Modifying polynitro benzene and pyrazine skeletons with flexible nitratoethyl substituents towards new energetic melt-castable materials

The development of new energetic melt-castable materials that can replace trinitrotoluene (TNT) is an important focus in energetic material research. Here, we developed a promising strategy for incorporating energetic flexible substituent groups onto a high-melting-point molecular skeleton to develop new energetic melt-castable materials. Using this method, five nitratoethyl-functionalized polynitro benzenes and pyrazines were synthesized. Among the prepared compounds, 1-(2-nitrato-ethylamino)-2,4,6-trinitrobenzene (MSR-1) and 1-bis(2-nitrato-ethyl)amine-2,4,6-trinitrobenzene (MSR-2) exhibited the potential as energetic melt-castable materials due to the desirable wide temperature range over which the materials were liquid, ranging from the melting point (T_m: 90.5 °C and 104.8 °C, respectively) to the high decomposition temperatures (T_d: 204.7 °C and 208.8 °C, respectively). Moreover, their densities (1.68 g cm⁻³, 1.71 g cm⁻³, respectively), detonation performances (7654 m s⁻¹, 7802 m s⁻¹, respectively) and impact sensitivities (20 J) were superior to those of TNT (1.65 g cm⁻³, 7303 m s⁻¹, 15 J, respectively). A quantitative and accurate method of binding energy in cluster (BEC) is proposed to account for the melting-point differences in the prepared energetic compounds. The average binding energy between the close-contacting dimers in the molecular clusters showed strongly positive correlation with the molecular melting point.