Microemulsion

The term "Microemulsion" was first introduced by Hoar and Schulman (1943) to describe a clear solution obtained when normal O/W coarse emulsions were titrated with medium-chain length alcohols. Daniel son and Lind man (1981) define microemulsion as a system of water, oil, and amphiphile which is an optically isotropic and thermodynamically stable liquid solution. Microemulsion refers to a thermodynamically stable isotropically clear dispersion of two immiscible liquids, such as oil and water, stabilized by an interfacial film of surfactant molecules. A microemulsion is an oil phase and a water phase, in combination with a surfactant. The dispersed phase typically comprises small particles or droplets, with a size range of 5 nm-200 nm, and has very low oil/water interfacial tension. Because the droplet size is less than 25% of the wavelength of visible light, microemulsions are transparent. The microemulsion is formed readily and sometimes spontaneously, generally without high-energy input. In many cases a co surfactant or co solvent is used in addition to the surfactant, the oil phase and the water phase.