Theoretical investigations on stability, sensitivity, energetic performance, and mechanical properties of CL-20/TNAD cocrystal explosive by molecular dynamics method

Molecular dynamics simulation of TNT/PYRN cocrystal PBXs

CONTEXT

The ternary eutectic system comprising trinitrotoluene (TNT) and pyranidine (PYRN) exhibits potential as a moderate-energy explosive compound characterized by reduced sensitivity. Recently, this composition can be a suitable alternative to TNT in the development of low-vulnerability explosive formulations, thus providing a promising alternative for future applications in the field of energetic materials. However, the changes in the structure and properties of eutectic explosives and their intrinsic causes for these changes have been rarely explored. Here, we construct a theoretical model of the TNT/PYRN eutectic system and integrates a diverse array of polymer additives, including butadiene rubber (BR), ethylene-vinyl acetate copolymer (EVA), polyethylene glycol (PEG), fluorinated polymer (F2603), and polyvinylidene fluoride (PVDF), into five distinct cleavage planes ((1 0 0), (0 1 0), (0 1 - 1), (1 0 0), and (1 0 - 1)) within the eutectic matrix. We found that the synthesis of polymer-bonded explosives (PBXs) is achieved through the integration of the aforementioned polymers into the TNT/PYRN eutectic system. This investigation elucidated the influence of various polymer matrices on the structural integrity, critical bond distances for initiation, mechanical attributes, and detonative behavior of the resultant PBXs. Within the corpus of five PBX models examined, the TNT/PYRN/F2603 configuration showed the supremum in binding energetics and the infimum in critical bond lengths, which portends superior stability, interfacial harmony, and a minimized propensity for unintended initiation. Furthermore, the TNT/PYRN/F2603 system was delineated by its enhanced capability for explosive initiation. Note importantly that the TNT/PYRN/F2603 model exhibited pre-eminence in its aggregate performance metrics, corroborating the hypothesis that F2603 constitutes a preferential binder candidate for PBX formulations predicated on the TNT/PYRN eutectic composite.

METHODS

Utilizing the Materials Studio computational platform, the physicochemical attributes of the TNT/PYRN eutectic-based polymer-bonded explosives (PBXs) were anticipated via molecular dynamics (MD) simulations. The MD protocol was executed with a temporal increment of 1 fs, encompassing an aggregate simulation span of 2 ns. An isothermal-isobaric (NPT) thermodynamic ensemble was employed for the duration of the 2 ns MD trajectory. The COMPASS empirical force field was utilized to model interatomic interactions, and the thermal parameter was maintained at a constant 295 K throughout the simulation campaign.

Design of Coamorphous Systems for Flavonoid Components Coformed with Meglumine by Integrating Theory-Model-Experiment Techniques

Flavonoids represent an extensive group of phenolic substances in vegetables, fruits, grains, tea, flowers, etc., which show a variety of biological activities in various nutraceutical, cosmetic, and medicinal fields. Despite demonstrating multifunctional bioactive properties relevant to nutraceutical and pharmaceutical applications, their clinical utilization faces challenges due to their generally low water solubility. This study established a systematic methodology combining computational modeling and experimental validation for developing flavonoid-meglumine (MEG) coamorphous formulations. The initial screening identified 13 flavonoid compounds exhibiting favorable miscibility with MEG from 15 candidates through Hansen solubility parameter analysis. Subsequent molecular dynamics simulations revealed potential hydrogen bond formation in six selected flavonoids (BAI, HES, NAR, KAE, QUE, and ISO) with MEG. Then, six flavonoid coamorphous systems were successfully prepared via the melt-quenching method and characterized by PLM, PXRD, and differential scanning calorimetry. FTIR and radial distribution function analysis results collectively confirmed intermolecular hydrogen bond interactions within these binary systems. In vitro dissolution studies revealed significant solubility/dissolution enhancement in both pH 1.2 HCl and pH 6.8 phosphate buffers, maintaining long-term supersaturation for all six coamorphous formulations. Meanwhile, six flavonoid coamorphous systems had superior stability over individual flavonoid amorphous components, which were attributed to the stronger intermolecular interactions by higher binding energy calculation. These results indicated that the obtained flavonoid coamorphous systems performed a promising application potential in functional products. Importantly, this study presents a novel design framework integrating computational prediction, molecular modeling, and experimental validation for systematic screening of flavonoid coamorphous formulations.

A New Screening Strategy for Flavonoid Components to Obtain a Satisfactory Co-Amorphous System with Piperine

Flavonoids are a large class of compounds with a variety of biological activities. Nevertheless, their therapeutic application remains limited due to the generally low water solubility. In the present study, an integrated approach was provided to guide the design of flavonoid co-amorphous systems co-formed with piperine (PIP). Firstly, 7 flavonoid compounds showed good miscibility with PIP from 13 flavonoid candidates. Then, molecular dynamics simulation confirmed hydrogen bond formation between 5 flavonoid compounds (i.e., BAI, HES, ISO, NAR and KAE) and PIP. Herein, 5 flavonoid compounds were successfully co-amorphized with PIP by the melting and quench cooling method, which were proved via PLM, PXRD and DSC measurements. FTIR results showed the potential hydrogen bond interactions between -OH of flavonoid molecules and C = O of PIP molecule in the formed co-amorphous systems, which were consistent with RDF analyses in molecular models. For dissolution tests, 4 co-amorphous systems (i.e., BAI-PIP CM, HES-PIP CM, ISO-PIP CM and NAR-PIP CM) appeared abnormally reduced dissolution compared to their original crystalline counterparts arising from the formation of gels during dissolution, while only KAE-PIP CM displayed significantly enhanced dissolution (5.83-fold of crystalline KAE at 12 h) with long-time supersaturated concentration. Meanwhile, KAE-PIP CM kept physically stable at least 3 months under 25°C and 40°C conditions, and possessed excellent physical stability over individual amorphous components, which was attributed to the stronger intermolecular interaction by higher binding energy analysis. Therefore, this study provides a design strategy to guide the screening of flavonoid co-amorphous systems through combining theory-model-experiment techniques.

Molecular dynamics simulation of CL-20 based high temperature resistant PBX

CONTEXT

To address the issue that the output charge in existing Deflagration to Detonation Transition (DDT) detonators cannot withstand high temperatures of 200 °C, and to improve the output performance of the detonator, a CL-20 (Hexanitrohexaazaisowurtzitane) based polymer bonded explosive (PBX) was investigated as the primary charge material for the detonator. To select the most suitable binder for thermal resistance, molecular dynamics (MD) simulations were employed to evaluate the performance of different binders at various crystal planes and temperatures. The results indicate that among the five PBXs models, CL-20/F2602 exhibits the highest binding energy and the shortest bond initiation length at both ambient and elevated temperatures. CL-20/F2611 demonstrates stronger hydrogen bonding interactions and superior thermal stability at high temperatures. CL-20/PCTFE shows the best ductility, while CL-20/F2602 possesses the second-best ductility. Therefore, PBXs containing F2602 possess the best stability, compatibility, and satisfactory ductility, while PBXs with F2611 exhibit the best thermal stability. Both F2602 and F2611 are suitable as binders for CL-20.

METHODS

Molecular dynamics (MD) simulations were carried out using the Materials Studio software to calculate the binding energies, trigger bond lengths, and mechanical properties of five PBX models at different crystal planes at 298 K, and at various temperatures on the (0 1 1) crystal plane after a 1 ns NPT dynamics simulation. The total MD simulation time was 1 ns, with a time step of 1 fs, and the COMPASS force field was employed throughout the simulation.

Cocrystal screening of benznidazole based on electronic transition, molecular reactivity, hydrogen bonding, and stability

CONTEXT

Screening of cocrystals of active pharmaceutical ingredients is important in the development of pharmaceutical compounds because it improves bioavailability, stability, solubility, and many other physicochemical properties. In this work, quantum chemical calculations were utilized for the computational evaluation of the cocrystal screening of benznidazole (BZN) API via hydrogen bonding with four coformers (maleic acid, malonic acid, oxalic acid, and salicylic acid), and they contain carboxylic groups. The nitrogen of the imidazole ring in benznidazole and the carboxylic group of the coformer form a hetero-synthon connected by a strong hydrogen bond. The strength of the hydrogen bonding interaction O-H…N was measured using various tools. It was found that in comparison to BZN cocrystals with malonic acid, oxalic acid, and salicylic acid, the O-H…N interaction in the BZN-maleic acid cocrystal had higher interaction energy, indicating it had stronger hydrogen bonding. The strength of the hydrogen bond O-H…N for synthons was discovered to be more beneficial than the C-H…O interaction, as confirmed by ESP analysis. The BZN-salicylic acid cocrystal was found to be more reactive and polarizable, whereas the BZN-malonic acid cocrystal was more stable. Cocrystals of benznidazole exhibited better physicochemical characteristics than API benznidazole, as indicated by electron transition properties between the most significant orbitals.

METHODS

The computational evaluation for the screening of benznidazole cocrystals was performed in Gaussian 16 software using density functional theory (DFT) with the hybrid functional B3LYP and the basis set 6-311 +  + G(d,p). The UV-Vis absorption spectrum in solvent water was analyzed using the TD-DFT/6-311 +  + G(d,p) method to determine the influence of the solvent in cocrystals using a polarizable continuum model. The strength of the hydrogen bonding interactions O-H…N in each of those mentioned cocrystals was used to screen the cocrystals using tools such as thermodynamic probability, ESP analysis, QTAIM analysis, and NBO analysis. The pairing energy of interaction was measured by determining H-bond donor ( α max ) and H-bond acceptor( β max ) parameters for hydrogen bonds from maxima and minima on the ESP surface. GaussView 06 software was used to create, visualize, and plot the optimized structure of the cocrystal and HOMO-LUMO orbitals. The AIMALL (10.05.04) software package generated the molecular graph for intra- and intermolecular interactions. The RDG-scatter plot, MEP map, and ELF plot were rendered from Multiwfn 8.0 and VMD 1.9.1 software.

Solvent Vapor/Gas-Induced Guest Transport and Exchange of a Nonporous Organic Crystal to Construct Smart Host-Guest Energetic Materials

Supramolecular materials with advanced properties constructed by intermolecular interactions have attracted extensive attention in many fields, such as sensing, catalysis, and biomedicine. However, in the field of energetic materials, limited by the tight-packed crystal structure of explosives and the strong intermolecular interaction forces, most supramolecular explosives can only be obtained in organic solution or under extreme external loading (high temperature/high pressure). Given the practical issues such as safety risks, operational difficulties, serious environmental pollution, and large-scale production of the existing technology, a new method of constructing host-guest explosives by solvent vapor/gas induction is proposed. This gas-solid reaction method takes advantage of the metastable properties from the explosives solvate (HNIW/ACN), and cleverly opens a fast channel for gas molecules to enter the explosives cell cavities, which results in the highly efficient preparation of the host-guest explosives (HNIW/CO2 and HNIW/N2O). The embedding of functional gas molecules greatly improves the structural stability and comprehensive performance of the explosive skeleton, and the detonation velocity of HNIW/N2O even reaches 9802 m·s-1, which is higher than that of ε-HNIW (9455 m·s-1). In addition, compared with ε-HNIW, HNIW/CO2 and HNIW/N2O exhibit high energy but low sensitivity, enhanced thermal stability, and combustion properties, which present a potential prospect in the field of energetic materials. The new method effectively overcomes the high-energy barrier of nonporous organic explosives, offering the advantages of simplicity, safety, efficiency, and environmental friendliness. This study provides a valuable pathway for constructing advanced supramolecular energetic materials, which contributes to the enrichment of supramolecular engineering systems.

Molecular dynamics simulation of DNAN/DNB cocrystal PBXs

CONTEXT

The DNAN/DNB eutectic is a high-energy explosive eutectic with superior safety and thermal stability compared to traditional melt-cast explosives. However, the addition of polymer binders can effectively enhance its mechanical properties, allowing for continued production demands without the need for changes to existing factory equipment. In this paper, a model of the DNAN/DNB eutectic explosive was established, and five different types of polymers-cis-1,4-polybutadiene (BR), ethylene-vinyl acetate copolymer (EVA), polyethylene glycol (PEG), fluorinated polymer (F2603), and polyvinylidene fluoride (PVDF)-were added to the (1 0 - 1), (1 0 1), and (0 1 1) cleavage planes, respectively, to form polymer-bonded explosives (PBXs). The stability, trigger bond length, mechanical properties, and detonation performance of the various polymer-bound PBXs were predicted retrogressively. Among the five PBX models, the DNAN/DNB/PEG model exhibited the highest binding energy and the shortest trigger bond length, indicating a significant improvement in stability, compatibility, and sensitivity compared to the original eutectic. Additionally, although the detonation performance of DNAN/DNB decreased after the addition of binders, the final results were still satisfactory. Overall, the DNAN/DNB/PEG model demonstrated excellent comprehensive performance, proving that among the many polymer binders, PEG is the optimal choice for DNAN/DNB.

METHODS

Within the Materials Studio software, molecular dynamics (MD) simulations were employed to predict the properties of the DNAN/DNB eutectic PBX. The MD simulation timestep was set to 1 fs, with a cumulative simulation duration of 2 ns. A 2 ns MD simulation was conducted using the isothermal-isobaric ensemble (NPT). The COMPASS force field was applied, and the temperature was fixed at 295 K.

Insight into Formation, Synchronized Release and Stability of Co-Amorphous Curcumin-Piperine by Integrating Experimental-Modeling Techniques

Intermolecular interactions between drug and co-former are crucial in the formation, release and physical stability of co-amorphous system. However, the interactions remain difficult to investigate with only experimental tools. In this study, intermolecular interactions of co-amorphous curcumin-piperine (i.e., CUR-PIP CM) during formation, dissolution and storage were explored by integrating experimental and modeling techniques. The formed CUR-PIP CM exhibited the strong hydrogen bond interaction between the phenolic OH group of CUR and the CO group of PIP as confirmed by FTIR, ss 13C NMR and molecular dynamics (MD) simulation. In comparison to crystalline CUR, crystalline PIP and their physical mixture, CUR-PIP CM performed significantly increased dissolution accompanied by the synchronized release of CUR and PIP, which arose from the greater interaction energy of H2O-CUR molecules and H2O-PIP molecules than CUR-PIP molecules, breaking the hydrogen bond between CUR and PIP molecules, and then causing a pair-wise solvation of CUR-PIP CM at the molecular level. Furthermore, the stronger intermolecular interaction between CUR and PIP was revealed by higher binding energy of CUR-PIP molecules, which contributed to the excellent physical stability of CUR-PIP CM over amorphous CUR or PIP. The study provides a unique insight into the formation, release and stability of co-amorphous system from MD perspective. Meanwhile, this integrated technique can be used as a practical methodology for the future design of co-amorphous formulations.

Molecular dynamics simulation of CL20/DNDAP cocrystal-based PBXs

CONTEXT

CL-20/DNDAP cocrystal is a promising new type of explosive with exceptional energy density and detonation parameters. However, compared to TATB, FOX-7 and other insensitive explosives, it still has higher sensitivity. In order to decrease the sensitivity of CL20/DNDAP cocrystal explosive, in this article, a CL20/DNDAP cocrystal model was established, and six different types of polymers, including butadiene rubber (BR), ethylene-vinyl acetate copolymer (EVA), polyethylene glycol (PEG), hydroxyl-terminated polybutadiene (HTPB), fluoropolymer (F₂₆₀₃), and polyvinylidene difluoride (PVDF), were added to the three cleaved surfaces of (1 0 0), (0 1 0) and (0 0 1) to obtain polymer-bonded explosives (PBXs). Predict the effects of different polymers on the stability, trigger bond length, mechanical properties, and detonation performance of PBXs. Among the six PBX models, CL-20/DNDAP/PEG model exhibited the highest binding energy and the lowest trigger bond length, indicating that CL-20/DNDAP/PEG model had the best stability, compatibility, and the least sensitivity. Furthermore, although the CL-20/DNDAP/F₂₆₀₃ model demonstrated superior detonation capabilities, it should be noted that this model displayed low levels of compatibility. Overall, CL-20/DNDAP/PEG model exhibited the superior comprehensive properties, thereby demonstrating that PEG is a more suitable binder option for PBXs based on the CL20/DNDAP cocrystal.

METHODS

The properties of CL-20/DNDAP cocrystal-based PBXs were predicted by molecular dynamics (MD) method under Materials Studio software. The MD simulation time step was set at 1fs and the total MD simulation time was 2ns. The Isothermal-isobaric (NPT) ensemble was used for the 2ns of MD simulation. The COMPASS force field was used, and the temperature was set at 295K.

Recent Progress on Synthesis, Characterization, and Performance of Energetic Cocrystals: A Review

In the niche area of energetic materials, a balance between energy and safety is extremely important. To address this "energy-safety contradiction", energetic cocrystals have been introduced. The investigation of the synthesis methods, characteristics, and efficacy of energetic cocrystals is of the utmost importance for optimizing their design and development. This review covers (i) various synthesis methods for energetic cocrystals; (ii) discusses their characteristics such as structural properties, detonation performance, sensitivity analysis, thermal properties, and morphology mapping, along with other properties such as oxygen balance, solubility, and fluorescence; and (iii) performance with respect to energy contents (detonation velocity and pressure) and sensitivity. This is followed by concluding remarks together with future perspectives.

Self-gelation involved in the transformation of resveratrol and piperine from a co-amorphous system into a co-crystal system

Self-gelation of co-amorphous system promotes the transformation into its co-crystal system during dissolution.