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In colloidal and surface chemistry, the critical micelle concentration (CMC) is defined as the concentration of surfactants above which micelles form and all additional surfactants added to the system will form micelles. [1] The CMC is an important characteristic of a surfactant.
In colloidal chemistry, the critical micelle concentration (CMC) of a surfactant is one of the parameters in the Gibbs free energy of micellization. The concentration at which the monomeric surfactants self-assemble into thermodynamically stable aggregates is the CMC.
The shape and size of a micelle are a function of the molecular geometry of its surfactant molecules and solution conditions such as surfactant concentration, temperature, pH, and ionic strength. The process of forming micelles is known as micellisation and forms part of the phase behaviour of many lipids according to their polymorphism .
Micellar solutions form when the concentration of amphiphile exceeds the critical micelle concentration (CMC) or critical aggregation concentration (CAC), which is when there are enough amphiphiles in the solution to clump together to form micells.
The critical micelle concentration (CMC) in water at 25 °C is 8.2 mM, [1] and the aggregation number at this concentration is usually considered to be about 62. [3] The micelle ionization fraction (α) is around 0.3 (or 30%). [4]
CM is the concentration of the micelle in the mobile phase (total surfactant concentration - critical micelle concentration) A plot of 1/k¢ verses CM gives a straight line in which KSW can be calculated from the intercept and KMW can be obtained from the ratio of the slope to the intercept. Finally, KSM can be obtained from the ratio of the ...
In colloidal chemistry, an aggregation number is a description of the number of molecules present in a micelle once the critical micelle concentration (CMC) has been reached. In more detail, it has been defined as the average number of surfactant monomers in a spherical micelle.
For most lyotropic systems aggregation occurs only when the concentration of the amphiphile exceeds a critical concentration (known variously as the critical micelle concentration (CMC) or the critical aggregation concentration (CAC)). At very low amphiphile concentration, the molecules will be dispersed randomly without any ordering.