The explosive performance of crystalline energetic materials is strongly related to the material’s crystal structure. For example, 2,4,6-trinitrotoluene (TNT), one of the most common secondary explosives, is known to predominantly exist as one of two polymorphsmonoclinic or orthorhombicwith the former being more thermodynamically stable. The production of different polymorphs is commonly achieved via crystal growth from solution in which the outcome is highly dependent on the absolute solubility. In the present work, effects related to both the nature and temperature of different solvents used for TNT crystallization are investigated via two separate crystal growth techniques: solvent evaporation and solvent/antisolvent (water) precipitation. The resulting polymorphism for each crystal sample was independently characterized using differential scanning calorimetry and single crystal X-ray diffraction. For both methods of crystallization, results demonstrate a strong correlation between the obtained polymorph and both TNT’s relative solubility in each solvent and the crystal growth temperature. The results are mostly consistent with the theoretical viewpoint of Ostwald’s rule of stages. Furthermore, an investigation of TNT crystals produced from solutions at temperature in excess of 25 °C is reported for the first time. Interestingly, TNT exhibited the formation of a supercooled liquid after undergoing solvent evaporation at 70 °C which is described from the viewpoint of two-step nucleation.

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In the development of crystal engineering and supramolecular chemistry, cocrystallization has been used as a way to develop novel explosives with tailored properties. We present a novel cocrystal solvate composed of 2,4,6trinitrotoluene (TNT) and aniline that exhibits unique physicochemical and explosive properties. X-ray diffraction studies reveal the crystallographic structure to contain TNT and aniline in a 1:1 molecular ratio. The crystals themselves exhibit a vibrant, ruby red color that likely results due to a charge-transfer interaction between the overlapping π-orbitals of the aromatic rings. The most notable evidence for a chargetransfer complex is the appearance of a broad absorbance peak in the visible region which is not present in the spectrum of either pure component. Comparisons of the cocrystal solvate to that of pure TNT are conducted to determine thermodynamic and kinetic parameters using both experimental and theoretical techniques. The desolvation of aniline from the cocrystal solvate was also investigated using both in situ powder X-ray diffraction and atomic force microscopy measurements to monitor changes in the crystal structure and surface topography, respectively.

The kinetic desolvation process of TNT/aniline solvates was investigated using various experimental techniques.