Two-site adsolubilization model of incorporation of alcohols into adsorbed surfactant aggregates

Abstract

The behavior of adsorbed surfactant aggregates, admicelles, was found to be very similar to that of micelles in the presence of alkanes. However, peculiar phenomena were observed in the incorporation of alcohols into admicelles: (i) very high ratios of alcohol to surfactant adsorption at lower coverages, (ii) remarkable increases of surfactant adsorption below the cmc, and (iii) a slight decrease of plateau adsorption. A two-site adsolubilization model is presented to interpret this complicated system. The hypothesis is that while the alkanes are adsolubilized only in a hydrocarbon core of the admicelle, there are two sites at which alcohols are adsolubilized, at the core and at the hydrophobic perimeter of the admicelle. The resulting model seems to be reasonable not only in explaining general trends in the alcohol and surfactant adsorption data but also in its estimates of aggregation numbers and the variation of aggregation numbers with alcohol and surfactant concentrations.

Small-Molecule Surfactant Adsorption, Polymer Surfactant Adsorption, and Surface Solubilization: An Overview

“…time-resolved resonance Raman spectroscopy has been described. Adsolubilization of a series of alcohols and alkanes into SDS admicelles on alumina were measured and compared to solubilization by micelles (104). For alkanes, the standard free energy of transfer of the alkanes into the admicelles was similar to that found with transfer of alkanes into micelles.…”

“…The (higher) internal pressure of the micelle would increase the chemical potential of solubilizate and therefore reduce its partition coefficient on a concentration basis into the micelle. A counter to this argument would be the similar free energy of transfer found for the alkanes partitioning into admicelles and micelles (104). However, the counter argument is only valid if the alkane did not transform the admicelles (-zero curvature) to highly curved small surface aggregates postulated by Zhu and Gu.…”

Adsorption of triton X-100 on silica gel: effects of temperature and alcohols

“…In monolayered hemimicelles the surfactant tails form a "hydrophobic film" in contact with the equilibrium aqueous solution. Even in bilayered admicelles, the direct water-tail contact occurs along the hydrophobic perimeter of the aggregates [52].…”

Facilitated transport of a PAH mixture by a rhamnolipid biosurfactant in porous silica matrices

“…different types of matrices Fig. 6 Park and Jaffe, 1993;Nayyar et al, 1994;Sun et al, 1995 , Lee et al, 1990;Edwards et al, 1994 , Ž . and type of matrix Esumi et al, 1997 .…”

“…Park and Jaffe, 1993 or to the affinity of the less hydrophobic compounds to thé perimeter of incompletely formed admicelles where the hydrophobic surfactant tails are Ž . exposed to the aqueous phase Lee et al, 1990;Nayyar et al, 1994 . surfactant was more that 10-fold for contaminants with log K ) 5.…”