A new model for describing the surface tension of binary liquid mixtures as a function of the bulk composition over the whole concentration range is presented. We first derive an equation relating surface and bulk volume fractions that generalizes the Langmuir isotherm so as to cover the entire range of concentrations. By combining this isotherm with a new mixing rule for nonideal solutions, we obtain an equation with two adjustable parameters, one measuring the lyophobicity of one component and the other accounting for the effect of molecular interactions. The model provides an excellent description of surface tension data for a wide variety of solutions with π0 = σA − σB values ranging from 2.2 to 51.0 mN/m.

An extensive dynamic and structural characterization of the supramolecular complexes that can be formed by mixing α-, β-, and γ-cyclodextrin (CD) with sodium dodecyl sulfate (SDS) in water at 283, 298, and 323 K was performed by means of computational molecular dynamics simulations. For each CD at the three temperatures, seven different initial conformations were used, generating a total of 63 trajectories. The observed stoichiometries, intermolecular distances, and relative orientation of the individual molecules in the complexes, as well as the most important interactions which contribute to their stability and the role of the solvent water molecules were studied in detail, revealing clear differences and similarities between the three CDs. Earlier reported findings in the inclusion complexes field are also discussed in the context of the present results. For any of the three native cyclodextrins, the CD(2)SDS(1) species in the head-to-head conformation appears to be a promising building block for nanotubular aggregates both in the bulk and at the solution/air interface, as earlier suggested for the case of α-CD. Moreover, the observed noninclusion arrangements involving β-CD are proposed as the seed for the premicellar (β-CD)-induced aggregation of SDS described in the literature.

No abstract

Excess molar volumes and isobaric excess molar heat capacities for 1,4-dioxane + 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol and excess molar enthalpies for the binary mixtures 1,4-dioxane + methanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol at the temperature 298.15 K have been determined as a function of mole fraction. The magnitude of these experimental quantities is discussed in terms of the nature and type of intermolecular interactions in binary mixtures. When available, the results have been compared with literature values.