Co-reporter:Zhenhua Wang, Xiangcheng Pan, Lingchun Li, Marco Fantin, Jiajun Yan, Zongyu Wang, Zhanhua Wang, Hesheng Xia, and Krzysztof Matyjaszewski
Macromolecules October 24, 2017 Volume 50(Issue 20) pp:7940-7940
Publication Date(Web):October 4, 2017
DOI:10.1021/acs.macromol.7b01597
A robust mechanically controlled atom transfer radical polymerization (mechano-ATRP) was developed by enhancing the interaction between piezoelectric nanoparticles and ATRP Cu catalysts. The interactions favor a mechano-induced electron transfer from the surface of the nanoparticles to the deactivator CuII/L complex under ultrasonic agitation, promoting the formation of the activator CuI/L complex, thereby increasing the rate of the polymerization. This mechano-ATRP was carried out with a low loading of zinc oxide nanoparticles, providing a polymer with high end-group fidelity, predetermined molecular weight, and low dispersity. Propagation of the polymer chains was switched on/off in response to the ultrasound. The effects of the nature of the nanoparticle, nanoparticle loading, and targeted degrees of polymerization were investigated to evaluate the mechanism of mechano-ATRP.
Co-reporter:Zhenhua Wang, Xiangcheng Pan, Lingchun Li, Marco Fantin, Jiajun Yan, Zongyu Wang, Zhanhua Wang, Hesheng Xia, and Krzysztof Matyjaszewski
Macromolecules October 24, 2017 Volume 50(Issue 20) pp:7940-7940
Publication Date(Web):October 4, 2017
DOI:10.1021/acs.macromol.7b01597
A robust mechanically controlled atom transfer radical polymerization (mechano-ATRP) was developed by enhancing the interaction between piezoelectric nanoparticles and ATRP Cu catalysts. The interactions favor a mechano-induced electron transfer from the surface of the nanoparticles to the deactivator CuII/L complex under ultrasonic agitation, promoting the formation of the activator CuI/L complex, thereby increasing the rate of the polymerization. This mechano-ATRP was carried out with a low loading of zinc oxide nanoparticles, providing a polymer with high end-group fidelity, predetermined molecular weight, and low dispersity. Propagation of the polymer chains was switched on/off in response to the ultrasound. The effects of the nature of the nanoparticle, nanoparticle loading, and targeted degrees of polymerization were investigated to evaluate the mechanism of mechano-ATRP.
Co-reporter:Fangfang He, Giuseppe Mensitieri, Marino Lavorgna, Martina Salzano de Luna, Giovanni Filippone, Hesheng Xia, Rosario Esposito, Giuseppe Scherillo
Composites Part B: Engineering 2017 Volume 116(Volume 116) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.compositesb.2016.10.076
The spatial distribution of graphene oxide (GO) nanoplatelets in a bromobutyl rubber (BBR) matrix has been tailored by exploiting the rubber latex mixing process to confine nanoparticles among latex microspheres, thus obtaining a segregated arrangement. The gas transport properties and the dielectric behavior of these nanocomposites displaying a ‘segregated’ morphology have been compared, for different filler contents, to those of BBR/GO nanocomposites in which the nanoparticles are uniformly dispersed within the rubber matrix. Relevant qualitative and quantitative differences emerge from the comparison of the properties of the two families of GO-based samples. It has been found that the segregated morphology enables a significant enhancement of the barrier properties of pristine rubber already at low levels of nanofiller loading. In addition, an exceptionally low value of the electrical percolation threshold has been detected, which is more than one order of magnitude lower than in the case of uniform filler dispersion. These effects are a direct consequence of the assembly and confinement of nanoparticles among the rubber latex microspheres.Download high-res image (158KB)Download full-size image
Co-reporter:Xili Lu;Shengwei Guo;Xia Tong;Yue Zhao
Advanced Materials 2017 Volume 29(Issue 28) pp:
Publication Date(Web):2017/07/01
DOI:10.1002/adma.201606467
A new strategy for enhancing the photoinduced mechanical force is demonstrated using a reprocessable azobenzene-containing liquid crystalline network (LCN). The basic idea is to store mechanical strain energy in the polymer beforehand so that UV light can then be used to generate a mechanical force not only from the direct light to mechanical energy conversion upon the trans–cis photoisomerization of azobenzene mesogens but also from the light-triggered release of the prestored strain energy. It is shown that the two mechanisms can add up to result in unprecedented photoindued mechanical force. Together with the malleability of the polymer stemming from the use of dynamic covalent bonds for chain crosslinking, large-size polymer photoactuators in the form of wheels or spring-like “motors” can be constructed, and, by adjusting the amount of prestored strain energy in the polymer, a variety of robust, light-driven motions with tunable rolling or moving direction and speed can be achieved. The approach of prestoring a controllable amount of strain energy to obtain a strong and tunable photoinduced mechanical force in azobenzene LCN can be further explored for applications of light-driven polymer actuators.
Co-reporter:Guoxia Fei, Qichun Gong, Dongxu Li, Marino Lavorgna, Hesheng Xia
Composites Science and Technology 2017 Volume 146(Volume 146) pp:
Publication Date(Web):7 July 2017
DOI:10.1016/j.compscitech.2017.04.020
The effect of both thermal annealing and plasticization of the polymeric matrix by low molecular weight compounds on the electrical conductivity of the polystyrene based carbon nanotubes (CNTs) composites were investigated. It was found that the electrical conductivity of the samples filled with 3 wt% of CNTs increased by nearly 2 orders of magnitude after thermal annealing for 10 h at 150 °C, and it further increased with increasing plasticizer content. The effect of the hierarchical CNT morphology on the electrical conductivity of composites was elucidated by in-situ Raman and Synchrotron Radiation Small Angle X-ray Scattering investigations. The synergistic effect between thermal treatment and matrix plasticization contributes to efficiently eliminate the residual stress at the interface between polymeric matrix and carbon nanotubes. This leads to the formation of a more effective CNTs network featured by more dense bundles, exhibiting a larger number of contacts between the CNTs which contributes to significantly enhance the electrical conductivity of composites.Download high-res image (113KB)Download full-size image
Co-reporter:Shuchi Liao, Tianliang Zhai and Hesheng Xia
Journal of Materials Chemistry A 2016 vol. 4(Issue 3) pp:1068-1077
Publication Date(Web):08 Dec 2015
DOI:10.1039/C5TA09540A
The graphene oxide aerogel microspheres were prepared by a novel approach, i.e. a combination of electrospraying and freeze-casting. The unique well-defined “center-diverging microchannel” dandelion-like structures were observed in the aerogel microspheres and a formation mechanism of the structure, i.e. radial-directional freezing–thawing, was proposed. After further thermal reduction, the reduced graphene oxide aerogel microspheres were obtained and the center-diverging microchannel structures can be remained. Due to their highly porous, hierarchical and hydrophobic structure as well as a random packing effect, the aerogel microspheres possess excellent adsorption ability for various organic solvents and oils, showing their potential applications in environmental pollutant treatment.
Co-reporter:Guo Li, Hu Zhang, Daniel Fortin, Weizheng Fan, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2016 vol. 4(Issue 25) pp:5932-5939
Publication Date(Web):24 May 2016
DOI:10.1039/C6TC01377E
A photoresponsive shape memory composite material with room temperature programmability is reported in this paper. The material is composed of poly(styrene-b-ethylene-co-butadiene-b-styrene) (SEBS: a thermoplastic elastomer), paraffin wax (PW: a mixture of short hydrocarbon chains with a melting point around 60 °C) and gold nanoparticles (AuNPs). On one hand, the SEBS/PW system is room temperature programmable, meaning that the temporary shape can be processed by directly deforming the material into a desired shape at room temperature. Particularly interesting is that the fixed deformation is not limited to elongation or compression, but includes other types of deformation like twisting and bending. This attribute makes three-dimensional shape processing doable under ambient conditions without heating or cooling. The results of wide-angle X-ray diffraction measurements on elongated SEBS/PW samples suggest that the stretching-induced orientation and reorganization of PW crystals could form a solid skeleton to sustain the elastic extension of the rubbery EB chains, resulting in the apparent plastic deformation. On the other hand, by loading a small amount of AuNPs (0.18 wt%) in the composite material, the shape recovery, which occurs upon melting of PW crystals, becomes controllable using visible light based on the photothermal effect arising from the surface plasmon resonance of AuNPs. Thanks to the ability of remote activation and spatiotemporal control, a potential application of photoresponsive shape memory materials with room temperature programmability is demonstrated using SEBS/PW/AuNP: damage inflicted on an object or a product in the form of mechanical deformation or shape distortion can be conveniently and effectively repaired using a visible light laser (532 nm) at room temperature.
Co-reporter:Jian Zhao, Rui Xu, Gaoxing Luo, Jun Wu and Hesheng Xia
Journal of Materials Chemistry A 2016 vol. 4(Issue 5) pp:982-989
Publication Date(Web):11 Dec 2015
DOI:10.1039/C5TB02036K
The thermally healable polysiloxane elastomers were successfully prepared by cross-linking polydimethylsiloxane bearing maleimide pendants with furan-end functionalized siloxane via the Diels–Alder (DA) reaction. The elastomers with good mechanical properties show excellent self-healing and remoldability functions due to the thermally reversible feature of the DA reaction. The molecular mechanism of self-healing was confirmed by in situ structural characterization. Moreover, the biocompatibility of the polysiloxane elastomer containing DA bonds is found to be fairly good by cytotoxicity evaluation and animal subcutaneous experiments, suggesting its potential applications in the biomedical field as artificial skin and scaffolds for tissue engineering.
Co-reporter:Ning Yan, Filomena Capezzuto, Marino Lavorgna, Giovanna G. Buonocore, Fabiana Tescione, Hesheng Xia and Luigi Ambrosio
Nanoscale 2016 vol. 8(Issue 20) pp:10783-10791
Publication Date(Web):21 Apr 2016
DOI:10.1039/C6NR00377J
Chitosan (CS) is one of the most promising polymers due to its biocompatibility, biodegradability, and natural abundance. However, its poor mechanical and barrier properties make it difficult to satisfy a wide range of applications. Herein, borate ions, originating from the hydrolysis of sodium tetraborate decahydrate (borax), have been used to crosslink chitosan and graphene oxide (GO) nanocomposites. Chitosan films consisting of 1.0 wt% boron and 1.0 wt% GO exhibit a significant improvement in both the toughness and oxygen barrier properties compared to pristine chitosan. In particular the tensile strength of the samples after thermal treatment increases by ∼160% compared to pristine chitosan, whereas their oxygen permeability reduces by ∼90%. This is ascribed to the chemical crosslinking between chitosan and GO nanoplatelets through borate ions, as well as the formation of a layered morphology with graphene nanoplatelets oriented parallel to the sample surface. The exceptional robust and high gas barrier film has promising application in the packaging industry. The borate-crosslinking chemistry represents the potential strategy for improving properties of other polymer nanocomposites.
Co-reporter:Tianliang Zhai, Qifeng Zheng, Zhiyong Cai, Hesheng Xia, Shaoqin Gong
Carbohydrate Polymers 2016 Volume 148() pp:300-308
Publication Date(Web):5 September 2016
DOI:10.1016/j.carbpol.2016.04.065
•Cellulose based aerogel microspheres were successfully prepared via a combination of the water-in-oil (W/O) emulsification process with the freeze-drying process.•The superhydrophobic modification of the cellulose based aerogel microspheres were achieved via a thermal chemical vapor deposition method.•The crude oil absorption and organic solvent uptake capacity of the resulting aerogel microspheres was up to 116 times and 140 times of their own weight, respectively.Superhydrophobic and crosslinked poly(vinyl alcohol) (PVA)/cellulose nanofibril (CNF) aerogel microspheres were prepared via a combination of the water-in-oil (W/O) emulsification process with the freeze-drying process, followed by thermal chemical vapor deposition of methyltrichlorosilane. The oil phase and the cooling agent were judiciously selected to ensure that the frozen ice microspheres can be easily separated from the emulsion system. The silanized microspheres were highly porous with a bulk density ranging from 4.66 to 16.54 mg/cm3. The effects of the solution pH, stirring rate, and emulsifier concentration on the morphology and microstructure of the aerogel microspheres were studied. The highly porous structure of the ultralight aerogel microspheres demonstrated an ultrahigh crude oil absorption capacity (up to 116 times its own weight). This study provides a novel approach for the large-scale preparation of polymeric aerogel microspheres with well-controlled particle sizes that can be used for various applications including oil and chemical spill/leak clean-up.
Co-reporter:Qiang Bu;Yanhu Zhan;Fangfang He;Marino Lavorgna
Journal of Applied Polymer Science 2016 Volume 133( Issue 15) pp:
Publication Date(Web):
DOI:10.1002/app.43243
ABSTRACT
Stretchable conductive films consisting of a layer of carbon nanomaterials, that is, carbon nanotubes (CNTs), mechanically exfoliated graphene (GE), or chemically reduced graphene oxide (rGO), deposited on polydimethylsiloxane (PDMS) films were prepared by spray coating. The correlations among the concentration of the carbon nanomaterials, the electrical resistance and the optical transmittance of the spray-coated films were investigated. The results show that the conductivity of the CNT coatings was better than that of the GE-based coatings. When the CNT concentration of the dispersion for spraying increased from 0.01 to 0.075 mg/mL, the surface electrical resistance decreased from 7.8 × 103 to 6.7 × 102 Ω, whereas for the GE or rGO coatings, the electrical resistance was several orders higher than that of the CNT coatings. The CNT spray-coated films exhibited an optical transmittance of about 60% at a wavelength of 550 nm; this was higher than that of the GE or rGO spray-coated films. The electric heating behaviors of the stretchable conductive films as functions of the applied voltage and the concentration of carbon nanomaterials and the electrical conductivity under tensile and bending strains were also investigated. The surface temperature of the CNT-coated films rose rapidly up to 200°C within about 40 s when the applied voltage was 110 V. The stretchable conductive films have potential as electric heating elements because of their excellent conductive properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43243.
Co-reporter:Fayong Li, Chuan Xie, Zhengang Cheng, Hesheng Xia
Ultrasonics Sonochemistry 2016 30() pp: 9-17
Publication Date(Web):May 2016
DOI:10.1016/j.ultsonch.2015.11.023
Co-reporter:Ning Yan, Filomena Capezzuto, Giovanna G. Buonocore, Marino Lavorgna, Hesheng Xia, and Luigi Ambrosio
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 40) pp:22678
Publication Date(Web):September 25, 2015
DOI:10.1021/acsami.5b07529
Gas-barrier materials obtained by coating poly(ethylene terephthalate) (PET) substrates have already been studied in the recent literature. However, because of the benefits of using cheaper, biodegradable, and nonpolar polymers, multilayered hybrid coatings consisting of alternate layers of reduced graphene oxide (rGO) nanosheets and a novel high amorphous vinyl alcohol (HAVOH) with zirconium (Zr) adducts as binders were successfully fabricated through a layer-by-layer (LbL) assembly approach. Atomic force microscopy analysis showed that rGO nanoplatelets were uniformly dispersed over the HAVOH polymer substrate. Scanning and transmission electron microscopies revealed that multilayer (HAVOH/Zr/rGO)n hybrid coatings exhibited a brick-wall structure with HAVOH and rGO as buildings blocks. It has been shown that 40 layers of HAVOH/Zr/rGO ultrathin films deposited on PET substrates lead to a decrease of 1 order of magnitude of oxygen permeability with respect to the pristine PET substrate. This is attributed to the effect of zirconium polymeric adducts, which enhance the assembling efficiency of rGO and compact the layers, as confirmed by NMR characterization, resulting in a significant increment of the oxygen-transport pathways. Because of their high barrier properties and high flexibility, these films are promising candidates in a variety of applications such as packaging, selective gas films, and protection of flexible electronics.Keywords: barrier properties; high amorphous poly(vinyl alcohol); layer-by-layer assembly; polymeric zirconium adducts; reduced graphene oxide
Co-reporter:Tianliang Zhai, Qifeng Zheng, Zhiyong Cai, Lih-Sheng Turng, Hesheng Xia, and Shaoqin Gong
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 13) pp:7436
Publication Date(Web):March 30, 2015
DOI:10.1021/acsami.5b01679
Superhydrophobic poly(vinyl alcohol) (PVA)/cellulose nanofibril (CNF) aerogels with a unidirectionally aligned microtubular porous structure were prepared using a unidirectional freeze-drying process, followed by the thermal chemical vapor deposition of methyltrichlorosilane. The silanized aerogels were characterized using various techniques including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and contact angle measurements. The structure of the aerogels fully filled with polydimethylsiloxane (PDMS) was confirmed by SEM and optical microscopy. The mechanical properties of the resulting PDMS/aerogel composites were examined using both compressive and tensile tests. The compressive and tensile Young’s moduli of the fully filled PDMS/aerogel composites were more than 2-fold and 15-fold higher than those of pure PDMS. This study provides a novel alternative approach for preparing high performance polymer nanocomposites with a bicontinuous structure.Keywords: cellulose nanofibrils (CNFs); mechanical properties; organic aerogels; polydimethylsiloxane; unidirectional freeze-drying
Co-reporter:Guo Li, Qiang Yan, Hesheng Xia, and Yue Zhao
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 22) pp:12067
Publication Date(Web):May 18, 2015
DOI:10.1021/acsami.5b02234
Therapeutic-ultrasound-triggered shape memory was demonstrated for the first time with a melamine-enhanced poly(vinyl alcohol) (PVA) physical hydrogel. The addition of a small amount of melamine (up to 1.5 wt %) in PVA results in a strong hydrogel due to the multiple H-bonding between the two constituents. A temporary shape of the hydrogel can be obtained by deformation of the hydrogel (∼65 wt % water) at room temperature, followed by fixation of the deformation by freezing/thawing the hydrogel under strain, which induces crystallization of PVA. We show that the ultrasound delivered by a commercially available device designed for the patient’s pain relief could trigger the shape recovery process as a result of ultrasound-induced local heating in the hydrogel that melts the crystallized PVA cross-linking. This hydrogel is thus interesting for potential applications because it combines many desirable properties, being mechanically strong, biocompatible, and self-healable and displaying the shape memory capability triggered by a physiological stimulus.Keywords: melamine; physical hydrogel; shape memory polymer; stimulus-responsive polymer; ultrasound trigger;
Co-reporter:Dongxu Li;Guoxia Fei;Paul E. Spencer;Philip D. Coates
Journal of Applied Polymer Science 2015 Volume 132( Issue 33) pp:
Publication Date(Web):
DOI:10.1002/app.42416
ABSTRACT
Thermoplastic polyurethane (TPU)/multi-walled carbon nanotubes (CNT) nanocomposites were prepared by twin-screw extrusion and micro injection molding. The electrical conductivity of micro injection molded polymer nanocomposites exhibits a low value and uneven distribution in the micromolded samples. Real-time tracing of electrical conductivity was conducted to investigate the post thermal treatment on the electrical conductivity of microinjection molded composites. The results show that postmolding thermal treatment leads to a significant increase in the electrical conductivity by over three orders of magnitude for 5 wt % CNT-filled TPU composites. In-situ Transmission electron microscopy confirms the conductive CNT network does not change at the micron/sub-micron scale during thermal treatment. TEM image analysis by a statistical method was used to determine the spatial distribution of CNT in the sample and showed that the average distance between adjacent CNT reduced slightly at the nanometer scale after postmolding thermal treatment. A new conductive mechanism is proposed to explain the enhancement of electrical conductivity after thermal treatment, i.e. micro-contact reconstruction of adjacent CNT in the polymer matrix through annealing-induced relaxation of interfacial residual stress and strain. Raman spectra and small angle X-ray scattering curve of annealed samples provide supporting evidence for the proposed new conductive mechanism. The electron tunneling model was used to understand the effect of inter-particle distance on the conductivity of polymer composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42416.
Co-reporter:Guo Li, Hongji Zhang, Daniel Fortin, Hesheng Xia, and Yue Zhao
Langmuir 2015 Volume 31(Issue 42) pp:11709-11716
Publication Date(Web):October 6, 2015
DOI:10.1021/acs.langmuir.5b03474
A double-network polymer hydrogel composed of chemically cross-linked poly(ethylene glycol) (PEG) and physically cross-linked poly(vinyl alcohol) (PVA) was prepared. When the hydrogel (70 wt % of water) is subjected to freezing/thawing treatment under strain, the enhanced physical network as a result of crystallization of PVA chains can stabilize the hydrogel deformation after removal of the external force at room temperature. Subsequent disruption of the physical network of PVA by heating allows for the recovery of the initial shape of the hydrogel. Moreover, the double-network hydrogel exhibits self-healing capability stemming from the physical network of PVA by virtue of the extensive interchain hydrogen bonding between the hydroxyl side groups. This study thus demonstrates a general approach to imparting both the shape memory and self-healing properties to chemically cross-linked hydrogels that otherwise do not have such functionalities. Moreover, by making use of the fixed hydrogel elongation, the effect of anisotropy arising from chain orientation on the self-healing was also observed.
Co-reporter:Hongji Zhang, Dehui Han, Qiang Yan, Daniel Fortin, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2014 vol. 2(Issue 33) pp:13373-13379
Publication Date(Web):11 Jun 2014
DOI:10.1039/C4TA02463J
A general method for preparing mechanically strong hydrogels that can undergo light-triggered healing was demonstrated. By loading a small amount of gold nanoparticles (AuNPs, 0.05 wt%) in hydrogels prepared with stearyl acrylate (SA), N,N-dimethylacrylamide (DMA) and N,N′-methylenebisacrylamide (MBA), whose strength is endowed by chemical crosslinking coexisting with crystallized hydrophobic SA side chains acting as the physical crosslinks, exposing a cut-through damage to a laser of wavelength at the surface plasmon resonance of AuNPs and subsequently turning off the light, gives rise to efficient healing of the hydrogel as a result of the reversible melting–crystallization phase transition of the hydrophobically associated SA chains. A hydrogel of this kind exhibits an unprecedented tensile strength, after repairing, of greater than 2 MPa. It also displays a light-controllable shape memory effect.
Co-reporter:Xili Lu, Guoxia Fei, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2014 vol. 2(Issue 38) pp:16051-16060
Publication Date(Web):04 Aug 2014
DOI:10.1039/C4TA02726D
The concept of using ultrasound to trigger shape memory assisted healing of covalently cross-linked dynamic polymers is demonstrated. The well-designed dynamically crosslinked poly(ε-caprolactone)-based polyurethane bearing Diels–Alder bonds not only possesses high mechanical strength and toughness, but also exhibits shape memory assisted crack-closure and healing upon exposure to high-intensity focused ultrasound owing to breaking and reformation of dynamic bonds. The use of focused ultrasound allows the healing process to be activated remotely and to be controlled locally by depositing the acoustic energy only in the damaged region without detriment to the undamaged parts of the material. The healable polyurethane materials have potential applications such as long-term load-bearing engineering components and anti-fatigue medical devices.
Co-reporter:Giuseppe Scherillo, Marino Lavorgna, Giovanna G. Buonocore, Yanhu H. Zhan, Hesheng S. Xia, Giuseppe Mensitieri, and Luigi Ambrosio
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 4) pp:2230
Publication Date(Web):February 3, 2014
DOI:10.1021/am405768m
Self-assembling of reduced graphene oxide platelets, as a tailored interconnected network within a natural rubber matrix, is proposed as a mean for obtaining nanocomposites with improved gas barrier, as compared to neat natural rubber. Interestingly, this nanocomposite structure results to be much more effective than homogeneous dispersion of graphene platelike particles, even at low graphene loadings. Such behavior is interpreted on the grounds of a theoretical model describing permeability of heterogeneous systems specifically accounting for self-segregated graphene morphology.Keywords: gas permeability; modelings; nanocomposite; natural rubber; reduced graphene oxide; self-assembling;
Co-reporter:Rui Tong, Xili Lu and Hesheng Xia
Chemical Communications 2014 vol. 50(Issue 27) pp:3575-3578
Publication Date(Web):11 Feb 2014
DOI:10.1039/C4CC00103F
Two different site-specific cleavage mechanisms for copolymer micelles under ultrasound and redox were confirmed. The finding that ultrasound induced mechanochemical cleavage of central ester bonds can open up a new way in the design of novel ultrasound responsive copolymer micelles for drug release.
Co-reporter:Hongji Zhang, Hesheng Xia, and Yue Zhao
ACS Macro Letters 2014 Volume 3(Issue 9) pp:940
Publication Date(Web):September 4, 2014
DOI:10.1021/mz500520b
A unique property of photothermal effect-based shape-memory polymers (SMPs) is demonstrated using a chemically cross-linked poly(ethylene oxide) (PEO) loaded with a small amount (0.5 wt %) of gold nanoparticles (AuNPs). We show that controlled surface plasmon resonance absorption of AuNPs allows for the formation of a temperature gradient in the polymer of temporary shape, which results in anisotropic polymer chain relaxation and strain energy release. This photoinduced temperature gradient effect enables the use of a laser to create a multitude of deformations and to control sophisticated motion executing mechanical work that are otherwise inaccessible with SMPs.
Co-reporter:Ning Yan, Giovanna Buonocore, Marino Lavorgna, Saulius Kaciulis, Santosh Kiran Balijepalli, Yanhu Zhan, Hesheng Xia, Luigi Ambrosio
Composites Science and Technology 2014 Volume 102() pp:74-81
Publication Date(Web):6 October 2014
DOI:10.1016/j.compscitech.2014.07.021
Natural rubber (NR)-reduced graphene oxide (rGO) composites were produced via latex mixing and co-coagulation approach followed by static hot-press and twin roll mixing process. Due to the process, a fine control of filler dispersion was obtained and the composites exhibited a three-dimensional rGO network or alternatively a homogeneous dispersion of single rGO platelets. The effect of rGO dispersion on chemical crosslink structure, and their influence on mechanical and barrier properties was thoroughly investigated. Small angle X-ray scattering (SAXS) and solid-state 13C NMR analysis showed that rGO platelets affect the vulcanization process of natural rubber and that the crosslinking sulphur polysulphidic species present in pristine natural rubber decrease with the rGO content. In fact, at rGO content higher than 6 phr, the crosslinking species consist mainly of monosulphidic species which attain a consequent increment of intrinsic crosslinking density. However, the composites with rGO segregated network exhibit both barrier to oxygen and water vapour permeation and mechanical properties improved with respect to pristine rubber and composites with the homogeneous dispersion of single rGO platelets. The results confirm that the morphology of filler has a prominent key role in determining the natural rubber composites properties.
Co-reporter:Zhenhua Wang, Wenru Fan, Rui Tong, Xili Lu and Hesheng Xia
RSC Advances 2014 vol. 4(Issue 49) pp:25486-25493
Publication Date(Web):28 May 2014
DOI:10.1039/C4RA02843K
A big challenge in developing stimuli-responsive materials is to integrate multiple functionalities such as shape memory property, healable ability, recyclability into a single-component material. With this purpose, we designed a novel poly(n-butyl acrylate-co-methyl methacrylate) bearing a side group 2,6-bis(1′-methylbenzimidazolyl)pyridine ligand, which is dynamically crosslinked by the metal salt zinc trifluoromethanesulfonate to obtain the metallosupramolecular polymer. The shape recovery and healing is achieved upon application of a thermal or light stimulus due to the specific metal–ligand interactions which not only serve as an “inert” crosslink network at low temperature to produce the shape recovery, but also dissociate at high temperature for healing. The healing rate is quick and the healing efficiently is close to ∼90%.
Co-reporter:Guo Li, Guoxia Fei, Bo Liu, Hesheng Xia and Yue Zhao
RSC Advances 2014 vol. 4(Issue 62) pp:32701-32709
Publication Date(Web):09 Jul 2014
DOI:10.1039/C4RA04586F
High intensity focused ultrasound (HIFU)-triggered shape memory has distinct features due to the unique heating mechanism based on polymer chain shearing and friction activated by ultrasonic energy. In this study we chose crosslinked poly(methyl methacrylate-co-butyl acrylate) P(MMA-BA) as a model polymer and studied in detail the HIFU induced thermal effect and shape recovery characteristics. It was found that HIFU heating for polymers is quick and spatially localized, and can be controlled by the ultrasound power, which allows for a spatiotemporally controllable shape memory process. The effects of various parameters including sample thickness, copolymer composition and crosslinker content on the HIFU-induced thermal effect and shape recovery were investigated. Under HIFU irradiation, there exists an optimum sample thickness for a maximum thermal effect and thus better shape recovery, which is different from conventional heating. Moreover, both the copolymer composition and the crosslinker content have a profound effect on the HIFU-induced temperature rise and thus the shape recovery. These effects can be related to changes in the viscoelastic parameter loss tangent (tanδ) of the copolymer around the glass transition temperature Tg that is the transition temperature for the shape recovery process.
Co-reporter:Juan Xuan, Dehui Han, Hesheng Xia, and Yue Zhao
Langmuir 2014 Volume 30(Issue 1) pp:410-417
Publication Date(Web):2017-2-22
DOI:10.1021/la404493n
The design, synthesis, and study of a new dual-stimuli-responsible ABC-type triblock copolymer are reported. Using ATRP and click coupling reaction, the prepared copolymer is composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[2-(dimethylamino)ethylmethacrylate] (PDMAEMA) and features a redox-cleavable disulfide junction between the PEO and PS blocks as well as a photocleavable o-nitrobenzyl linkage between the PS and PDMAEMA blocks. This design allows the triblock copolymer to respond to both a reducing agent like dithiothreitol (DTT) and UV light, while having the minimum number of stimuli-reactive moieties in the copolymer structure (two per chain). The disruption of the triblock copolymer micelles in aqueous solution was examined under the action of either UV light or DTT alone or combined use of the two stimuli. It was found that the removal of one type of hydrophilic polymer chains from the water-soluble corona of the micelles with a hydrophobic PS core, that is, either redox-cleaved PEO or photocleaved PDMAEMA, could only result in a limited destabilization effect on the dispersion of the micelles. Severe aggregation of the polymer was observed only by applying the two stimuli converting the triblock copolymer onto three homopolymers. By monitoring the quenching by aqueous medium of the fluorescence of a hydrophobic dye (Nile Red) loaded in the triblock copolymer micelles, the effect on the payload release was also investigated of the different ways in which the micelles can be disrupted by the stimuli.
Co-reporter:Bo Liang, Rui Tong, Zhenhua Wang, Shengwei Guo, and Hesheng Xia
Langmuir 2014 Volume 30(Issue 31) pp:9524-9532
Publication Date(Web):2017-2-22
DOI:10.1021/la500841x
The metal–supramolecular diblock copolymer containing mechano-labile bis(terpyridine)–Cu(II) complex linkage in the junction point was synthesized. These metal–ligand containing amphiphilic copolymers are able to self-assemble in aqueous solution to form spherical micelles with poly(propylene glycol) block forming the hydrophobic core. It is found that high intensity focused ultrasound can open the copolymer micelles and trigger the release of the payload in the micelle. The micellar properties and release kinetics of encapsulated guest molecule in response to ultrasound stimuli were investigated. The weak Cu(II)–terpyridine dynamic bond in the copolymer chain can be cleaved under ultrasound and thus leads to the disruption of the copolymer micelle and the release of loaded cargo. This study will open up a new way for the molecular design of ultrasound modulated drug delivery systems.
Co-reporter:Rui Tong, Hesheng Xia and Xili Lu
Journal of Materials Chemistry A 2013 vol. 1(Issue 6) pp:886-894
Publication Date(Web):13 Dec 2012
DOI:10.1039/C2TB00222A
Aiming at the development of a controlled redox responsive polymeric micelle system, a series of redox-sensitive ABA triblock degradable copolymers with different amounts of disulfide bonds were synthesized. These multi-disulfide-containing amphiphilic copolymers are able to self-assemble in aqueous solution to form spherical micelles with a hydrophobic polyurethane block forming the hydrophobic core. The presence of dynamic and labile disulfide bonds in the copolymer makes the copolymer and its micelle have responsivity to stimuli such as redox agents and ultrasound. The micellar properties and release kinetics of encapsulated guest molecules in response to stimuli were investigated using hydrophobic pyrene as a fluorescent probe and DTT as a redox agent. The redox-responsive behavior could be adjusted by changing the amount of disulfide bonds within the copolymer backbone. A relatively fast release behavior was observed for micelles formed by the copolymers in which every repeat unit of the hydrophobic block contains a disulfide bond. Furthermore, the release rate could be greatly enhanced and adjusted remotely under HIFU irradiation in the presence of DTT. The HIFU/redox combined stimulus for the specially designed copolymer micelles containing disulfide bonds provides a novel modality for drug delivery systems.
Co-reporter:Jian Zhao, Gaoxing Luo, Jun Wu, and Hesheng Xia
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 6) pp:2040
Publication Date(Web):March 1, 2013
DOI:10.1021/am302929c
Silicone rubber membrane with ordered micropores in the surface was prepared by means of the solvent evaporation-induced phase separation. A ternary solution including liquid silicone rubber precursor, liquid paraffin, and hexane was cast to form a film with a two-phase structure after the hexane was evaporated. The micropores were generated by removing liquid paraffin phase in the cured silicone rubber film. The effects of the liquid paraffin concentration, casting temperature, initial casting solution thickness, air circulation, and addition of surfactant Span-80 on the pore structure in the membrane surface were investigated. The average pore size increases with increasing liquid paraffin concentration or the initial casting solution thickness. The formation of pore structure in the membrane surface is related to the phase separation and thus the phase separation process of the casting solution surface was in situ observed using the digital microscope. The formation mechanism of pore is attributed to a nucleation, growth, and coalescence process of liquid paraffin phase in the membrane surface.Keywords: evaporation-induced phase separation; liquid paraffin; microporous membrane; phase diagram; silicone rubber; surface morphology;
Co-reporter:Hongji Zhang;Daniel Fortin;Yue Zhao
Macromolecular Rapid Communications 2013 Volume 34( Issue 22) pp:1742-1746
Publication Date(Web):
DOI:10.1002/marc.201300640
Co-reporter:Ning Yan;Yanhu Zhan ;Guoxia Fei
Macromolecular Materials and Engineering 2013 Volume 298( Issue 1) pp:38-44
Publication Date(Web):
DOI:10.1002/mame.201200044
Co-reporter:Guoxia Fei, Cristina Tuinea-Bobe, Dongxu Li, Guo Li, Ben Whiteside, Phil Coates and Hesheng Xia
RSC Advances 2013 vol. 3(Issue 46) pp:24132-24139
Publication Date(Web):04 Oct 2013
DOI:10.1039/C3RA43640C
Shape memory polymers with surface micropatterns have seen rising demand for high value applications such as adjustable adherence surfaces, dynamic micro-geometries for cell culture studies and switchable information carriers. Recently, microinjection molding has emerged as an efficient way to manufacture devices which contain surface micro-features using a wide range of polymers with high accuracy. In this study, shape memory polyurethane–carbon nanotube composites were prepared by twin-screw melt extrusion and subsequently processed using microinjection molding to obtain components with surface micropatterns. Then an electro-activated surface micropattern tuning system was developed which could recover the original micropatterned surface of the components after a thermal deformation by applying a current which heats the component using resistive heating. In order to optimize the technique, three key areas were investigated in this work: conductivity of the microinjection molded microparts, the retention of shape memory micropatterns on the surface of microparts during annealing treatment, and the macroscopic area shrinkage of microparts after thermal treatment. It has been found that the electrical conductivity of microinjection molded parts is relatively low due to the high shear rates prevalent in the process. An annealing treatment improves the electrical conductivity by several orders of magnitude, but can be detrimental to the dimensional stability of the micropatterns, which depends significantly on the micro-injection molding parameters, especially the mold temperature. Increasing the mold temperature, melt temperature, injection speed and injection pressure result in better retention of the micropattern and improved dimension stability during annealing treatment. This work demonstrates the potential of electro-activated surface micropattern control for microinjection molded electrically conductive shape memory polymer composites, which could be a promising technology for a range of application areas including electro-adjustable adherence, information storage, and anti-counterfeiting technology.
Co-reporter:Qichun Gong, Jinkui Wu, Xinglong Gong, Yanceng Fan and Hesheng Xia
RSC Advances 2013 vol. 3(Issue 10) pp:3241-3248
Publication Date(Web):04 Jan 2013
DOI:10.1039/C2RA22824F
A new kind of polyurethane (PU) magnetorheological (MR) foam was prepared via in situ polymerization and foaming for the first time. A chain-like structure of carbonyl iron particles in the liquid polyol is formed after orientation at a magnetic field and fixed in the PU foam after the in situ curing. The anisotropic PU MR foam possesses an anisotropic compression property. The compression strength along the magnetic chain direction reaches ∼1053.5 KPa for the sample with 80 wt% carbonyl iron content, which is ∼878 times that of the blank foam and ∼57 times of that at the vertical direction of the same sample. The PU MR foam exhibits a magnetic field controlled shear modulus, i.e., MR effect, which can be adjusted by changing the orientation structure and content of the carbonyl iron, test frequency and magnetic field strength. The maximum absolute and relative MR effects for the anisotropic PU MR foam are ∼1.07 MPa and ∼27.1%, respectively. Moreover, the introduction of carbonyl iron particles can notably improve the acoustic absorption properties in the low frequency region.
Co-reporter:Jianjun Han;Guoxia Fei;Guo Li
Macromolecular Chemistry and Physics 2013 Volume 214( Issue 11) pp:1195-1203
Publication Date(Web):
DOI:10.1002/macp.201200576
Co-reporter:Bo Liu;Guoxia Fei;Guo Li ;Wenru Fan
Macromolecular Chemistry and Physics 2013 Volume 214( Issue 22) pp:2519-2527
Publication Date(Web):
DOI:10.1002/macp.201300320
Co-reporter:Ning Yan;Jinkui Wu;Yanhu Zhan;Guoxia Fei;Chen Chen
Journal of Applied Polymer Science 2013 Volume 127( Issue 2) pp:933-941
Publication Date(Web):
DOI:10.1002/app.37861
Abstract
Natural rubber (NR)/high density polyethylene (HDPE) thermoplastic vulcanizate was compatibilized with graphene oxide (GO) by an ultrasonically assisted latex mixing process (ULM). GO was dispersed into NR latex by ultrasonic irradiation and followed by latex coagulation to obtain the NR/GO master-batch, which was further mixed and diluted with HDPE and NR via a dynamic vulcanization process to obtain the NR/HDPE/GO hybrid composites. It was found that the stacked GO platelets were successfully exfoliated by the ULM process and have good compatibilization efficiency for the immiscible NR and HDPE. A smaller discrete NR domain was observed in NR/HDPE blend in the presence of the GO. Moreover, the stacked GO platelets enhance the interfacial adhesion and phase compatibility, which results in an increase in mechanical property of NR/HDPE blends. Compared to the NR/HDPE blend, the tensile strength and tensile modulus at 300% strain for NR/HDPE/ (1.5 phr) GO blend were increased by ∼ 27% and ∼ 24%, respectively. The exfoliated GO can act as both the effective reinforcing filler and compatibilizer in the immiscible NR/HDPE blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Yanhu Zhan, Marino Lavorgna, Giovanna Buonocore and Hesheng Xia
Journal of Materials Chemistry A 2012 vol. 22(Issue 21) pp:10464-10468
Publication Date(Web):24 Apr 2012
DOI:10.1039/C2JM31293J
Vulcanized graphene/natural rubber composites with a conductive segregated network exhibiting good electrical conductivity, water vapor permeability and high mechanical strength are prepared by self-assembly in latex and static hot pressing. The composite exhibits a percolation threshold of ∼0.62 vol% and a conductivity of 0.03 S m−1 at a content of 1.78 vol%, which is ∼5 orders of magnitude higher than that of the composites made by conventional methods at the same loading fraction.
Co-reporter:Guo Li, Guoxia Fei, Hesheng Xia, Jianjun Han and Yue Zhao
Journal of Materials Chemistry A 2012 vol. 22(Issue 16) pp:7692-7696
Publication Date(Web):29 Feb 2012
DOI:10.1039/C2JM30848G
In this paper, we report a new modality enabling the simultaneous control of shape memory polymers (SMPs) and release of loaded drugs. The approach uses high intensity focused ultrasound (HIFU) and explores localized heating of SMPs upon HIFU exposure. We show that the HIFU-triggered shape recovery process can be spatially and temporarily controlled, allowing the shape memory effect to manifest in selected regions on demand, endowing SMPs with the capability of adopting multiple intermediate shapes and synchronizing the release of loaded drugs in a switchable manner. To our knowledge, this is the first time that HIFU is utilized as a trigger to reveal these appealing features of SMPs.
Co-reporter:Hongji Zhang, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2012 vol. 22(Issue 3) pp:845-849
Publication Date(Web):09 Nov 2011
DOI:10.1039/C1JM14615G
A new optically triggered shape memory composite material was prepared and investigated. Poly(ε-caprolactone) (PCL)-surface functionalized AuNPs were loaded in a thermosensitive shape-memory polymer (SMP) matrix of biodegradable, branched oligo(ε-caprolactone) (bOCL) cross-linked with hexamethylene diisocyanate (HMDI), referred to as XbOCL. By making use of a localized photothermal effect arising from the SPR absorption of AuNPs, we are able to demonstrate an optically triggered and spatially selective shape recovery process, with a stretched AuNP-loaded XbOCL film undergoing stepwise contraction and lifting of a load. Since the shape recovery process can be halted at any time by turning off the light exposure, multiple intermediate shapes can readily be obtained. These are appealing features that cannot be obtained from thermally activated SMPs based on a bulk thermal effect. Moreover, the magnitude of the photoinduced temperature increase of the material can be controlled by adjusting the laser power, it is also possible to use the same AuNP-loaded composite material for applications with different environmental temperatures below Ttransition, since the thermal transition at T > Ttransition can be optically induced by a laser from different environmental temperatures.
Co-reporter:Hongji Zhang, Hesheng Xia, and Yue Zhao
ACS Macro Letters 2012 Volume 1(Issue 11) pp:1233
Publication Date(Web):October 9, 2012
DOI:10.1021/mz300451r
It is discovered that poly(vinyl alcohol) (PVA) hydrogel prepared using the freezing/thawing method can self-repair at room temperature without the need for any stimulus or healing agent. The autonomous self-healing process can be fast for mechanically strong PVA hydrogel yielding a high fracture stress. Investigation on the effect of the hydrogel preparation conditions points out that hydrogen bonding between PVA chains across the interface of the cut surfaces is at the origin of the phenomenon. The key for an effective self-healing is to have an appropriate balance between high concentration of free hydroxyl groups on PVA chains on the cut surfaces prior to contact and sufficient PVA chain mobility in the hydrogel.
Co-reporter:Guoxia Fei, Guo Li, Lisha Wu and Hesheng Xia
Soft Matter 2012 vol. 8(Issue 19) pp:5123-5126
Publication Date(Web):05 Apr 2012
DOI:10.1039/C2SM07357A
Crosslinked P(MMA-BA)–CNTs shape memory composites prepared by ultrasound assisted in situ polymerization, have both relatively high electrical conductivities and good shape memory properties. Electrical resistance heating was used as a trigger to realize the spatial and temporal control of the shape memory process and to obtain multiple shapes by selecting the place where the electrical voltage was applied or switching the power on/off.
Co-reporter:Jinkui Wu;Xinglong Gong;Yanceng Fan
Journal of Applied Polymer Science 2012 Volume 123( Issue 4) pp:2476-2484
Publication Date(Web):
DOI:10.1002/app.34808
Abstract
The highly filled anisotropic polyurethane (PU) magnetorheological elastomers (MREs) were prepared through an in-situ one-step polycondensation process under a magnetic field. The carbonyl iron formed chain-like structure, which was fixed in the PU matrix. The plasticizer diisooctyl phthalate (DOP) was incorporated into PU to soften the matrix and improve the MR effect. The influence of DOP on the microstructure and properties of PU MREs were investigated. The incorporation of DOP reduced the viscosity of the prepolymer and made the carbonyl iron align more easily in the PU matrix. The aligned chain-like structure of carbonyl iron in PU greatly enhanced the thermal conductivity and the compressive properties of PU MREs. The incorporation of DOP reduced the modulus of PU MREs and the glass transition temperature of the soft segments of PU. But highly filled carbonyl iron and DOP led to a decrease in the thermal stability to some extent. The MR test showed that DOP plasticization significantly enhanced both absolute and relative MR effect simultaneously. With 70 wt% carbonyl iron and 15 wt% DOP (the weight ratio of Fe: PU: DOP is 70 : 15: 15), the absolute and relative MR effects of anisotropic PU MREs were ∼ 1.16 MPa and ∼ 386.7%, ∼ 3.5 and ∼ 58 times of the PU MRE without the plasticizer at the same iron content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Juan Xuan, Olivier Boissière, Yi Zhao, Bin Yan, Luc Tremblay, Serge Lacelle, Hesheng Xia, and Yue Zhao
Langmuir 2012 Volume 28(Issue 47) pp:16463-16468
Publication Date(Web):November 6, 2012
DOI:10.1021/la303946b
A new approach for amplifying the effect of high-intensity focused ultrasound (HIFU) in disassembling amphiphilic block copolymer (BCP) micelles in aqueous solution was investigated. The diblock copolymer is comprised of a water-soluble poly(ethylene oxide) (PEO) block and a block of poly(2-(2-methoxyethoxy)ethyl methacrylate) (PMEO2MA) that is hydrophobic at temperatures above its lower critical solution temperature (LCST). We show that by introducing a small amount of HIFU-labile 2-tetrahydropyranyl methacrylate (THPMA) comonomer units into the PMEO2MA that forms the micelle core at T > LCST, an ultrasound irradiation of a micellar solution could induce the hydrolysis of THPMA groups. As a result, the LCST of the thermosensitive polymer increases due to the conversion of hydrophobic THPMA comonomer units onto hydrophilic methacrylic acid. Consequently, the BCP micelles disassemble without actually changing the solution temperature. In addition to the characterization results of transmittance measurements, variable-temperature 1H NMR, SEM, and DLS, a 13C NMR spectral analysis provided critical evidence for the hydrolysis reaction of THPMA groups under HIFU irradiation.
Co-reporter:Jinkui Wu, Xinglong Gong, Yanceng Fan and Hesheng Xia
Soft Matter 2011 vol. 7(Issue 13) pp:6205-6212
Publication Date(Web):26 May 2011
DOI:10.1039/C1SM05386H
Physically cross-linked isotropic and anisotropic poly(vinyl alcohol) (PVA) hydrogels containing micron-sized carbonyl iron particles were prepared through a cyclic freezing–thawing process. The PVA hydrogel can respond to a magnetic field and shows a magnetorheological (MR) effect, i.e., the modulus of the PVA hydrogel can be adjusted under a magnetic field. The chain-like structures of carbonyl iron are formed in the PVA hydrogel after orientation under a magnetic field of 1.5 T. Also some magnetic field induced oriented pores with a tunable diameter are observed in the dried PVA gel. The MR effect can be adjusted by changing the carbonyl iron content, the initial concentration of PVA solution and test frequency. The formation of aligned chain-like structures of carbonyl iron in the anisotropic PVA MR hydrogel improves the compression properties and the MR effect. At a carbonyl iron content of 70 wt%, the maximum absolute and relative MR effect of anisotropic PVA MR hydrogels are ∼1.24 MPa and ∼230%, respectively. The PVA hydrogels with good MR effects and moderate mechanical strength have potential applications in artificial muscle, soft actuators and drug release.
Co-reporter:Yanhu Zhan;Jinkui Wu;Ning Yan;Guoxia Fei;Guiping Yuan
Macromolecular Materials and Engineering 2011 Volume 296( Issue 7) pp:590-602
Publication Date(Web):
DOI:10.1002/mame.201000358
Co-reporter:Juan Xuan;Maxime Pelletier;Yue Zhao
Macromolecular Chemistry and Physics 2011 Volume 212( Issue 5) pp:498-506
Publication Date(Web):
DOI:10.1002/macp.201000624
Co-reporter:Yongwen Li, Rui Tong, Hesheng Xia, Hongji Zhang and Juan Xuan
Chemical Communications 2010 vol. 46(Issue 41) pp:7739-7741
Publication Date(Web):09 Sep 2010
DOI:10.1039/C0CC02628J
A novel class of HIFU and redox dual responsive polymer with a disulfide bond weak linkage is developed. The novel modality of HIFU and redox triggered release allows for the fine-tuning of the release kinetics of the encapsulants from the micelles in a remote and controlled way.
Co-reporter:Xinrui Zhong;Guoxia Fei
Journal of Applied Polymer Science 2010 Volume 118( Issue 4) pp:2146-2152
Publication Date(Web):
DOI:10.1002/app.32531
Abstract
Poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles with a size of 50–100 nm were prepared by the oxidation polymerization of the monomer 3,4-ethylenedioxythiophene (EDOT) under ultrasonic irradiation. The structure and morphology of PEDOT, as well as the electrical conductivity were characterized. Compared with the conventional stirring method, the PEDOT nanoparticles prepared by ultrasonic irradiation have a smaller particle size and are more uniform and spherical due to the dispersion, emulsifying and disruption effects of ultrasound. The yield of PEDOT by ultrasonic irradiation can reach ∼ 50%, and the conductivity of PEDOT is high up to 11 S/cm. A decrease in particle size due to the ultrasonication can lead to more effective doping and enhanced conductivity. The reaction time, temperature and ultrasound power output have significant effects on the field and electrical conductivity of PEDOT. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Jinkui Wu;Xinglong Gong;Lin Chen;Zaiguo Hu
Journal of Applied Polymer Science 2009 Volume 114( Issue 2) pp:901-910
Publication Date(Web):
DOI:10.1002/app.30563
Abstract
The highly filled isotropic polyurethane (PU) elastomer with a magnetorheological (MR) effect was prepared through an in situ polycondensation method. The carbonyl iron particles were treated by coupling agents and then the dispersions of polyol/carbonyl iron particles was prepared by a ball milling process. The dispersion problem of magnetizable particles at a high content in PU matrix was tried to overcome by the combination of surface modification, ball milling, and in situ polymerization. The microstructure and properties of the composite were examined in detail. With increasing the content of carbonyl iron particles, the degree of phase separation of PU increased and the glass transition temperature (Tg) of PU soft segment decreased. Highly filled carbonyl iron particles led to the decrease in the thermal stability of PU matrix, especially in the heating air atmosphere. The MR effect appeared when the content of carbonyl iron particles was higher than 50 wt %, and became relatively pronounced at a 70 wt % of carbonyl iron content. The mechanical properties of PU MR elastomers were deteriorated significantly at a high content of carbonyl iron. Surface modification of carbonyl iron particles can improve the mechanical properties to some extent; however, it was also found that surface modification led to a decrease in the MR effect because of the improved interfacial adhesion. The MR test showed that the maximum absolute MR effect and relative MR effect of PU composite were ∼ 0.31 MPa and ∼ 8.1% at 1 Hz and 400 mT with 70 wt % of carbonyl iron, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Jie Wang, Maxime Pelletier, Hongji Zhang, Hesheng Xia and Yue Zhao
Langmuir 2009 Volume 25(Issue 22) pp:13201-13205
Publication Date(Web):July 2, 2009
DOI:10.1021/la9018794
Micelles of a diblock copolymer composed of poly(ethylene oxide) and poly(2-tetrahydropyranyl methacrylate) (PEO-b-PTHPMA) in aqueous solution could be disrupted by high-frequency ultrasound (1.1 MHz). It was found that, upon exposure to a high-intensity focused ultrasound (HIFU) beam at room temperature, the pH value of the micellar solution decreased over irradiation time. The infrared spectroscopic analysis of solid block copolymer samples collected from the ultrasound irradiated micellar solution revealed the formation of carboxylic acid dimers and hydroxyl groups. These characterization results suggest that the high-frequency HIFU beam could induce the hydrolysis reaction of THPMA at room temperature resulting in the cleavage of THP groups. The disruption of PEO-b-PTHPMA micelles by ultrasound was investigated by using dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. On the basis of the pH change, it was found that the disruption process was determined by a number of factors such as the ultrasound power, the micellar solution volume and the location of the focal spot of the ultrasound beam. This study shows the potential to develop ultrasound-sensitive block copolymer micelles by having labile chemical bonds in the polymer structure, and to use the high-frequency HIFU to trigger a chemical reaction for the disruption of micelles.
Co-reporter:Rui Tong, Xili Lu and Hesheng Xia
Chemical Communications 2014 - vol. 50(Issue 27) pp:NaN3578-3578
Publication Date(Web):2014/02/11
DOI:10.1039/C4CC00103F
Two different site-specific cleavage mechanisms for copolymer micelles under ultrasound and redox were confirmed. The finding that ultrasound induced mechanochemical cleavage of central ester bonds can open up a new way in the design of novel ultrasound responsive copolymer micelles for drug release.
Co-reporter:Yongwen Li, Rui Tong, Hesheng Xia, Hongji Zhang and Juan Xuan
Chemical Communications 2010 - vol. 46(Issue 41) pp:NaN7741-7741
Publication Date(Web):2010/09/09
DOI:10.1039/C0CC02628J
A novel class of HIFU and redox dual responsive polymer with a disulfide bond weak linkage is developed. The novel modality of HIFU and redox triggered release allows for the fine-tuning of the release kinetics of the encapsulants from the micelles in a remote and controlled way.
Co-reporter:Yanhu Zhan, Marino Lavorgna, Giovanna Buonocore and Hesheng Xia
Journal of Materials Chemistry A 2012 - vol. 22(Issue 21) pp:
Publication Date(Web):
DOI:10.1039/C2JM31293J
Co-reporter:Guo Li, Guoxia Fei, Hesheng Xia, Jianjun Han and Yue Zhao
Journal of Materials Chemistry A 2012 - vol. 22(Issue 16) pp:NaN7696-7696
Publication Date(Web):2012/02/29
DOI:10.1039/C2JM30848G
In this paper, we report a new modality enabling the simultaneous control of shape memory polymers (SMPs) and release of loaded drugs. The approach uses high intensity focused ultrasound (HIFU) and explores localized heating of SMPs upon HIFU exposure. We show that the HIFU-triggered shape recovery process can be spatially and temporarily controlled, allowing the shape memory effect to manifest in selected regions on demand, endowing SMPs with the capability of adopting multiple intermediate shapes and synchronizing the release of loaded drugs in a switchable manner. To our knowledge, this is the first time that HIFU is utilized as a trigger to reveal these appealing features of SMPs.
Co-reporter:Hongji Zhang, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2012 - vol. 22(Issue 3) pp:NaN849-849
Publication Date(Web):2011/11/09
DOI:10.1039/C1JM14615G
A new optically triggered shape memory composite material was prepared and investigated. Poly(ε-caprolactone) (PCL)-surface functionalized AuNPs were loaded in a thermosensitive shape-memory polymer (SMP) matrix of biodegradable, branched oligo(ε-caprolactone) (bOCL) cross-linked with hexamethylene diisocyanate (HMDI), referred to as XbOCL. By making use of a localized photothermal effect arising from the SPR absorption of AuNPs, we are able to demonstrate an optically triggered and spatially selective shape recovery process, with a stretched AuNP-loaded XbOCL film undergoing stepwise contraction and lifting of a load. Since the shape recovery process can be halted at any time by turning off the light exposure, multiple intermediate shapes can readily be obtained. These are appealing features that cannot be obtained from thermally activated SMPs based on a bulk thermal effect. Moreover, the magnitude of the photoinduced temperature increase of the material can be controlled by adjusting the laser power, it is also possible to use the same AuNP-loaded composite material for applications with different environmental temperatures below Ttransition, since the thermal transition at T > Ttransition can be optically induced by a laser from different environmental temperatures.
Co-reporter:Guo Li, Hu Zhang, Daniel Fortin, Weizheng Fan, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2016 - vol. 4(Issue 25) pp:NaN5939-5939
Publication Date(Web):2016/05/24
DOI:10.1039/C6TC01377E
A photoresponsive shape memory composite material with room temperature programmability is reported in this paper. The material is composed of poly(styrene-b-ethylene-co-butadiene-b-styrene) (SEBS: a thermoplastic elastomer), paraffin wax (PW: a mixture of short hydrocarbon chains with a melting point around 60 °C) and gold nanoparticles (AuNPs). On one hand, the SEBS/PW system is room temperature programmable, meaning that the temporary shape can be processed by directly deforming the material into a desired shape at room temperature. Particularly interesting is that the fixed deformation is not limited to elongation or compression, but includes other types of deformation like twisting and bending. This attribute makes three-dimensional shape processing doable under ambient conditions without heating or cooling. The results of wide-angle X-ray diffraction measurements on elongated SEBS/PW samples suggest that the stretching-induced orientation and reorganization of PW crystals could form a solid skeleton to sustain the elastic extension of the rubbery EB chains, resulting in the apparent plastic deformation. On the other hand, by loading a small amount of AuNPs (0.18 wt%) in the composite material, the shape recovery, which occurs upon melting of PW crystals, becomes controllable using visible light based on the photothermal effect arising from the surface plasmon resonance of AuNPs. Thanks to the ability of remote activation and spatiotemporal control, a potential application of photoresponsive shape memory materials with room temperature programmability is demonstrated using SEBS/PW/AuNP: damage inflicted on an object or a product in the form of mechanical deformation or shape distortion can be conveniently and effectively repaired using a visible light laser (532 nm) at room temperature.
Co-reporter:Rui Tong, Hesheng Xia and Xili Lu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 6) pp:NaN894-894
Publication Date(Web):2012/12/13
DOI:10.1039/C2TB00222A
Aiming at the development of a controlled redox responsive polymeric micelle system, a series of redox-sensitive ABA triblock degradable copolymers with different amounts of disulfide bonds were synthesized. These multi-disulfide-containing amphiphilic copolymers are able to self-assemble in aqueous solution to form spherical micelles with a hydrophobic polyurethane block forming the hydrophobic core. The presence of dynamic and labile disulfide bonds in the copolymer makes the copolymer and its micelle have responsivity to stimuli such as redox agents and ultrasound. The micellar properties and release kinetics of encapsulated guest molecules in response to stimuli were investigated using hydrophobic pyrene as a fluorescent probe and DTT as a redox agent. The redox-responsive behavior could be adjusted by changing the amount of disulfide bonds within the copolymer backbone. A relatively fast release behavior was observed for micelles formed by the copolymers in which every repeat unit of the hydrophobic block contains a disulfide bond. Furthermore, the release rate could be greatly enhanced and adjusted remotely under HIFU irradiation in the presence of DTT. The HIFU/redox combined stimulus for the specially designed copolymer micelles containing disulfide bonds provides a novel modality for drug delivery systems.
Co-reporter:Jian Zhao, Rui Xu, Gaoxing Luo, Jun Wu and Hesheng Xia
Journal of Materials Chemistry A 2016 - vol. 4(Issue 5) pp:NaN989-989
Publication Date(Web):2015/12/11
DOI:10.1039/C5TB02036K
The thermally healable polysiloxane elastomers were successfully prepared by cross-linking polydimethylsiloxane bearing maleimide pendants with furan-end functionalized siloxane via the Diels–Alder (DA) reaction. The elastomers with good mechanical properties show excellent self-healing and remoldability functions due to the thermally reversible feature of the DA reaction. The molecular mechanism of self-healing was confirmed by in situ structural characterization. Moreover, the biocompatibility of the polysiloxane elastomer containing DA bonds is found to be fairly good by cytotoxicity evaluation and animal subcutaneous experiments, suggesting its potential applications in the biomedical field as artificial skin and scaffolds for tissue engineering.
Co-reporter:Hongji Zhang, Dehui Han, Qiang Yan, Daniel Fortin, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 33) pp:NaN13379-13379
Publication Date(Web):2014/06/11
DOI:10.1039/C4TA02463J
A general method for preparing mechanically strong hydrogels that can undergo light-triggered healing was demonstrated. By loading a small amount of gold nanoparticles (AuNPs, 0.05 wt%) in hydrogels prepared with stearyl acrylate (SA), N,N-dimethylacrylamide (DMA) and N,N′-methylenebisacrylamide (MBA), whose strength is endowed by chemical crosslinking coexisting with crystallized hydrophobic SA side chains acting as the physical crosslinks, exposing a cut-through damage to a laser of wavelength at the surface plasmon resonance of AuNPs and subsequently turning off the light, gives rise to efficient healing of the hydrogel as a result of the reversible melting–crystallization phase transition of the hydrophobically associated SA chains. A hydrogel of this kind exhibits an unprecedented tensile strength, after repairing, of greater than 2 MPa. It also displays a light-controllable shape memory effect.
Co-reporter:Xili Lu, Guoxia Fei, Hesheng Xia and Yue Zhao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 38) pp:NaN16060-16060
Publication Date(Web):2014/08/04
DOI:10.1039/C4TA02726D
The concept of using ultrasound to trigger shape memory assisted healing of covalently cross-linked dynamic polymers is demonstrated. The well-designed dynamically crosslinked poly(ε-caprolactone)-based polyurethane bearing Diels–Alder bonds not only possesses high mechanical strength and toughness, but also exhibits shape memory assisted crack-closure and healing upon exposure to high-intensity focused ultrasound owing to breaking and reformation of dynamic bonds. The use of focused ultrasound allows the healing process to be activated remotely and to be controlled locally by depositing the acoustic energy only in the damaged region without detriment to the undamaged parts of the material. The healable polyurethane materials have potential applications such as long-term load-bearing engineering components and anti-fatigue medical devices.
Co-reporter:Shuchi Liao, Tianliang Zhai and Hesheng Xia
Journal of Materials Chemistry A 2016 - vol. 4(Issue 3) pp:NaN1077-1077
Publication Date(Web):2015/12/08
DOI:10.1039/C5TA09540A
The graphene oxide aerogel microspheres were prepared by a novel approach, i.e. a combination of electrospraying and freeze-casting. The unique well-defined “center-diverging microchannel” dandelion-like structures were observed in the aerogel microspheres and a formation mechanism of the structure, i.e. radial-directional freezing–thawing, was proposed. After further thermal reduction, the reduced graphene oxide aerogel microspheres were obtained and the center-diverging microchannel structures can be remained. Due to their highly porous, hierarchical and hydrophobic structure as well as a random packing effect, the aerogel microspheres possess excellent adsorption ability for various organic solvents and oils, showing their potential applications in environmental pollutant treatment.
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