生物降解PBS基离聚物的分子结构设计与性能调控

Ionomer is a polymer with small amount of ionic groups (usually less than 10%) attached to the backbone of polymer chain. It is well-known that such ionic groups tend to form phase-separated ionic aggregates in the hydrophobic polymer matrix. The ionic aggregates act as physical crosslinks which could improve the melt viscosity, melt strength, mechanical strength and toughness of polymer matrix significantly. The structure of ionic aggregate plays an important role in the properties of ionomer. The structure of ionic aggregate depends strongly on the structure of ionomer. There are some reports on the molecular design and property regulation of traditional vinyl ionomers. Aliphatic polyesters such as poly(butylene succinate) (PBS) are regarded as the most promising biodegradable polymers, due to their thermal stability, mechanical strength, and relatively high melting temperature. They can be widely used to replace non-degradable conventional plastics in general purpose application. However, aliphatic polyesters also have disadvantages. Taking PBS as an example, the melt strength and tear resistance are very poor, and the biodegradation rate is very small. Those shortcomings restricted the application of PBS significantly. PBS based ionomer has been reported in recently literatures, but only random PBS ionomer was synthesized and investigated. No report has been reported on the molecular design and property regulation for biodegradable aliphatic polyester ionomer, although the molecular structure of ionomer determines the ionic aggregate structure thus the properties of ionomers. In this project, we plan to synthesize high-molecular-weight PBS based ionomers with designed structures via chain-extension reaction. We designed three ionomers, i.e., PBSI random ionomer, PBS-b-PBSI multiblock copolyester ionomer, and PBS-b-PESI multiblock copolyester ionomer. The three ionomers will be synthesized by chain extension reaction of corresponding hydroxyl terminated prepolymers with hexamethylene diisocyanate as a chain-extender. Through molecular design, the distribution of ionic group on polymer chain and thus the structure of ionic aggregate can be regulated, and consequently, the comprehensive properties of PBS can also be tailored. The effect of molecular structure on the ionic aggregate structure and the melt behavior, thermal and mechanical properties, crystallization behavior, and biodegradation behavior of PBS based ionomers will be investigated systematically. The structure-property relationship of PBS based ionomers will be finally established. The results of the project are expected to enrich the basic principle of aliphatic polyester ionomers. In addition, a new biodegradable material with controllable properties is anticipated after the investigation of the project. Therefore, the project is meaningful not only theoretically but also practically.

离聚物的分子结构对离子聚集体结构与离聚物性能具有决定性作用，目前关于脂肪族聚酯离聚物分子结构设计、离子聚集体结构与离聚物性能调控的研究仍是空白。本项目以聚丁二酸丁二醇酯（PBS）基离聚物为研究对象，设计合成三种不同分子结构的PBS基离聚物，通过对离子基团分布与离聚物主链结构的调节，进行离子聚集体结构与离聚物性能的调控。具体而言拟合成PBSI无规离聚物、PBS-b-PBSI与PBS-b-PESI多嵌段共聚酯离聚物三种不同分子结构的离聚物；通过对PBS基离聚物的分子结构与离子聚集体结构关系的研究，与分子结构及其对应的离子聚集体结构对离聚物熔体性质、力学性能、热性能、结晶性能、亲疏水性与降解性能等影响的深入研究，揭示分子结构对离子聚集体结构与PBS基离聚物性能的影响规律，掌握脂肪族聚酯离聚物性能调控的关键技术，为该类材料的应用提供理论与技术支持。因此，本项目兼具科学意义与应用价值。

脂肪族聚酯的线形分子链结构导致其熔体粘度与强度低、耐撕裂性能差、成型加工尤其是吹膜性差，严重地限制了脂肪族聚酯的应用。将离子基团引入脂肪族聚酯分子中，利用离子间相互作用形成物理交联，可大幅改善脂肪族聚酯的熔体性质、加工性能与力学性能等。而离聚物的性能依赖于离子基团种类及其在聚合物分子链上的分布，鉴于以前未见关于脂肪族聚酯离子基团结构与分布调控的相关研究报道。.本项目将磺酸根引入聚丁二酸丁二醇酯（PBS）中，合成不同离子基团含量的羟基封端PBSI预聚物，再将其与羟基封端PBS预聚物扩链合成了PBSI离聚物，通过对PBSI预聚物离子基团含量的控制，实现了对磺酸根基团在PBSI离聚物分子链上分布的调控。系统地研究了离子基团分布对PBSI离聚物的微观形貌及其理化性能的影响，研究发现离子基团分布对离子聚集体的尺寸影响极大，分布越集中，形成的离子聚集体尺寸越大。而离子聚集体的形态又极大地影响了离聚物的结晶性能、流变性能、降解性能与力学性能等，即通过调控离子基团分布成功实现了对PBS综合性能的调控。本项目还将仲铵阳离子引入PBS分子链中，成功合成了PBSUI阳离子聚合物，研究发现阳离子基团的引入对PBS的综合性能影响极大，尤其在改善PBS结晶性能与流变性能方面效果极其显著，阳离子基团形成离子聚集体既起成核剂作用，大幅提升了PBS结晶速率，同时又起到物理交联作用，大幅改善了离聚物的熔体性质。此外，阳离子的引入还可在基本不影响拉伸性能的情况下，改善了PBS的降解性能。.综上，本项目设计合成了一系列不同离子基团种类与分布的PBSI离聚物，通过对离子基团种类与分布的调控，实现了对PBS综合性能的调控，通过研究离聚物分子结构对其离子聚集体形态与离聚物结晶性能、流变性能、降解性能与力学性能等的系统研究，揭示了PBS离聚物结构与性能关系的基本规律。研究成果不仅丰富了离子聚合物结构与性能调控的基本理论，而且对拓展PBS的实际应用具有指导意义。因此，本项目的研究成果不仅具有学术价值，而且具有应用价值。.项目研究成果已在Polymer，Carbohydrate Polymers与Composites Science & Technology等国际著名刊物上发表了SCI收录学术论文12篇，并获得了一项授权国家发明专利。培养了两名博士研究生，两名硕士研究生，圆满完成了项目的研究目标与任务。