Weak Interaction-Driven Self-Assembly of Low-Hygroscopicity Oxidizers for Biocidal Nanoenergetic Materials with Favorable Ignition Performance

Abstract Iodine pentoxide (I2O5) features a high elemental iodine content, and the composite materials formed with nano-aluminum (n-Al) exhibit both high reactivity and abundant gas generation. However, the n-Al/I2O5 system suffers from a long ignition delay and strong hygroscopicity of I2O5. In this work, a novel iodine-rich energetic oxidizer, [C2H10N2](H2I3O9)2 (EAI-2), was designed and synthesized via weak interaction-driven self-assembly, achieving an ultralow hygroscopicity of ≤0.06% and a high iodine content of 68.26%. Single-crystal X-ray diffraction revealed that the supramolecular architecture was stabilized by cooperative halogen bonds (I···O) and hydrogen bonds (N−H···O). These cooperative interactions effectively shielded the samples from moisture adsorption. Three n-Al/EAI-2 composites were prepared via physical mixing (PM), cooling crystallization (CC), and spray antisolvent (SA) methods. Systematic characterizations demonstrated that the preparation method profoundly affected the crystal morphology, interfacial contact, and mixing uniformity of the composites. SA-n-Al/EAI-2 exhibited the most intimate interfacial contact, attributed to the rapid nucleation and constrained crystal growth during the antisolvent-induced precipitation. Consequently, SA-n-Al/EAI-2 displayed superior sensitivity performances, with an impact sensitivity of >30 J, a friction sensitivity of 108 N, and a flame sensitivity of 7.9 cm, outperforming CC-n-Al/EAI-2. The ignition delay of SA-n-Al/EAI-2 (337.6 ms) was significantly shorter than that of n-Al/I2O5 (1039.6 ms) and PM-n-Al/EAI-2 (946.7 ms), demonstrating the critical role of interfacial engineering in energy release behavior. This study elucidates the relationship between crystallization methodology, supramolecular structure, and energetic performance, providing a crystal-engineering strategy for the design of advanced nano-thermites.