Preparation of graphene oxide coated polystyrene microspheres by Pickering emulsion polymerization.

Exfoliated graphene oxide (GO) nanosheets with hydrophilic oxygen-containing functional groups and hydrophobic residual conjugated structure are prepared by the oxidation of graphite powders. Polymerization of styrene stabilized by GO nanosheets is conducted at varied pH values. The morphology of the products is observed by field-emission scanning electron microscope (FE-SEM). It is found that GO coated polystyrene (PS) microspheres with narrow size distribution are obtained, although highly hydrophilic GO nanosheets cannot stabilize the monomer droplets in aqueous phase. Flocculation of polymer microspheres and GO nanosheets embedded in the PS matrix is induced by further decreasing the hydrophilicity of stabilizer. FT-IR, UV-vis spectra, XRD patterns and TGA results indicate the strong interaction between resulted PS chains and GO nanosheets during the initial stage of the polymerization. The amphiphilicity of GO nanosheets and the interaction between polymer and stabilizer are considered to be responsible for the fabrication of GO coated PS colloidal particles.