The present invention is a fluoropolymer comprising a plurality of pendent groups terminating in --CF.sub.2SO.sub.3X, --CF.sub.2SO.sub.2F, or combinations thereof, where X is selected from a group consisting of H.sup.+ and a monovalent cation, and at least one --CF.sub.2Y end group, where Y is selected from a group consisting of a chlorine atom, a bromine atom, an iodine atom, a nitrile group, and an --SO.sub.3X group.