Anionic membranes incorporating functional additives

Abstract

An ultra-thin anion exchange membrane incorporates functional additives to provide improved water management. Without the functional additives the ultra-thin membrane may have high cross-over and not be effective for many applications. A composite anion exchange membrane includes a porous scaffold support such as a porous polymer. The anion exchange polymer may be coupled to the porous scaffold, such as by being imbibed into the pores of the porous scaffold. The functional additives may contribute to increase water production, water retention, back-diffusion and reduce the gas crossover. A functional additive may include a reactive species, including a catalyst that reacts with oxygen or hydrogen, a plasticizer, a hygroscopic material and/or a radical scavenger.

Claims

1. An anion exchange membrane comprising: a) an anion exchange polymer comprising: i) polyphenylenes homopolymer backbones with side chain consisting of hydrophilic side chains with a CF.sub.3 linkage to said backbone; and ii) said hydrophilic side chains being linear hydrocarbon side chains having functional groups; wherein the anion exchange polymer extends as a first surface layer on a first side and as a second surface layer on a second side, opposing said first side, of the anion exchange membrane; b) a functional additive configured within the anion exchange membrane, between said first surface layer of said anion exchange polymer and said second surface layer of said anion exchange polymer, wherein the functional additive comprises a radical scavenger comprising polydopamine.

2. The anion exchange membrane of claim 1, further comprising a porous scaffold.

3. The anion exchange membrane of claim 2, wherein the porous scaffold comprises a porous polymer.

4. The anion exchange membrane of claim 3, wherein the porous polymer is selected from the group consisting of: polyethylene, polypropylene, polyether-ether-ketone (PEEK), and poly(tetrafluoroethylene).

5. The anion exchange membrane of claim 1, wherein the thickness of the anion exchange membrane is no more than 50 ?m.

6. The anion exchange membrane of claim 1, wherein the polyphenylenes backbones are aryl ether linkage free.

7. The anion exchange membrane of claim 1, wherein the functional groups of the anion exchange polymer is selected from the group of consisting of: quaternary ammonium, tertiary diamines, phosphonium, benz(imidazolium), sulphonium, guanidinium, metal cations, and pyridinium.

8. The anion exchange membrane of claim 1, wherein the functional additive further comprises reactive species selected from the group consisting of: carbon nanotubes, graphene, carbon black, sulfated zirconia and any combination of them.

9. The anion exchange membrane of claim 1, wherein the functional additive further comprises a catalyst.

10. The anion exchange membrane of claim 9, wherein the catalyst comprises platinum or a platinum group metal.

11. The anion exchange membrane of claim 9, wherein the catalyst is configured in the anion exchange polymer.

12. The anion exchange membrane of claim 9, wherein the catalyst is coupled to the porous scaffold.

13. The anion exchange membrane of claim 1, wherein the functional additive further comprises a plasticizer in the anion exchange polymer.

14. The anion exchange membrane of claim 13, wherein the plasticizer is selected from the group consisting of: 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-Hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (MC6), glycerol, and Nylon 6,6.

15. The anion exchange membrane of claim 1, wherein the functional additive further comprises a hygroscopic material.

16. The anion exchange membrane of claim 15, wherein the hygroscopic material is selected from the group consisting of: Aluminium oxide (Al2O3), Heteropolyacid (HPA)-based inorganic filler, IL-functionalised carbon materials, Carbon black, Multiwallcarbon nanotubes, Reduced Graphene Oxide, Phosphoric acid-modified silica, Imidazole-modified silica, Phosphate-modified titanium zirconium oxide, and Zeolitic imidazolate framework-8 (ZIF-8).

17. The anion exchange membrane of claim 1, wherein the hygroscopic material is configured in the anion exchange polymer.

18. The anion exchange membrane of claim 1, wherein the radical scavenger further comprises cerium oxide.

19. The anion exchange membrane of claim 1, wherein the radical scavenger is configured in the anion exchange polymer.

20. The anion exchange membrane of claim 1, wherein the radical scavenger further comprises manganese oxide.

21. The anion exchange membrane of claim 1, further comprising a porous scaffold and wherein at least a portion of the polydopamine configured within the anion exchange membrane is coupled to said porous scaffold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.

(2) FIGS. 1A and 1B show exemplary anion exchange polymers.

(3) FIG. 2 shows a cross-sectional view of an exemplary porous scaffold having functional additives coupled thereto.

(4) FIG. 3 shows a cross-sectional view of an exemplary composite ultra-thin anion exchange membrane having a porous scaffold and an anion exchange polymer configured within the pores of the porous scaffold and functional additives.

(5) FIG. 4 shows a cross-sectional view of an exemplary ultra-thin anion exchange membrane including functional additives.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

(6) Corresponding reference characters indicate corresponding parts throughout the several views of the figures. The figures represent an illustration of some of the embodiments of the present invention and are not to be construed as limiting the scope of the invention in any manner. Further, the figures are not necessarily to scale, some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

(7) As used herein, the terms comprises, comprising, includes, including, has, having or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Also, use of a or an are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

(8) Certain exemplary embodiments of the present invention are described herein and are illustrated in the accompanying figures. The embodiments described are only for purposes of illustrating the present invention and should not be interpreted as limiting the scope of the invention. Other embodiments of the invention, and certain modifications, combinations and improvements of the described embodiments, will occur to those skilled in the art and all such alternate embodiments, combinations, modifications, improvements are within the scope of the present invention.

(9) FIGS. 1A and 1B show exemplary anion exchange polymers. Exemplary anion exchange polymers are composed of an aromatic/polyaromatic ring in polymer backbone, such as biphenyl, terphenyl, fluorenyl, and a tethered alkyl halide (e.g. bromide) side chain which can be converted to quaternary ammonium hydroxide groups.

(10) FIG. 2 shows a cross-sectional diagram of a porous scaffold 20 having a thickness 25 from a first side 24 and an opposite second side 26. As described herein the thickness may be ultra-thin, such as about 50 ?m or less, about 35 ?m or less, about 25 ?m or less, about 20 ?m or less, about 15 ?m or less, about 10 ?m or less, about 5 ?m or less and any range between and including the thickness values provided, such as between about 5 ?m and 25 ?m. The porous scaffold has pores 22 and an open structure extending from the first side 24 to the second side 26, allowing for a flow of appropriate fluid or anion exchange polymer to imbibe the pores from the first to the second side. The porous scaffold is air permeable when not imbibed with the anion exchange polymer. Also, the porous scaffold may include functional additives 150 coupled to the structure, such as being bound to the porous scaffold. A functional additive may be coated onto the porous scaffold and adhered by a melting of the polymer of with a binder or adhesive. The functional additive may be incorporated into the polymer of the porous scaffold such as by blending prior to melt processing, or by co-coagulation, such as during co-coagulation with polytetrafluoroethylene. As discussed herein, the porous scaffold may be a polymer, such as an expanded polymer including, but not limited to, a fluoropolymer, expanded polytetrafluoroethylene (ePTFE), a hydrocarbon polymer such as polyethylene, polypropylene polyether-ether-ketone, (PEEK), and the like.

(11) FIG. 3 shows a cross-sectional diagram of an exemplary ultra-thin anion exchange membrane 10 which is a composite anion exchange membrane 11 comprising a porous scaffold 20 imbibed with an anion exchange polymer 70. The anion exchange polymer forms surface layers 78 and 79 on the two faces or opposing surfaces of the imbibed porous scaffold. These surface layers are the anion exchange polymer extending from the porous scaffold 20. Note that a surface layer may be configured on only one side or surface of the composite anion exchange membrane 11. The anion exchange polymer may include a functional additive 150 and this functional additive may be configured in the surface layers and throughout the polymer within the pores 22 of the porous scaffold. The thickness 75 of the composite anion exchange membrane extends from the first side 74 to the second side 76 and as described herein may be ultra-thin, such as about 50 ?m or less, as about 35 ?m or less, about 25 ?m or less, about 20 ?m or less, about 15 ?m or less, about 10 ?m or less, about 5 ?m or less and any range between and including the thickness values provided, such as between about 5 ?m and 25 ?m. Also, the porous scaffold may include a functional additive 150 and this functional additive may be a different functional additive from the functional additive in the anion exchange polymer, such as different chemically having a different chemical structure, or different in physical structure, such as having a different size. The functional additive coupled to the porous scaffold may have a different volumetric concentration than the functional additive configured with the anion exchange polymer.

(12) FIG. 4 shows a cross-sectional diagram of an ultra-thin anion exchange membrane 110 comprising functional additives 150. Optionally, the anion exchange polymer may be a cross-linked anion exchange polymer 71. The ultra-thin anion exchange membrane has a thickness 75 from a first side 74 to a second side 76.