Properties of microemulsions with mixed nonionic surfactants and citrus oil

Water/propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/citrus oil microemulsion systems were formulated and characterized using electrical conductivity, dynamic light scattering, and small angle X-ray scattering. The solubilization capacity of water in the oil is dependent on the surfactants mixing ratio (w/w). The free energy of solubilization (ΔGso) for water-in-oil microemulsions were calculated and found to decrease with water content in the water-in-oil microemulsions region and increase in the oil-in-water region, ΔGso decreased with increasing ethoxylated mono-di-glyceride content in the mixed surfactants. Static percolation phenomena were observed in these systems, and the water volume fraction percolation threshold was determined. The activation energy of conductive flow depends on the surfactants mixing ratio. The hydrodynamic diameter of the diluted microemulsions decreases with the increase in temperature. The periodicity and the correlation length those are characteristic lengths for the domain size of the microemulsions increase with the increase in the aqueous phase content.