环状和线型聚磷腈催化剂的设计合成及其在酯类开环聚合中的应用

Synthesis of biodegradable aliphatic polyesters via metal-free catalyzed ring-opening polymerization of cyclic esters is of great importance to their applications in biomedical and microelectronic fields, and is therefore becoming the most appealing research topic in polyester synthesis. As a category of organic superbases, phosphazene exhibits good biocompatibility and considerably high catalytic activity in ring-opening polymerization of cyclic esters. The catalytic performances of phosphazene catalysts highly depend on their structure and basicity. However, the application of phosphazene catalysts is limited due to the lack of structural diversity and successive basicity. Therefore, it is of great urgency and necessity to design and develop novel phosphazene catalysts..From the point of catalyst design, this project proposes a series of novel cyclic and linear polyphosphazene catalysts. The basicity of the catalysts could be controlled and tuned by the introduction of different substituent groups. The catalytic activities of new catalyst will be verified by catalyzing the ring-opening polymerization of cyclic esters with different ring size and strain, such as lactide, ε-caprolactone, γ-butyrolactone, and so on. The effect of the structure and basicity of phosphazene on the controllability of the polymerization will also be systematically studied. Besides, this project will achieve controllable synthesis of biodegradable aliphatic polyesters by the selection of catalyst and optimization of polymerization conditions. The development of this project can provide new idea and routes for developing new organocatalysts.

无金属催化聚合对可降解脂肪族聚酯在生物医药、微电子等领域中的应用意义重大，并逐渐成为脂肪族聚酯合成领域的发展方向。磷腈作为一类有机碱催化剂，生物相容性好，在酯类开环聚合中具有很高的催化活性，是目前研究的热点。磷腈催化剂的结构和碱性是决定其催化性能的关键因素，但目前已报道的磷腈催化剂种类少，结构单一，碱性难以调控。因此，设计开发结构多样、碱性可调控的新型磷腈催化剂具有极大的紧迫性和必要性。.本项目从催化剂设计角度出发，拟设计合成一系列环状和线型聚磷腈催化剂，通过改变取代基团实现对催化剂碱性的调控。进一步研究新型聚磷腈催化剂对丙交酯、ε-己内酯、γ-丁内酯等具有不同环张力酯类单体的催化活性，阐明磷腈催化剂的结构和碱性对聚合反应可控性的影响。在此基础上选择合适的催化剂，优化聚合条件，实现脂肪族聚酯的可控合成。本项目的开展将为新型有机催化剂的开发提供新的思路和方法。

磷腈是一类碱性很强的中性Brönsted碱，可催化环醚、环酯、环碳酸酯、环硅氧烷、内酰胺等多种单体的聚合反应。设计开发结构多样、碱性可调的新型磷腈催化剂对于实现脂肪族聚酯的可控合成具有十分重要的意义。本项目首先以六氯环三磷腈为原料，采用顺序取代的方法合成出了含有不同取代基团的环状聚磷腈和线型聚磷腈。然后研究了新型聚磷腈催化剂对于不同酯类单体的催化性能。采用环状聚磷腈催化剂CTPB高效催化了五元环单体γ-丁内酯的开环聚合反应，在-60°C时单体转化率高达98%，且可获得高分子量、窄分布的聚合物，该方法可以选择性制备线性聚γ丁内酯。CTPB/醇催化体系能够非常高效地催化ε-己内酯开环聚合，可获得超高分子量聚己内酯，数均分子量可达10万以上，可合成出线型、星型等具有不同拓扑结构的聚己内酯，还可实现有机催化的ε-己内酯“不死聚合”。CTPB可以高效催化大环ω-十五内酯的开环聚合，在80°C时，TOF值可达600/h，通过顺序加入单体的方法，可以合成结构明确的大环ω-十五内酯与L-丙交酯、ε-己内酯、δ-戊内酯的嵌段共聚酯。采用CTPB作为催化剂，实现了生物基薄荷醇内酯的开环聚合，制备了具有不同分子量的聚薄荷醇内酯，还可以制备结构可控的星型聚合物，通过端基官能化得到双键封端的星型聚薄荷醇内酯，经紫外光照后交联固化得可降解聚酯弹性体。上述研究成果在Macromolecules、Polymer Chemistry、Chinese Journal of Polymer Science等杂志上共发表SCI 学术论文10篇，申请国家发明专利4项，授权1项。