Influence of Polymerization and Restricted Dipole Motion on the Dielectric Constants of Ionic Liquids

We employ molecular dynamics simulations using the Stockmayer fluid (SF) model, in which ionic groups are treated as charged dipolar spheres, to study the dielectric constants of ionic liquids (ILs) and polymerized ionic liquids (PILs). The simulations model ethylammonium nitrate and poly(<i>N</i>-vinyl ethylimidazolium bromide) by implementing both a freely rotating dipolar PIL model and one with restricted dipolar motion for the side chains. We compare their dielectric constants and analyze their dipole orientational order and correlations. We find that there is a relationship between degrees of rotational freedom and the dielectric constants of PILs, and this relationship defines the change in the dielectric constant of PILs compared to their monomeric IL counterparts.