H. Ebeltoft et al., FATTY-ACID BASE INTERACTIONS IN MODEL SYSTEMS - A LANGMUIR FILM, SURFACE-TENSION, AND CALORIMETRIC STUDY, Langmuir, 10(7), 1994, pp. 2262-2266
Acid/base interactions have been studied by means of surface tension,
calorimetric measurements, and Langmuir films. When a fatty amine is c
ombined with hexanoic acid, the surface activity of the corresponding
complex is increased as the base is shifted from butylamine to octylam
ine. The complexation in the pure system hexylamine/hexanoic acid is a
ccompanied by an exothermic enthalpy change of -45 kJ/mol. The Langmui
r study reveals that complexes of butylamine/hexylamine and stearic ac
id are water soluble, while octylamine was incorporated into the monol
ayer of stearic acid. Monolayers of arachidic acid took up butyl- and
hexylamine with retained stability. When combined with octylamine, the
arachidic acid monolayers became unstable due to nucleation processes
.