Methods are provided to make acid functional fluoropolymers by: a) dehydrofluorinating a starting fluoropolymer with a dehydrofluorinating agent to form an unsaturated fluoropolymer; b) adding an acidifiable nucleophilic functionalizing agent to a double bond of the unsaturated fluoropolymer; and c) acidifying the added acidifiable function. Acid functional fluoropolymers and ion conducting membranes thereof are also provided, including acid functional fluoropolymer having pendent groups according to the formula: --X--Ar--A.sub.n, wherein X is selected from O, S or NR, where R is selected from H and C1 C30 alkyl or aryl, which are optionally substituted, wherein Ar is a C6 C30 aromatic group, which is optionally substituted, wherein A is an acidic function or salt thereof, wherein a can be independently chosen to be 1, 2 or 3.