Nano-emulsions preparation by low energy methods in an ionic surfactant system

The emulsion inversion point method was used to form nano-emulsions in the ionic system water/oleic acid-potassium oleate-C(12)E(10)/hexadecane. Potassium hydroxide solutions were added to oleic acid-C(12)E(10)/hexadecane solutions at constant temperature (25 degrees C) in order to obtain nano-emulsions at 80% water concentration, with a stoichiometric relation of oleic acid and KOH at this point. So, the ionic surfactant (the potassium oleate) was formed along the emulsification path. The influence of the phases present during the emulsification process on nano-emulsion droplet size was analized. The results show that the smallest droplet size is obtained when along the emulsification path and near the nano-emulsion region the equilibrium is achieved with all the oil dissolved in a phase, in this case in a cubic liquid crystalline phase. It has also been found that the most probable breakdown mechanism of the nano-emulsions formed is Ostwald Ripening. (c) 2006 Elsevier B.V. All rights reserved.