For the first time, a series of high molecular weight (1-4x10(5)g mol(-1)) sulfonated poly(oxadiazole-triazole) copolymers have been synthesized at high temperatures and very short reaction time, by a single-step method based on solution polycondensation reaction of non-sulfonated dicarboxylic acid, hydrazine sulphate and aromatic primary amine (sulfonated and non-sulfonated) in poly(phosphoric acid). By this fast synthetic procedure, copolymers with a high conversion to triazole groups (up to 93%) as well high sulfonation level (IEC= 1.17-1.84mequiv.g(-1)) have been obtained. The structure of the polymers was characterized by elemental analysis and H-1 NMR. Since high sulfonation levels (IEC = 1.17-1.84 mequiv.g(-1)) could be obtained, membranes were prepared from these polymers and have been characterized aiming the application in fuel cells. Proton conductivity up to 6 x 10(-2) S cm(-1) at 150 degrees C was measured. The polymer films had good mechanical properties with storage modulus of about 3 GPa at 300 degrees C. These films exhibited high thermal stability with T-g up to around 440 degrees C. (C) 2008 Elsevier B.V. All rights reserved.