Glass transition temperature of glucose, sucrose, and trehalose: An experimental and in silico study

Isothermal-isobaric molecular dynamics simulations are used to calculate the specific volume of models of different amorphous carbohydrates ( glucose, sucrose, and trehalose) as a function of temperature. Plots of specific volume vs temperature exhibit a characteristic change in slope when the amorphous systems change from the glassy to the rubbery state. The intersection of the regression lines of data below ( glassy state) and above ( rubbery state) the change in slope provides the glass transition temperature (T-g). These predicted glass transition temperatures are compared to experimental Tg values as obtained from differential scanning calorimetry measurements. As expected, the predicted values are systematically higher than the experimental ones ( about 12-34 K) as the cooling rates of the modeling methods are about a factor of 1012 faster. Nevertheless, the calculated trend of T-g values agrees exactly with the experimental trend: Tg(glucose) < Tg(sucrose) < T-g(trehalose). Furthermore, the relative differences between the glass transition temperatures were also computed precisely, implying that atomistic molecular dynamics simulations can reproduce trends of T-g values in amorphous carbohydrates with high quality.