Effect of Cluster Cohesion on Dynamics of Ionic Polymers in Solutions: MD Simulations Studies*

Correlation of dynamics of ionizable macromolecules with the cohesion of ionic clusters is critical to understanding their properties; hence directly impacting their potential uses. Here we probe the immense effects that even a small number of ionic groups tethered to a polymer have on their dynamics, through atomistic molecular dynamics simulations. Clusters shape and size were tuned via addition of ethanol to toluene solutions of sulfonated polystyrene in the ionomer regime. The static and dynamic structure factors were measured and corelated with the characteristics of the ionic clusters. We find that the dynamics of the polymer that is constrained on the length scale of the ionic cluster in toluene is enhanced as tiny quantities of ethanol are added. While the size of the clusters is only slightly altered, the degree of association of the solvents with the ionic groups changes with addition of ethanol affecting their internal packing and ultimately their macroscopic dynamics.