Enhancement of Aqueous Emulsion and Foam Stability with Oppositely Charged Surfactant/Polyelectrolyte Mixed Systems

Abstract : We have studied emulsifying and foaming properties of oppositely charged surfactant/polyelectrolyte mixed systems. We have shown that adding a small amount of oppositely charged polyelectrolyte to a ionic surfactant enhances the stability of emulsion and foams at very low surfactant concentration, typically below the CMC, in a range of concentration where the surfactant alone is usually not efficient for stabilizing macroscopic dispersed systems. This effect is explained by the co-adsorption of polymer and surfactant molecules at the fluid/fluid interface and formation of a highly surface active surfactant-polymer complex. Complexation and therefore emulsion and foam stability can be tuned by adjusting electrostatic attraction between the two charged species. Use of amphoteric polyampholyte can be used as pH switchable system for controling emulsion or foam stability.