A diamine monomer, a polyimide polymer, an aromatic polyamide polymer, and a preparation method and use thereof

Abstract

The application belongs to the technical field of high-mechanical-strength polymer materials, and particularly relates to a diamine monomer, a polyimide polymer, an aromatic polyamide polymer, a preparation method and application thereof. The application provides a diamine monomer shown in formula I, and a polyimide polymer (PI) or an aromatic polyamide polymer (PA) prepared by using the diamine monomer. The PI and PA materials provided by the application have good mechanical properties, and have good application prospects in the fields of composite materials and light-weight bulletproof clothes.

Description

Technical Field

[0001] This invention belongs to the field of high mechanical strength polymer materials technology, specifically relating to a diamine monomer, a polyimide polymer, an aromatic polyamide polymer, and their preparation methods and uses. Background Technology

[0002] High-heat-resistant, high-performance polymers are organic polymer materials with advantages such as high strength and modulus, excellent heat resistance and stability, high mechanical properties, good processability, and low water absorption. They have wide applications in both civilian and military fields. Polyimide (PI) and fully aromatic polyamide (PA) are typical representatives of high-heat-resistant, high-performance polymers. Due to their high heat resistance, wear resistance, and lightweight properties, they have wide applications in composite materials and lightweight bulletproof vests. Further improving their mechanical properties has always been one of the important goals pursued in this field.

[0003] The design and regulation of the chemical structure, hydrogen bonds, and crystalline aggregation state of polymers are effective ways to improve their mechanical properties. Hydrogen bonds are dynamic chemical bonds with strength between van der Waals forces and chemical bonds. Their interaction strength and ordered stacking are important factors in improving comprehensive properties such as tensile strength, modulus, and compressive strength. Introducing hydrogen bond interactions into the main chain of PI and PA polymers can enhance the interaction between molecular chains, thereby improving the mechanical strength of the polymer. In addition, rigid rod-shaped benzoxazole structures, such as benzimidazole and benzoxazole, have high planarity and conjugation interactions. This can enhance the π-π interaction and charge transfer interaction (CT interaction) between molecular chains, thereby improving the thermal properties and mechanical strength of PI and PA polymers. In the 1970s, the All-Union Scientific Research and Design Institute for Man-Made Fibers replaced part of the p-phenylenediamine (PPD) structure with 5(6)-amino-2-(4-aminobenzene)benzimidazole (PABZ) diamine monomer containing a benzimidazole structure to develop a new type of aromatic polyamide fiber (PBIA), commercially known as Armos. The tensile strength of PBIA increased to 4.8 GPa, the Young's modulus increased to 145 GPa, and the compressive strength increased to 0.39 GPa. The tensile strength, Young's modulus and compressive modulus were all improved.

[0004] With the rapid development of science and technology, there is an urgent need for polymer materials with higher mechanical strength, which places higher demands on PI and PA polymer materials. How to design the molecular structure of PI and PA polymer materials, control their chemical structure and aggregation state structure, and prepare PI and PA polymers with superior mechanical strength to meet the needs of applications in composite materials and lightweight bulletproof vests is a problem that urgently needs to be solved. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a diamine monomer, a polyimide polymer, an aromatic polyamide polymer, and their preparation methods and uses, with the aim of providing PI and PA materials with higher mechanical strength.

[0006] The compound represented by Formula I, or its salt or solvate, has the following structural formula:

[0007]

[0008] Among them, ring A is selected from benzene ring or 5-6 membered heteroaromatic ring;

[0009] R1 is selected from CH or N respectively, and at least one of R1 is N;

[0010] R2 is selected from hydrogen, hydroxyl, mercapto, carboxyl, or halogen.

[0011] Preferably, ring A is selected from benzene ring or pyridine ring; all R1s include 3 CH and 1 N; and R2 is selected from hydrogen or hydroxyl.

[0012] Preferably, the compound has the following structural formula:

[0013]

[0014] The present invention also provides a method for preparing the above-mentioned compound, or its salt, or its solvate, comprising the following steps:

[0015] Step 1: Raw material 1 undergoes a nitration reaction to obtain intermediate 1, and intermediate 1 undergoes a reduction reaction to obtain intermediate 3;

[0016]

[0017] or,

[0018] Raw material 2 undergoes ammonolysis to obtain intermediate 2, and intermediate 2 undergoes reduction to obtain intermediate 3;

[0019]

[0020] In raw material 2, X is selected from halogens; at least two groups among X, nitro, and amino are located in the ortho position;

[0021] Step 2: Intermediate 3 reacts with raw material 3 to obtain the compound shown in Formula I;

[0022]

[0023] Preferably, in step 1, the conditions for the nitration reaction of raw material 1 include: a reaction temperature of 30–80°C; and / or a reaction time of 1–3 hours; and / or the reaction is carried out under the action of an acid, wherein the acid is selected from one or more combinations of concentrated sulfuric acid, sulfuric acid, fuming sulfuric acid, and glacial acetic acid; the molar ratio of raw material 1 to acid is 1.0:5.0–10.0; and / or the reaction solvent is selected from one or more combinations of dichloromethane, trichloromethane, or carbon tetrachloride; and / or the nitrating agent is selected from at least one of nitrate, sodium nitrate, and potassium nitrate; and / or the molar ratio of raw material 1 to nitrating agent is 1.0:1.0–5.0.

[0024] And / or, the conditions for the ammonolysis reaction of raw material 2 include: a reaction temperature of 60–210℃; and / or, a reaction time of 0.5–24.0 h; and / or, the ammonolysis reagent is one or a combination of two or more of ammonia water, liquid ammonia, and ammonia gas, and the ammonolysis catalyst is a metal catalyst or metal oxide; and / or, the reaction solvent is selected from one or a combination of two or more of ethanol, methanol, butanol, isobutanol, and water; and / or, the molar ratio of raw material 2 to ammonolysis reagent is 1.0:1.0–10.0;

[0025] And / or, the conditions for the reduction reaction of intermediate 1 or intermediate 2 include: a reaction temperature of 20 to 120°C; and / or, a reaction time of 3 to 6 hours; and / or, the reducing agent is selected from hydrogen, and the catalyst for the reaction is selected from a metal catalyst or a metal oxide catalyst; and / or, the reaction solvent is selected from one or more combinations of ethanol, methanol, butanol, isobutanol, and water.

[0026] And / or, in step 2, the reaction conditions include: the reaction is carried out under the action of an antioxidant, and the reaction temperature is 170-220℃; and / or, the reaction time is 3-6 hours; and / or, the reaction is carried out under the action of an antioxidant, wherein the antioxidant is selected from SnCl2·H2O, Sn powder, or a combination of two; and / or, the reaction is carried out under the action of a dehydrating agent, wherein the dehydrating agent is selected from phosphorus pentoxide; and / or, the reaction solvent is a strong acid solvent, wherein the strong acid solvent is selected from polyphosphoric acid or methanesulfonic acid, or a combination of two; and / or, the molar ratio of intermediate 3 to raw material 3 is 1:0.95-1.05.

[0027] The present invention also provides the use of the above-mentioned compounds, or their salts, or their solvates, as polymeric monomers in the preparation of polymeric materials.

[0028] This invention also provides polymer materials prepared from the above-mentioned compounds, their salts, or their solvates, wherein the polymer materials have the following structural formula:

[0029]

[0030] in,

[0031] L1 is selected from aromatic dianhydrides with the removal of acid anhydride residues;

[0032] L2 is selected from aromatic diacyl chlorides with the acyl chloride residue removed;

[0033] n is an integer greater than or equal to 2.

[0034] Preferably, L1 is selected from at least one of the following structures:

[0035]

[0036] L2 is selected from at least one of the following structures:

[0037]

[0038] The present invention also provides a method for preparing the above-mentioned polymer material, comprising the following steps: polycondensing the compound shown in Formula I with raw material 4, or polycondensing the compound shown in Formula I with raw material 5, to obtain the polymer material.

[0039]

[0040] The temperature conditions for the polycondensation are 80–350°C.

[0041] Preferably, the reaction solvent for polycondensation is N,N-dimethylacetamide, and the molar ratio of the compound shown in Formula I to raw material 4 is 1:1. The polycondensation process is as follows: N,N-dimethylacetamide, the compound shown in Formula I and raw material 4 are mixed and stirred for 10 hours to obtain a polyamic acid solution with a solid content of 12 wt%. The polyamic acid solution is coated on the substrate surface and cured according to the following procedure: drying at 80°C for 1 hour, holding at 120°C for 2 hours at a heating rate of 5°C / min, continuing to heat to 220°C and holding for 1 hour, and finally holding at 350°C for 0.5 hours to obtain a polyimide polymer film.

[0042] Preferably, the molar ratio of the compound shown in Formula I to raw material 5 is 1:1; the polycondensation process is as follows: N,N-dimethylacetamide containing 3.5 wt% LiCl, the compound shown in Formula I, and raw material 5 are mixed and stirred for 4 h to obtain a polyamic acid solution with a solid content of 4 wt%. The polyamic acid solution is coated on the substrate surface and cured according to the following procedure: immersing in a coagulation bath of a mixed solvent of N,N-dimethylacetamide and water in a volume ratio of 1:1 for 15 min, soaking in distilled water at 80°C for 2 h, drying at 80°C for 1 h, and finally maintaining at 360°C for 0.5 h to obtain a film of aromatic polyamide polymer.

[0043] Preferably, the molar ratio of the compound shown in Formula I to raw material 5 is 1:1; the polycondensation process is as follows: N,N-dimethylacetamide containing 3.5 wt% LiCl, the compound shown in Formula I, and raw material 5 are mixed and stirred for 4 h to obtain a polyamic acid solution with a solid content of 4 wt%. The polyamic acid solution is washed in water at 80 °C in a wet spinning equipment by passing it through a mixed solvent of N,N-dimethylacetamide and water in volume ratios of 1:1 and 1:6, respectively, dried at 180 °C, and stretched at 410 °C to obtain fibers of aromatic polyamide polymer.

[0044] The present invention also provides the use of the above-mentioned polymer material in the preparation of high-strength composite materials or lightweight bulletproof vests.

[0045] By adopting the above technical solution, the following beneficial effects can be achieved:

[0046] 1. This invention provides a diamine monomer (Formula I) containing an imidazole [4,5-b]pyridine structure. When this diamine monomer is used to prepare PI and PA polymers, on the one hand, the introduction of imidazole and pyridine increases the number of hydrogen bonding sites in polyimide and aromatic polyamide, enhances hydrogen bonding, and improves the mechanical strength of the polymer; on the other hand, the introduction of the imidazole [4,5-b]pyridine structure results in a higher planarity and conjugation interaction of the molecular chain, which enhances the π-π interaction and CT interaction between molecular chains, further improving the thermal properties and mechanical strength of PI and PA polymers.

[0047] 2. The imidazole [4,5-b]pyridine diamine monomer of the present invention is applied to polyimide polymers or aromatic polyamide polymers. The polymers not only have excellent mechanical strength, but also maintain good film-forming and fiber-forming processability. This material is expected to be used in composite materials and lightweight bulletproof vests.

[0048] 3. This invention opens up new synthetic processes and methods for synthesizing diamine monomers containing imidazole [4,5-b] and pyridine structures;

[0049] 4. The present invention proposes two synthetic routes for the preparation of diamine monomers. In the preferred scheme, both synthetic routes can be controlled and optimized by combining process parameters to determine the material addition ratio, thereby achieving high yield and high production to prepare diamine monomers containing imidazole [4,5-b] and pyridine structures.

[0050] In summary, the technical solution of this invention has excellent application prospects.

[0051] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0052] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0053] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0054] Figure 1 It is the 2,6-diamino-3-nitropyridine prepared in Example 1. 1 1H NMR spectrum, the deuterated reagent is DMSO-d6;

[0055] Figure 2 It is the 2,3,6-triaminopyridine prepared in Example 1. 1 1H-NMR spectrum and mass spectrum, the deuterated reagent is DMSO-d6;

[0056] Figure 3 This is the mass spectrum of 2,3,6-triaminopyridine prepared in Example 1;

[0057] Figure 4 It is the 2-amino-3,5-dinitropyridine prepared in Example 1. 1 1H NMR spectrum, the deuterated reagent is DMSO-d6;

[0058] Figure 5 It is the 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine prepared in Example 1. 1 1H NMR spectrum, the deuterated reagent is DMSO-d6;

[0059] Figure 6 This is a high-resolution mass spectrum of 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine prepared in Example 1;

[0060] Figure 7 It is the 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine prepared in Example 1. 1 1H NMR spectrum, the deuterated reagent is DMSO-d6;

[0061] Figure 8 This is a high-resolution mass spectrum of 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine prepared in Example 1. Detailed Implementation

[0062] In the following examples and experimental cases, reagents and raw materials not specifically described are all commercially available products.

[0063] Example 1: Imidazole-[4,5-b]pyridine diamine monomer and its preparation method

[0064] I. Preparation of 2,3,6-triaminopyridine

[0065] (I) Synthetic Route 1: Triaminopyridine is prepared by first undergoing ammonolysis followed by nitro reduction.

[0066] The reaction formula is as follows:

[0067]

[0068] In a 250 ml pressurized hydrothermal reactor (6 MPa pressure resistance), weigh 10.0 g of 2-amino-6-chloro-3-nitropyridine, 5.0 g of cuprous chloride, and 100 ml of ammonia water. While magnetically stirring, slowly heat to 100 °C. Stop the reaction after 3 hours. After cooling to room temperature, wash several times with deionized water until the filtrate changes from green to yellow. Then dry the filter residue in a vacuum oven to obtain 8.51 g of yellow 2,6-diamino-3-nitropyridine powder (yield 96%).

[0069] In a 250 mL high-pressure reactor (6 MPa pressure resistance) equipped with a thermometer, stirrer, and pressure gauge, 10.0 g of 2,6-diamino-3-nitropyridine was weighed and dispersed in 100 mL of ethanol. The mixture was bubbled for 30 min to remove air from the solution. After bubbling, 100 mg of Pd / C catalyst was added. Hydrogen gas was introduced into the reactor, the pressure was adjusted to 1.0 MPa, the temperature was raised to 80 °C, and the reaction was stirred for 3 h. After the reaction, the mixture was cooled to 60 °C and filtered. The filtrate was concentrated by vacuum distillation and then dried under vacuum to obtain 7.72 g of orange-yellow 2,3,6-triaminopyridine (96% yield) solid powder. Alternatively, hydrogen chloride gas was introduced to obtain white 2,3,6-triaminopyridine hydrochloride powder.

[0070] The obtained 2,6-diamino-3-nitropyridine 1 H-NMR (DMSO-d6) spectrum shown Figure 1 In the NMR spectrum, the peaks correspond one-to-one with the chemical structure. By comparing the NMR peaks of the reactants and products, it was found that after converting chlorine to an amino group, the electronic effect of the pyridine ring changed significantly, the overall electron cloud density increased, and the NMR peaks shifted to higher fields, from 8.39 ppm and 6.67 ppm of the reactants to 7.97 ppm and 5.91 ppm of the products. This proves the successful synthesis of the product. Detailed data for 2,6-diamino-3-nitropyridine are as follows: 1H NMR (400MHz, DMSO-d6) δ7.97(d,J=9.2Hz,1H),7.58(s,2H),7.26(s,2H),5.91(d,J=9.2Hz,1H).

[0071] The obtained 2,3,6-triaminopyridine 1 H-NMR (DMSO-d6) spectrum shown Figure 2 In the 1H NMR spectrum, the peaks corresponded one-to-one with the chemical structures. By comparing the NMR peaks of the reactants and products, it was found that converting the nitro group to an amino group increased the electron cloud density of the pyridine ring, causing the NMR peak to shift to a higher field, moving left from 7.97 ppm to 7.66 ppm. Since the amino peak was an enveloped peak hidden within the baseline, its structure could not be accurately characterized. The mass spectrometry data further confirmed the successful synthesis of 2,3,6-triaminopyridine.

[0072] (II) Synthetic Route 2: Triaminopyridine is prepared by first nitration followed by nitro reduction.

[0073] The reaction formula is as follows:

[0074]

[0075] Weigh 50g of concentrated sulfuric acid into a 250ml three-necked round-bottom flask. Place the flask in an ice-water bath at a constant temperature of 0-5℃ and stir slowly with a mechanical stirrer. Weigh 5g of 2-amino-3-nitropyridine (or 2-amino-5-nitropyridine) and add it in small, frequent additions, strictly controlling the temperature at 0-5℃. After complete dissolution, a yellow sulfuric acid solution is obtained. Weigh 3.03g (1.01eq) of sodium nitrate and add it in small, frequent additions, strictly controlling the temperature at 0-5℃, as excessively high temperatures will produce NO2 gas. Then, slowly raise the temperature to 40℃ and stir for 2 hours to obtain a red solution. After the reaction is complete, slowly pour the reaction solution into ice water, filter, and wash with alkali. Recrystallization from tetrahydrofuran yields 6.07g of yellow powder 2-amino-3,5-dinitropyridine (yield 92%). The reagent amounts and conditions for the hydrogenation reaction of 2-amino-3,5-dinitropyridine are the same as in Part (I), and will not be repeated here.

[0076] Both raw materials can yield 2-amino-3,5-dinitropyridine, which 1 H-NMR (DMSO-d6) spectrum shown Figure 3 In the 1H NMR spectrum, the peaks correspond one-to-one with the chemical structure. The amino group's peak splits into two because the amino group forms an intramolecular hydrogen bond with the ortho-nitro group, resulting in inconsistent chemical environments for the two hydrogen atoms in the amino group. The multiplet report for 2-amino-3,5-dinitropyridine is as follows: 1H NMR (400MHz, DMSO-d6) δ9.27 (s, 1H), 9.18 (d, J = 2.6Hz, 1H), 8.96 (d, J = 2.6Hz, 1H), 8.70 (s, 1H).

[0077] In the above reaction steps, this embodiment demonstrates the preparation of 2,3,6-triaminopyridine and 2,3,5-triaminopyridine using two different methods, intended to illustrate that both methods can effectively prepare triaminopyridine compounds. In practical applications, those skilled in the art can select between ammonolysis and nitration reactions based on the different substituents and aromatic ring electron densities of the raw materials, thereby preparing precursors of triaminopyridine, which can then be obtained through nitro reduction or halogen reduction.

[0078] II. Preparation of Diamine Monomers

[0079] (I) Preparation of 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine

[0080] The reaction formula is as follows:

[0081]

[0082] In a 1000ml three-necked flask, 120g of polyphosphoric acid and 12.0g of P2O5 were weighed and placed in an oil bath at 60℃. The mixture was mechanically stirred and homogenized under nitrogen atmosphere, followed by the addition of 0.25g of the antioxidant SnCl2·2H2O. The temperature was then raised to 80℃, and 6.0g of 2,3,6-triaminopyridine was added. After thorough stirring, 7.40g (1.0 eq) of 4-aminosalicylic acid was added and stirred until homogenized. The temperature was then gradually increased to 195℃. The reaction was stopped after 6 hours at this high temperature. The reaction solution was cooled to 120℃ and poured into a vigorously stirred ice-water bath. The mixture was then filtered under reduced pressure to obtain the residue. The residue was dispersed in water, washed with NaHCO3 aqueous solution to remove excess phosphoric acid, and the pH was adjusted to 8. The residue was then obtained again by vacuum filtration; the residue was a deep yellow solid. Recrystallization from DMF yielded a dark yellow 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine powder (70% yield).

[0083] The obtained 5-amino-4-(2-hydroxy-4-amino)imidazol[4,5-b]pyridine 1 H-NMR (DMSO-d6) spectrum shown Figure 4 In the NMR spectrum, the peaks correspond one-to-one with the chemical structure. The multiplet report for 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine is as follows: 1¹H NMR (400MHz, DMSO-d6) δ 12.85 (s, 1H), 12.60 (s, 1H), 7.58 (dd, J = 14.8, 8.5Hz, 2H), 6.36 (d, J = 8.5Hz, 1H), 6.21–6.08 (m, 2H), 5.83 (s, 2H), 5.56 (s, 2H). Furthermore, because pyridine-imidazole and the adjacent benzene ring can rotate, the phenolic hydroxyl group can form an intramolecular hydrogen bond with the nitrogen of the imidazole, resulting in a stable configuration and thus a stable 5 / 6-position isomer. The ¹H NMR spectrum shows two sets of ¹H NMR peaks for 5-amino-4-(2-hydroxy-4-amino)imidazole [4,5-b]pyridine. The spectrum shows a small peak next to each main peak, representing the NMR peaks of the two configurations. The high-resolution mass spectrum of 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine is shown in the figure. Figure 5 In the study, the predicted molecular weight was M+H=242.1042, but the actual detected molecular weight was 242.1031.

[0084] (II) Preparation of 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine

[0085] The reaction formula is as follows:

[0086]

[0087] In a 1000ml three-necked flask, 120g of polyphosphoric acid and 12.0g of P2O5 were weighed and placed in an oil bath at 60℃. The mixture was mechanically stirred and homogenized under nitrogen atmosphere, and then 0.25g of the antioxidant SnCl2·2H2O was added. The temperature was then raised to 80℃, and 6.0g of 2,3,6-triaminopyridine was added. After stirring until homogenized, 6.62g (1.0eq) of p-aminobenzoic acid was added, and the mixture was stirred until homogenized. The temperature was then gradually increased to 195℃. The reaction was stopped after 6 hours at this high temperature. The reaction solution was cooled to 120℃ and poured into a vigorously stirred ice-water bath. The mixture was then filtered under reduced pressure to obtain the residue. The residue was dispersed in water, washed with NaHCO3 aqueous solution to remove excess phosphoric acid, and the pH was adjusted to 8. The residue was then filtered again under reduced pressure. The residue was a yellow solid, which was recrystallized from methanol to obtain a pale yellow 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine powder.

[0088] The obtained 5-amino-4-(4-amino)imidazol[4,5-b]pyridine 1 H-NMR (DMSO-d6) spectrum shown Figure 6In the 1H NMR spectrum, the peaks correspond one-to-one with the chemical structure. The multiplet report for 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine is as follows: 1H NMR (400MHz, DMSO-d6) δ 12.27 (s, 1H), 7.79–7.72 (m, 2H), 7.51 (d, J = 8.5Hz, 1H), 6.66–6.58 (m, 2H), 6.30 (d, J = 8.4Hz, 1H), 5.66 (s, 2H), 5.49 (s, 2H). The high-resolution mass spectrum of 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine is shown in [image / image / image]. Figure 7 In the study, the predicted molecular weight was M+H=226.1093, while the actual detected molecular weight was 226.1084.

[0089] As can be seen from the above reaction steps, this embodiment successfully prepared two diamine monomers, namely 5-amino-4-(2-hydroxy-4-amino)imidazol[4,5-b]pyridine and 5-amino-4-(4-amino)imidazol[4,5-b]pyridine.

[0090] Example 2: Polyimide polymer film

[0091] I. Preparation Method

[0092] This embodiment is based on the preparation of a polyimide polymer from a diamine monomer containing an imidazole [4,5-b] and pyridine structure. The diamine monomer containing the imidazole [4,5-b] and pyridine structure is selected from 5-amino-4-(2-hydroxy-4-amino)imidazole [4,5-b]pyridine and 5-amino-4-(4-amino)imidazole [4,5-b]pyridine obtained in Example 1 above.

[0093] The reaction formula is as follows:

[0094]

[0095] Under a nitrogen atmosphere, add 100 ml of N,N-dimethylacetamide to a 250 ml three-necked flask.

[0096] (DMAc) solvent, with the temperature controlled below 10℃, add 0.01mol of 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine or 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine, as shown in reaction formulas (11) and (12), respectively. After vigorous mechanical stirring until the diamine is completely dissolved, add 0.01mol of aromatic dianhydride in small amounts several times, and continue mechanical stirring for 10h to obtain a viscous polyamic acid solution with a solid content of 12wt%. Coat the solution onto a flat and clean glass plate using a coating machine, dry it in a vacuum oven at 80℃ for 1h, maintain the temperature at 120℃ for 2h at a heating rate of 5℃ / min, continue heating to 220℃ and maintain for 1h, and finally maintain at 350℃ for 0.5h to complete the final imidization, thus obtaining a polyimide polymer film.

[0097] In this embodiment, the aromatic dianhydrides selected are 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), diphenyl ether tetracarboxylic dianhydride (ODPA), 2,2ˋ-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA), and 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) (BPADA), with the following specific structural formulas:

[0098]

[0099] II. Performance Characterization

[0100] The mechanical properties were tested in accordance with the requirements of GB / T 13542.6-2006 "Electrical Insulating Films - Part 6: Polyimide Films for Electrical Insulation". Table 1 shows the properties of PI polymer films of the 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine system prepared in this example using different dianhydrides. By comparing the tensile strength, tensile modulus, and elongation at break of PI films with different chemical structures, the PI films obtained by polymerization of BPDA and 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine (tensile strength 280 MPa, tensile modulus 5435 MPa, elongation at break 10.5%) and ODPA-type PI polymers (tensile strength 266 MPa, tensile modulus 4836 MPa, elongation at break 12.1%) are superior to those of BPDA and PABZ system PI (tensile strength 260 MPa, tensile modulus 5351 MPa, elongation at break 12.5%). Due to the high flexibility of the 6FDA-type PI polymer and BPADA-type PI molecular chains, the tensile strength is slightly lower, but the elongation at break is slightly higher.

[0101] Table 2 shows the properties of PI polymer films prepared using the 5-amino-4-(4-amino)imidazole[4,5-b]pyridine system through this example, with different dianhydrides selected. By comparing the tensile strength, tensile modulus, and elongation at break of PI films with different chemical structures, the PI films obtained by polymerization of BPDA and 5-amino-4-(4-amino)imidazole[4,5-b]pyridine exhibit superior properties (tensile strength 273 MPa, tensile modulus 5354 MPa, elongation at break 10.9%) compared to PI films from the BPDA and PABZ systems.

[0102] The preparation method of PI for the control samples BPDA and PABZ used in the above experiment is the same as that in the first part of this embodiment, except that the polymerization monomers are different, as detailed below:

[0103]

[0104] In summary, the introduction of imidazole[4,5-b]pyridine structure can enhance the mechanical strength of PI polymer materials.

[0105] Table 1

[0106] BPDA 280 5435 10.5 ODPA 266 4836 12.1 6FDA 220 4547 13.7 BPADA 214 3654 15.2

[0107] Table 2

[0108] BPDA 273 5354 10.9 ODPA 246 4532 12.6

[0109] Example 3: Aromatic polyamide polymer film

[0110] I. Preparation Method

[0111] In this embodiment, an aromatic polyamide polymer was prepared based on a diamine monomer containing an imidazole [4,5-b]pyridine structure. The diamine monomer containing an imidazole [4,5-b]pyridine structure was selected from 5-amino-4-(2-hydroxy-4-amino)imidazole [4,5-b]pyridine and 5-amino-4-(4-amino)imidazole [4,5-b]pyridine obtained in Example 1 above.

[0112] The reaction formula is as follows:

[0113]

[0114] Under a nitrogen atmosphere, add 100 ml of N,N-dimethylacetamide (DMAc) solution containing 3.5 wt% LiCl to a 250 ml three-necked flask. Maintain the temperature below 10 °C, then add 0.0025 mol of 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine and 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine. Stir vigorously until the diamine is completely dissolved, then add 0.0 mol of DMAc solution in small, repeated additions. 0.25 mol of terephthaloyl chloride (TPC) was added and mechanically stirred for 4 h to obtain a viscous polyamic acid solution with a solid content of 4 wt%. The solution was coated onto a flat and clean glass plate using a coating machine, immersed in a coagulation bath of DMAc:water = 1:1 (volume ratio) mixed solvent for 15 min, then soaked in distilled water at 80 °C for 2 h, and then dried in a vacuum oven at 80 °C for 1 h. Finally, the film of aromatic polyamide polymer was obtained by maintaining the temperature at 360 °C for 0.5 h.

[0115] II. Performance Characterization

[0116] Referring to the requirements of GB / T 13542.6-2006 "Electrical Insulating Films Part 6: Polyimide Films for Electrical Insulation", various mechanical properties were tested. By comparing the tensile strength, tensile modulus, and elongation at break of PA films with different chemical structures, the performance of the 5-amino-4-(2-hydroxy-4-amino)imidazol[4,5-b]pyridine system (tensile strength 507 MPa, tensile modulus 8193 MPa, elongation at break 8.2%) and the performance of the 5-amino-4-(4-amino)imidazol[4,5-b]pyridine system (tensile strength 425 MPa, tensile modulus 7124 MPa, elongation at break 9.2%) were superior to those of the PABZ system PA (tensile strength 356 MPa, tensile modulus 6520 MPa, elongation at break 10.3%).

[0117] The preparation method of PA in the control sample PABZ system used in the above experiment is the same as that in the first part of this embodiment, except that the polymerization monomer is different, as detailed below:

[0118]

[0119] Example 4: Aromatic polyamide polymer fiber

[0120] I. Preparation Method

[0121] The viscous polyamic acid solution obtained in Example 3 was subjected to coagulation in a wet spinning equipment in a coagulation bath containing a DMAc:water mixture of 1:1 and 1:6 (volume ratio), followed by washing in distilled water at 80°C, drying the remaining moisture in an oven at 180°C, and finally high-temperature stretching at 410°C to obtain aromatic polyamide fibers.

[0122] II. Performance Characterization

[0123] The mechanical properties were tested according to the requirements of GB / T 14344—2022 "Test Method for Tensile Properties of Chemical Fiber Filaments". By comparing the tensile strength, tensile modulus and elongation at break of PA fibers with different chemical structures, the 5-amino-4-(2-hydroxy-4-amino)imidazolium[4,5-b]pyridine system (tensile strength 5.2 GPa, tensile modulus 178 GPa, elongation at break 2.5%) and the 5-amino-4-(4-amino)imidazolium[4,5-b]pyridine system (tensile strength 4.8 GPa, tensile modulus 154 GPa, elongation at break 3.4%) were superior to those of PA fiber with PABZ system (tensile strength 4.5 MPa, tensile modulus 145 MPa, elongation at break 4.5%).

[0124] The preparation method of PA in the control sample PABZ system used in the above experiment is the same as that in the first part of this embodiment, except that the polymerization monomer is different, as detailed below:

[0125]

[0126] In summary, the mechanical properties of the polyimide polymers and aromatic polyamide polymers prepared from the above embodiments based on imidazole [4,5-b]pyridine diamine monomers are all improved. Preferably, BPDA-type PI films, TPC-type PA films, and TPC-type PA fibers show more significant improvements in mechanical strength. It is evident that the diamine monomers provided by this invention can indeed produce PI and PA materials with better mechanical properties, showing great promise for applications in composite materials and lightweight bulletproof vests.

Claims

1. A polymer material, characterized in that, The polymer material has the following structural formula: or The polymer material is prepared from the monomer shown in Formula I, where Formula I is selected from: Formula I The structures of rings A, R1, and R2 make the structure of the compound described in Formula I selected from: 、 ； n is an integer greater than or equal to 2; L1 is selected from: ； L2 is selected from: 。 2. The method for preparing the polymer material according to claim 1, characterized in that, The process includes the following steps: polycondensing the compound shown in Formula I with raw material 4, or polycondensing the compound shown in Formula I with raw material 5, to obtain the product. or Wherein, rings A, R1, R2, L1, L2, and n are as described in claim 1; Formula I is as described in claim 1; The temperature conditions for the polycondensation are 80~350 ℃.

3. The use of the polymer material of claim 1 in the preparation of high-strength composite materials or lightweight bulletproof vests.

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