Patent ID: 8357725

Claim:
A semi-crystalline fluoropolymer [polymer (F)] having ion exchange groups comprising: recurring units derived from at least one ethylenically unsaturated monomer comprising at least one fluorine atom (fluorinated monomer, hereinafter); and a substantial amount of recurring units derived from at least one ethylenically unsaturated monomer comprising at least one ion exchange group (functional monomer, hereinafter), wherein the amount of unstable end groups of —COF type is of less than 0.05 mmol/kg [polymer (F)], wherein said polymer comprising recurring units derived from at least one fluorinated functional monomer selected from the group consisting of: (M1) sulfonated perfluoroolefin of formula (M1): wherein n is an integer between 0 and 6, and X′ is selected from the group consisting of Cl, F, Br, I, —O − M + , wherein M + cation selected among H + , NH 4 + , K + , Li + , or Na + , and mixtures thereof, (M2) sulfonated perfluorovinylethers of formula (M2); wherein m is an integer between 1 and 10, and X′ is selected from the group consisting of Cl, F, Br, I, —O − M + , wherein M + is a cation selected among H + , NH 4 + , K + , Li + , or Na + , and mixtures thereof; (M3) sulfonated perfluoroalkoxyvinylethers of formula (M3): wherein w is an integer between 0 and 2, RF, and RF 2 , equal to or different from each other and at each occurrence, are independently F, Cl or a C 1-10 perfluoroalkyl group, optionally substituted with one or more ether oxygens, y is an integer between 0 and 6, and X′ is selected from the group consisting of Cl, F, Br, I, —O − M + wherein M + is a cation selected among H + , NH 8 + , K + , Li + , or Na + , and mixtures thereof; (M4) sulfonated aromatic (per)fluoroolefins of formula (M4) Wherein AR is a C 3-15 aromatic or heteroaromatic moiety, and X′ is selected from the group consisting of Cl, F, Br, I, —O − M + is a cation selected among H + , NH 4 + K + , Li + , or Na + , and mixtures thereof; and (M5) mixtures thereof.