1H NMR study of rehydration/dehydration and water mobility in β-cyclodextrin Original Research Article

The processes of dehydration and rehydration of β-cyclodextrin were studied by analysis of the 1H NMR (nuclear magnetic resonance) line shape. Dehydration was carried in an open ampoule as a function of temperature and above 400 K total dehydration of β-cyclodextrin was observed. This result was confirmed by the thermogravimetry (TG) measurements. Rehydration was studied as a function of time at room temperature. After 40 days, β-cyclodextrin was found to absorb eight water molecules. The analysis of temperature changes in the shape of the 1H NMR line of β-cyclodextrin kept in a closed ampoule and its dielectric measurements provided information on the mobility of water molecules. The water molecules were found to perform complex molecular motions, that is, reorientational jumps below 200 K and additionally, translational motion (diffusion) above 200 K.