TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Material: The polyelectrolyte material has principal chain having a portion having a carbon type structure and a graft side chain portion having structure of formula -(CH2CHCO((A3-B-A4-CO-A2-CO)n-A3-B-A4-SO3H))m grafted by the principal chain.A2-A4,A',B,m=same as defined above;andn=1 or more, preferably 1.The principal chain portion is a fluorinated polyolefin whose at least one portion of polyolefin or hydrogen is substituted with fluorine atom. The principal chain portion is a copolymer of CH2CHR (where R is hydrogen or 1-3C alkyl group) and CF2CFR (where R is fluorine or 1-3C perfluoro-alkyl group). The polyelectrolyte material is obtained by grafting a monomer consisting of styrene or a monomer consisting of acrylic acid, to a polymeric material having a carbon type structure. An acyl-halide compound of formula XCO-A2-COX and an aromatic compound of formula H-A3-B-A4-H are reacted with 1 unit or more of the obtained grafted polymer, in the presence of a Lewis acid. A phenyl group and/or a sulfo group, is introduced to a portion of polymeric material, to obtain the polyelectrolyte material.A2-A4,B,n,m=same as defined above;andX=halogen.The mass ratio of grafted monomer in the polymeric material having a carbon structure, is 0.2 or more. Preferred Definitions:    A2-A4,A'=p-phenylene;and    B=-O-.    EXAMPLE - An ethylene-tetrafluoroethylene copolymer film was washed with acetone, irradiated with gamma-rays, and introduced into a reaction tube. A styrene monomer (in g) (70) was added into the reaction tube substituted with nitrogen. The reaction tube was maintained at 70degreesC for 2 hours. The film was washed with methanol and dried, such that the mass ratio of styrene with respect to the film was 0.33. The styrene grafted film, was immersed in nitrobenzene (100 mL) in which terephthaloyl dichloride (2) and aluminum chloride (1.3) were dissolved. Reaction was performed at 130degreesC for 3 hours. The obtained film was removed, washed and immersed in nitrobenzene (100 mL) in which diphenyl ether (1.7) and aluminum chloride (0.65) were dissolved. Reaction was performed at 130degreesC for 3 hours. The obtained film was removed, washed and immersed in dichloroethane (100 mL) containing chlorosulfonic acid (1). Sulfonation was performed for 90 minutes at 60degreesC, to obtain a film consisting of electrolyte composition. The obtained film was effectively used in fuel cells. The obtained film had grafting rate of 33%, saturation moisture content of 28.3%, ion exchange capacity of 1.3 meq/g and oxidation resistance of 97.3%.