(523e) 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. In this work, we present a new simulation strategy to study complex coacervation in polymeric solutions 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 all-atom simulations, but its predictive capability is limited by the need to specify emergent (e.g. chi) parameters. Using poly(acrylic acid) and poly(allylamine) aqueous mixture as a model polyelectrolyte coacervate forming system, we show an original way to use small-scale, atomistic simulations to parameterize statistical field theory models. Specifically, parameters for the field theory are derived from a systematic coarse-graining of representative all-atom simulations, using a strategy based on the so-called relative entropy. The capability of this approach is demonstrated by the prediction of the dependence of coacervation on important solution variables such as added salt and polymer composition. This synergistic approach opens the door to systematic design of a wide variety of polymeric formulations via simulations.