Shear Response of THF Swollen Ionic Polymer Melts: Molecular Dynamics Simulations Study*

Ionizable groups determine the behavior of polymers through long range electrostatic interactions that drive assembly and affect the inherent dynamics of the macromolecules and their mechanical response. Here, using molecular dynamics simulations we probe the effects of ionic assemblies on the inherent dynamics and shear response of polystyrene sulfonate melts in the ionomer and polyelectrolyte regimes as small amounts of THF are added to modify the cohesion of the ionic assemblies. We find that the shear viscosity is higher for the polyelectrolyte regime compared with ionomer one, due to large continuous ionic assemblies in polyelectrolytes. With increasing shear rates, the assemblies break up in both regimes, reducing the shear viscosity. THF that resides predominantly along the ionic assemblies reduces only slightly the shear viscosity. Molecular understanding that underline the shear response will be discussed.