Nanoscale Topography Influences Polymer Surface Diffusion

Using high-throughput single-molecule tracking, we studied the diffusion of poly(ethylene glycol) chains at the interface between water and a hydrophobic surface patterned with an array of hexagonally arranged nanopillars. Polymer molecules displayed anomalous diffusion; in particular, they exhibited intermittent motion (<i>i.e.</i>, immobilization and “hopping”) suggestive of continuous-time random walk (CTRW) behavior associated with desorption-mediated surface diffusion. The statistics of the molecular trajectories changed systematically on surfaces with pillars of increasing height, exhibiting motion that was increasingly subdiffusive and with longer waiting times between diffusive steps. The trajectories were well-described by kinetic Monte Carlo simulations of CTRW motion in the presence of randomly distributed permeable obstacles, where the permeability (the main undetermined parameter) was conceptually related to the obstacle height. These findings provide new insights into the mechanisms of interfacial transport in the presence of obstacles and on nanotopographically patterned surfaces

Energy and Biocides Storage Compounds: Synthesis and Characterization of Energetic Bridged Bis(triiodoazoles)

Energetic bridged triiodopyrazoles and triiodoimidazoles were designed and synthsized by reacting potassium triiodopyrazolate or triiodoimidazolate with corresponding dichloro compounds. All compounds were fully characterized by ¹H and ¹³C NMR spectroscopy, IR spectroscopy, and elemental analyses. The structure of compound <b>1</b> was further confirmed by single-crystal X-ray diffraction. All of the compounds exhibit good thermal stability with decomposition temperatures between 199 and 270 °C and high densities ranging from 2.804 to 3.358 g/cm³. The detonation performances and the detonation products were calculated by CHEETAH 7. Compound <b>3</b> (<i>D</i>_v = 4765 m s^–1; <i>P</i> = 17.9 GPa) and compound <b>7</b> (<i>D</i>_v = 4841 m s^–1; <i>P</i> = 18.5 GPa) show comparable detonation pressure to TNT, and high iodine content makes them promising as energy and biocides storage compounds

Nitrogen-Rich Energetic Salts: Both Cations and Anions Contain Tetrazole Rings

<div><p>Nitrogen-rich compounds are a kind of new type of energetic material and have good application prospects. They generally have high densities, high positive heats of formation, good thermal stability, and a series of excellent properties. Nitro-rich energetic salts in which cations and anions contain tetrazole rings possess more N-N and C-N bonds. These can help the salts achieve better performance. Their distinct advantages make them attractive for applications in gas generators and high-energy-density materials and as propellant additives.</p></div

Polymer Surface Transport Is a Combination of in-Plane Diffusion and Desorption-Mediated Flights

Previous studies of polymer motion at solid/liquid interfaces described the transport in the context of a continuous time random walk (CTRW) process, in which diffusion switches between desorption-mediated “flights” (i.e., hopping) and surface-adsorbed waiting-time intervals. However, it has been unclear whether the waiting times represented periods of complete immobility or times during which molecules engaged in a different (e.g., slower or confined) mode of interfacial transport. Here we designed high-throughput, single-molecule tracking measurements to address this question. Specifically, we studied polymer dynamics on either chemically homogeneous or nanopatterned surfaces (hexagonal diblock copolymer films) with chemically distinct domains, where polymers were essentially excluded from the low-affinity domains, eliminating the possibility of significant continuous diffusion in the absence of desorption-mediated flights. Indeed, the step-size distributions on homogeneous surfaces exhibited an additional diffusive mode that was missing on the chemically heterogeneous nanopatterned surfaces, confirming the presence of a slow continuous mode due to 2D in-plane diffusion. Kinetic Monte Carlo simulations were performed to test this model and, with the theoretical in-plane diffusion coefficient of <i>D</i>_2D = 0.20 μm²/s, we found a good agreement between simulations and experimental data on both chemically homogeneous and nanopatterned surfaces

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications

Efficient Construction of Energetic Materials via Nonmetallic Catalytic Carbon–Carbon Cleavage/Oxime-Release-Coupling Reactions

The exploitation of C–C activation to facilitate chemical reactions is well-known in organic chemistry. Traditional strategies in homogeneous media rely upon catalyst-activated or metal-mediated C–C bonds leading to the design of new processes for applications in organic chemistry. However, activation of a C–C bond, compared with C–H bond activation, is a more challenging process and an underdeveloped area because thermodynamics does not favor insertion into a C–C bond in solution. Carbon–carbon bond cleavage through loss of an oxime moiety has not been reported. In this paper, a new observation of self-coupling via C–C bond cleavage with concomitant loss of oxime in the absence of metals (either metal-complex mediation or catalysis) results in dihydroxylammonium 5,5-bistetrazole-1,10-diolate (TKX-50) as well as <i>N</i>,<i>N</i>′-([3,3′-bi­(1,2,4-oxadiazole)]-5,5′-diyl)­dinitramine, a potential candidate for a new generation of energetic materials

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications

Efficient Construction of Energetic Materials via Nonmetallic Catalytic Carbon–Carbon Cleavage/Oxime-Release-Coupling Reactions

The exploitation of C–C activation to facilitate chemical reactions is well-known in organic chemistry. Traditional strategies in homogeneous media rely upon catalyst-activated or metal-mediated C–C bonds leading to the design of new processes for applications in organic chemistry. However, activation of a C–C bond, compared with C–H bond activation, is a more challenging process and an underdeveloped area because thermodynamics does not favor insertion into a C–C bond in solution. Carbon–carbon bond cleavage through loss of an oxime moiety has not been reported. In this paper, a new observation of self-coupling via C–C bond cleavage with concomitant loss of oxime in the absence of metals (either metal-complex mediation or catalysis) results in dihydroxylammonium 5,5-bistetrazole-1,10-diolate (TKX-50) as well as <i>N</i>,<i>N</i>′-([3,3′-bi­(1,2,4-oxadiazole)]-5,5′-diyl)­dinitramine, a potential candidate for a new generation of energetic materials