https://doi.org/10.1039/D4NJ05047A
Abstract: 1-Ethyl-3-methylimidazolium dinitramide (EMImDN), an energetic ionic liquid, was synthesized and characterized by IR, 1H NMR, 13C NMR, 15N NMR, and 17O NMR techniques. The thermal properties of EMImDN were investigated through DSC and TG analyses. The TG curve revealed three consecutive exothermic decomposition events with peak temperatures at 223 oC, 277 oC and 308 oC, accompanied by an 80 % mass loss between 180 oC and 280 oC. The thermal decomposition kinetics were analyzed using the Kissinger method and Flynn-Wall-Ozawa isoconversional method. The activation energies for the three decomposition stages were calculated to be 41.1, 35.9 and 43.2 kcal/mol respectively by Kissinger method and 39.0, 36.8 and 42.6 kcal/mol respectively by FWO method. Pyrolysis GC-MS analysis identified the decomposition products, and the decomposition mechanism was predicted to involve dealkylation of the imidazole ring via bimolecular nucleophilic substitution (SN2). The proposed decomposition mechanism was further supported by density functional theory (DFT) calculations at B3LYP/6-311+G(d,p) level. Additionally, the molar enthalpy of formation of EMImDN (+54.5 kcal/mol), determined through combustion calorimetry, underscores the energetic nature of this ionic liquid. Notably, a 10 wt.% solution of NH3BH3 in EMImDN exhibited hypergolicity with red fuming nitric acid. Preliminary investigations into the interactions of EMImDN with HNO3 and NH3BH3 provide insights into the initial stages of this hypergolic reaction.