Polynorbornene-based ion exchange membranes derived from phosphonated polymer and methods of making same
A proton exchange polymer comprises a polynorbornene copolymer with hydrophobic and hydrophilic blocks that can be phosphonated to produce phosphonic acid functional groups for proton exchange. Also, the polymer may be crosslinked to form quaternary ammonium groups on the side chains. The polynorbornene copolymer may be acid doped to ionically bond phosphonic acids to the quaternary ammonium groups that may for ion pairs for proton exchange. The proton exchange polymer has high temperature stability with the phosphonic acid functional group and can be mechanically durable with cross linking. Proton exchange membranes may utilize the proton exchange membrane in fuel cell and electrolyzer applications.
1. A proton exchange polymer comprising:
a) a backbone comprising polynorbornene;
b) a side chain extending from the backbone; and
c) a functional group coupled to said side chain and comprising phosphonic acid covalently bonded to said side chain.
2. The proton exchange polymer of claim 1 , wherein the functional group further comprises quaternary ammonium.
3. The proton exchange polymer of claim 2 , further comprising ionically bonded phosphonic acid that forms an ion pair with the quaternary ammonium.
4. The proton exchange polymer of claim 3 , further comprising a cross-linker;
wherein the cross-linker is in a concentration of 0.1 mol % to 30 mol %.
5. The proton exchange polymer of claim 4 , wherein the cross-linker is a branched crosslinker.
6. The proton exchange polymer of claim 5 , wherein the branched cross-linker comprises triamine.
7. The proton exchange polymer of claim 4 , wherein the cross-linker includes a diamine compound.
8. The proton exchange polymer of claim 7 , wherein the cross-linker includes tetramethyl hexyldiamine (TMHDA).
9. The proton exchange polymer of claim 1 , further comprising a secondary crosslinking agent that are tertiary diamine head groups which include DABCO (1,4-diazabicyclo[2,2,2]octane) and TMHDA (N,N,N,N-tetramethylhexane diammonium), 1,4-diiodobutane.
10. The proton exchange polymer of claim 1 , wherein the side chain comprises aliphatic hydrocarbon side chains.
11. The proton exchange polymer of claim 10 , wherein the aliphatic hydrocarbon side chains comprise four or more carbons.
12. The proton exchange polymer of claim 1 , wherein the backbone is a co-polymer of hydrophobic blocks and hydrophilic blocks.
13. The proton exchange polymer of claim 12 , wherein the hydrophilic block comprises bromopropyl norbornene.
14. The proton exchange polymer of claim 12 , wherein the hydrophobic block comprises Butyl norbornene.
15. A proton exchange membrane comprising the proton exchange polymer of claim 1 , wherein the proton exchange membrane is a thin sheet of material having a thickness of less than 200 μm.
16. The proton exchange membrane of claim 15 , further comprising a recombination catalyst selected from the group consisting of platinum nanoparticles, platinum nanoparticles supported on carbon, platinum nanoparticles supported on oxides, platinum alloy nanoparticles, platinum alloy nanoparticles supported on carbons, and platinum alloy nanoparticles supported on oxides.
17. The proton exchange membrane of claim 15 , further comprising a radical scavenger that is an antioxidant selected from the group consisting of Cerium (Ce), Manganese (Mn), phenolic compounds, nitrogen-containing heterocyclic compounds, quinones, amine, phosphites, phosphonites, and thioesters.
18. The proton exchange membrane of claim 15 , further comprising a free radical inhibitor selected from the group consisting of inorganic free radical scavenger such as metal organic frameworks (MOF) including cerium oxides and metal oxide.
19. The proton exchange membrane of claim 15 , further comprising a plasticizer selected from the group consisting of nylon 6,6, Glycerol, ionic liquids.
20. The proton exchange membrane of claim 15 , further comprising a filler selected from the group consisting of oxides of aluminum, silicon, titanium, zirconium and zirconium phosphate, cesium phosphate, zeolites, clays and carbon black, multiwall carbon nanotubes, reduced graphene oxide.
21. The proton exchange membrane of claim 15 , further comprising:
a) a support layer;
wherein the proton exchange polymer extends through the support layer from a first side to a second side of the support layer to produce a composite proton exchange membrane.
22. The proton exchange membrane of claim 21 , wherein the support layer has pores and wherein the proton exchange polymer extends on a first side of said support layer.
23. A proton exchange system comprising:
a) a proton exchange membrane comprising the proton exchange polymer claim 1 ;
b) an anode; and
c) a cathode;
wherein protons are conducted through the proton exchange membrane.
24. The proton exchange system of claim 23 , wherein the proton exchange membrane is heated to a temperature of 130° C. or more.
25. A method of making the proton exchange polymer of claim 1 , comprising:
a) providing said polynorbornene co-polymer comprising a backbone and side chains; and
b) phosphonating the polynorbornene co-polymer to produce a phosphonated norbornene co-polymer comprising phosphonic acid groups covalently bonded to said side chains.
26. The method of claim 25 , further comprising crosslinking the polynorbornene co-polymer with a crosslinker, prior to phosphonating.