Porous arylamine polymer stabilizer suitable for nitrocotton

Abstract

The invention relates to a porous arylamine polymer stabilizer (POP-EDA) suitable for nitrocotton, which is prepared from a node unit 1, 3, 5-tribromobenzene and a connecting unit ethylenediamine. As chain fatty amine, ethylenediamine not only can introduce NOX absorption active sites, but also can construct a non-conjugated spatial network arylamine polymer structure. Compared with a conventional stabilizing agent, the polymer has high thermal stability and a relatively high specific surface area, not only has efficient physical adsorption capacity on nitrogen oxides generated by decomposition of nitrocotton, but also can stably and chemically fix the nitrogen oxides, so that autocatalytic decomposition of the nitrocotton is inhibited, and the service life of the nitrocotton can be effectively prolonged. The problems of poor thermal stability, few reaction active sites, generation of by-product gas, poor stabilizing effect and the like of the existing small-molecule stabilizing agent are solved, and the stability of the nitrate-based energetic material can be widely enhanced.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and more specifically, to a porous aromatic amine polymer suitable for use as a stabilizer for nitrocellulose. Background Technology

[0002] Because of the relatively low bond energy of nitrate ester groups, energetic materials such as nitrate cellulose (NC) will undergo slow exothermic decomposition even under normal storage conditions (temperature and humidity). Furthermore, the decomposition of nitrate cellulose is accelerated and catalyzed by nitrogen oxides produced during the decomposition process, which seriously affects the mechanical, chemical and ballistic properties of energetic materials and may even lead to thermal runaway explosions, thereby endangering the safety of weapon systems.

[0003] Currently, the most widely used traditional stabilizers are small molecule aromatic weak bases, such as diphenylamine (DPA), 2-nitrodiphenylamine (2-NDPA), stabilizer No. 2 (C2), stabilizer No. 1 (C1), and N-methyl-N',N'-diphenylurea (AK-II). However, the above-mentioned small molecule stabilizers have the following problems: the dense structure causes nitrogen oxides to react with them layer by layer from the outside to the inside, which limits the reaction rate; the nitrosamine derivatives produced during the stabilization process of DPA are carcinogenic substances, and their melting point is only 52℃, which has poor thermal stability and is easy to migrate during processing and molding, thus affecting the overall stabilization effect; C1 and C2 phenylurea stabilizers not only release CO2 during the stabilization process, which seriously affects the structural strength of the gunpowder, but also have problems such as poor thermal stability, few active sites, and poor stabilization effect (Reference 1: Curtis, NJ; Berry, P., Derivatives of Ethyl Centralite in Australian propellants. Propellants, Explosives, Pyrotechnics 2004, 14(6), 260-265.), (Reference 2: Trache, D.; Khimeche, K., Study on the influence of aging on chemical and mechanical properties of N,N′-dimethyl-N,N′-diphenylcarbamide) stabilizedpropellants.Journal of Thermal Analysis and Calorimetry 2012,111(1),305-312.).

[0004] With the continuous development of stabilizers, some functionalized polymers and macromolecules have been developed as stabilizers. Reference 3 (Shehata, AB; Hassan, MA, Poly N-(4-chlorophenyl), polyN-(4-methylphenyl)acrylamides and the copolymer of their monomers as stabilizers for nitrocellulose. Polymer Degradation and Stability 2002, 81(77), 355–370.) designed a class of polyamide derivatives 4-CPA and 4-MPA, with melting points of 183℃ and 167℃, respectively. They do not produce other gases during the reaction, but as polymers, they have fewer reaction sites and also suffer from layer-by-layer reaction and low reaction rate. References 4 (Zayed, MA; El-Begawy, SEM, Mechanism study of stabilization of double-base propellants by using zeolite stabilizers (nano-and micro-clinoptilolite). Arabian Journal of Chemistry 2017, 10(4), 573-581.) and 5 (Zayed, MA; El-Begawy, SE, Enhancement of stabilizing properties of double-base propellants using nano-scale inorganic compounds. J Hazard Mater 2012, 227-228, 274-9.6) studied the stability of double-base propellants (DBP) containing clinoptilolite stabilizers using physical adsorption. The propellants showed good stabilization effects, but nitrogen oxides were easily desorbed at high temperatures due to physical adsorption alone. Reference 6 (Cherif, MF; Trache, D., Organosolv lignins as new stabilizers for cellulose nitrate: Thermal behavior and stability assessment. 2020, 164, 794-807.) mentions lignin, an organic solvent extracted from natural plants, as a stabilizer. However, its reactivity with nitrogen oxides is weak, and it has few reactive sites per unit mass. Therefore, there is an urgent need to develop a stabilizer with high thermal stability, low toxicity, high chemical reactivity, and that does not produce other gases. Summary of the Invention

[0005] POP-EDA has a unique porous structure, a high specific surface area, and high reactivity towards nitrogen oxides. Therefore, the purpose of this application is to provide a porous aromatic amine polymer stabilizer suitable for nitrocellulose.

[0006] In the first aspect, the present invention provides a porous aromatic amine polymer stabilizer suitable for nitrocellulose, which has the following structure:

[0007]

[0008] n is a repeating unit, 2 < n < 10, and n is an integer.

[0009] In the second aspect, the present invention provides a method for preparing the porous aromatic amine polymer described in the first aspect. The porous aromatic amine polymer (POP-EDA) is synthesized through the Buchwald-Hartwig reaction, and specifically includes the following steps:

[0010] Under nitrogen protection, 1,3,5-tribromobenzene, ethylenediamine, a palladium catalyst, a ligand, and a base are placed in an anhydrous solvent, the heating temperature is 50 - 110 °C, and the mixture is refluxed for more than 48 h. After the reaction ends, it is washed, Soxhlet extracted, and vacuum dried to obtain the porous aromatic amine polymer.

[0011] Further, the palladium catalyst is palladium acetate, bis(dibenzylideneacetone)palladium, or tris(dibenzylideneacetone)dipalladium.

[0012] Further, the ligand is 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (XPhos), 2-dicyclohexylphosphino-2',6'-diisopropoxy-1,1'-biphenyl (RuPhos), or 2-(dicyclohexylphosphino)-3,6-dimethoxy-2'-4'-6'-tri-i-propyl-1,1'-biphenyl (BrettPhos).

[0013] Further, the base is sodium tert-butoxide, potassium carbonate, or cesium carbonate.

[0014] Further, the anhydrous solvent is tetrahydrofuran, toluene, N,N'-dimethylformamide, 1,4-dioxane, or dimethyl sulfoxide.

[0015] Further, the molar ratio of 1,3,5-tribromobenzene to ethylenediamine is 1:1.5 - 1:2; the molar ratio of 1,3,5-tribromobenzene to palladium acetate is 1:0.01 - 1:0.8; the molar ratio of 1,3,5-tribromobenzene to XPhos is 1:0.01 - 1:0.08; the molar ratio of 1,3,5-tribromobenzene to sodium tert-butoxide is 1:1.2 - 1:3;

[0016] Furthermore, Soxhlet extraction was performed using methanol and chloroform for two days.

[0017] Furthermore, it was dried in a vacuum oven at 70°C for 12 hours.

[0018] Thirdly, the present invention provides the use of the porous aromatic amine polymer described in the first aspect as a stabilizer for nitrocellulose.

[0019] Furthermore, the porous aromatic amine polymer is doped with nitrocellulose, with a mass ratio of nitrocellulose to porous aromatic amine polymer of 1% to 5%.

[0020] By mixing it with nitrocellulose, nitrogen oxides can be absorbed through both physical and chemical means to inhibit the autocatalytic decomposition of nitrocellulose, thereby extending the storage time of nitrocellulose, increasing its storage temperature range, and providing better stability.

[0021] The technical solutions provided in this application have at least the following advantages compared with the prior art:

[0022] This application provides a porous aromatic amine polymer suitable as a stabilizer for nitrocellulose. The porous aromatic amine polymer exhibits high thermal stability; according to TGA analysis, its decomposition temperature can reach 250°C, exceeding that of most traditional stabilizers. Furthermore, the porous aromatic amine polymer also possesses a high specific surface area; nitrogen isothermal adsorption experiments show that its specific surface area is approximately 25 m². 2 / g, compared to smaller molecules and traditional dense polymers, provides more reaction sites for them with nitrogen oxides; porous aromatic amine polymers have good compatibility with nitrocellulose (compatibility level I), exceeding that of diphenylamine; thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and solid-state analysis were performed. 13 Characterization techniques such as 12C nuclear magnetic resonance (NMR) verified that the reaction between the porous aromatic amine polymer and nitrogen oxides produced stable nitro compounds, demonstrating its high chemical reactivity with nitrogen oxides. The polymer is insoluble in common solvents and is environmentally friendly. This invention significantly improves the thermal stability of nitrocellulose, and methyl violet testing shows that the porous aromatic amine polymer, as a stabilizer, can extend the color change time of nitrocellulose by 55.8%. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below:

[0025] Figure 1This application provides a preparation process and stabilization mechanism for porous aromatic amine polymers suitable as stabilizers for nitrocellulose.

[0026] Figure 2 This is a TGA image of the porous aromatic amine polymer in Example 1 of this application.

[0027] Figure 3 FT-IR (a) and FT-IR (b) of the porous aromatic amine polymer in Example 1 of this application 13 C NMR (b).

[0028] Figure 4 SEM (a) and TEM (b) images of the porous aromatic amine polymer in Example 1 of this application.

[0029] Figure 5 The BET (a) and pore size distribution spectra (b) of the porous aromatic amine polymer in Example 1 of this application are shown.

[0030] Figure 6 The thermal properties of porous aromatic amine polymers and diphenylamine as stabilizers in Example 1 of this application are compared, wherein (a) TGA, (b) and (c) MMC, (d) and (e) VST, and (f) methyl violet.

[0031] Figure 7 For the compatibility test of porous aromatic amine polymer and diphenylamine with NC in Example 1 of this application, NC: stabilizer = 1:1, wherein (a) NC, (b) DPA, (c) POP-EDA DSC spectra at 2, 5, 8, 10 K / min, 150-250 °C, and nitrogen atmosphere; (d) NC, DPA and POP-EDA activation energy spectra under Friedman method.

[0032] Figure 8 The FT-IR (a) and FT-IR (a) of the porous aromatic amine polymer in Example 1 of this application after absorbing nitrogen oxides. 13 CNMR(b).

[0033] Figure 9 The images show the C1s (a), N1s (b), C1s (c), and N1s (d) spectra of the porous aromatic amine polymer POP-EDA (Example 1 of this application).

[0034] Figure 10 Vacuum stability test of POP-EDA and POP-EDA-Pd(dba)2 with NC in Example 2 of this application. Detailed Implementation

[0035] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0036] The concept of this invention is: combining Figure 1 A porous aromatic amine polymer, POP-EDA, was prepared using 1,3,5-tribromobenzene and ethylenediamine as raw materials via the Buchwald-Hartwig reaction. POP-EDA can stabilize nitrocellulose by immobilizing nitrogen oxides generated from the thermal decomposition of nitrocellulose through a dual-mode process of physical adsorption and chemical fixation.

[0037] In the examples below, the porous aromatic amine polymers were prepared by the Buchwald-Hartwig reaction, therefore all raw materials used must be anhydrous.

[0038] Example 1:

[0039] I. Preparation of POP-EDA

[0040] (1) 1,3,5-Tribromobenzene (3 mmol), ethylenediamine (4.5 mmol), palladium acetate (0.18 mmol), XPhos (0.18 mmol), and sodium tert-butoxide (3.6 mmol) were added to a Schrank flask, evacuated three times under vacuum, and then purged with nitrogen. Anhydrous tetrahydrofuran (5 mL) was then added, and the mixture was heated to 65 °C and reacted for two days.

[0041] (2) After the reaction is complete, the resulting mixture is washed with deionized water and dichloromethane until neutral. Then, Soxhlet extraction is performed for two days using methanol and chloroform.

[0042] (3) Finally, the product was dried in a vacuum oven at 70°C for 12 hours to obtain a gray-black polymer, called a porous aromatic amine polymer, named POP-EDA, with a yield of 21.3%.

[0043] II. Thermal stability test of POP-EDA

[0044] The thermal properties of the samples were tested using a thermogravimetric analyzer under a nitrogen atmosphere at temperatures ranging from 50 to 800°C. Figure 2 As shown.

[0045] TGA results indicate that the polymer exhibits excellent thermal stability with a thermal decomposition temperature up to 250 °C. The weight loss observed at lower temperatures is attributed to solvent and water absorption, which is common in porous materials. Weight loss above 250 °C corresponds to polymer decomposition.

[0046] III. Microstructure Analysis of POP-EDA

[0047] Fourier transform infrared (FT-IR) spectra of POP-EDA and raw materials were acquired using a Nicolet iS20 Fourier transform infrared spectrometer (Thermo Scientific). This instrument is equipped with a DTGS KBr detector and a KBr beam splitter at 0.4 cm⁻¹. -1 The sample was scanned 32 times at a resolution of [resolution missing]. The pore structure of the samples was determined using a Micromeritics ASAP 2460 surface area and porosity analyzer at 77 K via a nitrogen adsorption-desorption isotherm. Prior to measurement, the polymer was degassed at 90 °C, while POP-EDA underwent vacuum degassing at 120 °C for 8 hours. The Brunauer-Emmet-Teller (BET) model was used to calculate the surface area and total pore volume (V) in the range of P / P0 = 0.05–0.30. total The pore size distribution (PSD) was determined using the Barret-Joyner-Halenda (BJH) method, calculated from the isotherm with P / P0 = 0.99.

[0048] The chemical structure of POP-EDA was analyzed by FT-IR, and the results are as follows: Figure 3 As shown in (a), the spectra of 1,3,5-tribromobenzene, ethylenediamine, and POP-EDA are presented. After polymerization, the primary amine absorption peaks at 3354 and 3278 cm⁻¹ disappear, replaced by a secondary amine (NH) absorption peak at 3240 cm⁻¹, and methylene (-CH₂-) stretching vibration peaks at 2936 and 2869 cm⁻¹. The in-plane bending vibration of the methylene CH at 1447 cm⁻¹ confirms the formation of the methylene linkage. Furthermore, an aromatic CN stretching vibration is observed at 1280 cm⁻¹, indicating linkage with the benzene ring. The stretching vibrations at 3073 cm⁻¹ and 1545 cm⁻¹ are related to the unsaturated CH bonds of the aromatic ring and the benzene ring skeleton, respectively. The vibrations at 1658 cm⁻¹ and 1580 cm⁻¹ are attributed to the in-plane bending vibrations of the NH in the secondary and primary amines, respectively. The CN stretching vibration of the secondary amine is observed at 1055 cm⁻¹. These observations confirm the formation of the aromatic amine polymer structure. To further confirm the structure of POP-EDA, 13 CCP / MAS NMR spectroscopy analysis. The experimental spectra showed typical signals for aromatic and aliphatic carbons. In solid state... 13 CMAS NMR spectroscopy ( Figure 3In (b), the carbon signal of the aromatic ring appears in the range of 110-150 ppm. The resonance peaks at 47.1 ppm and 26.3 ppm are attributed to the secondary carbon of the methylene group, respectively. The resonance peak at 47.1 ppm is attributed to the methylene carbon attached to the secondary amine. The signal at 26.3 ppm is attributed to the carbon attached to the unreacted primary amine, which is a common phenomenon at polymer boundaries. These results indicate the successful synthesis of aromatic amine polymers.

[0049] Subsequently, we used FE-SEM ( Figure 4 a, b) and HAADF-STEM Figure 4 Images c) and d) show the morphology and microstructure of POP-EDA. The images reveal a rough surface with pores of various sizes. This porous structure significantly enhances the specific surface area of ​​POP-EDA, increasing its active sites for interaction with nitrogen oxides. Furthermore, due to its hypercrosslinked structure, POP-EDA is insoluble in common organic solvents such as dimethyl sulfoxide (DMSO), N,N'-dimethylformamide (DMF), chloroform, and tetrahydrofuran (THF), indicating its high chemical stability.

[0050] To further explore the effects of POP-EDA on NO X To investigate the physical adsorption and chemical absorption mechanisms, we conducted a series of tests on POP-EDA exposed to gas after heating to NC, and named the resulting absorbed substance POP-EDA-NO2. The permanent porosity of POP-EDA and POP-EDA-NO2 was characterized by nitrogen adsorption-desorption isotherms at 77 K. Figure 5 (a) The isotherms of POP-EDA show a slight increase in adsorption at very low relative pressures (P / P0 < 0.01). Furthermore, nitrogen adsorption increases continuously in the P / P0 range of 0.1 to 0.8, exhibiting a Type IV isotherm with H2 hysteresis consistent with IUPAC classification. When the P / P0 value is greater than 0.8, the loose packing of small particles leads to a significant increase in interparticle porosity, indicating that POP-EDA is primarily composed of a mesoporous structure. The almost reversible adsorption-desorption isotherms of POP-EDA indicate that the polymer network constructed from aromatic rings and aliphatic primary amines possesses sufficient rigidity. The N2 adsorption and desorption isotherms of POP-EDA-NO2 are almost identical to those of POP-EDA, with BET specific surface areas of 25.1 m². 2 / g and 20.9m 2 / g. Based on nonlocal density functional theory (NL-DFT) and the BJH method, POP-EDA and POP-EDA-NO2 exhibit a relatively wide pore size distribution ( Figure 5 (b) The total pore volume (V) of POP-EDA and POP-EDA-NO2. TotalThe values ​​are 0.15cm respectively. 3 / g and 0.13cm 3 The average pore sizes were 24.0 nm and 23.6 nm, respectively, indicating that they were mainly composed of mesopores. Compared with other amorphous POP materials, POP-EDA exhibited a lower apparent surface area. XRD patterns confirmed that the wide pore size distribution of POP-EDA was attributed to the spatial degree of freedom of the aliphatic chains, which led to distortion during polymerization, forming an amorphous polymer structure. The wide pore size range contributes to NO X Free access to the internal network increases its chances of interacting with the active sites within POP-EDA. Compared to POP-EDA, the pore size distribution of POP-EDA-NO2 is significantly narrower. This indicates that the porous structure of POP-EDA does indeed enable NO to freely enter the internal network. X It enters its interior through macropores and reacts with the active sites. X The filling of NO leads to a decrease in the specific surface area, total pore volume, and average pore size of POP-EDA-NO2. Notably, the pore volume of POP-EDA-NO2 increases significantly in the 2-3 nm range, which may be due to the filling of some of the slightly larger pores with NO. X The pores become smaller. This also explains why porous structures absorb NO. X Its role in.

[0051] IV. Thermal and NC Stability Analysis of POP-EDA

[0052] The physical mixture used to evaluate the stability of the samples to nitrocellulose (NC) was NC / POP-EDA (3% wt). Thermogravimetric analysis (TGA) was performed using a TGA / SDTA851E thermal analyzer (METTLER TOLEDO). The surface chemical state of the samples was analyzed by X-ray photoelectron spectroscopy (XPS) using a monochromatic Al Kα X-ray source on a Bruker Avance Neo400WB instrument (Bruker Daltonics). The morphology of the samples was characterized by field emission scanning electron microscopy (Gemini SEM 300, Carl Zeiss AG, operating voltage 10 kV). High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images and energy-dispersive X-ray spectroscopy (EDS) plots were obtained using a JEM-F200 (JEOL, Japan). The thermal decomposition of nitrocellulose was evaluated using an MMC274 multi-module calorimeter (NETZSCH Prowen Excellence). Non-isothermal DSC experiments were performed on a NETZSCH DSC204F1 instrument. The physical mixture for stability was NC / POP-EDA (50 wt%), the purge gas flow rate was 40 mL / min, the protective gas flow rate was 60 mL / min, the temperature range was 50 °C to 300 °C, and the heating rates were 2 °C / min, 5 °C / min, 8 °C / min, and 10 °C / min, respectively. Vacuum stability (VST) tests of the sample against nitrocellulose were performed using a VST 200Pro DAF4.0 (IDEA SCIENCE), with the test temperature maintained at 100 °C, the sample mass being 500 mg, and the duration being 48 hours. After 48 hours, the volume of gas released per unit mass of the sample was measured. The sample was heated in a test tube at 134.5 °C with a sample mass of 2.5 g, and methyl violet paper was used. The time (in minutes) required for the paper color to change from purple to salmon color was then measured. The wavenumber range of the infrared spectrometer was 4000 cm⁻¹. -1 ~550cm -1 .

[0053] To evaluate the stability of POP-EDA as a stabilizer for nitrate-based energetic materials, a series of stability tests were conducted. Test samples were prepared by physically mixing NC with the stabilizer, ensuring the stabilizer content was 3 wt%. All thermal analysis and stability performance test samples contained 3 wt% stabilizer, except for those tested by differential scanning calorimetry (DSC), which contained 50% stabilizer. The test samples were labeled POP-EDA / NC and DPA / NC, respectively.

[0054] Figure 6Figure (a) shows the TGA curves of NC, DPA / NC, and POP-EDA / NC at 134.5 °C. The figure clearly shows that NC experienced significant thermal weight loss, while the thermal weight loss of POP-EDA / NC was significantly reduced. The weight losses of NC, DPA / NC, and POP-EDA / NC were 94.9%, 97.6%, and 98.0%, respectively. It can be observed that POP-EDA exhibits significantly stronger stability during the isothermal process, especially in the first 10 minutes, compared to DPA. DPA does not appear to show a stabilizing effect in the first three minutes of the reaction, which may be because the reaction of DPA with NOX depends on the NOX concentration. The TGA results indicate that POP-EDA provides superior stability compared to the conventional stabilizer DPA. Figure 6 Figures (b) and (c) show the MMC curves of NC, DPA / NC, and POP-EDA / NC at 134.5 °C, with the heating and isothermal sections distinguished. The figures show that after one day of gas release, the pressures of NC, DPA / NC, and POP-EDA / NC were 5.1, 2.4, and 1.7 bar, respectively. The introduction of the stabilizer significantly reduced the gas release of NC. Throughout the process, the pressure rise rate of NC stabilized by POP-EDA remained almost constant, demonstrating good chemical reactivity. Compared to DPA, POP-EDA exhibited lower gas release, indicating superior performance in inhibiting nitrocellulose decomposition compared to the traditional stabilizer DPA.

[0055] In the VST experiment, such as Figure 6 Compared to DPA, POP-EDA exhibits lower gas release in (d) and (e) of the results, indicating its superior performance in inhibiting cellulose nitrate decomposition compared to the traditional stabilizer DPA. However, the stability of DPA shown in the pressure-time curves is inconsistent with the gas evolution results. This inconsistency stems from DPA's lower melting point, leading to the generation of a certain amount of saturated vapor; while the gas evolution calculations are based on the pressure of the cooling gas. The results show that POP-EDA significantly reduces NC gas release, with DPA and POP-EDA reducing the gas release rate by 80.6% and 68.2%, respectively. Combined with the Pt curves, it is clear that the stability of POP-EDA for NC is similar to that of DPA. Thermal analysis further confirms its significant stabilizing effect on NC.

[0056] To more intuitively describe the stabilizing ability of POP-EDA on nitrocellulose (NC), we conducted methyl violet tests on NC, DPA / NC, and POP-EDA / NC at 134.5℃. Figure 6As shown in (f) of the figure, it is clear from the figure that NC, DPA / NC, and POP-EDA / NC caused the methyl violet test paper to turn yellow at 23.3 minutes, 36.1 minutes, and 36.3 minutes, respectively. The experimental results show that DPA and POP-EDA both exhibit similar stabilizing abilities.

[0057] V. Compatibility testing of POP-EDA and NCZ and calculation of NC activation energy with different stabilizers

[0058] The activation energy (Ea) was obtained using the Friedman method and NETZSCH Kinetics Neo software. Figure 7 The curve of a) and conversion rate (in the figure) Figure 7 (b) The results show that the activation energy of nitrocellulose (NC) is 190.0 kJ / mol, R 2 It is 0.99953. For DPA / NC, the activation energy is 265.0 kJ / mol, R 2 It is 0.99743, ΔE a1 It is 75.0 kJ / mol, ΔE a1 / E a It is 39.5%. For POP-EDA / NC, the activation energy is 208.1 kJ / mol, R 2 It is 0.99743, ΔE a2 It is 18.1 kJ / mol, ΔE a2 / E a The percentage was 9.5%. DPA and POP-EDA increased the average activation energy of NC thermal decomposition by 39.5% and 9.5%, respectively. According to compatibility assessment criteria, ΔT p01 =0.1℃≤2.0℃, and ΔE a1 / E a =39.5% > 20%; ΔT p02 = -0.8℃≤2.0℃, and ΔE a2 / E a =9.5% < 20%. Therefore, DPA and NC exhibit Level II compatibility, while POP-EDA and NC exhibit Level I compatibility.

[0059] VI. Structural Analysis of POP-EDA After Absorption of Nitrogen Oxides

[0060] First, we performed FT-IR spectroscopy on POP-EDA-NO2 and 13 C solid-state NMR spectroscopy analysis. Figure 8 'a' in the figure demonstrates the effect of POP-EDA in absorbing NO XInfrared spectra at 0, 1, 2, and 3 hours. The FT-IR spectrum of POP-EDA changed significantly after NO2 absorption. Notably, the change occurred at 1636 cm⁻¹. -1 A characteristic absorption peak for the C=O bond appeared at 1447 cm⁻¹. -1 The CH bending vibration peak disappears at 1409 cm⁻¹. -1 A peak corresponding to the CN stretching vibration of primary amide appeared at 1278 cm⁻¹, indicating that the hydrogen on the methylene group was gradually replaced by oxygen. Furthermore, at 1278 cm⁻¹... -1 The peak at 1054 cm⁻¹ is attributed to the stretching vibration of CN and the in-plane bending vibration of NH, indicating the formation of an amide structure in the sample. -1 The gradual decrease in the CN stretching vibration peak of the secondary amine further confirms the formation of the amide structure. (1336 cm⁻¹) -1 The characteristic peak of the NO2 symmetric stretching vibration indicates that POP-EDA successfully absorbed NO2. From the relative intensities of the peaks and their changes over time, it can be inferred that POP-EDA first forms an amide, followed by further reaction to generate a nitro compound. Although this sequence is not absolute, it effectively reflects the priority and rate of the reaction.

[0061] From POP-EDA in absorbing NO X 0 hours and 3 hours later 13 C solid-state NMR spectroscopy ( Figure 8 As shown in b), POP-EDA mainly exhibits three characteristic peaks: aliphatic carbon peaks at 29.2 ppm and 49.9 ppm, and aryl benzene ring carbon peaks at 123.0 ppm and 131.4 ppm. The peak at 29.2 ppm corresponds to the methylene carbon linked to the primary amine, while the peak at 47.1 ppm corresponds to the methylene carbon linked to the secondary amine. The peak at 131.4 ppm is attributed to the benzene ring carbon linked to the secondary amine, and the peak at 123.0 ppm represents the unsubstituted benzene ring carbon. (Regarding NO absorption...) X Three hours later, new peaks appeared in POP-EDA-NO2 at 140.6 ppm and 168.0 ppm, corresponding to C-NO2 and O=CN, respectively. This indicates the formation of nitro and amide structures. Observing the changes in the benzene ring carbon in the 120-150 ppm range, it can be seen that the benzene ring carbon attached to the secondary amine remains unchanged, while the signal at 123.0 ppm is significantly weakened, indicating that the hydrogen on the unsubstituted benzene ring carbon is replaced by a nitro group. Due to the strong electron-withdrawing property of the nitro group, the peak at 140.6 ppm is considered to be the benzene ring carbon attached to the nitro group. The signals of the two aliphatic carbons also weakened significantly, which is attributed to the partial conversion of aliphatic carbons into amide carbons.

[0062] XPS was used to study the effect of POP-EDA on NO. XThe absorption mechanism. The binding energy of CC / CH at 284.8 eV was used as a reference. In the C1s spectrum of POP-EDA ( Figure 9 In the N1s spectrum, the peaks at 284.8 eV and 286.0 eV correspond to carbon atoms in the benzene ring and secondary amine, respectively. Figure 9 In b), the strong peak at 399.1 eV corresponds to an amino group. (Absorption of NO) X Subsequently, the XPS spectrum of POP-EDA-NO2 ( Figure 9 c) shows new peaks at 287.5 eV and 288.6 eV in the C1s spectrum, representing C=O and C-NO2 respectively. This indicates the formation of carbonyl and nitro groups during NOx absorption, consistent with infrared spectroscopy and... 13 The results were consistent with those of CMAS NMR spectroscopy. In the N1s spectrum of POP-EDA-NO2 ( Figure 9 In d), the peaks at 399.1 eV, 400.2 eV, and 401.7 eV represent CN, NC=O, and -N=O, respectively. Furthermore, the peaks at 405.9 eV and 407.1 eV represent -NO2. These results indicate that POP-EDA interacts with NO... X The reaction process between them.

[0063] Example 2:

[0064] I. Preparation of POP-EDA-1

[0065] (1) 1,3,5-Tribromobenzene (3 mmol), ethylenediamine (4.5 mmol), bis(dibenzylacetone)palladium (0.18 mmol), XPhos (0.18 mmol), and sodium tert-butoxide (3.6 mmol) were added to a Schrank flask, evacuated three times under vacuum, and then purged with nitrogen. Anhydrous tetrahydrofuran (5 mL) was then added, and the mixture was heated to 65 °C and reacted for two days.

[0066] (2) After the reaction is complete, the resulting mixture is washed with deionized water and dichloromethane until neutral. Then, Soxhlet extraction is performed for two days using methanol and chloroform.

[0067] (3) Finally, the polymer was dried in a vacuum oven at 70°C for 12 hours to obtain a grayish-black polymer, called a porous aromatic amine polymer, named POP-EDA-1, with a yield of 15.5%. The yield was low and the stability was relatively poor.

[0068] II. Vacuum Stability Test of POP-EDA-1

[0069] like Figure 10Compared with palladium acetate, the reaction yield of POP-EDA-1 ​​in Example 2 is relatively low. As the final pressure of POP-EDA reaches 2.18 kPa, the final pressure of POP-EDA-1 ​​reaches 2.52 kPa. The stabilizing effect of POP-EDA-1 ​​on nitrocellulose is not as good as that of POP-EDA in Example 1. The reaction rates of the two are roughly the same, but in the early stage of the reaction, their responsiveness to nitrogen oxide concentrations is different. POP-EDA in Example 1 can play a significant stabilizing role at low nitrogen dioxide concentrations.

[0070] Example 3:

[0071] (1) 1,3,5-Tribromobenzene (3 mmol), ethylenediamine (4.5 mmol), palladium acetate (0.18 mmol), XPhos (0.18 mmol), and sodium tert-butoxide (3.6 mmol) were added to a Schranke container, which was evacuated three times under vacuum and then purged with nitrogen. Anhydrous toluene (5 mL) was then added, and the mixture was heated to 110 °C and reacted for two days.

[0072] (2) After the reaction is complete, the resulting mixture is washed with deionized water and dichloromethane until neutral. Then, Soxhlet extraction is performed for two days using methanol and chloroform.

[0073] (3) Finally, the polymer was dried in a vacuum oven at 70°C for 12 hours to obtain a grayish-black polymer, called a porous aromatic amine polymer, with a yield of 5.5%. The yield was very low. This is because toluene has poor solubility in the polymer, making it difficult to form a polymer.

Claims

1. A method for preparing a porous aromatic amine polymer, characterized in that, The porous aromatic amine polymer is synthesized via the Buchwald-Hartwig reaction, specifically including the following steps: Under nitrogen protection, 1,3,5-tribromobenzene, ethylenediamine, palladium catalyst, ligand and base were placed in an anhydrous solvent, heated to 50-110°C and refluxed for more than 48 hours. After the reaction was completed, the mixture was washed, Soxhlet extracted and vacuum dried to obtain the porous aromatic amine polymer.

2. The method as described in claim 1, characterized in that, The palladium catalyst is palladium acetate, or palladium dibenzylacetone, or palladium tribenzylacetone.

3. The method as described in claim 1, characterized in that, The ligands are 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl (XPhos), 2-dicyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (RuPhos), and 2-(dicyclohexylphosphine)-3,6-dimethoxy-2'-4'-6'-tri-1-propyl-1,1'-biphenyl (BrettPhos).

4. The method as described in claim 1, characterized in that, The base is sodium tert-butoxide, potassium carbonate, and cesium carbonate.

5. The method as described in claim 1, characterized in that, The anhydrous solvents are tetrahydrofuran, toluene, N,N'-dimethylformamide, 1,4-dioxane, and dimethyl sulfoxide.

6. The method as described in claim 1, characterized in that, The molar ratio of 1,3,5-tribromobenzene to ethylenediamine is 1:1.5 to 1:2; the molar ratio of 1,3,5-tribromobenzene to palladium acetate is 1:0.01 to 1:0.08; the molar ratio of 1,3,5-tribromobenzene to XPhos is 1:0.01 to 1:0.8; and the molar ratio of 1,3,5-tribromobenzene to sodium tert-butoxide is 1:1.2 to 1:

3.

7. The porous aromatic amine polymer prepared by the method according to any one of claims 1-6.

8. A porous aromatic amine polymer, characterized in that, It has the following structure: n is the repeating unit.

9. Use of the porous aromatic amine polymer prepared by the method of any one of claims 1-6 or the porous aromatic amine polymer of claim 8 as a stabilizer for nitrocellulose.

10. The use as described in claim 9, characterized in that, Porous aromatic amine polymers are doped with nitrocellulose at a mass ratio of 1% to 5%.

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