TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: The sulfonated polyarylene is obtained by sulfonating a polymer (P). The polymer (P) is obtained by reacting monomer of formula (A) and monomer(s) of formulae (B-1) to (B-4).R and R' = halogen atom except fluorine atom, or -OSO2Z group;Z = alkyl, fluorine substituted alkyl or aryl group;R1-R8 = H, fluorine atom, alkyl, fluorine substituted alkyl, allyl and/or aryl group;X = bivalent electron-attractive group;Y = bivalent electron-donor group;n = 0 or positive integer;R9-R15 = H, fluorine atom or alkyl;m = 0,1 or 2;W = aryl;R27-R34 = H, fluorine atom, alkyl, fluorine substituted alkyl, aryl or group of formula (D); andR35-R43 = H, halogen atom, alkyl or fluorine substituted alkyl. EXAMPLE - A polyarylene group copolymer was prepared using an oligomer of formula (19) (in g) (25.4), 2,5-dichloro-4'-(4-phenoxy) phenoxy benzophenone (29.6), bis(triphenyl phosphine) nickel dichloride (1.37), sodium iodide (1.36), triphenyl phosphine (7.34), zinc dust (11) and N-methyl-2-pyrrolidone (130 ml). The prepared polyarylene group copolymer had a number average molecular weight and weight average molecular weight of polystyrene conversion of 43000 and 161000, respectively. The obtained copolymer (25) and 96.4% sulfuric acid (750 ml) were mixed under nitrogen stream at 25degreesC for 24 hours. The obtained solution was poured into ion exchange water, and the polymer was made to settle. The obtained polymer was washed repeatedly until the pH of the wash water became 5. The polymer was dried to obtain 96% sulfonic acid group containing polymer (29). The obtained polymer had a number average molecular weight and weight average molecular weight of polystyrene conversion of 67000 and 277000, respectively. The sulfonic acid equivalent weight of the obtained polymer was 1.9 mg/g. An electrolyte film was obtained using the sulfonic acid group containing polymer. The methanol permeability of the obtained film was 1480 g/m2. FORMULA (19), PAGE 26