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Dancing with 5-substituted monotetrazoles, oxygen-rich ions, and silver: towards primary explosives with positive oxygen balance and excellent energetic performance

Sun, Qi, Li, Xin, Lin, Qiuhan, Lu, Ming
Journal of materials chemistry A 2019 v.7 no.9 pp. 4611-4618
X-ray diffraction, carbon dioxide, combustion, coordination polymers, differential scanning calorimetry, explosives, ions, ligands, nitrates, oxidants, oxygen, silver, temperature, thermal stability, thermogravimetry
Although numerous primary explosives have been reported to date, those with a positive oxygen balance are extremely rare. To overcome this limitation, we present two strategies to improve the oxygen balance: (1) increasing the oxygen balance in the ligands and (2) the introduction of oxygen-rich ions. By applying these strategies, a series of energetic coordination polymers (ECPs) consisting of 5-substituted monotetrazoles, oxygen-rich ions, and silver (viz. [Ag₇MT₄(NO₃)₃]ₙ, [Ag₃HT₂NO₃]ₙ, [Ag₇AT₄(NO₃)₃]ₙ, [Ag₅NT₄NO₃]ₙ, and [Ag₅NT₄ClO₄]ₙ) were prepared. Their structures were characterized using single crystal XRD, IR, and elemental analysis and their properties were evaluated in terms of density, thermal stability, mechanical sensitivity and oxygen balance. In addition, the potential structure–property relationships of these polymers were studied. All five ECPs possessed high densities ranging from 3.12 to 3.60 g cm⁻³. DSC and TGA analysis showed that the ECPs have high thermal stability with decomposition temperatures ranging from 251 to 348 °C. All the ECPs were sensitive to stimuli and should be classified as primary explosives. Oxygen balance calculations, detonation reactions, and combustion experiments showed that [Ag₅NT₄NO₃]ₙ and [Ag₅NT₄ClO₄]ₙ have a positive oxygen balance, which gives the first two examples of ECP-based primary explosives exhibiting a positive oxygen balance (based on CO₂). Explosion experiments showed that [Ag₅NT₄NO₃]ₙ and [Ag₅NT₄ClO₄]ₙ, which display a positive oxygen balance, deliver improved initiation performance when compared to [Ag₇MT₄(NO₃)₃]ₙ, [Ag₃HT₂NO₃]ₙ, and [Ag₇AT₄(NO₃)₃]ₙ, which have a negative oxygen balance. Therefore, [Ag₅NT₄NO₃]ₙ and [Ag₅NT₄ClO₄]ₙ are efficient primary explosives. In addition, the positive oxygen balance of [Ag₅NT₄NO₃]ₙ and [Ag₅NT₄ClO₄]ₙ indicates their potential application as energetic oxidizers.