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

本项目的目的是阐明原位聚合制备的聚合物复合材料的高阶结构与力学性能之间的关系，从而建立纳米复合材料的分子设计原理。(1)通过两种原位聚合方法制备了高性能的增强聚合物/柔性基质聚合物复合材料：原位聚合方法(I)，其中增强聚合物单体在柔性基质聚合物溶液中聚合；原位方法(II)，柔性基质聚合物单体在增强聚合物溶液中聚合。原位法(I)比原位法(II)制备的聚合物复合材料具有更高的拉伸强度，这是因为原位法(I)使增强聚合物在聚合物复合材料中的分散性更好。(2)酸碱相互作用是原位聚合制备增强聚合物和柔性基质聚合物高性能复合材料的最佳方法。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)通过在聚酰亚胺(PI)的侧链中引入游离羧酸来改善聚4-乙烯基吡啶-共聚苯乙烯(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拉伸强度的影响。所得复合膜的拉伸强度随着聚酰亚胺中羧基含量的增加而增加，且高于单一聚合物组分的拉伸强度。

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.