AROMATIC COPOLYMER HAVING PROTON CONDUCTIVE GROUP AND APPLICATION THEREOF

An aromatic copolymer comprises a hydrophilic segment (A) and a hydrophobic segment (B), wherein the hydrophilic segment (A) comprises a structural unit (1) having a proton conductive group, and the hydrophobic segment (B) comprises at least one structural unit selected from the group consisting of a structural unit (2) and a structural unit (3), wherein the structural unit (2) is a divalent structural unit having an aromatic ring and no proton conductive groups and having two bonding sites at the para-position of one ring included in the aromatic ring, and the structural unit (3) is a divalent structural unit having a benzene ring and is a structural unit different from the structural unit (2), the hydrophobic segment (B) in its entirety contained in the aromatic copolymer including both the structural unit (2) and the structural unit (3).