Associative Phase Separation in Polyelectrolyte Complex Coacervates

Measurements on a common aqueous oppositely-charged polyelectrolyte complex, potassium-poly(styrene sulfonate) and poly(diallyl dimethyl ammonium bromide), shows liquid-liquid phase separation upon heating, or lower critical solution temperature behavior. The experimental accessibility of the apparent critical temperatures occurs for a narrow range of monovalent KBr salt concentration. We will show new static and dynamic light scattering and small-angle neutron scattering results and discuss how the correlation length, osmotic compressibility estimates from the scattered intensity to zero angle, and relaxation times change as the coexistence curve is approached by increasing temperature. The measurements of the binodal and spinodal curves from these polyelectrolyte solutions with chain association are compared to available models.