Polymer electrolyte composition

A polymer electrolyte composition comprising a polymer blend of (A) a sulfonated block copolymer and (B) a non-sulfonated aromatic polymer,

• (A) the sulfonated block copolymer comprising (i) a hydrophilic segment with sulfonic acid groups, and (ii) a hydrophobic segment with no sulfonic acid groups,
• (i) the hydrophilic segment comprising:
• (a) a structural unit according to formula (3)
• wherein,
• D3 is SO2 or CO, each b independently is 0 or 1 and at least one of b is 1, Z is a hydrogen atom or an alkali metal, Y3 is O or S, and Ar2 is a divalent aromatic residue having sulfonic acid groups;
• and
• (b) a structural unit according to formula (4)
• wherein,
• D4 is SO2 or CO, Y4 is O or S, and Ar3 is a divalent aromatic residue having sulfonic acid groups;
• and
• (ii) the hydrophobic segment comprising an aromatic ring residue in its main chain;
• (B) the non-sulfonated aromatic polymer being an aromatic polymer having no sulfonic acid groups and having the same structural unit as the structural unit contained in the hydrophobic segment of said sulfonated block copolymer;
• wherein the weight fraction Pb of the non-sulfonated aromatic polymer is in the range of from 0.03 to 0.4 calculated from the following equation:
• P
• b
• =
• W
• B
• W
• A
• +
• W
• B
• ,
• wherein WA is the weight of the sulfonated block copolymer (A), and WB is the weight of the non-sulfonated aromatic polymer (B).