Controllable synthesis of raspberry-like PS–SiO2 nanocomposite particles via Pickering emulsion polymerization

This paper presents a simple and controllable method for the synthesis of monodisperse nanometer-sized organic–inorganic raspberry-like polystyrene (PS)–SiO2 nanocomposite particles (NCPs) via Pickering emulsion polymerization, by simply using a silane coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MPS), as an auxiliary monomer and controlling its hydrolysis/condensation processes and amount. In this method, when MPS was stirred in acidic water with styrene (St) for a period of time, and then a basic silica solution added, raspberry-like PS–SiO2 NCPs were directly obtained after the polymerization. The whole process needs neither surface treatment for the silica particles nor additional surfactants or stabilizers. We propose that a silica-stabilized Pickering emulsion is formed through Si–OH reaction between the hydrolysis/condensation products of MPS distributed on the St droplets surface and the silica particles.