Silica nanoparticles encapsulated by polystyrene via surface grafting and in situ emulsion polymerization

Monodisperse polystyrene/SiO2 composite particles (PSCPs) with core-shell structure were then obtained by in situ emulsion polymerization of styrene (St) on the surface of grafted silica nanoparticles. Nanosized silica was synthesized by Stober method and modified with the oleic acid for the first time. The C=C bonds of oleic acid were covalently attached to silanol groups at the surface of nanosized silica to induce coating. The thickness of the coating layer can be altered by the variation of the amount of styrene, and the diameters of PSCP can be controlled by the variation of the amount of grafted silica. The average diameters of these spheres increase from 180 to 250 nm, while grafted silica nanoparticles increase from 1.0 to 1.5 g. It has been proven that this method is useful to obtain narrowly distributed particles with well-defined particle morphology. (C) 2004 Elsevier B.V. All rights reserved.