Abstract: The invention concerns fluoropolymers comprising at least one repeat unit of formula (I): wherein: groups X and Y, identical or different, represent H or F; group Z represents F or a perfluorinated alkyl group; group W represents CH2O or CF2O or CO2; group Ar represents a divalent group including at least one optionally substituted carbon-containing aromatic cycle; group Q represents a single bond, (CF2)n with 1?n?10, or C2F4OC2F4; group G represents a cation exchanging group, preferably selected among: SO2R1, with R1 representing OH, F or Cl; or P(?O) (OR2)2 with R2 representing H or an optionally substituted alkyl group; or CO2H and having ion exchange capacity not less than 0.5 meq/g polymer. The method of synthesis, the membranes obtained using these polymers and the fuel cell systems containing such membranes are also part of the invention.