Polymer electrolyte membrane

A method for producing a branched multi-block copolymer, comprising:

• (S1) forming a branched hydrophobic block by dissolving a bisphenol-based monomer, an aromatic dihalogen-based monomer and a brancher in an organic solvent and polymerizing them;
• and
• (S2) dissolving said branched hydrophobic block formed in the step (S1) and a bisphenol-based monomer or an aromatic dihalogen-based monomer;
• a phenol-based monomer having acid substitutents, a bisphenol-based monomer having acid substitutents or an aromatic dihalogen-based monomer having acid substitutents;
• and a brancher in an organic solvent and polymerizing them to produce a branched hydrophilic block and a branched multi-block copolymer at the same time,
• wherein, in the step (S2) for forming a hydrophilic block, the aromatic dihalogen-based monomer and the phenol-based or bisphenol-based monomer are selected to effect a reaction therebetween, and based on the monomers and the brancher, the total equivalent weight of a hydroxy group to the total equivalent weight of a halogen group is more than 70/100, not exceeding 95/100, or the total equivalent weight of a halogen group to the total equivalent weight of a hydroxy group is more than 70/100, not exceeding 95/100,
• wherein, throughout the steps (S1) and (S2), the total equivalent weight of a hydroxy group is the same as the total equivalent weight of a halogen group, based on the monomers and the branchers, and
• wherein the hydrophilic block has the total number of repeating units of 100 to 350.

A method for producing an acidified branched multi-block copolymer, comprising:

• substituting acid for an acid salt by adding an acid solution to a branched multi-block copolymer, the branched multi-block copolymer comprising:
• a hydrophobic block having a plurality of repeating units represented as chemical formula 1;
• and
• a hydrophilic block having a plurality of repeating units represented as chemical formula 2,
• wherein A, X and Y are each
• independently,
• R is —NO2 or —CF3,
• Z is
• Q is —SO3−M+, —COO−M+, —PO3H−M+or —PO32−2M+, and M is Na or K,
• B is
• G is X, and G′ is Z,
• 0<u/t<1, and 0<w/v<1,
• 0.7<(e+1.5*g)/(f+h)≦0.95 or 0.7<(f+h)/(e+1.5*g)≦0.95, and a+e+1.5(c+g)=f+h+b+d, in which a, b, c, d, e, f, g and h are molar ratios, and
• the hydrophilic block has a total number of repeating units of 100 to 350.