Reverse Micelles in Tribochemical Processes

Surface-active agents, or surfactants, all share interesting physicochemical characteristics at surfaces and interfaces. Surfactants (detergents and dispersants) are long chain hydrocarbons with polar headgroups which are called dipoles. Surfactants are molecules which consist of two well defined parts one which is oil-soluble hydrophobic and another which is water-soluble hydrophilic. The hydrophobic part is non-polar and usually consists of aliphatic or aromatic hydrocarbons. The hydrophilic part is polar and interacts strongly with water. 

Normal micelle (M) Soft-core reverse (RM) Hard-core reverse (RM) Hard-core reverse (RM) 

Surfactants fulfil many functions, such as detergency, micelle stabilization, interfacial tension reduction, wetting, and so on. In hydrocarbons, however, surfactants are not capable of lowering the surface tension, because these solvents 

Surfactants are classified on the basis of the charge carried by the polar headgroup as anionic, cationic, nonionic, and amphoteric. Surfactant headgroups are dipoles, especially ionic ones that exist as ion pairs in hydrocarbon solvents. Electrostatic dipole-dipole attraction between headgroups in hydrocarbon solvents is the driving force for the formation of reverse micelles, or micellar aggregates, see Fig. 3.1 and Fig. 3.2. 

The surfactant concentration range above which micelles are formed is called the critical micelle concentration (CMC). Studies have clearly established that most surfactants aggregate above the critical micelle concentration (CMC) to form normal micelles in polar solvents such as water, while they aggregate to form 

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