几种生物降解聚酯/POSS复合材料的制备、结晶行为和性能的研究

As a novel type of three-dimensional nanofiller, polyhedral oligomeric silsesquioxanes (POSS) have a structure of cube-octameric frameworks consisting of an inorganic cube-like core and eight organic corner groups. POSS molecules may be incorporated into some polymer matrixes either by copolymerization or physical blending; consequently, enhancements on polymer properties may be achieved, such as increased thermal stability, mechanical properties, and reduced flammability, etc. The preparation, structure and properties of POSS-based polymer nanocomposites have become one of the most active research topics in the polymer research fields in the word; however, few works have dealt with the POSS-based polymer nanocomposites with biodegradable polyesters being the matrix. On the basis of our previous research work, we will study the preparation, morphology, structure, properties, and degradation behavior as well as degradation mechanism of the nanocomposites consisting of biodegradable polyesters, such as poly(ethylene succinate) (PES) and poly(butylene adipate) (PBA), and some POSS containing different organic groups in this research project. For a better understanding of the preparation, structure, and properties relationship and their practical application, we will pay more attention to the effects of the POSS types and the POSS loadings on the crystalline morphology, crystallization behaviors, the crystal polymorphism, mechanical properties, thermal stability, degradation, and degradation mechanism of biodegradable polyester in the biodegradable polyester/POSS nanocomposites. It is believed that the investigation of this research proposal is not only very challenging but also very important from both academic and practical viewpoints.

笼型倍半硅氧烷(POSS)是一类兼具纳米尺度和三维结构的有机/无机杂化分子，将POSS引入到高分子中，有可能使POSS在纳米尺度上起到对聚合物的改性作用，从而使高分子高性能化。POSS/聚合物复合材料的制备、结构与性能的研究已成为国际上高分子科学领域中最活跃课题之一，但是以生物降解聚酯为聚合物基体的复合材料的研究工作尚未系统开展。本项目拟在前期研究工作基础上，对生物降解聚酯PES、PBA与ovi-POSS、PEG-POSS复合材料的制备、形态结构、性能和降解行为等研究过程中所存在的关键科学问题开展更加深入和全面的研究工作，明确POSS类型及含量对复合材料中聚酯的结晶形态、结晶行为、多晶型调控、力学性能、热稳定性、降解行为及降解机理的影响规律，建立此类复合材料的制备―结构―性能的关系，促进其实际应用。开展本领域的研究工作,不仅富有挑战性，而且具有十分重要的理论和实际意义。

本项目对于笼型倍半硅氧烷(POSS)/生物降解高分子复合材料的制备、结晶行为与性能的调控开展了系统研究工作。所选择的生物降解聚酯主要为聚丁二酸乙二酯(PES)和聚己二酸丁二酯(PBA)。所选取的POSS主要为8-乙烯基取代的POSS(ovi-POSS)、8-聚氧乙烯取代的POSS (PEG-POSS)。通过溶液挥发法制备了一系列具有不同POSS组成的生物降解高分子基纳米复合材料。研究结果表明：（1）对于ovi-POSS/生物降解高分子纳米复合材料体系，ovi-POSS不仅可在高分子基体中均一分散，而且以晶体形式存在；ovi-POSS明显提高了基体的非等温熔体结晶温度和等温结晶速率，提高了球晶密度，起到异相成核剂的作用，但不改变其结晶结构和结晶机理；ovi-POSS显著提高了基体的杨氏模量和动态储能模量，但降低了断裂伸长率；在一定程度上促进了基体的水解过程。（2）对于PEG-POSS/生物降解高分子纳米复合材料体系，PES-POSS可在生物降解高分子基体中良好分散；随PEG-POSS组成的提高，复合材料的玻璃化转变温度、平衡熔点降低，表明PEG-POSS中的PEG与基体具有良好的相容性；PEG-POSS促进了基体的非等温熔体、冷结晶过程；提高了复合材料中高分子的球晶生长速率、等温熔体结晶速率，但不改变晶体结构和结晶机理；在一定程度上降低了基体的热分解温度；与PEG-POSS复合后，提高了基体的断裂伸长率，但降低了杨氏模量和动态储能模量，表明了PEG-POSS的增塑作用。（3）在完成项目原定研究计划的基础上，进一步将所研究高分子体系扩展至聚（丁二酸乙二醇-co-丁二酸二甘醇）共聚酯（P(ES-co-DEGS)）、聚乳酸（PLLA）和聚辛二酸乙二醇酯（PESub），所研究POSS类型扩展至八异丁基POSS（oib-POSS）和三硅羟基异丁基POSS（tsib-POSS），并系统研究、总结了所制备的新型POSS/生物降解高分子纳米复合材料的结晶行为与性能调控的规律，以促进相关材料的实际应用。总之，顺利完成了本项目的研究内容。通过本项目的研究，对POSS/生物降解高分子纳米复合材料的制备、结晶行为与性能调控有了更加深入的认识和理解，从而促进了生物降解高分子材料的实际应用。