TECHNOLOGY FOCUS - POLYMERS - Preferred Materials: The crosslinked polymeric composition may have hydrophilic functional groups having a crosslinking moiety including at least one group selected from sulfonyl methide, sulfonyl methane, amide, sulfonamide, imide and sulfonimide groups. The crosslinked fluorocarbon polymeric composition has hydrophilic functional groups of the formula(II):covalently bonded through the Rf groups each to a CY group of a fluorocarbon polymeric composition of formula (III):A = polymeric group derived from at least one fluorine-containing polymerizable monomer;n = integer of 0, 1 or greater than 1;m = integer of at least 1;Y = hydrogen or halogen wherein at least one Y is a fluorine;T = carbonyl or sulfonyl group;Rf = 1-20 C linear, cyclic or branched fluoroalkyl group optionally containing one or more oxygen, nitrogen, chlorine, phosphorus, hydrogen and/or sulfur atoms and/or one or more sulfonyl or carbonyl groups, or a sulfonyl or carbonyl-containing fluoropolymeric group;Z+ = a proton or an organic or an inorganic cation;t = 0 or 1;L = C, CH or N;E' = TRfT- or -Rf'-;G = R'fT- or R;R'f = 1-20 C linear, cyclic or branched fluoroalkyl radical optionally containing one or more chlorine, phosphorus, and/or hydrogen atoms and/or one or more sulfonyl or carbonyl groups, or a sulfonyl or carbonyl containing fluoropolymeric group optionally connected to another chain of the fluorocarbon polymeric composition having hydrophilic functional groups;R = hydrogen or a substituted or unsubstituted alkyl or aryl group.A crosslinked perfluorocarbon polymeric composition having hydrophilic functional groups of formula (IV):covalently bonded through the Rf groups each to a CY group of a fluorocarbon polymeric composition of formula (III),Rf and Rf' = same or different and can be 1-20 C linear, cyclic or branched fluoroalkyl group optionally containing one or more oxygen, nitrogen, chlorine, phosphorus, hydrogen and/or sulfur atoms and/or one or more sulfonyl or carbonyl groups or a sulfonyl or carbonyl-containing fluoropolymeric group, optionally connected to another chain of the fluorocarbon polymeric composition having hydrophilic functional groups;Z+ = proton of an organic or an inorganic cation;t = 0 or 1 EXAMPLE - A piece of commercially available Nafion NE-105F film made from a perfluoroionomer in the sulfonyl fluoride form having an equivalent weight of 980 was placed in a small stainless pressure vessel. The vessel was evacuated to a pressure no greater than 100mTorr for at least 5 minutes. Gaseous anhydrous ammonia was then introduced into the vessel until the pressure in the vessel reached 60 psi. The film remained in contact with anhydrous ammonia for 30 hours at 60 degreesC. The vessel was allowed to equilibrate to room temperature, vented and purged with argon for five minutes. The film was removed from the vessel, rinsed in water and exposed to nitric acid to convert the membrane into the free sulfonamide form. The membrane was further rinsed with water and dried at room temperature. The film appeared stronger and stiffer than the starting film. Attenuated total reflectance of the film revealed the presence of sulfonamide groups. No significant amounts of sulfonyl fluoride groups remain on the film indicating complete conversion to the sulfonamide form.