Theoretical simulation of ion transport in main-chain poly(arylene piperidinium) anion exchange membranes with crown ether groups

Abstract

ABSTRACT Experimental studies have confirmed that introduction of the proper content of dibenzo-18-crown-6-ether (DE) into main-chain poly(arylene piperidinium) anion exchange membranes (AEMs) improved the efficiency of OH− transport. In this study, models of the AEMs (PDTP-x) were constructed with varying molar contents of DE groups (x = 0, 0.05, 0.10, 0.15, 0.20 and 0.25). Molecular dynamics simulations were employed to investigate the microscopic effects of the DE groups on OH− transport. The analysis examined the impact of the volume of the overlapping hydration shells around piperidinium groups and the continuities and uniformities of the ion transport channels. Furthermore, the stabilities of the hydrogen bonds between water molecules explained the effect of x on OH− transport. The results showed that the total overlap volume initially increased and then decreased as x increased. When the content of DE groups was appropriate, the hydration shells of the cations exhibited considerable overlap, which facilitated the formation of continuous and uniform ion transport channels. Additionally, the stabilities of the water hydrogen bonds initially decreased and then increased as x increased. The stabilities of the hydrogen bonds were lowest when the DE content was optimal, which facilitated the transport of OH−.