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.