Preparation Of Two Cocrystal Explosives And Molecular Dynamics Simulation

The cocrystal technology of energetic materials combines explosive molecules with the same crystal lattice through intermolecular hydrogen bonds,van der Waals forces,and halogen bonds to achieve the adjustment of explosive energy and sensitivity.2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclododecane（CL-20）is currently one of the highest energy in secondary explosives.CL-20 has the disadvantage of high mechanical sensitivity,which limits the application of CL-20.To this end,this dissertation uses cocrystal technology to modify CL-20 to improve the its safety.In this paper,the structural characteristics and functional groups of CL-20 were analyzed and then 2,4,6-trinitroresorcinol（TNR）and 1,1-diamino-2.2-dinitroethylene（FOX-7）were selected as the ligands of CL-20 co-crystal.The feasibility of forming a co-crystal between CL-20 and TNR or FOX-7 was discussed with the molecular structure using Materials Studio（MS）software.Through the radial distribution function simulation analysis,it is shown that the two co-crystals have hydrogen bonding and van der Waals effect.The binding energy simulation analysis shows that the binding energy of the cocrystal system is significantly higher than that of the blend explosives.It is possible that non-covalent bond interactions have occurred between the molecules in the cocrystal explosive.Therefore,it can be theoretically explained that a co-crystal can be formed betweenε-CL-20/TNR andε-CL-20/FOX-7by a non-covalent bond force.For theε-CL-20/TNR system,the solvent evaporation method is adopted as the cocrystal preparation method.It is optimized to prepareε-CL-20/TNR under the solvent volatilization method using ethyl acetate/ethanol mixed solvent as the solvent,the temperature 35°C,andε-CL-20/TNR 1:1 molar ratio.The powder XRD test results showed thatε-CL-20/TNR co-crystals had obvious new peaks at 12.0°and43.0°,and the main peaks of the raw material components were weakened.The infrared spectra showed that-OH of TNR and the stretching vibration of NO₂ofε-CL-20 changed,which indicated that the molecular interaction.Meanwhile the results of thermal decomposition and thermal weight loss tests showed that the thermal decomposition of the cocrystal are different from the raw material components.The XRD,infrared spectra and thermal decomposition results indicated cocrystal production.For theε-CL-20/FOX-7 system,the vacuum freeze-drying method,solvent-antisolvent method and interface method were used to study the preparation ofε-CL-20/FOX-7 co-crystal explosives.Finally,under the conditions of the solvent-antisolvent method,DMSO was selected as the solvent,water as the antisolvent,the experimental temperature 25°C.and the molar ratio of the feed was1:1 to prepare a co-crystal.Under the conditions of vacuum freeze-drying method,DMSO was selected as the solvent,the experimental temperature was-45°C and the molar ratio of the feed was 1:1 to prepare a co-crystal.For the sample prepared with these two conditions,the new diffraction peaks at 7.83°and 25.8°appeared in the powder XRD data while the two original XRD peaks disappeared.At the same time,the infrared spectrum and thermal analysis had obvious changes.These results indicated the new cocrystal generation.With the interface method,DMF and ethanol were selected as two-phase solvents,and the experimental conditions were optimized as temperature 20°C and the molar ratio 1:1 to prepare the cocrystal.XRD analysis showed that there was no cocrystal generation under this condition.The research work in this paper provides specific guidance for the preparation of two energetic co-crystals and single crystal cultivation.It can also provide a reference for the preparation and screening of other energetic co-crystals.