The association of a series of Triton X surfactants which have ethylene oxide (EO) chains of different length with β-cyclodextrin was studied by means of isothermal titration calorimetry (ITC) at 298. 15K. For these type inclusion complexes, the results agreed well with a 1:1 association model. Apparent values for the association constants, and changes in the standard molar Gibbs' energies, enthalpies, entropies, were derived for the association process. The results indicate that the association of surfactants with β- cyclodextrin are strongly enthalpy driven with unfavorable entropy changes. The results also demonstrated that the shorter EO chain of Triton X series surfactant, the greater the association constant with β-cyclodextrin.

Key words: SURFACTANTS, CYCLODEXTRIN, INCLUSION COMPLEXATIONS, CALORIMETRY, THERMODYNAMIC PROPERTIES, ETHYLENE OXIDE