Langmuir, Vol.19, No.24, 10061-10072, 2003
Nonequilibrium behavior in the three-component system stearic acid-sodium stearate-water
The state behavior of stearic acid-sodium stearate-water, which provides a model of a fatty acid structuring mechanism, was studied by differential scanning calorimetry (DSC), optical microscopy, and X-ray scattering. DSC mapped the state diagram of aged and quenched samples as a function of temperature. Optical microscopy identified a liquid crystal transition. Simultaneous small- and wide-angle X-ray scattering identified the structures present within different regions of the state diagram. Two acid/soaps differing in melting temperature, unit cell, lamellar spacing, and acid to soap chain ratio existed at room temperature. In half-neutralized samples, a lamellar hydrated gel phase with an hexagonal unit cell persisted to room temperature on quenching. Nonequilibrium behavior persisted to different degrees depending on the extent of neutralization of the system.