DEPENDENCE OF CRITICAL MICELLE CONCENTRATIONS ON INTENSIVE VARIABLES - A REDUCED VARIABLES ANALYSIS

An analysis of the relations between critical micellar concentrations (cmc's) and temperature, or between cmc's and applied pressure, indicates that experimental data fit on U-shaped curves whose minimum is cmc*T and T*, or cmc*P and P*, respectively. Irrespective of alkyl chain length, polar head groups, and counterions, cmc versus temperature data can be fitted in reduced equations keeping the form cmc(T)/cmc*T - 1 = |1 - T/T*]γ, where γ is an exponent. Similar fits account for the relations between cmc's and the applied pressure. Some considerations on the thermodynamics of micelle formation are discussed according to the above statements. In particular, the reduced variables approach allows to determine accurate values for the entropy of micelle formation. © 1990 American Chemical Society.