Co-reporter:Daliao Tao, Chun Feng, Yinan Cui, Xian Yang, Ian Manners, Mitchell A. Winnik, and Xiaoyu Huang
Journal of the American Chemical Society May 31, 2017 Volume 139(Issue 21) pp:7136-7136
Publication Date(Web):May 17, 2017
DOI:10.1021/jacs.7b02208
We report the preparation of a series of fiber-like micelles of narrow length distribution with an oligo(p-phenylenevinylene) (OPV)-core and a poly(N-isopropylacrylamide) (PNIPAM) corona via two different crystallization-driven self-assembly (CDSA) strategies. The average length Ln of these micelles can be varied up to 870 nm by varying the temperature in self-seeding experiments. In addition, seeded growth was employed not only to prepare uniform micelles of controlled length, but also to form fiber-like A-B-A triblock comicelles with an OPV-core.
Co-reporter:Jieshu Qian, Xiaoyu Li, David J. Lunn, Jessica Gwyther, Zachary M. Hudson, Emily Kynaston, Paul A. Rupar, Mitchell A. Winnik, and Ian Manners
Journal of the American Chemical Society March 19, 2014 Volume 136(Issue 11) pp:4121-4124
Publication Date(Web):March 19, 2014
DOI:10.1021/ja500661k
Monodisperse fiber-like micelles with a crystalline π-conjugated polythiophene core with lengths up to ca. 700 nm were successfully prepared from the diblock copolymer poly(3-hexylthiophene)-block-polystyrene using a one-dimensional self-seeding technique. Addition of a polythiophene block copolymer with a different corona-forming block to the resulting nanofibers led to the formation of segmented B-A-B triblock co-micelles by crystallization-driven seeded growth. The key to these advances appears to be the formation of a relatively defect-free crystalline micelle core under the self-seeding conditions.
Co-reporter:Yijie Lu, Amanda J. Boyle, Ping-Jiang Cao, David Hedley, Raymond M. Reilly, and Mitchell A. Winnik
ACS Biomaterials Science & Engineering March 13, 2017 Volume 3(Issue 3) pp:279-279
Publication Date(Web):February 4, 2017
DOI:10.1021/acsbiomaterials.6b00649
In this study, we developed a new generation of metal chelating polymer (MCP) reagents that carry multiple polyethylene glycol (PEG) pendant groups to provide stealth to MCP-based radioimmunoconjugates (RICs). We describe the MCP synthesis for covalent attachment to panitumumab F(ab′)2 fragments (pmabF(ab′)2) in which different numbers of pendant methoxy-PEG chains [M = 2000, ∼45 ethylene glycol (EG) repeat units, referred to as PEG2K] are incorporated into the polymer backbone. The pendant PEG2K chains were designed to provide a protein-repellant corona so that metal chelators attached closer to the polymer backbone will be less apparent to the physiological environment. DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) groups to chelate 64Cu were installed on these conjugates to be employed for PET imaging. The conjugation of MCPs to pmabF(ab′)2 was based on a UV quantifiable bis-aromatic hydrazone formation under mild conditions (pH 5–6) between an aromatic aldehyde introduced on ε-NH2 groups of lysines in the F(ab′)2 fragments and a hydrazinonicotinamide (HyNic) group installed on the initiating end of the MCP. Three MCPs with 17 polyglutamide (PGlu) repeat units, DOTA chelators and with an average of 2, 4, and 8 pendant PEG2K chains were studied to examine their in vitro and in vivo characteristics, as well as their potential for PET/CT imaging. A pmabF(ab′)2-MCP conjugate carrying 2 PEG2K and one carrying 8 PEG2K pendant chains in the polymer were selected for microPET/CT imaging and biodistribution studies in tumor-bearing mice. Orthotopic pancreatic patient-derived xenografts tumors were visualized by PET/CT imaging. These RICs showed low levels of liver and spleen uptake along with even lower levels of kidney uptake. These encouraging results confirm the stealth properties of the MCPs with pendant PEG2K chains.Keywords: antibody- polymer conjugate; metal-chelating polymer; pancreatic cancer; panitumumab;
Co-reporter:Jothirmayanantham Pichaandi, Lemuel Tong, Alexandre Bouzekri, Qing Yu, Olga Ornatsky, Vladimir Baranov, and Mitchell A. Winnik
Chemistry of Materials June 13, 2017 Volume 29(Issue 11) pp:4980-4980
Publication Date(Web):June 5, 2017
DOI:10.1021/acs.chemmater.7b01339
We are interested in developing lanthanide nanoparticles (NPs) as high sensitivity tagging reagents for antibodies to analyze cells by mass cytometry (MC). Two key prerequisites for this application are that the NPs have to be colloidally stable in phosphate-containing buffers and the free NPs must have very low levels of nonspecific binding to cells. These are the issues we address here. We describe the synthesis of 30 nm diameter NaYF4:Yb,Er nanoparticles, their transfer to aqueous solution via citrate exchange, and their encapsulation in liposomes to minimize their interaction with live cells. The lipid coating consisted of a 2:2:1 mol ratio mixture of dioleoylphosphatidyl choline (DOPC), egg sphingomyelin (ESM), and ovine cholesterol (Chol), referred to as DEC221. Since encapsulating 30 nm NPs in liposomes is an unprecedented challenge, we added varying amounts of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxyPEG-2000] (mPEG2K-DSPE) to the lipid formulation, both to promote curvature of the lipid coating and to use the polyethylene glycol (PEG) chains to impart stealth and minimize interaction with cells. We succeeded in coating individual NPs with the lipid bilayer and showed that, after coating, the NPs were colloidally stable in PBS buffer for up to one month. We used MC to measure nonspecific binding of the lipid-coated NPs to three different suspension cell lines, Ramos, THP-1, and KG1a cells. For dosages of 50, 100, and 1000 NPs/cell, the measured signals were barely above background. For dosages of 10 000 and 30 000 NPs/cell, nonspecific binding levels were on the order of 10–15 NPs per cell, less than 0.1% of the applied dose. Dopant ions such as Yb also provide a measurable signal, indicating that NaYF4 NPs can serve as a useful host matrix for different lanthanide dopants for multiparameter experiments. These are very encouraging results for future experiments in which specific antibodies will be incorporated into the lipid coating.
Co-reporter:Elsa Lu, Jothirmayanantham Pichaandi, Loryn P. Arnett, Lemuel Tong, and Mitchell A. Winnik
The Journal of Physical Chemistry C August 24, 2017 Volume 121(Issue 33) pp:18178-18178
Publication Date(Web):August 16, 2017
DOI:10.1021/acs.jpcc.7b03783
While there have been many advances in techniques to synthesize uniform lanthanide-doped upconversion nanoparticles (UCNPs), it is still a challenge to synthesize small (ca. 5 nm) hexagonal phase UCNPs that are also bright. The most common method to obtain strongly emissive UCNPs is to synthesize core–shell structures with a passivating shell coating the luminescent core. This approach normally results in larger NPs (>20 nm) and requires two-step procedures. Here, we report a one-pot synthesis of 4 nm NaLuF4:Gd(37%),Yb(16%),Er(2%) UCNPs, whose colloidal solutions show upconversion luminescence (UCL) visible to the eye. We initially hypothesized that the origin of UCL from such small UCNPs was due to a Gd-rich hexagonal upconverting core containing Yb and Er with a Lu-rich passivating shell. This idea is based on the different nucleation rates of the NaLnF4 NPs. Interestingly, the 4 nm NaLuF4-based UCNPs are in the cubic phase, and subsequently undergo a phase transformation with prolonged heating to form larger (12–14 nm) uniform hexagonal phase UCNPs. We also found that if the molar ratio of Lu:Gd in the reaction mixture was decreased from 45:37 to 20:62, the resulting UCNPs still initially nucleated in the cubic phase. Additional studies in which we varied other reaction parameters (temperature, ratios of Na+/Ln3+ and F–/Ln3+, and solvent composition) also resulted in initial nucleation in the cubic phase. In contrast, both the NaGdF4:Yb,Er and NaYF4:Gd,Yb,Er UCNPs nucleated in the hexagonal phase. Our results suggest that the presence of Lu in the reaction mixture influences the nucleation of NaLnF4 NPs. Lanthanide compositions that would normally nucleate in the hexagonal phase appear to nucleate in the cubic phase when Lu is present.
Co-reporter:Maria Jose Gonzalez-Alvarez;Jan Paternoga;Katharina Breul;Hyungjun Cho;Mahtab Z. Roshandel;Mohsen Soleimani
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 19) pp:2931-2941
Publication Date(Web):2017/05/16
DOI:10.1039/C7PY00387K
Concern for the environment has been driving major changes in the coatings industry. To reduce the amount of volatile organic compounds (VOC's) released to the atmosphere; new technology and deeper understanding should be developed to replace solvent-based coatings with water-based coatings. Most of these coatings contain latex particles prepared by emulsion polymerization, referred to as primary dispersions. Secondary dispersions are polymer nanoparticles in water normally prepared by nanoprecipitation in water of pre-formed polymer dissolved in a water-miscible organic solvent, which is later removed. In this work we design a new approach to secondary dispersions involving direct emulsification of a solid carboxylated polymer prepared by a solvent-free process. We carry out experiments to understand the emulsification process including polymer exchange among nanoparticles as the dispersions in water are annealed. We used a low molecular weight acid-functional styrene-acrylic copolymer (nominal Mn 5000 g mol−1, Đ = 3). With this polymer, we prepared aqueous polymer dispersion through partial neutralization with ammonia and vigorous stirring in hot water, in the absence of any organic solvent or surfactant. We labelled samples of the polymer with donor and acceptor dyes, which enabled us to study mixing of polymer molecules by fluorescence resonance energy transfer (FRET) during emulsification and upon annealing the dispersions. Our goal with labelling the polymer is to investigate the dispersion process as the partially neutralized polymer is stirred and heated, and to understand aspects of the colloidal stability of the dispersion at ambient and elevated temperatures. These types of polymers have the potential to serve as the basis for environmentally friendly tough and robust thermoset paints and coatings.
Co-reporter:Sepehr Mastour Tehrani, Wanjuan Lin, Sabine Rosenfeldt, Gerald Guerin, Yijie Lu, Yi Liang, Markus Drechsler, Stephan Förster, and Mitchell A. Winnik
Chemistry of Materials 2016 Volume 28(Issue 2) pp:501
Publication Date(Web):January 6, 2016
DOI:10.1021/acs.chemmater.5b03295
We describe the room-temperature synthesis and characterization of needle-like lanthanide phosphate (LnPO4) nanocrystals in water, based on in situ precipitation of LnPO4 using functional aqueous microgels as a soft nanoreactor. The poly(NIPAm/VCL/MAA) microgels were prepared by the copolymerization of N-isopropylacrylamide, N-vinylcaprolactam, and methacrylic acid. Our goal was to prepare Ln-encoded microgels suitable for bead-based biological assays employing mass cytometry. The low solubility of nanocrystalline LnPO4 avoids the problem of Ln ion leakage from the microgels. The main challenge was to find appropriate conditions to confine the LnPO4 precipitate to the interior of the microgels. Various sources of phosphate ions led to precipitation of LnPO4 on the exterior of the microgels. One approach worked. It involved three steps: neutralization of the MAA groups in the microgels with NaOH, ion exchange with a lanthanide salt, followed by treatment with a large excess of PBS buffer at pH 7.4. In this way, we obtained microgels containing ca. 107 Ln atoms per microgel (Ln = La, Nd, Eu, Tb, Ho, Tm). The microgels were shown to be uniform in size by dynamic light scattering and transmission electron microscopy. The LnPO4-containing microgels showed much higher stability against leakage of metals to acidic buffers compared to the LnF3-containing microgels reported previously [Lin, W.; Langmuir 2011, 27, 7265]. Small-angle X-ray scattering measurements and selected area electron diffraction data showed striking differences in the internal structure of hybrid microgels containing TbPO4 from those containing TbF3. The TbF3-containing microgels had a core–shell structure with an amorphous TbF3 core, whereas the TbPO4 microgels contained needle-like nanocrystals (width ca. 2 nm, lengths on the order of 80 nm) distributed throughout the structure. These microgels are very promising materials for biological assays based on mass cytometry.
Co-reporter:Lemuel Tong
The Journal of Physical Chemistry C 2016 Volume 120(Issue 11) pp:6269-6280
Publication Date(Web):March 10, 2016
DOI:10.1021/acs.jpcc.6b00570
Over the past decade, there have been extensive developments in the field of lanthanide-based nanoparticles (NPs). Most studies have focused on the application of upconverting NaYF4-based NPs for deep tissue imaging and paramagnetic NaGdF4 NPs for MRI. Current applications for the remaining members of the lanthanide series are rather limited. Recently, a novel bioanalytical technique known as mass cytometry (MC) has been developed which can benefit from the entire lanthanide series of NPs. MC is a high-throughput multiparametric cell-by-cell analysis technique based on atomic mass spectrometry that uses antibodies labeled with metal isotopes for biomarker detection. NaLnF4 NPs offer the promise of high sensitivity coupled with multiparameter detection, provided that NPs can be synthesized with a narrow size distribution. Here we describe the synthesis of six members of this NP family (NaSmF4, NaEuF4, NaGdF4, NaTbF4, NaDyF4, NaHoF4) with the appropriate size (5–30 nm) and size distribution (CV < 5%) for MC. We employed the coprecipitation method developed by Li and Zhang [Nanotechnology 2008, 19, 345606], and for each member of this series, we examined the heating rate, final reaction temperature, and composition of the reaction mixture in an attempt to optimize the synthesis. For each of the six NaLnF4, in the range of the target sizes, we were able to identify “sweet spots” in the reaction conditions to obtain NPs with a narrow size distribution. In addition, we investigated the oleate surface coverage of the NPs and the effect of long-term storage (2 years) on the colloidal stability of the NPs. Finally, NaTbF4 NPs were rendered hydrophilic via lipid encapsulation and tested for nonspecific binding with KG1a and Ramos cells by mass cytometry.
Co-reporter:Simmyung Yook, Yijie Lu, Jenny Jooyoung Jeong, Zhongli Cai, Lemuel Tong, Ramina Alwarda, Jean-Philippe Pignol, Mitchell A. Winnik, and Raymond M. Reilly
Biomacromolecules 2016 Volume 17(Issue 4) pp:
Publication Date(Web):March 14, 2016
DOI:10.1021/acs.biomac.5b01642
We are studying a novel radiation nanomedicine approach to treatment of breast cancer using 30 nm gold nanoparticles (AuNP) modified with polyethylene glycol (PEG) metal-chelating polymers (MCP) that incorporate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelators for complexing the β-particle emitter, 177Lu. Our objective was to compare the stability of AuNP conjugated to MCP via a single thiol [DOTA-PEG-ortho-pyridyl disulfide (OPSS)], a dithiol [DOTA-PEG-lipoic acid (LA)] or multithiol end-group [PEG-pGlu(DOTA)8-LA4] and determine the elimination and biodistribution of these 177Lu-labeled MCP-AuNP in mice. Stability to aggregation in the presence of thiol-containing dithiothreitol (DTT), l-cysteine or glutathione was assessed and dissociation of 177Lu-MCP from AuNP in human plasma measured. Elimination of radioactivity from the body of athymic mice and excretion into the urine and feces was measured up to 168 h post-intravenous (i.v.) injection of 177Lu-MCP-AuNP and normal tissue uptake was determined. ICP-AES was used to quantify Au in the liver and spleen and these were compared to 177Lu. Our results showed that PEG-pGlu(DOTA)8-LA4-AuNP were more stable to aggregation in vitro than DOTA-PEG-LA-AuNP and both forms of AuNP were more stable to thiol challenge than DOTA-PEG-OPSS-AuNP. PEG-pGlu(177Lu-DOTA)8-LA4 was the most stable in plasma. Whole body elimination of 177Lu was most rapid for mice injected with 177Lu-DOTA-PEG-OPSS-AuNP. Urinary excretion accounted for >90% of eliminated 177Lu. All 177Lu-MCP-AuNP accumulated in the liver and spleen. Liver uptake was lowest for PEG-pGlu(177Lu-DOTA)8-LA4-AuNP but these AuNP exhibited the greatest spleen uptake. There were differences in Au and 177Lu in the liver for PEG-pGlu(177Lu-DOTA)8-LA4-AuNP. These differences were not correlated with in vitro stability of the 177Lu-MCP-AuNP. We conclude that conjugation of AuNP with PEG-pGlu(177Lu-DOTA)8-LA4 via a multithiol functional group provided the greatest stability in vitro and lowest liver uptake in vivo and is, therefore, the most promising for constructing 177Lu-MCP-AuNP for radiation treatment of breast cancer.
Co-reporter:Maria Jose Gonzalez-Alvarez, Lin Jia, Gerald Guerin, Kris Sanghyun Kim, Van An Du, Gilbert Walker, Ian Manners, and Mitchell A. Winnik
Macromolecules 2016 Volume 49(Issue 20) pp:7975-7984
Publication Date(Web):October 12, 2016
DOI:10.1021/acs.macromol.6b01616
In this study, we examine how the self-assembly of crystalline-coil block copolymers in solution can be influenced by small changes in the chemical structure of the corona-forming block. Three samples of poly(ferrocenyldimethylsilane)-block-poly(2-vinylpyridine) that form long fiber-like micelles uniform in width in 2-propanol, were treated with methyl iodide to convert a small fraction (0.1% to 6%) of the pyridines to methylpyridinium groups. When these partially quaternized samples (PFS-b-P2VPQ) were subjected to the same self-assembly protocol, very different structures were obtained. For PFS36-b-P2VP502Q, the presence of positive charges led to the formation of much shorter rod-like micelles. In contrast, for PFS17-b-P2VP170Q and PFS30-b-P2VP300Q, complex platelet structures were obtained. We explain the complexity of these structures in terms of a distribution of compositions, in which the polymer chains with the highest extent of methylation are the least soluble in 2-PrOH and the first to associate, leading to two-dimensional aggregates. The less quaternized polymer chains remaining in solution have a stronger tendency to form elongated fiber-like micelles that grow from the ends of the initially formed planar structures. In this way, we show that small extents of chemical modification of the corona forming chains can modify the self-assembly process and that simple one-pot protocols can lead to diverse hierarchical structures.
Co-reporter:Gerald Guerin, Paul Rupar, Gregory Molev, Ian Manners, Hiroshi Jinnai, and Mitchell A. Winnik
Macromolecules 2016 Volume 49(Issue 18) pp:7004-7014
Publication Date(Web):September 9, 2016
DOI:10.1021/acs.macromol.6b01487
The emergence of one-dimensional (1D) micelles obtained from the crystallization driven self-assembly (CDSA) in solution of crystalline-coil block copolymers has opened the door to the fabrication of a variety of sophisticated structures. While the development of these fascinating nanomaterials is blossoming, there is very little fundamental work dedicated to understanding the morphological evolution of these 1D micelles in solution. Here, using a combination of transmission electron microscopy, electron tomography, and static and dynamic light scattering, we studied the effect of annealing on a colloidal suspension of 1D micelle fragments formed by the self-assembly of a crystalline-coil poly(ferrocenyldimethylsilane)-block-poly(isoprene) (PFS-b-PI) block copolymer in decane, a solvent selective for PI. We are particularly interested in studying the evolution of the rectangular cross-section of the crystalline core of these micelle fragments. By electron tomography, we observed that the shorter dimension of the cross-section became even thinner upon annealing at elevated temperatures, while the longer dimension increased. In parallel, we observed an increase in packing density of the crystalline block as the fragments were annealed at temperatures above 60 °C. From these results, we concluded that annealing the micelle fragments induces a thinning of the crystalline core coupled with a lateral growth.
Co-reporter:Sepehr Mastour Tehrani, Yijie Lu, and Mitchell A. Winnik
Macromolecules 2016 Volume 49(Issue 22) pp:8711-8721
Publication Date(Web):November 9, 2016
DOI:10.1021/acs.macromol.6b01270
Thermoresponsive colloidal hydrogels (aqueous microgels) made from poly[oligo(ethylene glycol) methacrylate] (PEGMA) are an interesting class of biomaterials due to their sharp thermal transition and excellent biocompatibility. However, the inherent protein repellency of PEGMA has made the biofunctionalization of these microgels difficult and prevented them from reaching their full potential in applications such as a protein carrier. Here, we report the synthesis of thermoresponsive PEGMA microgels and the covalent attachment of horseradish peroxidase (HRP, as a model protein) to these microgels. We prepared our microgels by the precipitation copolymerization of 70 mol % OEGMA300 and 30 mol % methacrylic acid in water. The resulting microgels showed a volume phase transition temperature (VPTT) of ca. 60 °C in acidic buffers and in DI water but in neutral and basic buffers did not show a thermal response up to 75 °C. The direct immobilization of HRP to the activated carboxylic groups in the microgel backbone was unsuccessful, but using a diamine spacer with four ethylene glycol units, we were able to covalently attach this enzyme to our PEGMA microgels through bis-aryl hydrazone chemistry. HRP has its maximum activity at ca. 50 °C. At higher temperatures, the activity was reduced, but the microgel-bound enzyme showed less reduction in activity than the native enzyme and no change in activity associated with the VPTT. In addition, PEGMA microgels stabilized the attached enzymes against thermal denaturation. For example, our results showed that the enzyme immobilized on the PEGMA microgel lost its activity 3.4 times slower than the free enzyme in the first 5 h of annealing at 50 °C. The bioconjugation strategy introduced here could serve as a model for the covalent attachment of other biomacromolecules to the protein-repellent PEGMA microgels.
Co-reporter:Hang Zhou, Yijie Lu, Meng Zhang, Gerald Guerin, Ian Manners, and Mitchell A. Winnik
Macromolecules 2016 Volume 49(Issue 11) pp:4265-4276
Publication Date(Web):May 23, 2016
DOI:10.1021/acs.macromol.6b00544
Amphiphilic crystalline-coil diblock copolymers polyferrocenyldimethylsilane-block-poly(N-isopropylacrylamide) of two different block ratios (PFS56-b-PNIPAM190 and PFS26-b-PNIPAM520) were synthesized by a copper-catalyzed azide–alkyne coupling reaction. They exhibited pronounced differences in self-assembly in alcohol solvents. While PFS56-b-PNIPAM190 formed mixtures of spherical and rod-like micelles in ethanol and 2-propanol, PFS26-b-PNIPAM520 formed long fibers of uniform width in these solvents. We used a seeded growth protocol to grow rod-like PFS26-b-PNIPAM520 micelles of uniform lengths. There were two surprising features of this experiment: First, micelle growth was unusually slow and required a long aging time (40 days) for them to reach their final length. Second, the micelles were characterized by a low number of polymer chains per unit length as determined by multiangle light scattering. This result suggests a loose packing of PFS chains in the micelle core. In an attempt to prepare thermoresponsive nanofibrillar hydrogels from these micelles, we explored approaches to transfer them from 2-propanol to water. These attempts were accompanied by extensive fragmentation of the micelles. We believe the fragility of these micelles is related to the loosely packed nature of the PFS chains in the micelle core. Fragmentation may also be affected by the cononsolvency effect of 2-propanol-water mixtures on the PNIPAM corona of the micelles. We could show, however, that the micelle fragments in water retained their anticipated thermoresponsive behavior.
Co-reporter:Isaac Herrera and Mitchell A. Winnik
The Journal of Physical Chemistry B 2016 Volume 120(Issue 9) pp:2077-2086
Publication Date(Web):February 18, 2016
DOI:10.1021/acs.jpcb.5b09202
Isothermal titration calorimetry (ITC) is a technique to measure the stoichiometry and thermodynamics from binding experiments. Identifying an appropriate mathematical model to evaluate titration curves of receptors with multiple sites is challenging, particularly when the stoichiometry or binding mechanism is not available. In a recent theoretical study, we presented a differential binding model (DBM) to study calorimetry titrations independently of the interaction among the binding sites (Herrera, I.; Winnik, M. A. J. Phys. Chem. B 2013, 117, 8659–8672). Here, we build upon our DBM and show its practical application to evaluate calorimetry titrations of receptors with multiple sites independently of the titration direction. Specifically, we present a set of ordinary differential equations (ODEs) with the general form d[S]/dV that can be integrated numerically to calculate the equilibrium concentrations of free and bound species S at every injection step and, subsequently, to evaluate the volume-normalized heat signal (δQV = δq/dV) of direct and reverse calorimetry titrations. Additionally, we identify factors that influence the shape of the titration curve and can be used to optimize the initial concentrations of titrant and analyte. We demonstrate the flexibility of our updated DBM by applying these differentials and a global regression analysis to direct and reverse calorimetric titrations of gadolinium ions with multidentate ligands of increasing denticity, namely, diglycolic acid (DGA), citric acid (CIT), and nitrilotriacetic acid (NTA), and use statistical tests to validate the stoichiometries for the metal–ligand pairs studied.
Co-reporter:Yang Gao; Huibin Qiu; Hang Zhou; Xiaoyu Li; Robert Harniman; Mitchell A. Winnik;Ian Manners
Journal of the American Chemical Society 2015 Volume 137(Issue 6) pp:2203-2206
Publication Date(Web):January 21, 2015
DOI:10.1021/ja512968b
Light-responsive block copolymers have been prepared with a crystallizable core-forming poly(ferrocenyldimethylsilane) (PFS) block, a corona-forming segment of poly(2-vinylpyridine) (P2VP), and a photocleavable o-nitrobenzyl (ONB) junction. These PFS-ONB-P2VP materials form monodisperse cylindrical micelles by living crystallization-driven self-assembly in a selective solvent for P2VP. The P2VP coronas were readily removed by photocleavage at the ONB linker, leading to PFS cylinders with a residual percentage of corona chains dependent on the photoirradiation time. Addition of PFS block copolymer unimers to a solution of the cylinders with ca. 10% residual coronal chains led to the formation of branched rather than linear micelles. The synthetic utility of the PFS-ONB-P2VP materials was further demonstrated by the preparation of nearly monodisperse P2VP nanotubes of tunable length using a strategy that also involved corona cross-linking.
Co-reporter:Lemuel Tong, Elsa Lu, Jothirmayanantham Pichaandi, Pengpeng Cao, Mark Nitz, and Mitchell A. Winnik
Chemistry of Materials 2015 Volume 27(Issue 13) pp:4899
Publication Date(Web):July 2, 2015
DOI:10.1021/acs.chemmater.5b02190
There have been important advances in characterizing the surface coverage of ligands on colloidal inorganic nanoparticles (NPs), but our knowledge of ligand coverage on lanthanide NPs is much more limited. The as-synthesized NPs are often coated with hydrophobic ligands that need to be replaced with hydrophilic ligands such as poly(ethylene glycol) (PEG) for biomedical applications. The two challenges in terms of characterizing ligand coverage on NPs are first to show that different analytical methods give consistent results and second to show how the sample preparation protocol affects ligand density. Here, we report a quantitative study of the native oleate content of as-synthesized NaYF4 and NaTbF4 NPs, as well as the surface coverage after ligand exchange with three methoxyPEG-monophosphates with Mn = 750, 2000, and 5000 Da. For NaYF4, we obtained consistent results for both oleates and PEGs by three independent methods (TGA, 1H NMR, and ICP-AES). The oleate coverage was very sensitive to the sample isolation/purification protocol, with a high surface coverage (5.5 to 8 nm–2) for ethanol/hexane sedimentation/redispersion but only 2 nm–2 if THF was used in place of hexanes. The surface coverages PEG750 (∼1.1 nm–2), PEG2000 (∼1.7 nm–2), and PEG5000 (∼0.2 nm–2) suggest that corona repulsion limits the number of PEG5000 molecules that can graft to the surface. For NaTbF4 NPs, we compared the surface coverage of PEG2000-monophosphate with a PEG2000-tetraphosphonate ligand shown to provide enhanced colloidal stability in PBS buffer. We found the surprising result that the footprints of these ligands were comparable, suggesting that there was insufficient room for all four phosphonate groups of the tetradentate ligand to bind simultaneously to the NP surface.
Co-reporter:Ghislaine Ngo Ndjock Mbong; Yijie Lu; Conrad Chan; Zhongli Cai; Peng Liu; Amanda J. Boyle; Mitchell A. Winnik;Raymond M. Reilly
Molecular Pharmaceutics 2015 Volume 12(Issue 6) pp:1951-1960
Publication Date(Web):April 28, 2015
DOI:10.1021/mp5007618
Our objective was to evaluate the cytotoxicity toward HER2-positive human breast cancer (BC) cells of trastuzumab modified site−specifically with a metal-chelating polymer (MCP) that presents multiple DTPA chelators for complexing 111In. 111In emits subcellular range Auger electrons that induce multiple lethal DNA double-strand breaks (DSBs) in cells. MCPs were synthesized with a polyglutamide backbone with 24 or 29 pendant DTPA groups, with or without nuclear translocation sequence (NLS) peptide modification and a terminal hydrazide group for reaction with aldehydes generated by sodium periodate (NaIO4)-oxidation of glycans on the Fc-domain of trastuzumab. Trastuzumab was site-specifically modified with two DTPA and labeled with 111In for comparison (trastuzumab-NH-Bn-DTPA-111In). The maximum specific activity (SA) for labeling trastuzumab-Hy-MCP with 111In was 90-fold greater than for trastuzumab-NH-Bn-DTPA-111In [8.9 MBq/μg (1.5 × 106 MBq/μmol) vs 0.1 MBq/μg (1.2 × 104 MBq/μmol)]. Trastuzumab-Hy-MCP-111In was bound, internalized, and imported into the nucleus of SK-BR-3 cells. NLS peptide modification of MCPs did not increase nuclear importation. A greater density of DNA DSBs was found for BC cells exposed to high SA (5.5 MBq/μg) than low SA (0.37 MBq/μg) radioimmunoconjugates. At 20 nmol/L, high SA trastuzumab-Hy-MCP-111In was 6-fold more effective at reducing the clonogenic survival (CS) of HER2 overexpressed and HER2 gene-amplified SK-BR-3 cells (1.3 × 106 receptors/cell) than low SA MCP-radioimmunoconjugates (CS = 1.8 ± 1.3 vs 10.9 ± 0.7%; P = 0.001). Low SA trastuzumab-NH-Bn-DTPA-111In (20 nmol/L) reduced the CS of SK-BR-3 cells to 15.8 ± 2.1%. The CS of ZR-75-1 cells with intermediate HER2 density (4 × 105 receptors/cell) but without HER2 gene amplification was reduced to 20.5 ± 4.3% by high SA trastuzumab-Hy-MCP-111In (20 nmol/L). The CS of HER2-overexpressed (5 × 105 HER2/cell) but trastuzumab-resistant TrR1 cells was decreased to 17.1 ± 1.6% by high SA trastuzumab-Hy-MCP-111In. Unlabeled trastuzumab (20 nmol/L) was 18-fold less potent than high SA trastuzumab-Hy-MCP-111In at reducing the CS of SK-BR-3 cells (CS = 37.0 ± 5.3%) and 3-fold less effective against Zr-75-1 cells (CS = 53.1 ± 9.8%). Unlabeled trastuzumab had no effect on the survival of TrR1 cells. We conclude that increasing the SA for labeling with 111In by site-specific conjugation of MCPs to trastuzumab greatly amplified the cytotoxic potency against HER2-overexpressed and gene-amplified BC cells and extended its cytotoxicity to cells with intermediate HER2 expression but without gene amplification and to cells that are HER2 overexpressed but trastuzumab-resistant.
Co-reporter:Emily L. Kynaston;Oliver E. C. Gould;Jessica Gwyther;George R. Whittell;Ian Manners
Macromolecular Chemistry and Physics 2015 Volume 216( Issue 6) pp:685-695
Publication Date(Web):
DOI:10.1002/macp.201400541
The crystallization-driven self-assembly (CDSA) of crystalline-coil polyselenophene diblock copolymers represents a facile approach to nanofibers with distinct optoelectronic properties relative to those of their polythiophene analogs. The synthesis of an asymmetric diblock copolymer with a crystallizable, π-conjugated poly(3-heptylselenophene) (P3C7Se) block and an amorphous polystyrene (PS) coblock is described. CDSA was performed in solvents selective for the PS block. Based on transmission electron microscopy (TEM) analysis, P3C7Se18-b-PS125 formed very long (up to 5 μm), highly aggregated nanofibers in n-butyl acetate (nBuOAc) whereas shorter (ca. 500 nm) micelles of low polydispersity were obtained in cyclohexane. The micelle core widths in both solvents determined from TEM analysis (≈ 8 nm) were commensurate with fully-extended P3C7Se18 chains (estimated length = 7.1 nm). Atomic force microscopy (AFM) analysis provided characterization of the micelle cross-section including the PS corona (overall micelle width ≈ 60 nm). The crystallinity of the micelle cores was probed by UV–vis and photoluminescence (PL) spectroscopy and wide-angle X-ray scattering (WAXS).
Co-reporter:Zachary M. Hudson;Ian Manners;Huibin Qiu
Science 2015 Volume 347(Issue 6228) pp:
Publication Date(Web):
DOI:10.1126/science.1261816
Cylindrical polymer micelles pack in 3D
When you control chemistry, solvents, temperature, and concentration, surfactants and block copolymers will readily assemble into micelles, rods, and other structures. Qiu et al. take this to new lengths through precise selection of longer polymer blocks that self-assemble through a crystallization process (see the Perspective by Lee et al.). They chose polymer blocks that were either hydrophobic or polar and used miscible solvents that were each ideal for only one of the blocks. Their triblock comicelles generated a wide variety of stable three-dimensional superstructures through side-by-side stacking and end-to-end intermicellar association.
Science, this issue p. 1329; see also p. 1310
Co-reporter:Graeme Cambridge, M. Jose Gonzalez-Alvarez, Gerald Guerin, Ian Manners, and Mitchell A. Winnik
Macromolecules 2015 Volume 48(Issue 3) pp:707-716
Publication Date(Web):January 21, 2015
DOI:10.1021/ma502279b
The self-assembly of block copolymers in solution leads to micellar structures with various morphologies. One way to modify the morphology of these micelles is to blend the block copolymer with a homopolymer corresponding to the core-forming block. Although the self-assembly of blends of amorphous homopolymers and block polymers has been extensively studied, there are few examples of solution self-assembly of blends of a core-crystalline block copolymer with a semicrystalline homopolymer. Here we describe a systematic study of the assembly in decane of blends of a polyferrocenylsilane-block-polyisoprene sample (PFS48-b-PI264) with two different PFS homopolymer samples (PFS50 and PFS20). We examine the structures formed as a function of blend composition and compare them to the structures formed from the individual components. PFS48-b-PI264 itself forms long cylindrical micelles, while the two homopolymer samples form stacks of lamellar crystals. Self-assembly of block copolymer mixtures leads to structures with an elongated planar core and fiber-like protrusions from the ends. The details of the structure vary in an interesting and systematic way as the ratio of homopolymer/block copolymer is increased, with important differences seen for the PFS50 and PFS20 homopolymer samples. This study demonstrates that cocrystallization plays a crucial role in determining the structures formed from these mixtures.
Co-reporter:Hang Zhou, Yijie Lu, Huibin Qiu, Gerald Guerin, Ian Manners, and Mitchell A. Winnik
Macromolecules 2015 Volume 48(Issue 7) pp:2254-2262
Publication Date(Web):April 6, 2015
DOI:10.1021/acs.macromol.5b00238
A polyferrocenyldimethylsilane-block-poly(2-vinylpyridine) sample with a photocleavable o-nitrobenzyl ester (ONB) group at the junction (PFS35-hv-P2VP400) was synthesized by copper-catalyzed coupling of a P2VP-ONB-alkyne with a PFS-azide. Rodlike core-crystalline micelles of uniform length and uniform width were prepared in 2-propanol, a selective solvent for P2VP. Samples of these micelles were photoirradiated with UV-A light (peak emission 360 nm), which induced cleavage at the core–corona junction. Prolonged irradiation (24 h) led to aggregation and precipitation of the corona-cleaved micelles. One could see by TEM that the width of the micelles in the aggregates was significantly reduced (from 49 to 21 nm) because of the loss of the P2VP block, while the PFS core length (L) remained unchanged. For one micelle sample with Lw = 320 nm (650 polymer molecules per micelle), the time course of the irradiation was monitored by GPC, TEM, and multiangle light scattering. After 1 h irradiation, 60% of the corona chains were cleaved, but only small amounts of aggregates had formed. Most of the rodlike micelles maintained their colloidal stability even after 70% of the corona chains had been cleaved. By GPC, we detected formation of an unexpected PFS dimer that became more prominent as the irradiation continued. Dimer formation could be explained by a photoredox coupling of o-nitrosobenzaldehyde groups at the ends of adjacent PFS chains embedded in the micelle core.
Co-reporter:Peng Liu, Amanda J. Boyle, Yijie Lu, Jarrett Adams, Yuechuan Chi, Raymond M. Reilly, and Mitchell A. Winnik
Biomacromolecules 2015 Volume 16(Issue 11) pp:
Publication Date(Web):October 15, 2015
DOI:10.1021/acs.biomac.5b01066
Metal-chelating polymers (MCPs) can amplify the radioactivity delivered to cancer cells by monoclonal antibodies or their Fab fragments. We focus on trastuzumab (tmAb), which is used to target cancer cells that overexpress human epidermal growth factor receptor 2 (HER2). We report the synthesis and characterization of a biotin (Bi) end-capped MCP, Bi-PAm(DET-DTPA)36, a polyacrylamide with diethylenetriaminepentaacetic acid (DTPA) groups attached as monoamides to the polymer backbone by diethylenetriamine (DET) pendant groups. We compared its behavior in vivo and in vitro to a similar MCP with ethylenediamine (EDA) pendant groups (Bi-PAm(EDA-DTPA)40). These polymers were complexed to a streptavidin-modified Fab fragment of tmAb, then labeled with 111In to specifically deliver multiple copies of 111In to HER2+ cancer cells. Upon decay, 111In emits γ-rays that can be used in single-photon emission computed tomography radioimaging, as well as Auger electrons that cause lethal double strand breakage of DNA. Our previous studies in Balb/c mice showed that radioimmunoconjugates (RICs) containing the Bi-PAm(EDA-DTPA)40 polymer had extremely short blood circulation time and high liver uptake and were, thus, unsuitable for in vivo studies. The polymer Bi-PAm(EDA-DTPA)40 carries negative charges on each pendant group at neutral pH and a net charge of (−1) on each pendant group when saturated with stable In3+. To test our hypothesis that charge associated with the polymer repeat unit is a key factor affecting its biodistribution profile, we examined the biodistribution of RICs containing Bi-PAm(DET-DTPA)36. While this polymer is also negatively charged at neutral pH, it becomes a zwitterionic MCP upon saturation of the DTPA groups with stable In3+ ions. In both nontumor bearing Balb/c mice and athymic mice implanted with HER2+ SKOV-3 human ovarian cancer tumors, we show that the zwitterionic MCP has improved biodistribution, higher blood levels of radioactivity, lower levels of normal tissue uptake, and higher tumor uptake. Surface plasmon resonance experiments employing the extracellular domain of HER2 show that the MCP immunoconjugates retain high affinity antigen recognition, with dissociation constants in the low nM range. In vitro studies with SKOV-3 cells for both MCP immunoconjugates show a combination of specific binding that can be completed in the presence of excess tmAb IgG and nonspecific binding (NSB) that persists in the presence of tmAb IgG. We conclude that zwitterionic MCPs represent a much better choice than polymers with charges along the backbone for in vivo delivery of RICs to HER2+ cancer cells.
Co-reporter:Jianbo Tan, Guangyao Zhao, Zhaohua Zeng, and Mitchell A. Winnik
Macromolecules 2015 Volume 48(Issue 11) pp:3629-3640
Publication Date(Web):May 22, 2015
DOI:10.1021/acs.macromol.5b00688
Functional poly(methyl methacrylate) (PMMA) microbeads with a very narrow size distribution were synthesized by photoinitiated RAFT dispersion polymerization in aqueous ethanol using an acrylic acid–oligo(ethylene glycol) copolymer as a macro-RAFT agent. These particles are a prototype for multiparameter bead-based assays employing mass cytometry, a technique in which metal-encoded beads are injected into the plasma torch of an inductively coupled plasma mass spectrometer (ICP-MS), and the metal ions generated are detected by time-of-flight mass spectrometry. To label the beads, the polymerization reaction was carried out in the presence of various types of small (ca. 5 nm) lanthanide fluoride (LnF3) nanoparticles (e.g., LaF3, CeF3, and TbF3) with polymerizable methacrylate groups on their surface. The type of metal ion and the metal content of the PMMA microbeads could be varied by changing the composition of the reaction medium. An important feature of these microbeads is that acrylic acid groups in the corona are available for covalent attachment of biomolecules. As a proof of concept, FITC–streptavidin (FITC-SAv) was covalently coupled to the surface of a Ln-encoded microbead sample. The number of FITC-SAv binding sites on the beads was determined through three parallel assays involving biotin derivatives. Interaction of the beads with a biotin–tetramethylrhodamine derivative was monitored by fluorescence, whereas interaction of the beads with a biotin-DOTA-Lu derivative was monitored both by ICP-MS and by mass cytometry. Each measurement detected an average of ca. 5 × 104 biotins per microsphere. Control experiments with beads covalently labeled with FITC–bovine serum albumin (FITC-BSA) showed only very low levels of nonspecific binding.
Co-reporter:Sepehr Mastour Tehrani, Yijie Lu, Gerald Guerin, Mohsen Soleimani, Dmitry Pichugin, and Mitchell A. Winnik
Biomacromolecules 2015 Volume 16(Issue 10) pp:
Publication Date(Web):September 3, 2015
DOI:10.1021/acs.biomac.5b00768
Immobilization of enzymes on solid supports has been widely used to improve enzyme recycling, enzyme stability, and performance. We are interested in using aqueous microgels (colloidal hydrogels) as carriers for enzymes used in high-temperature reactions. These microgels should maintain their volume and colloidal stability in aqueous media up to 100 °C to serve as thermo-stable supports for enzymes. For this purpose, we prepared poly(N-hydroxyethyl acrylamide) (PHEAA) microgels via a two-step synthesis. First, we used precipitation polymerization in water to synthesize colloidal poly(diethylene glycol-ethyl ether acrylate) (PDEGAC) particles as a precursor. PDEGAC forms solvent swollen microgels in organic solvents such as methanol and dioxane and in water at temperatures below 15 °C. In the second step, these PDEGAC particles were transformed to PHEAA microgels through aminolysis in dioxane with ethanolamine and a small amount of ethylenediamine. Dynamic laser scattering studies confirmed that the colloidal stability of microgels was maintained during the aminolysis in dioxane and subsequent transfer to water. Characterization of the PHEAA microgels indicated about 9 mol % of primary amino groups. These provide functionality for bioconjugation. As proof-of-concept experiments, we attached the enzyme horseradish peroxidase (HRP) to these aqueous microgels through (i) N-(3-(dimethylamino)propyl)-N′-ethylcarbodiimide hydrochloride (EDC) coupling to the carboxylated microgels or (ii) bis-aryl hydrazone (BAH) coupling to microgels functionalized with 6-hydrazinonicotinate acetone (PHEAA-HyNic). Our results showed that HRP maintained its catalytic activity after covalent attachment (87% for EDC coupling, 96% for BAH coupling). The microgel enhanced the stability of the enzyme to thermal denaturation. For example, the residual activity of the microgel-supported enzyme was 76% after 330 min of annealing at 50 °C, compared to only 20% for the free enzyme under these conditions. PHEAA microgels in water show great promise as hosts for enzymatic reaction, especially at elevated temperatures.
Co-reporter:Lin Jia, Amy Petretic, Gregory Molev, Gerald Guerin, Ian Manners, and Mitchell A. Winnik
ACS Nano 2015 Volume 9(Issue 11) pp:10673
Publication Date(Web):September 29, 2015
DOI:10.1021/acsnano.5b01176
Multistep crystallization-driven self-assembly has great potential to enable the construction of sophisticated hybrid mesostructures. During the assembly procedure, each step modifies the properties of the overall structure. Here, we demonstrate the flexibility and efficiency of this approach by preparing polymer–carbon nanotube (CNT) hybrid mesostructures. We started by growing polyferrocenyldimethylsilane (PFS) homopolymer crystals onto multiwalled CNTs. This first step facilitated the redispersion of the coated CNTs in both polar (2-propanol) and nonpolar (decane) solvents. In the second step of hybrid construction, a unimer solution of a PFS block copolymer was added into the PFS-CNT solution. The PFS coating on the CNT initiated the growth of elongated micelles, resulting in structures that resembled hairy caterpillars. PFS-b-P2VP (P2VP = poly-2-vinylpyridine) micelles were grown from the surface of PFS-CNT hybrids in 2-propanol, and PFS-b-PI (PI = polyisoprene) micelles were grown from these hybrids in decane. These micelles, by transmission electron microscopy were seen to have an unusual wavy kinked structure, very different from the uniform smooth structures normally formed by both block copolymers. For hybrids with PFS-b-PI micelles, cross-linking of the micelle coronas locked the whole structure in place and allowed us to use the partial oxidation of PFS components to grow metal nanoparticles in the core of these micelles. We finally investigated the influence of the corona-forming block used to grow the micelles on the wettability of films made from these mesostructures. Films formed with CNT hybrids grafted with PFS-b-PI micelles were superhydrophobic (contact angle, 152°). In contrast, the surface of the films was much more hydrophilic (contact angle, 54°) when they were prepared from CNT hybrids grafted with PFS-b-P2VP micelles.Keywords: carbon nanotube; crystallization-driven self-assembly; hierarchy; hybrid mesostructures; surface modification;
Co-reporter:John R. Finnegan ; David J. Lunn ; Oliver E. C. Gould ; Zachary M. Hudson ; George R. Whittell ; Mitchell A. Winnik ;Ian Manners
Journal of the American Chemical Society 2014 Volume 136(Issue 39) pp:13835-13844
Publication Date(Web):September 22, 2014
DOI:10.1021/ja507121h
Block copolymers (BCPs) with a short crystallizable poly(ferrocenyldimethylsilane) (PFS) core-forming block self-assemble in selective solvents to afford cylindrical micelles, the ends of which are active to further growth via a process termed living crystallization-driven self-assembly (CDSA). We now report studies of the CDSA of a series of crystalline-brush BCPs with C6 (BCP6), C12 (BCP12), and C18 (BCP18) n-alkyl branches that were prepared by the thiol–ene functionalization of PFS-b-PMVS (PMVS = poly(methylvinylsiloxane)). Although the increased n-alkyl brush length of BCP12 and BCP18 hindered micelle growth, the increased intercoronal chain repulsion could be alleviated by their coassembly with linear PFS-b-PMVS. When the coassembly was initiated by short cylindrical seed micelles, monodisperse block comicelles of controllable length with “patchy” coronal nanodomains were accessible. TEM and AFM analysis of micelles prepared from BCP18 and PFS-b-PMVS were found to provide complementary characterization in that the OsO4-stained PMVS coronal domains were observed by TEM, whereas the brush block domains of BCP18 (which displayed greater height) were detected by tapping mode AFM. The results showed that the coassembly afforded a gradient structure, with an initial bias for the growth of the linear BCP over that of the more sterically demanding brush BCP, which was gradually reversed as the linear material was consumed. This represents the first example of living gradient CDSA, a process reminiscent of a living covalent gradient copolymerization of two different monomers. Although other possible explanations exist, simulations based on a statistical model indicated that the coronal nanodomains detected likely result from a segmented, gradient comicelle architecture that arises as a consequence of: (i) different rates of addition of BCP unimer to the micelle termini, and (ii) a cumulative effect resulting from steric hindrance associated with the brush block.
Co-reporter:Lin Jia ; Lemuel Tong ; Yi Liang ; Amy Petretic ; Gerald Guerin ; Ian Manners
Journal of the American Chemical Society 2014 Volume 136(Issue 47) pp:16676-16682
Publication Date(Web):November 18, 2014
DOI:10.1021/ja510019s
Immobilizing uniform nanostructures on a mesoscale substrate is a promising approach to prepare nanometer to micrometer sized materials with new functionalities. The hierarchical structures formed depend on both the nature of the substrate and the components deposited. In this paper, we describe the use of colloidal polystyrene microbeads as a sacrificial template to create a nanofibrous network coating consisting of elongated block copolymer micelles. This network has a secondary structure very different from that of conformal coatings obtained by other methods. In addition, the fibers of the network could be elongated by crystallization-driven self-assembly. The network was locked in place by cross-linking the micelles through in situ generation of small Pt nanoparticles. Subsequent removal of the sacrificial template gave an open vesicular structure. To demonstrate further transformation of the membrane, we showed that the cross-linked micelles could also be used to embed silver nanoparticles. The sacrificial template contained known amounts of Tb and Tm ions, allowing us to estimate via atomic mass spectrometry that 85% of the template surface was covered with micelle seeds. This approach to fabricating hierarchical coating structures expands the generality and scope of template-assisted synthesis to build advanced hierarchical materials with precise morphological control.
Co-reporter:Chun Feng, M. Jose Gonzalez-Alvarez, Yin Song, Isaac Li, Guangyao Zhao, Gregory Molev, Gerald Guerin, Gilbert Walker, Gregory D. Scholes, Ian Manners and Mitchell A. Winnik
Soft Matter 2014 vol. 10(Issue 44) pp:8875-8887
Publication Date(Web):29 Aug 2014
DOI:10.1039/C4SM01402B
We describe the synthesis and characterization of a family of diblock copolymers with 5 units of a dihexyloxy-phenylenevinylene block (OHPV) connected to a series of poly(ethylene glycol) (PEG) chains of different average lengths (12, 45 and 115 PEG units: OHPV5-b-PEG12, OHPV5-b-PEG45, OHPV5-b-PEG115). All three polymers underwent self-assembly in ethanol, a good solvent for the PEG units, but poor for the OHPV segment. The nature of the structures formed depends sensitively on the length of the PEG block. OHPV5-b-PEG115 formed long fiber-like micelles of uniform width, whereas OHPV5-b-PEG45 formed fragile broad ribbons. We also obtained thin ribbons with OHPV5-b-PEG12 but they tend to fold and twist upon themselves. The structures obtained were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM), as well as by wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC). In addition, their photophysical properties were examined by UV-vis, steady state fluorescence and fluorescence decay measurements. The results of these experiments indicate that the OHPV groups pack differently in the fiber-like micelles of OHPV5-b-PEG115 than in the lamellar structures formed by OHPV5-b-PEG45.
Co-reporter:Wanjuan Lin, Yi Hou, Yijie Lu, Ahmed I. Abdelrahman, Pengpeng Cao, Guangyao Zhao, Lemuel Tong, Jieshu Qian, Vladimir Baranov, Mark Nitz, and Mitchell A. Winnik
Langmuir 2014 Volume 30(Issue 11) pp:3142-3153
Publication Date(Web):2017-2-22
DOI:10.1021/la403627p
This paper addresses the question of whether one can use lanthanide nanoparticles (e.g., NaHoF4) to detect surface biomarkers expressed at low levels by mass cytometry. To avoid many of the complications of experiments on live or fixed cells, we carried out proof-of-concept experiments using aqueous microgels with a diameter on the order of 700 nm as a proxy for cells. These microgels were used to test whether nanoparticle (NP) reagents would allow the detection of as few as 100 proteins per “cell” in cell-by-cell assays. Streptavidin (SAv), which served as the model biomarker, was attached to the microgel in two different ways. Covalent coupling to surface carboxyls of the microgel led to large numbers (>104) of proteins per microgel, whereas biotinylation of the microgel followed by exposure to SAv led to much smaller numbers of SAv per microgel. Using mass cytometry, we compared two biotin-containing reagents, which recognized and bound to the SAvs on the microgel. One was a metal chelating polymer (MCP), a biotin end-capped polyaspartamide containing 50 Tb3+ ions per probe. The other was a biotinylated NaHoF4 NP containing 15 000 Ho atoms per probe. Nonspecific binding was determined with bovine serum albumin (BSA) conjugated microgels. The MCP was effective at detecting and quantifying SAvs on the microgel with covalently bound SAv (20 000 SAvs per microgel) but was unable to give a meaningful signal above that of the BSA-coated microgel for the samples with low levels of SAv. Here the NP reagent gave a signal 2 orders of magnitude stronger than that of the MCP and allowed detection of NPs ranging from 100 to 500 per microgel. Sensitivity was limited by the level of nonspecific adsorption. This proof of concept experiment demonstrates the enhanced sensitivity possible with NP reagents in cell-by-cell assays by mass cytometry.
Co-reporter:Gregory Molev, Yijie Lu, Kris Sanghyun Kim, Ingrid Chab Majdalani, Gerald Guerin, Srebri Petrov, Gilbert Walker, Ian Manners, and Mitchell A. Winnik
Macromolecules 2014 Volume 47(Issue 8) pp:2604-2615
Publication Date(Web):April 3, 2014
DOI:10.1021/ma402441y
This paper reports a new synthetic strategy for the preparation of polyferrocenylsilane (PFS) block copolymers (BCPs), by conjugation of two independently prepared homopolymers using Diels–Alder cycloaddition. The PFS blocks were synthesized by photocontrolled ring-opening polymerization, yielding polymers with a cyclopentadienyl end group that serves as a diene in the conjugation reaction. In this initial study we focused on the synthesis of organometallic–polypeptide block copolymers PFS-b-PBLG (PBLG = poly(γ-benzyl-l-glutamate) using PBLG polymers with a terminal maleimide attached by one-step postpolymerization modification. Five PFS-b-PBLG copolymers with different degrees of polymerization were synthesized and purified by a series of selective precipitations. The self-assembly of these samples was studied in N,N-dimethylformamide, a solvent selective for PBLG. The BCPs with a PFS block longer than the PBLG block after annealing at 90 °C formed highly uniform platelet micelles with a truncated elliptical shape. Experiments at 75 °C showed that disordered elongated structures formed initially, with fiber-like protrusions from the ends. Over time, the structures became shorter and wider, evolving into uniform truncated elliptical micelles. The process was monitored by X-ray diffraction (XRD) measurements and by 1H NMR spectroscopy. AFM analysis showed that the micelles were flat and that their thickness increased with the overall chain length of the BCP. Self-assembly of these BCPs in the presence of PFS homopolymer led to formation of flower-like mesostructures consisting of stacks of lamellar petals.
Co-reporter:Guangyao Zhao, Lemuel Tong, Pengpeng Cao, Mark Nitz, and Mitchell A. Winnik
Langmuir 2014 Volume 30(Issue 23) pp:6980-6989
Publication Date(Web):2017-2-22
DOI:10.1021/la501142v
Developing surface coatings for NaLnF4 nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH2-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF4 and NaTbF4 nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH2-PAMAM-4P ligand on oleate-capped NaLnF4 NPs. The NPs were first treated with methoxy-poly(ethylene glycol)-monophosphoric acid (Mn = 750) in tetrahydrofuran. The mPEG750-OPO3-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH2-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (Mn = 2000) and biotin-terminated PEG (Mn = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF4 and NaTbF4 NPs capped with mPEG2000–PAMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF4 NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously ( Langmuir 2012, 28, 12861−12870) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline.
Co-reporter:Ming-Siao Hsiao, Siti Fairus M. Yusoff, Mitchell A. Winnik, and Ian Manners
Macromolecules 2014 Volume 47(Issue 7) pp:2361-2372
Publication Date(Web):March 21, 2014
DOI:10.1021/ma402429d
Three well-defined asymmetric crystalline-coil poly(ferrocenyldimethylsilane-block-2-vinylpyridine) (PFS-b-P2VP) diblock copolymers (PFS44-b-P2VP264, PFS75-b-P2VP454, and PFS102-b-P2VP625) with similar block ratios (r = NP2VP/NPFS = ca. 6.0 ± 0.1) but different overall molar masses (Mn = 38 700, 65 800, and 90 400 g mol–1) were synthesized by sequential anionic polymerization, and their solution self-assembly behavior was explored as a function of (i) molar mass and (ii) the ratio of common to selective solvent. When self-assembly was performed in isopropanol (i-PrOH), a selective solvent for P2VP, a decrease in the rate of the crystallization-driven transition from the initially formed spheres (with amorphous PFS cores) into cylinders (with crystalline cores) was detected with an increase in molecular weight. This trend can be explained by a decrease in the rate of crystallization for the PFS core-forming block as the chain length increased. In contrast, when a mixture of i-PrOH with increasing amounts of THF, a common solvent for both blocks, was used, spheres, cylinders, and also narrow lenticular platelets consisting of crystallized PFS lamellae sandwiched by two glassy coronal P2VP layers were formed from the same PFSx-b-P2VP6x sample. The most likely explanation involves the plasticization of the PFS core-forming block which facilitates crystallization, possibly complemented by contraction of the coils of the P2VP coronal block which otherwise limit of the lateral growth of the crystalline PFS core as THF is a poorer solvent for P2VP than i-PrOH. Selected area electron diffraction studies indicated that the PFS cores of the spherical micelles were amorphous but were consistent with those of the cylindrical micelles existing in a state approximating to that of a monoclinic PFS single crystal. In contrast, in the platelets formed in THF/i-PrOH, the PFS cores were found to be polycrystalline. The formation of narrow lenticular polycrystalline platelets rather than a regular, rectangular single crystalline morphology was attributed to a poisoning effect whereby the interference of the long P2VP coronal blocks in the growth of a rectangular PFS single crystalline core introduces defects at the crystal growth fronts.
Co-reporter:Jianbo Tan, Guangyao Zhao, Yijie Lu, Zhaohua Zeng, and Mitchell A. Winnik
Macromolecules 2014 Volume 47(Issue 19) pp:6856-6866
Publication Date(Web):September 19, 2014
DOI:10.1021/ma501432s
Macromonomers can serve as efficient and effective stabilizers for dispersion polymerization of monomers such as styrene and methyl methacrylate, but the size distributions of the polymer microparticles obtained tend to be broad. We are interested in functional microbeads which can be used for immunoassays, where the size distribution has to be very narrow. We report a photoinitiated RAFT dispersion polymerization of methyl methacrylate (MMA) in ethanol–water mixtures, with methoxy-poly(ethylene glycol) methacrylate (Mn = 2000 g/mol, EO45) as the reactive steric stabilizer. We identify reaction conditions where one can obtain PMMA microspheres with coefficient of variation in the particle diameter (CVd) less than 3%. Carboxy-functional PMMA microspheres were obtained by a two-stage (seeded) polymerization with methacrylic acid (MAA) added as a comonomer in the second stage. We show that the functional microspheres prepared in this way are effective substrates for the covalent attachment of proteins such as BSA and IgG immunoglobulins. In one set of experiments with a dye-labeled secondary antibody, we found that we could detect 104 IgGs per PMMA microbead.
Co-reporter:Adam Nunns, George R. Whittell, Mitchell A. Winnik, and Ian Manners
Macromolecules 2014 Volume 47(Issue 23) pp:8420-8428
Publication Date(Web):November 19, 2014
DOI:10.1021/ma501725h
A comparative study of the solution self-assembly behavior of two polystyrene-arm-polyisoprene-arm-polyferrocenylsilane (μ-SIF) miktoarm star terpolymers of similar composition has been conducted: one with a short, atactic, noncrystallizable poly(ferrocenylethylmethylsilane) (PFEMS) block (μ-SIFa) and one with a short, crystallizable poly(ferrocenyldimethylsilane) (PFDMS) block (μ-SIFc). Both solvent composition and the amorphous/crystallizable nature of the polyferrocenylsilane (PFS) block exhibited a profound influence on the morphologies of the micelles obtained. In hexane, the formation of uniform spherical micelles with an amorphous, phase-mixed PS/PFS core was observed for both μ-SIFa and μ-SIFc. The introduction of cyclohexane (a theta-solvent for PS at 34.5 °C) to give a 1:1 cyclohexane/hexane (v/v) solvent composition resulted in the formation of distorted spherical micelles with a core composed of phase-separated PS and PFS, for both μ-SIFa and μ-SIFc. Interestingly, the distorted spherical micelles formed from crystallizable μ-SIFc evolved with time into elongated fiber-like structures with a phase-separated PS and PFDMS core, while the noncrystallizable counterpart, μ-SIFa, remained as distorted spheres. It was found that in ethyl acetate, a good solvent for PI and PS, μ-SIFa remained unimeric in solution, whereas μ-SIFc formed cylindrical micelles composed of a crystalline PFDMS core and a phase-separated, patchy, PS and PI corona. Finally, seeded growth of μ-SIFc from short, cylindrical PFDMS-b-PDMS seeds (PDMS = polydimethylsiloxane) was demonstrated, yielding B–A–B block comicelles where outer segments derived from μ-SIFc blocks bore a strong resemblance to that ultimately formed under conditions of homogeneous nucleation.
Co-reporter:Gerald Guerin, Graeme Cambridge, Mohsen Soleimani, Sepehr Mastour Tehrani, Ian Manners, and Mitchell A. Winnik
The Journal of Physical Chemistry B 2014 Volume 118(Issue 36) pp:10740-10749
Publication Date(Web):August 29, 2014
DOI:10.1021/jp502806v
Scattering techniques (i.e., static light scattering, small angle neutron scattering,11 or small angle X-ray scattering) are excellent tools to study nanoscopic objects in solution. However, to interpret the experimental data, one needs to use the appropriate form factor. While recent progress has been made in the writing of form factors for complex structures, there is still a need to develop a method to evaluate the form factor of inhomogeneous elongated scatterers. Here, we propose an approach based on the principle of “Russian dolls”. Multiblock rods are represented as multi generations of rods (mother, daughter, granddaughter, etc.), where each rod is nested within the rod of the previous generation, like Russian dolls. A shift parameter is used to introduce asymmetry in the rod along its long axis. This approach not only allowed us to write the form factor of multiblock rods, but it also gave us the possibility to account for the polydispersity in length of each block and of the shift parameter. Finally, we applied these equations to the case of a series of solutions of triblock comicelles slightly polydisperse in length.
Co-reporter:Yijie Lu, Ghislaine Ngo Ndjock Mbong, Peng Liu, Conrad Chan, Zhongli Cai, Dirk Weinrich, Amanda J. Boyle, Raymond M. Reilly, and Mitchell A. Winnik
Biomacromolecules 2014 Volume 15(Issue 6) pp:
Publication Date(Web):May 16, 2014
DOI:10.1021/bm500174p
Three types of metal-chelating polymers (MCPs) with hydrazide end groups were synthesized. (1) The first set of polymers (the F-series) was synthesized with a furan end group, and all of the pendant groups along the chain carried only a diethylenetriaminepentaacetic acid (DTPA) metal-chelating functionality. The hydrazide was introduced via a Diels–Alder reaction between the furan and 3,3′-N-[ε-maleimidocaproic acid] hydrazide (EMCH). (2) The P-series polymers was designed to carry several copies of a nuclear-localization peptide sequence (NLS peptides, CGYGPKKKRKVGG, harboring the NLS from the simian virus 40 large T-antigen) in addition to the DTPA metal-chelating groups. (3) The third type of polymer (the P-Py series) was a variation of the P-series polymers but with the introduction of a small number of pyrene chromophores along the backbone to allow for UV measurement of the incorporation of the MCPs into trastuzumab (tmab). These hydrazide-terminated polymers were site-specifically conjugated to aldehyde groups generated by NaIO4 oxidation of the pendant glycan in the Fc domain of tmab. The immunoconjugates were radiolabeled with 111In and analyzed by SE–HPLC to confirm the attachment of the polymer to the antibody. HER2 binding assays demonstrated that neither the MCPs nor the presence of the NLS peptides interfered with specific antigen recognition on SK-Br-3 cells, although nonspecific binding was increased by polymer conjugation. Our results suggest that MCPs can be site-specifically attached to antibodies via oxidized glycans in the Fc domain and labeled with 111In to construct radioimmunoconjugates with preserved immunoreactivity.
Co-reporter:Peng Liu, Zhongli Cai, Jae W. Kang, Amanda J. Boyle, Jarret Adams, Yijie Lu, Ghislaine Ngo Ndjock Mbong, Sachdev Sidhu, Raymond M. Reilly, and Mitchell A. Winnik
Biomacromolecules 2014 Volume 15(Issue 3) pp:
Publication Date(Web):February 7, 2014
DOI:10.1021/bm401483a
We describe the synthesis of a heterotelechelic metal-chelating polymer (Bi-MCP-Dox), a polyacrylamide with a number average degree of polymerization DPn = 50 (PDI = 1.2), with biotin (Bi) and doxorubicin (Dox) as functional chain ends and diethylenetriaminepentaacetic acid (DTPA) pendant groups as the binding sites for metal ions. We compared its behavior in cell-uptake experiments with a similar polymer (Bi-MCP) without Dox. These MCPs were complexed with trastuzumab Fab (tmFab) fragments covalently linked to streptavidin (SAv) to form tmFab-SAv-Bi-MCP-Dox and tmFab-SAv-Bi-MCP via the strong affinity between Bi and SAv. tmFab targets human epidermal growth factor receptor-2 (HER2), which is overexpressed on certain human breast cancer cells. Surface plasmon resonance (SPR) experiments with the extracellular domain (ECD) of HER2 showed that incorporation of the MCPs in these complexes had no significant effect on the association or dissociation rate with the HER2 ECD and the dissociation constants. The tmFab-complexed MCPs were subsequently labeled with 111In (an Auger electron emitting radionuclide). Auger electrons can cause lethal DNA double strand breaks (DSBs) but only if they are emitted intracellularly and especially, in close proximity to the nucleus. To evaluate the cellular and nuclear uptake of tmFab-SAv-Bi-MCP-Dox, we incubated HER2+ SK-BR-3 human breast cancer cells with the complexes saturated with stable In3+ and visualized their distribution by confocal fluorescence microscopy, monitoring the fluorescence of Dox. In parallel, we carried out cell fractionation studies on tmFab-SAv-Bi-MCP-Dox and on tmFab-SAv-Bi-MCP labeled with 111In. Both radiolabeled complexes showed cell internalization and nuclear localization. We conclude that metal-chelating polymers with this composition appear to encourage internalization, nuclear uptake, and chromatin (DNA) binding of trastuzumab fragments modified with streptavidin in human breast cancer cells expressing HER2. Further study is needed to understand the impact of polymer charge on cellular uptake and distribution to intracellular compartments.
Co-reporter:Meng Zhang, Yiwei Hu, Yasser Hassan, Hang Zhou, Kimia Moozeh, Gregory D. Scholes and Mitchell A. Winnik
Soft Matter 2013 vol. 9(Issue 37) pp:8887-8896
Publication Date(Web):09 Aug 2013
DOI:10.1039/C3SM51668G
When 2-propanol is added to a chloroform solution containing a mixture of CdSe quantum dots (QDs) plus a polystyrene-block-poly(4-vinylpyridine) diblock copolymer (PS404-b-P4VP76, the subscripts refer to the degree of polymerization), the block copolymer assembles into uniform 40 nm diameter spherical micelles with a PS core and a thin P4VP corona to which the QDs are attached. As we reported in Macromolecules, 2010, 43, 5066–5074, vigorous magnetic stirring of this mixture over two days leads to a change in morphology to finite (1 to 2 μm) networks consisting of interconnected cylindrical PS struts surrounded by a P4VP corona in which the QDs are embedded. Here we find that these networks settle but do not lose their structure if allowed to age without stirring. Continued vigorous stirring over one month leads to a complete change in morphology, to form clusters of oval-shaped vesicles similar in size to the networks, in which individual vesicles are a few hundred nm long. Some of the vesicles appear to have popped open to form pairs of bowl-like structures. These bowls are single-walled structures, with walls similar in thickness (35 to 40 nm) to the core of the micelles formed in the initial step. We believe the walls consist of a PS core with P4VP chains protruding from the inner and out surfaces. The QDs are attached to both surfaces of both the vesicles and the bowls, presumably still embedded in the P4VP corona. These colloidal nanocomposites provide a striking example of kinetically controlled self-assembly in which the system evolves from small spheres of high curvature to cylinders of lower curvature, to larger vesicles, and each step takes place on its own characteristic time scale.
Co-reporter:Chun Feng, Vladimir I. Baranov and Mitchell A. Winnik
Journal of Analytical Atomic Spectrometry 2013 vol. 28(Issue 9) pp:1475-1484
Publication Date(Web):19 Jul 2013
DOI:10.1039/C3JA50149C
We describe the preparation of La, Tb-encoded-AuNP-coated PS microbeads via the combination of two-stage dispersion polymerization and post-functionalization of the particle surface. The introduction of La and Tb ions into the beads was achieved by the addition of LnCl3 and TbCl3 salts along with acrylic acid in the second the stage of dispersion polymerization. After the coating the surface of the beads with a silica layer containing methacrylate functional groups, a poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) layer was introduced by free radical polymerization. Subsequently, the PDMAEMA layer hosted the formation of gold nanoparticles on the surface of the beads. The formation of gold nanoparticles (AuNPs) on the surface of the beads was confirmed by dark-field transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX) and mass cytometry. Release experiments showed a negligible loss of Au ions or gold nanoparticles in 1.0% HCl aqueous solution over a two week period. The La, Tb-encoded-AuNP-coated PS beads were used to investigate the influence of plasma conditions on the thermolytic breakdown, diffusion, and matrix effects in the mass cytometer having two “thermometer” elements La (imbedded in the bulk of the bead) and Au (located on the bead surface). These experiments defined optimum conditions in terms of uniform ionization of the Au atoms present in the AuNPs. They also showed that neither the carbon-rich PS matrix nor the thin silica coating of the 1.6 μm diameter PS particles influenced the ability of the mass cytometer to determine La and Tb ion content quantitatively.
Co-reporter:Daniel Majonis, Olga Ornatsky, Dirk Weinrich, and Mitchell A. Winnik
Biomacromolecules 2013 Volume 14(Issue 5) pp:
Publication Date(Web):April 10, 2013
DOI:10.1021/bm4001662
We describe the synthesis and characterization of a family of poly(N-alkylacrylamide) polymers carrying 2–6 fluorescent dye molecules, ∼70 pendant DTPA (diethylenetriaminepentaacetic acid) groups, and an orthogonal maleimide end-group for covalent attachment to an antibody (Ab). These dual-purpose labels were designed for use in multiplexed immunoassays based on both mass cytometry and fluorescent flow cytometry. A challenge in the polymer synthesis was finding conditions for attaching a sufficient number of dye molecules to each polymer chain. Although attachment of a terminal maleimide to the polymers was not as efficient as anticipated, the end-functional polymers were still effective in labeling Abs. Secondary goat antimouse IgG was labeled with the four dual-label polymers as well as a control polymer, and while the resultant antibody-polymer conjugates showed positive performance in mass cytometric and fluorescent assays, some trials showed problems such as low signal and nonspecific adsorption. Four primary antibody conjugates were prepared and used to stain cells in 4-plex assays. The results of both primary assays are bittersweet in that the CD3-FITC and CD45-DyLight 649 conjugates performed well, while the CD13-DyLight 405 and the CD38-DyLight 549 conjugates did not.
Co-reporter:Dr. Nina McGrath;Dr. Avinash J. Patil;Dr. Scott M. D. Watson;Dr. Benjamin R. Horrocks;Dr. Charl F. J. Faul; Andrew Houlton; Mitchell A. Winnik; Stephen Mann; Ian Manners
Chemistry - A European Journal 2013 Volume 19( Issue 39) pp:13030-13039
Publication Date(Web):
DOI:10.1002/chem.201300589
Abstract
Stable colloidal dispersions of polyaniline (PAni) nanofibers with controlled lengths from about 200 nm–1.1 μm and narrow length distributions (Lw/Ln<1.04; Lw=weight average micelle length, Ln=number average micelle length) were prepared through the template-directed synthesis of PAni using monodisperse, solution-self-assembled, cylindrical, block copolymer micelles as nanoscale templates. These micelles were prepared through a crystallization-driven living self-assembly method from a poly(ferrocenyldimethylsilane)-b-poly(2-vinylpyridine) block copolymer (PFS25-b-P2VP425). This material was initially self-assembled in iPrOH to form cylindrical micelles with a crystalline PFS core and a P2VP corona and lengths of up to several micrometers. Sonication of this sample then yielded short cylinders with average lengths of 90 nm and a broad length distribution (Lw/Ln=1.32). Cylindrical micelles of PFS25-b-P2VP425 with controlled lengths and narrow length distributions (Lw/Ln<1.04) were subsequently prepared using thermal treatment at specific temperatures between 83.5 and 92.0 °C using a 1D self-seeding process. These samples were then employed in the template-directed synthesis of PAni nanofibers through a two-step procedure, where the micellar template was initially stabilised by deposition of an oligoaniline coating followed by addition of a polymeric acid dopant, resulting in PAni nanofibers in the emeraldine salt (ES) state. The ES–PAni nanofibers were shown to be conductive by scanning conductance microscopy, whereas the precursor PFS25-b-P2VP425 micelle templates were found to be dielectric in character.
Co-reporter:Isaac Herrera and Mitchell A. Winnik
The Journal of Physical Chemistry B 2013 Volume 117(Issue 29) pp:8659-8672
Publication Date(Web):July 10, 2013
DOI:10.1021/jp311812a
We present a set of model-independent differential equations to analyze isothermal titration calorimetry (ITC) experiments. In contrast with previous approaches that begin with specific assumptions about the number of binding sites and the interactions among them (e.g., sequential, independent, cooperative), our derivation makes more general assumptions, such that a receptor with multiple sites for one type of ligand species (homotropic binding) can be studied with the same analytical expression. Our approach is based on the binding polynomial formalism, and the resulting analytical expressions can be extended to account for any number of binding sites and any type of binding interaction among them. We refer to the set of model-independent differential equations to study ITC experiments as a differential binding model (DBM). To demonstrate the flexibility of our DBM, we present the analytical expressions to study receptors with one or two binding sites. The DBM for a receptor with one site is equivalent to the Wiseman isotherm but with a more intuitive representation that depends on the binding polynomial and the dimensionless parameter c = K·MT, where K is the binding constant and MT the total receptor concentration. In addition, we show how to constrain the general DBM for a receptor with two sites to represent sequential, independent, or cooperative binding interactions between the sites. We use the sequential binding model to study the binding interaction between Gd(III) and citrate anions. In addition, we simulate calorimetry titrations of receptors with positive, negative, and noncooperative interactions between the two binding sites. Finally, we derive a DBM for titrations of receptors with n-independent binding sites.
Co-reporter:Taunia L. L. Closson, Chun Feng, Adrienne Halupa, and Mitchell A. Winnik
Macromolecules 2013 Volume 46(Issue 7) pp:2523-2534
Publication Date(Web):March 18, 2013
DOI:10.1021/ma400079q
To obtain a better understanding of how lanthanide-encoded polystyrene microbeads are formed during their synthesis, we carried out kinetic studies of two-stage dispersion copolymerization of styrene and acrylic acid (AA, 2 wt % based on styrene), with or without added TmCl3, in ethanol in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) as a polymeric stabilizer. Particles of narrow size distribution and micrometer diameters were obtained, allowing us to compare rates of monomer conversion, Tm ion incorporation, and growth in particle size. In these reactions, AA or (AA + TmCl3) were added in a second stage (t = 1 h). Much of the AA incorporation into the particles occurred in the latter half of the reaction. In the presence of small amounts of TmCl3 there was some retardation of the polymerization reaction. The most striking result was that at the higher levels of TmCl3 most of the metal ion incorporation occurred late in the reaction.
Co-reporter:Amanda J. Boyle;Peng Liu;Yijie Lu;Dirk Weinrich
Pharmaceutical Research 2013 Volume 30( Issue 1) pp:104-116
Publication Date(Web):2013 January
DOI:10.1007/s11095-012-0853-y
To study the effects of backbone composition and charge of biotin-functionalized metal-chelating polymers (Bi-MCPs) for 111In complexed to streptavidin (SAv)-trastuzumab Fab fragments on tumor and normal tissue localization.Bi-MCPs were synthesized with a polyacrylamide [Bi-PAm(DTPA)40], polyaspartamide [Bi-PAsp(DTPA)33] or polyglutamide [Bi-PGlu(DTPA)28] backbone and harboured diethylenetriaminepentaacetic acid (DTPA) chelators for 111In. Bi-PAm(DTPA)40 had a net negative charge; Bi-PAsp(DTPA)33 and Bi-PGlu(DTPA)28 were zwitterionic with a net neutral charge. Binding to HER2+ SKOV-3 human ovarian carcinoma cells was determined. Tissue uptake was studied in Balb/c mice by MicroSPECT/CT imaging and biodistribution studies. Tumor and normal tissue uptake of 111In-labeled Bi-PAsp(DTPA)33 or Bi-PGlu(DTPA)28 complexed to SAv-Fab was evaluated 48 h post-injection in athymic mice with subcutaneous SKOV-3 xenografts.SAv-Fab complexed to MCPs bound specifically to SKOV-3 cells; but specific binding was decreased 2-fold. Liver uptake was 5–13 fold higher for Bi-PAm(DTPA)40 than Bi-PAsp(DTPA)33 and Bi-PGlu(DTPA)28 but was reduced by decreasing negative charges by saturation with indium. 111In-Bi-PAsp(DTPA)33 complexed to SAv-Fab accumulated in SKOV-3 tumors; low tumor uptake was found for 111In-Bi-PGlu(DTPA)28-SAv-Fab.Zwitterionic MCPs composed of polyaspartamide with a net neutral charge are most desirable for constructing radioimmunoconjugates.
Co-reporter:Dr. Jessica Gwyther; Joe B. Gilroy; Paul A. Rupar;David J. Lunn;Emily Kynaston; Sanjib K. Patra;Dr. George R. Whittell; Mitchell A. Winnik; Ian Manners
Chemistry - A European Journal 2013 Volume 19( Issue 28) pp:9186-9197
Publication Date(Web):
DOI:10.1002/chem.201300463
Abstract
With the aim of accessing colloidally stable, fiberlike, π-conjugated nanostructures of controlled length, we have studied the solution self-assembly of two asymmetric crystalline–coil, regioregular poly(3-hexylthiophene)-b-poly(2-vinylpyridine) (P3HT-b-P2VP) diblock copolymers, P3HT23-b-P2VP115 (block ratio=1:5) and P3HT44-b-P2VP115 (block ratio=ca. 1:3). The self-assembly studies were performed under a variety of solvent conditions that were selective for the P2VP block. The block copolymers were prepared by using Cu-catalyzed azide–alkyne cycloaddition reactions of azide-terminated P2VP and alkyne end-functionalized P3HT homopolymers. When the block copolymers were self-assembled in a solution of a 50 % (v/v) mixture of THF (a good solvent for both blocks) and an alcohol (a selective solvent for the P2VP block) by means of the slow evaporation of the common solvent; fiberlike micelles with a P3HT core and a P2VP corona were observed by transmission electron microscopy (TEM). The average lengths of the micelles were found to increase as the length of the hydrocarbon chain increased in the P2VP-selective alcoholic solvent (MeOH<iPrOH<nBuOH). Very long (>3 μm) fiberlike micelles were prepared by the dialysis of solutions of the block copolymers in THF against iPrOH. Furthermore the widths of the fibers were dependent on the degree of polymerization of the chain-extended P3HT blocks. The crystallinity and π-conjugated nature of the P3HT core in the fiberlike micelles was confirmed by a combination of UV/Vis spectroscopy, photoluminescence (PL) measurements, and wide-angle X-ray scattering (WAXS). Intense sonication (iPrOH, 1 h, 0 °C) of the fiberlike micelles formed by P3HT23-b-P2VP115 resulted in small (ca. 25 nm long) stublike fragments that were subsequently used as initiators in seeded growth experiments. Addition of P3HT23-b-P2VP115 unimers to the seeds allowed the preparation of fiberlike micelles with narrow length distributions (Lw/Ln <1.11) and lengths from about 100-300 nm, that were dependent on the unimer-to-seed micelle ratio.
Co-reporter:Meng Zhang, Paul A. Rupar, Chun Feng, Kaixiang Lin, David J. Lunn, Alex Oliver, Adam Nunns, George R. Whittell, Ian Manners, and Mitchell A. Winnik
Macromolecules 2013 Volume 46(Issue 4) pp:1296-1304
Publication Date(Web):February 7, 2013
DOI:10.1021/ma302054q
This paper reports a new synthetic strategy for the preparation of polyferrocenylsilane (PFS) block copolymers. The block copolymers were prepared by Cu-catalyzed alkyne/azide cycloaddition of two homopolymer precursors that allows access to new functional PFS block copolymers (e.g., polyferrocenylsilane-block-poly(N-isopropylacrylamide)) (PFS-b-PNIPAM)). Trimethylsilyl-protected, alkyne-terminated PFS homopolymer was first prepared via living anionic polymerization, terminating living PFS with commercially available 4-[(trimethylsilyl)ethynyl]benzaldehyde. Subsequent deprotection of the trimethylsilyl group with NaOMe yielded the ethynyl-terminated PFS (ω-alkyne-PFS). This method should be readily applicable to other polymers prepared by living anionic polymerization. Subsequently, non-PFS homopolymers containing a complementary “clickable” azide functional group were synthesized either by anionic polymerization, modification of a commercially available polymer, or atom transfer radical polymerization via two different approaches. In an azide postpolymerization modification approach, polystyrene (PS) and poly(methyl methacrylate) (PMMA) were functionalized by azide substitution of the terminal halide after ATRP. Alternatively, the azide moiety was incorporated into the ATRP initiator prior to polymerization, e.g., to give PNIPAM-N3 and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA-N3). Finally, the alkyne-terminated PFS segment and the azide functionalized counter block were coupled through the formation of a 1,2,3-triazole ring. In this report, PFS-b-PNIPAM, PFS-b-PDMAEMA, PFS-b-PS, PFS-b-PMMA, PFS-b-polydimethylsiloxane, and PFS-block-poly(ethylene oxide) have been synthesized via this convenient modular protocol in high yield and high purity.
Co-reporter:Jieshu Qian, Yijie Lu, Anselina Chia, Meng Zhang, Paul A. Rupar, Nikhil Gunari, Gilbert C. Walker, Graeme Cambridge, Feng He, Gerald Guerin, Ian Manners, and Mitchell A. Winnik
ACS Nano 2013 Volume 7(Issue 5) pp:3754
Publication Date(Web):April 15, 2013
DOI:10.1021/nn400124x
One-dimensional micelles formed by the self-assembly of crystalline-coil poly(ferrocenyldimethylsilane) (PFS) block copolymers exhibit self-seeding behavior when solutions of short micelle fragments are heated above a certain temperature and then cooled back to room temperature. In this process, a fraction of the fragments (the least crystalline fragments) dissolves at elevated temperature, but the dissolved polymer crystallizes onto the ends of the remaining seed fragments upon cooling. This process yields longer nanostructures (up to 1 μm) with uniform width (ca. 15 nm) and a narrow length distribution. In this paper, we describe a systematic investigation of factors that affect the self-seeding behavior of PFS block copolymer micelle fragments. For PI1000-PFS50 (the subscripts refer to the number average degree of polymerization) in decane, these factors include the presence of a good solvent (THF) for PFS and the effect of annealing the fragments prior to the self-seeding experiments. THF promoted the dissolution of the micelle fragments, while preannealing improved their stability. We also extended our experiments to other PFS block copolymers with different corona-forming blocks. These included PI637-PFS53 in decane, PFS60-PDMS660 in decane (PDMS = polydimethylsiloxane), and PFS30-P2VP300 in 2-propanol (P2VP = poly(2-vinylpyridine)). The most remarkable result of these experiments is our finding that the corona-forming chain plays an important role in affecting how the PFS chains crystallize in the core of the micelles and, subsequently, the range of temperatures over which the micelle fragments dissolve. Our results also show that self-seeding is a versatile approach to generate uniform PFS fiber-like nanostructures, and in principle, the method should be extendable to a wide variety of crystalline-coil block copolymers.Keywords: block copolymers; crystalline-coil; self-seeding
Co-reporter:Mark D. Whitmore, Jeffrey D. Vavasour, John G. Spiro, and Mitchell A. Winnik
Macromolecules 2013 Volume 46(Issue 22) pp:9045-9054
Publication Date(Web):November 11, 2013
DOI:10.1021/ma401862w
In recent years, there has been an explosion in the number of papers dealing with “cylindrical” PS-b-PMMA, for nanoscopic template or similar applications. This paper deals with two aspects of these systems. One is the detailed shape of the cores, i.e., the degree to which they are actually cylindrical in the hexagonal unit cell, as well as the nature of the core–corona interphase region. The second one relates to the use of fluorescence techniques to study these interphases, including whether or not one needs to consider energy transfer from one cylinder to neighboring ones. We approached these questions with numerical self-consistent field theory plus simulations of energy transfer based on them, and we examined two systems: one which mimics “typical” experimental systems at weak to moderate segregation, and one chosen to explore the limits of very weak segregation and polymer composition where the effects of interest could be maximal. In addition to providing basic information about the system characteristics, the results provide practical guidance on using the assumptions of cylindrical symmetry and no intercell energy transfer.
Co-reporter:Ludovico Cademartiri ; Gerald Guerin ; Kyle J. M. Bishop ; Mitchell A. Winnik ;Geoffrey A. Ozin
Journal of the American Chemical Society 2012 Volume 134(Issue 22) pp:9327-9334
Publication Date(Web):April 25, 2012
DOI:10.1021/ja301855z
One-dimensional inorganic crystals (i.e., crystalline nanowires) are one of the most intensely investigated classes of materials of the past two decades. Despite this intense effort, an important question has yet to be answered: do nanowires display some of the unique characteristics of polymers as their diameter is progressively decreased? This work addresses this question with three remarkable findings on the growth and form of ultrathin Bi2S3 nanowires. (i) Their crystallization in solution is quantitatively describable as a form of living step-growth polymerization: an apparently exclusive combination of addition of “monomer” to the ends of the nanowires and coupling of fully formed nanowires “end-to-end”, with negligible termination and initiation. (ii) The rate constants of these two main processes are comparable to those of analogous processes found in polymerization. (iii) The conformation of these nanowires is quantitatively described as a worm-like conformation analytically analogous to that of semiflexible polymers and characterized by a persistence length of 17.5 nm (shorter than that of double-stranded DNA) and contour lengths of hundreds of micrometers (longer than those of most synthetic polymers). These findings do not prove a chemical analogy between crystals and polymers (it is unclear if the monomer is a molecular entity tout court) but demonstrate a physical analogy between crystallization and polymerization. Specifically, they (i) show that the crystallization of ensembles of nanoscale inorganic crystals can be conceptually analogous to polymerization and can be described quantitatively with the same experimental and mathematical tools, (ii) demonstrate that one-dimensional nanocrystals can display topological characteristics of polymers (e.g., worm-like conformation in solution), (iii) establish a unique experimental model system for the investigation of polymer-like topological properties in inorganic crystals, and (iv) provide new heuristic guidelines for the synthesis of polymer-like nanowires.
Co-reporter:Yijie Lu, Mokit Chau, A. J. Boyle, Peng Liu, Ansgar Niehoff, Dirk Weinrich, Raymond M. Reilly, and Mitchell A. Winnik
Biomacromolecules 2012 Volume 13(Issue 5) pp:
Publication Date(Web):April 3, 2012
DOI:10.1021/bm2018239
We describe the synthesis of metal chelating polymers based on polyaspartamide and polyglutamide backbones as carriers for 111In in radioimmunoconjugates. These polymers [PAsp(DTPA), PGlu(DTPA)] have a biotin end group and diethylenetriaminepentaacetic acid (DTPA) chelators attached to the primary amines of the diethylenetriamine (DET) pendant groups of biotin-poly{N′-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} [PAsp(DET)] and of biotin-poly{N′-[N-(2-aminoethyl)-2-aminoethyl]glutamide} [PGlu(DET)]. Like Asn-containing proteins and polypeptides, polyaspartamides undergo uncatalyzed degradation under model physiological conditions (10 mM phosphate buffer, pH 7.4, 150 mM NaCl). We studied the uncatalyzed degradation of the polyaspartamide polymers by size exclusion chromatography and found that the degradation rate was sensitive to the nature of the pendant groups. The metal-free polymer underwent somewhat slower degradation than the corresponding polymers in which the DTPA groups were saturated with Eu3+ or In3+, but even after 14 days, substantial fractions of the polymers survived. We conclude that these polymers undergo negligible degradation on the time scale (24–48 h) of radioimmunotherapy treatment of tumors with 111In. From a mechanistic perspective, we note that these degradation rates are on the order of the deamidation rates reported [J. Peptide Res. 2004, 63, 426] for Asn-containing pentapeptides, with half-times on the order of 10 days, but much slower than the rapid decay (hours) reported recently [Biomaterials2010, 31, 3707] for poly{N′-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} itself. This variation in degradation rate can be explained in terms of the influence of positive charges on the pendant group enhancing the acidity of the side-chain amide nitrogen of the aspartamide repeat unit. The DET pendant group is positively charged at pH 7, but in indium-loaded PAsp(DTPA) this charge is offset by the net negative charge of the DTPA-In complex.
Co-reporter:Nicolas Illy, Daniel Majonis, Isaac Herrera, Olga Ornatsky, and Mitchell A. Winnik
Biomacromolecules 2012 Volume 13(Issue 8) pp:
Publication Date(Web):July 19, 2012
DOI:10.1021/bm300613x
Metal-chelating polymers (MCPs) are important reagents for multiplexed immunoassays based on mass cytometry. The role of the polymer is to carry multiple copies of individual metal isotopes, typically as lanthanide ions, and to provide a reactive functionality for convenient attachment to a monoclonal antibody (mAb). For this application, the optimum combination of chain length, backbone structure, end group, pendant groups, and synthesis strategy has yet to be determined. Here we describe the synthesis of a new type of MCP based on anionic ring-opening polymerization of an activated cyclopropane (the diallyl ester of 1,1-cyclopropane dicarboxylic acid) using a combination of 2-furanmethanethiol and a phosphazene base as the initiator. This reaction takes place with rigorous control over molecular weight, yielding a polymer with a narrow molecular weight distribution, reactive pendant groups for introducing a metal chelator, and a functional end group with orthogonal reactivity for attaching the polymer to the mAbs. Following the ring-opening polymerization, a two-step transformation introduced diethylenetriaminepentaacetic acid (DTPA) chelating groups on each pendant group. The polymers were characterized by NMR, size exclusion chromatography (SEC), and thermogravimetric analysis (TGA). The binding properties toward Gd3+ as a prototypical lanthanide (Ln) ion were also studied by isothermal titration calorimetry (ITC). Attachment to a mAb involves a Diels–Alder reaction of the terminal furan with a bismaleimide, followed by a Michael addition of a thiol on the mAb, generated by mild reduction of a disulfide bond in the hinge region. Polymer samples with a number average degree of polymerization of 35, with a binding capacity of 49.5 ± 6 Ln3+ ions per chain, were loaded with 10 different types of Ln ions and conjugated to 10 different mAbs. A suite of metal-tagged Abs was tested by mass cytometry in a 10-plex single cell analysis of human adult peripheral blood, allowing us to quantify the antibody binding capacity of 10 different cell surface antigens associated with specific cell types.
Co-reporter:Gerald Guerin, Fei Qi, Graeme Cambridge, Ian Manners, and Mitchell A. Winnik
The Journal of Physical Chemistry B 2012 Volume 116(Issue 14) pp:4328-4337
Publication Date(Web):March 26, 2012
DOI:10.1021/jp210454z
We describe simultaneous static (SLS) and dynamic light scattering (DLS) measurements on dilute solutions of a series of poly(ferrocenyldimethylsilane-b-isoprene) (PFS50–PI1000) block copolymer micelles of uniform length in tert-butyl acetate (tBA) and in decane. The subscripts in the term PFS50–PI1000 refer to the mean degree of polymerization of each block. The SLS experiments show that in both solvents the micelles formed are elongated and rigid. We also observed that the large length of the PI block (1000 units) contributes to the SLS signal. From the SLS data, we calculated the mass per unit length (linear aggregation number), as well as the cross section of the micelles in both solvents. Interestingly, the linear aggregation number and the micelle cross sections, as deduced by SLS, were the same in decane and in tBA. However, the fitting of DLS data indicates that the hydrodynamic cross section of the micelles in tBA is much larger than that in decane, and both values are larger than the values determined by SLS. We hypothesize that the difference between cross sections deduced from SLS and DLS data fitting is related to the shape of the segment density profile of the corona. In tBA, the PI chains are more stretched than in decane, increasing the hydrodynamic radius of the micelle cross section.
Co-reporter:John G. Spiro, Nicolas Illy, Mitchell A. Winnik, Jeffrey D. Vavasour, and Mark D. Whitmore
Macromolecules 2012 Volume 45(Issue 10) pp:4289-4294
Publication Date(Web):April 30, 2012
DOI:10.1021/ma202717p
The goal of this theoretical study was to examine whether formation of a lamellar superstructure was possible when blending relatively low-segregation cylindrical diblock copolymers (PS-b-PMMA) of complementary composition. In the past, these kinds of experiments had only been carried out at high segregation levels. Our numerical self-consistent field (NSCF) simulations provided details of the morphology of the superstructure as well as of the components to be blended. For comparison, we also report our NSCF simulation—giving the same details—of a corresponding experiment with PS–PB copolymers.
Co-reporter:Jieshu Qian, Yijie Lu, Graeme Cambridge, Gerald Guerin, Ian Manners, and Mitchell A. Winnik
Macromolecules 2012 Volume 45(Issue 20) pp:8363-8372
Publication Date(Web):October 10, 2012
DOI:10.1021/ma3014788
Two samples of rod-like micelles in decane were prepared by seeded growth from a sample of a poly(isoprene-b-ferrocenyldimethylsilane) diblock copolymer (PI1000–PFS50, where the subscripts indicate the degree of polymerization). These micelles were uniform in length with a mass/length of 1.9 molecules/nm. The longer micelles (L-1250) had a number-average length Ln = 1243 nm, whereas the shorter micelles (L-250) had Ln = 256 nm. We used transmission electron microscopy (TEM) to examine the behavior of these micelles when dilute solutions of L-1250 or L-250 or their mixtures were heated at temperatures ranging from 40 to 75 °C and then cooled to room temperature. At 55 °C, the L-1250 sample underwent kinetically controlled fragmentation to give a broad distribution of micelle lengths. At this temperature, fragmentation was much less prominent in the L-250 sample. At higher temperatures, micelles with narrow distributions of lengths were obtained in each case (Lw/Ln ≈ 1.01). This process operates under thermodynamic control, and Ln values increased strongly with an increase in temperature. These results indicate that the micelles fragment, and polymer molecules dissolve, as the samples were heated. The fraction of surviving fragments decreased significantly at elevated temperatures, presumably reflecting a distribution of crystallinity in the cores of the micelle precursor. When the solutions were cooled, the surviving fragments served as seeds for the epitaxial growth of the micelles as the polymer solubility decreased. The most striking result of these experiments was the finding that fragments formed from the L-1250 micelles had a distribution of dissolution temperatures shifted by about 5 °C to higher temperature than the shorter L-250 micelles.
Co-reporter:Mohsen Soleimani, Sheraz Khan, David Mendenhall, Willie Lau, Mitchell A. Winnik
Polymer 2012 Volume 53(Issue 13) pp:2652-2663
Publication Date(Web):7 June 2012
DOI:10.1016/j.polymer.2011.12.012
Co-reporter:Siti Fairus Mohd Yusoff, Ming-Siao Hsiao, Felix H. Schacher, Mitchell A. Winnik, and Ian Manners
Macromolecules 2012 Volume 45(Issue 9) pp:3883-3891
Publication Date(Web):April 26, 2012
DOI:10.1021/ma2027726
The influence of solvent composition on micelle morphology has been investigated for two crystalline-coil poly(ferrocenyldimethylsilane-block-2-vinylpyridine) (PFS-b-P2VP) diblock copolymers with different block ratios (5:1 and 1:1). The solution self-assembly of these materials was explored in solvent mixtures containing different ratios of a good solvent for both blocks (THF) and a selective solvent for the P2VP block (isopropanol). Various micellar morphologies such as spheres and platelets were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), dynamic light scattering (DLS), wide-angle X-ray scattering (WAXS), and atomic force microscopy (AFM). The results showed that the solution self-assembly of PFS-b-P2VP block copolymers (5:1, 1:1) gave spherical micelles with an amorphous PFS core at low THF content (10 vol %). Subsequently, the amorphous spheres were slowly transformed into platelet micelles with a lenticular shape that consisted of a crystalline PFS core sandwiched by two coronal P2VP layers. This indicated that the amorphous spherical micelles were in a metastable state. The transformation of spheres into platelets was significantly slower for the 5:1 block copolymer with the longer PFS core-forming segment presumably due to a lower rate of crystallization of the metalloblock. Platelets were found to be dominant for both block copolymers at higher THF content (THF ≥ 30 vol %). The formation of lenticular rather than regular platelets was attributed to a poisoning effect whereby interference of the P2VP corona-forming blocks in the growth of the crystalline PFS core leads to the creation of defects in the crystal growth fronts.
Co-reporter:Yi Liang, Ahmed I. Abdelrahman, Vladimir Baranov, Mitchell A. Winnik
Polymer 2012 Volume 53(Issue 4) pp:998-1004
Publication Date(Web):17 February 2012
DOI:10.1016/j.polymer.2011.12.031
This article describes a systematic study of ion release, carried out on lanthanide-encoded polystyrene-co-methacrylic acid (P(S-MAA)) and polystyrene-co-acrylic acid (P(S-AA)) copolymer particles, which were synthesized by two-stage or three-stage dispersion polymerizations. These particles with different levels of lanthanide (Ln) ion content and containing several different types of Ln ions were dispersed in normal buffer media, namely 2-(N-morpholino)ethanesulfonic acid (MES), phosphate buffered saline solution (PBS), ammonium acetate (AmAc) and buffers containing strong chelating molecules like ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA). Traditional inductively coupled plasma mass spectrometry (ICP-MS) was employed to follow the loss of ions into the aqueous medium as a function of time. The release behavior of the Ln ions were compared. In MES and PBS buffers at neutral pH, and AmAc at pH 9.0, there was essentially no significant loss of Ln ions from the particles to the buffer. When the chelating agents EDTA or DTPA were present in the buffer, the loss of Ln ions was more prominent, but less than 15% after 8 weeks under stirring. The differences among the different samples were small. Considering the ability of EDTA and DTPA to remove Ln ions from the particles and the fact of minimal ion release in the presence of PBS buffer, we infer that the ion loss is a more active process involving the EDTA or DTPA molecules. The main conclusion is that in the absence of strong chelating agents, these particles are stable against ion leakage, even upon prolonged storage and stirring. This is of great importance for their application in bead-array biological assays based on mass cytometry detection.
Co-reporter:Pengpeng Cao, Lemuel Tong, Yi Hou, Guangyao Zhao, Gerald Guerin, Mitchell A. Winnik, and Mark Nitz
Langmuir 2012 Volume 28(Issue 35) pp:12861-12870
Publication Date(Web):August 21, 2012
DOI:10.1021/la302690h
The range of properties available in the lanthanide series has inspired research into the use of lanthanide nanoparticles for numerous applications. We aim to use NaLnF4 nanoparticles for isotopic tags in mass cytometry. This application requires nanoparticles of narrow size distribution, diameters preferably less than 15 nm, and robust surface chemistry to avoid nonspecific interactions and to facilitate bioconjugation. Nanoparticles (NaHoF4, NaEuF4, NaGdF4, and NaTbF4) were synthesized with diameters from 9 to 11 nm with oleic acid surface stabilization. The surface ligands were replaced by a series of mono-, di-, and tetraphosphonate PEG ligands, whose synthesis is reported here. The colloidal stability of the resulting particles was monitored over a range of pH values and in phosphate containing solutions. All of the PEG-phosphonate ligands were found to produce non-aggregated colloidally stable suspensions of the nanoparticles in water as judged by DLS and TEM measurements. However, in more aggressive solutions, at high pH and in phosphate buffers, the mono- and diphosphonate PEG ligands did not stabilize the particles and aggregation as well as flocculation was observed. However, the tetraphosphonate ligand was able to stabilize the particles at high pH and in phosphate buffers for extended periods of time.
Co-reporter:Paul A. Rupar;Ian Manners;Laurent Chabanne
Science 2012 Volume 337(Issue 6094) pp:559-562
Publication Date(Web):03 Aug 2012
DOI:10.1126/science.1221206
Unidirectional Growth
Block copolymers, in which two dissimilar polymers are covalently joined together, can be designed to form micelles in solution and can be used as self-assembling injectable gels for tissue engineering or wound healing. One challenge is to find ways to create asymmetrical structures, because normally, block addition would occur at both ends of the polymer chain. Rupar et al. (p. 559; see the Perspective by Pochan) devised a route to link together three diblock copolymers with a capping approach. Protecting one end during growth gave rise to asymmetrical structures.
Co-reporter:Jean-Charles Eloi ; David A. Rider ; Graeme Cambridge ; George R. Whittell ; Mitchell A. Winnik ;Ian Manners
Journal of the American Chemical Society 2011 Volume 133(Issue 23) pp:8903-8913
Publication Date(Web):May 18, 2011
DOI:10.1021/ja1105656
In depth studies of the use of electron transfer reactions as a means to control the self-assembly of diblock copolymers with an electroactive metalloblock are reported. Specifically, the redox-triggered self-assembly of a series of polystyrene-block-polyferrocenylsilane (PS-b-PFS) diblock copolymers in dichloromethane solution is described. In the case of the amorphous polystyrenen-b-poly(ferrocenylphenylmethylsilane)m diblock copolymers (PSn-b-PFMPSm: n = 548, m = 73; n = 71, m = 165; where n and m are the number-averaged degrees of polymerization), spherical micelles with an oxidized PFS core and a PS corona were formed upon oxidation of more than 50% of the ferrocenyl units by [N(C6H4Br-4)3][SbX6] (X = Cl, F). Analogous block copolymers containing a poly(ferrocenylethylmethylsilane) (PFEMS) metalloblock, which has a lower glass transition temperature, behaved similarly. However, in contrast, on replacement of the amorphous metallopolymer blocks by semicrystalline poly(ferrocenyldimethylsilane) (PFDMS) segments, a change in the observed morphology was detected with the formation of ribbon-like micelles upon oxidation of PS535-b-PFDMS103 above the same threshold value. Again the coronas consisted of fully solvated PS and the core consisted of partially to fully oxidized PFS associated with the counteranions. When oxidation was performed with [N(C6H4Br-4)3][SbF6], reduction of the cores of the spherical or ribbon-like micelles with [Co(η-C5Me5)2] enabled full recovery of the neutral chains and no significant chain scission was detected.
Co-reporter:Feng He ; Torben Gädt ; Ian Manners
Journal of the American Chemical Society 2011 Volume 133(Issue 23) pp:9095-9103
Publication Date(Web):May 20, 2011
DOI:10.1021/ja202662u
We describe the self-assembly in 2-propanol (2-PrOH) of the triblock copolymer, poly(ferrocenyldimethylsilane-b-2-vinylpyridine-b-2,5-di(2′-ethylhexyloxy)-1,4-phenylvinylene) (PFS30-b-P2VP300-b-PDEHPV13, the subscripts refer to the degree of polymerization). The intense fluorescence of the PDEHPV moieties rendered the resulting cylindrical micelles and their aggregates visible in solution by laser confocal fluorescence microscopy (LCFM). Sonication yielded micelle fragments that could be grown into elongated fiber-like micelles 10 nm in width and nearly monodisperse in length by adding additional block polymer as a solution in tetrahydrofuran. The presence of the conjugated block in the corona promoted slow aggregation of the micelles into hierarchical flower-like structures, but this secondary assembly could be reversed by warming the solution to 50 °C for 30 min. When a solution of 500 nm long micelles of PFS30-b-P2VP300-b-PDEHPV13 in 2-PrOH was treated sequentially with controlled amounts of the diblock copolymer PFS30-b-P2VP300, and in intervals of 24 h, with additional aliquots of PFS30-b-P2VP300-b-PDEHPV13, PFS30-b-P2VP30, and PFS30-b-P2VP300-b- PDEHPV13, uniform rod-like multiblock co-micelles were obtained with remarkable optical properties: a banded light-emitting “barcode” structure with fluorescent segments of the triblock copolymer separated by nonemissive segments made up of the diblock copolymer.
Co-reporter:Joe B. Gilroy ; Paul A. Rupar ; George R. Whittell ; Laurent Chabanne ; Nicholas J. Terrill ; Mitchell A. Winnik ; Ian Manners ;Robert M. Richardson
Journal of the American Chemical Society 2011 Volume 133(Issue 42) pp:17056-17062
Publication Date(Web):September 1, 2011
DOI:10.1021/ja207417z
The self-assembly of block copolymers in selective solvents represents a powerful approach to functional core–shell nanoparticles. Crystallization of the core can play a critical role in directing self-assembly toward desirable, nonspherical morphologies with low mean interfacial curvature. Moreover, epitaxial growth processes have been implicated in recent advances that permit access to monodisperse cylinders, cylindrical block comicelles with segmented cores and/or coronas, and complex hierarchical architectures. However, how the core-forming block crystallizes in an inherently curved nanoscopic environment has not been resolved. Herein we report the results of synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) studies of well-defined, monodisperse crystalline-coil polyisoprene-block-polyferrocenylsilane cylindrical micelles aligned in an electric field. WAXS studies of the aligned cylinders have provided key structural information on the nature of the PFS micelle core together with insight into the role of polymer crystallinity in the self-assembly of these and potentially related crystalline-coil block copolymers.
Co-reporter:Mohsen Soleimani ; Jeffrey C. Haley ; Daniel Majonis ; Gerald Guerin ; Willie Lau
Journal of the American Chemical Society 2011 Volume 133(Issue 29) pp:11299-11307
Publication Date(Web):June 29, 2011
DOI:10.1021/ja203080p
We describe the synthesis, characterization, and film-forming properties of two-component nanoparticles that undergo a reversible morphology transformation in water as a function of pH. The particles consist of a high molecular weight acrylate copolymer and an acid-rich oligomer designed to be miscible with the polymer when its −COOH groups are protonated. Attaching a fluorescence resonance energy transfer (FRET) pair to components inside the nanoparticles enabled us to assess morphology at the molecular level. By inspecting changes in the donor fluorescence decay profile at different pH values, we established miscibility of the components in acidic solution but with charge-induced phase separation when the oligomers were neutralized to their carboxylate form. Complementary titration experiments revealed that the nanoparticles adopt a core–shell structure when the acid groups are deprotonated. We studied the effect of the acid-rich oligomer on the diffusion rate of the high molecular weight polymers following film formation. Our results show that the carboxylated oligomer enhanced the rate of diffusive mixing between high molecular weight molecules by more than 2 orders of magnitude. FRET measurements carried out on partially dried films using a low-resolution microscope showed that the carboxylate oligomer shell can delay coalescence for ca. 30 min after passage of the drying front. This delay is expected to help with increasing the ‘open time’ of latex paints, a desirable property of solvent-based paints that remains difficult to achieve with (environmentally compliant) waterborne paints. Use of ammonia as a volatile base resulted in synergistic effects: initial retardation of coalescence followed by acceleration of diffusive mixing as the ammonium salts dissociated and ammonia evaporated from the film.
Co-reporter:Sanjib K. Patra ; Rumman Ahmed ; George R. Whittell ; David J. Lunn ; Emma L. Dunphy ; Mitchell A. Winnik ;Ian Manners
Journal of the American Chemical Society 2011 Volume 133(Issue 23) pp:8842-8845
Publication Date(Web):May 11, 2011
DOI:10.1021/ja202408w
Solution self-assembly of the regioregular polythiophene-based block copolymer poly(3-hexylthiophene)-b-poly(dimethylsiloxane) yields cylindrical micelles with a crystalline P3HT core. Monodisperse nanocylinders of controlled length have been prepared via crystallization-driven self-assembly using seed micelles as initiators.
Co-reporter:Paul A. Rupar ; Graeme Cambridge ; Mitchell A. Winnik ;Ian Manners
Journal of the American Chemical Society 2011 Volume 133(Issue 42) pp:16947-16957
Publication Date(Web):October 3, 2011
DOI:10.1021/ja206370k
Previous work has established that polyisoprene (PI) coronas in cylindrical block copolymer micelles with a poly(ferrocenyldimethylsilane) (PFS) core can be irreversibly cross-linked by hydrosilylation using (HSiMe2)2O in the presence of Karstedt’s catalyst. We now show that treatment of cylindrical PI-b-PFS micelles with Karstedt’s catalyst alone, in the absence of any silanes, leads to PI coronal cross-linking through Pt(0)–olefin coordination. The cross-linking can be reversed through the addition of 2-bis(diphenylphosphino)ethane (dppe), a strong bidentate ligand, which removes the platinum from the PI to form Pt(dppe)2. The Pt(0) cross-linking of PI was studied with self-assembled cylindrical PI-b-PFS block copolymer micelles, where the cross-linking was found to dramatically increase the stability of the micellar structures. The Pt(0)–alkene coordination-induced cross-linking can be used to provide transmission electron microscopy contrast between PI and poly(dimethylsiloxane) (PDMS) corona domains in block comicelles as the process selectively increases the electron density of the PI regions. Moreover, following the assembly of a hierarchical scarf-shaped comicelle consisting of a PFS-b-PDMS platelet template with PI-b-PFS tassels, Pt(0)-induced cross-linking of the PI coronal regions allowed for the selective removal of the PFS-b-PDMS center, leaving behind an unprecedented hollowed-out scarf structure. The addition of Karstedt’s catalyst to PI or polybutadiene homopolymer toluene/xylene solutions resulted in the formation of polymer gels which underwent de-gelation upon the addition of dppe.
Co-reporter:Meng Zhang, Laetitia Rene-Boisneuf, Yiwei Hu, Kimia Moozeh, Yasser Hassan, Gregory Scholes and Mitchell A. Winnik
Journal of Materials Chemistry A 2011 vol. 21(Issue 26) pp:9692-9701
Publication Date(Web):31 May 2011
DOI:10.1039/C1JM11104C
Poly(styrene-b-4-vinylpyridine) diblock copolymers PS404-b-P4VP76 and PS317-b-P4VP76 (the subscripts indicate the degree of polymerization) self-assemble into spherical “crew-cut” micelles with a PS core and P4VP corona when prepared in a mixture of chloroform and 2-propanol. When the micelles are formed in the presence of quantum dots (QDs), the nature of the structures formed depends upon the polymer and the type of QDs. In our previous report [Macromolecules, 2010, 43, 5066–5074], PS404-b-P4VP76 + CdSe QDs formed stable spherical hybrid micelles, but prolonged vigorous stirring of the solutions led to a rearrangement into wormlike networks and loss of photoluminescence (PL) from the QDs. Here we report that PS317-b-P4VP76 + CdSe/ZnS core–shell QDs behave differently. Partial loss of PL intensity occurred upon addition of 2-propanol to the chloroform solution of the components, and the rearrangement to a network structure occurred spontaneously. We describe two strategies for recovery of the PL intensity for the QDs within the network, photo-activation and chemical activation with elemental sulfur.
Co-reporter:Ahmed I. Abdelrahman, Stuart C. Thickett, Yi Liang, Olga Ornatsky, Vladimir Baranov, and Mitchell A. Winnik
Macromolecules 2011 Volume 44(Issue 12) pp:4801-4813
Publication Date(Web):May 20, 2011
DOI:10.1021/ma200582q
Lanthanide-encoded polystyrene particles synthesized by dispersion polymerization are excellent candidates for mass cytometry based immunoassays; however, they have previously lacked the ability to conjugate biomolecules to the particle surface. We present here three approaches to postfunctionalize these particles, enabling the covalent attachment of proteins. Our first approach used partially hydrolyzed poly(N-vinylpyrrolidone) as a dispersion polymerization stabilizer to synthesize particles with high concentration of −COOH groups on the particle surface. In an alternative strategy to provide −COOH functionality to the lanthanide-encoded particles, we employed seeded emulsion polymerization to graft poly(methacrylic acid) (PMAA) chains onto the surface of these particles. However, these two approaches gave little to no improvement in the extent of bioconjugation. In our third approach, seeded emulsion polymerization was subsequently used as a method to grow a functional polymer shell (in this case, poly(glycidyl methacrylate) (PGMA)) onto the surface of these particles, which proved highly successful. The epoxide-rich PGMA shell permitted extensive surface bioconjugation of NeutrAvidin, as probed by an Lu-labeled biotin reporter (ca. 7 × 105 binding events per particle with a very low amount of nonspecific binding) and analyzed by mass cytometry. It was shown that coupling agents such as EDC were not needed, such was the reactivity of the particle surface. These particles were stable, and the addition of a polymeric shell did not affect the narrow lanthanide ion distribution within the particle interior as analyzed by mass cytometry. These particles represent the most promising candidates for the development of a highly multiplexed bioassay based on lanthanide-labeled particles to date.
Co-reporter:Fei Qi, Gerald Guerin, Graeme Cambridge, Wenguo Xu, Ian Manners, and Mitchell A. Winnik
Macromolecules 2011 Volume 44(Issue 15) pp:6136-6144
Publication Date(Web):July 14, 2011
DOI:10.1021/ma2008223
Many poly(ferrocenyldimethylsilane) (PFS) block copolymers form fiber-like micelles with a semicrystalline core in selective solvents. Solvent effects on micelle formation are not well understood. This paper compares micelle formation for a sample of PFS50–PI1000 (the subscripts refer to the number-average degrees of polymerization) in decane with that in tert-butyl acetate (tBA), a more polar solvent. When micelle formation is seeded, by adding block copolymer as a concentrated solution in tetrahydrofuran to solutions of micelle fragments, micelle growth was similar in both solvents. Micelles with a narrow length distribution were formed and the length increased in proportion to the amount of polymer added. In contrast, when micelles were prepared by heating a sample of the block copolymer in decane or tBA to 90 °C and allowing the solution to cool, pronounced differences were observed. In decane, micelles with a uniform width (10 nm) and a length on the order of 5 μm formed after 1 h, and grew to about 10 μm after 5 days. In tBA, aliquots taken from solution 1 h after cooling appeared to undergo microphase separation only upon solvent evaporation. Ribbon-like structures were observed after 1 and 5 days aging, but these evolved into fiber-like structures with a uniform 10 nm width and lengths greater than 30 μm after 25 days. These differences observed in the rate of micelle formation likely reflect differences in the nucleation stage of micelle formation. tBA is a better solvent for the PFS block than decane. As a consequence, it appears to take much longer for semicrystalline micelle nuclei to form in tBA. The seeded growth experiments demonstrate that once seed micelles are present, growth occurs similarly in both solvents.
Co-reporter:Jieshu Qian;Dr. Gerald Guerin;Yijie Lu;Graeme Cambridge; Ian Manners; Mitchell A. Winnik
Angewandte Chemie International Edition 2011 Volume 50( Issue 7) pp:1622-1625
Publication Date(Web):
DOI:10.1002/anie.201006223
Co-reporter:Wanjuan Lin, Xiaomei Ma, Jieshu Qian, Ahmed I. Abdelrahman, Adrienne Halupa, Vladimir Baranov, Andrij Pich, and Mitchell A. Winnik
Langmuir 2011 Volume 27(Issue 11) pp:7265-7275
Publication Date(Web):May 11, 2011
DOI:10.1021/la201013v
This article describes the synthesis and characterization of two series of functional polyelectrolyte copolymer microgels intended for bioassays based upon mass cytometry, a technique that detects metals by inductively coupled plasma mass spectrometry (ICP-MS). The microgels were loaded with Eu(III) ions, which were then converted in situ to EuF3 nanoparticles (NPs). Both types of microgels are based upon copolymers of N-isopropylacrylamide (NIPAm) and methacrylic acid (MAA), poly(NIPAm/VCL/MAA) (VCL = N-vinylcaprolactam, V series), and poly(NIPAm/MAA/PEGMA) (PEGMA = poly(ethylene glycol)methacrylate, PG series). Very specific conditions (full neutralization of the MAA groups) were required to confine the EuF3 NPs to the core of the microgels. We used mass cytometry to measure the number and the particle-to-particle variation of Eu ions per microgel. By controlling the amount of EuCl3 added to the neutralized microgels. we could vary the atomic content of individual microgels from ca. 106 to 107 Eu atoms, either in the form of Eu3+ ions or EuF3 NPs. Leaching profiles of Eu ions from the hybrid microgels were measured by traditional ICP-MS.
Co-reporter:Daniel Majonis, Olga Ornatsky, Robert Kinach, and Mitchell A. Winnik
Biomacromolecules 2011 Volume 12(Issue 11) pp:
Publication Date(Web):September 28, 2011
DOI:10.1021/bm201011t
We describe the synthesis of metal-chelating polymers (MCPs) with four different pendant polyaminocarboxylate ligands (EDTA, DTPA, TTHA, DOTA) and an orthogonal end-group, either a fluorescein molecule or a bismaleimide linker for antibody attachment. Polymer characterization by a combination of 1H NMR, UV/vis absorption measurements, and thermal gravimetric analysis (TGA) indicated that each chain of the fluorescein-terminated polymers contained one dye molecule. These polymer samples were loaded with three different types of lanthanide ions as well as palladium and platinum ions. The numbers of metal atoms per chain were determined by a combination of UV/vis and conventional ICP-MS measurements. The experiments with lanthanide ions demonstrated that a net anionic charge on the polymer is important for water solubility. These experiments also showed that at least one type of lanthanide ion (La3+) is capable of forming a bimetallic complex with pendant DTPA groups. Conditions were developed for loading these polymers with palladium and platinum ions. While these polymers could be conjugated to antibodies, the presence of Pd or Pt ions in the polymer interfered with the ability of the antibody to recognize its antigen. For example, a goat anti-mouse (secondary) antibody labeled with polymers that contain Pd or Pt no longer recognized a primary antibody in a sandwich assay. In mass cytometry assays, these Pd- or Pt-containing MCPs were very effective in recognizing dead cells and provide a new and robust assay for distinguishing live cells from dead cells.
Co-reporter:Dr. Joe B. Gilroy;Dr. Sanjib K. Patra;Dr. John M. Mitchels; Mitchell A. Winnik; Ian Manners
Angewandte Chemie 2011 Volume 123( Issue 26) pp:5973-5977
Publication Date(Web):
DOI:10.1002/ange.201008184
Co-reporter:Torben Gädt, Felix H. Schacher, Nina McGrath, Mitchell A. Winnik, and Ian Manners
Macromolecules 2011 Volume 44(Issue 10) pp:3777-3786
Publication Date(Web):April 22, 2011
DOI:10.1021/ma1029289
Diblock copolymers with a crystalline poly(ferrocenyldimethylsilane) (PFDMS) core-forming block have been previously shown to self-assemble in selective solvents for a coblock such as polyisoprene (PI) to form cylindrical micelles (where the material is asymmetric, with a PI:PFDMS block ratio of ca. >5:1) or platelets (where the block ratio is ca. 1:1). Moreover, upon addition of further cylinder-forming block copolymer to the ends of the crystalline cores of the cylinders, the faces of the platelets and also the surfaces of thin films of PFDMS homopolymer has been shown to initiate the further growth of cylinders by a living self-assembly process. This is believed to involve an epitaxial growth mechanism. To obtain more detailed insight and to examine the generality of this behavior, we report here detailed comparative studies of the analogous poly(ferrocenyldiethylsilane) (PFDES) homopolymer and the corresponding PI−PFDES diblock copolymers. Significantly, although PI-b-PFDES diblock copolymers with a semicrystalline PFDES core-forming block show similarities to their known PFDMS counterparts in terms of their self-assembly behavior in selective solvents for PI, important differences were also observed. For example, a pronounced tendency of PFDES diblock copolymers to form tape-like structures in solution was noted for PI:PFDES block ratios of ca. 6:1. Uniform cylindrical structures were obtained as the exclusive morphology by increasing the length of the PI block to block ratios of 19:1. Nevertheless, the successful crystallization-driven living self-assembly of PFDES block copolymers involving homoepitaxial growth was demonstrated by the addition of block copolymer unimers to preformed stub-like crystallites formed by sonication. This allowed controlled growth of monodisperse cylinders with the length controlled by the unimer to seed ratio. However, heteroepitaxial growth of PFDES block copolymer from seed micelles of the PFDMS analogue (and vice versa) could not be accomplished. This may be a consequence of the lattice mismatch between the materials and/or kinetic effects. The results demonstrate that crystallization-driven living self-assembly is not limited to PFDMS diblock copolymers and suggest that, although significant differences in self-assembly behavior are likely, this process may be expected to be applicable to other diblock copolymers with a semicrystalline core-forming block.
Co-reporter:Walter F. Schroeder, Yuanqin Liu, J. Pablo Tomba, Mohsen Soleimani, Willie Lau, Mitchell A. Winnik
Polymer 2011 Volume 52(Issue 18) pp:3984-3993
Publication Date(Web):18 August 2011
DOI:10.1016/j.polymer.2011.06.028
In this article we use fluorescence resonance energy transfer (FRET) to investigate how a classic coalescing aid, such as 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol™) (TX), acts on the earliest stages of polymer diffusion as the latex film is still drying. In our approach, we temporarily arrest the drying process of a partially wet latex film by sealing it in an airtight chamber previously cooled to near the latex Tg. At these conditions, we are able to effectively stop the drying process and the polymer diffusion. FRET measurements at various locations on such a sample provide us information about the mechanism operating at the initial stages of polymer diffusion as the latex film is still drying. We complete our study with FRET measurements carried out at longer aging times on predried latex films. We analyze our diffusion data in terms of free volume theory and propose a mechanism that can account for the results obtained.
Co-reporter:Yi Liang, Ahmed I. Abdelrahman, Vladimir Baranov, Mitchell A. Winnik
Polymer 2011 Volume 52(Issue 22) pp:5040-5052
Publication Date(Web):13 October 2011
DOI:10.1016/j.polymer.2011.08.056
Lanthanide-encoded polystyrene microspheres with methacrylic acid (MAA) as a co-monomer and with diameters on the order of 2 μm and a very narrow size distribution were synthesized by two-stage dispersion polymerization (2-DisP). These microspheres were designed as a platform for mass cytometry-based bioassays. Different lanthanides (Ln) were loaded into these microspheres during the synthesis, through the addition of LnCl3 salts and excess MAA to the reaction after about 10% conversion of styrene, i.e., well after the microsphere nucleation stage was complete. Different levels of MAA were employed to investigate the relationship between the number of carboxyl group on the particle surface and the amount of MAA used. The reaction remained well controlled with both 2 and 4 wt % MAA. As monitored by inductively coupled plasma (ICP) mass spectrometry, we found high incorporation efficiency (>95%) of Ln ions into the particles when the total amount of LnCl3 salts in the reaction mixture was sufficiently small. The Ln incorporation efficiency decreased with the increasing amount of LnCl3 salts. Mass cytometry analysis shows that individual microspheres contain ca. 105–108 chelated lanthanide ions, either a single element or a mixture of elements. This method of incorporating lanthanide into P(S-MAA) particles through the second stage of two-stage dispersion polymerization yields microspheres suitable for the highly multiplexed detection of biomolecules.
Co-reporter:Dr. Joe B. Gilroy;Dr. Sanjib K. Patra;Dr. John M. Mitchels; Mitchell A. Winnik; Ian Manners
Angewandte Chemie International Edition 2011 Volume 50( Issue 26) pp:5851-5855
Publication Date(Web):
DOI:10.1002/anie.201008184
Co-reporter:Sebastian Berger, Olga Ornatsky, Vladimir Baranov, Mitchell A. Winnik and Andrij Pich
Journal of Materials Chemistry A 2010 vol. 20(Issue 24) pp:5141-5150
Publication Date(Web):12 Apr 2010
DOI:10.1039/C0JM00075B
In this article we demonstrate that hybrid nanogels can be prepared by encapsulation of reactive nanoparticles (NPs) directly during nanogel synthesis. Nanogels investigated in present study consist of poly(N-vinylcaprolactam-co-(2-acetoacetoxyethyl) methacrylate) copolymer. The modification of the LaF3:Eu nanoparticle surface with reactive double bonds allows effective incorporation of the NPs into the nanogel structure. This approach ensures effective encapsulation of varying amounts of NPs into the nanogel interior with a loading efficiency close to 95%. The NPs are covalently bound to the nanogel core, and no NP leakage occurs. Reactive NPs act as multifunctional cross-linking agents and increase the cross-linking degree of the nanogels. We demonstrate the possibility of the incorporation of LaF3 nanoparticles doped with different ions (Eu, Tb, Pr, Gd) or nanoparticle mixtures into nanogels. These nanogels exhibit temperature-sensitive properties and superior colloidal stability in water and other aqueous media.
Co-reporter:Mingfeng Wang, Meng Zhang, James Li, Sandeep Kumar, Gilbert C. Walker, Gregory D. Scholes, and Mitchell A. Winnik
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 11) pp:3160
Publication Date(Web):October 29, 2010
DOI:10.1021/am100645j
This paper describes the co-self-assembly of a polystyrene-poly(4-vinylpyridine)-poly(ethylene oxide) triblock copolymer with CdSe nanocrystals (quantum dots, QDs) and with a styrene compatible phenylenevinylene conjugated polymer (MEH-PPV) in mixtures of chloroform and 2-propanol. The polymer itself (PS577−P4VP302−PEO852, where the subscripts refer to the number average degree of polymerization) forms worm-like micelles when 2-propanol is added to a solution of the polymer in CHCl3. In the presence of increasing amounts of QDs, the structures become shorter and form only spherical hybrid micelles (with QDs bound to the surface) at 4:1 QD/polymer w/w, accompanied by free QDs. These structures retain their colloidal stability in 2-PrOH, suggesting that even the free QDs bear a surface shell of block copolymer. The presence of MEH-PPV has no affect on this self assembly. One of the most remarkable observations occurred when the samples in 2-PrOH were centrifuged to remove the free QDs accompanying the hybrid micelles. The micelles sedimented, but upon redispersion in 2-PrOH, rearranged to form colloidally stable long branched cylindrical structures including cylindrical networks.Keywords: block copolymers; colloidal nanocomposites; composites; micelles; quantum dots; self-assembly
Co-reporter:Daniel Majonis, Isaac Herrera, Olga Ornatsky, Maren Schulze, Xudong Lou, Mohsen Soleimani, Mark Nitz, and Mitchell A. Winnik
Analytical Chemistry 2010 Volume 82(Issue 21) pp:8961
Publication Date(Web):October 12, 2010
DOI:10.1021/ac101901x
We describe the synthesis and characterization of metal-chelating polymers with a degree of polymerization of 67 and 79, high diethylenetriaminepentaacetic acid (DTPA) functionality, Mw/Mn ≤ 1.17, and a maleimide as an orthogonal functional group for conjugation to antibodies. The polymeric disulfide form of the DPn = 79 DTPA polymer was analyzed by thermogravimetric analysis to determine moisture and sodium-ion content and by isothermal titration calorimetry (ITC) to determine the Gd3+ binding capacity. These results showed each chain binds 68 ± 7 Gd3+ per chain. Secondary goat antimouse IgG was covalently labeled with the maleimide form of the DTPA polymer (DPn = 79) carrying 159Tb. Conventional ICPMS analysis of this conjugate showed each antibody carried an average of 161 ± 4 159Tb atoms. This result was combined with the ITC result to show there are an average of 2.4 ± 0.3 polymer chains attached to each antibody. Eleven monoclonal primary antibodies were labeled with different lanthanide isotopes using the same labeling methodology. Single cell analysis of whole umbilical cord blood stained with a mixture of 11 metal-tagged antibodies was performed by mass cytometry.
Co-reporter:Stuart C. Thickett, Ahmed I. Abdelrahman, Olga Ornatsky, Dmitry Bandura, Vladimir Baranov and Mitchell A. Winnik
Journal of Analytical Atomic Spectrometry 2010 vol. 25(Issue 3) pp:269-281
Publication Date(Web):24 Dec 2009
DOI:10.1039/B916850H
We present the synthesis and characterization of monodisperse, sub-micron poly(styrene) (PS) particles loaded with up to and including 107 lanthanide (Ln) ions per particle. These particles have been synthesized by seeded emulsion polymerization with a mixture of monomer and a pre-formed Ln complex, and analyzed on a particle-by-particle basis by a unique inductively coupled plasma mass cytometer. Seed particles were prepared by surfactant-free emulsion polymerization (SFEP) to obtain large particle sizes in aqueous media. Extensive surface acid functionality was introduced using the acid-functional initiator ACVA, either during seed latex synthesis or in the second stage of polymerization. The loading of particles with three different Ln ions (Eu, Tb, and Ho) has proven to be close to 100% efficient on an individual and combined basis. Covalent attachment of metal-tagged peptides and proteins such as Neutravidin to the particle surface was shown to be successful and the number of bound species can be readily determined. We believe these particles can serve as precursors for multiplexed, bead-based bio-assays utilizing mass cytometric detection.
Co-reporter:Ahmed I. Abdelrahman, Olga Ornatsky, Dmitry Bandura, Vladimir Baranov, Robert Kinach, Sheng Dai, Stuart C. Thickett, Scott Tanner and Mitchell A. Winnik
Journal of Analytical Atomic Spectrometry 2010 vol. 25(Issue 3) pp:260-268
Publication Date(Web):06 Jan 2010
DOI:10.1039/B921770C
We examine the suitability of metal-containing polystyrene beads for the calibration of a mass cytometer instrument, a single particle analyser based on an inductively coupled plasma ion source and a time of flight mass spectrometer. These metal-containing beads are also verified for their use as internal standards for this instrument. These beads were synthesized by multiple-stage dispersion polymerization with acrylic acid as a comonomer. Acrylic acid acts as a ligand to anchor the metal ions within the interior of the beads. Mass cytometry enabled the bead-by-bead measurement of the metal-content and determination of the metal-content distribution. Beads synthesized by dispersion polymerization that involved three stages were shown to have narrower bead-to-bead variation in their lanthanide content than beads synthesized by 2-stage dispersion polymerization. The beads exhibited insignificant release of their lanthanide content to aqueous solutions of different pHs over a period of six months. When mixed with KG1a or U937 cell lines, metal-containing polymer beads were shown not to affect the mass cytometry response to the metal content of element-tagged antibodies specifically attached to these cells.
Co-reporter:Mingfeng Wang;Seep Kumar;Neil Coombs;Gregory D. Scholes
Macromolecular Chemistry and Physics 2010 Volume 211( Issue 4) pp:393-403
Publication Date(Web):
DOI:10.1002/macp.200900511
Co-reporter:Seungmin Hong, Mohsen Soleimani, Yuanqin Liu, Mitchell A. Winnik
Polymer 2010 Volume 51(Issue 14) pp:3006-3013
Publication Date(Web):24 June 2010
DOI:10.1016/j.polymer.2010.04.028
Small amounts of hydrogen-bonding comonomers such as N-(2-methacryloxyethyl)ethylene urea (MEEU) are often included in latex particle synthesis to promote adhesion of latex films to metals and old surfaces. Little is known about how these monomers affect the latex film formation process. Here we examine the influence of 1–7 wt.% MEEU on butyl acrylate-methyl methacrylate copolymer latex films using fluorescence resonance energy transfer (FRET) measurements, in conjunction with donor- and acceptor-labeled latex particles, to study the rates of polymer diffusion in these films. The presence of MEEU in the copolymer leads to small increases in the polymer glass transition temperature (Tg). It also tends to retard the rate of polymer diffusion. This effect, however, is very sensitive to the humidity of the surrounding atmosphere. It appears that moisture taken up in the film minimizes the influence of MEEU groups on the rate of polymer diffusion.
Co-reporter:Walter F. Schroeder, Yuanqin Liu, J. Pablo Tomba, Mohsen Soleimani, Willie Lau and Mitchell A. Winnik
The Journal of Physical Chemistry B 2010 Volume 114(Issue 9) pp:3085-3094
Publication Date(Web):February 17, 2010
DOI:10.1021/jp9118875
We describe fluorescence resonance energy transfer (FRET) experiments carried out to examine the effect of ethylene glycol and propylene glycol on the early stages of polymer diffusion in poly(butyl acrylate-co-methyl methacrylate) latex films. In our approach, we temporarily arrest the drying process of a wet latex film by sealing the film in a previously cooled airtight sample chamber. This arrests propagation of the drying front and suppresses polymer diffusion during the measurements. We then measure donor fluorescence decays from 0.5 mm diameter spots at various locations on the film. From our analysis, we obtain information about the earliest stages of polymer diffusion as the film is still drying. We also investigate the effect of these glycols on polymer diffusion at longer aging times on predried latex films. Ethylene glycol and propylene glycol retard polymer diffusion at early times immediately after the passing of the drying front but enhance the rate of polymer diffusion at later aging times. This behavior is described quantitatively in terms of free-volume theory and the partitioning of the glycols between the aqueous and polymer phases in the film.
Co-reporter:Meng Zhang, Mingfeng Wang, Shu He, Jieshu Qian, Amir Saffari, Anna Lee, Sandeep Kumar, Yasser Hassan, Axel Guenther, Gregory Scholes and Mitchell A. Winnik
Macromolecules 2010 Volume 43(Issue 11) pp:5066-5074
Publication Date(Web):May 13, 2010
DOI:10.1021/ma1004106
Poly(styrene-b-4-vinylpyridine) (PS404-b-P4VP76, where the subscripts refer to the number-averaged degree of polymerization) forms spherical crew-cut micelles with a PS core and a P4VP corona when 2-propanol is added to a solution of the polymer in chloroform. When the CHCl3 solution also contains CdSe quantum dots, hybrid micelles form with the QDs bound to the corona. Here we report that vigorous magnetic stirring of a solution of these hybrid micelles in a solution containing 73 vol % 2-propanol leads to a morphology transformation to form three-dimensional wormlike networks that have structural features similar to that first reported by Jain and Bates [Science 2003, 300, 460−464] for a poly(butadiene-b-ethylene oxide) block copolymer in water. Under the influence of shear, PS404-b-P4VP76 micelles appear to aggregate and then rearrange to form colloidally stable networks consisting of wormlike micelles, uniform in width, that are present as loops and tails connected by T- and Y-junctions. The wormlike micelles are similar in width to the original hybrid micelles, whereas the tails of the micelles have thicker bulbous end-caps. This morphology transition is extremely sensitive to solvent composition and is also affected by the stirring rate.
Co-reporter:Mingfeng Wang, Ghasem Rezanejade Bardajee, Sandeep Kumar, Mark Nitz, Gregory D. Scholes, Mitchell A. Winnik
Journal of Chromatography A 2009 Volume 1216(Issue 25) pp:5011-5019
Publication Date(Web):19 June 2009
DOI:10.1016/j.chroma.2009.04.060
We explore the use of preparative size-exclusion chromatography (SEC) and high-performance liquid chromatography (HPLC) to purify quantum dots (QDs) after surface modification. In one example, in which Bio-Beads (S-X1) were used as the packing material for the preparative SEC column, CdSe QDs treated with a functional coumarin dye could be separated from the excess free dye by using tetrahydrofuran (THF) as the mobile phase. This column was unable to separate polymer-coated QDs from free polymer (M ∼ 8000) because of the relatively low cutoff mass of the column. Here a preparative HPLC column packed with TOYOPEARL gel allowed the effective separation of polymer-bound QDs from the excess free polymer by using N-methyl-2-pyrrolidinone (NMP) as the mobile phase. When other solvents such as absolute ethanol, acetonitrile, THF, and THF–triethylamine mixtures were used as the eluent, QDs stuck to the column. While NMP was an effective medium to remove excess free polymer from the QDs, it was difficult to transfer the purified QDs to more volatile solvents and maintain colloidal stability.
Co-reporter:Kangqing Deng;Neda Felorzabihi;Zhaohua Jiang;Zhihui Yin;Philip V. Yaneff;Rose A. Ryntz
Polymers for Advanced Technologies 2009 Volume 20( Issue 3) pp:235-245
Publication Date(Web):
DOI:10.1002/pat.1256
Abstract
Thermoplastic olefins (TPOs) are an important class of material used in the automotive industry. They are blends of isotactic polypropylene (iPP) and a polyolefin impact modifier. Chlorinated polyolefin (CPO) is a polymer used as an adhesion promoter to promote the paintability of TPO. The synthesis of a coumarin dye-labeled chlorinated (21.8 wt% Cl) maleated polypropylene (CPO), HY dye-labeled MEBR (maleated ethylene-butene copolymer with 28 wt% butene), and CPO (21.8 wt% Cl) was described. They were introduced as tracers into iPP/EBR9 (ethylene-butene copolymer with 9 wt% butene), iPP/CPO, EBR9/CPO binary, and iPP/EBR9/CPO ternary blends. The annealing effect on morphologies of the blends was examined by laser scanning confocal fluorescent microscopy (LSCFM). LSCFM revealed that the annealing caused phase coarsening in iPP/CPO and iPP/EBR blends, but had no obvious effect on the morphology of EBR/CPO blends, while in iPP/EBR/CPO ternary blends, iPP and EBR formed a completely separate domain, iPP and CPO formed their own domains EBR was distributed in the CPO domains. The morphology of iPP, EBR, and CPO binary blends was further investigated by SEM. SEM images showed that EBR and CPO interpenetrated each other on the nanometer scale in EBR/CPO blends, while obvious phase separation was observed in iPP/CPO and iPP/EBR blends. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) results showed that iPP and EBR, iPP and CPO crystallized respectively in binary blends, while there was a new population of crystals formed in EBR/CPO blend. Further exploration by dynamic mechanical analysis (DMA) revealed that there were two β relaxation transitions in iPP/CPO and iPP/EBR blends, and only one β relaxation transition with a small shoulder in EBR/CPO blends. Thus, we concluded that iPP/EBR and iPP/CPO blends are immiscible; the EBR/CPO blend is miscible in the melt and partially miscible in solid state, which is in agreement with the predictions based on calculations of the results by binary interaction energy density (Bij–Bc). Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Kangqing Deng, Mitchell A. Winnik, Ning Yan, Zhaohua Jiang, Philip V. Yaneff, Rose A. Ryntz
Polymer 2009 50(14) pp: 3225-3233
Publication Date(Web):
DOI:10.1016/j.polymer.2009.04.079
Co-reporter:Mingfeng Wang, Meng Zhang, Conrad Siegers, Gregory D. Scholes and Mitchell A. Winnik
Langmuir 2009 Volume 25(Issue 24) pp:13703-13711
Publication Date(Web):May 18, 2009
DOI:10.1021/la900523s
We report the incorporation of various inorganic nanoparticles (NPs) (PbS, LaOF, LaF3, and TiO2, each capped by oleic acid, and CdSe/ZnS core/shell QDs capped by trioctylphosphine oxide) into vesicles (d = 70−150 nm) formed by a sample of poly(styrene-b-acrylic acid) (PS404-b-PAA62, where the subscripts refer to the degree of polymerization) in mixtures of tetrahydrofuran (THF), dioxane, and water. The block copolymer formed mixtures of crew-cut micelles and vesicles with some enhancement of the vesicle population when the NPs were present. The vesicle fraction could be isolated by selective sedimentation via centrifugation, followed by redispersion in water. The NPs appeared to be incorporated into the PAA layers on the internal and external walls of the vesicles (strongly favoring the former). NPs on the exterior surface of the vesicles could be removed completely by treating the samples with a solution of ethylenediaminetetraacetate (EDTA) in water. The triangular nanoplatelets of LaF3 behaved differently. Stacks of these platelets were incorporated into solid colloidal entities, similar in size to the empty vesicles that accompanied them, during the coassembly as water was added to the polymer/LaF3/THF/dioxane mixture.
Co-reporter:J. Pablo Tomba;Daniel Portinha;Walter F. Schroeder
Colloid and Polymer Science 2009 Volume 287( Issue 3) pp:
Publication Date(Web):2009 March
DOI:10.1007/s00396-009-1996-1
This paper describes experiments that investigate the use of low glass transition temperature (Tg) latex particles consisting of oligomer to promote polymer diffusion in films formed from high molar mass polymer latex. The chemical composition of both polymers was similar. Fluorescence resonance energy transfer (FRET) was used to follow the rate of polymer diffusion for samples in which the high molar mass polymer was labeled with appropriate donor and acceptor dyes. In these latex blends, the presence of the oligomer (with Mn = 24,000 g/mol, Mw/Mn = 2) was so effective at promoting the interdiffusion of the higher molar mass poly(butyl acrylate-co-methyl methacrylate; PBA/MMA = 1:1 by weight) polymer (with Mn = 43,00 g/mol, Mw/Mn = 3) that a significant amount of interdiffusion occurred during film drying. Additional polymer diffusion occurred during film aging and annealing, and this effect could be described quantitatively in terms of free-volume theory.
Co-reporter:Neda Felorzabihi, Pablo Froimowicz, Jeffrey C. Haley, Ghasem Rezanejad Bardajee, Binxin Li, Enrico Bovero, Frank C. J. M. van Veggel and Mitchell A. Winnik
The Journal of Physical Chemistry B 2009 Volume 113(Issue 8) pp:2262-2272
Publication Date(Web):January 30, 2009
DOI:10.1021/jp807637s
Fluorescence resonance energy transfer (FRET) experiments were carried out on three pairs of donor−acceptor dyes in polymer films in which the donor dyes had absorption maxima in the range of 350−450 nm. Two of the donors, a coumarin dye and a naphthalimide dye covalently bound to polystyrene, gave nonexponential decays in the absence of acceptors. The decay profiles could be fitted to a stretched exponential form with a β value on the order of 0.9. We developed equations for analyzing donor fluorescence intensity decay profiles for donor−acceptor mixtures in rigid matrices for the case of donors showing relatively small deviations from exponentiality. To test these equations, we calculate values of the Förster radius (R0FR) from the decay profile data and compare these values to the Förster radius R0SO determined by the traditional spectral overlap method. Agreement between these values validates the methodology developed here for the use of such donor dyes in FRET studies of more complex polymer systems.
Co-reporter:Feng He, Torben Gädt, Marcus Jones, Gregory D. Scholes, Ian Manners and Mitchell A. Winnik
Macromolecules 2009 Volume 42(Issue 20) pp:7953-7960
Publication Date(Web):September 30, 2009
DOI:10.1021/ma900990y
A fluorescent ABC triblock copolymer containing poly(ferrocenyldimethylsilane) (PFS) and poly(2-vinylpyridine) (P2VP) moieties in the segments was synthesized via living anionic polymerization followed by quenching the living chains using a π-conjugated poly(2,5-di(2′-ethylhexyloxy)-1,4-phenylvinylene aldehyde (PDEHPV-CHO) homopolymer. The resulting triblock copolymer poly(ferrocenyldimethylsilane-b-2-vinylpyridine-b-2,5-di(2′-ethylhexyloxy)-1,4-phenylvinylene) (PFS-b-P2VP-b-PDEHPV) underwent self-assembly in 2-propanol to form cylindrical micelles. 2-Propanol is a good solvent for P2VP, a modest solvent for PDEHPV, and a poor solvent for PFS. The cylindrical shape of the micelles is likely related to the semicrystalline nature of the PFS in the core. The PDEHPV block showed strong green-yellow fluorescence both for polymers dissolved as discrete molecules in tetrahydrofuran (THF), a good solvent for all three components, and as micelles in 2-propanol. The fluorescence quantum yields were 56% for the triblock copolymer in THF and ca. 17% for the micelles in 2-propanol. Because ferrocene units are powerful fluorescence quenching entities, we surmise that in both cases, the P2VP block acts as a spacer to minimize the quenching of PDEHPV fluorescence by the PFS block. Taking advantage of the fluorescence of the PDEHPV block, we were able to obtain images of the block copolymer micelles and their flower-like aggregates in 2-propanol solution by laser confocal fluorescence microscopy.
Co-reporter:Mingfeng Wang, Meng Zhang, Jieshu Qian, Fei Zhao, Lei Shen, Gregory D. Scholes and Mitchell A. Winnik
Langmuir 2009 Volume 25(Issue 19) pp:11732-11740
Publication Date(Web):September 4, 2009
DOI:10.1021/la900614e
We report a method for preparing highly photoluminescent, water-soluble CdSe/CdS/ZnS core/shell/shell and CdSe/ZnS core/shell quantum dots (QDs) colloidally stabilized by double hydrophilic copolymers. The polymers, either a diblock copolymer poly(ethylene glycol-b-2-N,N-dimethylaminoethyl methacrylate) (PEG-b-PDMA) or a statistical copolymer poly(oligoethylene glycol methacrylate-co-2-N,N-dimethylaminoethyl methacrylate) (POEG-co-PDMA), were able to replace the hexadecylamine (HDA) or trioctylphosphine oxide (TOPO) ligands on the surface of the as-synthesized QDs and impart water-solubility and colloidal stability to the QD nanocrystals. In water, the [CdSe/ZnS]/POEG-co-PDMA colloids were present in the form of aggregates with a mean apparent hydrodynamic radius Rh of 54 nm and a narrow size distribution. Although the photoluminescence (PL) quantum yield (QY) of the polymer-treated QDs decreased upon transfer from an organic medium to water, much of this loss in brightness could be restored by the addition to the solution of an excess of a water-soluble primary amine such as 3-amino-propanol (APP). This chemical-activation strategy of adding primary amines as PL activators to polymer-stabilized QDs did not lead to a spectral shift of either the absorption or emission of the QDs in water.
Co-reporter:Daniele Fava;Zhihong Nie;Eugenia Kumacheva
Advanced Materials 2008 Volume 20( Issue 22) pp:4318-4322
Publication Date(Web):
DOI:10.1002/adma.200702786
Co-reporter:Lei Shen, Andrij Pich, Daniele Fava, Mingfeng Wang, Sandeep Kumar, Chi Wu, Gregory D. Scholes and Mitchell A. Winnik
Journal of Materials Chemistry A 2008 vol. 18(Issue 7) pp:763-770
Publication Date(Web):15 Jan 2008
DOI:10.1039/B713253K
We describe a new method for the preparation of fluorescent inorganic-nanoparticle composite microgels. Copolymer microgels with functional pendant groups were transferred viadialysis into tetrahydrofuran (THF) solution and mixed with colloidal solutions of semiconductor nanocrystals (quantum dots, QDs). CdSe QDs stabilized with trioctylphosphine oxide (TOPO) became incorporated into the microgels via ligand exchange of pendant imidazole (Im) groups for TOPO. PbS QDs stabilized with oleic acid were incorporated into microgels with pendant –COOH groups. This approach worked equally well with microgels based upon poly(N-isopropylacrylamide) (PNIPAM) and those based upon an acetoacetylethyl methacrylate-N-vinylcaprolactam copolymer (PVCL). These composite hybrid materials were colloidally stable in THF, and maintained their colloidal stability after transfer to water, either viadialysis or by sedimentation–redispersion. In water, the composites exhibited similar thermal responsiveness to the parent microgels, with a small shift to lower temperature in the volume phase transition. This approach allows one to use inorganic nanoparticles synthesized under optimum conditions in organic media at high temperature and to prepare composite microgels directly by mixing the components in a water-miscible organic solvent.
Co-reporter:Kenneth C.W. Chong, Mitchell A. Winnik, Lie-zhong Gong, James Nowicki
Dyes and Pigments 2008 Volume 79(Issue 2) pp:200-204
Publication Date(Web):November 2008
DOI:10.1016/j.dyepig.2008.02.007
A general method to prepare near infrared absorbing abietic acid derivatives is described in which the carboxylic acid of abietic acid is sterically hindered, making the seemingly simple esterification of the acid with a functional near infrared dye the most troublesome stage of the synthesis. Optimum results were obtained by constructing the chromophore from components previously attached to abietic acid. The spectral properties of the desired compound both in solution and within polymer films are discussed. The tackifiers increase the near infrared absorption, offering the potential for near infrared-activated hot-melt adhesives.
Co-reporter:Syed Nawazish Ali, Shakour Ghafouri, Zhihui Yin, Pablo Froimowicz, Sabira Begum, Mitchell A Winnik
European Polymer Journal 2008 Volume 44(Issue 12) pp:4129-4138
Publication Date(Web):December 2008
DOI:10.1016/j.eurpolymj.2008.09.004
We report a thermogravimetric study of the uncatalyzed and photo-acid-catalyzed decomposition of a series of polyformals and polycarbonates. Some of these polymers have previously been proposed as solventless photoresists. Such polymers should decompose at much lower temperatures when heated in the presence of strong acid than when heated in the absence of acid. In addition, decomposition should lead only to volatile break-down products. We found that most of these polymers underwent clean uncatalyzed thermal decomposition. When heated in the presence of acid, the onset of thermal decomposition occurred at much lower temperatures, as expected, but was accompanied by formation of significant amounts of non-volatile product. We also found that the extent of acid-catalyzed cross-linking (i.e., formation of non-volatile product) in the benzylic polyformals was greater than that for benzylic polycarbonates.
Co-reporter:Wanjuan Lin, Karolina Fritz, Gerald Guerin, Ghasem R. Bardajee, Sean Hinds, Vlad Sukhovatkin, Edward H. Sargent, Gregory D. Scholes and Mitchell A. Winnik
Langmuir 2008 Volume 24(Issue 15) pp:8215-8219
Publication Date(Web):July 3, 2008
DOI:10.1021/la800568k
Hydrophobic lead sulfide quantum dots (PbS/OA) synthesized in the presence of oleic acid were transferred from nonpolar organic solvents to polar solvents such as alcohols and water by a simple ligand exchange with poly(acrylic acid) (PAA). Ligand exchange took place rapidly at room temperature When a colloidal solution of PbS/OA in tetrahydrofuran (THF) was treated with excess PAA, the PbS/PAA nanocrystals that formed were insoluble in hexane and toluene but could be dissolved in methanol or water, where they formed colloidal solutions that were stable for months. Ligand exchange was accompanied by a small blue shift in the band-edge absorption, consistent with a small reduction in particle size. While there was a decrease in quantum yield associated with ligand exchange and transfer to polar solvents, as is commonly found for colloidal quantum dots, the quantum yields determined were impressively high: PbS/OA in toluene (82%) and in THF (58%); PbS/PAA in THF (42%) and in water (24%). The quantum yields for the PbS/PAA solutions decreased over time as the solutions were allowed to age in the presence of air.
Co-reporter:Lei Shen, Hai Wang, Gerald Guerin, Chi Wu, Ian Manners and Mitchell A. Winnik
Macromolecules 2008 Volume 41(Issue 12) pp:4380-4389
Publication Date(Web):May 20, 2008
DOI:10.1021/ma702852j
A sample of poly(ferrocenyldimethylsilane)-b-poly(2-vinylpyridine) (PFS23-b-P2VP230), with a short PFS block and a P2VP block 10-fold higher in degree of polymerization, forms spherical micelles when dissolved in ethanol. Over time (hours, days, and weeks), these solutions undergo a micelle sphere-to-cylinder transition eventually forming rather stiff, uniform fiber-like micelles with a core width of 10 nm, lengths between 20 and 50 µm, and approximately four polymer molecules per nm length. Here, we report the results of a combination of transmission electron microscopy, wide-angle X-ray scattering (WAXS), as well as static and dynamic laser light scattering measurements to follow the structural evolution. One key observation is the onset of partial aggregation of spherical micelles after an initial induction period (hours), so that the system as it ages consists of mixtures of free spherical micelles, micelle aggregates, and elongated structures with a high aspect ratio. Another important observation is the growth in intensity and sharpness of the WAXS peak characteristic of crystalline PFS domains as the number and uniformity of the cylindrical micelles increases. This formation of crystalline domains is the likely driving force for the structural transformation.
Co-reporter:Mingfeng Wang, Shan Zou, Gerald Guerin, Lei Shen, Kangqing Deng, Marcus Jones, Gilbert C. Walker, Gregory D. Scholes and Mitchell A. Winnik
Macromolecules 2008 Volume 41(Issue 19) pp:6993-7002
Publication Date(Web):September 4, 2008
DOI:10.1021/ma800777m
We report the synthesis of a new polythiophene (PT)-based molecular brush (PT-g-PDMA) by growing poly(N,N-dimethylaminoethyl methacrylate) (PDMA) chains from the PT backbone by ATRP. The polymer shows a reversible pH response in aqueous solution. A combination of AFM, light scattering, and 1H NMR measurements indicated that the polymer brush forms a more extended conformation with a decrease in pH from 8 to 2 due to the protonation of the Me2N− groups and increased repulsive interactions among the PDMA side chains, which drives the red shift of the absorption and PL spectra of the PT backbone. The good solubility of this polythiophene-based brush in a wide range of solvents is attractive for the fabrication of functional polymer composites.
Co-reporter:Jeffrey C. Haley;Yuanqin Liu
Journal of Coatings Technology and Research 2008 Volume 5( Issue 2) pp:157-168
Publication Date(Web):2008 June
DOI:10.1007/s11998-007-9061-9
The diffusion of polymer chains across the interface between distinct latex particles is the final step in latex film maturation. This step drives the transformation of a honeycomb of compacted latex particles bound by weak surface forces into a mechanically robust film. Knowledge of the onset of this diffusion process is limited. We have examined film formation in butyl acrylate-methyl methacrylate copolymer latex containing 1 wt% methacrylic acid. These films dry via a propagating drying front. We were able, via fluorescence resonance energy transfer measurements, to determine the extent of polymer interdiffusion at 23°C as a function of distance from the edge of the drying front for a series of partly wet latex films. Our apparatus allows us to arrest the latex drying process and to extract interdiffusion information from sub-millimeter regions of the drying film. We have tracked the latex drying process and subsequent polymer diffusion as a function of humidity. We find that adjacent to the drying front, increasing humidity initially delays the onset of interdiffusion, but once this initial barrier is overcome increasing humidity increases the rate of diffusion. This transition occurs within 1–2 mm of the drying front.
Co-reporter:X. Wang;H. Wang;D. J. Frankowski;P. M. Welch;M. A. Winnik;R. J. Spontak;J. Hartmann;P. G. Lam;I. Manners
Advanced Materials 2007 Volume 19(Issue 17) pp:2279-2285
Publication Date(Web):13 AUG 2007
DOI:10.1002/adma.200602230
Highly asymmetric metal-containing block copolymers are capable of forming nanotubes in solutions containing a nonpolar solvent. In this study, the time-dependent formation of these nanotubes is investigated and reveals how the aggregate nanostructures develop (see figure for an example at an early stage). These nanotubes are semicrystalline (see the diffraction pattern in the inset), suggesting that crystallization is at least partially responsible for the unique morphology formed by these block copolymers.
Co-reporter:Fugang Li, Mitchell A. Winnik, Anna Matvienko and Andreas Mandelis
Journal of Materials Chemistry A 2007 vol. 17(Issue 40) pp:4309-4315
Publication Date(Web):21 Aug 2007
DOI:10.1039/B708707A
Polypyrrole (PPy), like other conducting polymers, has a broad absorption band in the near infrared (NIR) with no evidence of fluorescence emission. We describe the preparation of PPy–EVA blends as potential hot-melt adhesives that can be activated by irradiation with NIR light. The PPy content needed to act as a thermal transducer of NIR radiation is much lower than that needed for conductivity. Blends were prepared in two ways: by blending sterically-stabilized 50 nm diameter PPy particles in water with a dispersion of 800 nm diameter ethylene–vinyl acetate copolymer (EVA) particles, and by synthesizing PPy-coated EVA core-shell particles by precipitation polymerization in water. The PPy nanoparticles and the PPy-coated EVA core-shell particles could be purified by sedimentation followed by redispersion in water to remove Fe salts. Films prepared from these particles, containing 0.1–0.5 wt% PPy, showed a strong NIR absorbance in the range of our spectrometer (700–1100 nm) with a weaker absorbance in the visible region. Photothermal radiometry (PTR) measurements indicate that these blends show good promise as potential NIR-activated adhesives, which are essentially transparent to the eye.
Co-reporter:David A. Rider, Mitchell A. Winnik and Ian Manners
Chemical Communications 2007 (Issue 43) pp:4483-4485
Publication Date(Web):03 Sep 2007
DOI:10.1039/B704200K
Polystyrene-block-polyferrocenylsilane (PS-b-PFS) diblock copolymers were stoichiometrically oxidized in solution using salts of the one-electron oxidant tris(4-bromophenyl)ammoniumyl. Due to a redox-induced polarity change for the PFS block, self-assembly into well-defined spherical micelles occurs. The micelles are composed of a core of partially oxidized PFS segments and a corona of PS. When the micellar solutions were treated with the reducing agent decamethylcobaltocene, the spherical micelles disassemble and regenerate unassociated and pristine PS-b-PFS free chains.
Co-reporter:Neda Felorzabihi;Ghasem R. Bardajee;Jeffrey C. Haley
Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 17) pp:2333-2343
Publication Date(Web):11 JUL 2007
DOI:10.1002/polb.21226
We measured the fluorescence decays of seven different amino-coumarin dyes in polymer films of poly(methyl methacrylate) (PMMA), poly(styrene) (PS), and ethylene-butene rubber (EBR); as well as in the small molecule analogs ethyl acetate and toluene. Many of the dye-solvent and dye-polymer combinations exhibited single exponential decays with lifetimes ranging from 2.3 to 3.9 ns. Small deviations from single exponential behavior occurred for most of the dyes in EBR. Significant deviations from single exponential behavior occurred for 7-(diethylamino)-2-oxo-2H-1-benzopyran-3-carboxylic acid (coumarin-3) in ethyl acetate and in all polymer matrices and 2,3,6,7-tetrahydro-11-oxo-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-10-carboxylic acid (coumarin-343) in all of the polymer matrices. Time-resolved fluorescence spectra indicated the presence of two different excited states for coumarin-3 and coumarin-343 in PMMA; these spectra were qualitatively different from the time-resolved spectra of coumarin-3 in ethyl acetate. We rationalize these results in terms of the chemical functionalities of the various dyes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2333–2343, 2007
Co-reporter:Xudong Lou;Guohua Zhang;Isaac Herrera;Robert Kinach;Olga Ornatsky Dr.;Vladimir Baranov Dr.;Mark Nitz ;Mitchell A. Winnik
Angewandte Chemie 2007 Volume 119(Issue 32) pp:
Publication Date(Web):29 MAY 2007
DOI:10.1002/ange.200700796
Elementarer Unterschied: Ein wasserlösliches Polymer mit Chelatliganden zur Metallbindung wurde in Bioassays mit ICP-Massenspektrometrie genutzt. Die kovalente Anbindung dieser Markierung an Antikörper ergab Polymer-Antikörper-Konstrukte, die mit Lanthanoidionen (Ln3+) beladen wurden und in einem simultanen Test von fünf orthogonal markierten Antikörpern gegen Zelloberflächenantigene, deren Häufigkeit um über zwei Größenordnungen variierte, zum Einsatz kamen.
Co-reporter:Xudong Lou;Guohua Zhang;Isaac Herrera;Robert Kinach;Olga Ornatsky Dr.;Vladimir Baranov Dr.;Mark Nitz ;Mitchell A. Winnik
Angewandte Chemie International Edition 2007 Volume 46(Issue 32) pp:
Publication Date(Web):29 MAY 2007
DOI:10.1002/anie.200700796
It's elemental: A water-soluble polymer bearing multiple metal-chelating ligands has been used as a tag for bioassays with inductively coupled plasma mass spectrometry. The tag was covalently conjugated to antibodies, and the polymer–antibody constructs were loaded with lanthanide ions (Ln3+) and used for the simultaneous assay of five orthogonally labeled antibodies against cell surface antigens that differ in abundance by more than two orders of magnitude.
Co-reporter:Xiaosong Wang;Gerald Guerin;Hai Wang;Yishan Wang;Ian Manners
Science 2007 Volume 317(Issue 5838) pp:644-647
Publication Date(Web):03 Aug 2007
DOI:10.1126/science.1141382
Abstract
Block copolymers consist of two or more chemically different polymers connected by covalent linkages. In solution, repulsion between the blocks leads to a variety of morphologies, which are thermodynamically driven. Polyferrocenyldimethylsilane block copolymers show an unusual propensity to forming cylindrical micelles in solution. We found that the micelle structure grows epitaxially through the addition of more polymer, producing micelles with a narrow size dispersity, in a process analogous to the growth of living polymer. By adding a different block copolymer, we could form co-micelles. We were also able to selectively functionalize different parts of the micelle. Potential applications for these materials include their use in lithographic etch resists, in redox-active templates, and as catalytically active metal nanoparticle precursors.
Co-reporter:Kyoung Taek Kim, Chiyoung Park, Chulhee Kim, Mitchell A. Winnik and Ian Manners
Chemical Communications 2006 (Issue 13) pp:1372-1374
Publication Date(Web):01 Mar 2006
DOI:10.1039/B516625J
New macromolecular self-assembling building blocks, dendron-helical polypeptide copolymers, have been synthesized; these materials possess a well-defined 3-D shape and self-assemble in solution to form nanoribbon and lyotropic liquid crystalline phases.
Co-reporter:Kyoung Taek Kim, Mitchell A. Winnik and Ian Manners
Soft Matter 2006 vol. 2(Issue 11) pp:957-965
Publication Date(Web):21 Sep 2006
DOI:10.1039/B606272E
Dendritic-helical diblock copolypeptides, dendritic poly(L-lysine)-b-poly(γ-benzyl-L-glutamate) (PBLG-Lys) were synthesized up to 4th generation of dendritic poly(L-lysine). PBLG was synthesized by conventional ring-opening polymerization of γ-benzyl-L-glutamate-N-carboxyanhydride with heptyl amine as an initiator. The N-terminus of this PBLG was used for further coupling reactions with Nα,Nε-bis(t-butoxycarbonyl)-L-lysine pentafluorophenylester. These block copolypeptides possess well-defined 3-D structures in solution, and they self-assemble into a fibrous structure via a nanoribbon mechanism in toluene. Amphiphilic block copolypeptides were obtained after deprotecting BOC groups at the periphery of the lysine dendrimer block. Due to the well-defined size and structure of the dendritic lysine block and well-defined α-helical conformation of the PBLG block, the block copolypeptides showed a generation-dependent self-assembly behavior in aqueous solution.
Co-reporter:Paul W. Cyr;Yishan Wang;Ronald Soong;Jian Yang;Peter M. Macdonald;Liusheng Chen;Ian Manners
Photochemistry and Photobiology 2006 Volume 82(Issue 1) pp:262-267
Publication Date(Web):30 APR 2007
DOI:10.1562/2005-06-21-RA-587
We describe experiments that determine the quenching kinetics by poly(ferrocenylsilane) (PFS) for platinum octaethylporphine (PtOEP) phosphorescence in toluene solution. The phosphorescence quenching process was interpreted in terms of diffusion-controlled kinetics. Pulsed-gradient spinecho nuclear magnetic resonance (PGSE NMR) and dynamic light scattering (DLS) were used to characterize the diffusion behavior of PFS and PtOEP in toluene solution. We found that the ferrocene group present in the repeat unit of polymer backbone is a good quencher for PtOEP phosphorescence. Quenching by the polymer involves the entire PFS polymer chain instead of individual ferrocene groups. The intrinsic quenching ability of PFS was found to be higher than that of a model compound, Bu-FS, that contains a single ferrocene group.
Co-reporter:Mingfeng Wang;Tieneke E. Dykstra;Xudong Lou;Mayrose R. Salvador;Gregory D. Scholes
Angewandte Chemie 2006 Volume 118(Issue 14) pp:
Publication Date(Web):3 MAR 2006
DOI:10.1002/ange.200502538
Halt dich fest: Pyrenmarkiertes Poly((dimethylaminoethyl)methacrylat) (Pyr-PDMAEMA) wurde als mehrzähniger Ligand für CdSe-Nanokristalle (NCs) synthetisiert (siehe Bild). Die mittlere Zahl an Polymeren, die an einen NC binden, lässt sich mithilfe einer quantitativen Analysemethode bestimmen, die auf der Ausschlusschromatographie basiert. Nach der spektroskopischen Charakterisierung der eluierten Partikel bindet Pyr-PDMAEMA fest an diese NCs.
Co-reporter:Mingfeng Wang, Tieneke E. Dykstra, Xudong Lou, Mayrose R. Salvador, Gregory D. Scholes,Mitchell A. Winnik
Angewandte Chemie International Edition 2006 45(14) pp:2221-2224
Publication Date(Web):
DOI:10.1002/anie.200502538
Co-reporter:Mitchell A. Winnik;Jian Yang;Tadeusz Pakula
Macromolecular Theory and Simulations 2005 Volume 14(Issue 1) pp:9-20
Publication Date(Web):5 JAN 2005
DOI:10.1002/mats.200400073
Summary: We describe the results of Monte Carlo simulations, based on the cooperative motion algorithm, of the lamellar structure generated at finite temperature by a symmetric diblock copolymer. The (70 × 70 × 70) simulation box in which the polymer chains were embedded for each simulation was rotated, based on the interface orientation, to bring the interfacial planes of the simulated structure into parallel. We found that the interface thickness, as defined by the distribution of the junction points, became narrower at lower temperature, and that the interface plane was characterized by a waviness with a maximum peak-to-valley distance of 20–30 lattice bonds. Compared with the isotropic state (T/N = ∞), chains at lower temperatures were stretched in the direction perpendicular to the interface; but only modestly compressed in the direction parallel to the interface. Individual block chains within the lamellar domains still behave like random coils. The block copolymer molecules exhibit only a modest tendency to orient themselves with their end-to-end vector perpendicular to the plane of the lamellar interface. Considered as an ensemble average, the results we obtained are similar to those reported from small angle neutron scattering measurements for the mean conformation of the PSd blocks of symmetrical PSd-PVP diblock copolymers.
Co-reporter:Jung Kwon Oh;Liza Deleebeeck;Jude Rademacher;Rajeev Farwaha
Journal of Polymer Science Part A: Polymer Chemistry 2005 Volume 43(Issue 22) pp:5632-5642
Publication Date(Web):3 OCT 2005
DOI:10.1002/pola.21025
We describe the synthesis and characterization of a weakly cross-linked poly(methacrylic acid-co-ethyl acrylate) alkali-swellable emulsion (ASE), as well as an investigation of its influence on the rate of polymer diffusion in latex films. The films examined were formed from poly(vinyl acetate-co-butyl acrylate) latex particles containing a small amount of acrylic acid as a comonomer. Polymer diffusion rates were monitored by the energy transfer technique. We found that the presence of the ASE component, either in the acid form or fully neutralized by ammonia or sodium hydroxide, had very little effect on the polymer diffusion rate. However, in the presence of 2 wt % NH4-ASE, there was a small but significant increase in the polymer diffusion rate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5632–5642, 2005
Co-reporter:Jun Wu;J. Pablo Tomba;Jung Kwon Oh;Rajeev Farwaha;Jude Rademacher
Journal of Polymer Science Part A: Polymer Chemistry 2005 Volume 43(Issue 22) pp:5581-5596
Publication Date(Web):30 SEP 2005
DOI:10.1002/pola.21029
We describe the synthesis of dye-labeled poly(vinyl acetate-co-ethylene) (EVA) latexes with the purpose of understanding the polymer diffusion behavior in their latex films. Polymer diffusion was followed with experiments based upon fluorescence resonance energy transfer (ET). Both the batch and semibatch emulsion polymerizations of vinyl acetate−ethylene (VAc−E) were examined. The ethylene content of these EVA samples was designed at ˜20 wt % (50 mol %). Under batch emulsion polymerization conditions, the reaction is characterized by a rapid monomer conversion and an increment of E content with reaction time. VAc−E batch emulsion polymerization in the presence of the donor dye 9-phenanthryl methyl methacrylate produced EVA with non-random dye distribution, which makes these samples unsuitable for ET experiments. The semibatch emulsion polymerization of VAc−E was carried out under VAc–starved feeding conditions. The resulting EVA was characterized by constant chemical composition throughout the feed. In addition, our data suggest the presence of two components, distinct in molar mass and degree of branching, in these EVA samples. More importantly, these VAc−E polymerizations in the presence of dyes [9-phenanthryl methyl acrylate as the donor and 2′-acryloxy-4′-methyl-4-(N,N-dimethylamino)-benzophenone as the acceptor] produced EVA with random dye incorporation, making these samples effective for ET experiments. Unlike the typical polymer diffusion behavior in latex films, characterized by small extents of polymer diffusion in newly dried latex followed by an increase of the extent of diffusion upon annealing, our ET experiments showed that polymer diffusion in these EVA latex films was complete by the time the films were dry. We attribute this striking difference to the low glass transition temperature (Tg) of the EVA and to its low effective monomeric friction coefficient at the drying temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5581-5596, 2005
Co-reporter:Kyoung Taek Kim, Chiyoung Park, Guido W. M. Vandermeulen, David A. Rider, Chulhee Kim, Mitchell A. Winnik,Ian Manners
Angewandte Chemie International Edition 2005 44(48) pp:7964-7968
Publication Date(Web):
DOI:10.1002/anie.200502809
Co-reporter:Kyoung Taek Kim;Chiyoung Park;Guido W. M. Vermeulen;David A. Rider;Chulhee Kim ;Ian Manners
Angewandte Chemie 2005 Volume 117(Issue 48) pp:
Publication Date(Web):15 NOV 2005
DOI:10.1002/ange.200502809
Diblockcopolymere aus dem helicalen Polypeptid Poly(γ-benzyl-L-glutamat) und Zufallsknäuelpolymeren wie Polyferrocenylsilanen gelieren in verdünnter Lösung thermoreversibel (siehe Bild). Für die Selbstorganisation der Blockcopolymere aus helicalen Polypeptiden wird ein neuartiger Mechanismus vorgeschlagen.
Co-reporter:Xiao-Song Wang;Ian Manners
Angewandte Chemie International Edition 2004 Volume 43(Issue 28) pp:
Publication Date(Web):7 JUL 2004
DOI:10.1002/anie.200453969
Hydrosilylative crosslinking of the coronas of tubules of self-assembled poly(ferrocenyldimethylsilane-b-polymethylvinylsiloxane) (PFS–b–PVMS) formed in hexane result in shell-crosslinked organometallic nanotubes (see picture) with reversible redox behavior and tunable swellability.
Co-reporter:Xiao-Song Wang;Ian Manners
Angewandte Chemie 2004 Volume 116(Issue 28) pp:
Publication Date(Web):7 JUL 2004
DOI:10.1002/ange.200453969
Die vernetzende Hydrosilylierung der Peripherie von röhrenförmigen Poly(ferrocenyldimethylsilan-b-polymethylvinylsiloxan)-Micellen, die in Hexan selbstorganisiert entstehen, führt zu metallorganischen Nanoröhren (siehe Bild) mit kontrolliertem Quellverhalten. Die Nanoröhren können reversibel oxidiert werden.
Co-reporter:Jean-François Gohy Dr.;Bas G. G. Lohmeijer Ir.;Alexer Alexeev Dr.;Xiao-Song Wang Dr.;Ian Manners Dr. Dr.;Ulrich S. Schubert Dr.
Chemistry - A European Journal 2004 Volume 10(Issue 17) pp:
Publication Date(Web):19 JUL 2004
DOI:10.1002/chem.200400222
A supramolecular AB diblock copolymer has been prepared by the sequential self-assembly of terpyridine end-functionalized polymer blocks by using RuIII/RuII chemistry. By this synthetic strategy a hydrophobic poly(ferrocenylsilane) (PFS) was attached to a hydrophilic poly(ethylene oxide) (PEO) block to give an amphiphilic metallo-supramolecular diblock copolymer (PEO/PFS block ratio 6:1). This compound was used to form micelles in water that were characterized by a combination of dynamic and static light scattering, transmission electron microscopy, and atomic force microscopy. These complementary techniques showed that the copolymers investigated form rod-like micelles in water; the micelles have a constant diameter but are rather polydisperse in length, and light scattering measurements indicate that they are flexible. Crystallization of the PFS in these micelles was observed by differential scanning calorimetry, and is thought to be the key behind the formation of rod-like structures. The cylindrical micelles can be cleaved into smaller rods whenever the temperature of the solution is increased or they are exposed to ultrasound.
Co-reporter:Frédéric Tronc;Bansi Lal Kaul;Jean-Christophe Graciet
Journal of Polymer Science Part A: Polymer Chemistry 2004 Volume 42(Issue 8) pp:1999-2009
Publication Date(Web):8 MAR 2004
DOI:10.1002/pola.20023
We describe the synthesis of several different polycarbonate particles by miniemulsion polymerization. The monomers were allylmethyl carbonate (AlMeC), di(ethylene glycol) bisallylcarbonate (DBAC), and 4-vinyl-1,3-dioxan-2-one [vinyl ethylene carbonate (VEC)]. For these polymerizations, higher monomer conversions were obtained with oil-soluble initiators (azobisisobutyronitrile and benzoyl peroxide) than with a water-soluble initiator (potassium persulfate). Benzoyl peroxide was particularly effective in yielding particles with a narrow size distribution. Although increasing amounts of a surfactant (sodium dodecyl sulfate) led to smaller particles, the choice of the monomer was the major determinant. For example, in polymerization reactions carried out at 85 °C with benzoyl peroxide as the initiator and with otherwise identical recipes, we obtained particle sizes of 181 nm with AlMeC, 296 nm with VEC, and 203 nm with DBAC. Fluorescent particles were synthesized with comonomers based on the benzothioxanthene nucleus. Because the dyes had poor solubility in the monomers, it was necessary to include typically 20 wt % bromobenzene or dichlorobenzene based on the monomer in the miniemulsion reaction mixture. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1999–2009, 2004
Co-reporter:Jung Kwon Oh;Valentina Stöeva;Jude Rademacher;Rajeev Farwaha
Journal of Polymer Science Part A: Polymer Chemistry 2004 Volume 42(Issue 14) pp:3479-3489
Publication Date(Web):7 JUN 2004
DOI:10.1002/pola.20148
We describe the synthesis of a new polymerizable coumarin derivative, [6-(β-acryloxyethoxy)-7-isopropoxy-4-methyl coumarin (3)], whose UV absorption spectrum significantly overlaps the emission spectrum of 9-alkyl phenanthrene chromophore. This dye can serve several purposes in latex films. It can be a tracer for fluorescence microscopy experiments, or it can act as a donor or acceptor dye in nonradiative energy transfer experiments. Here we emphasize its role as an energy transfer acceptor in experiments with phenanthrene as the corresponding donor. Coumarin-labeled poly(butyl methacrylate) latex dispersions could be synthesized by conventional batch emulsion polymerization with complete monomer conversion, complete dye incorporation, and uniform dye distribution. Attempts to extend this reaction to poly(vinyl acetate) copolymers failed because the dye inhibited monomer conversion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3479–3489, 2004
Co-reporter:Xiao Song Wang;Ian Manners
Macromolecular Rapid Communications 2003 Volume 24(Issue 5‐6) pp:403-407
Publication Date(Web):11 APR 2003
DOI:10.1002/marc.200390060
The first organometallic miktoarm star copolymer, PFS(PI)3 (PFS = polyferrocenyldimethylsilane, PI = polyisoprene) with PDI of 1.04 was synthesized through anionic polymerization by using SiCl4 as the coupling agent and its well-defined structure was characterized by using GPC and 1H NMR spectroscopy. In contrast to analogous diblock copolymers with similar PFS volume fractions which self-assemble to form cylindrical structures, PFS(PI)3 formed unimolecular micelles in the PI selective solvent, hexane.
Co-reporter:Jun Wu;Rajeev Farwaha;Jude Rademacher
Macromolecular Chemistry and Physics 2003 Volume 204(Issue 16) pp:1933-1940
Publication Date(Web):28 OCT 2003
DOI:10.1002/macp.200350060
We describe non-radiative energy-transfer experiments to measure the rates of polymer interdiffusion in P(MMA-co-BA) latex films formed in the presence of poly(vinyl alcohol) (PVOH). PVOH had relatively little effect on the initial efficiency of energy transfer, even when the amount of PVOH was large enough to form the continuous phase. Since ΦET(0) is a measure of the interfacial area between D- and A-labeled cells in the film, we conclude that under these circumstances the dispersed P(MMA-co-BA) copolymer is in the form of clusters with many contacts between particles containing D and A labels. These large amounts of PVOH also reduce the amount of polymer diffusion that takes place when the films are annealed. When smaller amounts of PVOH are present, the effects are measurable but much smaller. In the presence of 2 to 17 wt.-% PVOH, the polymer diffusion rate is retarded. The magnitude of the effect increases with the amount of PVOH present, and the effect is larger at 45 °C than at 63 °C. We show that the PVOH has its largest influence at the very early stages of polymer diffusion.
Co-reporter:Matthew Moffitt;Yahya Rharbi;Jiang-Dong Tong;J. P. S. Farhina;Huxi Li;M. A. Winnik;H. Zahalka
Journal of Polymer Science Part B: Polymer Physics 2003 Volume 41(Issue 6) pp:637-654
Publication Date(Web):5 FEB 2003
DOI:10.1002/polb.10408
With laser scanning confocal fluorescence microscopy, we demonstrate a novel type of morphology evolution in moderately thick films (70–100 μm) of ternary blends of polypropylene (PP), polyethylene (PE), and ethylene–propylene rubber (EPR), in which EPR is labeled with a benzothioxanthene dye (HY-EPR). The blends are prepared by solution blending, and the phase morphology evolves during the annealing of the blend films in a stainless steel mold. Our results indicate that wetting of the mold surface is a driving force in morphology evolution for the two blend compositions investigated. For 81/14/5 PP/PE/HY-EPR, phase evolution within the mold results in a laminar structure and hydrodynamic channels, features which have previously been found in thin films of polymer blends as a result of surface-directed spinodal decomposition. In a blend with a lower weight fraction of the dispersed phase (92/7/1 PP/PE/HY-EPR), we find that the PE/HY-EPR domains are larger and more polydisperse closer to the surface because of wetting of the mold wall. We also show that the phase morphology in these films can be controlled by the nature of one or both of the surfaces being varied. When one of the mold surfaces is replaced with a thin film of PP homopolymer, we observe draining of PE/HY-EPR from the PP to the mold surface, which results in a bilayer structure. A trilayer morphology is likewise obtained by the replacement of both mold surfaces with PP. We also carry out three-dimensional image reconstruction on a single PE/HY-EPR particle within the 81/14/5 PP/PE/HY-EPR blend to obtain detailed information on the interphase structure. We find that HY-EPR of this composition (30/70 ethylene/propylene) fully coats the PE dispersed phase and partially penetrates the PE droplets. This result falls between the interphase structures found for previously investigated EPR compositions (40/60 and 80/20 ethylene/propylene). © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 637–654, 2003
Co-reporter:Jian Yang;Jianping Lu
Journal of Polymer Science Part A: Polymer Chemistry 2003 Volume 41(Issue 9) pp:1225-1236
Publication Date(Web):11 MAR 2003
DOI:10.1002/pola.10644
We describe the synthesis and characterization of 1-(1-anthryl)-1-phenylethylene (1-An-E) and 1-(2-anthryl)-1-phenylethylene (2-An-E). These species were used to end cap the living end group of polyisoprene (PI) obtained by anionic polymerization in tetrahydrofuran. The anions generated were used to initiate methyl methacrylate polymerization. In this way, we synthesized two symmetrical PI-poly(methyl methacrylate) (PMMA) block copolymers each with a single dye at the junction. PI-An1-PMMA has an anthracene linked via its 1-position. PI-An2-PMMA has the anthracene linked via its 2-position. We compare the UV and fluorescence properties of the polymers to model compounds with similar chromophores. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1225–1236, 2003
Co-reporter:Mei Li;Frédéric Tronc;Bansi Lal Kaul;Jianping Lu;Jean-Christophe Graciet
Journal of Polymer Science Part A: Polymer Chemistry 2003 Volume 41(Issue 6) pp:766-778
Publication Date(Web):27 JAN 2003
DOI:10.1002/pola.10619
We describe the synthesis and characterization of latex particles labeled with a brightly fluorescent yellow dye (HY) based on the benzothioxanthene ring structure. Three dye derivatives were synthesized with different spacers connecting the HY nucleus to a methacrylate group. For one of the dyes (HY2CMA, rA), we show that the reactivity ratios with styrene (rA = 0.71, rB = 0.25) and butyl methacrylate (rA = 0.87, rB = 0.14) should lead to random dye incorporation if the amount of dye in the feed is small. Seeded emulsion polymerization fails to lead to significant dye incorporation unless large amounts of nonionic surfactant are present. In contrast, miniemulsion polymerization worked well to yield latex particles of polystyrene, poly(butyl methacrylate), and poly(methyl methacrylate) with high monomer conversion and essentially quantitative dye incorporation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 766–778, 2003
Co-reporter:Xiao-Song Wang;Ian Manners
Macromolecular Rapid Communications 2002 Volume 23(Issue 3) pp:
Publication Date(Web):18 FEB 2002
DOI:10.1002/1521-3927(20020201)23:3<210::AID-MARC210>3.0.CO;2-C
Water-soluble cylindrical micelles with an organometallic core are formed by self-assembly of the first polyferrocenylsilane-block-polyacrylate block copolymer, synthesized by anionic polymerization, in water at pH 8. A transmission electron microscopy image of the micelles is shown in the Figure.
Co-reporter:Matthew Moffitt;Yahya Rharbi;Warner Chen;M. A. Winnik;Derek W. Thurman;James P. Oberhauser;Julia A. Kornfield;Rose A. Ryntz;Jiang-Dong Tong
Journal of Polymer Science Part B: Polymer Physics 2002 Volume 40(Issue 24) pp:2842-2859
Publication Date(Web):7 NOV 2002
DOI:10.1002/polb.10301
A thermoplastic olefin blend consisting of isotactic polypropylene (PP) and an ethylene-butene copolymer (EBR) impact modifier (25 wt % EBR) was subjected to a short, high-shear pulse within the flow channel of a pressure-driven microextruder following low-shear channel filling from a reservoir of the melt. The resulting morphology was examined by laser scanning confocal fluorescence microscopy (LSCFM), with contrast provided by a fluorescent tracer in the EBR minor phase. Shear experiments were performed under isothermal conditions with a known wall shear stress for a specified duration, providing a well-defined thermal and flow history. Low-shear channel filling produces small droplets across the central region of the channel and large droplets, consistent with steady-state shear, in the regions near the channel walls. After cooling the molten blend to a crystallization temperature of 153 °C, a brief interval (5 s ∼ 1/2000 of the quiescent crystallization time) of high shear (wall shear stress: 0.1 MPa) induces rapid, highly oriented crystallization and a stratified morphology. Exsitu LSCFM reveals a “skin” at the channel walls (∼70 μm) in which greatly elongated fiberlike droplets, oriented along the flow direction, are embedded in highly oriented crystalline PP. Further from the walls but directly beside the skin layers are surprising zones in which EBR domains show no deformation or orientation. Several zones of intermediate deformation and orientation at an angle to the flow direction are located closer to the center of the channel. At the center of the channel, EBR droplets are spherical, as expected for channel flow. The various strata are explained by the interplay of droplet deformation, breakup, and coalescence with the shear-induced crystallization kinetics of the matrix. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2842–2859, 2002
Co-reporter:Jung Kwon Oh;Jun Wu;Gary P. Craun;Jude Rademacher;Rajeev Farwaha
Journal of Polymer Science Part A: Polymer Chemistry 2002 Volume 40(Issue 10) pp:1594-1607
Publication Date(Web):2 APR 2002
DOI:10.1002/pola.10216
This article describes our first experiments for preparing dye-labeled latex particles by the emulsion copolymerization of a 4/1 (w/w) mixture of vinyl acetate-butylacrylate (VAc-BA). We discuss the synthesis of acrylate derivatives of phenanthrene, anthracene, and pyrene [9-acryloxymethyl phenanthrene (7), 9-acryloxymethyl-10-methyl anthracene (8), and 1-acryloxymethyl pyrene (10)] and an allyl ether derivative of anthracene [9-allyoxymethyl-10-methyl anthracene (9)]. Although the phenanthrene derivative 7 gave latex particles with high monomer conversion and good dye incorporation, the pyrene acrylate and both anthracene comonomers strongly inhibited the free-radical reaction. To assist our search for a dye that would serve as a useful energy acceptor for phenanthrene and without suppressing VAc-BA polymerization, we also examined batch emulsion polymerization in the presence of a variety of dye derivatives—substituted anthracenes, acridines, a coumarin, and two benzophenone derivatives. All of the anthracene derivatives, as well as acridine, strongly inhibited monomer polymerization. The coumarin dye 7-hydroxy-4-methyl coumarin (22) that had only limited solubility allowed more than 90% monomer conversion. Most promising were 2-hydroxy-5-methyl benzophenone (23) and 4-N,N-dimethylamino benzophenone (24) that at 1 mol % in the monomer mixture permitted virtually quantitative monomer conversion to latex. 4′-Dimethylamino-2-acryloxy-5-methyl benzophenone (25) copolymerized well with the VAc-BA mixture, yielding latex particles in high yield and with a narrow size distribution. These dyes appear to be useful acceptor dyes for energy-transfer experiments with phenanthrene. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1594–1607, 2002
Co-reporter:Frédéric Tronc;Ronghua Liu;Sarah T. Eckersley;Gene D. Rose;J. M. Weishuhn;D. M. Meunier
Journal of Polymer Science Part A: Polymer Chemistry 2002 Volume 40(Issue 15) pp:2609-2625
Publication Date(Web):13 JUN 2002
DOI:10.1002/pola.10319
Results are presented on the synthesis and characterization of epoxy-functionalized poly(butyl acrylate-co-methyl methacrylate) latex dispersions. Two pairs of latex dispersions, of low and high molecular weights, were prepared by semicontinuous emulsion polymerization. In each pair, one latex was labeled with phenanthrene, a donor for nonradiative energy-transfer (ET) experiments, and the other was labeled with anthracene, the acceptor. Films were prepared from 1:1 mixtures of donor- and acceptor-labeled latex, and ET experiments were used to study the rate and extent of polymer diffusion in these films. A complicating feature of these experiments was that, even in the absence of an externally added crosslinking agent, the films began to gel as soon as they were formed. The rate of gel formation increased with increasing temperature but never reached 100% under the conditions of these experiments. The presence of a gel fraction caused the rate of polymer diffusion to slow down. An important parameter affecting the rate of diffusion is the amount of time the films are held at relatively low temperatures (4 and 25 °C) before being annealed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2609–2625, 2002
Co-reporter:Jung Kwon Oh;Jun Wu;Gary P. Craun;Jude Rademacher;Rajeev Farwaha
Journal of Polymer Science Part A: Polymer Chemistry 2002 Volume 40(Issue 17) pp:3001-3011
Publication Date(Web):18 JUL 2002
DOI:10.1002/pola.10384
We describe the synthesis and characterization of three new polymerizable benzophenone derivatives [2-acryloxy-5-methyl benzophenone (8), 4′-dimethylamino-2-acryloxy-5-methyl benzophenone (9), and 4′-dimethylamino-2-(β-acryloxyethyl)oxy-5-methyl benzophenone (10)]. We show that these monomers can successfully be incorporated into vinyl acetate (VAc) copolymer latex particles. These particles were prepared by semicontinuous emulsion polymerization and mini-emulsion polymerization of VAc with butylacrylate (BA) for VAc/BA = 4/1 by weight. The two monomers 9 and 10 bearing the 4′-dimethylamino group satisfy the important spectroscopic criteria required of a dye to serve as an acceptor chromophore for nonradiative energy transfer from phenanthrene (Phe) as the donor. Their UV absorption spectra suggest significant overlap with the emission spectrum of Phe, which can be incorporated into P(VAc-co-BA) latex through copolymerization with 9-acryloxymethyl Phe (2). In addition, these chromophores provide a window in their absorption spectra for excitation of the Phe chromophore at 300 nm. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3001–3011, 2002
Co-reporter:Frédéric Tronc;Warner Chen;J. M. Weishuhn;Sarah T. Eckersley;Gene D. Rose;D. M. Meunier
Journal of Polymer Science Part A: Polymer Chemistry 2002 Volume 40(Issue 22) pp:4098-4116
Publication Date(Web):4 OCT 2002
DOI:10.1002/pola.10462
This article describes the results of experiments examining the competition between the polymer diffusion rate and the crosslinking rate in low-glass-transition-temperature, epoxy-containing latex films in the presence of a diamine. We examined films formed from donor- and acceptor-labeled poly(butyl acrylate-co-methyl methacrylate-co-glycidyl methacrylate) copolymer latex and studied the influence of several parameters on the growth rate of gel content and the rate of polymer diffusion. These factors include the molecular weight of the latex polymer, the presence or absence of a diamine crosslinking agent, and the cure protocol. The results were compared to the predictions of a recent theory of the competition between crosslinking and polymer diffusion across interfaces. In the initially formed films, polymer diffusion occurs more rapidly than the chemical reaction rate. Therefore, these films fall into the fast-diffusion category of this model. In our system (unlike in the model), the latex polymer has a broad distribution of molecular weights and a distribution of diffusivities. The shortest chains contribute to the early time diffusion that we measure. At later stages of our experiment, slower diffusing species contribute to the signal that we measure. The diffusion time decreases substantially, and we observe a crossover to a regime in which the chemical reaction dominates. The increases in chain branching and gel formation bring polymer diffusion to a halt. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4098–4116, 2002
Co-reporter:Jiang-Dong Tong;Matthew Moffitt;Xiaoyu Huang;M. A. Winnik;Rose A. Ryntz
Journal of Polymer Science Part A: Polymer Chemistry 2001 Volume 39(Issue 1) pp:239-252
Publication Date(Web):28 NOV 2000
DOI:10.1002/1099-0518(20010101)39:1<239::AID-POLA270>3.0.CO;2-N
A benzothioxanthene-labeled ethylene-butene rubber has been synthesized and tested as a potential fluorescent tracer for the impact modifier (IM) phase in laser scanning confocal fluorescence microscopy (LSCFM) studies of thermoplastic olefin (TPO) morphology. The amino-functional Hostasol Yellow derivative HY-DP reacts with maleated EBR-28 to give a good labeling yield (ca. 70%) and a dye concentration of 0.051 mmol/g, when the maleated rubber is first refluxed over molecular sieves and the reaction purged with N2. Without pretreatment of the rubber and N2 purging, a lower labeling yield (0.036 mmol dye/g) is obtained and the labeled product tends to undergo crosslinking at 240 °C and subsequent dye detachment when the crosslinked gel is hydrolyzed. LSCFM studies reveal HY-labeled EBR to be completely miscible and evenly dispersed in the unlabeled EBR-9 of model TPO blends. Moreover, the HY-labeled EBR provides good fluorescence contrast between the IM droplets and the PP matrix in the TPO blend PP/EBR (80/20) (w/w) + 3 wt % labeled polymer with respect to EBR. Imaging of IM droplets down to 40 μm below the film surface of this blend has been demonstrated. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 239–252, 2001
Co-reporter:Mitchell A. Winnik;Frank Di Stefano;Jai Vanketessan;Ronghua Liu
Journal of Polymer Science Part A: Polymer Chemistry 2001 Volume 39(Issue 9) pp:1495-1504
Publication Date(Web):21 MAR 2001
DOI:10.1002/pola.1126
We describe the synthesis of three anthracene–methacrylate monomers [9-methacryloxymethyl-10-methyl anthracene (4), 9-methacryloxyethyloxymethyl-10-methyl anthracene (5), and 9-methacryloxy-10-methyl anthracene (6)] as well as their emulsion copolymers containing butylacrylate. When films prepared from latex dispersions containing 4 or 5 were heated, the anthracene (An) group was cleaved from the polymer at temperatures above 120 °C. Lower temperatures induced this reaction when strong acids were present. In 4 and 5, the polymerizable group is connected to the An ring via a 9-CH2O linkage. The cleavage reaction requires more stringent conditions when the connection involves a benzylic ether (5) instead of a benzylic ester. Polymers prepared from 6, with an AnO bond, were stable for 1 h at 150 °C in the presence of 0.5 wt % p-toluene sulfonic acid. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1495–1504, 2001
Co-reporter:Chunlin Zhou;Tze-Chi Jao
Journal of Polymer Science Part A: Polymer Chemistry 2001 Volume 39(Issue 15) pp:2642-2657
Publication Date(Web):8 JUN 2001
DOI:10.1002/pola.1241
We describe a new method for the synthesis of core–shell photolabile nanoparticles. The synthesis begins with the batch emulsion copolymerization of n-butyl methacrylate (BMA) and ethylene glycol dimethacrylate to form small (20-nm-diameter) crosslinked particles with a narrow size distribution. These seeds are then used for a second-stage emulsion copolymerizations in which BMA and various polar monomers, including methacrylic acid, are added under monomer-starved conditions. After characterization of the particles, they are transferred to an N,N-dimethylformamide solution. The cesium salt of the carboxylic acid groups is reacted with 2-bromo-1-phenyl-octadecan-1-one to convert various fractions of the COOH groups to the corresponding 2-benzoylheptadecyl ester groups. These aliphatic ester groups render the surface sufficiently hydrophobic that the particles can be dispersed in common aliphatic hydrocarbons solvents to yield colloidal dispersions, sterically stabilized by the dangling aliphatic chains. Ester groups with a phenyl ketone attached to the β-carbon are photolabile. Irradiation of the particles with UV light detaches the sterically stabilizing chains from the particle and transforms the surface groups back to COOH groups. This leads to flocculation of the particles. The emphasis in this article is on the optimization of the particle synthesis and the characterization of the particles obtained. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2642–2657, 2001
Co-reporter:Olga Vorobyova
Journal of Polymer Science Part B: Polymer Physics 2001 Volume 39(Issue 19) pp:2302-2316
Publication Date(Web):21 AUG 2001
DOI:10.1002/polb.1203
In-line studies of the initial stages of shear-induced coalescence in two-phase polymer blends were carried out with a home-built device combining a cone and plate rheometer and a fiber-optic-assisted fluorescence detection system. A blend of 90 wt % poly(2-ethylhexyl methacrylate) (PEHMA) and 10 wt % poly(butyl methacrylate) (PBMA) was prepared by the casting of films onto a solid substrate from mixed aqueous latex dispersions of the two polymers. The dispersions were prepared via emulsion polymerization under conditions in which both components were formed as spherical particles with a very narrow size distribution. By using a 14:1 particle ratio of PEHMA to PBMA, we obtained films in which 120-nm PBMA particles were surrounded by a PEHMA matrix. The blend contained phenanthrene-labeled PBMA particles and anthracene-labeled PBMA particles in a ratio of 4:1, whereas the PEHMA matrix polymer was unlabeled. We monitored the anthracene-to-phenanthrene fluorescence intensity ratio (I470/I360) as a measure of direct nonradiative energy transfer from phenanthrene to anthracene, whereas the blend was sheared at different shear rates and temperatures. Under no-shear conditions, the results of in-line experiments were in good agreement with the results of off-line measurements of energy transfer by conventional techniques. In blends under shear, the two sets of experiments, in-line and off-line, did not agree with each other. The cause of this disagreement was associated with normal forces in the blend under shear that affected the optical path length and the relative intensities of the fluorescence signals of the phenanthrene and anthracene groups in the blend. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2302–2316, 2001
Co-reporter:Olga Vorobyova
Journal of Polymer Science Part B: Polymer Physics 2001 Volume 39(Issue 19) pp:2317-2332
Publication Date(Web):21 AUG 2001
DOI:10.1002/polb.1204
This article reports the results of confocal fluorescence microscopy studies of shear-induced coalescence in binary blends of poly(2-ethylhexyl methacrylate) (PEHMA; 90 wt %) and poly(butyl methacrylate) (PBMA; 10 wt %). We prepared the blends by casting a mixture of latex dispersions of the components onto a substrate and allowing the film to dry under ambient conditions. The initial morphology of the film was a dispersion of 120-nm PBMA spheres in a continuous PEHMA matrix. One-fifth of the PBMA particles were labeled with anthracene, the emission of which we observed with confocal microscopy. The blends were sheared in a parallel-plate rheometer at 80 and 100 °C for 1 and 10 h. Careful image analysis allowed us to estimate the mean size of the dispersed phase and the width of the size distribution. The results were compared with the theoretical limits of Wu and Taylor. After 10 h of shearing, the mean particle size decreased and the particle distribution became narrower in comparison with the results obtained after 1 h of shearing. We explain this result by inferring that before the sample reached steady-state morphology, its rate of coalescence was greater than the rate of particle breakup. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2317–2332, 2001
Co-reporter:Liyan Huang;Yi Shi;Liusheng Chen;Xigao Jin;Ronghua Liu;David Mitchell
Journal of Polymer Science Part A: Polymer Chemistry 2000 Volume 38(Issue 4) pp:730-740
Publication Date(Web):25 JAN 2000
DOI:10.1002/(SICI)1099-0518(20000215)38:4<730::AID-POLA8>3.0.CO;2-1
The thermal decomposition behavior of six derivatives of maleated polyethylene was investigated by high-resolution pyrolysis gas chromatography–mass spectrometry. The results revealed that substituents attached to maleated polyethylene as amides formed from secondary amines were significantly less stable than imides formed from primary amines. Morpholine amide and N-methylaniline amide derivatives of maleated polyethylene underwent significant decomposition at 160 °C and substantial decomposition at 200 °C. In contrast, the imide derivatives of maleated polyethylene were stable for long periods of time at elevated temperatures. Following 2 min of heating, the first traces of decomposition were detected at 200 °C for the 2-aminoanthrancene imide derivative, at 255 °C for the 2-phenethylamine imide, and at 280 °C for the 9-aminomethylphenanthrene imide. With the exception of the 9-aminomethylphenanthrene imide, all other derivatives decomposed to form the corresponding amine as the single most significant volatile product. The most likely explanation for this result is that the polymer contained small amounts of succinamic acid that did not close to form the imide. We concluded that the imide was stable even to 315 °C and that the amine was lost from β-carboxyamide groups present in the sample. In the 9-aminomethylphenanthrene imide derivative, we observed no loss of amine. Instead, we observed an alternative fragmentation process yielding 9-methyl phenanthrene. The dependence of the thermal stability of these various derivatives of maleated polyethylene has important implications for the design of reactive-blending strategies for polyolefins with other functional polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 730–740, 2000
Co-reporter:Hung H. Pham
Journal of Polymer Science Part A: Polymer Chemistry 2000 Volume 38(Issue 5) pp:855-869
Publication Date(Web):8 FEB 2000
DOI:10.1002/(SICI)1099-0518(20000301)38:5<855::AID-POLA10>3.0.CO;2-Y
Cyclohexylcarbodiimidoethyl methacrylate (CCEMA) and t-butylcarbodiimidoethyl methacrylate (t-BCEMA) were prepared in a two-step synthesis. These monomers were then used to prepare carbodiimide-functionalized PBMA and PEHMA latex particles, employing two-stage emulsion polymerization, with the carbodiimide–methacrylate monomers being introduced only in the second stage under monomer-starved conditions. During emulsion polymerization, the carbodiimide moiety (NCN) was found to be unstable at pH 4, but stable when the pH of the dispersion was increased to 8, using NaHCO3 as the buffer. Survival of NCN group against hydrolysis during the polymerization, and during storage in the dispersion, was enhanced by using EHMA as the comonomer (more hydrophobic) and the t-butyl carbodiimide derivative. The t-butyl group provides more steric hindrance to the hydrolysis reaction. A decrease in the reaction temperature from 80°C to 60°C was also found to increase the extent of NCN group incorporation during emulsion polymerization. Under ideal conditions, more than 98% of the NCN groups in the monomer feed are successfully incorporated into the latex. When these latex particles are mixed with a COOH containing latex and allowed to dry, polymer diffusion leading to crosslinking occurs. Films annealed at 60°C reach a gel content of 60% in 10 h. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 855–869, 2000
Co-reporter:Ewa Odrobina;Jianrong Feng
Journal of Polymer Science Part A: Polymer Chemistry 2000 Volume 38(Issue 21) pp:3933-3943
Publication Date(Web):19 SEP 2000
DOI:10.1002/1099-0518(20001101)38:21<3933::AID-POLA100>3.0.CO;2-K
The aqueous phase of a poly(butyl methacrylate) (PBMA) latex dispersion contained an oligomeric component that was isolated after sedimentation of the PBMA latex particles. The component contained both water-soluble PBMA oligomer and some longer chain species that were present as a very fine colloidal dispersion. We describe the isolation and characterization of this component. This component was then added to a purified PBMA latex dispersion from which the aqueous component was previously removed. Latex films were prepared, and in the presence of the oligomeric material, the rate of polymer diffusion in the latex film was strongly enhanced. The magnitude of the enhancement was fit quantitatively to the Fujita–Doolittle equation, indicating that the oligomers acted like a traditional plasticizer to increase the free volume in the system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3933–3943, 2000
Co-reporter:Jose Raez;Raluca Barjovanu;Jason A. Massey Dr.;Mitchell A. Winnik ;Ian Manners
Angewandte Chemie 2000 Volume 112(Issue 21) pp:
Publication Date(Web):27 OCT 2000
DOI:10.1002/1521-3757(20001103)112:21<4020::AID-ANGE4020>3.0.CO;2-7
Co-reporter:Ronghua Liu;Matthew Moffitt;Johannes Heinemann;Rolf Mülhaupt
Journal of Polymer Science Part A: Polymer Chemistry 1999 Volume 37(Issue 22) pp:4169-4175
Publication Date(Web):21 JAN 2000
DOI:10.1002/(SICI)1099-0518(19991115)37:22<4169::AID-POLA16>3.0.CO;2-J
We describe the synthesis of a branched polyethylene-based polymer containing randomly spaced fluorescent dyes (phenanthrene or anthracene) along the polymer backbone. The dyes were introduced via ester exchange into the ethylene-methyl acrylate copolymer. Fluorescence and fluorescence-decay experiments indicated that the dyes were distributed randomly in a purely amorphous matrix. There was no indication of dye aggregation or of an enhanced local dye concentration of the sort that might be expected in a semicrystalline matrix. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4169–4175, 1999
Co-reporter:Jianrong Feng;Hung Pham;Valentina Stoeva
Journal of Polymer Science Part B: Polymer Physics 1998 Volume 36(Issue 7) pp:1129-1139
Publication Date(Web):7 DEC 1998
DOI:10.1002/(SICI)1099-0488(199805)36:7<1129::AID-POLB4>3.0.CO;2-P
Polymer diffusion across interfaces at room temperature (21°C) was analyzed by direct nonradiative energy transfer (DET) in labeled latex films. Two modellatex polymers were examined: poly(butyl methacrylate) [PBMA, Mw = 3.5 × 104, Tg (dry) = 21°C] and a copolymer of 2-ethylhexyl methacrylate with 10 wt % (acetoacetoxy)-ethyl methacrylate [P(EHMA-co-AAEM), Mw = 4.8 × 104, Tg (dry) = −7°C]. Little energy transfer due to polymer diffusion was detected for the P(EHMA-co-AAEM) latex samples in the dispersed state or dried to solids content below ca. 90%, but above 90% solids, diffusion occurs among particles. For PBMA, diffusion occurs only after the film is dried (>97% solids) and aged. In the dry PBMA films, it requires 4–5 days at 21°C to reach a significant extent of mixing (fm = 0.3–0.4). This corresponds to an estimated penetration depth dapp of 30–40 nm and a mean apparent diffusion coefficient (Dapp) of 5 × 10−4 nm2/s. The corresponding Dapp value for the dry P(EHMA-co-AAEM) sample is 5 × 10−2 nm2/s, and it takes about 25–40 min for this polymer to reach fm of 0.3–0.4 with dapp of 20–30 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1129–1139, 1998
Co-reporter:Melinda Guo, Sohyoung Her, Rachel Keunen, Shengmiao Zhang, Christine Allen, and Mitchell A. Winnik
ACS Omega Volume 1(Issue 1) pp:93-107
Publication Date(Web):July 18, 2016
DOI:10.1021/acsomega.6b00055
Elongated nanoparticles have recently been shown to have distinct advantages over their spherical counterparts in drug delivery applications. Cellulose nanocrystals (CNCs) have rodlike shapes in nature and have demonstrated biocompatibility in a variety of mammalian cell lines. In this report, CNCs are put forward as a modular platform for the production of multifunctional rod-shaped nanoparticles for cancer imaging and therapy. For the first time, PEGylated metal-chelating polymers containing diethylenetriaminepentaacetic acid (DTPA) (i.e., mPEG-PGlu(DPTA)18-HyNic and PEG-PGlu(DPTA)25-HyNic) are conjugated to CNCs to enable the chelation of radionuclides for diagnostic and therapeutic applications. The entire conjugation is based on UV/vis-quantifiable bis-aryl hydrazone-bond formation, which allows direct quantification of the polymers grafted onto the CNCs. Moreover, it has been shown that the mean number of polymers grafted per CNC could be controlled. The CNCs are also fluorescently labeled with rhodamine and Alexa Fluor 488 by embedding the probes in the polymer corona. Preliminary evaluation in a human ovarian cancer cell line (HEYA8) demonstrated that these CNCs are nontoxic and their penetration properties can be readily assessed in multicellular tumor spheroids (MCTSs) by optical imaging. These findings provide support for biomedical applications of CNCs, and further in vitro and in vivo studies are warranted to evaluate their potential as imaging and therapeutic agents for cancer treatment.Topics: Biological transport; Bonding; Drug delivery systems; Drug delivery systems; Drug discovery and Drug delivery systems; Fluorescence imaging; Imaging agents; Polyamides; Polyoxyalkylenes;
Co-reporter:Siti F. Mohd Yusoff ; Joe B. Gilroy ; Graeme Cambridge ; Mitchell A. Winnik ;Ian Manners
Journal of the American Chemical Society () pp:
Publication Date(Web):May 26, 2011
DOI:10.1021/ja202340s
Cylindrical block copolymer micelles with a crystalline poly(ferrocenyldimethylsilane) (PFDMS) core and a long corona-forming block are known to elongate through an epitaxial growth mechanism on addition of further PFDMS block copolymer unimers. We now report that addition of the semicrystalline homopolymer PFDMS28 to monodisperse short (ca. 200 nm), cylindrical seed micelles of PFDMS block copolymers results in the formation of aggregated structures by end-to-end coupling to form micelle networks. The resulting aggregates were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). In some cases, a core-thickening effect was also observed where the added homopolymer appeared to deposit and crystallize at the core–corona interface, which resulted in an increase of the width of the micelles within the networks. No evidence for aggregation was detected when the amorphous homopolymer poly(ferrocenylethylmethylsilane) (PFEMS25) was added to the cylindrical seed micelles whereas similar behavior to PFDMS28 was noted for semicrystalline polyferrocenyldimethylgermane (PFDMG30). This suggested that the crystallinity of the added homopolymer is critical for subsequent end-to-end coupling and network formation to occur. We also explored the tendency of the cylindrical seed micelles to form aggregates by the addition of PI-b-PFDMS (PI = polyisoprene) block copolymers (block ratios 6:1, 3.8:1, 2:1, or 1:1), and striking differences were noted. The results ranged from typical micelle elongation, as reported in previous work, at high corona to core-forming block ratios (PI-b-PFDMS; 6:1) to predominantly end-to-end coupling at lower ratios (PI-b-PFDMS; 2:1, 1:1) to form long, essentially linear structures. The latter process, especially for the 2:1 block copolymer, led to much more controlled aggregate formation compared with that observed on addition of homopolymers.
Co-reporter:Jieshu Qian ; Xiaoyu Li ; David J. Lunn ; Jessica Gwyther ; Zachary M. Hudson ; Emily Kynaston ; Paul A. Rupar ; Mitchell A. Winnik ;Ian Manners
Journal of the American Chemical Society () pp:
Publication Date(Web):2017-2-22
DOI:10.1021/ja500661k
Monodisperse fiber-like micelles with a crystalline π-conjugated polythiophene core with lengths up to ca. 700 nm were successfully prepared from the diblock copolymer poly(3-hexylthiophene)-block-polystyrene using a one-dimensional self-seeding technique. Addition of a polythiophene block copolymer with a different corona-forming block to the resulting nanofibers led to the formation of segmented B-A-B triblock co-micelles by crystallization-driven seeded growth. The key to these advances appears to be the formation of a relatively defect-free crystalline micelle core under the self-seeding conditions.
Co-reporter:Meng Zhang, Laetitia Rene-Boisneuf, Yiwei Hu, Kimia Moozeh, Yasser Hassan, Gregory Scholes and Mitchell A. Winnik
Journal of Materials Chemistry A 2011 - vol. 21(Issue 26) pp:NaN9701-9701
Publication Date(Web):2011/05/31
DOI:10.1039/C1JM11104C
Poly(styrene-b-4-vinylpyridine) diblock copolymers PS404-b-P4VP76 and PS317-b-P4VP76 (the subscripts indicate the degree of polymerization) self-assemble into spherical “crew-cut” micelles with a PS core and P4VP corona when prepared in a mixture of chloroform and 2-propanol. When the micelles are formed in the presence of quantum dots (QDs), the nature of the structures formed depends upon the polymer and the type of QDs. In our previous report [Macromolecules, 2010, 43, 5066–5074], PS404-b-P4VP76 + CdSe QDs formed stable spherical hybrid micelles, but prolonged vigorous stirring of the solutions led to a rearrangement into wormlike networks and loss of photoluminescence (PL) from the QDs. Here we report that PS317-b-P4VP76 + CdSe/ZnS core–shell QDs behave differently. Partial loss of PL intensity occurred upon addition of 2-propanol to the chloroform solution of the components, and the rearrangement to a network structure occurred spontaneously. We describe two strategies for recovery of the PL intensity for the QDs within the network, photo-activation and chemical activation with elemental sulfur.
Co-reporter:Lei Shen, Andrij Pich, Daniele Fava, Mingfeng Wang, Sandeep Kumar, Chi Wu, Gregory D. Scholes and Mitchell A. Winnik
Journal of Materials Chemistry A 2008 - vol. 18(Issue 7) pp:NaN770-770
Publication Date(Web):2008/01/15
DOI:10.1039/B713253K
We describe a new method for the preparation of fluorescent inorganic-nanoparticle composite microgels. Copolymer microgels with functional pendant groups were transferred viadialysis into tetrahydrofuran (THF) solution and mixed with colloidal solutions of semiconductor nanocrystals (quantum dots, QDs). CdSe QDs stabilized with trioctylphosphine oxide (TOPO) became incorporated into the microgels via ligand exchange of pendant imidazole (Im) groups for TOPO. PbS QDs stabilized with oleic acid were incorporated into microgels with pendant –COOH groups. This approach worked equally well with microgels based upon poly(N-isopropylacrylamide) (PNIPAM) and those based upon an acetoacetylethyl methacrylate-N-vinylcaprolactam copolymer (PVCL). These composite hybrid materials were colloidally stable in THF, and maintained their colloidal stability after transfer to water, either viadialysis or by sedimentation–redispersion. In water, the composites exhibited similar thermal responsiveness to the parent microgels, with a small shift to lower temperature in the volume phase transition. This approach allows one to use inorganic nanoparticles synthesized under optimum conditions in organic media at high temperature and to prepare composite microgels directly by mixing the components in a water-miscible organic solvent.
Co-reporter:Joe B. Gilroy ; David J. Lunn ; Sanjib K. Patra ; George R. Whittell ; Mitchell A. Winnik ;Ian Manners
Macromolecules () pp:
Publication Date(Web):July 12, 2012
DOI:10.1021/ma3008114
The solution self-assembly of block copolymers with a π-conjugated, crystalline, core-forming block represents a facile strategy toward the preparation of semiconducting nanowires with potential for high-tech applications. In this study, two asymmetric block copolymers based on regioregular poly(3-hexylthiophene) (P3HT) and poly(methyl methacrylate) (PMMA), namely P3HT40-b-PMMA520 (6a) and P3HT40-b-PMMA1100 (6b) (block ratios = 1:13 and 1:27.5, respectively) were prepared via atom transfer radical polymerization (ATRP) from a P3HT macroinitiator. The solution self-assembly of the P3HT-b-PMMA block copolymers was subsequently studied under a variety of experimental conditions. Short, fiber-like micelles resulted when THF (common solvent for P3HT and PMMA) solutions of the block copolymer were dialyzed against ethyl acetate and n-butyl acetate (selective solvents for PMMA). The electronic properties of the fiber-like micelles obtained coupled with wide-angle X-ray scattering studies confirmed that the cores of the aggregates were crystalline and suggested that growth occurs via a crystallization-driven pathway. The average lengths of fiber-like micelles were shown to increase relative to those obtained from dialysis versus the PMMA selective solvent, when THF was slowly evaporated from mixtures containing n-butyl acetate and P3HT-b-PMMA unimers, thereby limiting the rate of P3HT aggregation. Furthermore, the formation of only relatively short (mainly under 200 nm, always <1 μm) fiber-like micelles in these studies, even when the ratio of THF/alkyl acetate was controlled carefully via dialysis or evaporation, indicated that homogeneous nucleation of P3HT-b-PMMA block copolymers is relatively facile. This behavior differs significantly from that detected for other block copolymers such as polyferrocenylsilane-based materials that undergo crystallization-driven self-assembly to form cylinders with lengths of up to 10 μm under analogous conditions.
Co-reporter:Fugang Li, Mitchell A. Winnik, Anna Matvienko and Andreas Mandelis
Journal of Materials Chemistry A 2007 - vol. 17(Issue 40) pp:NaN4315-4315
Publication Date(Web):2007/08/21
DOI:10.1039/B708707A
Polypyrrole (PPy), like other conducting polymers, has a broad absorption band in the near infrared (NIR) with no evidence of fluorescence emission. We describe the preparation of PPy–EVA blends as potential hot-melt adhesives that can be activated by irradiation with NIR light. The PPy content needed to act as a thermal transducer of NIR radiation is much lower than that needed for conductivity. Blends were prepared in two ways: by blending sterically-stabilized 50 nm diameter PPy particles in water with a dispersion of 800 nm diameter ethylene–vinyl acetate copolymer (EVA) particles, and by synthesizing PPy-coated EVA core-shell particles by precipitation polymerization in water. The PPy nanoparticles and the PPy-coated EVA core-shell particles could be purified by sedimentation followed by redispersion in water to remove Fe salts. Films prepared from these particles, containing 0.1–0.5 wt% PPy, showed a strong NIR absorbance in the range of our spectrometer (700–1100 nm) with a weaker absorbance in the visible region. Photothermal radiometry (PTR) measurements indicate that these blends show good promise as potential NIR-activated adhesives, which are essentially transparent to the eye.
Co-reporter:Sebastian Berger, Olga Ornatsky, Vladimir Baranov, Mitchell A. Winnik and Andrij Pich
Journal of Materials Chemistry A 2010 - vol. 20(Issue 24) pp:NaN5150-5150
Publication Date(Web):2010/04/12
DOI:10.1039/C0JM00075B
In this article we demonstrate that hybrid nanogels can be prepared by encapsulation of reactive nanoparticles (NPs) directly during nanogel synthesis. Nanogels investigated in present study consist of poly(N-vinylcaprolactam-co-(2-acetoacetoxyethyl) methacrylate) copolymer. The modification of the LaF3:Eu nanoparticle surface with reactive double bonds allows effective incorporation of the NPs into the nanogel structure. This approach ensures effective encapsulation of varying amounts of NPs into the nanogel interior with a loading efficiency close to 95%. The NPs are covalently bound to the nanogel core, and no NP leakage occurs. Reactive NPs act as multifunctional cross-linking agents and increase the cross-linking degree of the nanogels. We demonstrate the possibility of the incorporation of LaF3 nanoparticles doped with different ions (Eu, Tb, Pr, Gd) or nanoparticle mixtures into nanogels. These nanogels exhibit temperature-sensitive properties and superior colloidal stability in water and other aqueous media.
Co-reporter:Stuart C. Thickett, Ahmed I. Abdelrahman, Olga Ornatsky, Dmitry Bandura, Vladimir Baranov and Mitchell A. Winnik
Journal of Analytical Atomic Spectrometry 2010 - vol. 25(Issue 3) pp:NaN281-281
Publication Date(Web):2009/12/24
DOI:10.1039/B916850H
We present the synthesis and characterization of monodisperse, sub-micron poly(styrene) (PS) particles loaded with up to and including 107 lanthanide (Ln) ions per particle. These particles have been synthesized by seeded emulsion polymerization with a mixture of monomer and a pre-formed Ln complex, and analyzed on a particle-by-particle basis by a unique inductively coupled plasma mass cytometer. Seed particles were prepared by surfactant-free emulsion polymerization (SFEP) to obtain large particle sizes in aqueous media. Extensive surface acid functionality was introduced using the acid-functional initiator ACVA, either during seed latex synthesis or in the second stage of polymerization. The loading of particles with three different Ln ions (Eu, Tb, and Ho) has proven to be close to 100% efficient on an individual and combined basis. Covalent attachment of metal-tagged peptides and proteins such as Neutravidin to the particle surface was shown to be successful and the number of bound species can be readily determined. We believe these particles can serve as precursors for multiplexed, bead-based bio-assays utilizing mass cytometric detection.
Co-reporter:Ahmed I. Abdelrahman, Olga Ornatsky, Dmitry Bandura, Vladimir Baranov, Robert Kinach, Sheng Dai, Stuart C. Thickett, Scott Tanner and Mitchell A. Winnik
Journal of Analytical Atomic Spectrometry 2010 - vol. 25(Issue 3) pp:NaN268-268
Publication Date(Web):2010/01/06
DOI:10.1039/B921770C
We examine the suitability of metal-containing polystyrene beads for the calibration of a mass cytometer instrument, a single particle analyser based on an inductively coupled plasma ion source and a time of flight mass spectrometer. These metal-containing beads are also verified for their use as internal standards for this instrument. These beads were synthesized by multiple-stage dispersion polymerization with acrylic acid as a comonomer. Acrylic acid acts as a ligand to anchor the metal ions within the interior of the beads. Mass cytometry enabled the bead-by-bead measurement of the metal-content and determination of the metal-content distribution. Beads synthesized by dispersion polymerization that involved three stages were shown to have narrower bead-to-bead variation in their lanthanide content than beads synthesized by 2-stage dispersion polymerization. The beads exhibited insignificant release of their lanthanide content to aqueous solutions of different pHs over a period of six months. When mixed with KG1a or U937 cell lines, metal-containing polymer beads were shown not to affect the mass cytometry response to the metal content of element-tagged antibodies specifically attached to these cells.
Co-reporter:Chun Feng, Vladimir I. Baranov and Mitchell A. Winnik
Journal of Analytical Atomic Spectrometry 2013 - vol. 28(Issue 9) pp:NaN1484-1484
Publication Date(Web):2013/07/19
DOI:10.1039/C3JA50149C
We describe the preparation of La, Tb-encoded-AuNP-coated PS microbeads via the combination of two-stage dispersion polymerization and post-functionalization of the particle surface. The introduction of La and Tb ions into the beads was achieved by the addition of LnCl3 and TbCl3 salts along with acrylic acid in the second the stage of dispersion polymerization. After the coating the surface of the beads with a silica layer containing methacrylate functional groups, a poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) layer was introduced by free radical polymerization. Subsequently, the PDMAEMA layer hosted the formation of gold nanoparticles on the surface of the beads. The formation of gold nanoparticles (AuNPs) on the surface of the beads was confirmed by dark-field transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX) and mass cytometry. Release experiments showed a negligible loss of Au ions or gold nanoparticles in 1.0% HCl aqueous solution over a two week period. The La, Tb-encoded-AuNP-coated PS beads were used to investigate the influence of plasma conditions on the thermolytic breakdown, diffusion, and matrix effects in the mass cytometer having two “thermometer” elements La (imbedded in the bulk of the bead) and Au (located on the bead surface). These experiments defined optimum conditions in terms of uniform ionization of the Au atoms present in the AuNPs. They also showed that neither the carbon-rich PS matrix nor the thin silica coating of the 1.6 μm diameter PS particles influenced the ability of the mass cytometer to determine La and Tb ion content quantitatively.
Co-reporter:David A. Rider, Mitchell A. Winnik and Ian Manners
Chemical Communications 2007(Issue 43) pp:NaN4485-4485
Publication Date(Web):2007/09/03
DOI:10.1039/B704200K
Polystyrene-block-polyferrocenylsilane (PS-b-PFS) diblock copolymers were stoichiometrically oxidized in solution using salts of the one-electron oxidant tris(4-bromophenyl)ammoniumyl. Due to a redox-induced polarity change for the PFS block, self-assembly into well-defined spherical micelles occurs. The micelles are composed of a core of partially oxidized PFS segments and a corona of PS. When the micellar solutions were treated with the reducing agent decamethylcobaltocene, the spherical micelles disassemble and regenerate unassociated and pristine PS-b-PFS free chains.
![2-Cyclopentene-1-methanol, 1-[(phenylmethoxy)methyl]-](http://img.cochemist.com/ccimg/61200/61111-55-5.png)
![2-Cyclopentene-1-methanol, 1-[(phenylmethoxy)methyl]-](http://img.cochemist.com/ccimg/61200/61111-55-5_b.png)
