A series of phenolphthalein-based poly(arylene ether sulfone nitrile)s containing imidazolium groups on the side chains was synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. Strong polar nitrile groups were introduced into the polymer backbone with the intention of improving the dimensional stability of the AEMs. The content of nitrile groups was varied to study the effect of nitrile groups on the morphology and properties of the AEMs. With imidazolium groups locating on the cardo side chains, all the AEMs exhibited well-defined microphase-separated structures. Furthermore, the imidazolium groups tend to aggregate with increasing the nitrile group content resulting in the formation of larger and more interconnected ionic domains in the AEMs. The ionic conductivity in the range of 2.21-8.14 x 10(-2) S cm(-1) increased with increasing the nitrile group content and temperature. The AEMs showed superb ratios of conductivity to IEC or swelling ratio at 60 degrees C, good mechanical properties, and thermal and alkaline stability. A single H-2/O-2 fuel cell using the as-prepared AEMs showed an open circuit voltage of 0.95 V and a peak power density of 50.6 mW cm(-2) at 60 degrees C. (C) 2015 Elsevier B.V. All rights reserved.