The glass transition of water, insight from phase change materials

The calorimetric features that have been broadly used to assign a glass transition temperature T_g of 136 K to amorphous water are qualitatively reproduced with a phase change material. Annealing treatments and ultrafast calorimetry measurements indicate that this feature is only a shadow-T_g and that the real T_g lies at higher temperature above the glass transition. A Kissinger analysis of the crystallization kinetics confirms that crystallization occurs below T_g from the glassy state at conventional heating rates. These results strongly suggest that the amorphous water endotherm at 136 K is indeed a shadow-T_g and that the real T_g lies at higher temperature as predicted from structural relaxation considerations.