Membranes having improved mechanical properties, for use in fuel cells
View Patent ↗An acid-doped, single-layer or multilayer polymer membrane comprising at least one layer A of a polymer blend with contains: a) from 0.1 to 99.9% by weight of one or more polymers comprising recurring azole units of the formula 1A and/or 1B: wherein the radicals Ar, Ar 1 , and Ar 2 are tetravalent, divalent or trivalent aromatic or heteroaromatic groups and the radicals X are each and oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a 1-20 carbon group, in admixture with b) from 99.9 to 0.1% by weight of a polysulfone containing recurring unit having no sulfonic acid groups.
1. An acid-doped, single-layer or multilayer polymer membrane comprising at least one layer A of a polymer blend comprising:
a) from 0.1 to 99.9% by weight of one or more polymers comprising recurring azole units of the formula 1A and/or 1B:
wherein the radicals Ar, Ar 1 and Ar 2 are tetravalent, divalent or trivalent aromatic or heteroaromatic groups and the radicals X, which are identical within a repeating unit, are each an oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a group having 1-20 carbon atoms, in admixture with
b) from 99.9 to 0.1% by weight of a polysulfone comprising recurring units of the formula 2A, 2B, 2C, 2D, 2E, 2F and/or 2G and having no protonated sulfonic acid groups —SO3H or no protonable sulfonic acid salt groups of the formula —SO 3 M + ,
wherein M + is an inorganic or organic cation:
—O—R—SO 2 —R— (2A)
—O—R—SO 2 —R—O—R— (2B)
—O—R—SO 2 —R—O—R—R— (2C)
—O—R—SO 2 —R—R—SO 2 —R— (2E)
—O—R—SO 2 —R—R—SO 2 —R—O—R—SO 2 —] (2F)
O—R—SO 2 —R SO 2 —R—R (2G),
wherein the radicals R are identical or different and are each, independently of one another are 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 4,4′-biphenyl, a divalent radical of a heteroaromatic, a divalent radical of a C 10 -aromatic or a divalent radical of a C 14 -aromatic and
wherein the polymer(s) comprising recurring azole units of the formula 1A and/or 1B are acid doped with a Lewis or Brønsted acid.
2. The doped polymer membrane as claimed in claim 1 , wherein X, which are identical within a repeating unit are each an oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a branched or unbranched alkyl, alkoxy group or an aryl group.
3. The doped polymer membrane as claimed in claim 2 , wherein the number of recurring azole units in the polymer is greater than or equal to 100.
4. The doped polymer membrane as claimed in claim 1 , wherein the number of recurring azole units in the polymer is greater than or equal to 10.
5. The doped polymer membrane as claimed in claim 1 , wherein the polymer a) is a polymer comprising recurring beuzimidazole units of the formula 1C):
wherein n is an integer greater than or equal to 10.
6. The doped polymer membrane as claimed in claim 5 , wherein the polymer blend comprises
a) from 50 to 99% by weight of a polymer comprising recurring azole units of the formula 1A and/or 1B, in admixture with
b) from 1 to 50% by weight of a polysulfone comprising recurring units of the formula 2A, 2B, 2C, 2D, 2E, 2F and/or 2G which has no sulfonic acid groups.
7. The doped polymer membrane as claimed in claim 1 , wherein the polysulfone is one of the following formulas:
wherein n is greater than 0.
8. The doped polymer membrane as claimed in claim 1 , wherein the polysulfone is
wherein n is greater than 0.
9. The doped polymer membrane as claimed in claim 8 , which is doped with hydrochloric acid, sulfuric acid and/or phosphoric acid.
10. The doped polymer membrane as claimed in claim 1 , which comprises at least two layers A and B which are each obtained from a polymer blend as defined in claim 1 and differ from one another in the content of polysulfone b) and in their thickness.
11. The doped polymer membrane as claimed in claim 1 , which comprises at least three layers A, B and C wherein layers A and B each obtained from a polymer blend as defined in claim 1 , with the middle layer C differing from the two outer layers A and B in the content of polysulfone b).
12. The doped polymer membrane as claimed in claim 11 , wherein the middle layer C contains no polysulfone b).
13. The doped polymer membrane as claimed in claim 1 , which has a total thickness of from 5 to 100 μm.
14. The doped polymer membrane as claimed in claim 1 , whose proton conductivity at room temperature is above 30 mS/cm and whose E modulus after 10 minutes at 100° C. is greater than 10 MPa.
15. A process for producing a doped polymer membrane as claimed in claim 1 , which comprises wetting a polymer blend as defined in claim 1 with phosphoric acid at temperatures in the range from room temperature to 100° C. and atmospheric or superatmospheric pressure.
16. An article which comprises the doped polymer membrane as claimed in 1 , wherein said article is used in fuel cells, in electrolysis, in capacitors or in battery systems.
17. A fuel cell comprising the membrane as claimed in claim 1 .
18. A membrane electrode unit comprising at least one polymer membrane as claimed in claim 1 .
19. The doped polymer membrane as claimed in claim 1 , wherein the polysulfone is one of the following formulas:
where n>0
where n<0
wherein n is greater than 0.
20. The doped polymer membrane as claimed in claim 1 , which is doped with phosphoric acid.