(187ad) Using a Stochastic Kinetic Theory to Study Charged Polyelectrolytes

The behavior and properties of systems containing multiple charged species at high concentrations are affected by correlations arising from the interplay between long-ranged electrostatic interactions, other interactions (such as excluded volume), fluctuations and motions of the species. This is important for systems such as colloidal suspensions, electrolytes, charged polymers, and proteins, where the collective interactions and motions can lead to phenomena such as phase separation.

The high concentrations motivate using a field-based approach, but traditional models of electrostatic interactions may not accurately capture ion-ion correlations or fluctuations or may not be applicable in non-equilibrium situations such as flow. We present the results of applying a stochastic kinetic theory (also called stochastic density functional theory) approach to charged systems, which is inherently applicable to non-equilibrium situations and can capture fluctuations and correlations in the system. It is a coarse-grained field-based approach where the species are tracked using equations describing their number density. Electrostatic interactions are treated using the Poisson equation. This approach is also capable of capturing phenomena such as underscreening that occur at high electrolyte concentrations.

We show how simulations using this approach can be used to study phase separation based on the underlying interactions and provide insight on its mechanism.