二乙二醇单乙醚基钡/三异丁基铝/正丁基锂体系引发合成反式-1,4-聚异戊二烯

以正丁基锂(简称Li)为主引发剂、二乙二醇单乙醚基钡(简称Ba)和三异丁基铝(简称Al)为助引发剂、环己烷为溶剂,对异戊二烯(Ip)聚合反应动力学及产物的微观结构进行了研究。结果表明,在Ba/Al/Li引发的聚合体系中,Ip的聚合反应速率与单体浓度呈动力学一级反应关系,假一级表观增长反应速率常数和表观增长反应活化能均与引发体系的三组分摩尔比相关;Al是引发体系中重要的活性组分,且随Ba/Al/Li引发体系中Al用量的增加,聚合反应速率先升高后下降,当Ba/Al/Li(摩尔比)为1/4/4时,聚合反应速率达到最大;Ba在调节聚异戊二烯反式-1,4-结构摩尔含量中的作用大于Al;聚合温度对聚合产物微观结构含量基本无影响。

Synthesis of trans-1,4-polyisoprene by barium salt of di(ethylene glycol) ethyl ether/triisobutyl aluminum/n-butyl lithium initiator system

Polyisoprene (PI) was synthesized with n-butyl lithium (simplified as Li) as initiator, barium salt of di(ethylene glycol) ethyl ether (simplified as Ba) and triisobutyl aluminum (simplified as Al) as assistant initiators, cyclohexane as solvent. The polymerization kinetics and the microstructure of PI were investigated. The results showed that the polymerization rate was linear with monomer concentration in Ba/Al/Li initiator system. The pseudo first order apparent propagation reaction rate constant and apparent propagation activation energy were related with the Ba/Al/Li(mole ratio). Al was the key active species in the initiator system, and the reaction rate firstly increased and then decreased with the increase of Al in the Ba/Al/Li. When the Ba/Al/Li(mole ratio) was 1/4/4, the reaction rate got its maximum. The effect of Ba in regulating the trans-1,4-unit content of PI was larger than that of Al. The temperature had no obvious effect on the microstructure of PI.