Mr. Dominguez et Jmr. Patino, Effect of ethanol on monoglyceride monolayers at the air-aqueous phase interface, J AM OIL CH, 76(9), 1999, pp. 1041-1046
We have studied the behavior of monopalmitin and monoolein monolayers, spre
ad at the air-aqueous phase interface, as a function of temperature and sur
face pressure. The subphases were aqueous ethanol solutions at 0.5 and 1 mo
l/L. The structural characteristics of these films at interface were deduce
d from the pi-A isotherms, as measured with an automated Langmuir-type film
balance. The monolayer structure and stability were functions of hydrocarb
on chain length and the presence of a double bond. Generally, the factors t
hat decreased monolayer stability produced transformations toward configura
tions with more expanded structures. Changes in the subphase composition ha
d a direct influence on the monolayer molecular structure. This study showe
d the existence of interactions between film and ethanol molecules at the i
nterface. As a consequence of these interactions, a contraction in the mono
layer structure was observed. The magnitude of interactions between monogly
ceride and ethanol molecules at the interface depends on the surface pressu
re, temperature, and surface composition. Stronger film-substrate interacti
ons produced changes in monolayer stability. Relationships between film ela
sticity and structural characteristics are also discussed.