Role of Surface Electrostatics in Particle-Polyelectrolyte Complex Coacervates

Particle-polyelectrolyte (PE) complex coacervation is a liquid-liquid phase separation that occurs when polyelectrolytes undergo associative phase separation with an oppositely charged non-polymeric species, such as surfactant micelles, colloids, and proteins. While this phenomenon has been extensively studied due to its benefits in biological and industrial applications, the molecular understanding of particle-PE coacervation remains limited to low-linear charge density systems. In previous studies using a hybrid Monte Carlo and Self-Consistent Field Theory (MC-SCFT) approach developed in our group, correlation attractions between two charged micelles in the presence of polyelectrolytes are necessary for phase separation to occur. Thus, we further investigate these correlation attractions by exploring different particle-PE systems that can lead to complex coacervation.

In this work, we study how micelle surface charge density, polyelectrolyte sequence, and salt concentration affect correlation attractions necessary for particle-PE coacervation. By employing thermodynamic integration and the potential of mean force for Brownian Dynamic simulations, two-dimensional energy landscapes of interacting surfaces were obtained. Initial result shows that these inter-particle electrostatic interactions are short-range and directly related to the local charge environments, and by modifying properties such as the polymer charge sequence and surface charge density, a variety of local charge environments can be observed. The results of this project will be integrated into our MC-SCFT model to provide a better molecular understanding of particle-PE coacervation thermodynamics.