TECHNOLOGY FOCUS - POLYMERS - Preferred Units: The block copolymer contains repeating structural units of formulae (A) and (B).Y'=bivalent electron-attractive group;Z=bivalent electron-donor group or bivalent direct bond;Ar=aromatic group having substituent of formula: -SO3H;m,n=0-10;k=1-4;A, D=direct bond, -CO-, -SO2-, -SO-, -CONH-, -COO-, -(CF2)l-, -(CH2)l, -C(R')2-, -O-, -S-, cyclohexylidene, or fluorenylidene;R'=alkyl, fluorinated alkyl, or aryl;l=1-10;B'=oxygen or sulfur atom;R1-R16=H, fluorine, (halogenated) alkyl, allyl, aryl, nitro, or nitrile;s,t=0-4;andr=0, or 1 or more.The ion-conducting polymer segment has a sulfonic acid group. EXAMPLE - 3-(2,5-dichloro benzoyl) neopentyl benzene sulfonate (in g) (39.58), an oligomer (15.23) having a number average molecular weight of 11200, a glass transition temperature of 110 degrees C, and a thermal decomposition temperature of 498 degrees C, 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 75 degrees C, 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 90 degrees C. 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. The obtained polyarylene (4), 1-methoxy-2-propanol (11.7), toluene (8.8), and gamma -butyrolactone (8.8) were stirred for 24 hours, to obtain a uniform polymer solution having a viscosity of 4500 cp. The solution was cast on a polyethylene-terephthalate film and dried, to obtain a uniform and transparent solid-electrolyte film of thickness 38 microns. The obtained film had a micro phase separation structure with a discontinuous domain consisting of non-ion-conducting polymer segment, and a matrix domain consisting of ion-conducting polymer segment. The film had excellent proton conductivity.