双金属引发体系苯乙烯活性聚合活性种的交互缔合动力学

自从发现烷氧基钾(ＲＯＫ)/烷基锂(ＲＬｉ)双金属引发体系对丁二烯苯乙烯阴离子共聚具有高效竟聚率调节作用以来1],相关的机理研究一直十分活跃2～6].在这类双金属引发体系中,由于含有Ｋ、Ｌｉ两种反离子,因此可能存在钾活性种(ＰＫ)和锂活性种(ＰＬｉ)的交互缔合体.但迄今有关不同反离子活性种形成交互缔合体的研究报道较少.本工作利用2甲基2己醇钾对苯乙烯均聚反应速度具有较大影响这一特性,对低Ｋ/Ｌｉ情况下可溶性醇钾/ｎＢｕＬｉ双金属引发体系苯乙烯均聚动力学进行了研究.建立了以交互缔合体为基础的反应动力学模型.求得了ＰＫ的增…

CROSS-ASSOCIATION DYNAMICS OF LIVING SPECIES OF BIMETALLIC INITIATING SYSTEM IN LIVING POLYMERIZATION OF STYRENE

The dynamics of living polymerization of styrene was studied with alkyllithium/potassium alkoxide as bimetallic initiator and cyclohexane as solvent. It was found that the apparent propagation rate constants ( k ap )increased greatly with little increasing of K/Li ratios and in linear relationships with the concentrations of potassium alkoxide (\)when K/Li ratios were lower that 0 1. And the slopes of k ap \|\ lines increased with the decreasing of alkyllithium concentrations. This dynamics feature can not be explained quantitatively by the ordinary association dynamics model which ignored the cross\|association between the propagation species with different metallic ion. In this paper, a new dynamics model on cross\|association concept was established and the dynamics feature of living polymerization of styrene can be interpreted satisfactorily. The propagation rate constant of potassium species(\%k\%\-k) and the constant group, (\%K\%\-1/2)\+\{0.5\}/\%K\%\-3, of dissociation constants of cross\|association species (\%K\%\-3)and lithium species (\%K\%\-1)were derived by curve fitting and led to values of 7 1 ×10 3(mol/L)\+\{-1\}min\+\{-1\} and 67 (mol/L) \+\{-0.5\} respectively at a polymerization temperature of 50℃.