Cosurfactant definition

When chloro-octadecane was found to give the same result as a so-called cosurfactant, an argument arose in terms of the real role of this highly hydrophobic compound because it is not surface active and has no cooperation with surfactant. Taking account of these systems, the definition of miniemulsion polymerization will be revised to the polymerization in which a water-insoluble compound in the dispersed phase retards or inhibits diffusion degradation of the emulsion. ... 

When one compares microemulsions and micelles, the demarcation line can become quite blurred and, in some cases, does not exist. There is some controversy as to the true definition of clear, isotropic solutions of oil, water, and surfactant (and cosurfactant if needed) as microemulsions rather than swollen micelles. Although the differences between the two systems may appear to many to be more semantic than real, several arguments have been presented that strongly support a differentiation of the two systems. 

Nonionics can function as cosurfactants in microemulsions. This cosurfactant role, which can also be performed by short-chain alcohols or glycol ethers, can make it possible to form microemulsions or other phases from anionic surfactant systems that would otherwise be unreachable in a pure anionic system. By one definition, a microemulsion system is one that achieves a zero or close-to-zero curvature [108]. This is easily achievable in nonionic systems, but very difficult in pure anionic surfactant systems due to the head group repulsions. Mixing the nonionic with the anionic makes these types of systems, which sometimes have greater cleaning ability, easily accomplished. 

Many attempts have been made to characterize these nanostructures by a good general definition. The best present definition states A microemulsion is a mixture of two immiscible liquid phases into nanosized aggregations in the presence of surfactants and sometimes with a need of cosolvents or cosurfactant. This definition does not mention the size or shape of the nanodroplets or nanostructures. The sizes are always smaller than 0.1 im (mostly a few nanometers), and the shapes can be spherical, disklike, cylindrical, or sheetlike (termed bicon-tinuous phases). 

A distinction has to be made between kinetically and thermodynamically stable emulsions. Mixtures of water, an oil, a surfactant, and a cosurfactant in proper proportions can spontaneously form transparent, themiodynamically stable emulsions, called microemulsions. The definition is not quite unequivocal. Thermodynamically unstable but kinetically stable systems which form spontaneously have also been called microemulsions [117]. Micellar solutions have been included in the definition of microemulsions and the debate on microemulsion structure is ongoing. 

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