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Influence of the Water Content on the Thermal Behaviour of β-Cyclodextrin at Low and Very Low Temperature

Research paper by P. Germain, C. de Brauer, M. Diot, J. M. Letoffe

Indexed on: 01 Jul '98Published on: 01 Jul '98Published in: Journal of Inclusion Phenomena and Macrocyclic Chemistry



Abstract

Heat capacities of β-CD·9.7H2O weremeasured by adiabatic calorimetry in the temperature range10–300 K. Differential scanning calorimetry wasused to follow the evolution of the thermalbehaviour versus hydration ratio between 170 and300 K. At least three different behaviours wereobserved, according to the number, n, of watermolecules: 0 < n < 7, 7 < n < 10, and n > 10.These macroscopic results are discussed in terms oforganization differences between the most or theleast hydrated β-CD. The structuring effectof the hydration water molecules is emphasised. Theexistence of two energetically distinct β-CDhydrates (n < 10 and n > 10) seems to be confirmed. Thishypothesis is discussed in comparison with previousspectroscopic and structural studies.