Hans Friedrich Eicke

On the stability of micelles in apolar media

Abstract An attempt has been made for the first time to calculate explicitly the stability of micelles built up by ionic surfactants in apolar media. The quantitative treatment based on a geometrical model closely corresponding to the shape and structure of these micelles refers to coulombic and London-Van der Waals interactions. The latter is applied under the suitable assumption that the dispersion forces are additive (“microscopic theory”). The experimentally observed properties of the micelles are well confirmed by this treatment with respect to size, stability, and solvent dependence of the mean aggregation number of the constituent monomers.

Nucleation process of micelle formation in apolar solvents

Abstract Vapor pressure osmometric, dipole moment and dielectric dispersion measurements of aerosol OT, AY, di-2-ethylhexyl sodium phosphate, and lecithin in apolar solvents give strong indications as to the existence of nuclei below the cmc. Based on these observations, a model has been proposed to interpret the micellization process as a phase change. According to this model, explicit calculations of the enthalpy and entropy changes for the micelle formation lead to an estimation of the size of the micelle, of the micellar nucleus, and in addition, to a determination of the free energy of formation of the nucleus. The dependence of these quantities on the selfenergy of the micelle, the temperature, and the cmc is discussed.