Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in material science and condensed matter physics. It has emerged as a major focus for industry and regulatory agencies respectively. Thermomicroscopy, infrared spectroscopy and thermal analysis, especially differential scanning calorimetry (DSC) is used to characterize polymorphism to provide a powerful to isolate and identify of crystalline modification. Enantiotropic and monotropic with reversible endothermic and irreversible exothermic phase transition is representative classifications of polymorphism. Recently, Dirac metamaterial based on pyrene derivatives is attracting great attention. It succeeded in forming a periodic and regular structure using the unique {pi}-{pi} interaction of the pyrene derivative, namely HYLION-12. The phase transition between modifications is not classified into the existing polymorphism system. Here, we propose a new kind of polymorphism by identifying and analyzing thermodynamic functions such as heat capacity, enthalpy, entropy and, Gibbs free energy between modifications from DSC. This not only allows us to better understand the formation of Dirac materials at the molecular level, but also to think about the condition for new types of polymorphism.
Download