Effect of Side Chain Length in Polymer Single-Ion Conductors

Strategies for improving conductivity in polymer single-ion conductors typically focus on increasing polymer segmental motion and encouraging greater ion dissociation. Strong ionic aggregation reduces the polymer segmental motion and can negatively impact ion dynamics. One approach to lowering the glass transition temperature and increasing segmental motion is to increase the length of the side chains. In this work, we present molecular dynamics simulations of polymer single-ion conductors using bead-spring models with ions bound at the end of side chains of varying lengths. We focus on the effect of chain architecture on ionic aggregation in model polymers with short and long side chains at equal ion contents. In systems with longer side chains, we find that ions aggregate more readily due to the increased conformational flexibility of the fixed ions. Additionally, the extent of aggregation and size of aggregates are reduced significantly when the strength of ionic interactions is reduced in systems with either short or long side chains. We discuss the impact of these factors on ion dynamics.