Nonequilibrium Molecular Dynamics of Flowing Complex Coacervates

Molecular simulations are applied to model the nonequilibrium dynamics of concentrated complex coacervates during nonlinear processing flows. We equilibrate bead-spring model coacervate phases with varying concentrations of polymer, salt, and neutral solvent and characterize their equilibrium structure and viscoelasticity. Coacervates undergo nonlinear simple shear flows for shear strain rates spanning from linear response to highly nonlinear flow. Systems display Rouse-like stress relaxation in linear response, and power-law shear thinning of the viscosity with increasing strain rate. We characterize how these rate-dependent trends depend on salt and solvent concentration, and temperature as coacervates are cooled toward glassy states. The nonequilibrium dynamics of chains are characterized and related to the macroscopic shear stress and viscosity.