Layered double hydroxide–polyphosphazene-based ionomer hybrid membranes with electric field-aligned domains for hydroxide transport

Abstract

With the aim to improve the conductivity of anion exchange membranes (AEMs), the layered double hydroxide (LDH) was added to the polyphosphazene-based ionomer, and an external AC electric field was applied to the LDH–polyphosphazene-based ionomer hybrid casting solution during solvent evaporation. The introduction of LDH nanoplatelets in AEMs significantly improved the conductivity, ion exchange capacity, water uptake, and mechanical properties of hybrid AEMs, but sacrificed lower dimensional stability. And, most importantly, the present technique is a potentially useful method for fabricating AEMs with oriented LDH nanoplatelets taking full advantage of the bulk conductivity of the LDH nanoplatelets and resulting in a 39% increase in conductivity in the trans-plane direction compared to that of normal methods. In addition, the novel polyphosphazene-based ionomer was designed not only to balance the hydroxide ions but also to improve interfacial adhesion with LDH nanoplatelets for improving the distribution of LDH nanoplatelets in hybrid AEMs.