A metal exchanged fluorinated ionomer is a copolymer minimally including repeating units of (i) a polymerized derivative of a perfluorinated cyclic or cyclizable monomer and (ii) a strong acid highly fluorinated vinylether compound in which the acid moiety is exchanged with a cation of a Group 11 metal. Metal exchanged fluorinated ionomers are readily soluble and can be formed into thin, selectively gas permeable membranes by solution deposition methods. These membranes are suitable for separating olefins from gas olefin/paraffin mixtures. Good selectivity and transmembrane flux can be obtained without humidifying the membrane feed gas mixture.