TECHNOLOGY FOCUS - POLYMERS - Preferred Units: The polyarylene consists of structural units of formulae (A,B).Y=bivalent electron-attractive group;Z=bivalent electron-donating group or bivalent direct bond;Ar=aromatic group having a substituent of formula: -SO3H;m,n=0-10;k=1-4;R1-R8=H, fluorine, alkyl, fluorine substituted alkyl, allyl, aryl, or cyano;W=bivalent electron-attractive group or bivalent single bond;T=single bond or divalent organic group;andp=0 or more.Preferred Properties: The sulfonic acid group and the functional group which can be interacted are basic functional groups which contain a nitrogen atom. The polymer having sulfonic acid group and functional group, has a weight average molecular weight of 500 or more. EXAMPLE - 4-(4-(2,5-dichloro benzoyl) phenoxy) neopentyl benzene sulfonate (in g) (39.58), an oligomer (15.23) having a weight average molecular weight of 11200, a glass transition temperature of 110degreesC, and a thermal decomposition temperature of 498degreesC, nickel chloride bis (triphenylphosphine) (1.67), triphenylphosphine (10.49), sodium iodide (0.45), zinc dust (15.69), and dry N-methyl-2-pyrrolidone (390 mL) were heated under nitrogen at 75degreesC, while stirring. The polymerization reaction liquid was diluted with tetrahydrofuran (250 mL), stirred for 30 minutes, and filtered. Large excess of methanol (1500 mL) was poured, and the filtrate was solidified. The solidified substance was filtered, air-dried, dissolved in tetrahydrofuran/N-methyl-2-pyrrolidone (200/300 mL), and solidified. A copolymer (47) (99% yield) consisting of a sulfonic-acid derivative protected by the neopentyl group was obtained after air-drying. The number average molecular weight was 47600, and the weight average molecular weight was 159000. The obtained copolymer (5.1) was dissolved in N-methyl-2-pyrrolidone (60 mL), and heated at 90degreesC. A mixture of methanol (50 mL) and concentrated hydrochloric acid (8 mL) was added to the reaction system, and reacted for 10 hours. Excess methanol was distilled, and a light green transparent solution was obtained. The polymer was washed with ion-exchange water. The obtained polyarylene copolymer had a number average molecular weight of 53200, a weight average molecular weight of 185000, and a sulfonic-acid equivalent of 1.9 meq/g. A film was cast using a solution obtained by dissolving the copolymer (10) in polyvinyl pyrrolidone (5) and N-methyl pyrrolidone (100 mL). The film had a proton conductivity of 0.29 S/cm, a dimensional-change rate of 104%, and a methanol permeability of 195 g/hour/m2.