Preparation of colloid microspheres of SiO2/Polystyrene without a coupling agent via soap-free emulsion polymerization

The colloid microspheres of SiO₂/Polystyrene without a coupling agent were prepared by soap-free emulsion polymerization. The component and microstructure of the composite particles were characterized by FT-IR and SEM technology, and the mechanism of polymerization was also investigated by the particles size and distribution using dynamic light scattering (DLS) method. The characterized results showed that polystyrene is cross-linked on the surface of SiO₂ by the chemical band of Si-O groups. The structures of synthesized SiO₂/Polystyrene microspheres with the diameter of 180-320 nm are formed from petal-like structure to raspberry-like structure. The mechanism of polymerization revealed that the nucleation of polystyrene deposits and forms droplets on the surface of SiO₂ at the beginning of polymerization. The droplets then agglomerate and shedding form the surface of SiO₂, resulting in the swell of new nucleation in suspension and a slower increase of SiO₂/Polystyrene microspheres diameter during the polymerization.