TECHNOLOGY FOCUS - POLYMERS - Preferred Compounds: The polymer (B) is polynorbornene rubber. The polymer (D) is a ternary polymer of ethylene, propylene and diene monomer. The polymer (C) contains a polymerizable monomer such as vinyl sulfonic acid having sulfonic acid group cross-linked by a cross-linking agent. EXAMPLE - Polymer composition (15 wt.pts) containing Norsorex NB (RTM: powder of ring-opened polymer of norbornene) (in wt.%) (20), EPDM553 (RTM: ethylene-propylene-diene monomer rubber) (10) having weight average molecular weight of 1000000 and ultra high molecular weight polyethylene (70) having weight average molecular weight of 1500000, and liquid paraffin (85 wt.pts) were mixed and melt-kneaded at 160degreesC for 60 minutes. The resulting mixture was cooled to form a sheet-like product. The obtained sheet was heat-pressed and biaxially stretched along the height and width direction at 115degreesC. Then, solvent was removed using heptane and microporous film was obtained. The microporous film was heat-processed in air at 85degreesC for 6 hours and at 116degreesC for 2 hours, to obtain a porous base-material having thickness of 20microns and porosity of 40%. The porous base-material was impregnated into 0.5 wt.% sodium dodecylbenzenesulfonate aqueous solution and ultrasonification and evacuation were carried out such that base-material was hydrophilized. Sodium dodecylbenzene sulfonate aqueous solution was mixed with vinyl sulfonic acid (70) having purity of 98%, vinyl pyrrolidone, and N,N- methylene-bis acrylamide (10). V-50 (RTM: water-soluble azo initiator) (1 mol%) was further added, to obtain an electrolyte monomer solution. Deaeration of resulting solution was carried out at 20degreesC or less under reduced pressure condition. The film base-material was further immersed in the resulting solution, and subjected to deaeration and heating such that electrolyte monomer was polymerized. The obtained electrolyte film was immersed in 1N hydrochloric acid aqueous solution. Ion exchange was carried out for 2 minutes, excess hydrochloric acid was removed and vacuum-dried at 50degreesC for 5 hours, to obtain proton exchange film having thickness of 29 microns and weight increase rate of 120%. The obtained film had proton conductivity of 0.17 S/cm and methanol permeation rate of 4.3 mol/cm2/hr. The film was hardly peeled from the electrode even when methanol was used as fuel.