Dynamics and Rheology of THF Swollen Ionic Polymer Melts: Molecular Dynamics Simulation Study

The macroscopic dynamics of ionic polymers are often constrained by the formation of ionic clusters. Traces of solvents however affect the structure, dynamics and viscoelastic response of these melts. Here, we probe the effects of THF on the dynamics of polystyrene sulfonate (PSS) melts by fully atomistic molecular dynamics simulations. We hypothesize that THF penetrates both hydrophilic and hydrophobic domains, affecting their interrelation. Melts swollen with THF as the sulfonation fraction is varied were studied. We find that with the addition of THF the average cluster size decreases. The number of THF molecules associated with ionic groups increases with increasing sulfonation fraction f. Shear measurements show that the addition of small amounts of THF decreases the viscosity dramatically. Correlations of the dynamics of swollen melts on different time and length scales as determined by MSD and S(q, t) with the rheology studies will be discussed.