FATTY-ACID BASE INTERACTIONS IN MODEL SYSTEMS - A LANGMUIR FILM, SURFACE-TENSION, AND CALORIMETRIC STUDY

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 .