A novel diamine monomer, 2,4-diamino-4'-carboxy diphenyl ether had been synthesized. Several polyimides were prepared by reacting this diamine with commercially available dianhydrides, such as benzophenone tetracarboxylic acid dianhydride (BTDA), 4,4'bis{hexafluoroisopropylidene his (phthalic anhydride)} (6-FDA), oxydiphthalic anhydride (ODPA) and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA). Furthermore, copolymers from the resulting diamine and oxydianiline (ODA) with 6 FDA were also synthesized. The inherent viscosities of the polymers were 0.42-0.67 dl g(-1). The polymers have good solubility in polar aprotic solvents, high thermal stability up to 410 ° C in nitrogen and high glass transition temperatures (T-g) ranging from 260-330 ° C. These polymers formed tough flexible films by solution casting. © 2005 Elsevier Ltd. All rights reserved.