Thermodynamic mechanism of stability and polymorphic transformation behaviors of enantiotropic polymorphs of glycolide

In this paper, the heat capacity data of two crystal forms (Form1 and Form 2) and liquid state of glycolide were obtained by differential scanning calorimetry (DSC). Their Gibbs energies were calculated by thermodynamic data and relevant thermodynamic equations. The melting point and melting enthalpy of Form 1 which can’t be experimentally determined were successfully calculated. According to the calculated Gibbs energy, thermodynamic stability regions of Form 1 and Form 2 of glycolide were obtained. Through analyzing data of Gibbs energy and activation energy of polymorphic transformation process, the thermodynamic mechanism of the stability and polymorphic transformation behaviors of the two forms of glycolide was proposed and discussed.