Preparation of sulphonate-containing core/shell latex particles via seeded emulsion copolymerization

<正>In this study,P(St-MAA) seed latex particles were first prepared via soap-free emulsion polymerization of styrene(St) and methacrylic acid(MAA),then the seed particles were allowed to swell with St at room temperature,and the P(St-MAA)/P(StNaSS) core/shell latex particles were then synthesized via seeded emulsion copolymerization of St and sodium styrene sulphonate (NaSS) using AIBN as initiator in the presence of N,N'-methylenebisacrylamide(BAA,water-soluble crosslinker).Results showed that the polymerization could be carried out smoothly when the ratio of BAA to total monomers was less than 3 mol%,the narrow dispersed P(St-MAA) seed particles with the diameter of 150 nm and the P(St-MAA)/P(St-NaSS) core/shell latexes with the particle size of about 200 nm were synthesized.When the 25/75 mole ratio of NaSS/(St + MAA) and 2 mol%of BAA were used in the seeded emulsion polymerization,the resulted P(St-MAA)/P(St-NaSS) latex product showed a low weight loss after water extraction,and the NaSS unit content in the whole particle and in the shell reached 11.7 mol%and 34.6 mol%,respectively.     

Cagelike polymer microspheres with hollow core/porous shell structures

Submicron‐scaled cagelike polymer microspheres with hollow core/porous shell were synthesized by self‐assembling of sulfonated polystyrene (PS) latex particles at monomer droplets interface. The swelling of the PS latex particles by the oil phase provided a driving force to develop the hollow core. The latex particles also served as porogen that would disengage automatically during polymerization. Influential factors that control the morphology of the microspheres, including the reserving time of emulsions, polymerization rate, and the Hildebrand solubility parameter and polarity of the oil phase, were studied. A variety of monomers were polymerized into microspheres with hollow core/porous shell structure and microspheres with different diameters and pore sizes were obtained. The polymer microspheres were characterized by scanning electron microscopy, transmission electron microscopy, optical microscopy, and Fourier transform infrared spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 933–941, 2007     

The preparation and characterization of amphiphilic core/shell particles

Colloidal amphiphilic particles were prepared with hydrophilic polyacrylamide cores encapsulated by hydrophobic poly(butyl methacrylate) shells. The hydrophobic shell possessed a porous structure, which made the hydrophilic core accessible to the outside liquid. The amphiphilicity of the particles was characterized by their water and diesel oil absorbabilities. The effect of the polymerization conditions on the structure and thickness of the hydrophobic layer was investigated in some detail. Such amphiphilic particles can be dispersed in both water and hydrophobic liquids, and the dispersions have a long life in water and a more moderate one in oil.     

Behavior of pH-sensitive core shell particles at the air-water interface

In this article, the adsorption of latex core-responsive polymer-shell nanoparticles at the air-water interface is investigated using a Langmuir trough. Phase transition isotherms are used to explore their responsive behavior at the interface as a function of changes in the pH of the subphase. By adjusting the pH of the water prior to particle deposition, we probe the effect of the stabilizing polymer wetting by the water subphase on the stability of these particles at the air-water interface. In addition, by initially compressing a stable film of adsorbed particles and then subsequently changing the pH of the subphase we study desorption of these particles into the water phase.     

Analysis of stepwise heterocoagulation for the preparation of soft core/hard shell composite polymer particles

The stepwise heterocoagulation of small cationic hard particles (SPs) onto a large anionic soft particle (LP) for the preparation of soft core/hard shell composite polymer particles was examined using dynamic light scattering and spectrophotometry. The effects of the pH value, the emulsifier content which was pre-added to the LP emulsion, and the heat treatment time on the covering of a LP by SPs, and the stability of the heterocoagulated emulsion were clarified. Received: 12 May 1998 Accepted: 31 July 1998     

Facile synthesis of urchin-like glass/nickel core/shell composite hollow spheres

Novel urchin-like core/shell composite hollow spheres were fabricated by assembly of nickel nanocones on the surface of hollow glass spheres; the effects of some reaction parameters on the morphology of the shell layers and the room temperature magnetic properties of the products were investigated.     

Using electroless deposition for the preparation of micron sized polymer/metal core/shell particles and hollow metal spheres

Uniform and stable core-shell microspheres composed of a poly(methyl methacrylate) (PMMA) core and a thin metallic shell of nickel-phosphorus, cobalt-phosphorus, or mixed metal alloys (CoNiP, NiFeP, CoFeP) were prepared by dispersion polymerization of methyl methacrylate followed by electroless plating. The presence of the metallic shell around the particles was confirmed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoelectron spectroscopy. Transmission electron microscopy images of the cross-section of individual particles show that the thickness of the metal/alloy can be precisely tuned by adjusting the immersion time of the microspheres in the electroless bath. Depending on the deposited metallic material, various magnetic properties, from paramagnetic to ferromagnetic, are achieved. Finally, uniform hollow metallic spheres composed of nickel, cobalt, or nickel-cobalt alloy are obtained by dissolving the polymer core.     

A novel approach to prepare core/shell polymer latex particles with high sulphonate contents

Crosslinked x-P(St-MAA) seed latex was first prepared via soap-free emulsion copolymerization of styrene (St) and methyl methacrylic acid (MAA) with divinyl benzene as crosslinker and ammonium persulfate as initiator, and x-P(St-MAA)/x-P(St-NaSS) core/shell latex particles were then synthesized through a novel seeded emulsion copolymerization of St and sodium styrene sulphonate (NaSS) in the presence of water-soluble crosslinker N,N′-methylene bisacrylamide (BAA) using oil-soluble 2,2-azobis isobutyronitrile as initiator. TEM observation indicated that narrow dispersed core/shell latex particles were obtained, and element analysis showed that NaSS unit content in the whole particle and in the shell reached 22.8 wt% and 51.2 wt%, respectively.     

Production of micron-sized monodispersed core/shell composite polymer particles by seeded dispersion polymerization

 The effect of the weight ratio of seed polymer/monomer on the morphology of the poly(methyl methacrylate) (PMMA)/polystyrene (PS) monodispersed composite particles produced by batch seeded dispersion polymerization of styrene with 1.64-μm-sized monodispersed PMMA seed particles in a methanol/water medium (4/1 w/w) was examined. In the PMMA/PS weight ratios of 3/1 and 2/1, the composite particles had a clear morphology consisting of a PMMA core and a PS shell. In the ratio of 1/1, a lot of small PS domains were observed in the PMMA core though the PS shell was still formed. By stepwise addition of styrene monomer, the formation of the small PS domain was depressed and complete core/shell morphology was formed. Absorption/release treatments of toluene into/from the PMMA/PS (1/1 w/w) composite particles resulted in a drastic morphological change from the core/shell structure to a multi- layered one. Received: 2 February 1999 Accepted in revised form: 7 April     

Synthesis and characterization of a novel fluorine-containing polymer emulsion with core/shell structure

A novel fluorine-containing polymer emulsion 4 with core/shell structure was synthesized in water phase by a two-stage emulsion polymerization technique using monomer 3 (i.e., 2-methacryloyloxyethyl perfluorooctanoate (MAEF)) reacting with the monomers such as butyl acrylate (BA), acrylic acid (AA) and styrene (ST). The monomer 3 was synthesized from the intermediate 2 (pentadecafluoro-octanoyl chloride) reacting with β-hydroxyethyl methacrylate (HEMA). Polymer film were prepared by coating emulsion 4 directly on a cleaned glass plate and allowed to dry at room temperature. Moreover, the characteristics of polymer film such as hydrophobicity, chemical resistance, surface composition, thermal stability, emulsion particle morphology, as well as the film-forming property were also studied.     

Novel preparation of magnetite/polystyrene composite particles via inverse emulsion polymerization

In this paper, super-paramagnetic magnetite/polystyrene (PSt) composite particles were prepared by inverse emulsion polymerization with water-based magnetic ferro-fluid as dispersing phase and organic solvent and styrene (St) as continuous phase. And the mechanism of the nucleation was discussed. The influence of factors, such as the monomer content, the amount of the ferro-fluid and the different continuous phases on the morphology of the magnetite/polystyrene composite particles was studied. The final products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Magnetic hysteresis loop measurements revealed that the composite particles were super-paramagnetic.     

Fabrication of bimodal porous silicate with silicalite-1 core/mesoporous shell structures and synthesis of nonspherical carbon and silica nanocases with hollow core/mesoporous shell structures

In this work, an attempt has been made to modify the shape and nanostructure of core-shell materials, which have been usually generated on the basis of amorphous spherical cores. Novel core-shell silicate particles, each of which consists of a silicalite-1 zeolite crystal core and mesoporous shell (ZCMS), were synthesized for the first time. The ZCMS core-shell particles are unique because they are of pseudohexagonal prismatic shape and have hierarchical porosity of both a uniform microporous core and a mesoporous shell coexisting in a particle framework. The nonspherical bimodal porous core-shell particles were then utilized as templates to fabricate a new carbon replica structure. Interestingly, the pore replication process was carried out only through the mesopores in the shell, and not through the micropores due to the narrower micropore size in the core, resulting in nonspherical carbon nanocases with a hollow core and mesoporous shell (HCMS) structure. Nonspherical silica nanocases with HCMS structure were also generated by replication using the carbon nanocases as templates, which are not possible to synthesize through other synthetic methods. Interestingly, the pseudohexagonal prismatic shape of the zeolite crystals was transferred onto the carbon and silica nanocases.     

Effect of the Shell Crosslinking Level andCore/Shell Ratio on the Morphology of LatexParticles in the Preparation of Hollow Latexes简

Three-layer core/shell latex particles with various shell crosslinking level and shell thickness were prepared by multistep emulsion polymerization, and the hollow latex particles with different morphologies were then obtained after alkali post-treatment. Influences of divinyl benzene(DVB) content and the core/shell mass ratio on emulsion polymerization and particle morphology were investigated. Results showed that with the increase of DVB content, the percentage of total amount of ―COOH on the particle surface and free in aqueous phase(PSFa) decreased, and the morphology of the post-treated particles underwent evolution from cracked, intact hollow to deficient swelling structure. Decreasing the core/shell mass ratio could not only make more carboxyl groups encapsulated by the shell, but also increase the shell resistance to the swelling of the core. The uniform hollow latex particles with intact morphology were obtained when the DVB content was 3.54 wt% and the core/shell mass ratio was 1/6.     

Preparation of composite particles with magnetic silica core and fluorescent polymer shell

Dual functions of magnetic and fluorescent properties were created in composite particles that incorporated magnetite (Fe₃O₄) nanoparticles in particle cores of silica and fluorescent pyrene in particle shells of polystyrene. The Fe₃O₄ nanoparticles were prepared with a conventional homogeneous precipitation method and surface modified with a coupling agent of carboxyethylsilanetriol. The silica particles incorporating Fe₃O₄ nanoparticles were synthesized with a modified Stöber method in which the Fe₃O₄ nanoparticles were added to a system of tetraethylorthosilicate (TEOS)/ammonia/water/ethanol. Then, the magnetite/silica composite particles were coated with the pyrene/polystyrene shell in a soap-free emulsion polymerization, which was conducted in the presence of pyrene in a mixed solvent of water/ethanol. The composite particles prepared in the mixed solvent had both magnetic and fluorescent properties. The fluorescent spectrum of the particles with Fe₃O₄ was very similar to that without Fe₃O₄, indicating that the magnetic component within the core particles scarcely interfered with the fluorescent emission from the polymer shell.     

Production of soft core/hard shell composite polymer particles by the stepwise heterocoagulation method with heat treatment

Soft core/hard shell composite polymer particle was prepared by the stepwise heterocoagulation, which was proposed by authors in 1990, of many cationic hard small polymer particles (SPs) onto an anionic soft large polymer particle (LP). The powder was obtained by freeze-drying at 0 ^°C which was higher than glass transition temperature of LP (−7 ^°C) and lower than that of SP (90 ^°C). Received: 9 December 1997 Accepted: 12 May 1998     

Synthesis and properties of organo-fly ash/polyaniline with core/shell structure based on emulsion polymerization

Organo-fly ash(OFA) was prepared with pretreated fly ash(FA) and hexadecyltrimethyl ammonium bromide (HDTMAB),and the composites composed of OFA and polyaniline were obtained by emulsion polymerization at different OFA weight ratios(2.0 wt%,5.0 wt%,10.0 wt%,15.0 wt%and 20.0 wt%) in the presence of dodecylbenzenesulfonic acid as dopant and emulsifier.A polymerization procedure was supposed.The electrical conductivities of the composites were tested by the four-probe technique.The chemical structure and crystallinity of the composites were confirmed by FT-IR and X-ray diffraction,respectively.Morphologies of FA,OFA and the composites were observed by SEM.The element analysis was performed by energy dispersive spectrometry.The thermal stability of the composites was analyzed by TGA.The results showed that the electrical conductivity of the composites decreased with increasing the feed weight ratio of OFA,and the lowest value was 0.62 S/cm.HDTMAB and PAn were just adsorbed on the surface of FA and OFA,respectively according to the physical adsorption without destroying the crystalline structure of FA or OFA.The surface became smoother after organification of FA by using HDTMAB,and its content on FA surfaces was about 26.9 wt%.The core/shell structure of the composite was observed by SEM analysis.The composites showed a higher thermal stability than pure PAn by introduction of OFA into this polymerization system,the heat stability of PAn was increased by decreasing 31.8 wt%of weight loss after introducing 20 wt%of OFA.     

W/0乳化法制备明胶/β-磷酸三钙多孔复合微球及其物化性能表征

采用乳液、离子缔合法制备得到明胶（Gel）/β-纳米磷酸三钙(β-TCP)复合多孔微球,其尺寸可通过控制反应的搅拌速度进行调节。 SEM和光学显微镜观察表明,明胶/β-TCP复合微球尺寸在20～40 μm之间,被包敷的磷酸三钙为200 nm左右,微球内部呈多孔结构。 当m（磷酸三钙）∶m（明胶）＞0.4∶1时,有大量花瓣状晶体附着于复合微球的表面,是磷酸三钙溶解和明胶分子诱导重结晶所致。 XRD与IR图谱表明,磷酸三钙纳米粒子与明胶之间存在化学键合,明胶/β-纳米磷酸三钙复合微球的微观结构与自然骨相似。 DSC-TGA结果显示,90%的TCP在乳化过程中与明胶复合。 本文所制备的复合微球,为添加各种药物和促骨生长因子并实现缓释提供了优良的载体。     

Synthesis of a Au/silica/polymer trilayer composite and the corresponding hollow polymer microsphere with a movable Au core

Gold/silica/poly(N,N'-methylenebisacrylamide) (Au/SiO2/polyMBAAm) trilayer composite materials were prepared by distillation precipitation polymerization of N,N'-methylenebisacrylamide (MBAAm) in the presence of Au/SiO2 particles as seeds, in which the seeds were prepared by a combination of gold-complexing and silane coupling agent with a further modified St?ber method. The polymerization of MBAAm was performed in neat acetonitrile with 2,2'-azobisisobutyronitrile as an initiator to encapsulate the Au/SiO2 seeds driven by the hydrogen-bonding interaction between the hydroxyl group on the surface of the seeds and the amide unit of polyMBAAm without modification of the Au/SiO2 surface in the absence of any stabilizer or surfactant. Hollow polyMBAAm microspheres with movable Au cores were further developed by the selective removal of the middle silica layer with hydrofluoric acid. The resultant trilayer Au/SiO2/polyMBAAm composite and hollow polyMBAAm microspheres with movable Au cores were characterized by transmission electron microscopy. The diffusion of chemicals across the polyMBAAm shell was investigated by a catalytic reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride as a reductant.     

Pickering乳滴模板法制备超粒子结构有机/无机杂化微球

Pickering乳滴模板法制备有机/无机杂化的核壳微球越来越引起人们的关注,主要因为该方法制备出的微球具有以无机粒子为壳层的超粒子结构(supracolloidal structure),能够赋予微球独特的功能.胶体粒子在乳滴表面自组装形成有序的球面胶体壳,得到稳定Pickering乳液,固定乳滴表面的胶体粒子来制备核壳结构的微球或者以胶体粒子为壳层的微胶囊(colloidosome).本文综述了我们课题组以Pickering乳滴模板法制备超粒子结构有机/无机杂化微胶囊包括实心微球方面的工作.我们选择具有不同性能、种类的胶体粒子以及具有不同性质和功能的核材料,采用Pickering乳滴模板法,对吸附在乳滴表面的胶体粒子用不同的固定方法制备具有不同结构和性能的微球和微胶囊,利用基于多重Pickering乳液的聚合技术制备双纳米复合的超粒子结构多核聚合物微球.     

A novel route for the synthesis of composite dielectric core/silver shell particles

We demonstrated the possibility of preparing continuous silver shells on particles of polystyrene latex by enlarging adsorbed seeding metal nanoparticles in solution containing ascorbic acid and silver nitrate. It is shown that a strong batochromic shift of the maximum of surface plasmon resonance is observed for such composite structures. Original Russian Text ? O.V. Dement’eva, M.A. Filippenko, M.E. Kartseva, V.M. Rudoy, 2009, published in Kolloidnyi Zhurnal, 2009, Vol. 71, No. 4, pp. 569–571.