This invention relates to fluoropolymer fibers and films which can be modified by cationic agents, such as cationic dyes. The fiber or film comprises a blend of a first and a second copolymer, or it comprises a terpolymer, the blend or terpolymer having (1) an acid or ionic functionality provided by a pendant group represented by the formula —(O—CF2CFR)aO—CF2CFR′SO3−Z+, wherein R and R′ are independently selected from F, Cl or a perfluorinated alkyl group having 1 to 10 carbon atoms, a=0, 1 or 2, and Z+ is H+, an alkali metal cation, or a cation derived from a compound selected from the group consisting of a cationic dye, a cationic whitener, a cationic flame retardant, a cationic antistatic agent, and mixtures thereof, and (2) a larger amount of a fluoroalkylvinylether, a fluoroalkene, or ethylene functionality. Such fibers and films are useful in various consumer goods where the product is desirably colored, whitened, antistatic, or flame retardant.