Effect of ionic and nonionic surfactants on the phase behaviour and physicochemical characteristics of pseudoternary systems involving polyoxyethylene(20) sorbitan monooleate

This study undertakes to construct the phase diagrams of pseudo-ternary systems of single and mixed surfactants involving polyoxyethylene(20) sorbitan monooleate(Tween-80). The mixed surfactant systems was achieved by adding Tween-80 to cetyltrimethylammonium bromide, sodium dodecyl sulphate or nonionic surfactant, polyoxyethylene(20) sorbitan monolaurate in the ratio 90:10. The sub-regions of both single and mixed microemulsions were identified by visual titration technique and the areas of the domains were demarcated with the help of electrical conductivity data. The physicochemical properties data such as density, electrical conductivity, cloud point, viscosity, size and zeta potential of the mixed systems were found to be significantly different from that of the single system. The percolation transition was evident from the conductivity data. The micropolarities of the o/w sub-region of both single and mixed microemulsions, as determined from pyrene fluorescence were found to be less polar than aqueous micelles. From the DLS studies the microdroplets involving ionic surfactants were found to be smaller in size due to the electrostatic repulsions. Thus, from the understanding of overall phase control, size and micropolarity of the microemulsions, the mixed microemulsion involving ionic-nonionic surfactant mixtures may find application as potential drug delivery systems.