| Poly (p-phenylene terephthalamide) (PPTA) has been noted as a kind of important polymeric material which presents a combination of outstanding properties such as high thermal stability, good chemical resistance, low flammability and excellent mechanical properties. In application, lyotropic liquid crystalline property of PPTA or similar polyamides has received considerable commercial and scientific interest since it was reported and applied in the developing of Kevlar~? by Kwolek, for its great advantages in the process of forming high performance fibers and films, especially the convenience in the tropism of the main chain. Some polyamides with varied structures have been reported, which exhibited lyotropic property in 100% sulfuric acid, a highly corrosive solvent and an acid rain generator. However, the lyotropic liquid crystalline property in polar aprotic organic solvents of these aromatic polyamides as well as good organic solubility is more valuable and desirable in respect that it will be constructively helpful to reduce the cost and environmental pollution in the manufacturing process of these polyamides, by wet-spinning or extruding these polyamides or copolyamides from organic solutions and averting the use of sulfuric acid. Unfortunately, few aromatic polyamides can exhibit lyotropic liquid crystalline properties in common organic solvents, due to their limited organic solubility. The too high rigidity and too strong intermolecular hydrogen bonding in these polyamides result in their poor solubility in most organic solvents, restricting their applications. In this thesis, our efforts have been focused on modificating chemical structures of rigid aromatic backbones of polyamides introducing phthalazinone moiety in order to improve their solubility while maintaining the desired properties.In the first part of the paper, the synthesis of l,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl) phenyl)] (2H) phthalazin-1-one (DHPZ-DA) is optimized and characterized by FTIR, NMR, MS, HPLC method. And a series of aromatic copolyamides containing phthalazinone moiety and ether linkages were prepared from DHPZ-DA, p-phenylenediamine (PPD), 4,4'-diaminodiphenylether (DAPE) and terephthaloyl dichloride (TPC) by low temperature solution polycondensation. With a serie of well designed experiments, all the factors which may affect the polycondensation are tested, and the optimized factors are found.The factors researched in the article including reaction temperature, monomer concentration, acid receptor concentration, salt concentration and so on.In our research, we also attempted to prepare organic soluble lyotropic liquid crystalline copolyamides with other desired properties by incorporating the twisted and non-coplanar phthalazinone structure into the rigid main chain of PPTA for the first time. The new copolyamides thus obtained were tested of their capability to form lyotropic solutions by polarizing light microscope (PLM). The influence of the twisted and non-coplanar phthalazinone structure on the close packing of the PPTA main chains was tested by WAXD. And their other properties such as inherent viscosity, solubility, thermal properties, crystallinity of these aromatic copolyamides were also measured. The copolyamides had relatively high inherent viscosities, ranging from 1.86 to 5.30 dL/g. Solubility of these copolyamides was improved in NMP, DMAc, NMP (1 wt % LiCl) and DMAc (1 wt % LiCl) by introducing phthalazinone moiety and ether linkages into the main chain. These copolyamides showed Tg values between 297 and 351 ℃. And they had good thermal stability, associated with 5% and 10% weight loss temperatures in the range of 480-516 ℃ and 501-532 ℃ in nitrogen, respectively. WAXD measures indicated these copolyamides were semicrystalline in nature. Some of these copolyamides exhibited lyotropic liquid crystalline behavior in concentrated H2SO4, NMP (1 wt % LiCl), and even in NMP solutions, as evidenced by polarizing light microscopy.
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