Synthesis and Characterization of an Azido Nitrofurazanyl Ether: An Energy-Rich Heterocyclic Plasticizer with a Low Glass Transition Temperature

We report on the synthesis and characterization of 3-(2-(2-azidoethoxy)ethoxy)-4-nitro-1,2,5-oxadiazole (NFPEG2N3), which is a liquid nitrofurazanyl ether that was designed to be an energy-rich plasticizer for glycidyl azide polymer (GAP)-and nitrocellulose (NC)-based formulations. NFPEG2N3 was obtained from 3,4-dinitrofurazan (DNF) via nucleophilic substitution with lithium 2-(2-azidoethoxy)ethanolate. It was then characterized using 1 H and 13 C NMR, Infrared (IR), Raman, elemental analysis (EA), and density measurement (ρ = 1.375 g/cm 3). The experimental IR bands were assigned with the help of DFT (B3LYP/6-31G*) calculations. Composite methods (CBS-QB3, G4MP2, and G4) were used to determine the enthalpy of formation. NFPEG2N3 exhibits a glass transition temperature (T g) of -74.9 • C, a thermogravimetric analysis mass-loss midpoint of 156 • C, and a closedcrucible differential scanning calorimetry exotherm onset at 186 • C. Among the comparators Bu-NENA and BDNPA/F, it shows the highest enthalpy of formation (164 kJ mol -1) and heat of explosion (4024 J g -1). Blending with GAP diol significantly improves processability. Viscosity at 20 • C decreases from 4560 mPa⋅s (pure GAP) to 1369 mPa⋅s at a 20 wt.% NFPEG2N3 content. Meanwhile, the mixture's T g decreases from -49.4 to -53.5 • C at a 10 wt.% NFPEG2N3 content. Thermodynamic analyses indicate that NFPEG2N3 in NC systems raises the specific energy while keeping the temperature of explosion moderate, with an optimum near 20 wt.% plasticizer content. In GAP/AP/HMX composite propellants, NFPEG2N3 increases the volume-specific impulse and delivers the highest mass-specific impulse at 5-10 wt.% compared to Bu-NENA and BDNPA/F. These results identify NFPEG2N3 as a promising energetic plasticizer that combines effective rheological modification with enhanced energetic performance.