Co-reporter:Jin-Tao Wang, Lin Wang, Xiaotian Ji, Li Liu, and Hanying Zhao
Macromolecules March 28, 2017 Volume 50(Issue 6) pp:2284-2284
Publication Date(Web):March 16, 2017
DOI:10.1021/acs.macromol.6b02665
Combinations of synthetic polymers and natural proteins provide a route to the synthesis of new biomaterials. The bioconjugates combining tunable properties of polymers with functionalities of proteins have found broad applications. One of the most challenging problems in this research field is the self-assembly behaviors of responsive polymer–protein bioconjugates. In this research, synthesis and self-assembly of bioconjugates composed of zwitterionic block copolymer and streptavidin were investigated. Block copolymers of poly(ethylene glycol) (PEG) and poly[3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] (PDMAPS) with cleavable biotin groups at the junction points were synthesized. The zwitterionic block copolymers exhibit phase transitions with upper critical solution temperatures (UCSTs) in aqueous solutions. The concentration of sodium chloride exerts a significant influence on the UCST. The zwitterionic block copolymer chains self-assemble into vesicles in aqueous solution at a temperature below UCST. Bioconjugates comprising of streptavidin molecules and zwitterionic block copolymer chains were fabricated based on biotin–streptavidin coupling. Upon conjugation to the protein molecules, the UCST of the zwitterionic block copolymer decreases due to the screening effect of the protein molecules. The bioconjugates are able to make self-assembly into different structures, depending on the average number of block copolymer chains on a protein molecule. The bioconjugate molecules with average 1.3 block copolymer chains on a streptavidin self-assemble into rodlike structures, while those with average 2.9 chains on a streptavidin self-assemble into spherical micelles.
Co-reporter:Weijing Fan; Li Liu; Hanying Zhao
Angewandte Chemie International Edition 2017 Volume 56(Issue 30) pp:8844-8848
Publication Date(Web):2017/07/17
DOI:10.1002/anie.201704955
AbstractThe development in the synthesis and self-assembly of patchy nanoparticles has resulted in the creation of complex hierarchical structures. Co-assembly of polymeric nanoparticles and protein molecules combines the advantages of polymeric materials and biomolecules, and will produce new functional materials. Co-assembly of positively charged patchy micelles and negatively charged bovine serum albumin (BSA) molecules is investigated. The patchy micelles, which were synthesized using block copolymer brushes as templates, leads to co-assembly with protein molecules into vesicular structures. The average size of the assembled structures can be controlled by the molar ratio of BSA to patchy micelles. The assembled structures are dissociated in the presence of trypsin. The protein–polymer hybrid vesicles could find potential applications in medicine.
Co-reporter:Yuanyuan Tao, Hanying Zhao
Polymer 2017 Volume 122(Volume 122) pp:
Publication Date(Web):28 July 2017
DOI:10.1016/j.polymer.2017.06.046
•Tadpole-shaped polymer with disulfide bonds at the junction points was synthesized.•Tadpole-shaped polymer self-assembles into shell-sheddable vesicles.•CMCs of tadpole-shaped and linear block copolymer were measured and compared.•Self-assembled structures made by tadpole-shaped and linear block copolymer were compared.Shell-sheddable polymeric assemblies are a type of self-assembled structures formed by amphiphilic block copolymers with cleavable linkages at the junction points. The shell-sheddable self-assemblies have been used as nanocarriers for drugs and inorganic nanoparticles. In this research, synthesis and self-assembly of amphiphilic tadpole-shaped block copolymer with disulfide bonds at the junction points were investigated. Dialkyne-terminated polystyrene (Da-PS) was synthesized by reversible addition-fragmentation chain transfer polymerization and thiol-disulfide exchange reaction. The tadpole-shaped block copolymer was synthesized by bimolecular coupling between azido-terminated PEG and Da-PS. Size exclusion chromatograph, FTIR, 1H NMR and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass analysis results all indicated successful synthesis of the polymer. The tadpole-shaped block copolymer self-assembles into vesicles in aqueous solution. The disulfide bonds at the junction points can be cleaved by a reducing agent, resulting in aggregation of the assemblies.Download high-res image (260KB)Download full-size image
Co-reporter:Guangda Han, Jin-Tao Wang, Xiaotian Ji, Li Liu, and Hanying Zhao
Bioconjugate Chemistry 2017 Volume 28(Issue 2) pp:
Publication Date(Web):December 30, 2016
DOI:10.1021/acs.bioconjchem.6b00704
Proteinosomes are a type of protein-based spherical capsules, which have potential applications in drug delivery, cell imaging, gene expression, and biocatalysis. In this research, a novel approach to the fabrication of proteinosomes entirely composed of protein molecules based on self-assembly of a supramolecular protein–polymer conjugate is proposed. A supramolecular protein–polymer conjugate was prepared by mixing βCD-modified bovine serum albumin (BSA) and adamantane-terminated poly(N-isopropylamide) (Ad-PNIPAM) in aqueous solution. The BSA-PNIPAM bioconjugate self-assembled into micelles with PNIPAM cores and BSA coronae at a temperature above the lower critical solution temperature (LCST) of PNIPAM. After cross-linking of BSA in the coronae, and followed by addition of excess βCD, PNIPAM chains were cleaved from the micellar structures, and nanoscale proteinosomes were prepared. The dual-responsive proteinosomes dissociated in the presence of trypsin or glutathione.
Co-reporter:Yuanyuan Ju;Mingming Zhang
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 35) pp:5415-5426
Publication Date(Web):2017/09/12
DOI:10.1039/C7PY01012E
The bio-functionalization of poly(ε-caprolactone) (PεCL) provides an approach to broaden the applications of the polymer in medical and biological engineering fields. In this research, PεCL with pendant glutathione (GSH) or L-carnosine was synthesized by a combination of ring-opening copolymerization, Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction (click reaction) and thiol-disulfide exchange reaction. The ring-opening copolymerization of εCL and α-chloro-ε-caprolactone (αCl-εCL) was employed in the synthesis of the PεCL-co-P(αCl-εCL) copolymer. The pendent chlorides were converted into azides by a reaction with sodium azide. N-Hydroxysuccinimide (NHS) groups were introduced into the polymer backbones by the click reaction. PεCL with pendant pyridyl disulfide groups was prepared by a reaction of N-hydroxysuccinimide (NHS) activated ester and pyridine dithioethylamine. Peptide modified PεCL were synthesized by thiol-disulfide exchange reactions between thiol groups on GSH (or thiol-modified L-carnosine) and the pendant pyridyl disulfide groups on the polymer chains. The synthesized copolymers were analyzed by size exclusion chromatography, FTIR, 1H NMR and differential scanning calorimetry. The bio-graft copolymers are able to self-assemble into micelles or vesicles in aqueous solutions, depending on the pH values of the solutions. The assembled structures formed by the bio-graft copolymers in aqueous solutions are essentially nontoxic toward MCF-7 and COS-7 cells. The functionalization of the peptide-stabilized assembled structures with lysozyme was also investigated in this research.
Co-reporter:Xiaotian Ji;Li Liu
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 18) pp:2815-2823
Publication Date(Web):2017/05/09
DOI:10.1039/C7PY00315C
Recently, the synthesis of bioconjugates combining tunable properties of polymers with the functionalities of proteins has aroused great interest in the biomaterials community. In this research, thermally-responsive polymer chains with pendant lysozyme molecules were prepared via a “grafting to” approach. The enzyme molecules were anchored to the polymer backbones through covalent bonds. The influences of the number of pendant enzyme molecules and the salt concentration on the thermal-responsive properties of the bioconjugates were investigated. With an increase in the number of pendant lysozyme molecules, the cloud point (TCP) shifts to a higher temperature. The TCPs of the bioconjugates decrease with an increase in the salt concentration. In aqueous solutions, the bioconjugate molecules make core–shell structures at a temperature below TCP due to the unfavorable interaction between the polymer chains and the enzyme molecules. The bioconjugates are able to self-assemble into mesoglobules at temperatures above TCP. The secondary structure and bioactivity of the enzyme on the assembled structures were basically maintained.
Co-reporter:Weijing Fan; Li Liu; Hanying Zhao
Angewandte Chemie 2017 Volume 129(Issue 30) pp:8970-8974
Publication Date(Web):2017/07/17
DOI:10.1002/ange.201704955
AbstractThe development in the synthesis and self-assembly of patchy nanoparticles has resulted in the creation of complex hierarchical structures. Co-assembly of polymeric nanoparticles and protein molecules combines the advantages of polymeric materials and biomolecules, and will produce new functional materials. Co-assembly of positively charged patchy micelles and negatively charged bovine serum albumin (BSA) molecules is investigated. The patchy micelles, which were synthesized using block copolymer brushes as templates, leads to co-assembly with protein molecules into vesicular structures. The average size of the assembled structures can be controlled by the molar ratio of BSA to patchy micelles. The assembled structures are dissociated in the presence of trypsin. The protein–polymer hybrid vesicles could find potential applications in medicine.
Co-reporter:Jin-Tao Wang, Yanhang Hong, Xiaotian Ji, Mingming Zhang, Li Liu and Hanying Zhao
Journal of Materials Chemistry A 2016 vol. 4(Issue 25) pp:4430-4438
Publication Date(Web):01 Jun 2016
DOI:10.1039/C6TB00699J
Polymer–protein core–corona particles can be used as multifunctional platforms in biological and medical applications. In this research, we prepared poly(2-hydroxyethyl methacrylate)–bovine serum albumin (PHEMA–BSA) core–corona particles by the “grafting from” method. In order to prepare the particles, activators generated by electron transfer for atom transfer radical polymerizations (AGET ATRP) of HEMA initiated by a BSA macroinitiator were performed. The polymerizations were conducted in the presence of ppm amounts of transition metal catalyst and ascorbic acid. Transmission electron microscopy, atomic force microscopy, dynamic light scattering and ξ-potential measurements were used to characterize the core–corona particles. The average size and ξ-potentials of the particles are strongly dependent on the amounts of BSA used in AGET ATRP. The secondary structure and bioactivity of the protein molecules in the coronae of the particles were studied. In vitro cytotoxicity assays and cell uptake assays indicate that the biohybrid particles are nontoxic and can be internalized into the cells. The polymer–protein core–corona particles will find applications in drug delivery and biomedical imaging.
Co-reporter:Dawei Chen, Wangmeng Hou, Dongxia Wu, Yunfang Wu, Guochen Cheng, and Hanying Zhao
ACS Macro Letters 2016 Volume 5(Issue 11) pp:1222
Publication Date(Web):October 18, 2016
DOI:10.1021/acsmacrolett.6b00750
Hydrogels containing protein components are a type of promising biomaterial. In this paper, we designed triple-responsive polymer–protein networks based on molecular recognition. Reduced bovine serum albumin (BSA) was modified with multiple β-cyclodextrin (βCD) by thiol–disulfide exchange reaction. The βCD-modified BSA was added into the aqueous solution of acrylamide copolymer with pendant adamantyl groups, resulting in the formation of polymer–protein network structures. The assembled polymer networks show triple-responsive behaviors upon treatment with trypsin, reduced glutathione, or native βCD. The network structures may find applications in tissue engineering and drug controlled release.
Co-reporter:Guangda Han, Yuanyuan Ju and Hanying Zhao
Polymer Chemistry 2016 vol. 7(Issue 5) pp:1197-1206
Publication Date(Web):28 Dec 2015
DOI:10.1039/C5PY01940K
Nanocapsules composed of cross-linked membranes and empty voids have found wide applications as drug delivery carriers, sensors and nanosized reactors. In this research, a new method for the fabrication of functional nanocapsules is proposed. Poly(oligo(ethylene glycol) monomethyl ether methacrylate)-block-(poly(tert-butyl methacrylate)-graft-poly(2-(dimethylamino)ethyl methacrylate)) (POEGMA-b-(PtBMA-g-PDMAEMA)) brush polymers were synthesized by two-step reversible addition–fragmentation chain transfer polymerization and atom transfer radical polymerization. The pendant PDMAEMA chains were grafted to the backbones through disulfide bonds. In acidic water, the brush polymer chains self-assembled into micelles with PtBMA cores and POEGMA/PDMAEMA mixed coronae. Upon cross-linking of PDMAEMA chains and cleavage of the disulfides with tri-n-butylphosphine, hydrophilic nanocapsules were obtained. The brush polymers were analyzed by gel permeation chromatography and 1H NMR. The sizes and the morphologies of the micelles and the nanocapsules were characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The thiol groups on the inner walls of the nanocapsules undergo a thiol–ene reaction with fluorescein O-methacrylate (FMA). The photoluminescence results demonstrate that FMA molecules are able to pass through the membranes and functionalization of the nanocapsules can be performed.
Co-reporter:Xiaona Yang, Dawei Chen, Hanying Zhao
Acta Biomaterialia 2016 Volume 29() pp:446-454
Publication Date(Web):1 January 2016
DOI:10.1016/j.actbio.2015.10.038
Abstract
In this research thermo-responsive polymer brushes and protein molecules are immobilized on the surfaces of silica particles by covalent bonds. Pyridyl disulfide functionalized silica particles are prepared by surface chemical reactions, and thiol-terminated poly(oligo(ethylene glycol) monomethyl ether methacrylate) (POEGMA) and bovine serum albumin (BSA) molecules are grafted to the silica particles by thiol–disulfide exchange reactions. X-ray photoelectron spectroscopy, thermogravimetric analysis, dynamic light scattering, confocal laser scanning microscopy, far-UV circular dichroism and transmission electron microscopy are employed to characterize the polymer/protein mixed layers on silica particles. The POEGMA brushes not only protect the protein molecules but also improve the dispersibility of the hybrid particles in aqueous solution. The activity of the immobilized BSA protein can be controlled by the thermo-responsive POEGMA brushes. At a temperature below the lower critical solution temperature (LCST) of POEGMA, BSA activity is not affected by polymer brushes; however, BSA activity decreases significantly at a temperature above the LCST of POEGMA.
Statement of Significance
In this research, both protein molecules and polymer brushes were anchored to the silica particles by highly efficient thiol–disulfide exchange reaction, and their grafting density can easily be determined by UV–vis. Owing to the temperature-sensitive nature of the grafted polymer brushes, the protein molecules can be protected by the collapsed polymer brushes above the LCST, and their catalytic activity can be controlled. Moreover, the protein molecules on silica particles can be easily separated from the solution and can be reused.
Co-reporter:Yue Zhang and Hanying Zhao
Langmuir 2016 Volume 32(Issue 15) pp:3567-3579
Publication Date(Web):March 28, 2016
DOI:10.1021/acs.langmuir.6b00267
In recent years, an emerging research area has been the surfactant behavior of polymer-tethered nanoparticles. In this feature article, we have provided a general introduction to the synthesis, self-assembly, and interfacial activity of polymer-tethered inorganic nanoparticles, polymer-tethered organic nanoparticles, and polymer-tethered natural nanoparticles. In addition, applications of the polymer-tethered nanoparticles in colloidal and materials science are briefly reviewed. All research demonstrates that amphiphilic polymer-tethered nanoparticles exhibit surfactant behavior and can be used as elemental building blocks for the fabrication of advanced structures by the self-assembly approach. The polymer-tethered nanoparticles provide new opportunities to engineer materials and biomaterials possessing specific functionality and physical properties.
Co-reporter:Xiaotian Ji, Jinchuan Liu, Li Liu, Hanying Zhao
Colloids and Surfaces B: Biointerfaces 2016 Volume 148() pp:41-48
Publication Date(Web):1 December 2016
DOI:10.1016/j.colsurfb.2016.08.043
•Enzyme-polymer nanogels are prepared by thiol-disulfide exchange reactions.•Morphology changes at different temperatures are investigated.•The hybrid nanogels show thermal responsiveness, and LCSTs are determined.•Enzyme molecules immobilized on the nanogels show enhanced heat resistance.In this paper a novel method for the fabrication of hybrid nanogels based on thiol-disulfide exchange reaction is reported. Poly(oligo(ethylene glycol) monomethyl ether methacrylate-co-di(ethylene glycol) methyl ether methacrylate-co-2-(2-pyridyldisulfide) ethyl methacrylate) (POEGMA-co-PDEGMA-co-PDSMA) was synthesized by reversible addition-fragmentation chain transfer polymerization. Pyridyl disulfide functionalized porcine pancreatic lipase (PPL-S-S-Py) was prepared by treatment of PPL with Traut’s reagent (2-iminothiolane) and 2,2′-dithiodipyridine. Upon addition of meso-2,3-dimercaptosuccinic acid into aqueous solutions of PPL-S-S-Py and POEGMA-co-PDEGMA-co-PDSMA, enzyme-polymer hybrid nanogels were prepared. The hybrid nanogels show thermal responsiveness. With an increase in the content of PPL in the nanogels, the lower critical solution temperature (LCST) shifts to the higher temperature. At a temperature below LCST, PPL molecules are in the shells of the nanogels, and at a temperature above LCST, PPL molecules are embedded inside the nanosized structures. The immobilized PPL show enhanced heat resistance and good reusability.
Co-reporter:Yue Zhang, Jiamin Zhang, Cheng Xing, Mingming Zhang, Lianyong Wang, and Hanying Zhao
ACS Biomaterials Science & Engineering 2016 Volume 2(Issue 12) pp:
Publication Date(Web):October 12, 2016
DOI:10.1021/acsbiomaterials.6b00490
There are many natural examples of smart structures that are able to change conformations and functionalities responding to the external stimuli. The responsiveness is directly related to their unique structures. In the design of new materials, it is crucial to endow these materials with the capabilities to change structures and functionalities under the external stimuli. In this research, virus-mimicking protein nanogels with temperature-induced reversible structures and redox responsiveness are synthesized by cross-linking a thermally responsive polymer poly(di(ethylene glycol) methyl ether methacrylate-co-2-(2-pyridyldisulfide) ethyl methacrylate) with reduced bovine serum albumin (BSA) molecules through thiol–disulfide exchange reaction. The lower critical solution temperature (LCST) and sizes of the nanogels can be controlled by controlling the reaction conditions. The nanogels are able to change their structures responding to the temperature change. Below the LCST, BSA molecules are embedded inside the nanogels and protected by the polymer chains. Above the LCST, polymer chains collapse forming the cores, and BSA moves to the shells to stabilize the nanogels. The disulfide-cross-linked nanogels are dissociated in the presence of glutathione. In vitro cytotoxicity assays and cell uptake assays demonstrate that the nanogels show low toxicity toward 3T3, 293T, and MCF-7 cells and can be internalized into the MCF-7 cells. The nanogels will find applications in protein delivery.Keywords: bovine serum albumin; core−shell structure; nanogels; thiol−disulfide exchange reaction;
Co-reporter:Zheng Wei, Shuzhe Zhu and Hanying Zhao
Polymer Chemistry 2015 vol. 6(Issue 8) pp:1316-1324
Publication Date(Web):18 Nov 2014
DOI:10.1039/C4PY01268B
Macromolecular brushes with thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) backbones and pendant poly(γ-benzyl-L-glutamate) (PBLG) side chains were synthesized by reversible addition–fragmentation chain transfer (RAFT) and ring-opening polymerization (ROP). Copolymers of NIPAM and N-acryloxysuccinimide (NAS) were synthesized by RAFT polymerization. Boc-protected amino groups were introduced into the backbone chains by substituting the NAS groups with N-Boc-ethylenediamine, and after removal of the Boc groups, amine groups were produced on the backbones. PBLG side chains were synthesized by ROP. Size exclusion chromatograph, 1H NMR and 13C NMR results indicated successful synthesis of well-defined brush macromolecules. The self-assembly of the macromolecules in aqueous solutions was investigated in this research. Depending on the backbone and side chain lengths, the brush macromolecules self-assemble into spherical micelles, worm-like structures and vesicles. Temperature exerted a significant effect on the morphology of the structures. At a temperature above lower critical temperature (LCST) of the PNIPAM backbone, the self-assembled structures aggregated together. The functionalization of PBLG side chains with 1-pyrenebutyric acid was also performed. The fluorescence properties and morphology of the functionalized brush macromolecules were investigated in this research.
Co-reporter:Dawei Chen, Dongxia Wu, Guochen Cheng and Hanying Zhao
Polymer Chemistry 2015 vol. 6(Issue 48) pp:8275-8283
Publication Date(Web):05 Oct 2015
DOI:10.1039/C5PY01299F
Hydrogels have found wide applications in many fields. Although plenty of mature preparation methodologies are available now, there is certainly a continuous impetus in developing new methods toward simplicity, adjustability and satisfying diverse emerging needs. In this paper, a novel and efficient approach for hydrogel preparation is proposed. Polyacrylamide (PAM) chains with pyridyl disulfide (PDS) side groups were synthesized by free-radical polymerization. Upon addition of a tiny amount of reductants to the aqueous solution of the synthesized copolymer, part of the PDS groups are reduced to free thiols, and the subsequent exchange reaction between thiol groups and PDS results in disulfide-crosslinked hydrogels. The rapid self-gelation process was monitored by in situ rheological measurements, and the network structures of the hydrogels were observed using a scanning electron microscope. It has been found that the mechanical properties and pore sizes of the hydrogels could be tuned by changing the polymer concentration and the amounts of the reductants added into the solution. The residual PDS groups in the hydrogels provide reaction sites for immobilization of biological functional molecules. Reduced glutathione and bovine serum albumin were successfully immobilized in the hydrogels, and the bioactivities of the hydrogels were measured in this research. The disulfide crosslinks are cleavable and the hydrogels are dissociated under reducing conditions, which indicates that the hydrogels may find potential applications in biological and medical fields.
Co-reporter:Jing Zhang, Yue Zhang, Feiyang Chen, Weiyao Zhang and Hanying Zhao
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 18) pp:12215-12221
Publication Date(Web):10 Apr 2015
DOI:10.1039/C5CP01560J
Salt-induced self-assemblies of poly(ethylene glycol-block-spiropyran methacrylate) (PEG-b-PSPMA) block copolymers were studied in this research. PEG-b-PSPMA block copolymers were dissolved in a 10:1 N,N-dimethyl-formamide (DMF)/water mixture. Upon ultraviolet light (UV) irradiation, the pendant spiropyran (SP) groups in the PSPMA blocks were isomerized into open merocyanine (MC) forms and the addition of inorganic salts (CuCl2, FeCl3 and Zn(CH3COO)2) induced micellization of PEG-b-PSPMA block copolymers in the solutions. In a salt-induced micelle, complexes formed by PSPMA and inorganic ions are in the cores and PEG chains are in the coronae. The reverse conversion of the isomers from MC form to SP form in the dark was studied by UV-vis, and the self-assembled aggregates were analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The self-assembly of PEG-b-PSPMA in aqueous medium was also investigated. In aqueous solution, amphiphilic PEG-b-PSPMA self-assembled into micelles with the hydrophobic PSPMA blocks in the cores and the hydrophilic PEG blocks in the coronae. Upon UV irradiation, the hydrophobic SP units in the cores were isomerized into hydrophilic MC forms. The MC isomers have the attractive MC–MC interactions, and the reversion from MC to SP in the dark is difficult. DLS and TEM results both demonstrated that the micelles self-assembled by PEG-b-PSPMA did not disassemble upon UV irradiation, due to the attractive MC–MC interactions in the cores.
Co-reporter:Shuzhe Zhu, Zhan-Wei Li, and Hanying Zhao
Langmuir 2015 Volume 31(Issue 14) pp:4129-4136
Publication Date(Web):March 26, 2015
DOI:10.1021/acs.langmuir.5b00526
Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition–fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol–disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S–Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation.
Co-reporter:Yue Zhang, Hanying Zhao
Polymer 2015 Volume 64() pp:277-284
Publication Date(Web):1 May 2015
DOI:10.1016/j.polymer.2015.02.005
•Amphiphilic mono-tethered SCNPs were prepared by intramolecular cross-linking reaction.•The amphiphilic mono-tethered SCNPs are able to lower the surface tension of water.•Surface tunable colloidal particles with SCNPs on the surfaces were prepared.In these years synthesis and applications of single-chain nanoparticles (SCNPs) have aroused great interests. In this article, the surfactant behaviors of amphiphilic mono-tethered SCNPs are reported. Amphiphilic mono-tethered SCNPs were prepared by intramolecular cross-linking reaction. In the mono-tethered SCNPs, there are disulfide bonds at the junction points between coil chains and the SCNPs. 1H NMR, size exclusion chromatography and transmission electron microscopy results demonstrated successful synthesis of the SCNPs. The amphiphilic mono-tethered SCNPs are able to lower the surface tension of water. Critical micelle concentration of the SCNPs in aqueous solution was determined. The mono-tethered SCNPs were used as surfactants in the suspension polymerization of styrene, and polystyrene colloidal particles with SCNPs on the surfaces were prepared. SCNPs on the colloidal particles were cleaved from the surfaces of the colloidal particles, leaving thiol groups on the surfaces. Pyridyl disulfide-modified PS colloidal particles were synthesized by a reaction between 2,2′-dipyridyl disulfide and the thiol groups on the PS particles. The pyridyl disulfide-modified colloidal particles were used as a platform for the preparation of functional colloidal particles. Herein, fluorescence-labeled colloidal particles were prepared by a reaction of thiol-modified fluorescein isothiocyanate and pyridyl disulfide groups on the particles.
Co-reporter:Lichao Sun and Hanying Zhao
Langmuir 2015 Volume 31(Issue 6) pp:1867-1873
Publication Date(Web):January 27, 2015
DOI:10.1021/la5040036
Lipid membrane fusion is a fundamental process in nature. In the fusion process two distinct bilayers merge the hydrophobic layers, and an interconnected structure is produced. In this research, the fusion of polymer membrane self-assembled by cleaved pinned micelles is investigated. Disulfide-tethered poly(tert-butyl acrylate-block-styrene) diblock copolymer brushes on the surfaces of silica particles were prepared by the “grafting to” or “grafting from” method. In acetone, the diblock copolymer brushes self-assemble into pinned micelles. Upon cleavage from the surfaces of the silica particles with n-tributylphosphine, the pinned micelles self-assemble into vesicles. In the meanwhile, thiol groups at the ends of the block copolymer brushes were produced in the cleavage reaction. Because of the oxidation of the thiol groups and the formation of the disulfide bonds, the vesicle structures are fused into bigger hollow structures and fiber-like structures. The further fusion of the fiber-like structures results in precipitation of the polymer from the solution.
Co-reporter:Lichao Sun, Jinchuan Liu and Hanying Zhao
Polymer Chemistry 2014 vol. 5(Issue 22) pp:6584-6592
Publication Date(Web):29 Jul 2014
DOI:10.1039/C4PY00938J
Micelles self-assembled by block copolymers are widely used in nanoscience and biomedical science. In the past few decades, much effort has been applied to the synthesis, characterization and applications of the polymeric micelles. However, previous research studies have paid less attention to the functionalization of coronae of the micelles. Herein, micelles with disulfide groups in the coronae were prepared and the micelles were used as a platform for functional modification reactions. Polystyrene-block-poly(oligo(ethylene glycol)monomethyl ether methacrylate)-block-poly(oligo(ethylene glycol)monomethyl ether methacrylate-co-2-((2-hydroxyethyl)disulfanyl)ethyl methacrylate), PS-b-PPEGMA-b-P(PEGMA-co-HDSMA), triblock copolymer was synthesized by RAFT polymerization. In aqueous solution, the triblock copolymer self-assembled into micelles with disulfides in the coronae. Upon cleavage of the disulfide bonds, thiol groups were produced in the coronae, and the micelles were able to undergo oxidation-induced aggregation. Hydroethyl disulfide groups in the PS-b-PPEGMA-b-P(PEGMA-co-HDSMA) triblock copolymer were converted to pyridyl disulfide groups by cleavage of the S–S bonds with tributylphosphine and reaction with dipyridyl disulfide. In PBS buffer solution, the modified triblock copolymer self-assembled into micelles with pyridyl disulfides in the coronae. The micelles were used as a platform for the preparation of glutathione or fluorescent group-decorated micelles. The antioxidant properties and the fluorescence properties of the functional micelles are reported in this paper. On the basis of this method, many different functional micelles can be prepared.
Co-reporter:Jianguo Wen, Jing Zhang, Yue Zhang, Yongfang Yang and Hanying Zhao
Polymer Chemistry 2014 vol. 5(Issue 13) pp:4032-4038
Publication Date(Web):11 Mar 2014
DOI:10.1039/C4PY00100A
In the field of materials science, one of the current challenges is to organize nanoparticles with various sizes, geometries and compositions into specific structures for constructing functional materials and devices. In this research, the self-assembly of the monotailed single-chain nanoparticles with different charge densities was investigated. Poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS) was synthesized by reversible addition–fragmentation chain transfer polymerization, and amphiphilic monotailed PDMAEMA single-chain nanoparticles were prepared by intramolecular cross-linking of PDMAEMA blocks. The cross-linking degree was controlled at about 20%. The surface charge densities on the single-chain nanoparticles were controlled by reactions of the single-chain nanoparticles with varying amounts of iodomethane. The surface charge density has a significant influence on the self-assembly of the monotailed single-chain nanoparticles. The monotailed single-chain nanoparticles made from PDMAEMA74-b-PS100 self-assemble into spherical micelles in aqueous solutions, and the average size of the micelles increases with the charge density. With an increase in the charge density, the morphology of the aggregates self-assembled by the monotailed single-chain nanoparticles changes from spherical micelles to vesicles, and to a mixture of worm-like cylinders and vesicles. In a cyclohexane–THF mixture, the monotailed single-chain nanoparticles made from PDMAEMA74-b-PS297 self-assemble into bunchy micelles, or a mixture of vesicles and large compound vesicles, depending on the charge densities.
Co-reporter:Yongfang Yang, Mao Li, Yulei Xie, Xiaohui Song, Xiongwei Qu, Hanying Zhao
Materials Letters 2014 Volume 118() pp:184-187
Publication Date(Web):1 March 2014
DOI:10.1016/j.matlet.2013.12.075
•We report a new method to prepare RGO–P2VP nanocomposites and CdS nanoparticles were protected by P2VP polymer brushes on RGO sheets.•TEM shows CdS nanoparticles were on the edges of RGO sheets.•RGO–CdS nanocomposites show strong optical limiting ability.CdS nanoparticles (NPs) on the edges of reduced graphene oxide (RGO) sheets are prepared. Carboxyl groups at the periphery of RGO sheets are converted to amine groups and a free-radical polymerization initiator is anchored to the RGO sheets. Poly(2-vinyl pyridine) (P2VP) brushes on RGO sheets are synthesized by in situ free-radical polymerization. Upon the addition of cadmium ions into the dispersion of RGO–P2VP nanocomposites in methanol, P2VP brushes form complexes with Cd2+, and CdS NPs protected by P2VP can be prepared upon the addition of sodium sulfide. A transmission electron microscope (TEM), Fourier Transform Infrared absorption spectra (FT-IR) and thermogravimetric analysis (TGA) are employed to characterize the composites. TEM results provide direct evidence for the location of CdS NPs at the periphery of RGO sheets. Fluorescence results indicate that there is a strong interaction between CdS NPs and RGO sheets. The synthesized composites show strong optical limiting ability.
Co-reporter:Guannan Liu;Dr. Jia Tian;Dr. Xu Zhang ; Hanying Zhao
Chemistry – An Asian Journal 2014 Volume 9( Issue 9) pp:2597-2603
Publication Date(Web):
DOI:10.1002/asia.201402379
Abstract
Materials with Janus structures are attractive for wide applications in materials science. Although extensive efforts in the synthesis of Janus particles have been reported, the synthesis of sub-10 nm Janus nanoparticles is still challenging. Herein, the synthesis of Janus gold nanoparticles (AuNPs) based on interface-directed self-assembly is reported. Polystyrene (PS) colloidal particles with AuNPs on the surface were prepared by interface-directed self-assembly, and the colloidal particles were used as templates for the synthesis of Janus AuNPs. To prepare colloidal particles, thiol-terminated polystyrene (PS-SH) was dissolved in toluene and citrate-stabilized AuNPs were dispersed in aqueous solution. Upon mixing the two solutions, PS-SH chains were grafted to the surface of AuNPs and amphiphilic AuNPs were formed at the liquid–liquid interface. PS colloidal particles decorated with AuNPs on the surfaces were prepared by adding the emulsion to excess methanol. On the surface, AuNPs were partially embedded in the colloidal particles. The outer regions of the AuNPs were exposed to the solution and were functionalized through the grafting of atom-transfer radical polymerization (ATRP) initiator. Poly[2-(dimethamino)ethyl methacrylate] (PDMAEMA) on AuNPs were prepared by surface-initiated ATRP. After centrifugation and dissolving the colloidal particles in tetrahydrofuran (THF), Janus AuNPs with PS and PDMAEMA on two hemispheres were obtained. In acidic pH, Janus AuNPs are amphiphilic and are able to emulsify oil droplets in water; in basic pH, the Janus AuNPs are hydrophobic. In mixtures of THF/methanol at a volume ratio of 1:5, the Janus AuNPs self-assemble into bilayer structures with collapsed PS in the interiors and solvated PDMAEMA at the exteriors of the structures.
Co-reporter:Jianguo Wen, Liang Yuan, Yongfang Yang, Li Liu, and Hanying Zhao
ACS Macro Letters 2013 Volume 2(Issue 2) pp:100
Publication Date(Web):January 11, 2013
DOI:10.1021/mz300636x
Shape amphiphiles with distinct shapes and amphiphilic properties can be used as fundamental building blocks in the fabrication of novel structures and advanced materials. In this research synthesis and self-assembly of monotethered single-chain nanoparticle shape amphiphiles are reported. Poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS) was synthesized by two-step reversible addition–fragmentation chain transfer (RAFT) polymerization. The PDMAEMA blocks were intramolecularly cross-linked by 1,4-diiodobutane (DIB) at significantly low concentrations, and PS-tethered PDMAEMA single-chain nanoparticles were prepared. Gel permeation chromatograph, 1H NMR and transmission electron microscopy results all indicated successful synthesis of the structures. The controlled self-assembly of the shape amphiphiles in selective solvents was investigated. Depending on the size of the single-chain nanoparticles, the shape amphiphiles self-assemble into strawberry-like micelles, a structure with single-chain nanoparticles in the corona and PS in the core, or vesicles in aqueous solutions. Similar to the self-assembled structures in aqueous solution, the morphology of the aggregates in methanol changes from micellar structure to vesicular structure with the decrease of the PDMAEMA single-chain nanoparticles size. In cyclohexane, the shape amphiphiles self-assemble into bunchy micelles with single-chain nanoparticles in the cores and linear PS in the coronae.
Co-reporter:Yue Zhang, Chuanzhuang Zhao, Li Liu, and Hanying Zhao
ACS Macro Letters 2013 Volume 2(Issue 10) pp:891
Publication Date(Web):September 20, 2013
DOI:10.1021/mz400286d
Mesoporous polymer nanoparticles containing pores with sizes ranging from 2 to 50 nm are attractive for wide applications, such as catalysis, drug delivery, and separations. On the basis of nanometer-sized phase separation and cleavage reaction in the micellar cores, polymeric micelles with mesoporous cores are prepared in this research. A triblock terpolymer, consisting of one hydrophilic block and two mutually incompatible hydrophobic blocks covalently connected by a redox-responsive disulfide linkage, self-assembles into multicompartment micelles, a type of micelle with subdivided hydrophobic cores, in aqueous solution. Due to the incompatibility, the two hydrophobic blocks have nanometer-sized phase separation in the micellar cores, one in the discontinuous phase and the other in the continuous phase. Upon cleavage of the disulfide linkage, the discontinuous phase is dissolved in a selective solvent, and micelles with mesoporous cores are obtained. The average pore size is around 3 nm. Functionalization of the mesopores with functional compounds and inorganic nanoparticles renders these micelles suited for wide applications.
Co-reporter:Jie Jin, Jun Wang, Pingchuan Sun and Hanying Zhao
Polymer Chemistry 2013 vol. 4(Issue 16) pp:4499-4505
Publication Date(Web):04 Jun 2013
DOI:10.1039/C3PY00516J
A poly(ethylene glycol)-b-poly(2-(2-bromoisobutyryloxy)ethyl methacrylate)-b-poly(tert-butyl acrylate) (PEG-b-PBIEM-b-PtBA) triblock copolymer self-assembles into micelles with an ATRP initiator residing at the interface. Interface cross-linked (ICL) micelles were prepared by interfacial atom transfer radical coupling (ATRC) reaction. The structure of the ICL micelles was characterized by 1H NMR, transmission electron microscopy (TEM) and dynamic light scattering. After hydrolysis of PtBA in the cores, hydrophilic ICL micelles with PEG in the coronae and poly(acrylic acid) in the cores were obtained. The hydrophilic ICL micelles were used as nanoreactors for the preparation of inorganic nanoparticles and nanocarriers for small molecular compounds. CdS quantum dots were prepared in the cores of the micelles. The morphology and optical properties of the quantum dots were studied by TEM and UV-vis, respectively. The hydrophilic ICL micelles were also used as nanocarriers for the absorption of methylene blue, a positively charged dye. The absorption kinetics study demonstrates that the cross-linked interfaces do not limit the diffusion of methylene blue molecules into the cores of the hydrophilic ICL micelles.
Co-reporter:Jie Jin, Jinchuan Liu, Xueming Lian, Pingchuan Sun and Hanying Zhao
RSC Advances 2013 vol. 3(Issue 19) pp:7023-7029
Publication Date(Web):04 Mar 2013
DOI:10.1039/C3RA40227D
Synthesis of cleavable PS brushes on the surface of silica particles was reported in this paper. Atom transfer radical polymerization (ATRP) initiator was anchored onto the surface of silica particles via dynamic imine bond, and PS brushes were prepared by surface ATRP of styrene. PS brushes could be cleaved from the surface of silica particles in the presence of trifluoroacetic acid. Based on the dynamic properties of imine bonds, pyrene-labeled silica particles were prepared through dynamic exchange reaction between PS brushes and 1-pyrenecarboxaldehyde. Moreover, silica particles with PS and fluorescein-labeled poly(methyl methacrylate) mixed polymer brushes were synthesized by dynamic exchange reaction. This research demonstrates that dynamic covalent chemistry provides an efficient method for the preparation of “dynamic” polymer brushes on silica particles.
Co-reporter:Junhua Liu, Guannan Liu, Mingming Zhang, Pingchuan Sun, and Hanying Zhao
Macromolecules 2013 Volume 46(Issue 15) pp:5974-5984
Publication Date(Web):August 1, 2013
DOI:10.1021/ma4007363
Materials with asymmetric structures are attractive for wide applications in chemistry and materials science. Two-dimensional Janus disks or nanosheets are particularly appealing because of the unique shape and the distinctive self-assembled structures. A facile and versatile method for the synthesis of amphiphilic Janus Laponite disks is proposed in this paper. Positively charged PS spheres were prepared by ATRP emulsion polymerization. Upon addition of aqueous dispersion of negatively charged Laponite disks into PS emulsions, the nanosized disks were adsorbed onto the surface of PS particles via electrostatic interaction. One side of a Laponite disk touches the surface of a colloidal particle, and the other side faces the medium. After addition of positively charged polymeric micelles or quaternized poly(2-(dimethylamino)ethyl methacrylate) (q-PDMAEMA) chains into the aqueous dispersions of the colloidal particles, the micelles or polymer chains were immobilized onto the Laponite disks, and Janus disks were produced on particle templates. After centrifugation and redispersion of the colloidal particles into a good solvent, amphiphilic Janus Laponite disks with PS chains on one side and hydrophilic q-PDMAEMA or polymeric micelles on the other side were obtained. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used to characterize the Janus disks. Self-assembly of the Janus disks at liquid–liquid interface and in selective solvents was investigated. Similar to small molecular surfactants, the amphiphilic Janus disks can self-assemble at liquid–liquid interface, resulting in a decrease of the interfacial tension and emulsification of oil droplets in water. In a THF–methanol mixture at a volume ratio of 1:6, PS brushes on the Janus disks collapse forming two-layer face-to-face stacks. The distinctive self-assembled structures were analyzed by TEM and AFM.
Co-reporter:Jinchuan Liu;Xueming Lian;Fei Zhao
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 17) pp:3567-3571
Publication Date(Web):
DOI:10.1002/pola.26760
Co-reporter:Yongfang Yang, Yulei Xie, Lichuan Pang, Mao Li, Xiaohui Song, Jianguo Wen, and Hanying Zhao
Langmuir 2013 Volume 29(Issue 34) pp:10727-10736
Publication Date(Web):July 29, 2013
DOI:10.1021/la401940z
Carboxyl groups at the periphery of reduced graphene oxide (RGO) sheets are converted to amine groups by reaction with N-hydroxysuccinimide and 1,3-diaminopropane, and a free-radical polymerization initiator is anchored to the RGO sheets. Poly(acrylamide) (PAM) polymer brushes on RGO sheets (RGO/PAM) are synthesized by in situ free-radical polymerization. The heavy metals, Pb(II), and the benzenoid compounds, methylene blue, (MB) were selected and adsorbed by RGO/PAM composites, and the adsorption capacity of RGO/PAM for Pb(II) and MB was measured. The experimental data of RGO/PAM isotherms for Pb(II) and MB followed the Langmuir isotherm model. The RGO/PAM displays adsorption capacities as high as 1000 and 1530 mg/g for Pb(II) and MB, respectively, indicating RGO/PAM is a good adsorbent for the adsorption of Pb(II) and MB. The adsorption kinetics of Pb(II) and MB onto RGO/PAM can be well fitted to the pseudo-second-order model. The adsorption processes of Pb(II) and MB onto RGO/PAM are spontaneous at 298, 308, and 318 K.
Co-reporter:Jie Jin, Mingming Zhang, Qingqing Xiong, Pingchuan Sun and Hanying Zhao
Soft Matter 2012 vol. 8(Issue 47) pp:11809-11816
Publication Date(Web):28 Sep 2012
DOI:10.1039/C2SM26362A
Poly(ethylene glycol-block-2-hydroxyethyl methacrylate-block-tert-butyl acrylate) (PEG-b-PHEMA-b-PtBA) triblock copolymer was synthesized by the sequential atom transfer radical polymerization (ATRP) of HEMA and tBA using an ATRP initiator terminated PEG (PEG-Br) as the macroinitiator. Azide groups were introduced to the short mid-blocks by reactions of the triblock copolymer with 2-bromoisobutyryl bromide and sodium azide. In aqueous solution, the triblock copolymer self-assembled into micelles with azide groups at the interfaces. Reactive polymeric micelles with reversible addition–fragmentation chain transfer agents (RAFT CTAs) at the interfaces were prepared by a click cross-linking reaction between dialkynetrithiocarbonate and the azide groups. FT-IR, 1H NMR, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize the interface cross-linked (ICL) micelles and the grafting of the RAFT CTAs to the interfaces. Polymeric micelles with PEG–poly(N-isopropylacrylamide) (PNIPAM) mixed coronal chains were prepared by the in situ RAFT polymerization of NIPAM at the interfaces. The TEM results demonstrate that the mixed coronal chains have nano-sized phase separation on the surfaces of the micelles. The use of the polymeric micelles as particulate emulsifiers was also investigated in this research. These ICL micelles with mixed coronal chains produce relatively fine 1-undecanol-in-water (o/w) emulsions compared to emulsions stabilized by the PEG homopolymer under the same conditions.
Co-reporter:Liang Yuan, Jingchuan Liu, Jianguo Wen, and Hanying Zhao
Langmuir 2012 Volume 28(Issue 30) pp:11232-11240
Publication Date(Web):July 5, 2012
DOI:10.1021/la3020817
An amphiphilic block copolymer comprising poly(ethylene glycol) (PEG) and poly(2-(methacryloyl)oxyethyl-2′-hydroxyethyl disulfide) (PMAOHD) blocks was synthesized by atom transfer radical polymerization (ATRP). Pyrenebutyric acid was conjugated to the block copolymer by esterification, and a block copolymer with pendant disulfide bonds and pyrenyl groups (PEG-b-P(MAOHD-g-Py)) was obtained. 1H NMR and gel permeation chromatography (GPC) results demonstrated the successful synthesis of the block copolymer. The cleavage of the disulfide bonds and the degrafting of the pyrenyl groups were investigated in THF and a THF/methanol mixture. Fluorescence spectroscopy, GPC, and 1H NMR results demonstrated fast cleavage of the disulfide bonds by Bu3P in THF. Fluorescence results showed the ratio of the intensity of the excimer peak to the monomer peak decreased rapidly within 20 min. GPC traces of the block copolymer moved to a long retention time region after addition of Bu3P, indicating the cleavage of the disulfide bonds and the degrafting of the pyrenyl groups. PEG-b-P(MAOHD-g-Py) can self-assemble into micelles with poly(MAOHD-g-Py) cores and PEG coronae in a mixture of methanol and THF (9:1 by volume). The dissociation of the micelles in the presence of Bu3P was investigated. After cleavage of the disulfide bonds in the micellar cores, a pyrene-containing small molecular compound and a block copolymer with pendant thiol groups were produced. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and 1H NMR were employed to track the dissociation of the polymeric micelles. All the techniques demonstrated the dissociation of the micelles and the fast release of pyrenyl groups from the micelles.
Co-reporter:Jia Tian, Liang Yuan, Mingming Zhang, Fan Zheng, Qingqing Xiong, and Hanying Zhao
Langmuir 2012 Volume 28(Issue 25) pp:9365-9371
Publication Date(Web):May 23, 2012
DOI:10.1021/la301453n
Amphiphilic gold nanoparticles (AuNPs) were produced at liquid–liquid interface via ligand exchange between hydrophilic AuNPs and disulfide-containing polymer chains. By using oil droplets as templates, hybrid hollow capsules with AuNPs on the surfaces were obtained after interfacial cross-linking polymerization. The volume ratio of toluene to water exerts an important effect on the size of capsules. The average size of the capsules increases with the volume ratio. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the hollow structures. In this research, not only one-component but also multicomponent hollow capsules were prepared by copolymerization of acrylamide and hybrid AuNPs at liquid–liquid interface. Because of the improvement in hydrophilicity of the hollow capsules, the average size of multicomponent capsules is bigger than one-component ones in aqueous solution.
Co-reporter:Xueming Lian, Fei Zhao, Yuan Li, Jun Wang, Siming Li, Hanying Zhao
Polymer 2012 Volume 53(Issue 9) pp:1906-1914
Publication Date(Web):17 April 2012
DOI:10.1016/j.polymer.2012.03.004
The self-assembly and photophysical properties of a triblock copolymer with complex mid-block in THF and aqueous solution were investigated in this research. Poly(poly(ethylene glycol) methyl ether methacrylate)-block-poly(2-(dimethylamino ethyl methacrylate)-block- poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA–b–PDMAEMA–b–PPEGMA) triblock copolymer was synthesized by subsequent atom transfer radical polymerizations (ATRP) of DMAEMA and PEGMA. The PDMAEMA blocks were quaternized by a reaction with iodomethane. The complex of the positively charged PDMAEMA chain unit and sodium salt of 1-pyrenebutyric acid was prepared by mixing equimolar amount of the two components in THF/water mixture. Transmission electron microscopy and fluorescence technique results show that the triblock copolymer chains self-assemble into micelles in THF at high concentration. The critical aggregation concentration (CAC) of the triblock copolymer in THF determined by fluorescence technique is 6.8 × 10−5 M. The triblock copolymer was also able to self-assemble into micelles in water. The value of CAC of the triblock copolymer in water is 2.0 × 10−5 M. The photophysical properties and self-assembly structures of the triblock copolymer in aqueous solutions were influenced by added sodium chloride. After salt addition, a transition of the assembled structures from micelles to hollow structures was observed.
Co-reporter:Yongfang Yang;Xiaohui Song;Liang Yuan;Mao Li;Jinchuan Liu;Rongqin Ji
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 2) pp:329-337
Publication Date(Web):
DOI:10.1002/pola.25036
Abstract
Preparation and characterization of poly(N-isopropylacrylamide) (PNIPAM) polymer brushes on the surfaces of reduced graphene oxide (RGO) sheets based on click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization was reported. RGO sheets prepared by thermal reduction were modified by diazonium salt of propargyl p-aminobenzoate, and alkyne-functionalized RGO sheets were obtained. RAFT chain transfer agent (CTA) was grafted to the surfaces of RGO sheets by click reaction. PNIPAM on RGO sheets was prepared by RAFT polymerization. Fourier transform-infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM) results all demonstrated that RAFT CTA and PNIPAM were successfully produced on the surfaces of RGO sheets. Nanosized PNIPAM domains on RGO sheets were observed on TEM. Micro-DSC result indicated that in aqueous solution PNIPAM on RGO sheets presented a lower critical solution temperature at 33.2 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Jia Tian, Fan Zheng, Qingjiao Duan and Hanying Zhao
Journal of Materials Chemistry A 2011 vol. 21(Issue 42) pp:16928-16934
Publication Date(Web):26 Jul 2011
DOI:10.1039/C1JM11384D
Polystyrene (PS) with pendant hydrophilic gold nanoparticles (AuNPs) were synthesized by free radical copolymerization of styrene and AuNPs monomer at a liquid–liquid interface. The hybrid polymers can self-assemble into ordered structures in aqueous solutions. The hydrophilicity of the hybrid polymers plays a key role in the self-assembly of the polymers. A decrease in the number of hydrophilic AuNPs results in a transition from a micellar structure to a vesicular structure. After grafting of hydrophilic poly(N-vinyl pyrrolidone) chains to the pendant AuNPs, the self-assembly changes from a vesilcular structure to a core–shell-corona structure. The hybrid polymers and PS-coated Fe3O4 nanoparticles can self-assemble into vesicles with PS and PS-coated Fe3O4 nanoparticles in the walls and AuNPs in the coronae, and the size of the vesicles is determined by the number of pendant AuNPs.
Co-reporter:Jie Jin, Jia Tian, Xueming Lian, Pingchuan Sun and Hanying Zhao
Soft Matter 2011 vol. 7(Issue 23) pp:11194-11202
Publication Date(Web):14 Oct 2011
DOI:10.1039/C1SM06225E
In this manuscript in situRAFT polymerization inside reactive triblock copolymer micelles were reported. Poly(ethylene glycol)-block-poly(2-hydroxyethyl methacrylate)-block-poly(tert-butyl acrylate) (PEG-b-PHEMA-b-PtBA) triblock copolymer was synthesized through two-step ATRP of HEMA and tBA by using ATRP initiator terminated PEG as macroinitiator. The pendant azide groups were introduced to the short mid-blocks by reactions of the triblock copolymer with 2-bromoisobutyryl bromide and sodium azide, respectively. Click reaction between the azido-modified triblock and dialkynetrithiocarbonate results in the formation of the reactive micelles with cross-linked cores and PtBA/PEG coronae. The size of the micellar aggregates is determined by initial polymer concentration. The entrapped reversible addition-fragmentation chain transfer (RAFT) agent molecules in the cores were used in RAFT polymerization of N-isopropylacrylamide (NIPAM). After RAFT polymerization, polymeric micelles with cross-linked PNIPAM cores and PEG/PtBA coronae were obtained. FTIR, 1H NMR, dynamic light scattering and transmission electron microscopy were used to characterize the structures of the micelles before and after RAFT polymerization. The degradation of the micelles was also investigated in this research. This type of micelles can be used as a platform for RAFT polymerization.
Co-reporter:Jie Jin, Dongxia Wu, Pingchuan Sun, Li Liu, and Hanying Zhao
Macromolecules 2011 Volume 44(Issue 7) pp:2016-2024
Publication Date(Web):March 7, 2011
DOI:10.1021/ma102398c
Poly(ε-caprolactone)-block-poly(ethylene glycol)-block-poly(ε-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymers with biotin groups at the junction points were synthesized based on a combination of click chemistry and ring-opening polymerization (ROP). Alkyne-functionalized PCL-b-PEG-b-PCL triblock copolymers were synthesized by using alkyne-functionalized PEG as macroinitiators in ROP of ε-caprolactone. Click chemistry was employed in the synthesis of the biotinylated triblock copolymers. Gel permeation chromatography and 1H NMR results all indicated successful synthesis of well-defined triblock copolymers. The triblock copolymer chains can self-assemble into micelles in aqueous solution. The PCL blocks form the cores of the micelles and the hydrophilic PEG blocks form the coronae. The biotin moieties distribute at the interface of the micelles. Upon addition of avidin to the micellar solution, micelles aggregated together forming micellar aggregates due to the interaction between avidin and biotin. The avidin/HABA competitive binding assay also proved the bioavailability of the biotinylated micelles to avidin.
Co-reporter:Qingjiao Duan, Jian Zhang, Jia Tian, and Hanying Zhao
Langmuir 2011 Volume 27(Issue 21) pp:13212-13219
Publication Date(Web):September 19, 2011
DOI:10.1021/la203180j
A simple approach to the synthesis of clay–silica nanocomposites is presented. Silica nanorings on the edges of clay sheets were synthesized by using a modified Stöber method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and fluorescence spectroscopy were employed to characterize the prepared nanocomposites. TEM results show that the average size of the nanorings increases with the growth of silica. XRD results indicate that the layered structures of clay can be found in the nanocomposite and the growth of silica nanorings expands the d spacing of clay platelets. The mechanism of the formation of the nanorings is discussed. The preparation of polystyrene (PS) brushes on the surfaces of silica nanorings by atom-transfer radical polymerization is also reported. The polymer nanocomposite with negatively charged clay surfaces and hydrophobic polymer brushes on the silica nanorings can be used in Pickering emulsions, and PS colloidal particles with clay–silica on the surfaces were prepared.
Co-reporter:Jia Tian ; Fan Zheng
The Journal of Physical Chemistry C 2011 Volume 115(Issue 8) pp:3304-3312
Publication Date(Web):February 9, 2011
DOI:10.1021/jp111355c
Polystyrene (PS) brushes on Fe3O4 nanoparticles were prepared by reversible addition−fragmentation chain transfer (RAFT) polymerization, and after reduction reaction PS brushes with terminal thiol groups (HS−PS−Fe3O4NPs) were obtained. Citrate-stabilized gold nanoparticles (AuNPs) were prepared in aqueous solution and HS−PS−Fe3O4NPs were dispersed in toluene. Upon mixing of the aqueous solution with the toluene solution, a stable O/W emulsion was prepared. Hydrophilic gold nanoparticles interacted with hydrophobic Fe3O4 nanoparticles via Au−S interaction, and amphiphilic nanoparticle complexes were formed at the liquid−liquid interface. The stability of the emulsion was achieved by the formation of the amphiphilic nanoparticle complexes. Upon transfer of the emulsion into excess methanol, core−shell structures with Fe3O4−nanoparticle cores and gold−nanoparticle coronae were fabricated. In this manuscript, the influences of the weight ratio of HS−PS−Fe3O4NPs to AuNP and volume ratio of toluene to water on the self-assembly structures were also investigated.
Co-reporter:Xueming Lian, Jie Jin, Jia Tian and Hanying Zhao
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 8) pp:2261
Publication Date(Web):July 29, 2010
DOI:10.1021/am1003156
Thermoresponsive nanohydrogels cross-linked by gold nanoparticles (AuNPs) were prepared by 1,3-dipolar cycloaddition reactions and in situ reversible addition−fragmentation chain-transfer (RAFT) polymerization. In order to synthesize thermoresponsive nanohydrogels, AuNPs decorated with azide groups (AuNPs-N3) were prepared through ligand exchange. Click reactions between AuNPs-N3 and dialkynetrithiocarbonate yielded cross-linked AuNP aggregates. The size and cross-linking density of AuNP aggregates increased with the molar ratio of acetylene groups to azide groups. After click reactions, the absorption maximum of the plasmon band of AuNPs red-shifted to a long wavelength. Thermoresponsive nanohydrogels were prepared by in situ RAFT polymerization of N-isopropylacrylamide (NIPAM) using trithiocarbonate in the cross-linked AuNP aggregates as chain-transfer agents. The thermoresponsive nanohydrogels presented a low critical solution temperature at around 32 °C due to the “coil-to-globule” transition of connecting PNIPAM chains in the nanohydrogels. The size of the thermoresponsive nanohydrogels was determined by the molar ratio of acetylene groups to azide groups.Keywords: click reaction; gold nanoparticles; nanohydrogel; RAFT polymerization
Co-reporter:Dongxia Wu;Xiaohui Song;Tao Tang
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 2) pp:443-453
Publication Date(Web):
DOI:10.1002/pola.23804
Abstract
Well-defined macromolecular brushes with poly(N-isopropyl acrylamide) (PNIPAM) side chains on random copolymer backbones were synthesized by “grafting from” approach based on click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization. To prepare macromolecular brushes, two linear random copolymers of 2-(trimethylsilyloxy)ethyl methacrylate (HEMA-TMS) and methyl methacrylate (MMA) (poly(MMA-co-HEMA-TMS)) were synthesized by atom transfer radical polymerization and were subsequently derivated to azide-containing polymers. Novel alkyne-terminated RAFT chain transfer agent (CTA) was grafted to polymer backbones by copper-catalyzed 1,3-dipolar cycloaddition (azide-alkyne click chemistry), and macro-RAFT CTAs were obtained. PNIPAM side chains were prepared by RAFT polymerization. The macromolecular brushes have well-defined structures, controlled molecular weights, and molecular weight distributions (Mw/Mn ≦ 1.23). The RAFT polymerization of NIPAM exhibited pseudo-first-order kinetics and a linear molecular weight dependence on monomer conversion, and no detectable termination was observed in the polymerization. The macromolecular brushes can self-assemble into micelles in aqueous solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 443–453, 2010
Co-reporter:Jia Tian, Jie Jin, Fan Zheng and Hanying Zhao
Langmuir 2010 Volume 26(Issue 11) pp:8762-8768
Publication Date(Web):January 19, 2010
DOI:10.1021/la904519j
Colloidal particles with polystyrene (PS) cores and gold nanoparticle (AuNP) coronae were prepared on the basis of the self-assembly of AuNP’s and PS. Citrate-stabilized AuNP’s were dispersed in aqueous solution, and PS with thiol terminal groups (PS-SH) was dissolved in toluene. A stable emulsion was obtained by mixing the two solutions. Optical microscope images indicate that after grafting of PS-SH to the citrate-stabilized AuNP’s at liquid−liquid interface, the interfacial tension is reduced and the average size of toluene droplets in the emulsion decreases. Transmission electron microscope (TEM) results also prove the grafting of PS-SH to AuNP’s and the location of the hybrid nanoparticles at the liquid−liquid interface. Colloidal particles with PS cores and AuNP coronae were prepared by adding the emulsion to excess methanol. The weight ratio of PS-SH to AuNP exerts a significant effect on the size of colloidal particles. TEM and dynamic light scattering results both indicate that the size of colloidal particles increases with the weight ratio. The application of the core−shell-structured colloidal particles to protein separation was also investigated in this research. Colloidal particles with PS-coated magnetic nanoparticles in the cores were also prepared by this strategy.
Co-reporter:Chuanzhuang Zhao, Dongxia Wu, Xueming Lian, Yue Zhang, Xiaohui Song and Hanying Zhao
The Journal of Physical Chemistry B 2010 Volume 114(Issue 19) pp:6300-6308
Publication Date(Web):April 26, 2010
DOI:10.1021/jp1007494
An amphiphilic asymmetric comb polymer with pendant pyrene groups and poly(N-isopropylacrylamide) (PNIPAM) side chains was synthesized based on click chemistry and reversible addition−fragmentation chain transfer polymerization. Gel permeation chromatography, FTIR, and 1H NMR results all indicated successful synthesis of a well-defined comb polymer. The photophysical properties and self-assembly of the polymer in solution were studied by UV−vis spectroscopy, fluorescence technique, and transmission electron microscopy. The intensity ratio of the excimer peak (IE) to the monomer peak (IM) of the comb polymer in THF was used to monitor the formation of inter- or intramolecular excimers. At low polymer concentration, the value of IE/IM kept unchanged, indicating the formation of intramolecular excimer; at high polymer concentration, the value increased rapidly with concentration because of the formation of intermolecular excimer. The change of the intensity ratio of the first to the third vibronic band (I1/I3) on the monomer emission of the comb polymer also proved the association of the pendant pyrene groups in THF at high polymer concentration. In aqueous solution, the comb polymer chains self-assembled into vesicles with pyrene groups in the walls and PNIPAM side chains in the coronae. The value of the critical aggregation concentration of the polymer was determined by fluorescence technique. Temperature exerted a significant effect on the size and morphology of the vesicles. At a temperature above the lower critical solution temperature (LCST) of PNIPAM, PNIPAM brushes in the coronae of vesicles collapsed on the surface of the structures forming nanosized domains, and vesicles with smaller size were obtained. Fluorescence quenching experiments indicated that the collapsed PNIPAM chains protected a part of pyrene groups from being quenched by nitromethane at a temperature above the LCST of PNIPAM.
Co-reporter:Xueming Lian, Dongxia Wu, Xiaohui Song, and Hanying Zhao
Macromolecules 2010 Volume 43(Issue 18) pp:7434-7445
Publication Date(Web):August 25, 2010
DOI:10.1021/ma101452h
Two well-defined amphiphilic asymmetric macromolecular brushes, one bearing hydrophilic poly(ethylene glycol) (PEO) and hydrophobic polystyrene (PS) side chains on poly(glycidyl methacrylate) (PGMA) backbone and the other bearing pendant PEO and poly(styrene-block-N-isopropylacrylamide) (PS-b-PNIPAM) block copolymer side chains, were synthesized by grafting from approach based on a combination of click chemistry and in situ reversible addition−fragmentation chain transfer (RAFT) polymerization. PGMA backbone was synthesized by atom transfer radical polymerization (ATRP), and a polymer backbone with pendant hydroxyl and azide groups (PGMA−OH/N3) was obtained after ring-opening reaction of the epoxide rings on PGMA. RAFT chain transfer agent (CTA) was introduced to the polymer backbone by facile click reaction between alkyne-terminated RAFT CTA and PGMA−OH/N3. PEO side chains were grafted onto the polymer backbone by esterification between carboxyl end group of PEO and hydroxyl group on the polymer backbone; PS or PS-b-PNIPAM side chains were prepared by RAFT polymerization. Gel permeation chromatograph, FTIR and 1H NMR results all indicated successful synthesis of well-defined amphiphilic asymmetric macromolecular brushes. The self-assembly of the macromolecular brushes in solutions was also investigated in this research. Asymmetric macromolecular brushes with PEO and PS side chains self-assembled into vesicle structures in methanol. PS side chains were in the walls of the vesicles, and PEO side chains were in the coronae. The average size of the structure increased with PS chain length. The macromolecular brushes with PEO and PS-b-PNIPAM block copolymer side chains were able to self-assemble into vesicles in aqueous solution. Temperature exerted a significant effect on the morphology of the structures. At a temperature above lower critical solution temperature (LCST) of PNIPAM, the size of the vesicles decreased due to the shrinking of PNIPAM blocks in the corona.
Co-reporter:Jian Zhang, Xiaojuan Wang, Dongxia Wu, Li Liu and Hanying Zhao
Chemistry of Materials 2009 Volume 21(Issue 17) pp:4012
Publication Date(Web):August 7, 2009
DOI:10.1021/cm901437n
Janus silica particles decorated with biotin molecules and poly(ethylene oxide) PEO chains on two hemispheres were prepared by two-step click reactions. Polystyrene (PS) particles coated with azide modified silica particles were used as templates. On the PS surface one hemisphere of a silica particle was exposed to the solvent and the other one was embedded in PS. The alkynated biotin molecules were grafted onto the exposed side of the silica particle by click reaction. After removal of PS, the embedded part of the silica particle was released, and alkynated PEO chains were grafted to the particle by click reaction. FT-IR, TGA, and TEM were employed to characterize the Janus particles. The Janus particles show strong interaction with avidin.
Co-reporter:Xiwen Zhang, Yongfang Yang, Jia Tian and Hanying Zhao
Chemical Communications 2009 (Issue 25) pp:3807-3809
Publication Date(Web):26 May 2009
DOI:10.1039/B906967D
Polystyrene (PS) with pendant gold nanoparticles and PS-coated Fe3O4nanoparticles self-assemble into vesicle structures with PS and PS-coated Fe3O4nanoparticles in the wall and gold nanoparticles in the shell.
Co-reporter:Dongxia Wu;Chuanzhuang Zhao;Jia Tian
Polymer International 2009 Volume 58( Issue 11) pp:1335-1340
Publication Date(Web):
DOI:10.1002/pi.2670
Abstract
BACKGROUND: Molecular brushes are types of macromolecules with densely grafted side chains on a linear backbone. The synthesis of macromolecular brushes has stimulated much interest due to their great potential in applications in various fields. Poly(L-lactide)–poly(ethylene glycol) methyl ether methacrylate (PLLA-PEOMA) comb-block-comb molecular brushes with controlled molecular weights and narrow molecular weight distributions were successfully synthesized based on a combination of activator generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) and ring-opening polymerization. The synthetic route is a combination of the ‘grafting through’ method for AGET ATRP of the PEOMA comb block and the ‘grafting from’ method for the synthesis of the PLLA comb block. Poly(2-hydroxyethyl methacrylate) (PHEMA) was synthesized by ATRP, and PLLA side chains and PEOMA side chains were grown from the backbones and the terminal sites of PHEMA, respectively.
RESULTS: The number-average degrees of polymerization of PLLA chains and poly[poly(ethylene glycol) methyl ether methacrylate] (PPEOMA) comb blocks were determined using 1H NMR spectroscopy, and the apparent molecular weights and molecular weight distributions of the brush molecules were measured using gel permeation chromatography. The crystallization of the components in the comb-block-comb copolymers was also investigated. The crystallization of PLLA side chains is influenced by PLLA chain length and the content of PPEOMA in the molecular brushes. The comb-block-comb copolymer composed of hydrophobic PLLA and hydrophilic PEOMA can self-assemble into a micellar structure in aqueous solution.
CONCLUSION: A combination of AGET ATRP and ring-opening polymerization is an efficient method to prepare well-defined comb-block-comb molecular brushes. The physical properties of the molecular brushes are closely related to their structures. Copyright © 2009 Society of Chemical Industry
Co-reporter:Yani Wu;Jian Zhang
Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 6) pp:1535-1543
Publication Date(Web):
DOI:10.1002/pola.23256
Abstract
In this study, we describe a new strategy for producing narrowly dispersed functional colloidal particles stabilized by a nanocomposite with hydrophilic clay faces and hydrophobic polystyrene (PS) brushes on the edges. This method involves preparation of polymer brushes on the edges of clay layers and Pickering suspension polymerization of styrene in the presence of the nanocomposites. PS brushes on the edges of clay layers were prepared by atom transfer radical polymerization. X-ray diffraction and thermogravimetric analysis results indicated that PS chains were grafted to the edges of clay platelets. Transmission electron microscope results showed that different morphologies of clay-PS particles could be obtained in different solvents. In water, clay-PS particles aggregated together, in which PS chains collapsed forming nanosized hydrophobic domains and hydrophilic clay faces stayed in aqueous phase. In toluene, clay-PS particles formed face-to-face structure. Narrowly dispersed PS colloidal particles stabilized by clay-PS were prepared by suspension polymerization. Because of the negatively charged clay particles on the surface, the zeta potential of the PS colloidal particles was negative. Positively charged poly(2-vinyl pyridine) (P2VP) chains were adsorbed to the surface of PS colloidal particles in aqueous solution at a low pH value, and gold nanoparticles were prepared in P2VP brushes. Such colloidal particles may find important applications in a variety of fields including waterborne adhesives, paints, catalysis of chemical reactions, and protein separation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1535–1543, 2009
Co-reporter:Yongfang Yang, Jie Wang, Jian Zhang, Jinchuan Liu, Xinglin Yang and Hanying Zhao
Langmuir 2009 Volume 25(Issue 19) pp:11808-11814
Publication Date(Web):July 14, 2009
DOI:10.1021/la901441p
Exfoliated graphite oxide (GO) sheets with hydroxyl groups and amine groups on the surface were prepared by modification of graphite. Atom transfer radical polymerization (ATRP) initiator molecules were grafted onto the GO sheets by reactions of 2-bromo-2-methylpropionyl bromide with hydroxyl groups and amine groups. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) chains on the surface of GO sheets were synthesized by in-situ ATRP. X-ray photoelectron spectroscopy, thermogravimetric analysis, and transmission electron microscopy (TEM) results all demonstrated that polymer chains were successfully produced. After grafting of PDMAEMA, the dispersity of GO sheets in solvents was improved significantly. Poly(ethylene glycol dimethacrylate-co-methacrylic acid) particles were deposited on GO sheets via hydrogen bonding between MAA units on polymer particles and amine groups of PDMAEMA. TEM and scanning electron microscopy were used to characterize the structure of the nanocomposites.
Co-reporter:Jian Zhang, Jie Jin and Hanying Zhao
Langmuir 2009 Volume 25(Issue 11) pp:6431-6437
Publication Date(Web):March 20, 2009
DOI:10.1021/la9000279
Amphiphilic Janus silica particles with hydrophobic polystyrene (PS) and hydrophilic poly(sodium methacrylate) (PSMA) brushes on two hemispheres were prepared at the liquid−liquid interface by surface-initiated polymerization. After introduction of free-radical initiator modified silica particles into a mixture of styrene and water, the silica particles were adsorbed at the liquid−liquid interface. One hemisphere of a silica particle is immersed in aqueous phase, and the other one is in styrene phase. After initiation at an elevated temperature, PSMA chains grow on one hemisphere and PS chains grow on the other one. Thermogravimetric analysis and infrared spectra results confirmed the grafting of polymer brushes on the surfaces. Transmission electron microscopy was used to characterize the asymmetric surface structure and aggregation structure of the Janus particles.
Co-reporter:Xiwen Zhang, Li Liu, Jia Tian, Jian Zhang and Hanying Zhao
Chemical Communications 2008 (Issue 48) pp:6549-6551
Publication Date(Web):11 Nov 2008
DOI:10.1039/B815778B
The use of stoichiometrically functionalized gold nanoparticles (AuNPs) as building units in polymerization reaction is described; the obtained copolymers, comprised of AuNPs and polystyrene, behave differently in various solvents, micellar structures with PS cores and AuNPs corona are obtained in water.
Co-reporter:Xiwen Zhang, Xueming Lian, Li Liu, Jian Zhang and Hanying Zhao
Macromolecules 2008 Volume 41(Issue 21) pp:7863-7869
Publication Date(Web):October 14, 2008
DOI:10.1021/ma801405j
Comb copolymers comprising hydrophilic poly(ethylene glycol) comb chains and hydrophobic fluorescent pyrenyl groups were synthesized by a combination of reversible addition−fragmentation chain transfer polymerization and click chemistry. FTIR, 1H NMR, and gel permeation chromatograph results indicated successful synthesis of the comb copolymers with well-defined structures. The self-assembly of comb copolymers in aqueous solution was investigated. The comb copolymers with different compositions were able to self-assemble into micellar structure or vesicle structure. The pendant pyrenyl groups on the comb copolymer chains had electron donor−acceptor (EDA) interaction with 4-bromo-N,N′-dimethylaniline (BDMA). Vesicle structure formed by BDMA and comb copolymer via EDA interaction was observed by transmission electron microscopy. The fluorescence properties of the supramolecular structure were studied in detail.
Co-reporter:Kaiqiang Chen, Dehai Liang, Jia Tian, Linqi Shi and Hanying Zhao
The Journal of Physical Chemistry B 2008 Volume 112(Issue 40) pp:12612-12617
Publication Date(Web):September 13, 2008
DOI:10.1021/jp803216s
Herein we describe a new strategy for producing micelles with mixed coronal chains. This method involves attachment of an atom transfer radical polymerization (ATRP) initiator at the interface of a micelle and preparation of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes at the interface by a “grafting from” method. Poly(ethylene glycol)-block-polystyrene (PEG-b-PS) diblock copolymer was achieved by ATRP. After the sulfonation reaction PS blocks were partly sulfonated. In aqueous solution at low pH the sulfonated block copolymer self-assembled into micelles with PS cores and PEG coronae and sodium 4-styrenesulfonate groups were distributed at the interfaces of the micelles. An ATRP initiator consisting of a quaternary ammonium salt moiety and a 2-bromo-2-methyl propionate moiety was ion exchanged onto the interface of the micelle. ATRP of DMAEMA was initiated at the interface, and micelles with PEG/PDMAEMA mixed coronal chains were prepared by ATRP. The structures of the micelles were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and zeta potential measurements. The size and morphology of the micelles were controlled by pH in aqueous solution. At high pH, PDMAEMA brushes collapse, forming nanodomains on the surface of the micelles. PDMAEMA brushes in the coronae of the micelles could be used as a template for preparation of gold nanoparticles.
Co-reporter:Jian Zhang;Chuanzhuang Zhao;Yongfang Yang
Journal of Polymer Science Part A: Polymer Chemistry 2007 Volume 45(Issue 22) pp:5329-5338
Publication Date(Web):4 OCT 2007
DOI:10.1002/pola.22278
Polystyrene (PS) and poly(methyl methacrylate) (PMMA) mixed polymer brushes on the surface of clay layers were prepared by using in situ free radical polymerization. Free radical initiator molecules with two quaternary ammonium groups at both ends were intercalated into the interlayer spacing of clay layers. The amount of polymer brushes grafted on the surface of clay layers can be controlled by controlling the polymerization time. Thermogravimetric analysis, X-ray diffraction, and high-resolution transmission electron microscope results indicated successful preparation of the mixed polymer brushes on the surface of clay layers. The kinetics of the grafting of the monomers was also studied. The mixed polymer brushes on the surface of clay layers were used as compatibilizers in blends of PS and PMMA. In the blends, the intercalated clay particles tend to locate at the interface of two phases reducing the interfacial tension. In the meanwhile, PMMA homopolymer chains tend to intercalate into clay layers. The driving force for the intercalation is the compatibility between homo-PMMA chains and PMMA brushes on the surface of clay layers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5329–5338, 2007
Co-reporter:Roy L. Moodie
Science 1921 Vol 53(1368) pp:259-260
Publication Date(Web):18 Mar 1921
DOI:10.1126/science.53.1368.259-b
Co-reporter:Jia Tian, Fan Zheng, Qingjiao Duan and Hanying Zhao
Journal of Materials Chemistry A 2011 - vol. 21(Issue 42) pp:NaN16934-16934
Publication Date(Web):2011/07/26
DOI:10.1039/C1JM11384D
Polystyrene (PS) with pendant hydrophilic gold nanoparticles (AuNPs) were synthesized by free radical copolymerization of styrene and AuNPs monomer at a liquid–liquid interface. The hybrid polymers can self-assemble into ordered structures in aqueous solutions. The hydrophilicity of the hybrid polymers plays a key role in the self-assembly of the polymers. A decrease in the number of hydrophilic AuNPs results in a transition from a micellar structure to a vesicular structure. After grafting of hydrophilic poly(N-vinyl pyrrolidone) chains to the pendant AuNPs, the self-assembly changes from a vesilcular structure to a core–shell-corona structure. The hybrid polymers and PS-coated Fe3O4 nanoparticles can self-assemble into vesicles with PS and PS-coated Fe3O4 nanoparticles in the walls and AuNPs in the coronae, and the size of the vesicles is determined by the number of pendant AuNPs.
Co-reporter:Jin-Tao Wang, Yanhang Hong, Xiaotian Ji, Mingming Zhang, Li Liu and Hanying Zhao
Journal of Materials Chemistry A 2016 - vol. 4(Issue 25) pp:NaN4438-4438
Publication Date(Web):2016/06/01
DOI:10.1039/C6TB00699J
Polymer–protein core–corona particles can be used as multifunctional platforms in biological and medical applications. In this research, we prepared poly(2-hydroxyethyl methacrylate)–bovine serum albumin (PHEMA–BSA) core–corona particles by the “grafting from” method. In order to prepare the particles, activators generated by electron transfer for atom transfer radical polymerizations (AGET ATRP) of HEMA initiated by a BSA macroinitiator were performed. The polymerizations were conducted in the presence of ppm amounts of transition metal catalyst and ascorbic acid. Transmission electron microscopy, atomic force microscopy, dynamic light scattering and ξ-potential measurements were used to characterize the core–corona particles. The average size and ξ-potentials of the particles are strongly dependent on the amounts of BSA used in AGET ATRP. The secondary structure and bioactivity of the protein molecules in the coronae of the particles were studied. In vitro cytotoxicity assays and cell uptake assays indicate that the biohybrid particles are nontoxic and can be internalized into the cells. The polymer–protein core–corona particles will find applications in drug delivery and biomedical imaging.
Co-reporter:Xiwen Zhang, Li Liu, Jia Tian, Jian Zhang and Hanying Zhao
Chemical Communications 2008(Issue 48) pp:NaN6551-6551
Publication Date(Web):2008/11/11
DOI:10.1039/B815778B
The use of stoichiometrically functionalized gold nanoparticles (AuNPs) as building units in polymerization reaction is described; the obtained copolymers, comprised of AuNPs and polystyrene, behave differently in various solvents, micellar structures with PS cores and AuNPs corona are obtained in water.
Co-reporter:Xiwen Zhang, Yongfang Yang, Jia Tian and Hanying Zhao
Chemical Communications 2009(Issue 25) pp:NaN3809-3809
Publication Date(Web):2009/05/26
DOI:10.1039/B906967D
Polystyrene (PS) with pendant gold nanoparticles and PS-coated Fe3O4nanoparticles self-assemble into vesicle structures with PS and PS-coated Fe3O4nanoparticles in the wall and gold nanoparticles in the shell.
Co-reporter:Jing Zhang, Yue Zhang, Feiyang Chen, Weiyao Zhang and Hanying Zhao
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 18) pp:NaN12221-12221
Publication Date(Web):2015/04/10
DOI:10.1039/C5CP01560J
Salt-induced self-assemblies of poly(ethylene glycol-block-spiropyran methacrylate) (PEG-b-PSPMA) block copolymers were studied in this research. PEG-b-PSPMA block copolymers were dissolved in a 10:1 N,N-dimethyl-formamide (DMF)/water mixture. Upon ultraviolet light (UV) irradiation, the pendant spiropyran (SP) groups in the PSPMA blocks were isomerized into open merocyanine (MC) forms and the addition of inorganic salts (CuCl2, FeCl3 and Zn(CH3COO)2) induced micellization of PEG-b-PSPMA block copolymers in the solutions. In a salt-induced micelle, complexes formed by PSPMA and inorganic ions are in the cores and PEG chains are in the coronae. The reverse conversion of the isomers from MC form to SP form in the dark was studied by UV-vis, and the self-assembled aggregates were analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The self-assembly of PEG-b-PSPMA in aqueous medium was also investigated. In aqueous solution, amphiphilic PEG-b-PSPMA self-assembled into micelles with the hydrophobic PSPMA blocks in the cores and the hydrophilic PEG blocks in the coronae. Upon UV irradiation, the hydrophobic SP units in the cores were isomerized into hydrophilic MC forms. The MC isomers have the attractive MC–MC interactions, and the reversion from MC to SP in the dark is difficult. DLS and TEM results both demonstrated that the micelles self-assembled by PEG-b-PSPMA did not disassemble upon UV irradiation, due to the attractive MC–MC interactions in the cores.
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