General Patterns of the Phase Behavior of Mixtures of H2O, Alkanes, Alkyl Glucosides, and Cosurfactants

Abstract

We demonstrate how rather hydrophilic surfactants can be used for solubilizing simultaneously water and alkane. The required hydrophilic−lipophilic balance can be achieved by the addition of a medium-chain alcohol, that is, a hydrophobic cosurfactant. Specifically, the phase behavior of the quaternary water−n-octane−n-octyl β-d-glucopyranoside (C8G1)−n-octanol (C8E0) system has been investigated. Sugar surfactants, in general, are hydrophilic and, because of the comparatively large number of hydroxyl groups, much less temperature-sensitive than the well-known alkylpolyglycolether (CiEj) surfactants. Therefore, one has to resort to tuning the phase behavior by mixing with a hydrophobic cosurfactant. Once this is done, the phase behavior mimics that of water−alkane−CiEj microemulsions. To show this, the trajectory of the middle-phase is determined as the phase inversion is passed. A scaling of the trajectory onto the trajectories of conventional temperature-sensitive ternary microemulsions is possible after...