Phase Behavior of Lecithin at the Oil/Water Interface

Abstract

In order to elucidate the mechanism for the formation of an interfacial film providing enhanced emulsion stability by lecithin, we performed dynamic contacting experiments in which water was brought into contact with a solution of the phospholipid in n-decane. Two main phenomena were observed in the vicinity of the interfacial boundary on the side of the nonaqueous phase. The first to be noted was the formation of a thick interfacial film, visible even to the naked eye. The second was the separation of a liquid phase. On the basis of the combined data from our current and previous experiments, we suggest the mechanism for interfacial processes of which the basis is the lecithin organogel formation. Water transferring from aqueous solution into the nonpolar phase through a hydration of the adsorbed phospholipid promotes a sequence of phase or pseudophase transitions near the phase boundary between immiscible liquids: spherical reverse micelles → three-dimensional network from entangled wormlike micelles → organogel separation into a diluted solution and a compact gel or solid mass precipitating on the interfacial boundary.