The Relationship between the Interfacial Free Energy and the Free Energy of Micellization of Triton X-100 and Sodium Dodecyl Sulfonate

Abstract

The contact angles for water and Triton X-100 on Teflon; for water, glycerol, formamide, and diiodomethane on Teflon covered with a Triton X-100 film and a sodium dodecyl sulfonate film and glass covered with a sodium dodecyl sulfonate film; and for water, glycerol, and diiodomethane on glass were measured. Also, the surface tension of Triton X-100 and the interfacial tensions of Triton X-100–n-dodecane and Triton X-100–diiodomethane were measured. From the results of these measurements, the Lifshitz–van der Waals component and the electron-acceptor and electron-donor parameters of the acid–base component of the apolar and polar moieties of Triton X-100 and sodium dodecyl sulfonate were determined. Next, taking into account the molecular dimensions of these surfactants, the free energy of interfacial interaction through water was calculated for the apolar and polar parts of Triton X-100 and sodium dodecyl sulfonate. Also, the electrostatic free energy of interactions between DSs−ions was evaluated. Good agreement between the free energy of micellization obtained from the cmc data and the free energy of interaction between molecules of surfactant through water was found.