TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: The polymer compound having acidic ionic conductive component is a block copolymer that consists of segment containing ionic conductivity and segment that does not contain ionic conductivity. The block copolymer is preferably polyarylene having sulfonic acid group and having repeating units of formulae (A,B).A=bivalent electron-attractive group;B=bivalent electron-donor group or bivalent direct bond;Ar=aromatic group having -SO3H group;m,n=0-10;k=1-4;R1-R8=hydrogen, 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 positive integer.Preferred Process: The irradiation amount of electron beam to the film, is 1-2000 kGy. Preferred Property: The polymer has ion exchange capacity of 0.5-3 mEq/g. EXAMPLE - Polymer (in g) (17.6) of formula (I) having number average molecular weight of 11000, 2,5-dichloro-4'-(4-phenoxy)phenoxy benzophenone (25.4), bis (triphenylphosphine) nickel dichloride (1.18), sodium iodide (1.17), triphenylphosphine (6.3) and zinc dust (9.41) were added to flask that was substituted with dry nitrogen. Subsequently, N-methyl-2-pyrrolidone (NMP) (100 ml) was added to flask, and heated at 80degreesC. Subsequently, the resulting solution was polymerized for 4 hours, and obtained polymer solution was diluted by NMP. The obtained solution was filtered, and the filtrate was supplied into large amount of methanol. The obtained solid substance was filtered, dried and re-precipitated in methanol. The obtained solid substance was removed by filtration and dried, to obtain copolymer (35.7) having weight average molecular weight of 155100. The obtained copolymer (16) was mixed with 98% sulfuric acid (160 ml) in a flask, and maintained at 25degreesC for 24 hours in presence of nitrogen. The resulting solution was poured into ion exchange water, and obtained polymer was removed, washed with water and dried, to obtain sulfonic-acid-group-containing polymer (18) having weight average molecular weight of 161700 and number average molecular weight of 40200. Uniform polymer solution containing sulfonic-acid-group-containing polymer, methanol, and NMP was prepared. The obtained solution was cast on polyethylene terephthalate film, and dried at 80degreesC for 30 minutes and at 150degreesC for 60 minutes, to obtain uniform and transparent solid-electrolyte film of 90 microns thickness. The obtained film was further irradiated with electron beam (500 kGy irradiation amount) at acceleration voltage of 4 MeV. The film had methanol flux of 80 g/h/m2, conductivity of 0.103 S/cm (at 60degreesC and 80% relative humidity) and 0.051 S/cm (at 25degreesC and 80% relative humidity), and favorable dimensional stability.