Design of pendent imidazolium side chain with flexible ether-containing spacer for alkaline anion exchange membrane

A novel approach is proposed to design anion exchange membranes (AEMs) containing pendent imidazolium side chains with flexible ether-containing spacer by the Williamson etherification between chloromethylated polysulfone and as-synthesized hydroxyl-bearing imidazolium. The introduction of long flexible ether-containing spacer chains enhances the mobility of terminated imidazolium groups and ion interactions. It facilitates the formation of a good hydrophilic/hydrophobic micro-phase separation structure, which is confirmed by the scattering peak of SAXS. As a result, the membranes exhibit high conductivity and excellent anti-swelling ability. The membrane with IEC of 1.55 mmol g(-1) shows considerable hydroxide conductivity (72 mS cm(-1), 60 degrees C), low swelling ratio (7.3%, 60 degrees C), and great tensile strength in hydrated state (43.4 MPa, 20 degrees C). The existence of long spacer chain also improved the alkaline stability. After immersion in 60 degrees C, 1 M KOH solution for 168 h, hydroxide conductivity and tensile strength of the membrane remain constant. The ether-containing side chains fabricated in this work provides a universal promising method to balance hydroxide conductivity and dimensional and alkaline stability.