Considerable research is being pursued to alleviate the issues in anion exchange membranes (AEMs) in order to make these novel polyelectrolytes comparable in performance to proton exchange membranes, the current industry standard for fuel cells and water electrolysers. Although there are several advantages of using AEMs, these materials suffer from very low conductivities of the anions which hamper their usage in large industrial setups needing considerable power densities in the equipment. The bottom-up approach of designing membranes based on microscopic properties has gained traction amongst many researchers primarily because such methods have very good predictability and excellent transferability between different properties. In this work, we have performed molecular dynamics simulations to determine the thermodynamic and transport characteristics, namely the density of the membranes and the diffusivity and conductivity of the anions for three AEMs namely Poly ether ether ketone (PEEK), Sustainion and HMT-PMBI anion exchange membrane. These membranes have given quite a credible performance as AEMs in a water electrolyser, but the atomistic details of these materials are yet to be studied. Our work aims at bridging this critical gap in literature by providing a detailed molecular understanding of the behaviour of the PEEK, Sustainion and HMT-PMBI AEMs under different levels of hydration at different temperatures. The density exhibits a non-monotonic trend while the diffusivity showcases a non-linear behaviour with hydration, similar to what has been observed for other membranes. Furthermore, the dependence of temperature on diffusion is Arrhenius-like with the activation energies exhibiting a non- monotonic relationship akin to the density. An explanation for these different phenomena is provided on the basis of the counteracting influence of the potential of mean force and co-ordination number of the ions at different hydration levels. Finally, the simulation results are compared with experimental data, further underscoring the relevance and robustness of our molecular model.
