By copolymerization of the disodium-2,2'-disulfonate-4,4'-oxydibenzoic acid (SODBA), the 4,4'-oxybis(benzoic acid) (OBBA) with the bis 3,4-(diaminophenyl)sulfone (BDAPS), a series of high molecular weight sulfonated polybenzimidazoles (sPBI) were prepared by varying the ratio of monomers SODBA/OBBA. Polymers with ion exchange capacity (IEC) ranging from 0 to 3.2 meqH(+)/g were obtained. The chemical structure of the sPBI was confirmed by NMR, Fourier-transform infra-red (FTIR). Although the sPBI display a very poor solubility in organic solvents, they are, in the ammonium salt form, soluble in polar aprotic solvents such as DMF, NMP, or DMSO. Tough and ductile membranes from solution casting method were prepared. The water uptake and the ionic conductivity were determined at 30 and 90 degrees C. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1732-1742, 2010