Cluster Cohesion of Ionomer Regime Swollen Melts

Structure and dynamics of polymer melts in the ionomer regimes are affected by the backbone as well as the ionizable groups. On the path to understanding the immense effect a small number of ionizable groups have on polymer dynamics, the current study probes lightly sulfonated polystyrene melts swollen with THF, using molecular dynamics simulations. Though THF is a polar solvent and interacts predominantly with the ionic clusters, it has limited effects on the backbone conformations which allows the study of the cohesion of the ionic clusters on the polymer structure and dynamics. Cluster characteristics including shape, size and internal dynamic were calculated and correlated with the polymer structure and dynamics as expressed in the static, S(q), and dynamic, S(q,t), structure factors, and mean square displacement (MSD). Surprisingly with increasing THF fraction, larger clusters are formed, suggesting that the solvent releases constraints that allow assembly into larger ionic domains. The cluster boundaries become significantly more defined. In contrast to PSS in toluene, even though the average clusters are larger, segmental dynamics increases. The interrelation between the cluster properties and dynamics will be discussed.