Laboratoire Hydrazines et Composés Energétiques Polyazotés

The photopolymerization of styrene in emulsion is achieved in a conventional double-wall reactor equipped with a LED ribbon coiled around the external glass wall. Styrene mixed to acridine orange is added to the water phase containing sodium dodecyl sulfate, a water-soluble N-heterocyclic carbene-borane and disulfide, and irradiated. Highly stable latexes are obtained, with particles up to a diameter of 300 nm. The ability to reach such large particle sizes via a photochemical process in a dispersed medium is due to the use of visible light: the photons in the visible range are less scattered by larger objects and thus penetrate and initiate better the polymerizations. They are also greener and cheaper to produce via LEDs, and much safer than UVs. The method presented does not require any specific glassware; it works at lower temperature and delivers larger particles compared to thermal processes at similar solids contents and surfactant concentrations.

Abstract Differential scanning calorimetry of high molar mass poly(4‐vinylphenylboronic acid, pinacol ester)s evidenced unusual reactive events above 120 °C, resulting in a high glass‐transition temperature of 220 °C. A reversible ring‐opening reactivity of pinacol boronates is proposed, involving a nucleophilic attack on the sp 2 boron and subsequent bridging between boron atoms by interconnected pinacol moieties to form a densely crosslinked network with high T g . FTIR, solid‐state NMR investigations, and rheology studies on the polymer as well as double‐tagging analyses on molecular model structures and theoretical calculations further support this hypothesis and indicate a ring‐opening inducing crosslinking. When diluted in an apolar solvent such as toluene, the polymer network can be resolubilized via ring closing, thus recovering the entropically favored linear chains featuring cyclic boronate esters.

Abstract 1,3‐Dimethylimidazol‐2‐ylidene difluoroborane (NHC‐BF 2 H) was prepared in a one‐pot, two‐step reaction from the parent ligated borane (NHC‐BH 3 ). The derived difluoroboryl radical (NHC‐BF 2 . ) was generated by laser flash photolysis experiments and characterized by UV spectroscopy and rate‐constant measurements. It is transient and reacts quickly with O 2 . Unusually, it also reacts more rapidly with ethyl vinyl ether than with methyl acrylate. By this measure, it is the first electrophilic ligated boryl radical. Both NHC‐BH 3 and NHC‐BF 2 H serve as co‐initiators in bulk photopolymerizations, converting both electron‐poor and electron‐rich monomers at roughly similar rates. However, the difluorinated coinitiator provides polymers with dramatically increased chain lengths from both monomers.

The reaction of cyanogen (NC-CN) with MN(3) (M=Na, K) in liquid SO(2) leads to the formation of the 5-cyanotetrazolate anion as the monohemihydrate sodium (1·1.5 H(2)O) and potassium (2) salts, respectively. Both 1·1.5 H(2)O and 2 were used as starting materials for the synthesis of a new family of nitrogen-rich salts containing the 5-cyanotetrazolate anion and nitrogen-rich cations, namely ammonium (3), hydrazinium (4), semicarbazidium (5), guanidinium (6), aminoguanidinium (7), diaminoguanidinium (8), and triaminoguanidinium (9). Compounds 1-9 were synthesised in good yields and characterised by using analytical and spectroscopic methods. In addition, the crystal structures of 1·1.5 H(2)O, 2, 3, 5, 6, and 9·H(2)O were determined by using low-temperature single-crystal X-ray diffraction. An insight into the hydrogen bonding in the solid state is described in terms of graph-set analysis. Differential scanning calorimetry and sensitivity tests were used to assess the thermal stability and sensitivity against impact and friction of the materials, respectively. For the assessment of the energetic character of the nitrogen-rich salts 3-9, quantum chemical methods were used to determine the constant volume energies of combustion, and these values were used to calculate the detonation velocity and pressure of the salts using the EXPLO5 computer code. Additionally, the performances of formulations of the new compounds with ammonium nitrate and ammonium dinitramide were also predicted. Lastly, the ICT code was used to determine the gases and heats of explosion released upon decomposition of the 5-cyanotetrazolate salts.

A Diels–Alder reaction between cyclopentadiene and methyl cyanodithioformate afforded a 60:40 mixture of the isomers 2a and b. The n.m.r. studies of these compounds and the products of LiAlH 4 reduction, 3a and b, established that the major isomer, 2a, was 3-exo-cyano-3-methylthio-2-thiabicyclo-[2.2.1]hept-5-ene, and that 3a was the corresponding 3-exo-aminomethyl compound.

Abstract 1,1,4,4‐Tetramethyl‐2‐tetrazene (TMTZ) is considered as a prospective replacement for toxic hydrazines used in liquid rocket propulsion. The heat of formation of TMTZ was computed and measured, giving values well above those of the hydrazines commonly used in propulsion. This led to a predicted maximum I sp of 337 s for TMTZ/N 2 O 4 mixtures, which is a value comparable to that of monomethylhydrazine. We found that TMTZ has a vapor pressure well below that of liquid hydrazines, and it is far less toxic. Finally, an improved synthesis is proposed, which is compatible with existing industrial production facilities after minor changes. TMTZ is thus an attractive liquid propellant candidate, with a performance comparable to hydrazines but a lower vapor pressure and toxicity.

Investigations of polymerization-induced self-assembly in emulsion were conducted using molecular dynamics simulations. Using umbrella sampling and the weighted histogram analysis method algorithm, we calculated the interaction free energy between different self-assembled copolymer aggregates. In the presence of poly(ethylene glycol) (PEG) side chains at 80 °C, an attractive interaction between the copolymer micelles is observed. This attractive well is followed, in some case, by a repulsive barrier depending on the position of the PEG side chains. The strength of this repulsive barrier controls the aggregation kinetics: a strong repulsive barrier leads to slower aggregation rate and thus larger and denser clusters (i.e., reaction-limited cluster aggregation). These clusters then coalesce into large vesicles due to the presence of interstitial water molecules in the cluster. Inversely, a weak repulsive barrier causes rapid aggregation, which gives loose and ramified clusters (i.e., diffusion-limited cluster aggregation) that coalesce after swelling with a hydrophobic monomer, leading to tubular nanostructures and small vesicles. This new mechanism approach can explain the change of morphology from spheres to fibers and vesicles depending on the polymer architecture in the case of polymerization-induced self-assembly (PISA) in emulsion.

Nanoparticle-based temperature imaging is an emerging field of advanced applications. Herein, the sensitivity of the fluorescence of rhodamine B-doped latex nanoparticles toward temperature is described. Submicrometer size latex particles were prepared by a surfactant-free emulsion polymerization method that allowed a simple and inexpensive way to incorporate rhodamine B into the nanoparticles. Also, rhodamine B-coated latex nanoparticles dispersed in water were prepared in order to address the effect of the dye location in the nanoparticles on their temperature dependence. A better linearity of the temperature dependence emission of the rhodamine B-embedded latex particles, as compared to that of free rhodamine B dyes or rhodamine B-coated latex particles, is observed. Temperature-dependent fluorescence measurements by fluorescent confocal microscopy on individual rhodamine B-embedded latex particles were found similar to those obtained for fluorescent latex nanoparticles in solution, indicating that these nanoparticles could be good candidates to probe thermal processes as nanothermometers.

Bis-NHC adducts of the type (NHC) 2 ·B 2 (OR) 4 are sources of boryl radicals of the type NHC–BR 2 ˙, which are formed by homolytic B–B bond cleavage.

Diaminomaleodinitrile was reacted at low temperatures with in situ generated nitrous acid to form 4,5-dicyano-2H-1,2,3-triazole (1) in yields above 90%. Crystalline 1 was then reacted with one equivalent of a suitable alkali or alkaline earth metal base (typically a hydroxide or a carbonate) in a polar solvent to form the corresponding alkali and alkaline earth metal salts of 4,5-dicyano-2H-1,2,3-triazole (compounds 2-9). The thermal stability of the metal salts 2-9 was assessed by differential scanning calorimetry, which showed excellent thermal stabilities up to above 350 °C. Due to the energetic character of triazole-based salts, initial safety testing was used to assess the sensitivity of compounds 2-9 towards impact, friction, electrostatic discharge and fast heating. These results revealed very low sensitivities towards all four stimuli. Additionally, compounds 2-9 were characterized by mass spectrometry, elemental analysis, infrared and Raman spectroscopy and ((1)H, (13)C and (14)N) NMR spectroscopy. We also determined the solid state structure of the 4,5-dicyano-2H-1,2,3-triazole anion of one of the alkali metal salts (4: Monoclinic, P2(1)/c, a = 9.389(1) Å, b = 10.603(1) Å, c = 6.924(1) Å, β = 102.75(1)° and V = 1036.58(3) Å(3)) and one of the alkaline earth metal salts (6: Monoclinic, P2(1)/c, a = 9.243(1) Å, b = 15.828(2) Å, c = 6.463(1) Å, β = 90.23(1)° and V = 945.5(2) Å(3)). Furthermore, we noted the hydrolysis of one of the cyano groups of the 4,5-dicyano-2H-1,2,3-triazole anion in the strontium salt 8 to form the 5-cyano-2H-1,2,3-triazole-4-carboxylic acid derivative 8b, as confirmed by X-ray studies (8b: Monoclinic, P2(1)/n, a = 6.950(1) Å, b = 17.769(1) Å, c = 13.858(1) Å, β = 92.98(1)° and V = 1709.1(1) Å(3)). Lastly, we computed the NBO and Mülliken charges for the anion of compounds 2-9 and those of the anion of compound 8b.

Abstract Our aim was to study the aromatic nucleophilic substitution between the sodium anion of diethylphosphite and several halogenated substrates like: iodo-anilines, iodo-nitrobenzenes, bromo- and iodopyridines, bromoquinoline. Two coupling processes have been evaluted. The first one is the photostimulated nucleophilic substitution (SRN1), the second the promoted arylation by transition metals. We obtain good results with the first method which is efficient and simple; by contrast the second one has given only few positive results. We describe five aromatic aminophosphonic acids. Nous avons étudié la substitution nucléophile aromatique entre le diéthylphosphite sodé et plusieurs substrats halogénés tels que iodo-anilines, iodonitrobenzenes, bromo- et iodo-pyridines, bromo-quinoleine. Deux méthodes de couplage ont été évaluées. L'une est la substitution nucléophile sous photostimulation (SRN1), l'autre l'assistance par les métaux de transition. La premiere donne de bons résultats dans la majorité des cas étudiés, elle est simple, reproductible, efficace; la seconde plus décevante a donné peu de résultats positifs. Nous décrivons cinq acides aminophosphoniques aromatiques.

1,1,1-Trimethylhydrazinium iodide ([(CH(3))(3)N-NH(2)]I, 1) was reacted with a silver salt to form the corresponding nitrate ([(CH(3))(3)N-NH(2)][NO(3)], 2), perchlorate ([(CH(3))(3)N-NH(2)][ClO(4)], 3), azide ([(CH(3))(3)N-NH(2)][N(3)], 4), 5-amino-1H-tetrazolate ([(CH(3))(3)N-NH(2)][H(2)N-CN(4)], 5), and sulfate ([(CH(3))(3)N-NH(2)](2)[SO(4)]·2H(2)O, 6·2H(2)O) salts. The metathesis reaction of compound 6·2H(2)O with barium salts led to the formation of the corresponding picrate ([(CH(3))(3)N-NH(2)][(NO(2))(3)Ph-O], 7), dinitramide ([(CH(3))(3)N-NH(2)][N(NO(2))(2)], 8), 5-nitrotetrazolate ([(CH(3))(3)N-NH(2)][O(2)N-CN(4)], 9), and nitroformiate ([(CH(3))(3)N-NH(2)][C(NO(2))(3)], 10) salts. Compounds 1-10 were characterized by elemental analysis, mass spectrometry, infrared/Raman spectroscopy, and multinuclear NMR spectroscopy ((1)H, (13)C, and (15)N). Additionally, compounds 1, 6, and 7 were also characterized by low-temperature X-ray diffraction techniques (XRD). Ba(NH(4))(NT)(3) (NT=5-nitrotetrazole anion) was accidentally obtained during the synthesis of the 5-nitrotetrazole salt 9 and was also characterized by low-temperature XRD. Furthermore, the structure of the [(CH(3))(3)N-NH(2)](+) cation was optimized using the B3LYP method and used to calculate its vibrational frequencies, NBO charges, and electronic energy. Differential scanning calorimetry (DSC) was used to assess the thermal stabilities of salts 2-5 and 7-10, and the sensitivities of the materials towards classical stimuli were estimated by submitting the compounds to standard (BAM) tests. Lastly, we computed the performance parameters (detonation pressures/velocities and specific impulses) and the decomposition gases of compounds 2-5 and 7-10 and those of their oxygen-balanced mixtures with an oxidizer.

New energetic polymers were synthesized from monomers containing a trans-2-tetrazene unit. In contrast to traditional binders, such as inert hydroxytelechelic polybutadiene or glycidyl azide polymers-in which the energetic features are on the side chains-the energetic groups in the polytetrazenes are incorporated directly in the polymer backbone. Thermal analyses demonstrated that decomposition occurs at approximately 130 °C, regardless of the polymer structure. Glass-transition temperatures ranged from -34.2 to 0.2 °C and could be lowered further (to -61 °C) with the help of a new diazidotetrazene energetic plasticizer. Interestingly, hexafluoroisopropanol (HFIP) enabled complete, room-temperature depolymerization within 1 week. This depolymerization should enable the recycling of unused pyrotechnic compositions based on these new binders.

1,1-Dimethylhydrazine can be readily alkylated with bromoacetonitrile to form 1-cyanomethyl-1,1-dimethylhydrazinium bromide ([(CH(3))(2)N(CH(2)CN)NH(2)]Br, 1). The metathesis reaction of compound 1 led to the formation of a new family of energetic salts based on the [(CH(3))(2)N(CH(2)CN)NH(2)](+) cation and nitrate (2), perchlorate (3), azide (4), 5-aminotetrazolate ([H(2)N-CN(4)](-), 5), 5,5'-azobistetrazolate ([N(4)C-N=N-CN(4)](2-), 7), and picrate (8) anions. The new materials were characterized by elemental analysis, mass spectrometry, and (multinuclear) NMR and vibrational (infrared and Raman) spectroscopies. Additionally, the molecular structure of the [(CH(3))(2)N(CH(2)CN)NH(2)](+) cation in compounds 1, 3, and 8 and that of sodium 5,5'-azobistetrazolate octahydrate (NaZT·8H(2)O) were solved by X-ray diffraction techniques. The hydrogen-bonding networks found in the structure of salts 1, 3, 8, and NaZT·8H(2)O are described using graph-set analysis. The melting and decomposition points of the new compounds were determined by differential scanning calorimetry, and insight into their sensitivity towards impact, friction, and electrostatics was gained by submitting the materials to standard tests. Furthermore, we estimated some performance parameters of interest and predicted the decomposition gases formed upon decomposition of salts 2-8 and of mixtures with an oxidizer. The interesting thermal, sensitivity, and performance properties of some of the compounds described in this work make them attractive towards a prospective energetic application.

The electronic properties and orientation of films of poly‐3‐alkylselenophenes electrochemically deposited onto Pt have been studied by NEXAFS. The C—K edge characteristics reveal that several major effects occur when n is increased from 0 to 9: (i) In the undoped semiconducting form, a continuous decrease in the polymeric 1s → π* intensity is observed due to an overlap between the π* antibonding band from the polymer and the band which develop when the alkyl chain length increases. (ii) The doping to the conducting state proceeds via a narrowing of the bandgap causing the appearance of metallic‐like behavior. However, the changes in the unoccupied antibonding π* band become less pronounced for a long alkyl chain length. (iii) The orientation of the selenophene ring structure switches from a "lying‐down" to an "on‐edge" configuration with the long alkyl chain being oriented perpendicular to the Pt surfaces.

N-Heterocyclic carbene–boranes (NHC-boranes, NHCBs) were recently described as efficient coinitiators for the visible light photopolymerization of hydroxyethyl methacrylate (HEMA) in the presence of water. In this work, a new, more water-soluble, NHC-borane—2,4-dimethyl-1,2,4,5-tetrazol-3-ylidene borane—has been synthesized, and its efficiency in three-component systems (dye (Acridine Orange), disulfide, and NHC-borane coinitiators) for the polymerization of methacrylate resins under visible light under air has been studied. In fluid resins this new photoinitiating system (PIS) gives better results than the one previously studied. More importantly, this system is competitive with the widely used type II system—camphorquinone/4-(dimethylamino)benzonitrile (DMABN)—for the polymerization of methacrylate resins but better for the photopolymerization of poly(2-hydroxyethyl methacrylate) leading to hydrogels, where the former PIS fails. The excellent ability of the NHC-boranes, and especially the new one, to be used as photopolymerization coinitiators has been analyzed by laser flash photolysis (LFP). The rate constants for elementary reactions of the three boranes and their derived NHC-boryl radicals obtained by LFP correlated well with the molecular modeling data and show that the key for the observed reactivity is the ability of the tetrazolydinyl NHC-borane to repair the peroxyl radicals formed by the reactions of the macroradicals with oxygen.

The reaction of 1,1-dimethylhydrazine with excess dichloromethane led to the formation of the chloride salt of the 1-(chloromethyl)-1,1-dimethylhydrazinium cation ([(CH3)2N(CH2Cl)NH2]Cl, 1). The reaction of 1 with a suitable silver salt provided the nitrate ([(CH3)2N(CH2Cl)NH2][NO3], 2), perchlorate ([(CH3)2N(CH2Cl)NH2][ClO4], 3), azide ([(CH3)2N(CH2Cl)NH2][N3], 4), dicyanamide ([(CH3)2N(CH2Cl)NH2][N(CN)2], 5) and sulphate ([(CH3)2N(CH2Cl)NH2]2[SO4], 6) salts. Compound 6 reacted with barium 5,5′-azobistetrazolate pentahydrate (Ba[N4C–NN–CN4]·5H2O), barium dipicrate tetrahydrate (Ba[(NO2)3Ph–O]2·4H2O) and barium 5-amino-1H-tetrazolate tetrahydrate (Ba[H2N–CN4]2·4H2O) to form the corresponding metathesis products: [(CH3)2N(CH2Cl)NH2]2[N4C–NN–CN4] (7), [(CH3)2N(CH2Cl)NH2][(NO2)3Ph–O] (8) and [(CH3)2N(CH2Cl)NH2][H2N–CN4] (9). Compounds 1–9 were characterized by elemental analysis, mass spectrometry, NMR (1H and 13C) and vibrational spectroscopy (infrared and Raman). Additionally, we measured the 15N NMR spectrum of the nitrate salt 2 and identified the solid state structure of compounds 3, 6, 7 and 8 by low temperature X-ray crystallography (3: Triclinic P, a = 5.983(1) Å, b = 7.502(1) Å, c = 9.335(1) Å; α = 93.86(1)°, β = 101.21(1)°; γ = 91.13(1)°; V = 409.8(1) Å3, 6: Monoclinic C2/c, a = 11.674(2) Å, b = 17.503(3) Å, c = 6.616(1) Å; β = 90.27(1)°; V = 1351.8(4) Å3, 7: Triclinic P, a = 8.851(1) Å, b = 8.872(1) Å, c = 11.529(1) Å; α = 80.98(1)°, β = 83.47(1)°; γ = 71.37(1)°; V = 845.4(1) Å3 and 8: Monoclinic C2/c, a = 24.168(3) Å, b = 7.375(1) Å, c = 17.062(3) Å; β = 116.19(2)°; V = 1351.8(3) Å3). The solid state structure of barium dipicrate hexahydrate (Ba[(NO2)3Ph–O]2·6H2O) was also elucidated: Triclinic P, a = 6.641(1) Å, b = 11.588(1) Å, c = 15.033(1) Å; α = 84.64(1)°, β = 80.07(1)°; γ = 86.80(1)°; V = 1133.8(1) Å3. Furthermore, we studied the thermal properties of compounds 1–9 by differential scanning calorimetry (DSC). Salts 2–4, 8 and 9 fall within the category of ionic liquids. Lastly, the energetic salts were subjected to standard sensitivity tests and a software code was used to predict the detonation parameters and specific impulses of the compounds and their mixtures with an oxidizer.

We have developed the first family of air- and moisture-stable pentafluorosulfanylation (SF₅) reagents. Although the SF₅ group is a bioisostere of the trifluoromethyl group (CF₃)-exhibiting even greater electronegativity and lipophilicity, attributes that have earned it the nickname "super trifluoromethyl group"-the development of shelf-stable, non-toxic, and easy-to-handle SF₅-incorporating reagents had remained elusive for over 70 years since its discovery. Our discovery enables the synthesis of per- and polyfluoroalkyl substances (PFAS)-free fluorinated compounds, offering significant advantages over traditional CF₃ analogs. These new reagents exhibit promising reactivity under photochemical conditions, efficiently facilitating the formation of novel SF₅-containing molecules. Moreover, our approach is compatible with the late-stage functionalization of complex molecules. Mechanistic studies have provided valuable insights into the underlying reaction pathways.

In the development of 3D printing fuels, there is a need for new photoinitiating systems working under mild conditions and/or leading to polymers with new and/or enhanced properties. In this context, we introduce herein N-heterocyclic carbene-borane complexes as reagents for a new type of photo-click reaction, the borane-(meth)acrylate click reaction. Remarkably, the higher bond number of boranes relative to thiols induced an increase of the network density associated with faster polymerization kinetics. Solid-state NMR evidenced the strong participation of the boron centers on the network properties, while DMA and AFM showed that the materials exhibit improved mechanical properties, as well as reduced solvent swelling.

Abstract The photopolymerization of styrene in emulsion is achieved in a conventional double‐wall reactor equipped with a LED ribbon coiled around the external glass wall. Styrene mixed to acridine orange is added to the water phase containing sodium dodecyl sulfate, a water‐soluble N‐heterocyclic carbene–borane and disulfide, and irradiated. Highly stable latexes are obtained, with particles up to a diameter of 300 nm. The ability to reach such large particle sizes via a photochemical process in a dispersed medium is due to the use of visible light: the photons in the visible range are less scattered by larger objects and thus penetrate and initiate better the polymerizations. They are also greener and cheaper to produce via LEDs, and much safer than UVs. The method presented does not require any specific glassware; it works at lower temperature and delivers larger particles compared to thermal processes at similar solids contents and surfactant concentrations.