Surface-modified hemispherical polystyrene/polybutyl methacrylate composite particles

Micrometer-sized polystyrene/poly(n-butyl methacrylate) composite particles of hemisphere morphology and narrow size distribution were prepared by a process of single-step swelling of uniform polystyrene template microspheres with emulsion droplets of the monomer n-butyl methacrylate containing the initiator benzoyl peroxide in the presence, or absence, of the co-swelling agent toluene. Butyl methacrylate was then polymerized at 73 degrees C within the template microspheres. Surface and bulk characterization of the particles were performed by methods such as FTIR, elemental analysis, XPS, advancing contact angle, light microscope, SEM, and cross-sectional TEM. Selective surface functionalization of the poly(n-butyl methacrylate) phase of the composite particles was performed by carrying out a similar swelling and polymerization process in the presence of a water-soluble vinylic monomer such as acrylamide.     

Film formation from nano‐sized polystyrene latex particles

This work reports on the steady state fluorescence (SSF) technique for studying film formation from surfactant‐free, nano‐sized polystyrene (PS) latex particles prepared via emulsion polymerization. The latex films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures in 5, 10, 15, 20 and 30 min time intervals above the glass transition temperature (T_g) of PS. During the annealing processes, the transparency of the film was improved considerably. Monomer and excimer fluorescence intensities, I_P and I_E respectively, from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of the latex films was monitored by using photon transmission intensity, I_tr. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 10.3 and 50.3 kJ mol⁻¹. Void closure temperatures, T_v, were determined from the minima of I_tr value. Copyright © 2005 John Wiley & Sons, Ltd.     

Silica‐Coated Metal Nanoparticles

The advanced high‐quality synthesis of dense and porous silica‐coated nanostructures is enjoying ever‐increasing research interests for their important properties and diverse applications, especially for catalytic, controlled release, colorimetric diagnostics, photothermal therapy, surface enhanced Raman scattering (SERS) detection, and so forth. In this timely Focus Review, we summarize the up‐to‐date synthesis strategies, improved properties, and emerging applications of silica‐coated metal nanoparticles. In particular, the large scale synthesis of silica‐coated metal nanoparticles and the recent development of hollowed‐out silica‐coated metal nanoparticles by silica dissolution are emphasized for new and practical applications.     

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.     

Mesoporous‐Silica‐Functionalized Nanoparticles for Drug Delivery

The ever‐growing interest for finding efficient and reliable methods for treatment of diseases has set a precedent for the design and synthesis of new functional hybrid materials, namely porous nanoparticles, for controlled drug delivery. Mesoporous silica nanoparticles (MSNPs) represent one of the most promising nanocarriers for drug delivery as they possess interesting chemical and physical properties, thermal and mechanical stabilities, and are biocompatibile. In particular, their easily functionalizable surface allows a large number of property modifications further improving their efficiency in this field. This Concept article deals with the advances on the novel methods of functionalizing MSNPs, inside or outside the pores, as well as within the walls, to produce efficient and smart drug carriers for therapy.     

Silica‐supported metallocenes: effect of the preparation procedure on the morphology of polyethylene particles

Polyethylene (PE) particles are produced by a catalyst prepared by contacting a (C₄H₉Cp)₂ZrCl₂/MAO pre‐mixing solution with SiO₂ support. These particles have a large granular size and very few fine particles compared with those derived from a catalyst prepared by adsorption of (C₄H₉Cp)₂ZrCl₂ onto methylaluminoxane modified SiO₂. The amount of Al in the pre‐mixing catalyst has an important effect on its activity and the PE particle size distribution. The optimal concentration is about 30 wt.‐%. The PE particles produced using a pre‐mixing catalyst consist of globules with randomly oriented fiber structure on the surface, whereas those produced using adsorption catalysts have worm‐like fibrils protruding from the PE globule surface.     

Nanosized‐Silica‐Reinforced Holographic Polymer‐Dispersed Liquid Crystals

Summary: Nanosized silicas added to holographic polymer‐dispersed liquid crystals (HPDLC) provide the resin phase with increased elasticity, dimensional stability, and the high diffraction efficiency of the gratings. On the other hand, nucleation and growth of periodic modulation are delayed, especially with small‐sized silica because of the increased viscosity of the resin mixture. Effects of the LC/resin composition and cell gap on the diffraction efficiency have also been studied.

AFM image of silica added HPDLC.     

Narrowly dispersed micrometer‐sized composite spheres based on diazonium–polystyrene

Diazonium group–substituted polystyrene (PS–N) micrometer‐sized spheres with narrow distribution were prepared from highly crosslinked polystyrene particles. Then a composite sphere was prepared with the micro‐PS–N sphere as core and submicrometer‐sized poly(styrene‐methyl methacrylate‐acrylic acid) [P(S‐MMA‐AA)] colloids or nanometer‐sized SiO₂ particles as shell via columbic interaction. The ionic linkages between the core and shell convert to covalent bonds in the thermal treatment process. As a result, the composite sphere becomes very stable toward polar solvents as well as toward ultrasonic treatment. A hollow SiO₂ micrometer‐sized sphere then was achieved by removing the core under sintering conditions (700 °C). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4284–4288, 2004     

Preparations of polystyrene/aluminum hydroxide and polystyrene/alumina composite particles in an ionic liquid

Polystyrene (PS)/aluminum hydroxide (Al(OH)(3)) composite particles were successfully prepared by the sol-gel process of aluminum isopropoxide (Al(OPr(i))(3)) in a hydrophilic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]) using ammonium hydroxide (NH(4)OH) as a catalyst in the presence of PS seed. Transmission electron microscopy observation of ultrathin cross-sections of the composite particles revealed that the composite particles had a core-shell morphology consisting of a PS core and a Al(OH)(3) shell having high crystallinity. The amount of secondary nucleated Al(OH)(3) could be reduced by dropwise addition of NH(4)OH. Moreover, PS/η-Al(2)O(3) composite particles were successfully prepared by heat treatment of PS/Al(OH)(3) at 300 °C in N(2) atmosphere, which is below the decomposition temperature of PS.     

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.     

Synthesis and properties of silica/polystyrene/polyaniline conductive composite particles

In this study, silica/polystyrene/polyaniline (SiO₂/PS/PANI) conductive composite particles were synthesized by four sequential reactions. The nanosized SiO₂ particles were synthesized from tetraethoxysilane (TEOS) by a sol–gel process with water as the solvent medium, followed by a surface modification with triethoxyvinylsilane; then the surface modified SiO₂ particles were used as seeds to synthesize SiO₂/PS composite particles with soapless seeded emulsion polymerization. Finally, the SiO₂/PS particles were used as seeds to synthesize the SiO₂/PS/PANI conductive composite particles. The sol–gel process of SiO₂, the effect of surface modification, and several other factors that influenced polymerization of styrene in the soapless seeded emulsion polymerization will be discussed. Either potassium persulfate (KPS) or 2,2′‐azobis(isobutyramidine) dihydrochloride (AIBA) was used as the initiator to synthesize the uniform SiO₂/PS particles successfully, and the cross‐section morphology of the SiO₂/PS particles was found to be of a core–shell structure, with SiO₂ as the core, and PS as the shell. The SiO₂/PS particles were well dispersed in many organic solvents. In the following step to synthesize SiO₂/PS/PANI conductive composite particles, sodium dodecyl sulfate (SDS) played an important role, specifically, to absorb aniline onto the surfaces of the SiO₂/PS particles to carry out the polymerization of aniline over the entire surface of the particles. The conductivity of the SiO₂/PS/PANI composite particles approached that of semiconductive materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 342–354, 2005     

Well‐Defined Single‐Site Monohydride Silica‐Supported Zirconium from Azazirconacyclopropane

The silica‐supported azazirconacyclopropane ?SiOZr(HNMe₂)(η²‐NMeCH₂)(NMe₂) ( 1 ) leads exclusively under hydrogenolysis conditions (H₂, 150 °C) to the single‐site monopodal monohydride silica‐supported zirconium species ?SiOZr(HNMe₂)(NMe₂)₂H ( 2 ). Reactivity studies by contacting compound 2 with ethylene, hydrogen/ethylene, propene, or hydrogen/propene, at a temperature of 200 °C revealed alkene hydrogenation.     

Preparation of epoxy‐functionalized polystyrene/silica core–shell composite nanoparticles

Epoxy‐functionalized polystyrene/silica core–shell composite nanoparticles were prepared by the postaddition of glycidyl methacrylate (GMA) via emulsion polymerization. The outermost shell of obtained multilayered core–shell particles was made up of poly(glycidyl methacrylate) (PGMA). A semicontinuous process involving the dropwise addition of GMA was used to avoid demulsification of the emulsion system. The amount of grafted PGMA was quantified by Fourier transform infrared spectroscopy and was altered in a wide range (1–50 wt % to styrene). The binding efficiency was usually high (ca. 90%), indicating strong adhesion between the silica core and the polymer shell. There were approximately four or five original silica beads, which formed a cluster, per composite of nanoparticles whose size was about 60–70 nm. Other main factors of polymerization conditions including the amounts of sodium dodecyl sulfonate and silica are also discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2253–2262, 2004     

Electrorheological properties of carbon nanotube/polyelectrolyte self‐assembled polystyrene particles by layer‐by‐layer assembly

Sulfonated polystyrene (PS) particles were prepared by the sulfonation of PS microspheres with H₂SO₄. Then, composite particles were synthesized by layer‐by‐layer (LbL) self‐assembly with funtionalized multiwall carbon nanotubes (fMCNTs) and polyelectrolytes on sulfonated PS particles. The amount of fMCNTs on PS particles was adjusted by controlling the number of fMCNT layers by LbL self‐assembly. Composite particles were characterized by ζ‐potential analysis, scanning electron microscopy, and thermal analysis. The electrorheological (ER) properties of composite particles in insulating oil was investigated with varying the number of fMCNT layers under controlled electric fields. It was observed that the number of fMCNT layers was a critical factor to determine the ER properties of composite particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1058–1065, 2008