Dynamics of liquid coacervates: Higher charged density polyelectrolytes are in entangled semiflexible regime

Solutions made from oppositely charged polyelectrolytes can phase separate to form a polymer-rich coacervate phase, important in biology and technological applications. In coacervates made from polyelectrolytes of high enough molecular weights, topological constraints known as entanglements alter the dynamic properties and can be due to either the polyanion, the polycation or both. In entangled charge density asymmetric coacervates, the high charge density polymer has an electrostatic persistence length that can be smaller or larger than the diameter of a confining tube by low charge density polymers. Here, we consider the case in which the electrostatic persistence length of the high charge density polymer is larger than the diameter of a confining tube by low charge density polymers. On length scales smaller than the tube diameter, high charge density polymers have a higher effective friction than in pure solutions, owing to a dynamic coupling between the polymers even in the unentangled regime. On length scales larger than the tube diameter, the high charge density polymer behaves similar to entangled semiflexible polymers. The effect of the higher effective friction and “semiflexible” dynamics on rheological properties and polymer diffusion will be discussed.