| abstract |
(57) [Problem] To provide a fuel cell with uniform properties such as proton conductivity, gas barrier properties, and mechanical properties, and at the time of preparing a membrane-electrode assembly, which is less likely to cause a defect at a bonding portion. Provided is a method for producing a sulfonated polymer membrane having no wrinkles, blisters, or irregularities useful as a membrane. The present invention relates to a method for producing a sulfonated polymer membrane comprising a polymer compound (B) in which a part of the aromatic ring of the polymer compound (A) having an aromatic ring is substituted with a sulfonic acid group. This is achieved by a manufacturing method including a step of drying while applying tension to the substrate, or a step of fixing the film to a frame and drying. |