Surface Films of Soybean Lecithin II: Interactions Between Lecithin and Lipid Substances in Mixed Monomolecular Films

Abstract

Mixed films of lecithin with the fatty acids (stearic, elaidic, and oleic) as well as with the glycerol esters of mono-, di-, and triglyceride have been investigated. Evaluation of these systems has been made utilizing two properties of surface films, their mean molecular areas and their collapse points. It would appear from this investigation that in mixed film systems, lecithin—stearic acid and lecithin—monoglyceride are miscible, but without a significant degree of interaction and as such, form ideal two-dimensional liquids. Lecithin—oleic and lecithin—elaidic acids have been shown to be miscible in mixed film systems but with a significan degree of interaction so that they may be considered to be nonideal two-dimensional liquids. The data for the lecithin—di- and triglyceride systems did not conclusively show whether these systems were ideal or nonideal two-dimensional liquids in mixed surface films. Mixed films of lecithin with the fatty acids (stearic, elaidic, and oleic) as well as with the glycerol esters of mono-, di-, and triglyceride have been investigated. Evaluation of these systems has been made utilizing two properties of surface films, their mean molecular areas and their collapse points. It would appear from this investigation that in mixed film systems, lecithin—stearic acid and lecithin—monoglyceride are miscible, but without a significant degree of interaction and as such, form ideal two-dimensional liquids. Lecithin—oleic and lecithin—elaidic acids have been shown to be miscible in mixed film systems but with a significan degree of interaction so that they may be considered to be nonideal two-dimensional liquids. The data for the lecithin—di- and triglyceride systems did not conclusively show whether these systems were ideal or nonideal two-dimensional liquids in mixed surface films.