聚丁二烯基锂/三异丁基铝引发苯乙烯阻滞负离子聚合

Retarded Anionic Polymerization of Styrene Initiated by Polybutadiene Lithium/i-Bu_3Al

以聚丁二烯基锂(PBLi)为引发剂、i-Bu3Al为调节剂、环己烷为溶剂,在70～120℃下引发苯乙烯聚合,研究了n(i-Bu3Al)∶n(PBLi)对阻滞苯乙烯聚合行为的影响;并用NMR方法对反应的聚合动力学进行了研究。实验结果表明,加入i-Bu3Al时体系的聚合反应速率降低,n(i-Bu3Al)∶n(PBLi)越大,聚合反应速率越慢,甚至反应完全停滞;当n(i-Bu3Al)∶n(PBLi)=1.0、反应温度由90℃升至120℃时,聚合反应速率大幅加快,1.5 h内苯乙烯转化率达到90%以上。当n(i-Bu3Al)∶n(PBLi)较小时,两者可能形成较高活性的1∶2络合体;当n(i-Bu3Al)∶n(PBLi)较大时可能形成低活性的1∶1络合体,且1∶2络合体自身及其与1∶1络合体之间均存在构型转换。

The retarded anionic polymerization of styrene initiated by polybutadiene lithium （PBLi） / i-Bu3Al at 70 - 120℃ in cyclohexane was investigated. The results showed that the polymerization reaction slowed down to complete stagnation with increasing n（i-Bu3Al） ： n（PBLi） from 0.3 to 1.0. The polymerization rate increased rapidly with rise of the reaction temperature at n （ i-Bu3Al ） ： n（PBLi） 1.0. It was indicated that 1 ： 2 i-Bu3Al/PBLi complex probably formed at low n（i- Bu3Al） ： n （ PBLi）, which could promote the styrene polymerization at 90℃. At high n （ i-Bu3Al） ： n（ PBLi）, 1 ： 1 complex formed and the polymerization rate was considerable just at high temperature （higher than 100 ℃）. The reactive activity of the former was higher than the latter and the transformation between them or among 1 ： 2 complex might exist.