Composite solid propellants face mechanical limitations due to microstructural defects in energetic binders, primarily caused by side-group steric hindrance. To address this, we propose four binder network design strategies: reactive activation, segmental densification, node reinforcement, and topological balancing. Systematically optimizing the formulation (via stoichiometric adjustments, short-chain copolyethers, multifunctional cross-linkers, and gradient curing agents) transforms the binder into a topologically dense network. This structural regulation improves the balance between strength and deformability under the present formulation design, increasing the propellant's tensile strength to 1.04 MPa and elongation at break to 44.4%. For practical structural integrity evaluation, we developed a nonlinear viscoelastic-damage coupled constitutive model based on a Prony series and interfacial debonding geometry. Implemented via a finite element user subroutine, the model reasonably captures the macroscopic mechanical response and modulus softening of the optimized propellant across a wide temperature range (-40 to 70 degrees C). This integrated approach of network regulation and constitutive modeling bridges theoretical material design with computational evaluation for actual engineering applications.

The block copolyether (HTPE) composed of polytetrahydrofuran and polyethylene glycol holds significant promise for preparing insensitive solid propellants. However, no corresponding photosensitive binder formulation has been available for the photopolymerization 3D printing of such propellants. In this study, a photosensitive binder formulation is developed using acrylate-terminated polyether (ATPE), obtained through end-group modification of HTPE, as the oligomer, hydroxyethyl methacrylate (HEMA) and caprolactone acrylate (CA) as reactive diluents, trimethylolpropane triacrylate (TMPTA) as the crosslinker, and N-butyl-N-(2-nitroxyethyl) nitramine (Bu-NENA) as the plasticizer. The effects of ATPE content, crosslinker content, and plasticizer ratio on mechanical properties are systematically investigated using orthogonal experimental. Based on the identified optimal levels, four distinct ATPE-HC# photosensitive binder formulations with varying ATPE contents are ultimately determined. The optimized ATPE-HC# binder films exhibit a low glass transition temperature, favorable processing characteristics, and excellent compatibility with Bu-NENA, ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), and aluminum powder. The results of DLP 3D printing show that ATPE-HC5# has good applicability for rapid photocuring 3D printing of solid propellants. This photosensitive binder strategy, derived from the HTPE molecular structure, not only significantly enhances the production efficiency of solid propellant but also has higher mechanical strength than the thermally cured HTPE solid propellant.

Quantitatively modulating sensitivity of the energetic materials while minimizing detonation energy impact is a persistent challenge as conventional modification methods often sacrifice energy output. Herein, we propose a novel strategy utilizing resonant absorption of vibrational energy levels by specific laser wavelengths to induce thermal effects, leading to controlled lattice disruption with negligible molecular changes.By this method, the irradiation with a 10.6 mu m CO2 laser line on RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) reduces electrostatic sensitivity by 30%, while detonation-related parameters (e.g., velocity, pressure) remain within acceptable error margins.Structural characterization confirmed irradiation-induced crystallographic changes and subtle molecular modifications in RDX. This finding highlights the underlying mechanism of the reduction process. CO2 laser photons are resonantly absorbed by the N-N bonds in RDX molecules, inducing thermal effects in the crystal lattice, leading to crystal melting and partial N-NO2 bond breakage, significantly reducing sensitivity.

The design of high-performance elastomeric networks from highly branched prepolymers represents a significant challenge in polymer science due to inherent topological complexities. Branched glycidyl azide polymer (BGAP), while serving as a functional candidate for energetic binders, typically exhibits restricted mechanical properties arising from steric hindrance, a high proportion of dangling chains, and topological looseness. This study develops a multiscale regulation strategy by optimizing the formulation-defined NCO/OH ratio (R = 5), replacing 20 wt% of BGAP with PET, and adding 1 wt% TMP. The strategy was systematically evaluated across 13 formulations using tensile testing, LF-NMR-derived cross-linked fraction A(c) and crosslink density nu, and XPS/FTIR analysis of urethane-related signals at a plasticizer ratio of 0.3. Optimization achieves a 2.5-fold tensile strength increase to 1.19 MPa with >140% elongation at break, as nu rises from 4.563 & times; 10(-4) to 6.443 & times; 10(-4) mol/mL at A(c)= 66.75%, accompanied by enhanced XPS -NH-/-NO2 and FTIR N-H/C=O urethane-related signals. The observed cross-scale correlations (adjusted R-2 = 0.74-0.97 for the selected parameter pairs) suggest that molecular urethane-related signals are closely associated with effective network evolution and provide a basis for formulation-guided optimization of BGAP-based energetic binders.

The development of thermosetting polyurethane elastomers (TPUEs) face an inherent contradiction between mechanical robustness and re-processability in covalent adaptable networks (CANs), where conventional dynamic bonds either compromise strength (<20 MPa) or require prohibitively high activation temperatures (>150 degrees C). Herein, we address this long-standing challenge through an innovative dynamic crosslinking strategy based on neighboring-group participation (NGP) of thiabicyclo [3.3.1] nonane (S-BCN), constructing ionic CAN (SPU2MC). The double chair-conformation and cation-pi interactions in SPU2MC synergistically enhance mechanical strength (31.1 MPa tensile strength, a 215% increase compared to the glycerol-crosslinked control group (GPU) at the same crosslinking density). Simultaneously, rapid dynamic bond exchange enabled by the NGP allows reprocessing at 110 degrees C (thermal recycling) and 60 degrees C (solvent recycling). Benefiting from the high charge density, SPU2MC also exhibits intrinsic antimicrobial activity (>99.9% inhibition against E. coli and S. aureus) by adhering to bacterial cell walls and disrupting membrane integrity. For the first time, a catalyst-free dynamic crosslinking strategy achieves synergistic optimization of mechanical performance, re-processability, and antibacterial functionality within a single TPUE system. Such materials show great promise for emerging applications in flexible electronics and protective components.

The development of photocuring 3D printed solid propellants is limited by photosensitive binders. Numerous commercial photosensitive oligomers used as binders for solid propellants fail to meet the performance criteria related to processability, mechanical properties, and safety. Modifying established binders that have been used in solid propellants offers a more cost-effective and dependable approach to prepare photosensitive binders. By utilizing the addition reaction between the isocyanate group in 2-isocyanatoethyl acrylate (AOI) and the hydroxyl group in hydroxyl-terminated polyether (HTPE), we successfully modified HTPE to synthesize acrylate-terminated polyether (ATPE), which exhibits the capability of undergoing free radical polymerization. The molecular weight distribution of HTPE and ATPE, as well as the correlated characteristic absorption peaks, were analyzed using gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR) techniques, respectively. The excellent initiation properties of photoinitiator 819, serving as a photosensitive additive of ATPE, were elucidated by comparing the differences in molar absorption coefficients, initiator decomposition rates, and initiator decomposition rate constants among photoinitiators 184, 819, TPO and TPO-L under UV light at 405 nm. The thermal effects resulting from the photopolymerization of ATPE were investigated using photo differential scanning calorimetry (Photo-DSC), and the characteristics of the photopolymerization reaction, along with polymerization kinetic parameters such as the polymerization rate, growth polymerization rate constant (kp), and termination polymerization rate constant (kt), were analyzed in detail. The synthesis and photopolymerization kinetics of ATPE presented in this work provide valuable support for the photopolymerization 3D printing of solid propellants.

Exploring the microscopic mechanism of critical initiation conditions is a challenging task in shock research on energetic materials. Herein, a multiscale impact simulation of hexanitrohexaazaisowurtzitane (epsilon-CL-20) was conducted within a velocity range of 8.0 similar to 10.0 km/s by coupling the NNP-SHOCK force field with the ReaxFF-lg force field. Using peak pressure as a stage division indicator, the impact initiation process was quantitatively divided into two stages: impact compression and intense reaction. Among the large variety of epsilon-CL-20 decomposition products, CO2 content was identified as a key metric to reflect the initial reaction process of epsilon-CL-20, rather than the initial product NO2. The correlation between the change in CO2 quantity and the change in unit cell pressure is particularly high when the shock wave velocity is below the critical shock initiation velocity (9.1 km/s) of CL-20. Correspondingly, the calculated critical decomposition rate of CL-20 reaches 9.451 ps(-1) when subjected to a critical detonation velocity. In addition, reaction network diagrams of epsilon-CL-20 and its typical final products (CO2, H2O, and N-2) were drawn to clarify the initial transformation pathways of epsilon-CL-20 and to determine the intrinsic relationships among the chemical reactions of CO2, H2O, and N-2.

The determination of the composition and timing sequence of products during the detonation of energetic materials is crucial for the evaluation of detonation performance and improvement of the formulation. However, it is difficult to determine the detonation products of energetic materials due to the fast reaction time during detonation. Herein, a new setup is built to detect the detonation products of energetic materials by time correlated laser induced plasma spectroscopy (LIPS) combined with high-speed schlieren imaging. The characteristics of time resolution and spatial distribution of propellant products from laser induced micro-detonation are obtained using the system. According to the time resolved spectrum of the products and high-speed schlieren images of laser induced micro-detonation, we speculate on the timing sequence of gaseous propellant products from laser induced micro-detonation in air: N2, O2, and nitrogen oxides precede hydrocarbon gases, followed by carbon oxides and gaseous containing the element of H. Moreover, the distribution of the gaseous products from laser induced micro-detonation are clarified. This study provides a new method for the detection of products during the detonation of energetic materials. The characteristics of time resolution and spatial distribution of propellant products from laser induced micro-detonation are obtained by time correlated laser induced plasma spectroscopy (LIPS) combined with high-speed schlieren imaging.

The rheological behavior of propellant slurries is crucial for ensuring the feasibility of the 3D printing process, controlling print quality, regulating performance, and simulating predictions. However, there have been relatively few prior studies on the rheological properties of composite solid propellant slurries at low temperatures, which hinders the application of 3D printing propellant technology under extreme temperature conditions. In addition, the use of 3D printing technology to manufacture propellants at low temperatures is advantageous for improving safety. This paper investigates the rheological properties of monodisperse systems with aluminum powder as a solid filler and end-hydroxy polybutadiene (HTPB) as the dispersed phase at low temperatures (-15∼10 °C). It explores the effects of solid content, temperature, and particle size on their rheological properties. Results show that the viscosity of the system in the range of -15∼10 °C increases exponentially with the decrease in temperature, and the viscosity at -15 °C increases by 616.90% compared with that at 10 °C when the volume fraction (φ) of Al-1 is 35.8%; the larger size of the particles the larger the viscosity is when the temperature and φ are the same, which is interpretes in terms of interfacial properties between the systems. The low-temperature correction factor is introduced into the Einstein-Roscoe equation to obtain the modified viscosity-volume fraction equation, and the correction factor is 0.0173, as evidenced by its excellent agreement with the experimental data.

It is highly desirable to actively modulate the explosive performance and sensitivity of traditional explosives, such as RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine), and HMX (cyclotetramethylene tetranitramine), especially to reduce their explosive power and electrostatic sensitivity. Herein, a new avenue is found to effectively modulate the explosive performance and electrostatic sensitivity by direct irradiation of high‐density X‐ray from synchrotron radiation. RDX as a kind of popular and high‐performance explosive, is chosen to demonstrate the modulated effectiveness. After X‐ray irradiation with different irradiation time, the detonation velocity (DV), detonation pressure (DP), heat of detonation (HoD), and electrostatic sensitivity of RDX are determined. Compared with the electrostatic sensitivity and explosive parameters of original high‐quality RDX, the maximum electrostatic sensitivity value is increased to 1061 mJ after irradiation, which is an enhancement ratio of 39.61 %. The lowest DV is 7.57 km/s (−14.27 %), the lowest DP is 16.23 GPa (−53.20 %), and the lowest HoD is 5.15 kJ/g (−9.65 %). These changes mainly originate from the changes in the structure and crystal structure of RDX molecules after irradiation, as evaluated by Scanning Electron Microscope (SEM), X‐ray Diffraction (XRD), and X‐ray Photoelectron Spectroscopy (XPS). The mechanism of RDX modulation by X‐ray is due to denitrification, which always accompanies lots of energy releases, thus impacting the electrostatic sensitivity and explosive power of RDX. Therefore, this study not only provides a new method for reducing electrostatic sensitivity to improve the safety of storage, transportation, and application of RDX, but also holds great potential to reduce explosive performance by non‐contact means.

Liquid crystalline elastomers (LCEs) have emerged as an important class of functional materials that are suitable for a wide range of applications, such as sensors, actuators, and soft robotics. The unique properties of LCEs originate from the combination between liquid crystal and elastomeric network. The control of macroscopic liquid crystalline orientation and network structure is crucial to realizing the useful functionalities of LCEs. A variety of chemistries have been developed to fabricate LCEs, including hydrosilylation, free radical polymerization of acrylate, and polyaddition of epoxy and carboxylic acid. Over the past few years, the use of click chemistry has become a more robust and energy-efficient way to construct LCEs with desired structures. This article provides an overview of emerging LCEs based on click chemistries, including aza-Michael addition between amine and acrylate, radical-mediated thiol-ene and thiol-yne reactions, base-catalyzed thiol-acrylate and thiol-epoxy reactions, copper-catalyzed azide-alkyne cycloaddition, and Diels-Alder cycloaddition. The similarities and differences of these reactions are discussed, with particular attention focused on the strengths and limitations of each reaction for the preparation of LCEs with controlled structures and orientations. The compatibility of these reactions with the traditional and emerging processing techniques, such as surface alignment and additive manufacturing, are surveyed. Finally, the challenges and opportunities of using click chemistry for the design of LCEs with advanced functionalities and applications are discussed.