A poly(2-acrylamido-2-methyl-1-propane-sulphonate) (PAMPS) ionomer containing both sodium and quaternary ammonium cations functionalised with an ether group, has been characterised in terms of its thermal properties, ionic conductivity and sodium ion dynamics. The ether oxygen was incorporated to reduce the Na+ association with the anionic sulfonate groups tethered to the polymer backbone, thereby promoting ion dissociation and ultimately enhancing the ionic conductivity. This functionalised ammonium cation led to a significant reduction in the ionomer T-g compared to an analogue system without an ether group, resulting in an increase in ionic conductivity of approximately four orders of magnitude. The sodium ion dynamics were probed by Na-23 solid-state NMR, which allowed the signals from the dissociated (mobile) and bound Na+ cations to be distinguished. This demonstrates the utility of Na-23 solid-state NMR as a probe of sodium dynamics in ionomer systems. (C) 2015 Elsevier Ltd. All rights reserved.