Small Ion Effects on Self-Coacervation Phenomena in Block Polyampholytes

Polyelectrolyte complexation is a common phenomenon in natural polymers and has been applied to synthetic materials systems for coatings, adhesives, and encapsulants. Single-component polyelectrolyte complexes are formed when block polyampholytes exhibit self-coacervation, phase separating into a dense liquid coacervate phase rich in the polaympholyte coexisting with a dilute supernatant phase. Using fully fluctuating field theoretic simulations, we explore the phase behavior of block polyampholytes in solution to understand the structure and thermodynamics of the self-coacervate. Results are shown concerning the effects of counterions, added salt, and charge asymmetries. In particular, non-neutral chains are considered, probing the crossover at which electrostatic repulsions dominate the attractions, resulting in suppressed phase separation. Simple analytical and random phase approximation (RPA) expressions are used to discuss scaling relationships.