A polyvinylidene difluoride copolymer with a fluoroolefin selected from 2,3,3,3-tetrafluoropropene, 1,1,3,3,3-pentafluoropropene, 2-chloro-pentafluoropropene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, 3,3,3-trifluoro-2-trifluoromethylpropene and a mixture thereof, wherein the stoichiometry of the co-monomers defines the barrier properties of the copolymer. Such polymers include moisture barrier copolymers and oxygen barrier copolymer. Processes for preparing such moisture barrier copolymers and oxygen barrier copolymers are also provided.