含氮类亲核试剂对异丁烯阳离子聚合的作用(Ⅰ)——三乙胺对以四氯化钛为共引发剂阳离子聚合的作用

Effect of N-Containing Nucleophiles on IB Carbocationic Polymerization(I) ——Effect of Triethylamine on IB Carbocationic Polymerization

亲核试剂在可控阳离子聚合体系中起着重要作用 ,含氮类亲核试剂三乙胺 ,可以有效地控制阳离子聚合反应生成聚合物的分子质量 ,使聚合物的分子质量分布变窄 ,实现可控阳离子聚合。三乙胺在乙酸叔丁酯 /四氯化钛和水 /四氯化钛两个引发体系引发异丁烯的阳离子聚合体系的研究结果表明 ,三乙胺在异丁烯阳离子聚合体系中主要起 3个作用 :(1 )与质子络合 ,生成无活性的络合离子 ,起到质子捕获剂的作用 ;(2 )与增长的碳正离子络合 ,降低碳正离子的反应活性 ,使碳正离子的稳定性增加 ,聚合反应的速率下降 ,有利于向可控聚合转化 ;(3 )当三乙胺浓度大到一定程度时 ,由于严重的溶剂化作用 ,包围了碳正离子 。

Nucleophiles play an important role in controllable cationic polymerization systems. N - containing nucleophiles triethylamine can control isobutylene carbocationic polymerization and obtain polymer with narrow molecular distribution in containing (Et)3N systems. After systematic and profound investigation to triethylamine the roles of triethylamine are revealed. The roles of triethylamine in IB carbocationic polymerization fall into the following three: (1) Playing the role of 'proton trap' by combining with protons to produce complex cations without activity. (2) Combining with increasing carbon cations as to make the cation activity decreased. The results increases carbon cation steady and decreases reaction speed, thus it will be beneficial to transform the reaction to controllable one. (3) Stopping the reaction when concentration of used triethylamine reaches certain degree because the carbon cations are circled due to the critical solventization.