New Role for an N, N′-Alkylidene Bridge: Taming the Hygroscopicity of Acidic Energetic Materials with Enhanced Stability

Hygroscopicity can cause undesirable chemical reactions, affect the stability and compatibility, and also the reduce strength and detonation performance of energetic materials; therefore, it should be avoided for civil and military applications. The existence of acidic protons in the molecule is the main causes of hygroscopicity, and the most common strategy to eliminate acidic hydrogen includes the formation of salts, introduction of N-CH₃or N-NH₂groups, etc. In this work, we present the preparation of tricyclic fused-ring energetic compounds derived from bi(1,2,3-triazole) by introducing an N,N′-alkylidene bridge which could act as a "buffer" to reduce the external stimuli, therefore resulting in compounds with enhanced thermal stability and reduced sensitivity as well as elimination of the hygroscopicity and acidity in the meantime. Their physical and chemical properties were determined and interpreted by both experimental and theoretical methods. The nonhygroscopicity, good thermal stability (C1, T_d= 277 °C; C2, T_d= 290 °C), low sensitivity (C1, IS = 30 J, FS > 360 N; C2, IS = 50 J, FS > 360 N), and detonation properties (C1, D = 8287 m s^-1P = 29.4 GPa; C2, D = 8027 m s^-1P = 25.4 GPa) comparable to those of TATB (D = 8114 m s^-1P = 31.2 GPa) make them desirable candidates as high-energy insensitive energetic materials.