TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Acid: The super-strong acid group is a fluorine group sulfonate or a fluorine group sulfonamide, such as (-(CF2)n-SO3H), -(CF2)n-SO2-NH-SO2-(CF2)m-CF3, etc.n = 1 or more;m = 0 or more    TECHNOLOGY FOCUS - POLYMERS - Preferred Polymer: The hydrocarbon group polymer is the graft copolymer of polystyrene to a principal chain containing C-F coupling as a side chain. Preferably, the graft copolymer is a polystyrene-graft polytetrafluoroethylene copolymer, polystyrene-graft ethylene tetrafluoroethylene (ETFE) copolymer, polystyrene-graft hexafluoropropylene-tetrafluoroethylene copolymer etc. The monomer having principal chain with C-F coupling as the side chain, is preferably naphthyl or biphenyl groups. EXAMPLE - A base graft film was produced containing a graft polymer with C-F coupling (10), formed by linking a styrene monomer (9), to an ethylene-tetrafluoroethylene (ETFE) copolymer (8) as follows: An ETFE film was put into a thin vinyl bag and sealed in an argon atmosphere, and an electron beam of 5 kGy was irradiated. A styrene monomer and the ETFE film after electron irradiation were inserted into a separating flask. Nitrogen bubbling and deaeration of dissolved oxygen were performed. The material was immersed in a 60degreesC bath. Polystyrene graft chain was introduced after reacting for 10 hours.    The obtained film was washed in chloroform. The non-graft components (unreacted monomer and homo-polystyrene) were extracted and removed. A 50 mm X 50 mm square was formed, of the 17 microns thick ethylene-tetrafluoroethylene copolymer film (ETFE). The base graft film obtained was immersed into a solution of carbon disulfide, chloromethyl methyl ether and zinc chloride at room temperature. After stirring for 72 hours, chloromethyl group was introduced into styrene ring. The film was washed, processed with acetone/water (5:3) mixed solvent containing equivalent sodium sulfonate (Na2SO3). After further processing, fluorine-group sulfonated graft film (11) (thickness 0.023 mm) was synthesized.    The ion exchange capacity, electrical conductivity, membrane practical strength and fuel cell operativity for the film were measured. Ion exchange capacity was 1.2 milli-equivalents/g, electrical conductivity was 0.18 S/cm at 100% relative humidity, and 0.08 S/cm at 50% relative humidity, and membrane strength was good. It was found that when benzene sulfonates were introduced as super-strong acid groups, the electrolyte film had high ion exchange capacity and strength, compared to other sulfonate acid groups.