NOVEL SULFONIC ACID GROUP-CONTAINING SEGMENTED BLOCK COPOLYMER AND USE THEREOF

Disclosed is a proton exchange membrane for use in fuel cells, which not only has improved proton conductivity and resistance to swelling caused by hot water but also has greater durability when used in a fuel cell, as well as a sulfonic acid group-containing segmented block copolymer constituting the proton exchange membrane, a membrane electrode assembly using the proton exchange membrane, and a fuel cell using the membrane electrode assembly. A sulfonic acid group-containing segmented block copolymer, which is a di- or multi-block copolymer including, within a molecule, at least one kind of hydrophilic segment and at least one kind of hydrophobic segment, a 0.5 g/dL solution thereof dissolved in N-methyl-2-pyrrolidone as a solvent showing a logarithmic viscosity measured at 30°C in the range of 0.5 to 5.0 dL/g, wherein the copolymer has at least one kind of hydrophobic segment represented by Chemical Formula 1, the segment has a structure bound to a group represented by Chemical Formula 2, and the hydrophilic segment has at least one kind of structure represented by Chemical Formula 3 or Chemical Formula 3-2.