Cocrystals of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) and 2,4-dinitro-2,4-diazapentane (DNDAP) in a 2 : 1 molar ratio were prepared by both slow evaporation and spray drying methods. The structure of the cocrystals was characterized using single crystal X-ray diffraction and it showed evidence of hydrogen bonds between H_CL-20 and O_DNDAP to the primary stabilizing force in cocrystal formation. Infrared spectroscopy and powder X-ray diffraction analysis indicated that the polycrystalline product from the spray drying method is consistent with the single crystals from solution crystallization. DSC and TG tests revealed that the exothermic decomposition of the cocrystal occurs via two main continuous steps with peak maxima at 223.5 °C and 254.1 °C and largely increases the melting point of DNDAP by 129.9 °C. The cocrystal possesses high detonation velocity and detonation pressure (8997 m s⁻¹ and 37.5 GPa, respectively); meanwhile it features significantly reduced impact and friction sensitivities relative to those of CL-20. These results demonstrate that the CL-20/DNDAP cocrystal can be utilized as a promising ingredient in explosive applications.

To improve the mechanical properties of glycidyl azide polymer (GAP)-based polyurethane network binders, a novel fluorinated glycidyl azide polymer, (2,2,2-trifluoro-ethoxymethyl epoxy-r-glycidyl azide) copolymer (poly(TFEE-r-GA)) was synthesized through an initial cationic copolymerization of epichlorohydrin and 2,2,2-trifluoro-ethoxymethyl epoxy, followed by azidation. The structure of poly(TFEE-r-GA) was characterized by FTIR, ¹H NMR, ¹³C NMR and GPC. DSC and TGA were used to investigate the thermal behavior of poly(TFEE-r-GA), the glass transition temperature and decomposition temperature of poly(TFEE-r-GA) were found to be −49.5 and 250 °C, respectively. The copolyurethane networks were further synthesized by cross-linking poly(TFEE-r-GA) using trimethylolpropane as a chain extender agent, using isophorone diisocyanate as a cross-linking agent. In comparison with GAP, the poly(TFEE-r-GA) based copolyurethane networks exhibited relatively better mechanical properties, which had a tensile strength of 5.52 MPa, and an elongation at break of 162.8%. All the results indicated that the fluorine-containing GAP might serve as a potential energetic binder for future propellant formulations.

Cocrystals of hexanitrohexaazaisowurtzitane (CL-20) and 7H-trifurazano[3,4-b:3′,4′-f:3′′,4′′-d]azepine (TFAZ) in a 1 : 1 molar ratio were prepared by both slow evaporation and self-assembly methods. Structure determination showed that they belong to the monoclinic system (space group P2₁) with a crystal density of 1.932 g cm⁻³. The intermolecular hydrogen bonds and N–O⋯NO₂ type interactions are demonstrated as the predominant driving forces in the cocrystal formation. Furthermore, the cocrystals were successfully synthesized by a self-assembly method using only water as a solvent under mild conditions and the product yield was up to 92.3%. The two types of cocrystals were fully characterized by powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Moreover, the thermal behavior, sensitivity, and calculated detonation performance of the cocrystals were evaluated. The cocrystals exhibit good thermal stability (T_d = 242.8 °C), low impact sensitivity (H₅₀ = 42 cm) and friction sensitivity (P_f = 38%), high crystal density, and high calculated detonation velocity (9103 m s⁻¹). This work opens up a new perspective in the environment-friendly preparation of energetic cocrystals on a large-scale, as well as providing potential low-sensitivity and high-energy explosives.

Molecular dynamics simulations have been employed to study the ε-CL-20-based PBXs under COMPASS force field. ε-CL-20 was chosen as the base explosive due to its higher energy, density and detonation performance than conventional explosives. Four polymers, GAP, GAP-NH₂, GAP-NO₂ and GAP-NH₂-NO₂ were added into the ε-CL-20(001) crystalline surface to build the PBX models. The cohesive energy densities (CEDs), elastic coefficients, isotropic mechanical properties (Young's moduli, bulk moduli, shear moduli, Poisson's ratio, Cauchy pressure and K/G) and initiation bond length distribution were studied. It turned out that the CEDs order was A1 < A4 < A3 < A2 < A. The mechanical properties of pure ε-CL-20(001) were effectively improved by building PBX models. System A3 showed better comprehensive mechanical properties than the other three PBXs. A study on the initiation bond length distribution showed that the L_max and L_ave of N–NO₂ increased with increasing temperature and they were related to the sensitivity of the explosives. The order of L_max was A3 < A4 < A2 < A1 < A, which indicated that the PBXs owned lower sensitivity than system A. These studies are thought to provide guidance for further research on the application of GAP and its derivative polymers. Meanwhile, they are meaningful for the studies on ε-CL-20-based PBXs.

The pursuit of high-energy density materials has been long stymied by the fundamental trade-off between energy output and mechanical sensitivity, a challenge that has persisted for centuries. Herein, we present a dizwitterionic design strategy that enables the synthesis of TYX-2, a planar bistriazolotetrazine-based material exhibiting an unprecedented synergy of high energy and low sensitivity. The molecular model of TYX-2 was elucidated through single-crystal X-ray diffraction analysis of its dimethylamine adduct (TYX-2²⁻·2(Me₂NH₂ ⁺)), which was successfully obtained via crystallization from an aqueous dimethylamine solution. With a measured density of 2.04 g cm⁻³ and detonation velocity of 9.915 km s⁻¹, neutral TYX-2 attains energetic performance comparable to that of the benchmark caged explosive CL-20 while demonstrating radically improved safety characteristics. Its mechanical sensitivity, measured at 180 N (friction) and 22.5 J (impact), represents a 3.7-fold and 5.6-fold reduction relative to CL-20, respectively. When integrated into PNMMO-based solid propellants as a replacement for conventional explosives (such as AP, RDX, HMX and CL-20), neutral TYX-2 significantly enhances specific impulse while mitigating safety risks inherent to current formulations. This work achieves decoupling of energy and sensitivity in energetic materials, offering transformative potential for both military and civilian propulsion technologies.