Polymeric ion-exchange membranes are widely used as proton-conductive separators in fuel cells. Ionomers – polymer chains with ion-exchange groups bound to them – are often used for these purposes, and the most famous and widely used is Nafion. In the search for more chemically and mechanically stable alternatives to Nafion, an understanding of the nanophase separation that ionomers undergo at different levels of hydration and the effects that this has on conductivity and other properties is vital. On page 368 of this issue, Elshad Allahyarov and Philip Taylor report simulation studies of equilibrium morphologies in low-water ionomers. Amongst other things, their simulation results indicate that it is possible to generate larger clusters in polymers with longer side chains. The increased flexibility of longer side chains also modestly improves proton diffusion through the membrane.