(59h) Complex Coacervates of Semiflexible Polyanions and Flexible Polycations: Isotropic and Liquid-Crystalline States

Complex coacervation plays an essential role in compartmentalization of the living cells and is important for an understanding of prebiotic evolution. This fuels increasing interest in liquid-liquid phase separation, which takes place in solutions of oppositely charged biopolyelectrolytes, including that containing duplex DNA. High rigidity of double stranded DNA strongly affects the properties of the polymer-rich phase. In our work, we combine scaling concepts, the random phase approximation (RPA), and Onsager approach to nematic ordering of partially flexible polymers to develop a theory of coacervates formed from semiflexible polyanions and flexible polycations. At low stiffness of polyanion, coacervates are isotropic liquids with two different correlation lengths. These lengths are equal to the mesh sizes of polyanion and polycation interpenetrating semidilute solutions. When the polyanion stiffness is above the threshold, coacervate undergoes nematic ordering. Formation of nematic phase is induced by both anisotropic excluded volume and anisotropic Coulomb interactions between semiexible chains. Our theoretical predictions on intra-coacervate liquid crystalline ordring are supported by recent experimental studies.