Stable trifluorostyrene containing compounds grafted to base polymers, and their use as polymer electrolyte membranes
A fluorinated ion exchange polymer prepared by grafting at least one grafting monomer on to at least one base polymer, wherein the grafting monomer comprises structure 1a or 1b: wherein Z comprises S, SO 2 , or POR wherein R comprises a linear or branched perfluoroalkyl group of 1 to 14 carbon atoms optionally containing oxygen or chlorine, an alkyl group of 1 to 8 carbon atoms, an aryl group of 6 to 12 carbon atoms or a substituted aryl group of 6 to 12 carbon atoms; RF comprises a linear or branched perfluoroalkene group of 1 to 20 carbon atoms, optionally containing oxygen or chlorine; Q is chosen from F, —OM, NH 2 , —N(M)SO 2 R 2 F , and C(M)(SO 2 R 2 F ) 2 , wherein M comprises H, an alkali cation, or ammonium; R 2 F groups comprises alkyl of 1 to 14 carbon atoms which may optionally include ether oxygens or aryl of 6 to 12 carbon atoms where the alkyl or aryl groups may be perfluorinated or partially fluorinated; and n is 1 or 2 for 1a, and n is 1, 2, or 3 for 1b. These ion exchange polymers are useful in preparing catalyst coated membranes and membrane electrode assemblies used in fuel cells.
1. A fluorinated ion exchange polymer prepared by grafting at least one grafting monomer on to at least one base polymer, wherein the grafting monomer comprises structure 1a or 1b:
wherein Z is chosen from S, SO 2 , or POR wherein R comprises a linear or branched perfluoroalkyl group of 1 to 14 carbon atoms optionally containing oxygen or chlorine, an alkyl group of 1 to 8 carbon atoms, an aryl group of 6 to 12 carbon atoms or a substituted aryl group of 6 to 12 carbon atoms;
R F is chosen from a linear or branched perfluoroalkene group of 1 to 20 carbon atoms, optionally containing oxygen or chlorine;
Q is chosen from F, —OM, —NH 2 , —N(M)SO 2 R 2 F , and —C(M)(SO 2 R 2 F ) 2 , wherein M comprises H, an alkali cation, or ammonium;
R 2 F groups is chosen from alkyl of 1 to 14 carbon atoms which may optionally include ether oxygens or aryl of 6 to 12 carbon atoms where the alkyl or aryl groups may be perfluorinated or partially fluorinated; and
n is 1 or 2 for 1a, and n is 1, 2, or 3 for 1b.
2. The fluorinated ion exchange polymer of claim 1 wherein Q comprises fluorine.
3. The fluorinated ion exchange polymer of claim 1 wherein R F is chosen from (CF 2 ) q wherein q=1 to 16, (CF 2 ) q OCF 2 CF 2 wherein q=1 to 12, and (CF 2 CF(CF 3 )O) q CF 2 CF 2 wherein q=1 to 6, and R 2 F is chosen from methyl, ethyl, propyl, butyl, and phenyl, each of which may be partially fluorinated or perfluorinated.
4. The fluorinated ion exchange polymer of claim 3 wherein R F is chosen from (CF 2 ) q wherein q=1 to 4; (CF 2 ) q OCF 2 CF 2 wherein q=1 to 4; and (CF 2 CF(CF 3 )O) q CF 2 CF 2 wherein q=1 to 2 and R 2 F is chosen from perfluoromethyl, perfluoroethyl, and perfluorophenyl.
5. The fluorinated ion exchange polymer of claim 3 wherein n=1 and Z is S or SO 2 .
6. The fluorinated ion exchange polymer of claim 1 wherein the at least one grafting monomer further comprises at least one co-monomer chosen from compounds containing single or multiple vinyl groups; at least one monomer having the structure 2 or 3; and mixtures thereof:
wherein Y comprises H; halogen such as CI, Br, F or I; linear or branched alkyl or perfluoroalkyl groups, wherein the alkyl group comprises C1 to C10 carbon atoms; or a perfluoroalkyl group containing oxygen, chlorine or bromine, and wherein the alkyl group comprises C1 to C10 carbon atoms.
7. The fluorinated ion exchange polymer of claim 6 wherein the compounds containing single or multiple vinyl groups comprise bis(trifluorovinyl)-benzenes of structure 2 or triallyl cyanurate.
8. The fluorinated ion exchange polymer of claim 7 wherein the substituents Y on co-monomer of structure 3 are chosen from hydrogen, chlorine, fluorine, methyl, ethyl, methoxy, perfluoromethyl, perfluoroethyl, perfluorobutyl, perfluoromethoxy, and —CF 2 CF(CF 3 )OCF 2 CF 3 .
9. The fluorinated ion exchange polymer of claim 1 wherein the base polymer comprises at least one homopolymer or copolymer prepared from non-fluorinated, fluorinated, or perfluorinated monomers.
10. The fluorinated ion exchange polymer of claim 9 wherein the base polymer is chosen from poly(ethylene-tetrafluoroethylene), poly(ethylene-chlorotrifluoroethylene), poly(tetrafluoroethylene-hexafluoropropylene), poly(tetrafluoroethylene-perfluoroalkyl vinyl ether), poly(tetrafluoroethylene-perfluoromethyl vinyl ether), poly(tetrafluoroethylene-perfluoropropyl vinyl ether), polytetrafluoroethylene, modified polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), poly(ethylene-tetrafluoroethylene-termonomer), poly(tetrafluoroethylene-perfluorovinylether), polyethylene, and polypropylene.
11. The fluorinated ion exchange polymer of claim 10 wherein the perfluoro(alkyl vinyl ether) comprises a perfluoro(propyl vinyl ether) or perfluoro(ethyl vinyl ether).
12. The fluorinated ion exchange polymer of claim 2 wherein the base polymer is chosen from a terpolymer of ethylene, tetrafluoroethylene (TFE), and 1 to 10 mole % of a termonomer comprising perfluorobutyl ethylene.