Jmr. Patino et al., Structural-dilatational characteristics relationships of monoglyceride monolayers at the air-water interface, LANGMUIR, 17(13), 2001, pp. 4003-4013
We have studied the effect of monolayer structure on dilational characteris
tics (surface dilatational modulus and its elastic and viscous components)
of monoglyceride monolayers (monoolein and monopalmitin) spread on the air-
water interface, at 20 degreesC and at pH 5 and 7. The stress response to c
ompression-expansion sinusoidal deformation of the interface in a modified
Wilhelmy-type trough with two oscillating barriers was measured as a functi
on of deformation amplitude (within the range of 1-20% of the initial area)
, frequency (within the range of 1-300 mHz), and superficial density (withi
n the range of 1-3.5 mg/m(2)). The same experimental device coupled with Br
ewster angle microscopy makes it possible to determine the structure and mo
rphology of the monolayer. The monolayer structure and, especially, the con
ditions at which the monolayer collapses determine the viscoelastic behavio
r of the monolayer and the linear response of the stress to area deformatio
n. The nonlinear viscoelastic behavior of the interface has been associated
with the monoglyceride monolayer collapse. It was found that the dilatatio
nal modulus is not only determined by the interactions between spread molec
ules (which depend on the surface density) but that the structure of the sp
read monolayer also plays an important role.