Incorporation of 0.5 mol % of nitrile and bromine functionalities was found to enhance the radiation crosslinking of the copolymer of tetrafluoroethylene-co-perfluoro(methylvinyl ether) (TFE/PMVE) by a factor of 2 for gamma-irradiations carried out at room temperature to doses in the range 0-50 kGy. The functional groups, nitrile, perfluorophenyl, and hydrogen were found to greatly enhance crosslinking well below the glass transition temperature of TFE/PMVE (276 K). Increased amounts of gel formation as well as improved tensile properties were obtained for irradiations carried out below the T-g of the polymers containing functionalized monomers. These functional groups appear to be acting as catalysts for the radiation crosslinking of TFE/PMVE but they do not get incorporated into the crosslink. (C) 2000 John Wiley & Sons, Inc.