咪唑烷基桥联双芳氧基稀土胺化物高效催化ε-己内酯开环聚合

High Effective Ring-Opening Polymerization of ε-Caprolactone by Rare-Earth Metal Amides Bearing an Imidazolidine-Bridged Bis( phenolato) Ligand

研究了一系列咪唑烷基桥联双芳氧基稀土金属胺化物催化ε-己内酯开环聚合反应性能。通过对聚合物的分子量和分子量分布进行分析,结果显示,这些稀土胺化物能在相对较温和的条件下高活性引发ε-己内酯开环聚合,其催化活性随着稀土金属离子半径变大而增强,但所得聚合物的分子量分布较宽（PDI=1.21-1.89）,显示它们不是可控聚合体系。加入异丙醇原位转化成稀土金属烷氧基配合物后,聚合的可控性得到了明显的改善,显示了可控聚合的特点。通过分析齐聚物的末端基,研究了这类稀土胺化物加醇体系催化ε-己内酯聚合的机制。

Ring-opening polymerization（ ROP） of ε-caprolactone（ ε-CL） initiated by a series of neutral rare-earth metal amides supported by an imidazolidine-bridged bis（ phenolato） ligand was investigated. It was found that all of these rare-earth amido complexes were efficient initiators for the ring-opening polymerization of ε-CL,and giving the resultant polymers with high molecular weights and relatively broad molecular weight distributions（ Mw/ Mn=1. 21 - 1. 89） which indicated that the polymerization is not well-controlled,and the ionic radii of the central metals had a significant effect on the catalytic activity. A further study revealed that these rare-earth metal amides can initiate ε-CL polymerization in a controlled manner in the presence of 1 equiv of isopropyl alcohol. The initiation mechanism was also elucidated by end-group analysis of oligomer of ε-CL by1 H NMR.