Structure formation in polyelectrolyte coacervates

Measurements on mixtures of oppositely-charged polyelectrolytes 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 critical temperature occurs for a narrow range of monovalent salt and outlines a temperature, salt concentration and polymer concentration coexistence surface.  We show how associative behavior within the homogeneous phase enhances the concentration fluctuations upon approach to the phase boundary.  The properties of the ensuing coacervate phase (droplet morphology, interfacial tension) will be discussed in the context of the phase diagram and the kinetics of phase separation.