TECHNOLOGY FOCUS - POLYMERS - Preferred Properties: The oxygen gas permeability coefficient of the ion-exchange membrane, is 0.1 x 10-12 - 3 x 10-12 mol/cm/seconds.The transfer coefficient of water molecule of ion-exchange membrane by electro-endosmosis, is less than 2.5.Preferred Composition: The sulfonic acid group content of ion-exchange membrane, is 0.3-3.5 meq/g. The ion-exchange membrane contains 50-100 mass% of polyarylene ether group compounds. The surface of ion-exchange membrane is coated with fluorine group ion-exchange resin layer of 0.5-50 microns thickness.The ion-exchange membrane further contains an antioxidant.The polyarylene ether group compound preferably contains structural units of formulae (4) or (5).X = same as define above. EXAMPLE - 3,3'-Di-sulfo-4,4'-dichlorodiphenyl sulfone disodium salt (in g) (5.2335), 2,6-dichlorobenzonitrile (2.3323), 4,4'-biphenol (4.5086), potassium carbonate (3.484) and molecular sieve (2.61) were added to 4-neck flask (100 ml). Then, nitrogen and N-methyl pyrrolidinone (NMP) (35 ml) were added, and stirred for 1 hour at 150 degreesC. The temperature was further increased to 200 degreesC, and cooled. The obtained polymer was washed with water, and dried to obtain polymer having logarithmic viscosity of 1.19. The obtained polymer (1) was dissolved in NMP (5 ml), and cast on top of glass plate. Then, NMP was distilled, and the glass plate was immersed in water. The film formed on the glass plate was washed with dilute sulfuric acid, and salt was removed. Finally, the acid component was removed from the film by boiling with pure water for 1 hour, to obtain ion-exchange membrane of 205 microns thickness. The ion-exchange membrane had ionic conductivity of 0.16 S/cm, oxygen gas permeability coefficient of 0.51 x 10-12 mol/cm/seconds, ion-exchange capacity of 2.03, water-molecule transfer coefficient of 1.7 and electric power generation efficiency of 99 %. 3 wt.% reduction temperature of the membrane was 381 degreesC when measured by thermogravimetric analysis. The ion-exchange membrane had favorable durability (fenton-proof test) and dimensional stability.