Synthesis And Properties Of Novel Polyimides And Polyacetylene Liquid Crystals

High molecular weight liquid crystalline materials have been only 60 years from its origin and increasing attentions have been paying to it. Liquid crystal polymers have exhibited special properties, great values of applications, and huge development spaces.Liquid crystalline polymers mainly consist of two types: main chain and side-chain liquid crystalline polymers. There are some exceptions, such as the mesogen-jacketed liquid crystalline polymers.The science of liquid crystalline polymers is still young, and more research and development on it are needed. The physical properties and practical applications depend on both side chain and main chain. The side chain mesogen modification and polymer chain characters determine their properties. The molecular designing, synthesis, structure-property relationship in this field still need more research.This thesis reported three kinds of liquid crystalline polymers: polyimides, polyacetylene and mesogen-jacketed liquid crystalline polymers. The structure characterization of the monomers and polymers was carried out with NMR, IR, MS, GPC. The properties have been investigated with POM, DSC, TGA. The discussion on the results led to the conclusions of the thesis.The thesis consists of four chapters: Chapter One briefly introduced the elementary knowledge about polymers and liquid crystal materials, then liquid crystalline polymers and several representative types was introduced. The content and feature of the thesis were pointed out.Chapter Two reported novel polyimide liquid crystals. As polyimide main chain is rigid, it is difficult to show liquid crystalline properties. Through molecular designing of connecting the mesogen to the polyimide main chain by a flexible spacer, two series to polyimide polymer films were prepared. Finally, the liquid crystal behavior, phase transition temperature, thermal stability and mechanical properties were studied.Chapter Three carried out the research on polyacetylene liquid crystals. Through the designing of side chain mesogens, four series of polyacetylene liquid crystals were synthesized and characterized. The molecular structure configuration was simulated by computer calculation. The liquid crystalline properties, thermal stability, and the influence of intrachain hydrogen bonding on mesomorphism were summarized and discussed.Chapter Four reported the synthesis and characterization of polyacetylene with triphenylene discogens. The acetylene monomers with triphenylene discogens have been polymerized by [Rh(nbd)Cl]₂. The activity of fuctional group for polymerization, the influence of organic base and the solvent system on polymerization have been investigated, and some big breakthroughs have been made in this field. A triphenylene discotic mesogen-jacketed polyacetylene liquid crystalline polymer was reported first time.The primary research on polyacetylene discotic liquid crystals and discogen-jacketed liquid crystalline polymers in this thesis are interesting and intriguing. It is worth further more and deep investigation.