Orderly branched anion exchange membranes bearing long flexible multi-cation side chain for alkaline fuel cells

Poly(arylene ether ketone) (PEK) based anion exchange membranes (AEMs) with different structures were successfully prepared in this work by polycondensation, bromination and Menshutkin reaction. The orderly branched AEMs (OBAEMs) have an obvious microphase separation morphology and well-connected ion cluster region, as confirmed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The OBAEMs with IEC of 1.81−2.01 meq g-1 showed superior ionic conductivity (93.3−119 mS cm-1) over the random branched AEM (RBAEM) (78.9 mS cm-1) and the side-chain AEM (SAEM) (67.8 mS cm-1). Meanwhile, the maximum power density of a single cell using the OBAEMs (130.8 mW cm-2) is much higher than that using the RBAEM (84.1 mW cm-2) and the SAEM (63.2 mW cm-2). Besides this, the OBAEMs presented reasonable alkaline stability after exposed to a harsh alkaline environment at 80 °C for 500 h. All those results pointed out that the AEMs with orderly branched structure holds a promising future for application in fuel cells.