Metastability release of the form α of trehalose by isothermal solid state vitrification

Kinetic investigations of the polymorphic form alpha of anhydrous trehalose have been performed below its apparent melting temperature (T(m)) by differential scanning calorimetry (DSC) and X-ray diffraction. The results reveal a spontaneous isothermal vitrification process which indicates that the phase alpha is in a very unusual superheating situation. This behavior has been attributed to the fact that the effective melting temperature (T(m)(eff)) of the phase alpha is likely to be located far below the glass transition temperature (T(g)) of this compound. The high viscosity of the liquid trehalose between T(m)(eff) and T(g) is thus invoked to explain the long lifetime of the phase alpha in this temperature range.