A new series of sulfonated polyimide (SPI) copolymers containing NH, OH, or COOH groups were synthesized by the polycondensation of 1,4,5,8-naphthalnetetracarboxylic dianhydride, 3,3'-bis(sulfopropoxy)-4,4'-diaminobiphenyl, and 3-(4-aminophenyl)-5-(3-aminophenyl)-1H-1,2,4-triazole (SPI-8-m), 3,5-bis(4-aminophenyl)-1H-1,2,4-triazole (SPI-8-p), 3,6-diaminocarbazole (SPI-9), 3,5-diamino-1H-1,2,4-triazole (SPI-10), bis(3-aminopropyl)-amine (SPI-11), 2,6-diaminopurine (SPI-12), 2,4-diamino-6-hydroxyprymidine (SPI-13), or 3,5-bis(4-aminophenoxy)benzoic acid (SPI-14). The obtained SPIs were soluble in polar organic solvents and gave tough and flexible membranes by solution casting. The SPI membranes having NH and COOH groups showed high thermal (decomposition temperature approximate to 1200 degrees C) and mechanical (maximum stress >22 MPa) stability. Introducing NH groups, especially triazole and carbazole groups, was effective in improving proton conductive properties of SPI membranes at low humidity. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2846 2854, 2010