Abstract: Polypropylene b syndiopolystyrene block copolymers were synthesized by sequential addition of two monomers with Cp^*Ti(OBz)₃ catalyst activated with modified methylaluminoxane(MAO) and triisobutylaluminium(TIBA). The result shows that the titanocene has a high activity on propylene/styrene block copolymerization. The concentration of Cp^*Ti(OBz)₃, the amount of TIBAand the residual propylene monomer after prepolymerization were investigated and found to have pronounced influence on the catalytic activity. The appropriate concentration of the titanocene complex 〔c(Ti)=0.6～0.8×10^-3 mol·L^-1〕 will prevent the active centers from being buried by propylene prepolymers so that the copolymerization of the two monomers was promoted. Since the Ti(Ⅵ) catalytic system is favorable to propylene prepolymerization while the Ti(Ⅲ) catalytic system is required for styrene polymerization, TIBAhad played an important role in changing the active centers from Ti(Ⅳ) to Ti(Ⅲ) so that the block copolymerization can take place. The investigation also indicated the existence of residual propylene after propylene prepolymerization will prevent styrene from block copolymerization. The PPb sPSblock copolymers were separated from the gross products with successive extraction with boiling 2-butanone, heptane, THF, and chloroform. Each fraction of materials were characterized by ¹³C NMR, DSCand elemental analysis.

Key words: Titanocene catalyst, Polypropylene, Syndiotactic polystyrene, Block copolymerization