Preparation method of ion exchange membrane for monovalent/divalent cation separation

The invention relates to the field of high-molecular polymer separation membrane materials, and discloses a cation exchange membrane for monovalent/divalent ion separation, which not only contains a rigid aromatic main chain structure, but also contains a flexible fat side chain structure with a hydrophilic cation exchange group. In a film forming process, a hydrophobic main chain and a hydrophilic side chain are respectively self-aggregated to form a hydrophobic aromatic region microphase and a hydrophilic ion cluster microphase, so that an ion channel with a proper size can be formed; different aliphatic side chains are introduced to a polymer main chain respectively, and through electrostatic interaction difference between different types of cation exchange groups carried by the side chains and monovalent/divalent cations (such as Li < + >/Mg < 2 + >) with the same charge property but different charge properties, the migration rate ratio and the ion exchange equilibrium constant among the cations are chang