Nonpolar Thermodynamically Stable Nanodrop Emulsions with Film-Forming Capacity

Abstract

Obtaining thermodynamically stable nonaqueous microemulsions has so far required at least one component to be polar. This requirement introduces limitations when strictly nonpolar media are needed. In this report, we describe the spontaneous formation of completely nonpolar, thermodynamically stable microemulsions by incorporating a semifluorinated alkane that acts as a “solvotrope” into a mixture of hydrocarbon and fluorocarbon oils. These microemulsions are composed of narrowly dispersed nanodrops of one liquid within the other, leading to the formation of both hydrocarbon-in-fluorocarbon and fluorocarbon-in-hydrocarbon microemulsions, depending on the ternary mixture composition. We also report a phase separation at the microemulsion-air interface: when the hydrocarbon oil serves as the continuous phase, the fluorocarbon nanodrops rapidly and preferentially adsorb at this interface. This leads to the formation of a thin hydrophobic and lipophobic surface film. These findings enhance our understanding of microemulsions and the ouzo effect, which were previously confined to polar systems, now extending their relevance to completely nonpolar systems and opening up new possibilities for applications.