Poly (aryl ether ketone)/polymeric ionic liquid with anisotropic swelling behavior for anion exchange membranes

Abstract Dimensionally stable and high level of conductivity is of importance for alkaline exchange membrane (AEM) applications. However, the main challenge for AEMs is to control swelling behavior and construct ion transport “high way” simultaneously. Here we report a series of self-crosslinked membranes using poly (aryl ether ketone) as rigid matrix and imidazolium-based polymeric ionic liquid as hydroxyl transporting groups. The obtained membranes possess anisotropic swelling behavior: no more than restricted 4% in-plane swelling ratio indicate excellent dimensional stability; while, obvious through-plane swelling guaranteed abundant water absorption in the hydrophilic domains, which benefited sufficient hydroxide ion dissociation and improved ion conductivity. The swelling ratio of through-plane can be more than tenfold of in-plane. This result quantifies the dramatic influence of flexible polymeric ionic liquid on specific swelling behavior of membranes for the first time. Moreover, the distinct microscopic phase separation endows the membranes possessing high ion conductivity (0.067 S cm −1 ). The introduction of long-chain polymeric ionic liquid not only facilitate continuous pathway, but also reduce the dependency on λ (average hydration number vs. positive group). After treatment in alkaline conditions, the membranes still exhibit more than 8 MPa tensile strength.