Co-reporter:Youwei Zhang, Wenjuan Gu, Jiongxin Zhao, Zongyi Qin
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017 Volume 531(Volume 531) pp:
Publication Date(Web):20 October 2017
DOI:10.1016/j.colsurfa.2017.07.062
The synthesis of hydrophilic crosslinked poly(methacrylic acid) (PMAA) nanoparticles usually involves the use of organic solvents. In this study, a novel, facile and efficient route was developed for the “green” fabrication of PMAA nanoparticles in water. Crosslinked PMAA nanoparticles were prepared via simply copolymerizing MAA with crosslinker N,N′-methylenebisacrylamide in an aqueous solution of polyoxyethylene (20) sorbitan monolaurate (tween 20), sodium dodecylsulfate and 2,2′-azodiisobutyronitrile. The water-soluble PMAA chains produced in-situ are converted into water-insoluble PMAA/tween 20 complexes via hydrogen bonding interactions with tween 20. This leads to the homogenous nucleation and deposition growth of PMAA nanoparticles, thus realizing the fabrication of crosslinked PMAA nanoparticles in water. Crosslinked PMAA nanoparticles with a z-average hydrodynamic diameter in the range of 99–480 nm and a normalized swelling ratio in the range of 1.3–3.1 were obtained by varying the reaction parameters. The pH-sensitivity, biocompatibility and carboxyl functional groups make the crosslinked PMAA nanoparticles ideal candidates for various biomedical applications.Download high-res image (172KB)Download full-size image
Co-reporter:Dafu Wei, Yan Chen, Youwei Zhang
Carbohydrate Polymers 2016 Volume 136() pp:543-550
Publication Date(Web):20 January 2016
DOI:10.1016/j.carbpol.2015.09.086
•Novel antibacterial nanoparticles were prepared.•The paper coated with the nanoparticles displayed excellent antibacterial activity.•The paper coated with the nanoparticles displayed excellent washing durability.Taking advantage of the self-assembly between the components, novel stable antibacterial nanoparticles were efficiently fabricated via a facile one-step co-polymerization of acrylic acid (AA) and N,N′-methylenebisacrylamide (MBA) on a mixed aqueous solution of poly(hexamethylene guanidine hydrochloride) (PHMG) and hydroxyethylcellulose (HEC). The z-average hydrodynamic diameters of the nanoparticles ranged from 220 nm to 450 nm. The inner layer of the nanoparticles is composed of water-insoluble interpolymer complexes of PHMG and PAA networks, while the outer layer is composed of PHMG and HEC. The nanoparticles are stabilized by electrostatic interactions, hydrogen bonding interactions, and the chemical bonds. The nanoparticle solution remained stable in a wide pH range of 2.0–12.0 and at salt concentrations below 0.25 mol/L. The nanoparticles were incorporated into handsheets using a dipping treatment. The resulted handsheets exhibited excellent antimicrobial activities even after multiple water washing treatments. The nanoparticles are promising in fabricating paper, water-based coatings and textiles with permanent antibacterial activity.
Co-reporter:You-Wei Zhang, Wen-Juan Guan, Ya-Ming Lu and Jiong-Xin Zhao
RSC Advances 2016 vol. 6(Issue 71) pp:66571-66578
Publication Date(Web):12 Jul 2016
DOI:10.1039/C6RA07372G
Due to the water solubility of their component polymers, hydrophilic nano-hydrogels are usually fabricated in organic media, which causes environmental and toxicity issues. In this study, by the combined use of an ionic/nonionic surfactant mixture, a hydrophobic initiator and a poly(methyl methacrylate) (PMMA) nanolatex seed, a novel emulsion polymerization method was developed for the “green” synthesis of poly(methacrylic acid) (PMAA) nano-hydrogels in water at a high concentration (50 g L−1). The method includes two steps. First, PMMA nanolatex seeds stabilized by sodium dodecylsulfate (SDS) were formed in situ. Second, MAA was selectively polymerized on the surfaces of the PMMA nanoparticles with the help of the nonionic surfactant Tween 20, resulting in PMAA nano-hydrogels with cores of PMMA and cross-linked shells of PMAA. The core–shell structure of the PMAA nano-hydrogels was confirmed by TEM observations. The size and swelling capacity of the nano-hydrogels can be facilely adjusted: as the amount of crosslinker is decreased, the concentration of Tween 20 is increased, the concentration of MAA is increased, or MAA is fed in one batch instead of semi-continuously, both the size and swelling capacity of the nano-hydrogels increase. The PMAA nano-hydrogels also display excellent pH response: as the pH value increases from 1 to 6, the hydrodynamic volume of the hydrogels expands 64-fold. Finally, this new method is expected to be extended to the “green” synthesis of other nano-hydrogels such as poly(acrylic acid) and polyacrylamide nano-hydrogels.
Co-reporter:Youwei Zhang, Xin Zhuang, Wenjuan Gu, Jiongxin Zhao
European Polymer Journal 2015 Volume 67() pp:57-65
Publication Date(Web):June 2015
DOI:10.1016/j.eurpolymj.2015.03.057
•Semi-continuous emulsion polymerization of AN in the presence of AIBN was studied.•The AIBN amount has little influences on the size of PAN nanoparticles.•PAN nanoparticles (〈Dh〉 = 99 nm) was fabricated at [AN] = 202 g L−1 and [SDS] = 10 g L−1.Due to the large solubility of acrylonitrile (AN) monomer in water and the insolubility of polyacrylonitrile (PAN) in AN monomer, it remains a great challenge to fabricate PAN nanoparticles with sizes of below 100 nm at high monomer concentrations by emulsion polymerization methods. The synthesis of PAN nanoparticles at high monomer concentrations via a hydrophobic initiator 2,2′-azobisisobutyronitrile (AIBN)-initiated semi-continuous emulsion polymerization method was investigated. The influences of various parameters, including the initiator amount, the monomer concentration and feeding mode, the reaction temperature, the surfactant concentration and type, on the polymerization were studied. The results show that narrowly-distributed PAN nanoparticles with smaller sizes can be prepared by decreasing the monomer concentration, modestly slowing down the monomer feeding rate, decreasing the polymerization temperature, or modestly increasing the surfactant amount. The polymerization rate during the AIBN-initiated semi-continuous emulsion polymerization is kept at a very low level due to the hydrophobicity of AIBN. This endows the method with the advantage in the preparation of PAN nanoparticles at high monomer concentrations as compared with the conventional water-soluble initiator potassium persulfate (KPS)-initiated emulsion polymerization method. Narrowly-distributed PAN nanoparticles with a z-average hydrodynamic diameter around 99 nm and a polydispersity index of 0.02 was successfully fabricated at a monomer concentration as high as 202 g L−1 (based on the volume of water) and a sodium deodecylsulfate (SDS) content as low as 4.9 wt% (based on the monomer). As compared with the results of the KPS-initiated emulsion polymerization, the monomer concentration is dramatically higher, and the SDS content is much lower.Graphical abstract
Co-reporter:Youwei Zhang, Yaqin He, Jiongxin Zhao
European Polymer Journal 2014 Volume 61() pp:316-325
Publication Date(Web):December 2014
DOI:10.1016/j.eurpolymj.2014.11.004
•Semi-continuous emulsion polymerization of MMA in the presence of AIBN was studied.•The AIBN amount has little influences on the size of PMMA nanoparticles.•PMMA nanolatex (〈Dh〉 = 77 nm) was fabricated at [MMA] = 315 g L−1 and [SDS] = 1.67 g L−1.•PMMA nanolatex particles remain stable at a surface coverage ratio as low as 0.084.By a combined use of oil-soluble initiators and the semi-continuous monomer feeding, a modified emulsion polymerization method was developed for the synthesis of poly(methyl methacrylate) (PMMA) nanolatexes at high monomer concentrations. The influences of various parameters on the polymerization were studied, including the monomer feeding rate, the surfactant concentration, the initiator amount, and the monomer concentration. Narrowly-distributed PMMA nanolatex particles with smaller sizes can be prepared by slowing down the monomer feeding rate, modestly increasing the surfactant concentration, or decreasing the monomer concentration. The molecular weight of PMMA nanolatex particles increases with the monomer feeding rate and the monomer concentration. Most importantly, PMMA nanoparticles with a z-average hydrodynamic diameter of 77 nm, a polydispersity index of 0.07, and a number-average molecular weight of 3.96 × 106 g mol−1 was fabricated at a monomer concentration as high as 315 mg mL−1 and a surfactant concentration as low as 1.67 mg mL−1. The surface coverage ratio of the nanolatex particles is decreased down to a surprising low value of 0.084. This can be attributed to the slow polymerization rate of the modified emulsion polymerization as well as the interactions between the polar ester groups of PMMA and water.
Co-reporter:Dafu Wei;Rihui Zhou;Yong Guan;Anna Zheng
Journal of Applied Polymer Science 2013 Volume 127( Issue 1) pp:666-674
Publication Date(Web):
DOI:10.1002/app.37849
Abstract
Polyhexamethylene guanidine hydrochloride (PHMG) oligomer is attracting increasing attention for its highly efficient biocidal activity and nontoxicity. To make it bearing carbon-to-carbon double bonds and enlarge its application in production of antimicrobial materials via copolymerization, PHMG oligomer was modified via reaction with glycidyl methacrylate (GMA). The influence of reaction parameters on the conversion rate of GMA was investigated using ultraviolet absorption spectroscopy. The structures of PHMG oligomer before and after modification were characterized by Fourier transform infrared spectrometry, Raman spectrometry, nuclear magnetic resonance spectrometry, and electrospray ionization time-of-flight mass spectrometry. The results show that carbon-to-carbon double bond is successfully introduced into the modified PHMG oligomer. At a feeding molar ratio of GMA to PHMG of 1.0, the conversion rate of GMA reached up to 75% after 60 h of reaction at 60°C in dimethyl sulfoxide. Also, there is an activity difference in the different aminos of PHMG oligomer: the primary amino is ready to react with epoxy of GMA, while the guanidyl amino hardly reacts with GMA due to the p-π conjugation. Furthermore, the modified PHMG oligomer was used as comonomer to synthesize acrylonitrile copolymer, showing excellent antimicrobial activity against Staphylococcus aureus. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Da-Fu Wei;Ri-Hui Zhou;You-Wei Zhang;Yong Guan;An-Na Zheng
Journal of Applied Polymer Science 2013 Volume 130( Issue 1) pp:419-425
Publication Date(Web):
DOI:10.1002/app.39163
Abstract
Nonleaching acrylic fibers with permanent antibacterial activity were prepared via a combination of copolymerization and a wet-blend-spinning method. Specifically, poly[acrylonitrile-co-modified poly(hexamethylene guanidine hydrochloride)] [poly(AN-co-M-PHMG)] copolymers containing a covalently connected antibacterial guanidine oligomer were first synthesized via the precipitation copolymerization of acrylonitrile (AN) with a modified poly(hexamethylene guanidine hydrochloride) (M-PHMG) macromonomer in water. Then, modified acrylic fibers were prepared from a mixture of the copolymer and commercial fiber-grade AN terpolymer via a wet-spinning process with dimethyl sulfoxide as the solvent. The influences of the reaction time, temperature, pH value of the medium, and amount of initiator on the copolymerization and the effect of the copolymer content on the mechanical properties and antibacterial activity of the modified acrylic fibers were investigated in detail. The results show that the M-PHMG macromonomer exhibited a lower reactivity than AN. The poly(AN-co-M-PHMG) copolymer with a PHMG content of 5.49% and an intrinsic viscosity of 11.2 dL/g could be synthesized under optimized conditions. With increasing copolymer content, the tensile strength of the modified acrylic fibers decreased slightly, and the antibacterial activity increased. The modified acrylic fibers with a copolymer content of 50% (i.e., a PHMG content of 2.75%) exhibited both good mechanical properties and excellent antibacterial activity. The additional antibacterial function would surely enlarge the applications of the fiber. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Y. Zhang;Q. Wu;H. Zhang;J. Zhao
Journal of Nanoparticle Research 2013 Volume 15( Issue 7) pp:
Publication Date(Web):2013 July
DOI:10.1007/s11051-013-1800-5
Crosslinked polyacrylonitrile (PAN) nanolatex, with an average hydrodynamic diameter of 84 nm and a polydispersity index of 0.06, was successfully synthesized at a high monomer concentration and low surfactant content via a modified emulsion polymerization. Three measurements were adopted to control the nucleation and growth processes. Taking advantage of the chemical activity of nitrile groups, intelligent hydrophilic polymeric nanoparticles were fabricated via simple alkaline hydrolysis treatment of the crosslinked PAN nanolatex. Dynamic light scattering, electrophoretic light scattering, FT-IR spectroscopy, elemental analysis, and TEM observations were used to monitor the changes in the composition, structure, and morphology of the nanoparticles during the hydrolysis process. The sizes, chemical composition, morphology, and pH-responsive behavior of the intelligent hydrophilic nanoparticles could be adjusted by simply changing the hydrolysis time. As the hydrolysis was prolonged, the following nanoparticles could be obtained, crosslinked PAN nanoparticles with hydrophilic surfaces, amphiphilic nanoparticles with a hydrophobic PAN core and a hydrophilic polymeric shell composed of acrylamide and acrylic acid units, or carboxylic polyacrylamide nanoparticles. These modified nanoparticles all display good hydrophilicity, good biocompatibility, pH-sensitivity, as well as carboxyl functional groups, and thus are ideal candidates for various biomedical applications.
Co-reporter:Jian Zhang;Degang Zhang ;Jiongxin Zhao
Journal of Applied Polymer Science 2012 Volume 125( Issue S1) pp:E58-E66
Publication Date(Web):
DOI:10.1002/app.36317
Abstract
To produce polyacrylonirtile (PAN) fiber precursor with desired cross-section shape, microstructure and mechanical properties, several measurements including adopting DMSO/water (95/5, v/v) mixture as the solvent of the spinning dope, ethanol/DMSO (60/40, v/v) mixture at 10°C as the coagulation medium, and modified multi-walled carbon nanotube (MWCNT) as the reinforcing nanofiller, as well as extra-drawing the as-spun fiber in air, were taken in the preparation of PAN fibers via dry-jet wet spinning. The morphology, structure, and properties, thermal behavior of the resultant fibers were studied. The results show that gel fibers with homogeneous dense structure and circular cross-section were obtained. High orientation of PAN molecules in fiber was achieved by additional drawing the as-spun fiber in air. After the introduction of a very small amount of modified MWCNT, the tensile strength and modulus of the fiber enhance substantially: there is a 19% increase in strength and a 62% increase in modulus at a MWCNT content of 1.0 wt %. Also, the heat release rate decreases during the oxidative stabilization. The uniform microstructure, circular cross-section, high orientation of PAN molecules, high tensile strength and modulus, as well as the gentle oxidative cyclization behavior, make the PAN/MWCNT composite fiber an attractive precursor candidate for carbon fiber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Jian Zhang;Jiongxin Zhao
Polymer Bulletin 2011 Volume 67( Issue 6) pp:
Publication Date(Web):2011 September
DOI:10.1007/s00289-011-0525-9
In order to investigate the effects of the non-solvent species on the formation mechanism of polyacrylonitrile (PAN) fiber in wet spinning, theoretical ternary phase diagrams of water/DMSO/PAN and ethanol/DMSO/PAN systems were constructed based on the extended Flory–Huggins theory. The cloud-points of dilute PAN solutions of the two systems were determined by titration method and those of concentrated PAN solutions from Boom’s linearized cloud-point correlation. Binary interaction parameters were calculated and optimized to construct the theoretical phase diagram. The obtained diagrams were used to investigate the effects of the non-solvent species on the formation of PAN fibers. If the non-solvent water is replaced with ethanol, the meta-stable two-phase region in the ternary phase diagram increases. This favors the de-mixing of the filament via nucleation and growth mechanism during the coagulation process, resulting in homogenous dense PAN fibers with low porosity.
Co-reporter:Youwei Zhang, Qiaorong Jin, Jiongxin Zhao, Chengxun Wu, Qingqing Fan, Qimin Wu
European Polymer Journal 2010 Volume 46(Issue 7) pp:1425-1435
Publication Date(Web):July 2010
DOI:10.1016/j.eurpolymj.2010.04.023
Taking advantage of the specific hydrogen bonding interactions between the components, core–shell nanoparticles based on poly(methacrylic acid) (PMAA) and hydroxyethyl cellulose (HEC) can be efficiently prepared via facile one-step polymerization of MAA on HEC template in water. Various techniques were used to characterize in detail the sizes, morphology, and structures of the nanoparticles, as well as the interactions between the components. The core–shell structures of the nanoparticles were confirmed by TEM observation. Dynamic light scattering and fluorescence spectrometry were used to monitor the polymerization process, which indicates a size decrease and a hydrophobicity increase of the nanoparticles. A mechanism was proposed to explain the formation of core–shell nanoparticles during the template polymerization. The obtained nanoparticles are stable against urea, salt, temperature and in the storage; meanwhile, they exhibit pH-response: the volume of the nanoparticles increased more than six times as pH value of the medium increased from 2.8 to 3.7.Driven by the specific hydrogen bonding interactions, PMAA chains synthesized in situ during the template polymerization self-assemble with HEC template macromolecules, resulting in well-defined nanoparticles with cores of PMAA/HEC inter-polymer complexes and shells of HEC.
Co-reporter:Yansong Wang, Youwei Zhang, Weiping Du, Chengxun Wu, Jiongxin Zhao
Journal of Colloid and Interface Science 2009 Volume 334(Issue 2) pp:153-160
Publication Date(Web):15 June 2009
DOI:10.1016/j.jcis.2009.02.063
PAA/gelatin nanoparticles, with interpolymer complexes of gelatin and polyacrylic acid (PAA) as the cores and gelatin as the shells, were prepared via facile polymerization of AA on gelatin template. The morphology change of the nanoparticles during the reaction was traced by a combined use of dynamic light scattering (DLS) and atomic force microscopy (AFM) techniques, which revealed a discrepancy among the structure of the nanoparticles formed at different stages of the reaction: as the reaction proceeds, nanoparticles with larger compact cores and thinner shells are produced. The resultant nanoparticles are multi-responsive. Especially, they exhibit a significant temperature-dependent size change: upon raising the temperature from 25 °C, the nanoparticle size decreases monotonically until reaching equilibrium at about 40 °C. This temperature-dependence of the nanoparticle size was found to be reversible provided the nanoparticle solution was cooled at a low temperature (4 °C). The thermo-sensitivity of the nanoparticles is attributed to the thermo-induced sol–gel transition of the gelatin shells. In addition, the nanoparticles were further converted to hollow spheres via successive locking the shell structure by the reaction of gelatin with cross-linker glutaraldehyde, and cavitation of the cross-linked nanoparticles by switching the medium from acidic to neutral. The cavitation process was monitored by DLS, which indicated a mass decrease and size shrinkage. AFM and transmission electron microscopy (TEM) were used to trace the morphology change of the nanoparticles during the cavitation. The hollow structure was confirmed by TEM observation.Core-shell nanoparticles are prepared by polymerization of AA in a gelatin aqueous solution, followed by successive selective cross-linking and core cavitation to obtain hollow spheres.
Co-reporter:Youwei Zhang, Ming Jiang, Jiongxin Zhao, Daoyong Chen
European Polymer Journal 2007 Volume 43(Issue 12) pp:4905-4915
Publication Date(Web):December 2007
DOI:10.1016/j.eurpolymj.2007.09.008
Using fluorescence spectrometry, it was found pyrene begins to partition into the core of poly(ε-caprolactone)/poly(N-isopropylacrylamide) (PCL/PNIPAM) core–shell nanoparticles at a low nanoparticle concentration (0.001 mg/mL). The partition coefficient for pyrene partitioning between water and the nanoparticles is around 104. The rate for pyrene partitioning into PCL core is very quick, depending on the relative PCL core weight. And the distinct on–off property of the nanoparticle with temperature was revealed: pyrene molecules enter into PCL core freely when temperature is less than 34 °C; while it becomes difficult when temperature rises to 37 °C. In addition, a new procedure to accurately determine the loading capacity of nanoparticle core for hydrophobic compound using UV–vis spectrometry was developed.
Co-reporter:Youwei Zhang;Jiongxin Zhao;Ming Jiang;Jiaye Wang
Frontiers of Chemistry in China 2007 Volume 2( Issue 3) pp:287-291
Publication Date(Web):2007 July
DOI:10.1007/s11458-007-0052-2
According to the new method of preparing core-shell nanospheres developed by our group, by using two monomers, 2-hydroxypropyl methacrylate(HPMA) and vinyl acetate(VAc), two kinds of core-shell nanospheres with poly(ɛ-caprolactone) (PCL) as the core and crosslinked poly(2-hydroxypropyl methacrylate) (PHPMA) or poly(vinyl acetate) (PVAc) as the shell were successfully prepared under similar conditions. After degrading the PCL cores of the two kinds of nanospheres by lipase, the corresponding crosslinked poly(methyl acrylic acid) hollow spheres and crosslinked poly(vinyl alcohol) hollow spheres were obtained. Results indicate that the new method we proposed for preparing core-shell polymeric nanospheres via in-situ polymerization can be generalized to a certain extent, and it is suitable for many systems provided the monomer used is soluble in water, while its corresponding polymer is insoluble in water.
