Linear Viscoelasticity and Time–Alcohol Superposition of Chitosan/Hyaluronic Acid Complex Coacervates

Complex coacervation is an associative liquid–liquid phase separation phenomenon resulting from the complexation of oppositely charged macroions. While it is well-known that the phase behavior and rheological character of the resulting coacervates can vary as a function of the identity of the various species present (i.e., macroions, salt, and solution conditions), the effect of solvent quality has been rarely studied. Here, the effect of adding small amounts of either methanol or ethanol to complex coacervates of the natural polymers chitosan and hyaluronic acid is described. The effect of cosolvent addition on the phase behavior and linear viscoelasticity of the resulting coacervates is characterized. Lastly, we explore the potential for using not only time–salt superposition but also time–alcohol and time–salt–alcohol superposition to provide insight into coacervate rheology.