Structure and Properties of Complex Coacervate Core Micelles

Complex coacervation is a liquid-liquid phase separation when two oppositely charged polyelectrolytes are mixed in an aqueous solution. Because of low interfacial tension and hydrophilicity, complex coacervate have been applied to the field of pharmacy and food industry. Complex coacervate core micelles (C3M) are formed by simple mixing of AB and A’B diblock copolyelectrolyte solutions in an aqueous solvent where A and A’ are oppositely charged blocks, and B is neutral and hydrophilic block (e.g., PEO). In this study, we investigate the structure of C3M as a function of molecular weight of charged block, pH, and salt concentration by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). Since the charged moieties are introduced by post modification of mother block copolymers, the charge imbalance issue can be neglected. The results reveal that the relatively monodisperse C3Ms are formed by simple mixing, and overall micelle size and core radii reduce as salt concentration increases, and followed by disappearance of C3Ms above a critical salt concentration. In particular, we observed the scaling relationship between core dimension and molecular weight of charged block, which is analogous to traditional block copolymer micelles.