稀土催化两仪聚合研究

“Janus polymerization”, firstly reported by the applicant, combines anionic and cationic polymerizations on the two ends of one propagating chain. Both ends carry out living polymerizations without the interference from each other. The growing chain ends perform coupling reactions only after the consumption of monomer(s), which converts chain-growth polymerization into step-growth polymerization. It is the only existing one-step method to produce multi-block copolymers directly from monomers. In this proposal, the applicant is going to use rare earth complexes to catalyze Janus polymerization of cyclic monomers including lactones, lactides, cyclic ethers, amino acid-N-(thio)carboxyanhydrides, etc. The project is to develop new catalytic and polymerization systems based on the balance between catalysts and monomers. The key point of the project is to investigate kinetics and mechanisms of Janus polymerization by means of both experimental characterizations and calculations of density functional theory. Deep understanding and more examples of Janus polymerizations lead to novel synthetic approaches to synthesize structural polymeric materials containing ester, ether and peptide linkages with multi-block, cyclic, star-shaped, (hyper-)branched, and cylindrical brush-like topologies. This research project aims to set up a novel methodology of Janus polymerization to extend the theory of ionic and coordination polymerization mechanisms.

申请人首创的“两仪聚合”能在增长链两端分别进行阴离子聚合与阳离子聚合，且当单体耗尽时聚合链之间自发偶合反应，由连锁聚合转变为逐步聚合，从环状单体一步法直接合成多嵌段共聚物。本项目用稀土配合物为催化剂，以环酯/环醚/氨基酸-N-(硫代)羧酸酐等为单体，深入研究两仪聚合反应特征，明晰催化剂/单体/聚合条件之间的平衡关系，联用实验表征和密度泛函理论计算，揭示两仪聚合的微观反应机理。设计并实现多种稀土催化剂催化环状单体两仪聚合，合成具有多嵌段、环状、星形、（超）支化、柱状聚合物刷等复杂拓扑结构的聚酯/聚醚/聚氨基酸生物医用材料。本项目研究成果将建立全新的两仪聚合方法学，发展离子聚合与配位聚合理论，拓展稀土催化剂在聚合方面的应用。

本项目在系统研究了两仪聚合动力学行为和聚合物结构表征的基础上，结合密度泛函理论计算结果，深入阐明了两仪聚合机理，确定了稀土配合物中间体结构及其对聚合反应速率的影响作用，总结形成了两仪聚合方法学。考察了数十种催化剂、引发剂和单体组合，成功实现了三类全新的两仪聚合体系，合成了具有多嵌段、瓶刷状、环状、超支化等拓扑结构可控的聚酯、聚醚和聚氨基酸产物。成功实现了甲基四氢呋喃、gamma-丁内酯、共轭-delta-戊内酯等多种难聚合的环醚和取代内酯的离子型开环聚合。构建了各聚合体系的催化-结构-性质之间的关系，为制备具有优异生物相容性、可控降解性、可设计结晶性与溶解性的生物医用高分子材料提供了灵活可行的合成方法。本项目高质量完成了研究任务，在Angew Chem、Macromolecules、Chinese J Chem、高分子学报中英文版等国内外著名期刊发表SCI收录论文共计14篇，获得3项中国发明专利授权，超过预期目标。项目负责人与成员参加5次国内外学术会议，完成了4次邀请报告和2次口头报告。培养博士研究生毕业3名、在读3名。