Research Projects

Since the discovery of gunpowder (the first known explosive) in the 9th century, High Energy Density Materials (HEDMs) have greatly benefited humanity in defense, space exploration and civilian applications. Developing innovative energetic materials that demonstrate high energetic performance along with good environmental and personal safety is the major problem facing researchers of energetic materials. Conventional explosives like RDX and HMX are carcinogenic in addition to being sensitive to physical stimuli like impact and friction. The most common oxidizer, ammonium perchlorate and lead/mercury-based primary explosives (lead azide and mercury fulminate), are also bad for the environment. These problems can be remedied using greener synthetic approaches, fine-tuning at the molecular level, and generating greener decomposition products (inert N2 gas). Nitrogen-rich five and six-membered aromatic heterocyclic rings, such as azoles, oxadiazoles, tetrazines, etc., are the backbone of contemporary energetic materials. Because of the presence of many energetic N-N and N=N bonds, energetic materials based on these heterocyclic rings have high positive heats of formation, and harmless dinitrogen (N2) gas is liberated after decomposition. Among azoles, nitropyrazoles-based energetic materials have gained significant popularity because of their high nitrogen and oxygen content, high densities and heats of formation, and acceptable overall stabilities. Further, 4-substituted-3,5-dinitropyrazole-based energetic compounds are the most suitable for designing modern energetic materials because their properties can be regulated by choice of explosophores at the 4th position. While substituents that can form intramolecular hydrogen bonds, like -NH2 and -OH, tend to make the resultant compound more stable, those that are elector withdrawing, like -NO2 and NHNO2, make them more sensitive. Also, it is observed that most of these 4-substituted-3,5-dinitropyrazole cannot be used directly because of the presence of a highly acidic NH bond, which prohibits their practical applications. E.g., 3,4,5-trinitropyrazole (TNP) has excellent energetic properties (Dv = 9253 m/s and P = 38.6 GPa), high thermal stability (Tdec = 260 ˚C) and good oxygen balance (+ 19.69 %), but high acidity (pKa = 2.35) of its NH bond precludes practical applications. In this proposal, we will synthesize advanced energetic materials based on 3,5-dinitropyrazoles. Energetic and physical properties will be controlled (i) depending on the substituent (-NH2, -OH, N3, -NO2, etc.) on the 4th position of the pyrazole ring, (ii) N-functionalization to remove the acidic NH and connect 3,5-dinitropyrazoles with other energetic heterocyclic rings like tetrazole, tetrazole N-oxide, nitroimino(oxadiazole), nitrotriazole, dintitromethane, etc. The energetic and physical properties of the resulting neutral compounds will be further fine-tuned by energetic salt formations.