Preparation And Characterization Of Cocrystal Explosives Based On Non-covalent Intermolecular Interactions

It is well documented that cocrystallization offers great potential todramatically alter many of the physicochemical properties of energetic materials.The formation of cocrystal explosives can make an alteration of key propertiesincluding density, melting point, oxygen balance and decomposition temperatureas compared with their co-formers. Cocrystallization is a novel and intriguingmethod to solve the contradiction between the high-energy and insensitive, andprovides an important role in changing explosives performance.In this paper,11cocrystal explosives were prepared by solvent evaporationmethod. X-ray diffraction was used to analysis the crystal structure of the sevenkinds of cocrystal, and the formation of cocrystal were verified by the powderX-ray diffraction, infrared and differential scanning calorimetry. In addition, theexplosive performance and the formation mechanism of cocrystal were studied anddiscussed, which has a guiding role in the design and preparation of the furthercocrystal explosives. The obtained cocrystals main divided into three series,namely TNT/TNB, the BTF series and CL-20series. Besides, the crystal ofMeNQ/H2O was obtained during the preparation of the cocrystal explosives. Themain research results obtained are summarized as follows:(1)TNT/TNB: The TNT/TNB cocrystal with a1:1molar ratio was prepared.The formation of cocrystal is mainly relying on donor-acceptor π-π interaction,p-π interactions and C-H...O hydrogen bonding interactions. It was found that themelting point of cocrystal is62℃, and the lower melting point can makes it beused in conjunction with TNT as cast explosives mobile phase to improve thecasting process.(2) BTF series: The molar ratios of1:1BTF cocrystal explosives wereprepared. Those cocrystals have similar density with RDX, and the sensitivity ofBTF/TNT, BTF/TNP and BTF/TNB cocrystal was lower than that of BTF, whichproved that the co-crystallization can be used to reduce the sensitivity of BTF.The single crystal structures of the five kinds of cocrystal have been studiedand discussed, and further use of the infrared spectrum to verify the interactionbetween co-formers. The formation of5BTF cocrystals mainly rely on the p-πstacking interactions, the hydrogen bonds interactions between adjacent molecules as well as π-π interaction. This indicates that there is some regularity in theformation of cocrystal, and perhaps these explosives, which have relativelyelectron-rich group, can formation cocrystal with BTF. This provides a referencefor the design and preparation of future cocrystal explosives.(3) CL-20Series: three CL-20cocrystals were prepared by rotary evaporationmethod, and further use of the XRD, DSC, IR and other methods to determine theformation of cocrystal. The crystal structure of CL-20/CPL was analyzed, and it isfound that the formation of cocrystal is resulted by intermolecular hydrogen bondinteraction. The formation mechanism and influencing factors of cocrystalformation were studied and discussed. It shows that the water in the air has aprofound effect on the cocrystal format ion, and it can lead to crystalform conversion of C L-20, but not the formation of cocr yst al.(4) MeNQ/H2O: A molar ratio of1:1MeNQ/H2O crystal was obtained in thepreparation process of cocrystal explosives. Heating XRD, simultaneous thermalanalysis and warming IR were used to characterize the formation of MeNQ/H2Ocrystal.