Phase Behavior and Interfacial Tension of Polyelectrolyte Complex Coacervates

Complex coacervation occurs when a solution of anionic and cationic polyelectrolytes undergoes liquid-liquid phase separation under suitable conditions. The viscoelastic polymer-rich phase (coacervate) exhibits a low interfacial tension with the polymer-poor supernatant. This tunable phase behavior, under different physicochemical conditions, enables the applications of coacervates as encapsulation media and spreadable wet adhesives, for example. This presentation describes an experimental measurement method of the ultralow interfacial tension by combining thermal-induced microphase separation and droplet-retraction analysis. The effect of salt concentration, temperature and molecular mass on the interfacial tension will be discussed and compared to available mean field theory predictions.