Surfactant-free oil/water and bicontinuous microemulsion composed of benzene, ethanol and water

Generally, a microemulsion consists of oil, water, surfactant and sometimes cosurfactant. Herein, we report a novel surfactant-free microemulsion (denoted as SFME) composed of benzene, water and ethanol without the amphiphilic molecular structure of traditional surfactant. The phase behavior of the ternary system was investigated, finding that there were a single-phase region and a two-phase region in ternary phase diagram. The electrical conductivity measurement was employed to investigate the microregion of the single-phase region, and a bicontinuous microregion and a benzene-in-water (O/W) microemulsion microregion were identified, which was confirmed by freeze-fracture transmission electron microscopy (FF-TEM) observations. The sizes of the microemulsion droplets are in the range of 20–50 nm.