Heat Capacity Study to Evidence the Interactions between Cyclodextrin and Surfactant in the Monomeric and Micellized States

Abstract

The heat capacities of transfer (∆Cpt) of hydroxypropyl-R-cyclodextrin and hydroxypropyl-γ-cyclodextrin (0.05 mol kg -1 ) from water to aqueous solutions of sodium hexanoate, sodium decanoate, and sodium dodecanoate were determined at 298 K. The measurements were extended to both the pre-and the postmicellar regions. The shape of the ∆Cp t as a function of the surfactant concentration curve is system specific. As well, the ∆Cpt magnitude depends on the macrocycle cavity being largely negative for HP-γ-CD. The qualitative analysis of the experimental data highlights that the features of the heat capacity are different from those of the enthalpy due to the important effect of temperature on the equilibria in solution. The experimental points were treated by means of a new equation based on the following contributions: (i) the formation of host-guest complexes in the aqueous phase, (ii) the shift of the micellization equilibrium induced by the cyclodextrin, and (iii) the interaction between micelle and cyclodextrin (free and complexed). The resulting equation is involved since it contains not only the terms related to the various equilibria in solution but also those relative to their shift with temperature. Despite its complexity, the equation fitted very well the experimental points in the absence and the presence of micelles.

Cyclodextrin/Amphiphilic Phosphane Mixed Systems and their Applications in Aqueous Organometallic Catalysis

“…However, Milioto et al. clearly demonstrated that HP‐α‐CD or HP‐γ‐CD interacted with sodium alkanoates‐based micelles 41,42,43. In that case, CDs adsorbed on the micelle surface because of hydrogen bonding between the carboxylate groups of the micelle components and the CD hydroxyle functions.…”

Factors controlling flavors binding constants to cyclodextrins and their applications in foods

“…The binding constant and the change in the property for the host-guest complex formation can be simultaneously estimated from the bulk thermodynamic properties like calorimetry (Castronuovo, Elia, Niccoli, & Velleca, 2003), density (Martínez et al, 1999) and heat capacity (De Lisi, Lazzara, Milioto, Muratore, & Terekhova, 2003).…”

Cyclodextrin-Surfactant Mixed Systems as Reaction Media

“…Recent results from the study of the enthalpy of transfer of CD from water to aqueous surfactant solutions suggest the existence of interactions between micelles and CDs in systems using hydrogenated [43,44] and fluorinated [45] alkanoates. Quantitative analysis of the postmicellar region indicates that the CD -micelle forces are ion -dipole (carboxylate head=hydroxylic group) in nature.…”