Anion Exchange Membranes Based on Styrene–Ethylene/Butene–Styrene Consist of Two Grafting Forms: N Heterocyclic Cations with Alkyl Intervals and Flexible Long Hydrophobic Side Chains

In view of the problems of poly(styrene–ethylene/butene–styrene) (SEBS) being difficult to dissolve and poor mechanical properties, a series of SEBS-C16D60-DMHP-X (X represents the cationic graft ratio, 20–40%) anion exchange membranes (AEMs) have been prepared. Graft hydrophobic long chains were applied onto the SEBS skeleton to change its solubility, introducing hydrophobic long chains to help construct microphase separation structures and improve ion conductivity (up to 110.22 mS cm–1). The combination of the rigid ring structure in the ring cation with an alkyl spacer and the toughness of the SEBS skeleton, as well as the free folding of alkyl chains, greatly improved the mechanical properties of the AEM, and the swelling ratio of the membrane is well controlled (25.31%, at 80 °C). The alkaline resistance (conductivity decreased only 10.29% after 1400 h of immersion at 80 °C in 2 M NaOH solution) also continuously increased. The structure of this AEM will provide a very meaningful reference for the development of AEMs.