Thermal degradation mechanism and isothermal sublimation kinetics of DDMEBT: Structure–property correlations for process optimization

Background: 2-[4-(Dimethylamino)phenyl]-3-([4-(dimethylamino)phenyl]ethynyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile (DDMEBT) is a thermally robust organic material of interest for applications requiring controlled volatility. Understanding its thermal stability, decomposition mechanism, and sublimation behavior is critical for optimizing deposition conditions in industrial processes. Methods: A comprehensive set of techniques was employed, including thermogravimetric analysis coupled with mass spectrometry and FTIR spectroscopy (TG/MS/FTIR), differential scanning calorimetry (DSC), ATR-FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic vapor sorption (DVS) analysis, polarized light microscopy (POM), and molecular modeling. Sublimation kinetics were investigated under isothermal conditions (130–150 °C) using anthracene as reference. Significant findings: DDMEBT exhibits a sequential three-step degradation mechanism, independent of heating rate, with high thermal stability (final residue ∼77 %) attributed to its nonplanar architecture and intermolecular π–π/dipole–dipole interactions. Thermal analysis revealed melting at ∼190 °C, structural rearrangements (196–230 °C), and an amorphous-to-crystalline transition at 270 °C. Sublimation proceeds via zero-order kinetics with low volatility (0.178 μg/min at 130 °C) and an activation energy of 66.5 kJ/mol. The determined vapor pressure (1998–4000 Pa) and transport coefficients confirm a thermally activated, hydrodynamically stable process. These findings establish a reliable basis for sublimation modeling and provide guidelines for optimizing material processing in high-temperature, low-volatility applications.