(59c) Dynamics of Entangled Liquid Coacervates Made from Oppositely Charged Polyelectrolytes

Mixtures of oppositely charged polyelectrolytes can phase separate to form a polymer rich phase, called a coacervate, and a polymer depleted supernatant. Much effort has been devoted to understanding the charge driven phase separation of coacervates made from oppositely charged polyelectrolytes, leading to models that are able to predict the coacervate phase diagram and the structure of the coacervate phase. However, few studies have considered the dynamic properties of coacervates and how these depend on experimentally controllable parameters. We develop a scaling theory to predict the dynamic behavior of entangled charge asymmetric liquid coacervates made from oppositely charged polyelectrolyte solutions. Here, charge asymmetry results from making a coacervate with polyanions and polycations that have a different number of charges along their backbones. Polyelectrolytes with high enough molecular weights give raise to topological constraints known as entanglements which, in the coacervate, can arise due to either the polyanion, the polycation or both. We model these entanglements utilizing reptation theory, where entanglements are coarse-grained by considering polymer chains to be confined inside a tube in which they must undergo reptating motion to diffuse and relax. We develop a scaling theory that predicts the diffusion of the polyelectrolytes in and the shear viscosity of entangled asymmetric coacervates. The theory demonstrates how the dynamic properties of entangled coacervates can be modified with experimentally controllable parameters such as the degree of polymerization, polymer concentration in the coacervate phase and the number density of charges of the polyanion and polycation. This provides a means with which to design and tune the viscoelastic properties of entangled asymmetric coacervates for a wide variety of applications.