Synthesis of microcapsules with polystyrene/ZnO hybrid shell by Pickering emulsion polymerization

Polystyrene/zinc oxide (ZnO) hybrid microcapsules having polystyrene as inner shell and ZnO nanoparticles as outer shell were synthesized by Pickering emulsion polymerization method. ZnO nanoparticles were used to form the colloidosomes that worked as the polymerization vessels, where both styrene monomer and crosslink agent were polymerized together. Fourier transform infrared spectra and thermogravimetric thermograms showed the existence of ZnO and polystyrene in the shell of hybrid microcapsules. The hollow structure and the different morphology under various conditions were also observed by field emission scanning electron microscopy. In addition, the shell thickness of hybrid microcapsules increased as the monomer concentration increased. The photoluminescence property of PS/ZnO hybrid microcapsules could be maintained without any noticeable variation by comparing with the pure ZnO particles. It could be reasonably deduced that hybrid hollow microspheres with multifarious polymer as inner shell and ZnO nanoparticles as outer shell would be produced for many applications.     

Morphologies of micron-sized monodispersed composite polymer particles having crosslinked structures produced by seeded polymerizations

Three kinds of micron-sized monodispersed polystyrene (PS)/ poly(styrene - divinylbenzene) composite particles were produced by two kinds of seeded copolymerizations of styrene (S) and divinylbenzene (DVB) (PS seed/ (S+DVB)=2/1, wt. ratio; S/DVB=1/1, molar ratio) in the presence of about 2 μm-sized monodispersed PS particles, and their morphologies were examined. One was produced by a seeded dispersion copolymerization where almost monomers and initiators exist in an ethanol/water (12.6/4.0, w/w) medium. The others two were produced by seeded copolymerizations with the dynamic swelling method where almost monomers exist in the monomer-swollen particles using 2, 2'-azobisisobutyronitrile in monomer-swollen PS seed particles or using 4, 4'-azobis (4-cyanopentanoic acid) in an ethanol/water (7/43, w/w) medium. In the former polymerization, the produced composite particles had a high dense crosslinked shell, whereas in the latter two polymerizations, they did the comparatively homogeneous crosslinked structures.     

Preparation of micron-sized nonspherical polystyrene/poly(styrene-<Emphasis Type="Italic">co</Emphasis>-ethyleneglycol dimethacrylate) particles by seeded soap-free emulsion polymerization

Micron-sized nonspherical polymer particles having different morphologies were synthesized by seeded soap-free emulsion polymerization of styrene(St) and ethyleneglycol dimethacrylate(EGDMA,used as a crosslinker) on spherical, linear polystyrene(PS) seed particles.The morphology of the resulting PS/poly(St-co-EGDMA) particles was dependent on the crosslinker concentration and polymerization temperature.     

The morphology of composite polymer particles produced by multistage soapless seeded emulsion polymerization

 Composite polymer particles which contain poly(methyl methacrylate) (PMMA) and polystyrene (PS) components (PMMA/PS composite particle) were synthesized by the method of multistage soapless seeded emulsion polymerization. In this study, the process of multistage soapless seeded emulsion polymerization included two-stage polymerization, three-stage polymerization or four-stage polymerization. The morphologies of the PMMA/PS composite particles were studied. The kinetic factor was the main force to control the morphology of the linear PMMA–PS composite particles which were synthesized by the method of two-stage reaction. Both the kinetic factor and the thermodynamic factor decide the morphology of the linear composite particles which were synthesized by the method of either three-stage or four-stage reaction. However, the thermodynamic factor cannot influence the morphology of the PMMA/PS composite particles with a cross-linked structure which were synthesized by the method of three-stage reaction. The cross-linked composite polymer particles had the morphology of a multilayer structure, which showed that the polymer layers accumulated in their order of production. Received: 9 January 2001 Accepted: 14 June 2001     

Preparation of micrometer-sized, monodisperse "janus" composite polymer particles having temperature-sensitive polymer brushes at half of the surface by seeded atom transfer radical polymerization

Micrometer-sized, monodisperse polystyrene (PS)/poly[methyl methacrylate-(chloromethyl)styrene] [P(MMA-CMS)] composite particles having hemispherical structure were prepared by solvent evaporation from toluene droplets containing dissolved PS and P(MMA-CMS) dispersed in aqueous solution, which had been prepared using the membrane method. The formation of hemispherical ("Janus") morphology by phase separation between the PS and the P(MMA-CMS) was confirmed by both optical and electron microscopy. Atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DM) was subsequently carried out in the presence of hemispherical PS/P(MMA-CMS) composite particles in an aqueous dispersed system. After polymerization, the morphology of the particles changed from spherical to "mushroom" shape as observed by scanning electron microscopy, indicating that DM polymerized inside or on the surface of half [P(MMA-CMS) phase] of the particles. 1H NMR spectra were consistent with chloromethyl functional groups in P(MMA-CMS) operating as ATRP initiators in the DM polymerization.     

A facile strategy for synthesis of multilayer and conductive organo-silica/polystyrene/polyaniline composite particles

By means of a facilely designed strategy, we successfully fabricated the multilayer and conductive organo-silica/polystyrene/polyaniline (organo-silica/PS/PANi) composite particles. First, organo-silica/PS core/shell composite particles were synthesized by seeded emulsion polymerization and the vinyl groups located on the surface of organo-silica nanoparticles were used to induce in situ polymerization of styrene. The influence of the route of the addition of styrene on the morphology of organo-silica/PS composite particles was investigated. Then, the coating of organo-silica/PS composite particles with PANi was achieved by virtue of the "Swelling-Diffusion-Interfacial-Polymerization Method" (SDIPM). The whole preparation process was monitored by transmission electron microscope, scanning electron microscope, Fourier transform infrared, Raman spectroscopy, dynamic light scattering, and thermogravimetry. As a result, the multilayer and conductive organo-silica/PS/PANi nanocomposites possessed of a uniform size and well-defined morphology, and furthermore, their structure could be well controlled by simply changing the weight ratio of aniline/PS.     

悬浮-乳液复合聚合聚苯乙烯-聚甲基丙烯酸甲酯复合粒子的颗粒特性和成粒机理

采用在苯乙烯 (St)悬浮聚合过程中滴加甲基丙烯酸甲酯 (MMA)乳液聚合组分的悬浮 乳液复合聚合方法 ,制备大粒径聚苯乙烯 聚甲基丙烯酸甲酯 (PS PMMA)复合粒子 .研究聚合物粒径分布和颗粒形态的变化发现 ,在St悬浮反应中期滴加MMA乳液聚合组分后 ,聚合体系逐渐由悬浮粒子与乳胶粒子并存向形成单峰分布复合粒子转变 ,最终形成核 壳结构完整的大粒径PS PMMA复合粒子 ;在St悬浮反应初期滴加MMA乳液聚合组分 ,St与MMA一起分散成更小液滴 ,反应后期凝并成非核 壳结构复合粒子 ;在St悬浮反应后期滴加MMA乳液聚合组分 ,PMMA乳胶粒子与PS悬浮粒子基本独立存在 .根据以上结果 ,提出了St MMA悬浮 乳液复合聚合的成粒机理 .     

Production of micron-sized monodispersed core/shell polymethyl methacrylate/polystyrene particles by seeded dispersion polymerization

 Micron-sized monodispersed polymethyl methacrylate (PMMA)/polystyrene (PS) (PMMA/PS=2/1, wt ratio) composite particles consisting of PMMA-core and PS-shell were successfully produced by seeded dispersion polymerization of styrene in a methanol/water medium in the presence of about 2 μm-sized monodispersed PMMA particles. From the view point of thermodynamic equilibrium, such a morphology is difficult to form by usual seeded polymerization in a polar medium such as water. It is concluded that seeded dispersion polymerization in which almost all monomers and initiators exist in the medium has an advantage to produce core/shell polymer particles in which polymer layers accumulate in their order of the production regardless of the hydrophobicity of polymers, because of high viscosity in polymerizing particles. Received: 9 December 1996 Accepted: 26 February 1997     

Fabrication of zinc oxide/poly(styrene) grafted nanocomposite latex and its dispersion

Zinc oxide nanoparticles, with an average size of about 40 nm, were encapsulated by polystyrene using in situ emulsion polymerization in the presence of 3-methacryloxypropyltrimethoxysilane (MPTMS) as a coupling agent and polyoxyethylene nonylphenyl ether (OP-10) as a surfactant. Polymerization mechanism of nanocomposite latex was discussed. Transmission electron microscopy (TEM) proved the presence of ZnO nanoparticle appeared to be monodisperse in nanosize in polymer composite particles. ZnO/PS nanocomposites were characterized by Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results of FT-IR and XPS revealed that the surface of ZnO particle was successfully grafted by PS through the link of the coupling agent between ZnO and polymer. TGA and DSC results indicated an enhancement of thermal stability of composite materials compared with the pure polymer. SEM (scanning electron microscope) images showed a perfect dispersion of the ZnO particles in latex film. In addition, UV-visible absorption measurements demonstrated that the ZnO/PS composite coatings display a perfect performance of absorbing UV light.     

Fabrication of core/shell hybrid organic–inorganic polymer microspheres via Pickering emulsion polymerization using laponite nanoparticles

Oil-in-water (o/w) emulsions of styrene, as monomer oil in water, were achieved successfully via Pickering emulsification with laponite nanoparticles as the sole inorganic stabilizers. The formed emulsions showed excellent stability not only against droplets coalescence (before polymerization) but also against microparticles coagulation (after polymerization). Generally, the number of composite polystyrene microparticles (PS) increased and their sizes decreased with the content of solid nanoparticles used in stabilizing the precursor o/w emulsions. This is consistent with the formation of rigid layer(s) of the inorganic nanoparticles around the PS microparticles thus a better stability was achieved. The composite microparticles were characterized using various techniques such as surface charge, stability, transmission electron microscope (TEM), scanning electron microscope (SEM) and Fourier transform infra-red (FT-IR). Coating films of the prepared latexes were applied to flat glass surfaces and showed reasonable adhesion compared to PS latex particles prepared with conventional surfactants. The effect of employed conditions on the features of the resulting emulsions in terms of stability and particle size has been discussed.     

Morphological analysis of bead–string shaped and core–shell attapulgite@polystyrene (ATP@PS) particles via emulsion polymerization

A convenient method for the preparation of bead–string shaped and core–shell attapulgite@polystyrene (ATP@PS) composite particles through emulsion polymerization from needle‐shaped attapulgite is reported. The pretreatment of attapulgite with cetyltrimethylammonium bromide (CTAB) in ultrasonic is essential for successful encapsulation and for creating strong interfacial interaction between attapulgite and polystyrene (PS). The different morphologies of the ATP@PS particles, bead–string shaped and core–shell shaped, obtained with different amounts of styrene charges, were characterized by transmission electron microscopy (TEM). Encapsulation mechanisms of the two morphologies were also developed. Copyright © 2007 John Wiley & Sons, Ltd.     

细乳液聚合法制备磁性复合微球及其表征

在制备超细Fe3O4 磁性粒子的基础上 ,以 3种低分子量聚合物Disperbyk 1 0 6、Disperbyk 1 0 8和Disperbyk 1 1 1为Fe3O4 微粒在单体相中的分散稳定剂 ,采用细乳液聚合法制备了平均粒径为 3 40nm的PS Fe3O4 磁性复合微球 .详细研究了分散剂种类对细乳液聚合制备磁性复合微球的影响 ,并采用XRD、TGA和TEM等手段对磁性复合微球的形态、结构及磁响应性等进行了表征 .实验结果证明分散剂的选择对磁性复合微球的成功制备起着至关重要的作用 ,兼具酸性和碱性功能基的分散剂Disperbyk 1 0 6具有更好的分散和稳定效果 .TEM结果表明 ,所制备的复合微球具有一些缺陷 ,而缺陷处往往是Fe3O4 磁性粒子聚集的地方     

Functional colloidal particles stabilized by layered silicate with hydrophilic face and hydrophobic polymer brushes

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     

Semiconductor nanoparticle/polystyrene latex composite materials

Cadmium sulfide and cadmium selenide/cadmium sulfide core/shell nanoparticles stabilized with poly(cysteine acrylamide) have been bound to polystyrene (PS) latexes by three methods. First, anionic 5 nm diameter CdS particles were electrostatically attached to 130 nm surfactant-free cationic PS latexes to form stable dispersions when the amount of CdS particles was less than 10% of the amount required to form a monolayer on the surface of the PS particles or when the amount of CdS particles exceeded the amount required to form a monolayer on the PS particles. Transmission electron microscopy (TEM) showed nanoparticles on the surface of the latex particles. Fluorescence spectra showed unchanged emission from the nanoparticles. Second, anionic, surfactant-free PS latexes were synthesized in the presence of CdS and CdSe/CdS nanoparticles. TEM showed monodisperse latex particles with trapped nanoparticles. Third, surfactant-stabilized latexes were synthesized by copolymerization of styrene with vinylbenzyl(trimethyl)ammonium chloride electrostatically bound to the CdSe/CdS nanoparticle surface. Brownian motion of the submicroscopic composite particles in water was detected by fluorescence microscopy.     

Fabrication of cage-like particles via unstable seeded dispersion polymerization: A new concept in the polymerization-induced self-assembly

The formation mechanism of hollow micron-sized polystyrene (PS) particles having numerous dents on the surface, so-called cage-like particles, obtained from seeded dispersion polymerization (SDP) of 2-ethylhexyl methacrylate (EHMA) with low molecular weight (MW) PS particles stabilized by poly(vinyl alcohol) (PVA) in the presence of hexadecane droplets was investigated. It was found that association of poly(2-ethylhexyl methacrylate) (PEHMA)/hexadecane phases which occurs due to the instability of the obtained composite particles followed by a diffusion of PS ellipsoidal particles into each other is the main process responsible for the production of such unique morphology. Time course monitoring of the SDP showed that diffusion of hexadecane and/or PS and/or PEHMA phase into PS/PEHMA/hexadecane composite particles through PS shell which happens based on Ostwald ripening is the main phenomenon which results in the formation of the dents on the surface of final particles. Moreover, the experimental results revealed that in this reaction system, the polymerization develops in a faster manner rather than the SDP employing seed particles having higher MWs. Furthermore, it was observed that particles with different surface morphologies can be produced by using different hydrocarbons. The elimination of small particles which are produced in addition to the cage-like ones via decreasing the concentration of the stabilizer was another interesting finding of this research. The acquired results showed that unstable SDP is expected to be a new concept in polymerization-induced self-assembly (PISA) which employs instability of a dispersion for self-assembly of polymeric particles, and therefore, production of polymeric unique objects.     

Environmentally responsive "hairy" nanoparticles: mixed homopolymer brushes on silica nanoparticles synthesized by living radical polymerization techniques

This article reports on the preparation of environmentally responsive "hairy" nanoparticles by growth of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes from silica particles using living radical polymerization techniques and subsequent hydrolysis of PtBA to produce amphiphilic mixed poly(acrylic acid) (PAA)/PS brushes. Silica particles were synthesized by the Stober process and were functionalized with an asymmetric difunctional initiator-terminated monolayer. Surface-initiated atom transfer radical polymerization of tBA was carried out in the presence of a free initiator. Kinetics study showed that the polymerization was well controlled. By cleaving PtBA off the particles, the molecular weights of the grafted and free polymers were found to be essentially identical. Mixed PtBA/PS brushes were obtained by the nitroxide-mediated radical polymerization of styrene from PtBA particles. The M(n) of the grafted PS was found to be the same as that of the free PS formed in the solution from the free initiator. Amphiphilic mixed PAA/PS brush-coated nanoparticles were synthesized from mixed PtBA/PS particles by hydrolysis of PtBA with iodotrimethylsilane. Tyndall scattering experiments and (1)H NMR study showed that the mixed PAA/PS particles can be dispersed and form a stable suspension in CHCl(3), a selective solvent for PS, and also in CH(3)OH, a selective solvent for PAA, demonstrating the capability of these hairy nanoparticles to undergo chain reorganization in response to environmental changes.     

Modification of Cross-Linked Rubber Particles by Free Radical Polymerization

The synthesis of polystyrene chains covalently bound to the surface of cross-linked rubber particles from recycled tires (ground tire rubber, GTR) was investigated via free radical polymerization in situ by using azobisisobutyronitrile (AIBN) and dibenzoyl peroxide (BPO) as initiators. Indeed, the graft polymerization provides a significant route to modify the physical and chemical properties of these particles allowing to improve their compatibility with other polymers. Polymerization reactions were carried out in bulk by changing the styrene/GTR ratio as well as the amount of free radical initiator. Appreciable amounts of polystyrene (PS) were grafted on GTR when BPO was used as confirmed by particle characterizations.     

苯乙烯在阴离子型聚氨酯纳米水分散液中聚合过程的研究

采用自乳化法制备出阴离子聚氨酯纳米水分散液,以其作为乳化剂使苯乙烯单体在其中进行聚合,制备出不同聚苯乙烯与聚氨酯质量比的阴离子型PS/PU纳米复合物水分散液;对苯乙烯单体的聚合过程进行了研究;采用光子相关谱仪和透射电镜对其微观结构、粒径及其分布进行了测试,结果表明,该方法能够制备出稳定的具有核壳结构的PS/PU纳米复合物水分散液,但当苯乙烯单体浓度增大到一定程度(PS/PU质量比为50∶100)时,粒子不稳定而发生聚集.     

A facile method to prepare CdS/polystyrene composite particles

Nano-CdS/polystyrene composite particles were prepared via surfactant-free emulsion polymerization. 2-(Dimethylamino)ethyl methacrylate (DMEMA) was used as auxiliary monomer which co-polymerized with styrene (St) and provided the location for coordinating with Cd²⁺. By the coordination of Cd²⁺ ions to DMEMA, mono-disperse polystyrene with the Cd²⁺ ions on the particles surface were prepared successfully. With the release of S²⁻ ions from the thioacetamide (TAA), cadmium sulfide (CdS) was formed. Nano-CdS/PS composite particles could be synthesized via this facile method. The order of materials addition and the amount of initiator both are playing important roles to the final morphologies of the composite particles. In the method proposed in this study, no surfactant was used, and the stable emulsion was successfully obtained. UV–vis absorption and fluorescence measurement indicated the quantum dot effect in the resulted nano-CdS/PS composite particles. The possible composite particle formation mechanism was presented.     

Morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

 Monodispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles having 9.4 μm in diameter were produced by seeded polymerization for the dispersion of highly n-butyl methacrylate (BMA)-swollen PS particles, and their morphologies were examined. The highly BMA-swollen PS particles (about 150 times the weight of the PS seed particles) were prepared by mixing monodispersed 1.8 μm-sized PS seed particles and 0.7 μm sized BMA droplets prepared with an ultrasonic homogenizer in ethanol/water (1/2, w/w) medium at room temperature. After NaNO₂ aqueous solution as inhibitor was added in the dispersion, the seeded polymerization was carried out at 70 °C. In an optical microscopic observation, one or two spherical high contrast regions which consisted mainly of PS were observed inside PS/PBMA composite particles. In the PS domain, there were many fine spherical PBMA domains. Such morphologies were based on the phase separation of PS and PBMA within the homogeneous swollen particles during the seeded polymerization. Received: 04 June 1997 Accepted: 27 August 1997