The present invention relates to functionalized polyazoles comprising recurring imidazole units of the general formula ##STR00001## where the radicals Ar, Ar.sup.1 and Ar.sup.2 are tetravalent, divalent or trivalent aromatic or heteroaromatic groups, Y is a bond or a group having from 1 to 20 carbon atoms, v is an integer from 1 to 10 and Z is a group of the general formula ##STR00002## where R.sup.1 and R.sup.2 are each, independently of one another, a hydrogen atom or a group having from 1 to 20 carbon atoms, characterized in that the polyazole is soluble in organic solvents. Furthermore, the present invention relates to intermediates and to a process for preparing the polyazoles. Furthermore, the present invention describes polymer electrolyte membranes and fuel cells in which the polyazoles of the invention are present.