Triacylglycerol microemulsions stabilized by alkyl ethoxylate surfactants--a basic study. Phase behavior, interfacial tension and microstructure

As triacylglycerols are the main components of natural fats and oils their solubilization in the form of emulsions or microemulsions was of great interest within the last years. However, systematic studies of their properties along the classical lines of complex fluids science are still missing. In the present paper we focus on the phase behavior, the interfacial tension and the microstructure of systems of type H(2)O/NaCl-triacylglycerol-alkylpolyglycolether (C(i)E(j)). The interfacial tension between water and oil sigma(ab) is high in a microemulsion system containing triolein. Thus, one needs high surfactant mass fractions to formulate a single-phase microemulsion. We show that this is not only true for triolein, but also for saturated long-chained triacylglycerols. The determination of the amphiphilicity factor f(a) and the calculation of the bending rigidities of the amphiphilic film confirm that despite the fact that high surfactant mass fractions and high temperatures are needed to solubilize triolein in a system of type H(2)O/NaCl-triacylglycerol-alkylpolyglycolether (C(i)E(j)), this is still a microemulsion in the narrower sense.