Microcalorimetric study of the influence of alcohols on the critical micelle concentration and thermodynamic functions of nonaqueous micelle solutions at 298.15 K

The power-time curves of the micellization process were determined for two kinds of anionic surfactants [sodium laurate (SLA) and sodium dodecyl sulfate (SDS)] and a kind of nonaqueous solvent [N,N-dimethyl formamide (DMF)] with mixed alcohols by titration microcalorimetry. From the data of the lowest point and the area of the power-time curves, the critical micelle concentration (CMC) and Delta H-m(0). were obtained. Delta G(m)(0) and Delta S-m(0) were also calculated according to the thermodynamic theory. For different surfactants, cosurfactants, and solvents, the relationships between the alcohol's carbon number, concentration, and CMC and the thermodynamic functions are discussed. For an identical alcohol concentration at the same temperature, the values of CMC, Delta H-m(0), Delta G(m)(0), and Delta S-m(0) decrease with an increase in the carbon number of the alcohol. For each alcohol at the same temperature, the CMC and Delta G(m)(0) increase, while Delta H-m(0) and Delta S-m(0) decrease with an increase in the alcohol concentration.