TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The total radiation dose for step (c) and (a) is 1 - 10 (preferably 6 - 9) Mrad and 10 - 80 Mrad respectively. The radiation is provided by gamma rays, X rays, ultraviolet radiation, plasma irradiation or beta particles. Step (d) is is carried out at 15 - 70 (preferably 45 - 55)degreesC for 0.5 - 6 (preferably 2 - 3) hours. Step (b) involves heating in an oxygen free atmosphere and adding at least one cross-linking agent. Nitrogen is continuously bubbled through the reaction mixture during step (c). The process additionally involves sulfonating the monomer-grafted cross-linked polymer. The sulfonation is carried out by contacting the monomer-grafted cross-linked polymer with a mixture of methylene chloride and chlorosulfonic acid. Preferred Components: The polymer is an expanded microporous polymer structure and is in the form of thread, non-woven fabric, tube, powder, pellet, sheet or film. The polymer is selected from fluorinated and perfluorinated polymer, copolymer or terpolymer (preferably polyethylene, polytetrafluoroethylene, polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-propylene copolymer, tetrafluoroethylene-ethylene copolymer, hexafluoropropylene-propylene copolymer, hexafluoropropylene-ethylene copolymer, polyvinylidene fluoride, vinylidene fluoride tetrafluoroethylene copolymer, vinylidene fluoride hexafluoropropylene copolymer, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene-hexafluoropropylene copolymer, chlorotrifluoroethylene-ethylene copolymer, chlorotrifluoroethylene-propylene copolymer, perfluoro-alkoxy copolymer, polychloroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or perfluoroalkoxy copolymer).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Emulsion: The emulsion is prepared by heating the emulsifier until it just melt, adding the monomer and adding the water with stirring. The emulsion additionally comprises isopropyl alcohol. The monomer is present in an amount of 25 - 70 (preferably 40 - 60 especially 45 - 55) wt.% and the emulsifier is in 1 - 15 (preferably 5 - 10) wt.% based on the weight of the monomer. Preferred Components: The unsaturated monomer is styrene, trifluorostyrene, alphamethylstyrene, alpha,beta-dimethylstyrene, alpha,beta,beta-trimethylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, divinylbenzene, triallylcyanurate, (meth)acrylic acid, vinylpyrrolidone, vinylpyridine, vinylacetate, trifluorovinylacetate and/or methylvinyltoluene. The emulsifier is alkyl sulfate, alkyl aromatic sulfonate, ethoxylated fatty alcohol and/or fatty acid ester. The cross-linking agent is divinylbenzene or triallyl cyanurate. EXAMPLE - A monomer emulsion was prepared by heating Atlas 3969 (emulsifier) (30.1 g) gently until it just melted. Styrene (301.2 g) was added and mixed thoroughly. De-ionized water (334.7 g) was added with stirring to form the monomer solution. A tetrafluoroethylene-ethylene copolymer(ETFE) film of 50 mum thickness was cut to 7.6 cm x 10.2 cm and sealed in polyethylene bag. It was irradiated to 30 Mrad and quenched at 80degreesC in nitrogen. It was then irradiated to 9 Mrad (3 passes at 3 Mrad per pass, the film was reversed after each pass). The above monomer solution was heated to 60degreesC and sparged with nitrogen for two hours. The film was then immersed in a flat-bottom test tube filled with the emulsion. The reaction was continued at 60degreesC for 4 hours with nitrogen sparging. The film was washed with deionized water and dried. In comparative process the film was immersed in a styrene/toluene (40/60 v/v) mixture instead of the emulsion at 60degreesC and sparged with nitrogen for 2 hours. The reaction time was 17 hours. The comparative film was removed, dried and then heated at 80degreesC for 10 minutes. The percentage graft for the test/comparative film was 108/57. This showed that the distribution of monomer on the test grafted film was very uniform than that of the comparative.