AN INVESTIGATION INTO THE MECHANISMS OF SELF-EMULSIFICATION USING PARTICLE-SIZE ANALYSIS AND LOW-FREQUENCY DIELECTRIC-SPECTROSCOPY

A series of mixtures comprising Imwitor 742 and Tween 80 have been pre pared and their self-emulsifying properties studied using a method of visual examination. The particle size distributions of emulsions prepa red from these mixtures at 25 degrees C, 37 degrees C in water and 37 degrees C in 0.1 M HCl have been measured. A marked decrease in mean p article size was observed for 30 and 40% Imwitor 742/Tween 80 mixtures at 25 degrees C with a decrease in particle size also being noted for the majority of Imwitor 742/Tween 80 compositions at higher temperatu res. Low frequency dielectric spectroscopy was performed on the pure c omponents and on binary systems to which water had been added to make 50% v/v mixtures. Evidence was shown for the formation of liquid cryst alline phases at concentrations corresponding to those shown to be eff icient self-emulsifying systems. The study therefore suggests that sel f-emulsification may be associated with liquid crystal formation and t hat low frequency dielectric spectroscopy may be of considerable use i n understanding the factors leading to self-emulsification.