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.