Interfacial Properties of Polyelectrolyte Coacervates

Under favorable conditions, mixing aqueous solutions of cationic and anionic polymers can lead to a type of liquid-liquid phase separation known as coacervation, where one phase is rich in polymers (coacervate). These coacervates have a wide range of applications, including as underwater adhesives, in food processing, drug delivery, or advanced coatings. The key to understanding the formation of coacervates and fine-tuning their performance is to develop a model of their interfacial properties, capable of describing the width of the interface, ion distributions, and polymer concentration gradients. We have developed such a model by combining the Cahn-Hilliard theory with the modified Debye-Hueckel treatment on electrostatic interactions. We investigated the coacervation phase diagram, interfacial density profile, and ion distribution, by comparing the predictions of our model with results from direct molecular simulations. We further investigated the effects of dielectric inhomogeneity and chain connectivity.