Molecular Dynamics Simulations of Patterned Complex Coacervates

Complex coacervation is the liquid-liquid phase separation of polyelectrolytes in aqueous salt solution into a polymer-dense phase (coacervate), and a polymer-dilute phase (supernatant). These materials are simplified analogues of membraneless compartments in cells, where the sequence of charge has been shown to alter resistance to the presence of salt. Previous work using Monte Carlo simulations demonstrated that changing the sequence of charged and neutral monomers while keeping the charge fraction constant alters the extent of phase separation. We have run molecular dynamics simulations to elucidate the interplay between charge fraction and charge sequence, showing comparisons to existing Monte Carlo simulations and experimental data demonstrating that charge blockiness enhances phase separation. This model is then used to demonstrate the structural effects of varying the charge fraction, in particular showing the emergence of microphase separation at low salt concentrations for blocky polyelectrolytes.