Ultralow interfacial tension of polyelectrolyte coacervates using drop retraction method

The interfacial tension of coacervates can be controlled by a number of physicochemical conditions, such as salt type and concentration, temperature, and polymer molecular mass. An improved understanding of these relationships will help advance applications such as polymer coatings, encapsulation media and wet adhesives. However, interfacial tension measurements are challenging due to the ultra-low magnitudes observed in polyelectrolyte coacervates. This presentation describes the use of shape retraction analysis of a deformed drop of dilute phase generated in situ in the coacervate. Our measurements confirm that the interfacial tension follows the mean field prediction of 3/2 scaling as a function of the difference between salt concentration and the critical salt concentration at which interfacial tension vanishes. The additional effects of temperatures and molecular mass will be described.