Surfactant-free microemulsions

Surfactants (or amphiphiles) are generally believed to be a necessary component of microemulsions. However, research has found that in the absence of traditional surfactants, microemulsions can also form in a ternary system of two immiscible fluids and an “amphi-solvent”. Such microemulsions are called “surfactant-free microemulsions” (SFMEs). The so-called amphi-solvent is a solvent that is completely or at least partially miscible with each of the two immiscible fluids. The structures and properties of SFMEs are similar to those of traditional surfactant-based microemulsions (SBMEs) to some extent. This review focuses on recent advances in SFMEs, including their phase behavior, structures, properties and potential applications.