In chemistry, the critical micelle concentration (CMC) is defined as the concentration
of surfactants in free solution in equilibrium with surfactants in aggregated form.
Forward & Reverce CMC can be automatically determined; instrumentation
pictured here with an LDU.There are several theoretical definitions of CMC. One well-known definition is that CMC is the total
concentration of surfactants under the conditions:
if C = CMC, (d3F/dCt3) = 0
F = a[micelle] + b[monomer]: function of surfactant
solution
Ct: total concentration
a, b: proportional constants
Therefore, CMC depends on the method of measuring
the samples, since a and b depend on the properties of the solution such as conductance and photochemical characteristics.
When the degree of aggregation is monodispersion, the CMC is not related to the method of measurement. On the other hand,
when the degree of aggregation is multidispersion, CMC is related to both the method of measurement and the dispersion.
The self-organisation of the molecules of surfactants and lipids depends on
the concentration of the lipid present in solution. Below the critical micelle concentration the lipids form a single layer
on the liquid surface and are dispersed in solution. At the first critical micelle concentration (CMC-I), the lipids organise
in spherical micelles, at the second critical micelle concentration (CMC-II) into elongated pipes, and at the lamellar point
(LM or CMC-III) into stacked lamellae of pipes. The CMC depends on the chemical composition, mainly on the ratio of the head
area and the tail length.
