Physicochemistry and Percolation behavior of Microemulsions as a Function of Chain Length of Cosurfactant and Surfactant

The study involved investigations on phase behavior and physicochemical characterization of microemulsions (MEs) stabilized by mixture containing polysorbates (C12-C18) as surfactants and n-alkanols (C2-C6) as cosurfactant. Distribution coefficient and Gibbs free energy were also determined for systems containing Tween 20 as surfactant. ME having Tween 20 as surfactant and ethanol as cosurfactant was found to exhibit maximium ME region as well as water solubilization capacity (WSC). Values of both these parameters were found to decrease as chain length of surfactant increased in all cases of alkanols with exception of Tween 80. This could be attributed to unsaturated structure of Tween 80 which presumably caused folding of chain and lesser oil penetration. Furthermore, the transition of w/o MEs to o/w MEs via bicontinuous structure along the dilution line was confirmed by conductivity, viscosity and droplet size analysis