Remarks and further calculations on the thermodynamic properties of enantiotropic polymorphs of glycolide

The dissolution thermodynamic properties of polymorphic glycolide in different organic solvents were researched by Huang and coworkers [J. Chem. Thermodynamics 111 (2017) 106-114]. The analysis of Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TG) indicated that glycolide form 1 has a phase transition between the experimental temperature and the melting point. It should be considered that the effect of phase transformation when calculating the activity coefficient of glycolide form 1 by NRTL model. Moreover, the dissolution properties, including Gibbs energy, enthalpy and entropy of form 1 and form 2 were not consistent with the formula (ΔHdis=ΔGdis+TΔSdis) in published paper. In order to get a better understanding of solution behavior, we tried to further calculate and discuss the activity coefficient (γ1∞) and reduced excess enthalpy (H1E,∞) at infinite dilution of glycolide form 1 and form 2 in this work.