Explicit Polarization in Coarse-Grained Simulations of Ionomer Melts

Abstract

The structure and morphology of ionic aggregates in ionomer melts significantly influence their ion transport properties. Understanding the underlying mechanisms and relevant time scales of ion transport can facilitate design of viable ionomer materials as single-ion conductors for energy applications. Previous studies have characterized the ionic aggregate structure, morphology, and dynamics using non-polarizable coarse-grained molecular dynamics (CGMD) simulations. In this work, we examine the role of polarization in ionomer melts by explicitly incorporating Drude oscillators in CGMD simulations. We systematically study the structure and dynamics of pendant ionomers, focusing on the comparison to non-polarizable systems. Polarization within the ion clusters leads to less overall ion structuring. On the aggregate scale, less ion structuring yields smaller ionic aggregates. The extent to which the clusters are smaller delicately depends on the strength of the electrostatic interactions (the dielectric constant). Under certain conditions, we find that the time scale for free counterion diffusion does not depend on the morphology, unlike that in a non-polarizable model.