Abstract: A copolymer containing, in addition to recurring elements of a sulfonated poly(arylene) containing exclusively recurring structural element(s) of the general formulas —[—Ar1(SO3M)n-X—]— and —[—Ar2(SO3M)n-Y—]—, wherein X and Y, which are identical or different from each other, each represent an electron-acceptor group, Ar1 and Ar2, which are either identical or different from each other, represent an aromatic or heteroaromatic ring system with 5-18 ring atoms; wherein the aromatic or heteroaromatic ring system, in addition to the SO3M and the substituents X and Y, optionally comprises additional substituents which are not electron-donor groups; M represents monovalent cation and n is an integral number between 1 and 4; and wherein X, Y, Ar1, Ar2, M and n can be identical or different in various structural elements, independently of each other, one or several additional elements of at least one additional monomer or macromonomer.