Phase Behavior and Salt Partitioning in Polyelectrolyte Complex Coacervates

Abstract

Polyelectrolyte complexes are omnipresent both in nature and in the technological world, including nucleotide condensates, biological marine adhesives, food stabilizers, encapsulants, and carriers for gene therapy. However, the true phase behavior of complexes, resulting from associative phase separation of oppositely charged polyelectrolytes, remains poorly understood. Here, we rely on complementary experimental and simulation approaches to create a complete quantitative description of the phase behavior of polyelectrolyte complexes that represents a significant advance in our understanding of the underlying physics of polyelectrolyte complexation. Experiments employing multiple approaches with model polyelectrolytes—oppositely charged polypeptides poly(l-lysine) and poly(d,l-glutamic acid) of matched chain lengths—led to phase diagrams with compositions of the complex and the supernatant that were in excellent agreement with simulation results. Contrary to the widely accepted theory for complexation, we...