Lewis酸改性烷基锂负离子聚合研究进展Ⅱ.以二烷基镁为添加剂的第1代引发体系

Progress in research of Lewis acids modified alkyl lithium initiated anionic polymerization Ⅱ.First generation initiator systems with dialkylmagnesium additives

分别评述了于50℃和100℃下n,s-Bu2Mg对在环己烷中由s-BuLi引发苯乙烯聚合动力学的影响,发现[n,s-Bu2Mg]/[PSLi]在0～20时随其增大聚合增长活性种的反应性连续下降,下降程度由R2Mg的类型和用量及[n,s-Bu2Mg]/[PSLi]的值决定。紫外可见光分析表明,该结果与R2Mg与RLi生成的混合络合物有关,可认为生成的酸根型络合物处于动态平衡。总结了所研究范围内的聚合活性特征,特别是聚合物相对分子质量的控制问题。此外还讨论了不同结构的R2Mg对苯乙烯的聚合阻滞效应及聚合活性种的稳定性。

The influence of n,s-dibutylmagnesium on the kinetics of styrene polymerization initiated by s-butyl lithium in cyclohexane at 50 ℃ and 100 ℃ were respectively reviewed.The reactivity of the propagating species was found to decrease with increasing dialkylmagnesium/polystyryllithium（mole ratio） in the range from 0 to 20.The presence of the magnesium derivatives led to a drastic reduction of the overall reactivity depending on the type,concentration,and proportion of dialkylmagnesiam used.This was associated with mixed complexes of n,s-dibutylmagnesium and s-butyllithium as shown in UV-visible spectra,which were considered as ＂ate＂ complexes in dynamic equilibrium.The living character of the polymerization,especially the control of the relative molecular mass was summarized over the entire range studied.In addition,the influence of the structure of various dialkylmagnesium additives on retardation of styrene polymerization and stability of the polystyryllithium species was investigated.