Polyamorphism and liquid-liquid transformations in D-mannitol.

The polyamorphism exhibited by D-mannitol between the normal melt quenched glass (GN) and the amorphous Phase X (GX) induced by annealing has been examined in a detailed series of differential scanning calorimetry (DSC) measurements covering a wide range of scanning rates. The glass transition of the (GN), TgN develops an increasing behavior upon annealing, but the glass transition of (GX), TgX changes little during annealing, implying that (GX) is a kinetically more stable glass. A series of interrupted thermal cycles has allowed for the identification of a liquid-liquid transition between the supercooled liquid of (GN), SCL-1 and that for (GX), SCL-2. The precise annealing conditions that could be reached by Flash DSC enabled the construction of the Temperature-Time-Transformation plot of D-mannitol for the transition between GN/(SCL1) and G X/(SCL2), as well as the transition between amorphous and crystalline phases revealing thermally activated behavior. Under the action of an applied stress, GX can be induced to transform irreversibly into the higher density GN.