Development and Evolution of Energetic Cocrystals

Abstract

Conspectus In spite of the importance of energetic materials to a broad range of military (munitions, missiles) and civilian (mining, space exploration) technologies, the introduction of new chemical entities in the field occurs at a very slow pace. This situation is understandable considering the stringent requirements for cost and safety that must be met for new chemical entities to be fielded. If existing manufacturing infrastructure could be leveraged, then this would offer a fundamental shift in the discovery paradigm. Cocrystallization is an approach poised to realize this goal because it can use existing materials and make new chemical compositions through the assembly of multiple unique components in the solid state. This account describes early proof-of-principle studies with widely used energetics in the field, including 2,4,6-tri­nitrotoluene (TNT) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), forming cocrystals with nonenergetic coformers that alter key properties such as density, sensitivity, and morphology. The evolution of these studies to produce cocrystals between two energetic components is detailed, including those exploiting new intermolecular interaction motifs that drive assembly such as halogen bonding. Implications of cocrystallization for performance, sensitivity to external stimuli, and manufacturability are explored at each stage. The derivation of many of these cocrystals from energetic materials in common use satisfies the goal of using materials already demonstrated to be cost-effective at scale and with well-understood safety profiles. The account concludes with a discussion of cocrystallizing molecules having excess of oxidizing power with those that are oxygen-deficient to push the limits of explosive performance to unprecedented levels. The purposeful production of an arbitrary combination of two solid components into a cocrystal is far from certain, but the studies described motivate the continued exploration of novel materials and the development of predictive models for identifying crystallization partners. When such cocrystals form, many of their most important properties cannot be predicted, pointing to another challenge for the purposeful development of energetic materials based on cocrystallization.

Optimized energetic HNTO/AN co-crystal and its thermal decomposition kinetics in the presence of energetic coordination nanomaterials based on functionalized graphene oxide and cobalt

“…The pre-exponential factor is estimated by using the CE by a single heating rate method in the succeeding correlation eqn (20):…”

“…[17][18][19] Several energetic co-crystals with interesting features have been developed so far and the topic continues to attract current/future and increasingly intense international discussion to fulll the requirement of the next generation of EMs. [20][21][22] As one of the most interesting propellant oxidizer and explosive ingredient, AN displays prominent characteristics such a positive oxygen balance, low cost, availability, and 100% of gaseous decomposition products. 23 Nonetheless, AN exhibits unneglectable shortcomings such as low energy rate, poor ignitability, lower burning rate, high hygroscopicity, and an ambient temperature polymorphic solid-solid phase transition, acknowledged as one of the foremost reason for damaging and caking of AN-based energetic formulations, which inhibits its extensive employments, particularly as solid-propellant ingredient.…”

First and Second Dissociation Enthalpies in Bi-Component Crystals Consisting of Maleic Acid and L-Phenylalanine

“…Multi-component organic crystals have been known of since at least 1844, when Wöhler synthesized quinhydrone from p -quinone and hydroquinone [ 1 ]. Interest in these materials was renewed in recent years, after it was widely recognized that the incorporation of two or more different molecules in the same crystal could open a variety of opportunities for product innovation [ 2 ] and patenting [ 3 ] in industrial sectors such as dyes [ 4 ], agrochemicals [ 5 ], optics [ 6 , 7 ], energetic materials [ 8 , 9 , 10 ], and pharmaceuticals [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Thus, for example, energetic materials made of bi-component crystals with better stability than their individual precursors have been reported [ 8 , 9 , 10 ], and medicines based on bi-component crystals (API-CF) consisting of an active pharmaceutical ingredient (API) and a pharmaceutically acceptable co-former (CF) or two APIs (API–API) have been marketed or are in clinical development [ 19 , 20 ].…”

“…Interest in these materials was renewed in recent years, after it was widely recognized that the incorporation of two or more different molecules in the same crystal could open a variety of opportunities for product innovation [ 2 ] and patenting [ 3 ] in industrial sectors such as dyes [ 4 ], agrochemicals [ 5 ], optics [ 6 , 7 ], energetic materials [ 8 , 9 , 10 ], and pharmaceuticals [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Thus, for example, energetic materials made of bi-component crystals with better stability than their individual precursors have been reported [ 8 , 9 , 10 ], and medicines based on bi-component crystals (API-CF) consisting of an active pharmaceutical ingredient (API) and a pharmaceutically acceptable co-former (CF) or two APIs (API–API) have been marketed or are in clinical development [ 19 , 20 ]. In the pharmaceutical area, where the main driving force for research on multi-component crystals currently resides, the goal is typically the improvement and modulation of properties that need to be strictly controlled to warrant the optimal and reproducible performance of a drug (e.g., chemical and physical stability, tabletability, hygroscopicity, solubility, dissolution rate, bioavailability) [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], or the achievement of multimodal therapy [ 21 , 22 ].…”

Tetrazole‐Based Energetic Metal‐Organic Frameworks: Impacts of Metals and Ligands on Explosive Properties

“…[15] The dense packing is primarily due to diverse coordination modes between Tz and metals. [16] Interestingly, the densely-packed structures are desirable in energetic application, [17][18][19] where the arrangement of nitrogen-rich, energetic molecules like Tz plays a crucial role in modulating the explosive and safety properties (e. g. detonation performance and sensitivity). [20][21][22] Such metal-organic hybrid systems have unique advantages over traditional energetic materials, such as trinitrotoluene (TNT), cyclotrimethylene trinitramine (RDX), and cyclotetramethylene tetranitramine (HMX) as shown in Figure 1a.…”