Characteristics of Enthalpy Relaxation in Glassy <sc>d</sc>-Mannitol by Nanocalorimetry

d-Mannitol has attracted significant interest as a model system for understanding polyamorphism. In this study, the characteristics of enthalpy relaxation in d-mannitol glass are investigated using high-rate, high-precision nanocalorimetry under different controlled thermal histories. Key parameters, including glass-forming ability, liquid fragility, and activation energy for structural alpha relaxation, are determined by examining the dependence of crystallization enthalpy, limiting fictive temperature and glass transition temperature on cooling and heating rates. Isothermal physical aging experiments are conducted at temperatures significantly below the glass transition temperature over time scales spanning five decades. The kinetics of enthalpy relaxation is analyzed using the stretched exponential function, revealing that the extrapolated liquid line may not be reached by aging. A transition from slow beta relaxation to alpha relaxation is identified through the Kissinger analysis across a range of heating rates. Further analysis of enthalpy relaxation using the absolute reaction rate theory reveals that the memory effect can occur without an increase in activation entropy during temperature up-jumps. These findings highlight d-mannitol as a compelling system for understanding relaxation behavior in glassy materials.