Preparation and characterization of polymer/silica nanocomposites via double in situ miniemulsion polymerization

Polymer/SiO₂ nanocomposite microspheres were prepared by double in situ miniemulsion polymerization in the presence of methyl methacrylate, butyl acrylate, γ‐methacryloxy(propyl) trimethoxysilane, and tetraethoxysilane (TEOS). By taking full advantage of phase separation between the growing polymer particles and TEOS, inorganic/polymer microspheres were fabricated successfully in a one‐step process with the formation of SiO₂ particles and the polymerization of organic monomers taking place simultaneously. The morphology of nanocomposite microspheres and the microstructure, mechanical properties, thermal properties, and optical properties of the nanocomposite films were characterized and discussed. The results showed that hybrid microspheres had a raspberry‐like structure with silica nanoparticles on the shells of polymer. The silica particles of about 20 nm were highly dispersed within the nanocomposite films without aggregations. The transmittance of nanocomposite film was comparable to that of the copolymer film at around 70–80% from 400 to 800 nm. The mechanical properties and the fire‐retardant behavior of the polymer matrix were improved by the incorporation of silica nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3128–3134, 2010     

Effect of initiation site location on morphology of polymer microspheres via pickering polymerization

A novel way is introduced to control polymerization routes and morphology of final polymer microspheres during the Pickering polymerization. Cetyltrimethylammonium bromide (CTAB)‐modified silica and different initiators are used simultaneously to determine the initiation location, nucleation step, and morphology of final particles. As Pickering stabilizer, the CTAB‐modified silica is characterized by dynamic light scattering. The size and distribution of the oil droplets stabilized by the silica nanoparticles is observed by optical microscopy. The resulted silica/polymer composite microspheres are characterized by scanning electron microscopy and transmission electron microscopy. The silica content is measured by thermogravimetric analysis. It is proven that both surface property of inorganic particles and type of initiators can greatly affect the polymerization routes and the morphology of the obtained polymer microspheres. Detailed formation mechanisms of several kinds of polymer particles are also proposed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

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 carboxylic acid‐coated silica nanoparticles

The preparation of carboxylic acid‐coated silica nanoparticles was investigated. A monolayer of carboxylic acid residues with controllable graft density was anchored to the nanoparticle by a ring‐opening reaction with succinic anhydride. Poly(methacrylic acid) [poly(MAA)] grafted nanoparticles were prepared via a polymerization–deprotection strategy. Tert‐butyl methacrylate was polymerized from the surface of silica nanoparticles in a predictable manner and with excellent control over the molecular weight distribution. Subsequent removal of the tert‐butyl group resulted in poly (MAA) grafted nanoparticles. The polymer nanoparticles were also functionalized with dyes, which may be useful in tracking the particles in biological systems. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation of silica microspheres with a broad pore size distribution and their use as the support for a coated cellulose derivative chiral stationary phase

A templating strategy using crosslinked and functionalized polymeric beads to synthesize silica microspheres with a broad pore size distribution has been developed. The polymer/silica hybrid microspheres were prepared by utilizing the combination of a templating weak cation exchange resin, a structure‐directing agent N‐trimethoxysilylpropyl‐N,N,N‐trimethylammonium chloride, and a silica precursor tetraethyl orthosilicate. The silica microspheres were then obtained after calcinating the hybrid microspheres. The as‐prepared materials were characterized by scanning electron microscopy, mercury intrusion porosimeter, and thermal gravimetric analysis. The results showed that the starting templating beads were about 5 μm in diameter and the formed silica microspheres were less than 3 μm with a pore size range of 10–150 nm, some pores were even extended to beyond 250 nm. It was demonstrated that cellulose tris(3,5‐dimethylphenylcarbamate) was readily coated onto the surface of the as‐synthesized silica microspheres without any additional surface pretreatment. The coated silica microspheres were uniformly dispersed even with high loading of the chiral stationary phase, which exhibited high resolution chiral separations in high‐performance liquid chromatography.     

Synthesis and adsorption properties of gold nanoparticles within pores of surface‐functional porous polymer microspheres

Mesoporous polymer microspheres with gold (Au) nanoparticles inside their pores were prepared considering their surface functionality and porosity. The Au/polymer composite microspheres prepared were characterized by transmission electron microscope (TEM), X‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) techniques. The results showed that the adsorption of Au nanoparticles could be increased by imparting the pore structure and surface‐functional groups into the supporting polymer microspheres (in this study, poly (ethylene glycol dimethacrylate‐co‐acrylonitrile) and poly (EGDMA‐co‐AN) system). Above all, from this study, it was established that the porosity of the polymer microspheres is the most important factor that determines the distribution and adsorption amount of face‐centered cubic (fcc) Au nanoparticles in the final products. Our study showed that the continuous adsorption of Au nanoparticles with the aid of the large surface area and surface interaction sites formed more favorably the Au/polymer composite microspheres. The BET measurements of Au/poly(EGDMA‐co‐AN) composite microspheres reveals that the adsorption of Au nanoparticles into the pores kept the pore structure intact and made it more porous. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5627–5635, 2004     

Reparation of silica/poly(methacrylic acid)/poly(divinylbenzene-co-methacrylic acid) tri-layer microspheres and the corresponding hollow polymer microspheres with movable silica core

 Hollow poly(divinylbenzene-co-methacrylic acid) (P(DVB-co-MAA)) microspheres were prepared by the selective dissolution of the non-crosslinked poly(methacrylic acid) (PMAA) mid-layer in ethanol from the corresponding silica/PMAA/P(DVB-co-MAA) tri-layer hybrid microspheres, which were afforded by a three-stage reaction. Silica/PMAA core-shell hybrid microspheres were prepared by the second-stage distillation polymerization of methacrylic acid (MAA) via the capture of the oligomers and monomers with the aid of the vinyl groups on the surface of 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified silica core, which was prepared by the Stöber hydrolysis as the first stage reaction. The tri-layer hybrid microspheres were synthesized by the third-stage distillation precipitation copolymerization of functional MAA monomer and divinylbenzene (DVB) crosslinker in presence of silica/PMAA particles as seeds, in which the efficient hydrogen-bonding interaction between the carboxylic acid groups played as a driving force for the construction of monodisperse hybrid microspheres with tri-layer structure. The morphology and the structure of silica core, silica/PMAA core-shell particles, the tri-layer hybrid microspheres and the corresponding hollow polymer microspheres with movable silica cores were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS).     

Synthesis of poly(silyl ether)s containing pendant chloromethyl groups by the polyaddition of bis(oxetane)s with dichlorosilanes

The polyaddition of bis(3‐ethyl‐3‐oxetanylmethyl) terephthalate (BEOT) with dichlorodiphenylsilane (CPS) using tetrabutylammonium bromide (TBAB) as a catalyst proceeded under mild reaction conditions to afford a polymer containing silicon atoms in the polymer main chain. A poly(silyl ether) (P‐1) with a high molecular weight (M_n = 53,200) was obtained by the reaction of BEOT with CPS in the presence of 5 mol % of TBAB in toluene at 0 °C for 1 h and then at 50 °C for 24 h. The structure of the resulting polymer was confirmed by IR and ¹H NMR spectra. Furthermore, it was proved that the polyaddition of certain bis(oxetane)s with dichlorosilanes proceeds smoothly to give corresponding poly(silyl ether)s with TBAB as the catalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2254–2259, 2000     

Acrylic polymer/silica hybrids prepared by emulsifier‐free emulsion polymerization and the sol–gel process

Acrylic polymer/silica hybrids were prepared by emulsifier‐free emulsion polymerization and the sol–gel process. Acrylic polymer emulsions containing triethoxysilyl groups were synthesized by emulsifier‐free batch emulsion polymerization. The acrylic polymer/silica hybrid films prepared from the acrylic polymer emulsions and tetraethoxysilane (TEOS) were transparent and solvent‐resistant. Atomic force microscopy studies of the hybrid film surface suggested that the hybrid films did not contain large (e.g., micrometer‐size) silica particles, which could be formed because of the organic–inorganic phase separation. The Si? O? Si bond formed by the cocondensation of TEOS and the triethoxysilyl groups on the acrylic polymer increased the miscibility between the acrylic polymer component and the silica component in the hybrid films, in which the nanometer‐size silica domains (particles) were dispersed homogeneously in the acrylic polymer component. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 273–280, 2006     

Preparation and characterization of monodisperse CdS quantum dot‐polymer microspheres

A novel and effective method for the preparation of monodisperse CdS quantum dot‐polymer microspheres was proposed. The monodisperse hollow polymer microspheres were firstly swelled in chloroform. Then, the reaction precursor composed of CdO and sulfur, was impregnated into the hollow polymer microspheres. Subsequently, the CdS quantum dots were synthesized directly within the polymer microspheres by thermal decomposition. The morphology, structure, and fluorescence properties of CdS quantum dot‐polymer microspheres were studied by scanning electron microscope, transmission electron microscope, fluorescence microscope, and flow cytometry. The results indicate that the fluorescent CdS quantum dots are successfully synthesized in the monodisperse hollow polymer microspeheres, which provide very strong fluorescence intensity, and offer excellent photostability due to the compact structure of the polymer matrix. These CdS quantum dot‐polymer microspheres have potential applications in biotechnology and biomedicine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 751–755, 2010     

Chromatographic performance of molecularly imprinted polymers: Core‐shell microspheres by precipitation polymerization and grafted MIP films via iniferter‐modified silica beads

In this work, two different surface imprinting formats have been evaluated using thiabendazole (TBZ) as model template. The first format is a thin film of molecularly imprinted polymer (MIP) grafted from preformed silica particles using an immobilized iniferter‐type initiator (inif‐MIP). The second format is molecularly imprinted polymer microspheres with narrow particle size distribution and core‐shell morphology prepared by precipitation polymerization in a two‐step procedure. For the latter format, polymer microspheres (the core particles) were obtained by precipitation polymerization of divinylbenzene‐80 (DVB‐80) in acetonitrile. Thereafter, the core particles were used as seed particles in the synthesis of MIP shells by copolymerization of DVB‐80 and methacrylic acid in the presence of TBZ in a mixed solvent porogen (acetonitrile/toluene). The materials were characterized by elemental microanalysis, nitrogen sorption porosimetry and scanning (and transmission) electron microscopy. Thereafter, the imprinted materials were assessed as stationary phases in liquid chromatography. From this study it can be concluded that grafted MIP beads can be obtained in a simple and direct manner, consuming only a fraction of the reagents used typically to prepare imprinted particles from a monolithic imprinted polymer. Such materials can be used in the development of in‐line molecularly imprinted solid‐phase extraction methods. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1058–1066, 2010     

Synthesis of SiO2/poly(styrene‐co‐butyl acrylate) nanocomposite microspheres via miniemulsion polymerization

A series of SiO₂/poly(styrene‐co‐butyl acrylate) nanocomposite microspheres with various morphologies (e.g., multicore–shell, normal core–shell, and raspberry‐like) were synthesized via miniemulsion polymerization. The results showed that the morphology of the composite latex particles was strongly influenced by the presence or absence of the soft monomer (butyl acrylate), the particle sizes of the silica, and the emulsifier concentrations. The incorporation of the soft monomer helped in forming the multicore–shell structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3202–3209, 2006     

一步聚合法制备壳核型、可控阶层结构的羰基铁/聚苯乙烯复合微球

采用改进的悬浮聚合法合成了一系列粒径和结构可调的羰基铁粉/聚苯乙烯磁性高分子微球.利用傅立叶变换红外光谱仪、热重分析仪、X射线衍射仪、扫描电镜等分析了微球的结构、化学成分及形貌.结果表明,通过改变苯乙烯单体和聚乙烯醇(PVA)的加入量,可以制备三类不同形貌和结构的复合微球,即多孔复合微球,无孔复合微球和含"带状"突起的...     

Acrylic polymer/silica hybrid for electron‐beam resists

An acrylic polymer/silica hybrid resist film was investigated for fabricating a microstructure by electron‐beam (EB) lithography. EB lithography on the hybrid thin film afforded a positive pattern whose depth corresponded to the EB exposure dose; this indicated that the hybrid was an analog resist and could fabricate a three‐dimensional microstructure. The resist film had high heat resistance and compatibility with the underlying quartz plate, probably because of the silica component. The acrylic polymer/(RSiO_1.5)_n hybrid film showed higher EB sensitivity than a film of the crosslinked acrylic polymer and an acrylic polymer/(SiO₂)_n hybrid. Atomic force microscopy observation of the hybrid film surface showed the homogeneous dispersion of the acrylic polymer and the silica components in the hybrid film. The acrylic polymer component was EB‐sensitive, whereas dispersing the acrylic polymer and silica components homogeneously also played an important role in increasing the EB sensitivity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2107–2116, 2006     

Preparation of PLGA microspheres with different porous morphologies

Poly(D,L-lactide-co-glycolide)(PLGA) microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres were studied. The results showed that addition of porogen or surfactants to the inner aqueous phase, types of organic solvents and polymer concentration affected greatly the microsphere morphology. When dichloromethane was adopted as organic solvent, microspheres with porous structure were produced. When ethyl acetate served as organic solvent, two different morphologies were obtained. One was hollow microspheres with thin porous shell under a lower PLGA concentration, another was erythrocyte-like microspheres under a higher PLGA concentration. Three types of microspheres including porous, hollow core with thin porous shell(denoted by hollow in brief) and solid structures were finally selected for in vitro drug release tests. Bovine serum albumin(BSA) was chosen as model drug and encapsulated within the microspheres. The BSA encapsulation efficiency of porous, hollow and solid microspheres was respectively 90.4%, 79.8% and 0. And the ultimate accumulative release was respectively 74.5%, 58.9% and 0. The release rate of porous microspheres was much slower than that of hollow microspheres. The experiment results indicated that microspheres with different porous structures showed great potentials in controlling drug release behavior.     

Ionic liquid‐based organic–inorganic hybrid electrolytes: Impact of in situ obtained and dispersed silica

Organic–inorganic hybrid electrolytes based on PEO‐NaTFSI‐ionic liquid (HMIMTFSI)‐silica (in situ production via sol gel process) are being reported in this article. The variation in conductivity with ionic liquid (IL) addition has been explained on the basis of number of free TFSI anions evaluated using ATR‐IR data. The deconvolution of the IR spectra of these hybrid electrolytes has given evidence of ion‐pair formation which has been compared vis‐á‐vis the conductivity variation. The hybrid electrolyte with maximum conductivity comprises the highest number of free imide ions and has lowest glass transition temperature. FESEM has displayed a porous and layered surface morphology with dispersed silica nanoparticles. In addition, the optimized hybrid electrolyte has been compared with 5 wt% (limit of mechanical stability) ex situ silica added composite where the temperature cycling of conductivity has shown that the ex situ dispersed hybrid electrolytes do not retrace their conductivity path contrary to the in situ prepared hybrid electrolytes. This behavior has been explained to be due to the hindrance offered by the ex situ added silica in the recrystallization kinetics of PEO. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 207–218     

Anisotropic janus magnetic polymeric nanoparticles prepared via miniemulsion polymerization

Anisotropic Janus magnetic polymeric nanoparticles are prepared via the miniemulsion polymerization of styrene and acrylic acid monomers in the presence of oleic acid‐coated magnetic nanoparticles (MNPs). The controllable phase separation between the polymer matrix and the encapsulated MNPs is a key success factor to produce Janus morphology. The effects of MNPs, 2,2′‐azobis(2‐isobutyronitrile) and sodium dodecyl sulfate contents, on the morphology, chemical composition and colloidal stability of the prepared Janus hybrid particles are investigated. Besides the determination of polymerization conversion, zeta potential, size analysis, TGA, and TEM are applied for characterization of the anisotropic particles. The results show the stable spherical Janus particles containing MNPs (15 wt % magnetic content) located on one side of each polymer particle. The anisotropic submicron Janus magnetic polymeric particles (250 nm) can be easily separated by an external magnet. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4779–4785     

Flame‐retardant epoxy resins: An approach from organic–inorganic hybrid nanocomposites

Phosphorus‐containing epoxy‐based epoxy–silica hybrid materials with a nanostructure were obtained from bis(3‐glycidyloxy)phenylphosphine oxide, diaminodiphenylmethane, and tetraethoxysilane in the presence of the catalyst p‐toluenesulfonic acid via an in situ sol–gel process. The silica formed on a nanometer scale in the epoxy resin was characterized with Fourier transform infrared, NMR, and scanning electron microscopy. The glass‐transition temperatures of the hybrid epoxy resins increased with the silica content. The nanometer‐scale silica showed an enhancement effect of improving the flame‐retardant properties of the epoxy resins. The phosphorus–silica synergistic effect on the limited oxygen index (LOI) enhancement was also observed with a high LOI value of 44.5. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 986–996, 2001     

Particle monolayer formation at the air–water interface by silica particle with well‐defined grafted polymer

Particle monolayer formation at the air–water interface by polymer‐grafted colloidal silica was investigated. Methyl methacrylate (MMA) was polymerized from initiative bromide groups at colloidal silica surface by atom transfer radical polymerization. We obtained polymer‐grafted silica particle (SiO₂‐PMMA) with relative narrow polydispersity of PMMA. For the polymer‐grafted particle with high graft density, particle monolayer formation was confirmed by π‐A isotherm measurement and SEM observation. Interparticle distance was controllable by surface pressure. Furthermore, grafted polymer chains were suggested to be fairly extended at the air–water interface. However, for the polymer‐grafted particle with low graft density, monolayer structure on substrate showed aggregation and voids. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2789–2797, 2006     

Synthesis of poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymer and their applications for ordered porous film and compatibilizer

A series of new functional poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymers (EVAL‐g‐PS) with controlled molecular weight (M_n = 38,000–94,000 g mol^?1) and molecular weight distribution (M_w/M_n = 2.31–3.49) were synthesized via a grafting from methodology. The molecular structure and component of EVAL‐g‐PS graft copolymers were confirmed by the analysis of their ¹H NMR spectra and GPC curves. The porous films of such copolymers were fabricated via a static breath‐figure (BF) process. The influencing factors on the morphology of such porous films, such as solvent, temperature, polymer concentration, and molecular weight of polymer were investigated. Ordered porous film and better regularity was fabricated through a static BF process using EVAL‐g‐PS solution in CHCl₃. Scanning electron microscopy observation reveals that the EVAL‐g‐PS graft copolymer is an efficient compatibilizer for the blend system of low‐density polyethylene/polystyrene. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 516–524