Hydrophilic polymers and their use in electrochemical cells
A hydrophilic cross-linked polymer obtainable by copolymerization of hydrophobic and hydrophilic monomers that give a cross-linked hydrophilic polymer on polymerization; a monomer including a strongly ionic group; and water is useful as the membrane in an assembly that can be used in an electrolyter or fuel cell. More generally, a membrane electrode assembly comprises electrodes and an ion-exchange membrane which comprises a hydrophilic polymer including a strongly ionic group. A method for producing a membrane electrode assembly comprising electrodes and an ion-exchange membrane, comprises introducing between the electrodes a material or materials from which the membrane can be formed, and forming the membrane in situ.
1. A membrane electrode assembly comprising electrodes and an ion-exchange membrane which comprises a hydrophilic polymer composition including a strongly ionic group; wherein the polymer is obtainable by a procedure comprising copolymerization, in the presence of water, of hydrophobic and hydrophilic monomers that give a hydrophilic polymer composition on polymerization; wherein said procedure further comprises the addition of a monomer including a strongly ionic group such that the hydrophilic polymer composition thus obtained further includes, in addition to the hydrophobic and hydrophilic monomers, the monomer with a strongly ionic group.
2. The membrane electrode assembly according to claim 1 , which further comprises at least one defined channel for the transmission of a liquid or gaseous reaction component to and/or from at least one of the electrodes.
3. The assembly according to claim 1 , wherein the monomer having said ionic group is physically trapped within the polymer composition.
4. The assembly according to claim 1 , which comprises a catalyst.
5. The assembly according to claim 4 , and which contains at least one channel for the transmission of a liquid or gaseous reaction component to and/or from at least one of the electrodes, wherein the at least one channel allows transmission of the reaction component to the catalyst.
6. A hydrophilic polymer composition obtainable by a procedure comprising copolymerization, in the presence of water, of hydrophobic and hydrophilic monomers that give a hydrophilic polymer composition on polymerization; wherein said procedure further comprises the addition of a monomer including a strongly ionic group such that the hydrophilic polymer composition thus obtained further includes, in addition to the hydrophilic and hydrophobic monomers, the monomer with a strongly ionic group.
7. The polymer according to claim 6 , which has cationic sites.
8. The polymer according to claim 6 , which has anionic sites.
9. The polymer according to claim 6 , which has a water uptake of no more than 85%.
10. The polymer according to claim 6 , wherein the hydrophobic monomer is acrylonitrile.
11. The polymer according to claim 6 , wherein the hydrophilic monomer is vinylpyrrolidone.
12. The polymer according to claim 6 , which is cross-linked.
13. The polymer according to claim 12 , wherein the monomers include a separate cross-linking agent.
14. The polymer according to claim 6 , wherein the polymerisation comprises γ-irradiation or thermal initiation.
15. The assembly according to any of claim 1 , which is in the form of a fuel cell.
16. The assembly according to claim 1 , which is in the form of an electrolyser.
17. The assembly according to claim 1 , which is in the form of a stack.
18. The assembly, according to claim 1 , wherein the monomer having said strongly ionic group is chemically bonded as part of the polymer.
19. The polymer, according to claim 6 , wherein the monomer having said ionic group is physically trapped within the polymer composition.
20. The polymer, according to claim 6 , wherein the monomer having said strongly ionic group is chemically bonded as part of the polymer.