Ambivalent Thermodynamic States of Water in Solid γ-Cyclodextrin Hydrates

The thermodynamics of γ-cyclodextrin hydration was studied using methods of thermal analysis and solution calorimetry. The enthalpy and entropy changes are in a good agreement with two steps of γ‑cyclodextrin hydration isotherm and changes of unit cell volume. The first step of γ-cyclodextrin hydration is more exothermic and has more negative change of entropy while as the second step is less exothermic providing more disorder of water molecules in the hydrate crystal. The kinetic study of γ-cyclodextrin dehydration process revealed the activation energy of this process.