A Novel Strategy for Preparing the Superior Performance Solid Form of Energetic Materials Based on Rapid In-Situ Solvate-Mediated Phase Transformation Mechanism

Abstract

Using energetic materials (EMs) products with impure solid forms in practical application scenarios will lead to a series of serious consequences in terms of safety, mechanics, storage, detonation, and reliability properties. A novel approach to obtain the scarce and superior performance solid form of EMs was developed by the strategy of rapid in-situ solvate-mediated phase transformation, which is a promising and convenient method because of avoiding additional desolvating under specific external conditions and greatly reducing the risks in the production of EMs. In this strategy, the low sensitivity and highly energetic material 4,4′,5,5′-tetranitro-1H,1′H-[2,2′-biimidazole]-1,1′-diamine (DATNBI) was used as a model substance and its α-DATNBI that is hard to gain but with better performance was successfully prepared. Furthermore, a mechanism of this solvate-mediated method was studied by exploring the types of solute clusters and intermolecular interaction of DATNBI in the microscopic view. These molecular assembly modes were determined in solid and solvents employing X-ray diffraction and in-situ micro-Raman technique, as well as attenuated total reflectance-Fourier transform infrared spectra combined with density functional theory calculation, respectively. It is found that solute molecules tend to exist as solvated monomers resulting in the prior precipitation of solvate in saturated solution of THF. From the perspective of crystal structure and transformation energy, the solvates consisting of DATNBI and THF can easily transform to the scarce α form of DATNBI. This study proposes a new practical strategy for a specific solid form mediated by solvates-mediated phase transformation, which is particularly beneficial for the preparation of high-purity solid forms of EMs with better energy and safety properties but also helps us to understand the key role of solvates in the polymorph formation.

Keywords: energetic materials, Solvates mediated, Phase transformation, In-situ preparation, Polymorphism