Abstract: The present invention relates to proton-conducting polymer membranes which comprise polyazoles containing sulfonic acid groups and is obtainable by a process comprising the steps A) mixing of one or more aromatic and/or heteroaromatic tetraamino compounds with one or more aromatic and/or heteroaromatic carboxylic acids or derivatives thereof which contain at least two acid groups per carboxylic acid monomer, with at least part of the tetraamino compounds and/or the carboxylic acids comprising at least one sulfonic acid group, or mixing of one or more aromatic and/or heteroaromatic diaminocarboxylic acids, of which at least part comprises sulfonic acid groups, in polyphosphoric acid to form a solution and/or dispersion, B) heating of the solution and/or dispersion obtainable according to step A) under inert gas to temperatures of up to 350° C.