芳氧基稀土化合物催化ε-己内酯开环聚合的链转移反应及Monte Carlo模拟

Monte Carlo Simulation and Chain Transfer Reaction in Ring-opening Polymerization of ε-Caprolactone Initiated by Rare Earth Aryloxides

设计了三(2,6-二叔丁基-4-甲基苯氧基)稀土配合物[Ln(OAr)3]催化ε-己内酯(CL)开环聚合反应体系中的链转移反应.证明存在分子内/分子间酯交换反应,并验证聚合物在链转移反应过程中发生明显的分子量下降和分子量分布变宽.用Monte Carlo方法对聚ε-己内酯(PCL)链转移过程进行了计算机模拟,定量解释了链转移过程中环链分子数量比值的增加、环和链分子的数均分子量下降以及分子量分布变宽等现象,并发现随着链转移反应的进行,体系的各项参数先后趋于定值,最终体系将进入"环链平衡"状态.

Transesterification remains an essential cause of the difficulties to carry out living ring-opening polymerization of ε-caprolactone initiated by rare earth tris（2,6-di-tert-butyl-4-methylphenolate） s.This paper investigates chain transfer reaction which significantly decreases molecular weights and broadens the distributions（Mw /Mn） of the polymers.The intra-and inter-molecular transesterification reactions are demonstrated as well.A Monte Carlo program simulates the chain transfer kinetics and quantitatively reproduces the increase in the cyclic molecule number,the decrease in molecule weights and the broadening of Mw /Mn.A ring-chain equilibrium is reached when the number of cyclic molecules keeps constant after enough reaction time.