Solubilization and interfacial curvature in microemulsions: II. Surfactant efficiency and PIT

We show that perfume molecules can be considered as co-solvents and/or as co-surfactants in microemulsion systems. They can affect the phase-inversion temperature and surfactant efficiency. Based on our previous solubilization studies (part I of this series of articles, this issue), we establish a relationship between the interfacial curvature and the surfactant efficiency as a function of the excess perfume penetrating the interfacial layer. This result gives guidelines to minimize the concentration of surfactant used in formulations and to position the phase boundaries.