Speed of sound, density, conductivity, and fluorescence spectroscopy experiments were run to analyze the mixed aggregation process of a nonionic−cationic surfactant system in aqueous media at 298.15 K. The mixed system comprises a nonionic surfactant, n-octyl-β-d-glucopyranoside (OBG), and a cationic surfactant, tetradecyltrimethylammonium bromide (C14TAB), with 8 and 14 carbon atoms on the hydrophobic tails, respectively. From these data, the total and partial critical micellar concentrations, the total and partial aggregation numbers, apparent molar volumes and isentropic compressibilities, hydration numbers, and the corresponding changes in the latest properties due to the mixed aggregation process were determined. Pure and mixed micelles were analyzed from a geometrical point of view by determining the packing parameter of the aggregates. Furthermore, the experimental characterization of both the monomeric and micellar phases was completed with a theoretical study of the mixed micellization phenomena studied herein, by means of some of the most relevant theoretical models.

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Excess volumes, excess heat capacities and light scattering have been measured for several 1,2-dibromoethane-alkane (n-heptane, n-octane, n-tetradecane, cyclooctane and 2,2,4-trimethylpentane) systems. The results show that there is good agreement between values of the concentration-concentration correlation function S , ,, as calculated from light-scattering data, and the predictions of the simple rigid lattice model of Flory and Huggins, which estimates the relative effects of the differences in molecular sizes and of differences in the interaction energies of the two components. The results also confirm the utility of S,, as predictor of the existence of W-shaped excess isobaric heat capacity (CE) curves, although other effects, such as the destruction of the (partial) correlation of molecular orientation may complicate this issue.