Ion exchange polymers and ion exchange membranes incorporating same
An ion exchange membrane is provided which includes an ion exchange polymer that is partially cross-linked. The partially cross-linked ion exchange polymer will be more stable and will not be washed out over time. The ion exchange polymer may be UV or chemically cross-linked, wherein a cross-linking compound is added to the ion exchange polymer either before or after coupling to a support material. A support material may be made of, or be coated with, a cross-linking compound and the support material may initiate cross-linking proximal to the support material. The support material may be made of a material that chemically bonds with the ionomer.
1. An ion exchange membrane comprising:
a) an ion exchange polymer having reactive sites;
wherein the ion exchange polymer is partially cross-linked having some portion of reactive sites cross-linked to form cross-linked sites;
wherein the ion exchange polymer is an anion exchange polymer;
b) a support material having pores, wherein the ion exchange polymer is configured on a first side of the support material to form a first ionomer layer and is configured in the pores a support material to form an imbibed ionomer portion;
wherein the support material comprises a cross-linking compound that is coupled to the support material forming bonding sites, and wherein the imbibed ionomer portion is bonded to the bonding sites of the cross-linking compound of the support material; and
wherein first ionomer layer has a concentration of cross-linked sites that is at least 10% higher in mol % than a concentration of cross-linked sites of the imbibed ionomer portion; and
wherein the cross-linking compound that is coupled to the support material is coated onto the support material and comprises divalent barium cations.
2. The ion exchange membrane of claim 1 , wherein the ion exchange polymer is an acidic sulfonated polyetherketoneketone and is cross-linked with barium cations to create ionic crosslinks between the sulfonate groups attached to the aromatic rings of the polyetherketoneketone.
3. The ion exchange membrane of claim 1 , wherein the cross-linked sites comprise a cross-linking agent selected from the group consisting of: polyisocyanates, polyurethane, blocked polyurethane, polyurea, blocked polyurea, polyamines, blocked polyamines and dicyanodiamides.
4. The ion exchange membrane of claim 3 , wherein the cross-linked sites are formed by exposure to ultraviolet light.
5. The ion exchange membrane of claim 1 , wherein the first ionomer layer is configured partially in the pores of the support material to form a support coating layer.
6. The ion exchange membrane of claim 1 , wherein the first ionomer layer contains no support material on a first side of the ion exchange membrane.
7. The ion exchange membrane of claim 1 , comprising a second ionomer layer that contains no support material on a second side of the ion exchange membrane.
8. The ion exchange membrane of claim 7 , wherein the second ionomer layer has a concentration of cross-linked sites that is at least 10% higher than a concentration of cross-linked sites of the imbibed ionomer portion.
9. The ion exchange membrane of claim 1 , wherein the ion exchange polymer extends through the pores of the support material from said first side to a second side of the support material.
10. The ion exchange membrane of claim 9 , wherein the first ionomer layer is configured partially in the pores of the support material to form a support coating layer.
11. The ion exchange membrane of claim 1 , wherein the support material is a microporous membrane having a mean flow pore size of 1 μm or less.
12. The ion exchange membrane of claim 1 , wherein the support material is made out of a cross-linking compound.
13. The ion exchange membrane of claim 12 , wherein the cross-linking compound of the support material comprises divalent barium cations.