Abstract: The association of α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) with sodium polyoxyethylene dodecyl sulfonate (C12EnS, n=1, 3) was studied by means of isothermal titration calorimetry and 1H NMR measurements in aqueous solution at 298.15 K. The results indicated that the binding processes of β-CD with the surfactants were characterized by both enthalpy favorable and entropy favorable, while those of α-CD with the surfactants were mainly entropy driven. The stoichiometry of β-CD binding with the surfactants varied with numbers of oxyethyl groups in surfactant molecules, while that of α-CD binding with the surfactants made no difference. The 1H NMR spectra revealed that chemical shift data of all protons in α-CD and β-CD molecules moved to high field in the presence of C12EnS, which could be regarded as a microscopic evidence of the occurrence of inclusion interaction.

Key words: Cyclodexfrin, 1H NMR, Inclusion complex, Isothermal titration calorimetry, Sodium polyoxyethylenated dodecyl sulfonate