Effects of Molecular Size and Polarity on Viscosity Scaling and Ionic Conductivity of Polymerized Ionic Liquids

There are few computational studies in the literature on how molecular polarization affects the viscosity of polymeric ionic liquids (PILs) to the large computational expense of atomistic simulations. In this study, we perform coarse-grained molecular dynamics simulations of unentangled poly(1-ethyl-3-vinylimidazolium bis(trifluoromethane sulfonyl imide)) (PC₂VITFSI). We model the ionic side chains in PC₂VITFSI as charged, rotating dipolar spheres rigidly attached to polymer backbones. We compare the scaling of the viscosity with molecular weight to experimental observations and discuss the relation to scaling theories of the viscosities of uncharged polymer melts and polyelectrolyte solutions. Furthermore, we investigate how the molecular size and polarity of the side chains affect viscosity scaling and ionic conductivity in PC₂VITFSI, highlighting the roles of ion aggregation and the local electrostatic potential.