Stratification in emulsion films

Abstract Formation of films possessing a layered or stratified structure has been observed with foam films from liquid crystals, from concentrated surfactant solutions and in liquid layers on the surface of water. The stratifying films have a structure similar to that of the smectic phase which soaps are known to form in the bulk solution at high concentrations. The repeating units of which such films are built are the so-called black films: each unit consists of two surfactant layers interleaved by a thin aqueous core. In the study presented here we have observed that stratification can also take place in emulsion films from concentrated aqueous surfactant solutions. We have compared these results with those obtained for foam films using the same surfactant, i.e. sodium dodecylsulfate.