3.4.3. Thermal Properties

The thermal properties of the DPA and DPA\_PA salt were evaluated by DSC and TG measurements. DSC revealed a single sharp endotherm at 84 ◦C in agreement with a reported metastable form at 85 ◦C. In the DSC curve of the DPA\_PA salt, the endothermic peak at around 161 ◦C is the melting point of salt, which is significantly different from DPA (84 ◦C) and PA (216 ◦C) (Figure S3). TG data of the DPA single crystal revealed that no weight loss before melting confirmed the absence of any solvent or hydrate in the crystal lattice as same as that of DPA commercial. Also, the thermal stability and decomposition processes of DPA\_PA salt have been shown, measured by simultaneous TG in flowing air. The DPA\_PA salt is stable until 160 ◦C (Figure S4). There are no thermal moments for all crystals before the melting process, indicating that these crystals are unsolvated.
