Effect of Charge Patterning and Polymer Architecture on Polypeptide-Based Coacervates

Complex coacervation is an associative, electrostatically-driven liquid-liquid phase separation that occurs when aqueous solutions of oppositely-charged polyelectrolytes are mixed. The dense, polymer-rich coacervate phase finds application in many fields, such as cosmetics, processed food and microencapsulation for drug and gene delivery. These materials are affected by many factors such as the polycation/polyanion ratio, total polymer concentration, pH, temperature, and pattern of charges present. Among these factors, the effect of charge patterning has been rarely studied, due to the difficulty of synthesizing polyelectrolytes with equal chain length and charge density, but different distributions of charge or other functionalities. However, polypeptides represent a model platform for the synthesis and study of polyelectrolytes with precisely controlled sequence patterning at the molecular level. We examine the effect of charge density, charge patterning, and polymer architecture on the stability and overall material properties of complex coacervates formed from positively- and negatively-charged polypeptides with matched and mismatched sequences of charged residues. This systematic investigation of the effects of charge patterning will help to elucidate design rules to facilitate the tailored creation of complex coacervate-based materials with defined properties for a wide range of applications.