Predicting polyelectrolyte complex coacervation from a molecularly-informed field-theoretic simulation approach

Understanding the phase behavior of polyelectrolyte coacervation is crucial for many applications, including a range of consumer products. However, in most cases, modeling coacervation is not easily accessible by molecular simulation methods due to the long-range nature of electrostatic forces and the typical high molecular weights of the species involved. We present a new simulation strategy to study complex coacervation leveraging the strengths of both particle and polymer field-theoretic simulations. Field theory is uniquely suited to capture larger length scales that are inaccessible to particle simulations, but its predictive capability is limited by the need to specify emergent (e.g. χ) parameters. Using model coacervate forming systems consisting of polyelectrolytes and/or surfactants, we show an original way to use small-scale, atomistic simulations to parameterize field theory models via the relative entropy coarse-graining approach. The capability of this approach is demonstrated by the prediction of the dependence of coacervation on important solution variables such as added salt and charged group composition. This synergistic approach opens the door to systematic design of a wide variety of polymeric formulations via simulations.