The origin of the concept of the critical microemulsion concentration (CmuC) and its relation to the surfactant molecular structure

Abstract: The critical microemulsion concentration (CmuC) is the minimum surfactant concentration required to produce bicontinuous microemulsions (and obtain ultralow interfacial tension).  This concentration is very important from a practical point of view because it dictates the surfactant concentration required to obtain the formulation benefits of low interfacial tension. However, very little is known about how the molecular structure of the surfactant affect the value of the CmuC. In this work, we review some of the literature on interfacial tension (IFT) vs. surfactant concentration curves, interpreting that data in light of the Gibbs adsorption isotherm and in terms of the HLD-NAC calculated Interfacial tension. After combining these two IFT models, a new model emerges that relates the value of the CmuC vs. the surfactant molecular structure.