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Abstract

Use of a proton exchange membrane M in proton exchange membrane fuel cells, wherein the membrane M comprises a blend of (I) at least one polybenzimidazole polymer PBI which comprises, in polymerized form, at least 90 mol-% monomeric units U of formula (I) and/or (II), based on the total amount of monomeric units of the polybenzimidazole polymer PBI, wherein Y is a substituted element selected from O and S; or Y is a single carbon-carbon bond; Z is selected from the group consisting of divalent C₁-C₁₀ alkanediyl; divalent C₂-C₁₀ alkenediyl; divalent C₆-C₁₅ aryl; divalent C₅-C₁₅ heteroaryl; divalent C₅-C₁₅ heterocyclyl; divalent C₆-C₁₉ aryl sulfone; and divalent C₆-C₁₉ aryl ether; and wherein the total amount of monomeric units U in the polybenzimidazole polymer PBI is from about 100 to about 10,000; and (III) at least one sulfonated polymer SP, which comprises, in polymerized form, at least 50 mol-% monomeric units U′, based on the total amount of monomeric units of the sulfonated polymer SP, wherein at least one of the monomeric units U′ carries at least one moiety —SO₃H; wherein the membrane M is essentially free of water and exhibits a proton conductivity at a temperature of 100° C. or more, preferably in the range of from 100 to 250° C. of at least 10⁻⁵ S/cm, as measured by impedance method.

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