Effect of the dispersion behavior of a nonionic surfactant on surface activity and emulsion stability

Using a nonionic. surfactant decaglycerol mono-oleate (MO750), long-term st able ethanol-in-oil (E/O) emulsions were prepared. The Bancroft rule was no t applicable to the preparation of E/O emulsion systems. The surface-active performance of MO750 in water differed from that in commercial 95% ethanol and oil. The critical micelle concentration of MO750 could not be measured in 95% ethanol and oil, suggesting that the solvent used greatly affects t he surface activity of MO750. The experimental results indicated that MO750 does not significantly reduce the interfacial tension of the 95% ethanol/o il interface, but plays an important role in stabilizing the E/O emulsion. The dispersion behavior of MO750 in 95% ethanol and in oil was investigated with small-angle X-ray scattering. The surfactant was found to exist in a spherical structure with a radius of gyration of about 7 Angstrom in 95% et hanol, and it formed aggregates with a radius of gyration of about 90 Angst rom in oil. A possible stabilization mechanism is presented based on the st ratification theory. (C) 2001 Academic Press.