Study on Inclusion Complexes of Cyclodextrin with Sodium Dodecyl Polyoxyethylenated Sulfonate Using Microcalorimetry and 1H NMR

Abstract

The association of α‐, β‐ and γ‐cyclodextrin (α‐CD, β‐CD and γ‐CD) with sodium dodecyl polyoxyethylenated sulfonate (C12EnS n=1, 3) was studied by means of isothermal titration calorimetry and 1H NMR measurements in aqueous solution at T=298.15 K. The results indicate that the binding processes of β‐CD with the surfactants are characterized by both enthalpy favorable and entropy favorable, while those of α‐CD or γ‐CD with the surfactants are mainly entropy driven. The stoichiometry of β‐CD binding with the surfactants is different with different numbers of oxyethyl groups in surfactant molecules, while that of α‐CD or γ‐CD binding with the surfactants makes no difference. The 1H NMR spectra reveal that chemical shift data of all protons in α‐CD, β‐CD and γ‐CD molecules move to high field in the presence of C12EnS, which can be regarded as a microscopic evidence of the occurrence of inclusion interaction.