单茂钛／MAO催化剂合成间规聚苯乙烯聚合介质的影响

单茂钛催化剂五甲基茂基三对甲氧基苯氧基钛[Cp^*Ti(OC6H4OCH3)3]/甲基铝氧烷（MAO）／三异丁基铝（TIBA）体系催化苯乙烯聚合,在不同的聚合介质中,表现出不同的催化活性和立构选择性,聚合产物的结构和性质也不一样。

Influence ofPolymerization Mediums on Synthesis of Syndiotactic Polystyrene withMono-Titanocene/Methylaluminoxane Catalyst

Syndiotactic polystyrene (sPS) was synthesized in the presence of a mono-titanocene complex of η5-pentamethylcyclopentadienyltri-4-methoxyphenoxy titanium ［Cp*Ti(OC6H4OCH3)3］ activated by methylaluminoxane(MAO).Influences of different polymerization mediums including heptane, toluene, chlorobenze and neat styrene on the activity, syndiotacticity and molecular weight of polystyrene were investigated. The bulk polymerization was the best choice in all cases for producing sPS with the highest activity and molecular weight. In contrast, much better activity and syndiotacticity of yields arose from polymerization in heptane than in the other solvents. Using a solvent with higher dipole moment, such as chlorobenze, lower activity and syndiotacticity were given resulting from the stronger coordination of solvent with Ti(Ⅲ) active species which controlled syndiospecific polymerization of styrene. Aggregated structures of sPS obtained respectively from bulk polymerization and polymerization in heptane used as solvent were different.