A method was presented for the preparation of raspberry-like organic-inorganic nanocomposite microspheres with polystyrene (PSt) as cores and nano-silica particles as shells through miniemulsion polymerization in the presence of aqueous nanosilica dispersions.A small amount of nonionic CA-897 (poly(oxyethylene) octyl phenylether

with 40 oxyethylene units) was used as surfactant and 1-vinylimidazole (1-VID) as auxiliary monomer.Composite microspheres were obtained via the acid-base interaction between silica particles and auxiliary monomer 1-VID.TEM indicated that the colloidally stable composite microspheres had typical raspberry-like morphology

indicating the acid-base interaction was strong enough for the formation of long-stable composite spheres.The average particle sizes and the final silica contents adsorbed on the composite microspheres could range from 140 nm to 180 nm and 19 wt% to 31 wt%

respectively

depending upon reaction conditions.The influences of some synthetic parameters

for instance

CA-897 concentration

ultrasonic frequency

ultrasonic time on the polymerization stability

diameters

silica contents and morphology of the composite microspheres were studied in detail.With the CA-897 amount increase

the average diameter of the composite microspheres tended to decrease and the silica contents adsorbed on the latexes surface increased.Ultrasonic frequency had obviously influence on the average diameter and the silica content of composite microspheres

but the effect of ultrasonic time was less.