Developing energetic materials that combine high thermal stability, strong detonation performance, and low sensitivity remains a challenge in advanced explosive chemistry. While conventional heat-resistant explosives such as HNS and TATB exhibit excellent thermal resistance, they often have limited energetic performance or complicated synthesis routes involving hazardous organic solvents.
In a recent study published in Energetic Materials Frontiers , researchers from China Academy of Engineering Physics developed a facile one-step aqueous synthetic strategy for constructing fused azole–pyrimidine energetic materials based on azole-6-nitro-[1,5-a]pyrimidine building blocks. By employing water as the reaction medium, the method provides an environmentally friendly route toward high-performance heat-resistant energetic compounds.
"The development of energetic compounds with exceptional thermal stability has emerged as a leading research focus in the field of energetic materials," explains corresponding author Qing Ma. "Eco-friendly synthetic strategies constitute a viable and effective approach for the development of advanced energetic materials."
The researchers synthesized a series of fused energetic compounds through reactions between commercially available aminoazoles and sodium nitromalonaldehyde in water at moderate temperatures. "The resulting compounds were obtained in high yields through a straightforward aqueous synthesis process without relying on complex organic solvent systems," Ma says.
Among more than ten synthesized materials, one exhibited particularly balanced energetic and thermal properties. "The compound, designated as Compound 6, achieved a density of 1.76 g·cm⁻³, a decomposition temperature of 316 °C, a detonation velocity of 7824 m·s⁻¹, and a detonation pressure of 23.9 GPa, performance levels comparable to the conventional heat-resistant explosive HNS," shares Ma.
Thermal analysis further revealed that another compound (Compound 5) possessed an even higher decomposition temperature of 333 °C, exceeding that of HNS. Differential scanning calorimetry showed that three compounds, including 5 and 6, maintain excellent thermal resistance due to extensive intermolecular hydrogen bonding, π–π stacking interactions, and highly conjugated fused-ring structures.
"Single-crystal X-ray diffraction analysis demonstrated that the fused azole–pyrimidine frameworks exhibit highly planar molecular structures and ordered crystal packing arrangements," adds Ma. "Strong intermolecular hydrogen bonding and layered π–π stacking interactions contribute significantly to molecular stability and reduced mechanical sensitivity."
Sensitivity measurements showed that Compounds 4 and 5 possess impact and friction sensitivities substantially lower than those of TNT and HNS. "Even Compound 6, despite slightly higher sensitivity, retained comparable safety characteristics relative to analogous energetic materials," notes Ma.
Further Hirshfeld surface analysis and electrostatic potential calculations revealed that hydrogen bonding networks and intermolecular atomic contact distributions play critical roles in regulating thermal stability and sensitivity. The researchers found that fused azole–pyrimidine rings generate extensive noncovalent interactions that reinforce structural robustness under thermal stress.
"We demonstrated that environmentally friendly aqueous synthesis can provide an efficient route toward advanced heat-resistant energetic materials without sacrificing energetic performance," says Ma. "The universal nitropyrimidine construction strategy established may serve as a general methodology for designing future fused-ring energetic compounds with integrated thermal stability, low sensitivity, and high energy density."
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Contact the author:
National Key Laboratory of Chemical Explosion Safety, Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, 621999, China
( qingma@caep.cn&mattqing@126.com )
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Energetic Materials Frontiers
A facile one-step aqueous synthetic strategy for fused azole–pyrimidine heat-resistant energetic materials
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.