Preparation of silica-polystyrene core-shell particles up to micron sizes.

A method for producing silica-core composite particles with a polystyrene shell is proposed. Silica particles were prepared by the Stöber method through condensation and hydrolysis of tetraethyl orthosilicate in a water-ethanol-ammonia solution. The silica particles were the surface-modified with a coupling reagent, methacryloxypropyltrimethoxysilane (MPTMS), to introduce vinyl groups onto the particle surfaces. Polymerization of styrene was conducted with an initiator, potassium persulfate (KPS), and an anionic monomer, sodium p-styrenesulfonate (NaSS), in the presence of the silica particles. In these coating experiments, the average size of the silica particles was varied from 339 to 1210 nm with the concentration ranges of MPTMS (0-10 mmol/l), NaSS (0-10 mmol/l), KPS (4-12 mmol/l), and styrene (0.12-0.4 mol/l). Selection of reaction conditions enabled the preparation of composite particles that contained one core of silica. The coefficient of variance of size distribution of the composite particles was less than 7%, and shell thickness was in the range 125 to 410 nm.