Disclosed are copolymers formed by copolymerization of: (1) one or more hydrofluoroolefin monomer(s) selected from the group consisting of hydrofluoroethylenes, hydrofluoropropenes, hydrofluorobutenes, hydrofluoropentenes and combinations of these, and preferably selected from 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, with said 1,3,3,3-tetrafluoropropene preferably comprising, consisting essentially of or consisting of trans-1,3,3,3-tetrafluoropropene, and combinations of these, and (2) one or more chlorofluoroethylene monomers, preferably chlorotrifluoroethylene (“CTFE”) monomers, wherein the mole ratio of monomer (1) to monomer (2) is preferably from about 30:1 to about 1:30.