NOVELTY - A functional fluorine-containing polymer composition comprises a polymer having amorphous and crystalline segments; and alkali metal sulfonate, ammonium sulfonate, sulfonic acid, sulfonyl methide (both acid and salt), or their derivatives. The mpt. of polymer lies above that of a fully random copolymer of its monomers; and lies at most 5 degrees C below that of poly(vinylidene fluoride).    USE - The invention is for electrochemical applications, e.g. fuel cells (claimed), batteries, exchange membranes, and sensors. The ionically conductive compositions are preferably useful in a binder polymer for lithium ion battery electrodes or polymer gel electrolyte for lithium ion battery separator. The ionomers and ionically conductive compositions may be employed as direct substitutes for the ionomers disclosed in Doyle et al, op.cit., and Feiring et al, op.cit..    ADVANTAGE - The graft copolymer of the invention exhibits a lower tensile modulus and a higher elongation to break, which is greater ductility and toughness, than are exhibited by a polymeric composition identical compositionally in every respect to the graft copolymer but prepared from separately polymerize crystalline and amorphous polymer components. The crystalline polymer exhibits a heat of fusion of at least 1, preferably at least 5, J/g with mpt of at least 35 degrees C. The amorphous polymer does not exhibit a heat of fusion of at least 1, preferably less than 0.5, J/g with a mpt of at least 35, preferably 100 degrees C. This polymer does not have a glass transition temperature of above 35, preferably not above 10 degrees C.    DETAILED DESCRIPTION - A functional fluorine-containing polymer composition comprises a polymer of formula ((CF2CH2)u(CF2-CF-O-Rf-SO2F)v)a((CF2CH2)x(CF2-CF-O-Rf-SO2F)y)b where the section in the first square bracket is amorphous and the section in the second is crystalline and;    Rf = perfluoroalkenyl ether diradical    and additives of alkali metal sulfonate, ammonium sulfonate, sulfonic acid, sulfonyl methide (both acid and salt), or their derivatives. The ratio of u:v is 85:15-50:50 and that of x:y is 100:0-87:13. (I) is a copolymer of monomers of formulae CF2=CH2 (IIa) and CF2=CF-O-Rf-SO2F (IIb). Its mpt lies above that of a fully random copolymer of monomers (IIa) and (IIb) of the same overall composition; and lies at most 5 degrees C below that of poly(vinylidene fluoride).    INDEPENDENT CLAIMS are included for the following:    (a) An electrochemical cell comprising an anode, a cathode, and a separator, each containing an ionomer of the polymer;    (b) A process for forming a graft copolymer of (I) comprising combining (IIb) at 0.2-.6 g/ml with water and fluorosurfactant, and agitating the combination to form an emulsion having a droplet size of not more than 0.5 mum; in a reaction vessel, combining in water the emulsion with (IIa) at a first monomer concentration ratio and a free radical concentration; allowing the monomers to polymerize to form a first copolymer that may be amorphous or crystalline; in a reaction vessel, combining in water the first copolymer with an additional amount of the emulsion of (IIb) and additional amount of (IIa), at a second monomer concentration ratio, and an additional amount of free radical initiator; and allowing the further amounts of monomer to polymerize to form a second copolymer that is crystalline if the first copolymer is amorphous and the second copolymer being amorphous if the first copolymer is crystalline.