Thermodynamics of micelle formation in water, hydrophobic processes and surfactant self-assemblies

The critical micelle concentration (c.m.c.) for four cationic surfactants, alkyl-trimethyl-ammonium bromides, was determined as a function of temperature by conductivity measurements. The values of the standard free energy of micellisation G°mic at different temperatures were calculated by using a pseudo-phase transition model. Then, from the diagram (-G°mic /T) = f(1/T), the thermodynamic functions Happ and Sapp were calculated. From the plots Happ = f(T) and Sapp = f(lnT) the slopes Cp = nw(H)Cp,w and Cp = nw(S)Cp,w were calculated, with the numbers nw(H) and nw(S) negative and equal and therefore defined simply as nw. The number nw