Charge Asymmetry Suppresses Coarsening Dynamics in Polyelectrolyte Complex Coacervation

Mixing solutions of oppositely charged macromolecules can result in liquid-liquid phase separation into a polymer-rich coacervate phase and a polymer-poor supernatant phase. Here we show that charge asymmetry in the constituent polymers can slow down the coarsening dynamics, with an apparent growth exponent that deviates from the well-known 1/3 for neutral systems and decreases with increasing degrees of charge asymmetry. Decreasing solvent quality accelerates the coarsening dynamics for asymmetric mixtures, but slows down the coarsening dynamics for symmetric mixtures. We rationalize these results by examining the interaction potential between merging droplets.