Wetting, Unbinding, and Ultralow Tensions in Amphiphilic Systems

Abstract

AbstractWetting phenomena in ternary amphiphilic systems is reviewed with a particular emphasis on the effect of fluctuations on the location of the wetting transition, both in balanced and unbalanced systems. A rich prewetting behavior, yet to be observed, is also described. Unbinding transitions of lamellar phases in these systems are related to their wetting counterparts, and the possibility of observing a pre‐unbinding transition is discussed. It is shown that were a complete unbinding of a lamellar phase to occur, the interfacial tension between oil and water phases coexisting with it would be identically zero. It is argued that the origin of the ultralow interfacial tensions in strong amphiphilic systems is the proximity to such an unbinding transition, one which is prevented by van der Waals forces. A consequence of this assumption is that the interfacial tension between oil and water phases coexisting with a structured phase of given wavelength should vary as the inverse square of that wavelength, a result confirmed by experiments on microemulsions.