环状磷腈超强碱催化的γ-丁内酯及其衍生物的开环聚合

As an important bio-based polymer, poly(γ-butyrolactone) has better performance compared to poly(ε-caprolactone) and poly(lactide) in biomedical applications, such as absorbable sutures and tissue engineering scaffolds. However, the currently reported ring-opening polymerization of γ-butyrolactone and its derivatives were catalyzed by organometallic catalysts, which limit their applications in biomedical technology. It is of significance to develop novel metal-free catalyzed polymerization method..In this project, the effects of the catalyst structures and their basicity, solvent polarity, reaction temperature and monomer concentration on ring-opening polymerization of γ-butyrolactone and its derivatives will be investigated with using organic phosphazene superbases as catalysts. The kinetics and thermodynamics of polymerization will be also studied. Moreover, the block copolymers will be prepared through copolymerization of γ-butyrolactone and its derivatives with other cyclic lactones or lactides. The thermal and mechanical properties of obtained homopolyesters or copolyesters will be systematically investigated. This project will provide guidelines on ring-opening polymerization of cyclic lactones with five-membered rings.

聚（γ-丁内酯）是一类重要的生物基高分子，与聚己内酯和聚乳酸相比，在可吸收手术缝合线、组织工程支架等生物医药领域具有更加优异的性能。但目前γ-丁内酯及其衍生物的开环聚合以有机金属催化剂为主，限制了其在生物医药领域的应用。发展新的无金属催化的聚合方法具有重要的科学意义。.本项目拟利用有机环状磷腈超强碱为催化剂，阐明催化剂结构和碱性、溶剂极性、反应温度、单体浓度对γ-丁内酯及其衍生物开环聚合的影响，系统研究聚合反应动力学和热力学。进一步研究γ-丁内酯及其衍生物与其他环状单体的共聚行为，实现嵌段共聚物的制备。研究所得聚酯均聚物和共聚物的热力学和力学性质。本项目的开展能够为五元环内脂的开环聚合提供理论指导。

发展具有“单体-聚合物-单体”的闭合循环特性的化学循环高分子是解决目前塑料污染问题最具吸引力的方案。γ-丁内酯是一种生物质来源单体，其上游产品丁二酸在美国能源部提出的十二种生物基平台化合物中位列首位。γ-丁内酯及其衍生物开环聚合得到的聚酯材料可以定量解聚得到单体，是一类重要的化学循环高分子材料。但由于γ-丁内酯及其衍生物具有低环张力的五元环结构，热力学上不易开环，其开环聚合仍然是高分子化学的一大挑战。. 本项目通过发展有机强碱/脲二元协同催化体系，实现了“低环张力”γ-丁内酯及其衍生物的可控选择性开环聚合，制备得到高分子量聚（γ-丁内酯）；首次实现有机催化α-亚甲基-γ-丁内酯（MBL）的化学选择性开环聚合，制备得到含侧基官能团的可循环聚酯；分别利用“顺序开环聚合法”和“大分子引发剂法”首次制备了聚（γ-丁内酯）-b-聚乳酸嵌段共聚物以及聚乙二醇-b-聚（γ-丁内酯）两亲性嵌段共聚物；成功实现了MBL和ε-己内酯或δ-戊内酯的选择性无规共聚，制备得到的无规共聚酯表现出随组成变化的热力学性质。受项目资助，申请人在Angew. Chem. Int. Ed., CCS Chemistry, Macromolecules等国内外学术期刊上共发表第一/通讯作者论文9篇，获授权发明专利3项。.