TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The mixing rate of the electrolyte polymer formed by co-polymerizing monomer (a) having acidic group or quaternary ammoniated monomer having acidic group, and monomer (b) having base group, and polyimide is 10/90-80/20. The polyimide has hydroxyl group and/or carboxyl group. Preferred Method: The solid polymer is obtained by further adding a neutral monomer to the monomer (a) and monomer (b) which has a basic group followed by copolymerizing the resulting monomer mixture. The polyimide is obtained by polycondensing tetracarboxylic acid dianhydride(s) and tetracarboxylic acid, and diamine compound(s), in a solvent. Preferred Monomer: The quaternary ammoniated monomer having acidic group is quaternary ammonium salt of an acrylamide methyl propane sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, (meth)allyl sulfonic acid, (meth)acrylic acid, maleic acid anhydride, fumaric acid or these monomers. The monomer which has basic group (b) is acrylamide, allylamine, vinyl pyrrolidone, vinyl imidazole, amino acrylamide, amino sulfone, vinylpyridine, dimethyl amino-ethyl (meth)acrylate, vinyl caprolactam, vinylcarbazole, vinyl di amino triazine or ethylenimine. The neutral monomer is 2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, styrene, acrylonitrile, polyethylene glycol-di (meth)acrylate. The tetracarboxylic acid dianhydride is chosen from 1,2,4,5-cyclohexane tetracarboxylic acid dianhydride, 1,2,3,4-cyclobutane tetracarboxylic acid dianhydride, 1,2,4,5-cyclopentane tetracarboxylic acid dianhydride and bicyclo (2.2.2) oct-7-en-2,3,5,6-tetracarboxylic acid dianhydride. The tetracarboxylic acid is chosen from 1,2,4,5-cyclohexane tetracarboxylic acid, 1,2,3,4,-cyclobutane tetracarboxylic acid, 1,2,4,5-cyclopentane tetracarboxylic acid, bicyclo(2.2.2) oct-7-en-2,3,5,6-tetracarboxylic acid. The diamine compound is chosen from 2,2'-dihydroxy-4,4'-diamino diphenylene, methylene bis(4-amino-2-benzoic-acid), 4,4'-diamino diphenylether, 2,2-bis(4-(4-amino phenoxy)phenyl) propane, 1,4-bis(4-amino phenoxy)benzene and 4,4'-diamino di-cyclohexyl methane. EXAMPLE - Polymer (A) was prepared using dimethyl sulfoxide, 2-acryl amide-2-methyl propane sulfonic acid, acryl amide and azobisisobutyronitrile. Polyimide (1,2,4,5-cyclohexane tetracarboxylic acid dianhydride, methylene bis(4-amino-2-benzoic acid) and methylene bis (4-amino-2-benzoic acid)) (in g) (4), polymer (A) (4) and dimethyl sulfoxide (8) were added, stirred and set as homogenous solution. The mixed solution was applied on upper surface of glass plate applied with external mold release agent, and temperature was raised from 70degreesC to 120degreesC for 6 hours, and electrolyte film with thickness of 27 microns was obtained. The obtained film had ionic conductivity of 1.4x10-2 S/cm, methanol transmission rate of 4.5 mg/cm2/minute and methanol permeability of 12 micrograms/cm.minute.