流动场下热塑性聚酰亚胺结构形态调控研究

Thermoplastic polyimide (PI), as an important special engineering plastic, have been widely used in aerospace, military weapon, automotive, and electronic fields, due its outstanding mechanical properties, excellent thermal stability, high resistance to radiations, etc. Up to now, most research of PI mainly focus on the manipulation of the molecular chains’ structure (such as molecular weight, molecular weight distribution and introduction of functional groups) in the synthesis stage, which overlook the manipulation of the aggregates’ structure during the processing stage. Therefore, the evolution mechanism of the aggregates’ structure during the processing is far from clarification, which leads to the lack of corresponding theory and technique. In this project, we plan to adopt in situ detection technologies including in situ synchrotron infrared radiation spectrum and in situ synchrotron X-ray diffraction to probe the orientation and relaxation, preorder, the formation and growth of oriented nuclei, and the crystallization kinetics of rigid molecular chains in PI upon shear flow. We will pay a close attention on the transformation of the PI aggregates’ structure upon shear flow, in order to reveal the critical flow field for the formation of oriented crystals. At last, we will study the influence of shear-induced oriented crystals on the mechanical properties, in order to uncover the relationship between the aggregates’ structure and mechanical properties. Our work are promising to give some valuable theory guidelines and technical supports for deepening and broadening the application field of PI.

热塑性聚酰亚胺（PI）具有优异的机械性能、耐高低温性能及耐辐射性能等，作为一种重要的特种工程塑料广泛应用于航空航天、武器装备、汽车、电子等领域。目前，PI研究主要关注的是合成阶段对PI分子链结构（如：分子量、分子量分布、功能基团引入等）的调控，比较忽略成型加工阶段PI聚集态结构的调控，以至于在加工过程中PI聚集态结构形态演变机理远不明确，相应的加工理论和技术也有所缺失。基于上述理由，本项目拟采用原位在线检测技术（同步辐射红外光谱、同步辐射X射线衍射）实时跟踪研究在流动场下PI刚性分子链的取向与松弛、预有序、晶核结构的形成、取向晶核生长及结晶动力学过程；重点研究流动场诱导PI聚集态结构的突变，即形成取向晶体结构的临界流动场条件；考察流动场诱导的取向晶体结构对各种物理机械性能的影响，揭示PI聚集态结构与性能的关系，为深化和拓展PI的应用领域奠定理论基础。

作为一种重要特种工程塑料的聚酰亚胺（PI）具有优异的机械性能、耐高低温性能及耐辐射性能等，广泛应用于航空航天、武器装备、汽车、电子等领域。因目前对于PI外场下聚集态结构调控及结构与性能关系研究的不足，大大限制了PI应用的拓展。.针上述情况，本项目从PI单体的选择、到合成工艺的探索，再到加工工艺的调控，最后到高性能PI材料的制备，开展了系统与全面的研究工作。采用共缩聚反应将支化结构、异构单体、含氟基团、封端基团、醚键等引入到PI分子链上，揭示了单体柔韧性、基团极性与大小、分子链间相互作用与聚集态结构等对于PI材料的力学性能、热性能、溶解性能与光学透明性等的影响规律。在保持PI优良的综合性能的同时，显著提升了PI的溶解性及光学透明性，克服了PI黄度指数高、难以成型加工的缺点，制备出了高透明、易加工、综合性能优良的PI材料。在PI分子链骨架上引入具有显著刚性和空间位阻的超支化硅氧烷大分子单体或者通过改变PI单体配比调节分子骨架的刚柔性，获得了系列介电常数可调的高性能PI薄膜，为易加工、低介电PI膜材料的构筑提供了新思路。采用“球磨共混-高压压制-低温烧结”的加工方式，使PI分子链与氮化硼（BN）微片在面内定向排布，制备了具有各向异性的高导热PI复合材料。当BN含量30wt%时，复合材料的面内导热系数高达2.81W/mK，面外导热系数达到0.73W/mK，分别为纯PI样品的3.2倍与2.4倍。采用“包覆-高压压制”构筑了BN微片充分包覆PI颗粒的三维导热隔离网络结构，制备了各向同性的高导热PI复合材料。当BN为20vol%时，复合材料导热系数可高达4.47W/mK，相对于纯PI提升了2099%。这些工作为高导热PI复合材料的制备提供了新方法，也为电子电器所亟需的热界面材料提供了来源。在Macromolecular Rapid Communications, Composites Part B等国内外核心期刊上发表了学术论文11篇，SCI收录11篇，EI收录10篇，准备申请发明专利2项。