茂钛化合物／改性MAO催化剂制备聚丙烯-b-间规聚苯乙烯嵌段共聚物

以五甲基环戊二烯基三苄氧基钛化合物 Cp Ti(OBz) 3 ]为主催化剂 ,改性甲基铝氧烷作助催化剂 ,采用单体顺序投入法 ,合成了聚丙烯 b 间规聚苯乙烯嵌段共聚物 .外加三异丁基铝可以使活性中心的氧化态由Ti(Ⅳ )还原为Ti(Ⅲ ) ,从而提高苯乙烯共聚单体的转化率 .实验表明此催化体系对共聚物的合成具有较高活性 ,适宜的茂钛化合物浓度可阻止活性中心被丙烯预聚物包埋 .抽除残余丙烯气也可促进苯乙烯的共聚合 .对聚合产物进行溶剂连续萃取 ,可分离出嵌段共聚物 ,并用 13 CNMR和DSC进行结构表征

Synthesis of Polypropylene-b-syndiopolystyrene Block Copolymers with Titanocene Activated with Modified MAO

Polypropylene-b-syndiopolystyrene block copolymers were synthesized by sequential addition of two monomers with Cp* Ti (OBz)s 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 TIBA and 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. 8×10-3mol· 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 (ⅥI) catalytic system is favorable to propylene prepolymerization while the Ti ( Ⅲ ) catalytic system is required for styrene polymerization,TIBA had 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 PP-b-sPS block 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, DSC and elemental analysis.