A series of aromatic copolyamides containing phthalazinone moiety and ether linkages were prepared from 1,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)](2H)phthala zin-1-one (DHPZ-DA), p-phenylenediamine (PPD), 4,4'-diaminodiphenylether (DAPE) and terephthaloyl dichloride (TPC) by low temperature solution polycondensation. The copolyamides had relatively high inherent viscosities, ranging from 1.86 to 5.30 dl/g. The copolyamides showed T, values between 297 and 351 C. 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. And they had good thermal stability, associated with 5 and 10% weight loss temperatures in the range of 480-516 and 501532 C in nitrogen, respectively. WARD 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. (c) 2005 Elsevier Ltd. All rights reserved.