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Below the CMC point, interfacial tension between oil and water phase is no longer effectively reduced. [10] If the concentration of the surfactant is kept a little above the CMC, the additional amount covers the dissolution with existing brine in the reservoir. It is desired that the surfactant will work at the lowest interfacial tension (IFT).
The critical micelle concentration (CMC) is the exact concentration of surfactants at which aggregates become thermodynamically soluble in an aqueous solution. Below the CMC there is not a high enough density of surfactant to spontaneously precipitate into a distinct phase. [7]
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.
Bottle of 20% sodium dodecyl sulfate in distilled water for use in the laboratory. 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]
An amphiphilic behavior can be observed for water and an organic solvent or between two organic solvents. Note 2: Polymeric micelles have a much lower critical micellar concentration (CMC) than soap (0.0001 to 0.001 mol/L) or surfactant micelles, but are nevertheless at equilibrium with isolated macromolecules called unimers.
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 ...
Above the critical micelle concentration, the anions organize into a micelle, in which they form a sphere with the polar, hydrophilic heads of the sulfate portion on the outside (surface) of the sphere and the nonpolar, hydrophobic tails pointing inwards towards the center. The water molecules around the micelle in turn arrange themselves ...
The molecules will be forced to remain in the aqueous phase when there are no more vacancies for them to stay on the surface. At this point, the surface tension is maximally lowered and is termed as the critical micelle concentration (CMC). [21] The lower the CMC, the more efficient the wetting solution is in reducing surface tension.