A liquid composition comprising at least one aprotic organic solvent and at least one fluorinated ion exchange polymer which consists of recurring units derived from a chlorofluoroolefin of formula CF2═CCIY, wherein Y is F or CI, and from at least one fluorinated functional monomer selected among those of formula CF2═CF—O—(CF2CF(CF3)O)m—(CF2)nSO2X, wherein m is an integer equal to 0 or 1, n is an integer from 0 to 10 and X is chosen among halogens (CI, F, Br, I), —O−M+, wherein M+ is a cation selected among H+, NH4+, K+, Li+, Na+, or mixtures thereof is disclosed. The liquid composition is suitable for the preparation of ion exchange membranes, in particular composite membranes, for use in fuel cell applications.