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

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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.