Study on Control of Higher Order Structure of Composites by In-situ Polymerization and Their Mechanical Properties

本课题旨在阐明原位聚合法制备的高分子复合材料的高阶结构与力学性能之间的关系，进而建立纳米复合材料的分子设计原理。在本项目中获得了以下结果：(1)通过两种原位聚合方法制备了增强聚合物和柔性基体聚合物的高性能复合材料：原位聚合法(I)，在柔性基体聚合物溶液中进行增强聚合物单体的聚合；原位聚合法（II），在增强聚合物溶液中进行柔性基体聚合物单体的聚合。原位法(I)得到的聚合物复合材料的抗拉强度高于原位法（II），因为原位法(I)得到的增强聚合物在聚合物复合材料中的分散更加精细。(2)发现酸碱相互作用最适合原位聚合法制备增强聚合物和柔性基聚合物的高性能复合材料。此外，原位聚合法制备的复合膜的拉伸强度远高于共混法制备的复合膜。(3)在聚酰亚胺（PI）侧链中引入游离羧基，以改善聚（4-乙烯基吡啶-co-苯乙烯）（P4VPy-St）和PI复合材料的力学性能，并研究了羧基含量对复合膜抗拉强度的依赖关系。复合膜的抗拉强度随PI中羧基含量的增加而增加，且高于任何单个聚合物组分。

The purpose of this project is to clarify the relationship between the higher order structure and the mechanical properties of the polymer composites prepared by in-situ polymerization and then to establish a principle of molecular design of nano-composite materials. The following results were obtained in this project.(1)High-performance composites of reinforcing polymers and flexible matrix polymers were prepared by two in-situ polymerization methods : by the in-situ method(I), where polymerization of monomers of reinforcing polymers was carried out in a solution of flexible matrix polymers, and by the in-situ method(II), where polymerization of monomers of flexible matrix polymers was carried out in a solution of reinforcing polymers. The in-situ method(I) was found to give polymer composites with higher tensile strength than the in-situ method(II), because the in-situ method(I) gave much more fine dispersion of reinforcing polymer in the resulting polymer composites.(2)The acid-base interaction was found to be best for preparation of high performance composites of reinforcing polymers and flexible matrix polymers by the in-situ polymerization. Furthermore, the tensile strengths of the composite films prepared by the in-situ polymerization method were much higher than those of the films prepared by the blend method.(3)Free carboxylic acid groups were introduced into side chains of polyimide(PI) in order to improve the mechanical properties of the poly(4-vinylpyridine-co-styrene) (P4VPy-St) and PI composites, and the carboxyl group content dependence of the tensile strength of the resulting composite films was investigated. The tensile strength of the resulting composite films increased with increasing carboxyl group content in PI and was higher than that of either of the individual polymer components.