Preparation and Characterization of Lyotropic Liquid Crystalline Aromatic Copolyamides Containing Twisty and Non-coplanar Moiety

Abstract

A series of aromatic rigid-chain copolyamides were prepared from 1,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)](2H)phthalazin-1-one (DHPZ-DA), p-phenylenediamine (PPD), 1,4-bis(4-aminophenoxy)benzene (BAPOB) and terephthaloyl dichloride (TPC) by low temperature solution polycondensation. The polymers were produced with high yields and relatively high inherent viscosities, ranging from 1.74 to 4.31 dL/g. The introducing of phthalazinone moiety and ether linkages into the main chain improved the solubility in some polar solvents. The Tg values of the polymers were in the range of 291–351 °C and the 5 and 10% weight loss temperatures in nitrogen were in the range of 486–518 and 509–538 °C, respectively, indicating their good thermal stability. WAXD measures indicated that these copolyamides were semicrystalline in nature. Most of the polymers exhibited nematic lyotropic liquid crystalline characteristics in concentrated H2SO4, NMP (1 wt % LiCl) and DMAc (1 wt % LiCl) solutions, as evidenced by polarizing light microscopy.