Dielectric constant of mixture of polymers and ionic liquids and its effect on ionic conductivity*

Simulations that only include the ion-dipole and dipole-dipole interactions often accurately predict the dielectric constant of ion-containing liquids. However, an accurate description of ionic liquids requires the inclusion of the collective translational dipole moment due to ion translation, yet our understanding of this effect is still largely limited. In this study, we calculate the dielectric constant of a mixture of polymers and ionic liquids using Stockmayer fluid molecular dynamics simulations. Our model accounts for the electrostatic interactions and dielectric response of the species through the ion-ion, ion-dipole, and dipole-dipole interactions. We discuss the mixing rule of the dielectric constant of the liquid mixture as well as the effect of the translational contribution to the dielectric constant on ionic conductivity. We also show that despite the drastic model simplification, the simulated ionic conductivity of ethylammonium nitrate closely matches the experimental value.