联吡啶双酚铝催化开环(共)聚合制备聚酯材料

Synthesis of Polyesters from Ring-opening(Co)polymerization by Aluminum Bipyridine Bisphenolate Complexes

有机金属配合物是研究和应用最为广泛的开环(共)聚合催化剂.其中,Salen-铝配合物(Salen)AlX已成功用于催化环酯开环聚合、环酐(或CO_(2))/环氧烷烃开环共聚合、对映异构体立体选择性聚合以及混合单体的序列选择性聚合,极大地推动了聚酯材料的发展.然而,由于“稀释效应”以及催化剂分解,(Salen)AlX在高单体/催化剂投料比(催化剂相对浓度较低)时催化活性会严重衰减甚至完全失活.提高催化剂的稳定性及杂质耐受性,并抑制催化剂的“稀释效应”,在保持聚合活性和可控性的同时降低催化剂用量、减少催化剂在聚酯中的残留是环境友好高分子领域的重要研究目标之一.我们利用稳定的吡啶环替代Salen配体中易分解的席夫碱结构,获得了高效稳定的联吡啶双酚铝氯化物(BpyBph)AlCl.本专论总结了(BpyBph)AlCl在催化丙交酯开环聚合、环(硫)酐/环氧烷烃开环共聚合以及多组分混合单体的序列选择性聚合制备具有精确链结构的聚酯材料方面的研究进展,重点阐述了(BpyBph)AlCl在催化活性、热稳定性、杂质耐受性以及聚合可控性方面的独特优势.

Organometallics are one kind of potential catalytic system for synthesis of polyester from ring-opening(co)polymerization,because their catalytic performance can be easily modulated by tuning the Lewis acidity of the metal centre and modifying the electronic or steric effects of ligand backbone.In the past decades,the aluminum complexes with salen-type ligand have been widely used in ring-opening polymerization of cyclic ester,ring-opening copolymerization of(thio)anhydride and epoxide,stereo-selective ring-opening polymerization and chemo-selective multicomponent polymerization for farbricating well-defined polyesters.However,the traditional salen-Al complexes generally suffer from low catalytic activity or complete deactiveation at low catalyst concentration or high concentration of chain transfer agent,owing to the concentration effects and the decomposition of the catalyst caused by protic agents.It is desirable to develop catalytic system with high stability and good compatibility with protonic agents,which is important for decreasing catalyst loading,reducing the cost,minimizing the catalyst residual and increasing the molecular weight.Recently,we synthesized a series of bipyridine bisphenolate aluminum(BpyBph-Al)complexes and used these complexes to catalyze the lactide polymerization,melaic anhydride/epoxide copolymerization and thioanhydride/epoxide copolymerization.This feature article summarizes the recent progress on synthesis of polyesters by using(BpyBph-Al)complexes and discussed the their unique advantages in ring-opening(co)polymerization.