Benzimidazole-based low-sensitivity and heat-resistant energetic materials: design and synthesis

Heat-resistant and low-sensitivity energetic materials are urgently needed in demanding environments, such as deep oil wells, space blasting, and hypersonic weapons. Herein, through the processes of substitution, reduction, cyclization, nitration, and ammoniation, two nitro groups and two amino groups were successfully introduced into a benzimidazole framework to prepare a new heat-resistant energetic material, 4,6-diamino-5,7-dinitro-1H-benzo[d]imidazole (DADNBI). Single crystal X-ray diffraction was executed to verify the structure of the compound. Crystal DADNBI belongs to the C2/c space group and monoclinic crystal system. The thermal stability of DADNBI was analyzed through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and results showed that the decomposition temperature of DADNBI was 366 °C, which is higher than that of 2,4,6-trinitrotoluene (TNT) (T_d: 295 °C), hexanitrostilbene (HNS) (T_d: 318 °C), and 5,5′-bis(2,4,6-trinitrophenyl)-2,2′-bi(1,3,4-oxadiazole) (TKX-55) (T_d: 335 °C) and comparable to that of 1,3,5-tritamino-2,4,6-trinitrobenzene (TATB) (T_d: 360 °C). Non-isothermal thermal decomposition kinetics and Mayer bond pole calculations verified the excellent thermal stability of DADNBI from a theoretical perspective. The characteristic drop height (h_50%) of DADNBI is 305 cm. All these parameters of DADNBI far exceed those of the reported 5,7-dinitro-1H-benzo[d]imidazole (DNBI). This work offers important guidelines from both theoretical and experimental perspectives for designing and synthesizing new insensitive heat-resistant energetic materials.