Properties of microemulsions based on mixed nonionic surfactants and mixed oils

The systems studied were water/sucrose laurate/ethoxylated mono-di-glyceride/isopropylmyristate/peppermint oil. The solubilization capacity of water in the oils is dependent on the surfactants and oils mixing ratios (w/w). The transport properties (electrical conductivity and dynamic viscosity) were studied as function of water volume fraction. Electric percolation phenomenon was observed in these systems and the water volume fraction percolation thresholds were determined. The diffusion properties investigated by nuclear magnetic resonance confirm a progressive transformation of the water-in-oil to bicontinuous and inversion to oil-in-water microemulsions that occur upon dilution with water. The diffusion coefficients of surfactants increase with the increase in the water volume fraction. The structural parameters studied by small angle X-ray scattering that include the periodicity and correlation length were estimated. The periodicity increases linearly with the increase in the water volume fraction whereas the correlation length increases with the increase in the water volume fraction to a certain value then decreases. Cryogenic transmission electron microscopy images for diluted microemulsions revealed the presence of spheroidal droplets of up to 10 nm diameter.