一釜合成多嵌段CO2基共聚物及其结构与性能

Multiple block copolymers have attractive features of polycarbonate with varied Tgs and polyester with varied Tms. Such copolymers are potential to enlarge the application of CO2-based copolymers due to its easy-to-tuned strucutre and properties. However, to our knowledge, there are still no reports on synthesizing such CO2-based multiple block copolymers. This project provides a new catalytic hetero-block-exchanging polymerization to afford CO2-based multiple block copolymers by two catalysts in one system for catalyzing the mixed monomers for the first time. For this aim, this project will focus on two key issues: 1) the screening of the catalyst pairs: one is for CO2/epoxide copolymerization (Cat.1), and the other is for ring-opening polymerizatoin of cyclic ethers (Cat.2). Both catalysts cannot poison each other in one system but support fast chain transfer reaction and chain exchange reaction. In this system, three mixed monomers, CO2, epoxide and cyclic ether will be polyermerized by two catalysts, produing polycarbonate and polyester independently.Supposed that two catalysts have no ability to resolute the hydroxyl-terminated polycarbonate or polyester, hetero-block-exchanging reaction will occur and produce multiple blocks. 2) the control of hetero-block-exchanging reaction for well-controlledly producing multiple block copolymers, including the selectivity of epoxides and cyclic ethers, the systematic investigation on the effect of the catalytic factors (e.g.: temperture, CO2 pressure, the amounts of monomers and initiators) on the MW, PDI, average block length and numbers of the resutlant block copolymers. The mehcanical, thermal and biodegradable properties of these CO2-based multiple block copolymers will be systematically characterized and evaluated in correspondence to the chain structure and aggregation stucutre of the resultant block copolymers. The results of this project will provide a new methodology that utilize two different catalysts for making one CO2-based multiple block copolymer, and enrich the content of the polymer chemistry and C1 chemistry.

本项目提出一釜交叉链交换(不同组分链之间，异链交换)共聚制备嵌段"纯净"且段序列可控的多嵌段二氧化碳(CO2)基共聚物的催化合成方法。采用互不毒化的两种催化剂（催化剂对）同时催化CO2、环氧化物和环酯一釜共聚，在原位生成聚碳酸酯和聚酯链的同时，利用两催化剂对"休眠"链端羟基的不可辨性，实现异链间的链交换反应，得到聚碳酸酯段和聚酯段"纯净"且交替排列的多嵌段共聚物。深入研究催化剂对的筛选确立和异链交换反应调控两个关键问题，系统研究和总结催化剂对、引发剂、单体结构及摩尔比和动力学等因素对产物分子量及分布、平均嵌段长度和嵌段数等链结构的影响规律，调控产物分子链微结构乃至聚集态结构；研究多嵌段共聚物结构参数、结晶性能和生物降解性、力学性能和热性能之间的关系。研究结果将提供一种简单高效催化混合单体"一锅"共聚大量制备多嵌段CO2基共聚物的方法，对高分子合成化学理论产生新的贡献。

一碳（C1）基共聚物尤其是CO2基共聚物的生物降解性和使用性能难以并存兼容，导致此类聚合物的应用有难度，至今仅少量品种进入了生产和应用领域。针对这一难题，本项目提出了交叉链交换共聚的催化合成方法，制备了嵌段“纯净”且段序列可控的多嵌段CO2基共聚物。采用互不毒化的两种催化剂，同时催化CO2、环氧化物和环酯一釜共聚，在原位生成聚碳酸酯和聚酯链的同时，利用两催化剂对“休眠”链端羟基的不可辨性，实现了异链间的链交换反应，得到聚碳酸酯段和聚酯段“纯净”、且交替排列的多嵌段共聚物。筛选得到了两种催化剂，实现了异链交换反应的调控，系统研究和总结了两催化剂、引发剂、单体结构及摩尔比等动力学因素对产物分子量及分布、平均嵌段长度和嵌段数等链结构的影响规律，调控了产物分子链的微结构和聚集态结构；研究了多嵌段共聚物的结构参数、结晶性能和生物降解性、力学性能和热性能之间的关系。研究结果提供了一种催化三单体“一锅”共聚、大量和高效制备多嵌段CO2 基共聚物的方法。在这一结果的指导下，我们已在工业中试验生产新的CO2共聚物。本项目期间，还实现了ABA三嵌段共聚物的精确合成，获得了无金属Lewis酸碱催化途径合成嵌段共聚物的方法，得到了一系列不同结构和功能的C1基聚合物，研究了它们的结构与性能关系，探索了若干光学功能的C1聚合物，系统总结了不同拓扑结构CO2基共聚物的合成方法。由本项目建立的嵌段共聚物的制备方法，可以通过调整链段结构，来协调共聚物的生物降解性和结晶性，进而调节性能。这些结果对C1基共聚物的工业化应用有着显著和积极的意义。