Fabrication and characterization of raspberry-like PSt/SiO2 composite microspheres via miniemulsion polymerization

Raspberry-like composite microspheres with polystyrene (PSt) as cores and nanosilica particles as shell were prepared through miniemulsion polymerization by using the anionic sodium dodecyl sulfate (SDS) as surfactants and 2-(methacryloyl) ethyltrimethylammonium chloride (MTC) as auxiliary monomer. TEM indicated that the colloidally stable composite microspheres have the typical raspberry-like morphology. Zeta potential measurements confirmed that the positively charged MTC was located on the surface of the composite microspheres and had a drastic impact on the formation of the composite microspheres. The average particle sizes and the final silica contents of the composite microspheres could range from 150 to 250 nm and 10 to 40 wt%, respectively, depending upon the reaction conditions. The influences of some synthetic parameters, for instance, the initial silica amount, MTC amount and SDS concentration on the polymerization stability, diameters, silica contents and morphology of the composite microspheres were studied in detail.