Evaluation of the absolute configurational entropy of tri-O-methyl-8-cyclodextrin, a molecule with many degrees of freedom

In this study, we evaluated the temperature dependence of the absolute configurational entropy of tri-O-methyl8-cyclodextrin (TMCD), a molecule with many degrees of freedom. We calculated the configurational entropy from the configurational heat capacity obtained by subtracting the calculated heat capacity due to lattice vibrations and intramolecular vibrations from the heat capacity measured above the glass-transition temperature. We fitted the configurational heat capacity using both a power law and a logarithmic function based on Landau's critical-point theory. The configurational entropy increases more gradually as the temperature increases. We found that the temperature at which the configurational entropy vanishes (the so-called Kauzmann temperature TK) lies between 280 K and 298 K for TMCD. This is about 50 K lower than the glass-transition temperature of TMCD, which is consistent with the expectations.

Automated summary

In this study, we investigated the relationship between the absolute configurational entropy of TMCD and temperature. We calculated the configurational entropy by subtracting the heat capacity due to lattice vibrations and intramolecular vibrations from the measured heat capacity above the glass-transition temperature. The configurational heat capacity was fitted using both a power law and a logarithmic function based on Landau's critical-point theory. The results showed that the configurational entropy increases gradually with increasing temperature. The temperature at which the configurational entropy vanishes (TK) for TMCD was found to be between 280 K and 298 K, which is about 50 K lower than the glass-transition temperature and consistent with expectations.