Composite anion-conducting membranes were prepared from polysulfone with grafted quaternary ammonium groups and dispersed nanoparticles of layered double hydroxide (LDH) with composition Mg0.62Al0.38(OH)(2)(Cl)(0.38)center dot 0.6H(2)O as inorganic filler. Two types of amines were used: small and flexible trimethylamine and bulky and rigid 1,4-diazabicyclo[2.2.2]octane (DABCO). The composite membranes have a distinctly lower water uptake and swelling and they can be hydrated at 60 degrees C without dissolution. Composites with DABCO have slightly lower water uptake and ionic conductivity than those with TMA. Their mechanical properties in fully humidified conditions are clearly enhanced with especially a nearly 3-fold increase of the Young modulus. In spite of their strongly reduced hydration, the conductivity of the composite membranes is comparable with that of the pristine ionomers, being in the range 2-4 mS cm(-1) at 25 degrees C. Furthermore, the membranes can be treated in alkaline conditions at 60 degrees C without losing their properties and the ionic conductivity reaches 30 mS cm(-1) under 95% RH. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.