Syntheses, Crystal Structures, and Properties of Two Novel CL-20-based Cocrystals

In recent years, cocrystallization has emerged as an effective way of tuning the properties of compounds and has been widely used in the field of energetic materials. In this study, we have prepared two novel cocrystals of CL-20 and methylimidazole, including a 1:2 CL-20 / 2-mercapto-1-methylimidazole (1) and a 1:4 CL-20 / 4-methyl-5-nitroimidazole (2). Cocrystal 1 has good physical and detonation properties (ρ ₁ = 1.652 g·cm ^–3 , D ₁ = 7073 m·s ^–1 , P ₁ = 21.6 GPa); however, cocrystal 2 shows higher properties (ρ ₂ = 1.680 g·cm ^–3 , D ₂ = 7945 m·s ^–1 , P ₂ = 27.4 GPa). The performance of both cocrystals is better than those of TNT. Thermal performance suggests that both the cocrystals have moderate thermal stabilities. Cocrystal 1 decomposes at 164.9 °C and cocrystal 2 has an exothermic peak at 221 °C. Both cocrystals are insensitive energetic explosives (IS > 40 J, FS > 360 N). Methylimidazole compounds are rarely used as coformers to form cocrystals with CL-20, which possess good properties for a range of potential applications. Herein, we provide new possible directions for enriching cocrystal speciation.