Hydrogen-Bonded Ammonium Dinitramide/Dibenzo-[18]-Crown-6 Cocrystal with Low Hygroscopicity and Reduced Sensitivity

Abstract

Dibenzo-[18]-crown-6 (DB18C6) was used to form a novel cocrystal with ammonium dinitramide (ADN) via solvent evaporation under controlled temperature and humidity conditions to accelerate cocrystallization and reduce hygroscopicity. Single-crystal X-ray diffraction was applied for the validation of the ADN/DB18C6 cocrystal structure. This cocrystal’s formation is primarily due to robust intermolecular hydrogen-bonding interactions mediated by the ammonium ions of ADN and the oxygen atoms present in the crown ether rings. In comparison to the individual components, the ADN/DB18C6 cocrystal shows an increased melting point (173 °C), which significantly exceeds those of ADN (90 °C) and DB18C6 (164 °C), suggesting enhanced thermal stability. Furthermore, under conditions of 30 °C with 60% relative humidity for a duration of 12 hours, the hygroscopicity of the ADN/DB18C6 cocrystal is noticeably reduced compared to that of pristine ADN. The moisture adsorption decreases from 20.60% for ADN to only 1.29% for the cocrystal. Tests for impact and friction sensitivity further reveal that the ADN/DB18C6 cocrystal has an impact sensitivity of 10 J, which is a bit elevated compared to that of raw ADN at 7.5 J, while its friction sensitivity exceeds 360 N, which is considerably greater than ADN’s 84 N, thus significantly improving safety during the handling and storage of energetic materials. In summary, these findings show that cocrystallization serves as a successful approach for tuning and enhancing ADN’s physicochemical characteristics, offering a feasible means to improve the safety and usability of ADN-based energetic materials.