共查询到19条相似文献,搜索用时 171 毫秒
1.
Grafting of poly(methyl methacrylate) from narrow disperse polymer particles by surface-initiated atom transfer radical polymerization (ATRP) was investigated. Polydivinylbenzene (PDVB) particles were prepared by dispersion polymerization with poly(N-vinyl pyrrolidone) (PVP) as the stabilizer. Chloromethylated PDVB was used as initiating core sites for subsequent ATRP of methyl methacrylate with CuBr/bpy as catalyst system. It was found that poly(methyl methacrylate) was grafted not only from the particle surfaces but also from within a thin shell layer, leading to particles size increases from 2.38-3.00μm with a core-shell structure particles. The grafted core-shell particles were characterized with FTIR, SEM, DSC. 相似文献
2.
Rong Long LI Cheng You KAN Yi DU Ze Ping LI 《中国化学快报》2006,17(11):1503-1506
Monodisperse functional polymer microspheres with different particle size and with clean surface were prepared by batch soap-free emulsion polymerization of styrene, methyl methacrylate and acrylic acid in the presence of salts, and the influences of type and amount of electrolytes on polymerization process and particle morphology were investigated. Results showed that there was a critical concentration for different electrolyte to make polymerization process and the resultant emulsion stable, and the particle size increased with the increase of electrolyte concentration. The effect of metal ions was Ca^2+〉〉K^+〉Na^+〉Li^+, and the effect of haloids was Br〉Cl〉F. Keywords: Electrolyte, soap-free emulsion polymerization, polystyrene, latex particle morphology. 相似文献
3.
Yagoub Mansoori Khadijeh Roojaei Mohammad RezaZamanloo Gholamhassan Imanzadeh 《高分子科学》2012,30(6):815-823
An account of the experiments on preparing polystyrene(PS) nanocomposites through grafting the polymer onto organophilic montmorillonite is reported.Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety.Because the reaction may liberate HC1,it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H~+ ions.Only the silanol groups on the edge of the clay react with vinyltrichlorosilane.The radical polymerization of the product with styrene as a vinyl monomer leads to chemical grafting of PS onto the montmorillonite surface.The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction.Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy.The prepared nanocomposite materials and the grafted nano-particles were studied by XRD.Exfoliated nanocomposites may be obtained for 0.5 wt%-l wt%clay content.The nanocomposites were studied by thermogravimertic analysis(TGA) dynamic thermal analysis(DTA) and dynamic mechanical analysis (DMTA). 相似文献
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Xiao-bin Ding Zong-hua Sun Guo-xiang Wan Ying-yan Jiang Chengdu Institute of Organic Chemistry Chinesc Academy of Sciences Chengdu China Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》1999,(2):129-134
Fe_3O_4/Polystyrene(PSt) magnetic particles with core/shell structure have been prepared in thepresence of Fe_3O_4 magnetic fluid in ethanol/water medium by dispersion polymeriation of styrene. A Fe_3O_4particle formation mechanism was proposed. According to this mechanism, the size of particle nuclei isdetermined by the extent of aggregation of Fe_3O_4 /oligomer. Magnetic particles with diameter ranging from 5to 200 μm were prepared under different reaction conditions. Some polymerization parameters such as theconcentration of monomer, stabilizer, initiator, and ethanol which affect particle size and size distribution arediscussed and their effect on particle formation are explained by the proposed mechanism. 相似文献
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Cationic latexes were prepared through emulsion copolymerization of styrene(St) and butyl acrylate(BA) with a cationic surfactant,cetyl trimethyl ammonium bromide(CTAB).Latex properties,including particle size,size distribution,ζpotential,surface tension and monomer conversion,were determined for latexes prepared with different CTAB amounts. Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation.Results showed that both particle size andζpotential were function of polymerization time and latex solids.Parallel emulsion polymerizations with cationic,anionic charged initiator and charge-free initiators were also carried out,the latex properties were determined at different polymerization time.All these results were attentively interpreted based on the mechanisms of emulsion polymerization,surfactant adsorption and latex particle stabilization. 相似文献
6.
PolyDL-lactide (PDLLA) and the block copolymer, polyDL-lactide-b-poly(ethylene glycol)-b-polyDL-lactide (PELA) were used as the microsphere matrix to encapsulate plasmid DNA. The PDLLA, PELA, pBR322-1oaded PDLLA and pBR322-1oaded PELA microspheres were prepared by solvent extraction method based on the formation of multiple w1/o/w2 emulsion. The microspheres were characterized by surface morphology, mean particle size, particle size distribution and loading efficiency. The integrity of DNA molecules after being extracted from microspheres was determined by agarose gel electrophoresis. The result suggested that plasmid DNA molecules could retain their integrity after being encapsulated by PELA. The PELA microspheres could prevent plasmid DNA from being digested by DNase. The in vitro degradation and release profiles of plasmid DNA-loaded microspheres were measured in pH - 7.4 buffer solution at 37℃. The in vitro degradation profiles of the microspheres were evaluated by the deterioration in microspheres surface morphology, the molecular weight reduction of polymer, the mass loss of microspheres, the changes of pH values of degradation medium, and the changes of particle size. The in vitro release profiles of the microspheres were assessed by measurement of the amount of DNA presented in the release medium at determined intervals. The release profiles were correlation with the degradation profiles. The release of plasmid DNA from PELA microspheres showed a similar biphasic trend, that is, an initial burst release was followed by a slow, but sustained release. 相似文献
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OU BaoLi LI DuXin College of Chemistry Chemical Engineering Hunan University of Science Technology Xiangtan China State Key Laboratory of Powder Metallurgy Central South University Changsha China 《中国科学B辑(英文版)》2008,51(1):51-57
Immobilization of the atom transfer radical polymerization (ATRP) macroinitiators at the silica nanoparticle surfaces was achieved through surface modification with excess toluene-2,4-diisocynate (TDI), after which the residual isocyanate groups were converted into ATRP macroinitiators. Structurally well-defined polystyrene chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined, densely grafted outer polystyrene by ATRP, which was initiated by the as-synthesized silica-based macroinitiator. FTIR, NMR and gel permeation chro-matography (GPC) were used to characterize the polystyrene/silica hybrid particles. 相似文献
8.
Ethylene-α-octene copolymer(POE)/polystyrene(PS) blend pellets with fine particle sizes were prepared by diffusion and subsequent polymerization of styrene in POE pellets through a one-pot procedure.The effects of the amounts of styrene and BPO on PS content,monomer efficiency and monomer conversion were investigated.The blend pellets were characterized by Micro-FTIR and FESEM,showing homogeneous diametrical distributions of PS and particle size.After melt-processing into rods,the average particle sizes are almost doubled,but still in submicron scale.Compared to neat POE rods,the blend rods with PS content higher than 15% exhibit improved tensile modulus and tensile strength without significantly losing ductility,being attributed to the small sizes,complex nature of particles and the existence of POE-g-PS copolymer that result in good interfacial adhesion.POE/PS pellets were compared with the previously reported PP/PS pellets,and the differences between the two systems are attributed to the different morphology of the two matrices: POE is completely amorphous at the diffusion and polymerization temperature,while i PP is semicrystalline.Without efficient impediment of the crystal lamellae in POE pellets,styrene diffuses easily in POE pellets. 相似文献
9.
Preparation of polystyrene/silica nanocomposites by radical copolymerization of styrene with silica macromonomer 总被引:1,自引:0,他引:1
A two-stage process has been developed to generate the silica-based macromonomer through surface-modification of silica with polymerizable vinyl groups. The silica surfaces were treated with excess 2,4-toluene diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). Thus, polystyrene/silica nanocomposites were prepared by conventional radical copolymerization of styrene with silica macromonomer. The main effecting factors, such as ratios of styrene to the macromonomer, together with polymerization time on the copolymerization were studied in detail. FTIR, DSC and TGA were utilized to characterize the nanocomposites. Experimental results revealed that the silica nanoparticles act as cross-linking points in the polystytene/silica nanocomposites, and the glass transition temperatures of the nanocomposites are higher than that of the corresponding pure polystyrene. The glass transition temperatures of nanocomposites increased with the increasing of silica contents, which were further ascertained by DSC. 相似文献
10.
《Journal of Energy Chemistry》2016,(6)
The Co-based catalysts were prepared with different cobalt acetate solutions. Effects of p H value were studied deeply on Fischer–Tropsch synthesis(FTS) through a semi-batch reactor. Among all impregnation solutions(water, butanol, amyl alcohol, acetic acid, nitric acid and ammonium nitrate), the catalyst prepared by NH_4NO_3 solution showed the highest catalytic activity due to its small particle size and high reduction degree. However, the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS. According to FT-IR spectra results, the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity. Whereas, the high activity of catalysts prepared from NH_4NO_3 solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower p H conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher p H value. 相似文献
11.
André Pfaff Leonie Barner Axel H.E. Müller Anthony M. Granville 《European Polymer Journal》2011,(4):805-815
We report the synthesis and characterization of sugar-containing microspheres consisting of poly(divinylbenzene) (PDVB) cores onto which chains of galactose- or mannose-bearing polymers have been grafted. PDVB particles prepared by distillation polymerization with a diameter of 2.4 μm containing residual surface vinyl groups were used as starting material. “Grafting from”, “grafting through” and “grafting to” techniques were performed and special interest was laid towards the resulting grafting densities. The surface modification via “grafting from” was conducted by reversible addition fragmentation chain transfer (RAFT) polymerization directly from the surface, whereas thiol-ene chemistry was used to affix glycopolymer chains onto the particle surface. The resulting sugar-covered microspheres were analyzed towards their protein recognition activity with a series of lectins. 相似文献
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Rigid and monodisperse spherical polymer particles with 2.36 ± 0.18 μm diameter containing residual surface vinyl groups were prepared by photoinitiated precipitation polymerization of divinylbenzene. Anti‐Markovnikov addition of HBr to the surface vinyl groups yielded a 2‐bromoethyl functionality that was used as macroinitiator for atom transfer radical polymerization (ATRP), providing the possibility for further functionalization by controlled “grafting from” processes. This was demonstrated by grafting of glycidyl methacrylate brushes from the particle surface, using an ATRP system based on CuBr and pentamethyl diethylenetriamine. Existence of a methacrylic overlayer was verified by FTIR and XPS measurements, and the grafted particles were easily dispersed in water, confirming conversion of the particle surface from hydrophobic to hydrophilic. Hydrobromination of residual vinyl groups yields a macroinitiator that can be used for grafting of glycidyl methacrylate by ATRP. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1259–1265, 2009 相似文献
14.
Ming-Qing Chen Akio Kishida Mitsuru Akashi 《Journal of polymer science. Part A, Polymer chemistry》1996,34(11):2213-2220
Thermosensitive microspheres with 0.4–1.2 μm diameter consisting of a polystyrene core and poly(N-isopropylacrylamide) (polyNIPAAm) branches on their surfaces were prepared by the free radical polymerization of a polyNIPAAm macromonomer and styrene in ethanol. Electron spectroscopy for chemical analysis (ESCA) of the microsphere surface suggested that polyNIPAAm chains were favorably located on the surface of the microspheres. The morphology of the microspheres was observed by transmission electron micrograph (TEM) and the particle size of was estimated by submicron particle analyzer. The molecular weight of the polyNIPAAm macromonomer, the ratio of the macromonomer and styrene, and the polymerization temperature affected the particle size. Thermosensitive properties of polyNIPAAm-coated polystyrene microspheres were evaluated by the turbidity of their dispersion solutions and the hydrodynamic size of the miocrospheres. The transmittance in dispersion solutions changed clearly, similar to oligoNIPAAm and polyNIPAAm macromonomers. In addition, the particle size of microspheres decreased with rising temperature. These results were explained by the thermosensitivity of polyNIPAAm branches on the microsphere surface. © 1996 John Wiley & Sons, Inc. 相似文献
15.
Narrow-disperse, surface-functionalized "living" polymer microspheres with uniformly cross-linked structures were prepared by two-stage precipitation copolymerization of styrene and divinylbenzene. The two-stage precipitation polymerization is composed of an initial conventional precipitation polymerization for the nucleation followed by a reverse atom transfer radical polymerization(reverse ATRP) for the controlled polymerization process. The polymerization parameters(including reaction time for the first stage, AIBN amount and monomer loading) have been studied to show significant influences on the morphologies. Moreover, narrower size distribution and an ATRP initiator-functional surface of resulting particles can be obtained by applying reverse ATRP to conventional precipitation polymerization in the second stage. Furthermore, the "livingness" of the resulting polymer microspheres was testified by their surface modification of poly[2-(dimethylamino) ethyl methacrylate](PDMAEMA) brushes via surface-initiated ATRP(SI-ATRP). 相似文献
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Further insight into the mechanism of poly(styrene‐co‐methyl methacrylate) microsphere formation
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Samantha I. Applin Russell C. Schmitz Pacita I. Tiemsin Jan Genzer John W. Connell Christopher J. Wohl 《Journal of polymer science. Part A, Polymer chemistry》2017,55(13):2249-2259
Polymeric microspheres have been used in a broad range of applications from chromatographic separation techniques to analysis of air flow over aerodynamic surfaces. The preparation of microspheres from many polymer families has consequently been extensively studied using a variety of synthetic approaches. Although there are a myriad of polymeric microsphere synthesis methods, free‐radical initiated emulsion polymerization is one of the most common techniques. In this work, poly(styrene‐co‐methyl methacrylate) microspheres were synthesized via surfactant‐free emulsion polymerization. The effects of co‐monomer composition and addition time on particle size distribution, particle formation, and particle morphology were investigated. Particles were characterized using dynamic light scattering and scanning electron microscopy to gain further insight into particle size and size distributions. Reaction kinetics were analyzed through consideration of characterization results. A particle formation mechanism for poly(styrene‐co‐methyl methacrylate) microspheres was proposed based on characterization results and known reaction kinetics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2249–2259 相似文献
19.
分散聚合法制备液相芯片聚苯乙烯磁性复合微球的研究 总被引:1,自引:0,他引:1
本文将丙烯酸基磁流体均匀分散到苯乙烯单体中,采用分散聚合法制备出了适于构建液相芯片微球载体的单分散性微米级磁性微球.考察了丙烯酸基磁流体预处理时间、加料顺序和单体量对微球形貌和粒径分布的影响及其条件优化.扫描电镜(SEM)显示磁性微球平均粒径为7.77 μm,具有良好的单分散性(多分散指数PDI为1.03),并且表面光滑致密;用超导量子干涉磁强计测量了Fe3O4纳米粒子的磁化曲线;用红外光谱(FT-IR)和热失重(TG)方法表征了磁性微球的化学结构及Fe3O4含量. 相似文献