| abstract |
A cation-exchange membrane is prepared by impregnating a diene monomer having carboxylic acid group or a functional group which can be converted to a carboxylic acid group, into a fluorinated polymer membrane having cation-exchangeable groups; partially polymerizing said diene monomer; swelling the membrane with a water miscible organic solvent and heat-treating the swollen membrane and if necessary, converting the functional groups to carboxylic acid groups. |