The physicochemistry and percolation behavior of microemulsions as a function of chain length of cosurfactant and surfactant

Abstract

This study involved investigating phase behavior and physicochemical characterization of microemulsions (MEs) stabilized by mixtures containing polysorbates (C12-C18) as surfactants and n-alkanols (C2-C6) as cosurfactants. Distribution coefficients and Gibbs free energy were also determined for the systems containing polyoxyethylene sorbitan monolaurate (Tween® 20) as surfactant. ME with Tween® 20 as the surfactant and ethanol as the co surfactant exhibited maximium ME area, as well as, water solubilization capacity (WSC). In the presence of all the cosurfactants, values of both of these parameters decreased as the chain length of the surfactant increased with the exception of Tween® 80. This could be attributed to the unsaturated structure of Tween® 80 which possibly allowed for greater spatial configurations of the chain and thus allowing less oil penetration. Furthermore, the transition of w/o MEs to o/w MEs via a bi-continuous structure along the dilution line was confirmed by conductivity, viscosity and droplet size analysis.