Copolymerization of acrylonitrile (AN) with p-trimethylsilylstyrene (TMSS) was carried out at 60°C in bulk and in solution in the presence of 2,2Јazobisisobutyronitrile (AIBN). The reactivity ratios of AN (M 1 ) and TMSS (M 2 ) were determined to be r 1 ϭ 0.068 and r 2 ϭ 0.309. The effects of the AIBN concentration and that of the chain transfer agent CCl 4 on the molecular weights (MWs) of the copolymers were investigated. An increase in the concentrations of AIBN or CCl 4 in solution led to a decrease in MW. Poly(AN-co-TMSS-co-St) was synthesized in solution using AIBN as the initiator. The molar fraction of AN was 0.415, while the molar ratio of TMSS/St varied from 1 : 1 to 1 : 9. The transition temperatures and thermal and thermooxidative stabilities of poly(AN-co-TMSS) and poly(AN-co-TMSS-co-St) were investigated. The differential scanning calorimeter technique was used to determine the compatibility of the poly(AN-co-TMSS) and poly(AN-co-TMSS-co-St) with commercial poly(AN-co-St). All the blends show a single glass transition temperature, which indicates the compatibility of the blend components. The surface film morphology of the blends mentioned above was examined by X-ray photoelectron spectroscopy. The data obtained indicate that the silicon-containing copolymer is concentrated in the surface layer.