Aggregation in Volume Micelles

FIGURE 8.2. Steric model of a spherical micelle in water. Each surfactant molecule has a tail of length R and a polar head whose surface area exposed to water has a prescribed value Ep. 

At this point, the geometry of the micelle, which has a radius R, is fully determined. Its volume is 

Finally, the number p of molecules per micelle is given by p = 367t4 10o4 ( nl). 

Micelles form only above a certain critical micellar concentration (commonly abbreviated as cmc). The cmc can be estimated by means of a crude thermodynamic argument based on chemical potentials. 

Consider the case of an ionic surfactant. The chemical potential of the unassociated surfactant is of the form  

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