Effect of ethanol on monoglyceride monolayers at the air‐aqueous phase interface

Abstract

AbstractWe have studied the behavior of monopalmitin and monoolein monolayers, spread at the air‐aqueous phase interface, as a function of temperature and surface pressure. The subphases were aqueous ethanol solutions at 0.5 and 1 mol/L. The structural characteristics of these films at interface were deduced from the π‐A isotherms, as measured with an automated Langmuir‐type film balance. The monolayer structure and stability were functions of hydrocarbon chain length and the presence of a double bond. Generally, the factors that decreased monolayer stability produced transformations toward configurations with more expanded structures. Changes in the subphase composition had a direct influence on the monolayer molecular structure. This study showed the existence of interactions between film and ethanol molecules at the interface. As a consequence of these interactions, a contraction in the monolayer structure was observed. The magnitude of interactions between monoglyceride and ethanol molecules at the interface depends on the surface pressure, temperature, and surface composition. Stronger film‐substrate interactions produced changes in monolayer stability. Relationships between film elasticity and structural characteristics are also discussed.