| Abstract
| - Calorimetric and X-ray diffraction investigations of anhydrous α trehalose obtained by dehydration of itsdihydrate form have been performed. The results show that the structural and thermodynamic properties ofthe dehydrated state strongly depend on the kinetics of water loss. A fast dehydration promotes the formationof a glassy amorphous phase and thus provides an unusual example of direct transformation from crystal toglass. On the other hand, a slow dehydration promotes the formation of a polymorphic crystalline phase (α)of anhydrous trehalose. We also show how this duality crystalline state/glassy amorphous state has led, inprevious studies, to a confused pattern of thermodynamic properties of the dehydrated state of trehalosedihydrate. Our results show, in particular, that the properties of the glassy amorphous trehalose obtained bydehydration are very close to that of the quenched liquid trehalose.
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