Synthesis of polystyrene/silica and poly(styrene-co-butyl acrylate)/silica nanocomposite particles by Pickering emulsion polymerization with non-functionalized silica nanoparticles

Organic-inorganic nanocomposite particles can be prepared by Pickering emulsion polymerization. Attempts to prepare polystyrene/silica nanocomposite particles without the addition of auxiliary comonomers, surface modification of silica sols or alcoholic silica sols or use of functionalized silica nanoparticles have not yielded satisfactory results. In this study, we demonstrated a versatile approach to prepare polystyrene/silica and poly(styrene-co-butyl acrylate)/silica nanocomposite particles by subjecting commercially available non-functionalized silica nanoparticles through Pickering emulsion polymerization. Monodisperse nanocomposite particles with a high silica incorporation efficiency were fabricated. We investigated the effects of the silica content, initiator content and pH value on the properties of the prepared nanocomposite particles. Mechanistic investigations of the system showed that the silica nanoparticles did not require surface polymerization. Two aspects facilitated the adhesion of silica nanoparticles onto the growing latex particles: wetting of hydrophilic silica nanoparticles by more hydrophobic oligomers, and electrostatic interaction between the silica nanoparticles and oppositely charged oligoradicals.