TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The process involves initial step of dehydrofluorinating a starting fluoropolymer using dehydrofluorinating agent to form an unsaturated fluoropolymer. Then, the acidifiable functionalizing agent preferably nucleophilic agent is added to the unsaturated fluoropolymer and the functionalizing agent is then acidified. The process further involves a cationic exchange process which yield acid functional fluoropolymer such as lithium anion salt. The acid functional fluoropolymer may be cross-linked.Preferred Properties: The acid functional fluoropolymer has an equivalent weight of 3000 g/mol or less preferably 1600 g/mol or less. The ionic conductivity (H+) of acid functional fluoropolymer is 0.01 mS/cm or more preferably 0.05 mS/cm or more at 25degreesC.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The starting fluoropolymer is a polymer or copolymer of vinylidene fluoride (1,1-difluoro ethene).The acidifiable nucleophilic functionalizing agent comprises a group selected from anionic nitrogen, oxygen and sulfur containing groups.The acidifiable functionalizing agent preferably has general formula -X-Ar. Most preferably, the agent is an aryl oxide (ArO-), phenoxide (O-) or sulfonyl halide.The acid functional fluoropolymer having pendent groups of formula -X-Ar-An preferably has groups,X = O;A = SO3M;M = H+ or metal anion; andAr = phenyl EXAMPLE - Fluoropolymer resin Fluorel FC2145 at weight ratio of 68.7 was blended with 20% of Fluorel FC2178. 1 M phenoxide solution of weight ratio 31.3 was dissolved in tetrahydrofuran and added to fluoropolymer mixture. 10% of bisphenol AF and two equivalence of lithium carbonate was added and the solution was refluxed and left out at room temperature over night. The resulting brown solution was decanted, solvent was removed under an aspirator and then under a vacuum pump to obtain acid functional resin. The equivalent weight of the resin was 1070 g/mol. The resin was pressed into films which were then sulfonated to form membrane. The ionic conductivity of the membrane was measured and was found to be 65 mS/cm at 25degreesC and 94 mS/cm at 82degreesC.