Poly(aryl ether nitrile)s containing flexible side-chain-type quaternary phosphonium cations as anion exchange membranes

In order to effectively improve the properties of anion exchange membrane (AEM) materials, a series of novel poly(aryl ether nitrile)s with flexible side-chain-type quaternary phosphonium cations (PAEN-TPP-x) were designed and prepared on the basis of considering the influences of polymer backbone, cationic group species and the connection way between the cations and polymer chains. The synthetic method, structure and ion-exchange capacity, water absorption, swelling, hydroxide conductivity and alkaline stability of the obtained AEMs were studied. A comparative study with other reported AEMs was also performed for further exploration of the relationship between the structure and properties. These AEMs with flexible side-chain-type quaternary phosphonium cations displayed good comprehensive properties. Their water uptakes and swelling ratios were in the range of 11.6%–22.7% and 4.4%–7.8% at 60°C, respectively. They had hydroxide conductivity in the range of 28.6–45.8 mS cm−1 at 60°C. Moreover, these AEMs also exhibited improved alkaline stability, and the hydroxide conductivity for PAEN-TPP-0.35 could remain 82.1% and 80.6% of its initial value at 60 and 90°C in 2 mol L−1 NaOH solution for 480 h, respectively.