Effects of N-oxide on the thermal stability of energetic materials: A case study of 2,6-Diamino-3,5-dinitropyrazine-1-oxide

Finding new insensitive high explosives has been the focus of the energetic materials community in recent decades. To accelerate the discovery process, it is necessary to elucidate the relationship between molecular structure and the performance of explosives. In this regard, the effects of N-oxide groups, commonly introduced to increase the energy density of explosives, on the thermal stability of explosives were investigated by comparing the thermal behaviors of a typical energetic N-oxide, ANPZO, and its analogue ANPZ. The presence of N-oxide facilitated the thermal decomposition of ANPZO thoroughly and suppressed its sublimation to a certain extent. Compared to ANPZ, the introduction of N-oxide increased the thermal enthalpy, reduced the solid residues, and shortened the acceleration period of thermal decomposition of ANPZO. Additionally, the sublimation rate and vapor pressure of ANPZO were lower than those of ANPZ. The enthalpy of sublimation for ANPZO was 175.1 kJ mol(-1), compared to 135.2 kJ mol(-1) for ANPZ. The effects of N-oxide on the thermal decomposition and sublimation are attributed to its contribution to the augmentation of oxygen sources and intermolecular interactions, respectively. This study provides further insight into the relationship between the N-oxide group and the performance of explosives, which could be beneficial for the design and application of new explosives.