Monodispersed carboxyl-containing PSt seed latex with the diameter of 360 nm was first synthesized via batch emulsifier-free emulsion polymerization

and the positively charged PSt latex particles with surface reactive ethoxylsilyl groups were then prepared in the medium of ethanol and water using -aminopropyl triethoxysilane (KH-550) as modifier

then PSt/SiO2core-shell composite microspheres were obtained by dropwise adding tetraethoxysilane (TEOS) into the above system.Influences of pH and TEOS amount on the morphology of PSt/SiO2 core-shell composite microspheres were investigated using TEM and SEM.Results showed that the PSt/SiO2core-shell composite microspheres were generated only under alkaline conditions.When the amounts of PSt seed particles and TEOS was 1.5 g and 5.0 g

respectively

and pH was controlled at 8.5

the encapsulation of PSt seed particles with SiO2 was intact

and the uniform SiO2 shell with about 35 nm was obtained

and after that

the percentage of the composite microspheres partially encapsulated by SiO2 increased with the increase of pH value.With the increase of TEOS amount from 2.5 g to 15 g

the thickness of PSt/SiO2core-shell composite microspheres gradually increased from 17 nm to 68 nm

but their surface gradually became rough.