Preparation, structure, and main properties of bimolecular crystals CL-20—DNP and CL-20—DNG

Crystal Growth & Design

Wang

et al. 2020

A new 1:3 CL-20 (2,4,6,8,10,12-hexanitrohexaazaisowurtzitane)/4,5-MDNI (1-methyl-4,5-dinitroimidazole) cocrystal (1) in combination with the previously reported 1:1 CL-20/4,5-MDNI cocrystal (2) together have been first realized in different stoichiometric ratios based on CL-20 and 4,5-MDNI in energetic−energetic cocrystals. Subtle differences in intermolecular interactions and packing motifs may lead to the formations of the cocrystals 1 and 2 by structure comparisons. Moreover, properties (e.g., density, thermal properties, sensitivity, and detonation performances) varied significantly under different stoichiometric ratios and crystal structures. For instance, the comprehensive performances of cocrystal 1 (ρ: 1.813 g/cm 3 ; D: 8604 m/s, P: 34.45 GPa; IS: 16 J) were less excellent than those of cocrystal 2, whereas cocrystal 1 exhibited a detonation velocity superior to that of LLM-105 (2,6-diamino-3,5-dinitropyrazine-l-oxide, a relatively new insensitive explosive) and a low impact sensitivity close to that of LLM-105; thus, cocrystal 1 may act as a new high-energy insensitive explosive. Moreover, the findings of CL-20/4,5-MDNI cocrystals may offer new insights into the design and preparation of energetic cocrystals with different ratios and other energetic cocrystals, enrich better understanding of the formations for energetic cocrystals, and provide a smart strategy to tune performances.

Section: Introductionmentioning

confidence: 99%

Different Stoichiometric Ratios Realized in Energetic–Energetic Cocrystals Based on CL-20 and 4,5-MDNI: A Smart Strategy to Tune Performance

Tan

Crystal Growth & Design

Wang

et al. 2020

“…In addition, an interesting phenomenon is that multiple conformers of CL-20 or HMX are found in EMCCs. The CL-20-based EMCCs possess the largest population among the observed EMCCs except for a large quantity of energetic solvates of HMX. ,,,− This can be attributed to the remarkable detonation performance, while the rather high sensitivity requires an improvement of CL-20 itself. With regard to the molecular structure of CL-20, its cage frame is rigid, while its nitro groups can be swung readily, giving it a certain flexibility to implement the conformational transformation. , With respect to the CL-20 molecules in CL-20-based EMCCs, five types of conformers are found, including β, γ, η, ε, and ζ forms (Figure ).…”

Section: Intermolecular Interactions In Emccsmentioning

confidence: 99%

Review of the Intermolecular Interactions in Energetic Molecular Cocrystals

Crystal Growth & Design

Wei

Zhang

2020

Energetic cocrystallization is thriving now and presents a promising perspective to create new energetic materials (EMs). In comparison with the single-component EMs, the creation of energetic cocrystals exhibits a greater significance of crystal engineering, whose central scientific issue is intermolecular interaction. This article reviews the current progress in studying the intermolecular interactions of energetic molecular cocrystals (EMCCs), as well as the molecular stacking and the thermodynamics for EMCC formation. The intermolecular interactions include hydrogen bonding (HB), π interactions, and halogen bonding. The strength of these interactions is found to be generally weak, similar to that of single-component energetic molecular crystals. By means of cocrystallization, the molecular stacking can be improved to be prone to layered stacking, facilitating low impact sensitivity. This could be feasible for alleviating the energy−safety contradiction of EMs. The driving force of the EMCC formation is thought to be the increase in entropy, because the EMCCs are in nature the products of an increase in randomness, with a small variation of intermolecular interactions in comparison with original pure components. Finally, the dependence of the properties of EMCCs on the compositions and molecular structures of original pure components is proposed to attract increasing attention, as it is a base for creating new EMs with tunable compositions, structures, and properties by way of crystal engineering.

“…Expectedly, the safety performance can be improved dramatically after cocrystalization compared with that of raw CL-20 and HMX. Combining experimental detonation velocity (9000 m/s for 1 c [46] and 8712 m/s for RDX [47]) and mechanical sensitivity, it is strongly suggested that the comprehensive performance of 1 c significantly outperforms traditional high explosive RDX. Therefore, the following properties: (a) high detonation performance; (b) moderate mechanical sensitivity; (c) good thermal stability; (d) rapid, high-yielding, and scale-up of preparation highlight 1 c as a suitable replacement for commonly used high explosives.…”

Section: Thermal and Sensitivity Propertiesmentioning

confidence: 99%

Rapid and High‐Yielding Formation of CL‐20/DNDAP Cocrystals via Self‐Assembly in Slightly Soluble‐Medium with Improved Sensitivity and Thermal Stability

Propellants Explo Pyrotec

Duan²,

et al. 2019

In this study, the energetic 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane/2,4‐dinitro‐2,4‐diazapentane (CL‐20/DNDAP) cocrystals were successfully fabricated via an efficient self‐assembly strategy. The formation processes of CL‐20/DNDAP cocrystal in solvents of H2O, H2O/methyl acetate, and 2‐propanol have been investigated by using the powder X‐ray diffraction (PXRD) qualitative/quantitative analysis and scanning electron microscopy (SEM). Both theoretical and experimental studies confirmed that the most satisfying results can be achieved by using 2‐propanol at 30 °C with crystallization time of 2 h, with a high yield up to 98.2 %. The addition of sodium dodecyl benzene sulfonate (SDBS) is effective in controlling its morphology with a narrow size distribution. Furthermore, the cocrystal exhibits better thermal stability and improved mechanical sensitivity compared with the one prepared by spray drying method. This work provides a simple and convenient approach for the preparation of energetic cocrystals, and the CL‐20/DNDAP cocrystal with high energy and low sensitivity is desirable for various applications.