Polyelectrolyte membrane having, as base therefor, polymer having high density of acidic functional groups

A method for producing a polyelectrolyte membrane, comprising

• (A) the step of preparing a hydrophobic polymer to produce a block a,
• (B) the step of polymerizing the block a with a monomer having an acidic functional group protected by a protecting group or a monomer having a phosphonic acid group protected by a protecting group via a spacer structure to form a block b, and producing a block copolymer having an a-b type unit in which the block a and the block b composed of a unit of the monomer by polymerization are covalently linked;
• and
• (C) the step of removing the protecting group of the block b to produce a polymer containing the acidic functional group or the phosphonic acid group in an amount of at least 0.70 in the monomer unit constituting the block b and containing the acidic functional group or the phosphonic acid group on a side chain,
• wherein
• the hydrophobic polymer is a hydrophobic hydrocarbon-based vinyl polymer, and
• the hydrophobic hydrocarbon-based vinyl polymer is a polystyrene-based polymer, the polystyrene-based polymer containing at least one member selected from the group consisting of polyacetylstyrene, polyanisoylstyrene, polybenzoylstyrene, polybiphenylstyrene, polybromoethoxystyrene, polybromomethoxystyrene, polybromostyrene, polybutoxymethylstyrene, poly-tert-butylstyrene, polybutylstyrene, polychlorofluorostyrene, polychloromethylstyrene, polychlorostyrene, polycyanostyrene, polydichlorostyrene, polydifluorostyrene, polydimethylstyrene, polyethoxymethylstyrene, polyethoxystyrene, polyfluoromethylstyrene, polyfluorostyrene, polyiodostyrene, polymethoxycarbonylstyrene, polymethoxymethylstyrene, polymethylstyrene, polymethoxystyrene, polyperfluorostyrene, polyphenoxystyrene, polyphenylacetylstyrene, polyphenylstyrene, polypropoxystyrene, polytoluoylstyrene, and polytrimethylstyrene.

A composite polymer membrane comprising

• (1) a polymer having an acidic functional group, and
• (2) a polymer having a basic functional group,
• wherein (1) the polymer having an acidic functional group is
• (i) a block copolymer having at least an a-b type unit in which a block a and a block b are covalently linked,
• and/or
• (iii) a polymer containing a monomer unit having a phosphonic acid group via a spacer structure and containing no highly hydrolyzable functional group between the main chain structure and the phosphonic acid group,
• the block a in (i) contains a hydrophobic polymer or water-repellent polymer,
• the block b in (i) contains a polymer having an acidic functional group on a side chain or the polymer in (iii), or
• the side chain of the block b in (i) contains a graft chain containing a monomer unit having an acidic functional group, and
• the composite polymer membrane produces a conductivity of 1.0×10−3 S/cm or higher.