Aromatic diamine monomers, processes for their preparation and use

Abstract

The application discloses aromatic diamine monomers, and a preparation method and application thereof, and the aromatic diamine monomers comprise at least one of compounds as shown in formula I, formula II and formula III: formula I; formula II; and formula III. The application combines a rigid skeleton of “2,2,4,4-tetramethylcyclobutane” and a high reactivity structural unit of “aromatic diamine” for the first time, and creates a new type of compound. The aromatic diamine monomers can be used for preparing high-performance polymer materials such as polyimide, polyamide and polyurethane, and the combination of an alicyclic structure and an aryl ether structure in the aromatic diamine monomers makes the aromatic diamine monomers have a good application prospect in the field of high-performance polymer materials such as polyimide, polyamide and polyurethane.

Description

Technical Field

[0001] This application belongs to the field of organic synthesis and polymer materials technology, specifically relating to an aromatic diamine monomer, its preparation method and application. Background Technology

[0002] Aromatic diamines are an important class of organic chemical intermediates. The two amino functional groups in their molecular structure endow these compounds with rich reactivity, making them widely used in many fields such as pharmaceutical intermediates, pesticide chemicals, dyes and pigments, curing agents, and the synthesis of polymer materials. The amino groups on the aromatic rings of aromatic diamines can participate in a variety of chemical reactions such as acylation, sulfonation, alkylation, and diazotization, making them essential basic raw materials for constructing complex organic molecular skeletons.

[0003] However, the types of aromatic diamine compounds in the existing technology are limited and their performance is poor. Therefore, it is necessary to develop a new type of aromatic diamine monomer. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art. Therefore, the purpose of this application is to provide an aromatic diamine monomer, its preparation method, and its application.

[0005] In one aspect of this application, an aromatic diamine monomer is provided. According to embodiments of this application, the aromatic diamine monomer comprises at least one of the compounds shown in Formula I, Formula II, and Formula III: Formula I; Formula II; Formula III.

[0006] In addition, the aromatic diamine monomer according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the aromatic diamine monomer... 1 The 1H NMR spectrum includes: a singlet with a chemical shift of 5.5 ppm, multiplets with chemical shifts of 6.61 ppm to 7.10 ppm, and a singlet with a chemical shift of 0.9 ppm.

[0007] According to the embodiments of this application, the aromatic diamine monomer combines the rigid skeleton of "2,2,4,4-tetramethylcyclobutane" with the highly reactive structural unit of "aromatic diamine," creating a novel class of compounds. The aromatic diamine monomer of this application contains two reactive amino groups in its molecular structure, making it suitable for use as a diamine monomer in the preparation of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. Furthermore, the combination of alicyclic and aromatic ether structures in the aromatic diamine monomer of this application gives it promising application prospects in the field of high-performance polymer materials such as polyimides, polyamides, and polyurethanes.

[0008] In a second aspect of this application, a method for preparing the aromatic diamine monomer of the first aspect is provided. According to embodiments of this application, the method includes: (1) 2,2,4,4-Tetramethyl-1,3-cyclobutanediol, fluoronitrobenzene, basic catalyst and first organic solvent are mixed and subjected to nucleophilic substitution reaction to obtain 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane; (2) The 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane, palladium on carbon catalyst, hydrazine hydrate and a second organic solvent are mixed and subjected to catalytic transfer hydrogenation reaction to obtain the aromatic diamine monomer.

[0009] The method for preparing aromatic diamine monomers according to the embodiments of this application, for the first time, uses 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) as a starting material and synthesizes an aromatic diamine monomer (i.e., 1,3-bis(aminophenoxy)-2,2,4,4-tetramethylcyclobutane) via a two-step process. This compound is a novel aromatic diamine monomer. The synthetic route of this application employs nucleophilic substitution and palladium on carbon / hydrazine hydrate catalytic transfer hydrogenation reduction, which is simple to operate, has mild reaction conditions, and does not require high-pressure hydrogen equipment, making it suitable for industrial-scale production. Furthermore, CBDO is already available on an industrial scale, and fluoronitrobenzene, palladium on carbon, and hydrazine hydrate are all stable industrial raw materials, making production costs controllable.

[0010] In addition, the method for preparing aromatic diamine monomers according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, in the nucleophilic substitution reaction, the fluoronitrobenzene includes any one of p-fluoronitrobenzene, m-fluoronitrobenzene, and o-fluoronitrobenzene; and / or, the basic catalyst includes at least one of potassium carbonate, cesium carbonate, potassium hydroxide, and sodium hydride; and / or, the first organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0011] In some embodiments of this application, in the nucleophilic substitution reaction, the molar ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol to the fluoronitrobenzene is 1:(2~3); and / or, the molar ratio of the basic catalyst to the 2,2,4,4-tetramethyl-1,3-cyclobutanediol is (2~3):1.

[0012] In some embodiments of this application, the nucleophilic substitution reaction is carried out at a temperature of 80°C to 150°C for a duration of 8 hours to 24 hours.

[0013] In some embodiments of this application, in the catalytic transfer hydrogenation reaction, the mass of the palladium catalyst on carbon is 1% to 10% of the mass of 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane; and / or, the mass fraction of palladium in the palladium catalyst on carbon is 5% to 10%; and / or, the molar ratio of hydrazine hydrate to 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane is (3 to 10):1; and / or, the mass concentration of hydrazine hydrate is 80% to 100%; and / or, the second organic solvent includes at least one of methanol, ethanol, tetrahydrofuran, ethyl acetate, and water.

[0014] In some embodiments of this application, the temperature of the catalytic transfer hydrogenation reaction is 70°C to 100°C, and the reaction time is 4 hours to 12 hours.

[0015] In a third aspect of this application, the application of an aromatic diamine monomer prepared by the method of the first aspect or the method of the second aspect in the preparation of polyimides, polyamides, and polyurethanes is proposed. The combination of alicyclic and aromatic ether structures in the aromatic diamine monomer of this application makes it promising for application in the field of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. In particular, because the aromatic diamine monomer of this application simultaneously possesses rigid cyclobutane and four methyl side groups in its molecule, when used to prepare polymers such as polyimides, it can impart comprehensive properties such as high transparency, high glass transition temperature, good solubility, and low dielectric constant to the materials. This provides a new monomer selection for the development of novel polyimides, polyamides, and other materials with tunable properties.

[0016] In some embodiments of this application, the aromatic diamine monomer and the dianhydride monomer are subjected to a polycondensation reaction to obtain a polyimide material.

[0017] In some embodiments of this application, the temperature of the polycondensation reaction is -10℃ to 60℃, and the time is 4 hours to 24 hours; the glass transition temperature of the polyimide material is 320℃ to 400℃, the transmittance of the polyimide material at 450nm is ≥85%, and the dielectric constant of the polyimide material at 1MHz is 3.0 to 3.5.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The aromatic diamine monomer obtained in Example 1 of this application 1 H NMR spectrum; Figure 2 The infrared spectrum is shown for the aromatic diamine monomer obtained in Example 1 of this application. Detailed Implementation

[0020] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0021] This application is based on the inventor's following discovery: The inventors discovered that introducing an alicyclic skeleton, particularly a four-membered ring system with a rigid ring structure, into the molecular structure of aromatic diamine compounds can significantly alter the spatial configuration and electron cloud distribution of the molecule, thereby endowing the final product with unique physicochemical properties. As the smallest carbocyclic system, the cyclobutane structure's unique four-membered ring strain, rigid conformation, and the spatial arrangement of substituents have a significant impact on the reactivity and thermal stability of the compound. Therefore, developing novel aromatic diamine compounds containing cyclobutane structural units is of great significance for enriching the structural types of organic intermediates and expanding the synthetic routes for functional compounds with cyclobutane skeletons.

[0022] 2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) is a tertiary diol containing a cyclobutane skeleton. Its molecular structure exhibits the following notable characteristics: first, the four-membered cyclobutane ring imparts strong molecule rigidity; second, the four methyl substituents at the 2,2,4,4-positions provide significant steric hindrance; and third, the two hydroxyl groups at the 1,3-positions are attached to the tertiary carbon atoms of the cyclobutane, resulting in high steric hindrance and low nucleophilic reactivity. These structural features present unique challenges when using this compound as a starting material for chemical transformation.

[0023] In related technologies, the classic synthetic routes for aromatic diamines mainly include two categories: one is to obtain the corresponding aromatic diamines through catalytic hydrogenation reduction or chemical reduction of aromatic nitro compounds; the other is to construct CN bonds through coupling reactions between aromatic halides and amino compounds. However, there are currently no reports on synthetic routes for aromatic diamines based on CBDO. The main difficulties in its synthesis are: (1) the hydroxyl group in the diol structure is attached to a highly substituted tertiary carbon, which has great steric hindrance and is difficult to directly react with haloaromatics to form CO bonds under traditional conditions; (2) the four-membered ring of cyclobutane is prone to ring-opening side reactions under strong acid, strong base or high temperature conditions, which puts forward strict requirements for the mildness of the reaction conditions; (3) the spatial crowding effect of the four methyl groups makes the separation and purification of reaction intermediates very difficult.

[0024] Furthermore, there are no literature reports on cyclobutane aromatic diamines with a 2,2,4,4-tetramethyl substitution mode in the relevant technologies.

[0025] In view of this, in one aspect of this application, a novel aromatic diamine monomer (named: 1,3-bis(aminophenoxy)-2,2,4,4-tetramethylcyclobutane) is proposed. According to embodiments of this application, the aromatic diamine monomer comprises at least one of the compounds shown in Formula I, Formula II, and Formula III: Formula I; Formula II; Formula III.

[0026] According to the embodiments of this application, the aromatic diamine monomer combines the rigid skeleton of "2,2,4,4-tetramethylcyclobutane" with the highly reactive structural unit of "aromatic diamine," creating a novel class of compounds. The aromatic diamine monomer of this application contains two reactive amino groups in its molecular structure, making it suitable for use as a diamine monomer in the preparation of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. Furthermore, the combination of alicyclic and aromatic ether structures in the aromatic diamine monomer of this application gives it promising application prospects in the field of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. In particular, because the aromatic diamine monomer of this application simultaneously possesses a rigid cyclobutane and four methyl side groups, when used to prepare polymers such as polyimides, it can impart comprehensive properties such as high transparency, high glass transition temperature, good solubility, and low dielectric constant to the materials. This provides a new monomer selection for the development of novel polyimides, polyamides, and other materials with tunable properties.

[0027] According to some specific embodiments of this application, the aromatic diamine monomer 1 The 1H NMR spectrum includes: a singlet with a chemical shift of 5.5 ppm, multiplets with chemical shifts of 6.61 ppm to 7.10 ppm, and a singlet with a chemical shift of 0.9 ppm.

[0028] In a second aspect of this application, a method for preparing the aromatic diamine monomer of the first aspect is provided. According to an embodiment of this application, the method includes: S100: mixing 2,2,4,4-tetramethyl-1,3-cyclobutanediol, fluoronitrobenzene, a basic catalyst, and a first organic solvent to carry out a nucleophilic substitution reaction to obtain 1,3-bis(nitrobenzoxy)-2,2,4,4-tetramethylcyclobutane; S200: mixing 1,3-bis(nitrobenzoxy)-2,2,4,4-tetramethylcyclobutane, palladium on carbon catalyst, hydrazine hydrate, and a second organic solvent to carry out a catalytic transfer hydrogenation reaction to obtain the aromatic diamine monomer.

[0029] The method described in this application uses industrial-scale alicyclic diol CBDO as the starting material and connects two aniline end groups through ether bonds to introduce an alicyclic structure into an aromatic diamine monomer, which is a novel structural type of aromatic diamine compounds.

[0030] The method for preparing aromatic diamine monomers according to the embodiments of this application, for the first time, uses 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) as a starting material and synthesizes an aromatic diamine monomer (i.e., 1,3-bis(aminophenoxy)-2,2,4,4-tetramethylcyclobutane) via a two-step process. This compound is a novel aromatic diamine monomer. The synthetic route of this application employs nucleophilic substitution and palladium on carbon / hydrazine hydrate catalytic transfer hydrogenation reduction, which is simple to operate, has mild reaction conditions, and does not require high-pressure hydrogen equipment, making it suitable for industrial-scale production. Furthermore, CBDO is already available on an industrial scale, and fluoronitrobenzene, palladium on carbon, and hydrazine hydrate are all stable industrial raw materials, making production costs controllable.

[0031] It should be noted that, using CBDO as the starting material, the two hydroxyl groups in its molecule are attached to highly substituted tertiary carbon atoms, resulting in significant steric hindrance and making direct nucleophilic substitution reactions extremely difficult. The method described in this application develops an efficient synthetic route that successfully converts these two "inert" tertiary alcohol hydroxyl groups into highly reactive aromatic diamines.

[0032] Meanwhile, the aromatic diamine monomers prepared by this method can be used as diamine monomers in the preparation of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. Furthermore, the combination of alicyclic and aromatic ether structures in the aromatic diamine monomers prepared by this method makes them promising for applications in the field of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. In particular, the aromatic diamine monomers prepared by this method, due to the simultaneous presence of rigid cyclobutane and four methyl side groups in their molecules, can impart comprehensive properties such as high transparency, high glass transition temperature, good solubility, and low dielectric constant to polymers such as polyimides when used in their preparation. This provides a new monomer selection for the development of novel polyimides and polyamides with tunable properties.

[0033] Specifically, the above method includes the following steps: S100: 2,2,4,4-Tetramethyl-1,3-cyclobutanediol, fluoronitrobenzene, basic catalyst and first organic solvent are mixed and subjected to nucleophilic substitution reaction to obtain 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane; In this step, using CBDO and fluoronitrobenzene as starting materials, aromatic nucleophilic substitution is carried out under alkaline conditions via a Williamson ether synthesis reaction, replacing the fluorine atom of fluoronitrobenzene with the oxonium of CBDO to obtain a dinitro compound intermediate (i.e., 1,3-bis(nitrobenzoxy)-2,2,4,4-tetramethylcyclobutane). Taking p-fluoronitrobenzene as an example, the reaction equation is as follows:

[0034] In the embodiments of this application, the specific types of fluoronitrobenzene are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred embodiments, the fluoronitrobenzene includes any one of p-fluoronitrobenzene, m-fluoronitrobenzene, and o-fluoronitrobenzene.

[0035] In the embodiments of this application, the specific type of alkaline catalyst is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred embodiments, the alkaline catalyst includes at least one of potassium carbonate, cesium carbonate, potassium hydroxide, and sodium hydride.

[0036] In the embodiments of this application, the specific type of the first organic solvent is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred embodiments, the first organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0037] According to some specific embodiments of this application, the molar ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol to fluoronitrobenzene is 1:(2~3), for example, it can be 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3 or any range between the two. By limiting the molar ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol to fluoronitrobenzene within the above range, it can be ensured that 2,2,4,4-tetramethyl-1,3-cyclobutanediol and fluoronitrobenzene react fully.

[0038] According to some specific embodiments of this application, the molar ratio of the above-mentioned alkaline catalyst to 2,2,4,4-tetramethyl-1,3-cyclobutanediol is (2~3):1, for example, it can be 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3 or any range between the two. By limiting the molar ratio of the above-mentioned alkaline catalyst to 2,2,4,4-tetramethyl-1,3-cyclobutanediol within the above range, it can be ensured that 2,2,4,4-tetramethyl-1,3-cyclobutanediol and fluoronitrobenzene can fully undergo aromatic nucleophilic substitution reaction under alkaline catalyst.

[0039] According to some specific embodiments of this application, the temperature of the above-mentioned nucleophilic substitution reaction is 80°C to 150°C (e.g., 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or any range between the two), and the time is 8 hours to 24 hours (e.g., 8 hours, 10 hours, 15 hours, 20 hours, 24 hours, or any range between the two). By limiting the temperature and time of the nucleophilic substitution reaction within the above range, it is further ensured that 2,2,4,4-tetramethyl-1,3-cyclobutanediol and fluoronitrobenzene undergo an aromatic nucleophilic substitution reaction under a basic catalyst.

[0040] S200: 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane, palladium on carbon catalyst, hydrazine hydrate, and a second organic solvent are mixed and subjected to catalytic transfer hydrogenation to obtain an aromatic diamine monomer.

[0041] In this step, the aforementioned dinitro compound intermediate (i.e., 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane) undergoes a catalytic transfer hydrogenation reduction reaction in the presence of a palladium-on-carbon catalyst and a hydrazine hydrate reducing agent. The hydrazine hydrate decomposes on the palladium-on-carbon surface to generate active hydrogen atoms, progressively reducing the nitro group to an amino group (reaction pathway: -NO2→-NO→-NHOH→-NH2), ultimately yielding the corresponding aromatic diamine monomer containing the tetramethylcyclobutane structure. The reaction equation is as follows:

[0042] According to some specific embodiments of this application, the mass of the palladium-on-carbon catalyst is 1% to 10% of the mass of 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane, for example, it can be 1%, 2%, 4%, 6%, 8%, 10%, or any range between the two. By limiting the amount of the palladium-on-carbon catalyst to the above range, it can be further ensured that the above-mentioned dinitro compound intermediate (i.e., 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane) can fully undergo catalytic transfer hydrogenation reduction reaction in the presence of the palladium-on-carbon catalyst and hydrazine hydrate reducing agent.

[0043] According to some specific embodiments of this application, the mass fraction of palladium in the palladium-on-carbon catalyst is 5% to 10%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10% or any range between the two. This can further ensure that the above-mentioned dinitro compound intermediate (i.e., 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane) can fully undergo catalytic transfer hydrogenation reduction reaction in the presence of palladium-on-carbon catalyst and hydrazine hydrate reducing agent.

[0044] According to some specific embodiments of this application, the molar ratio of the above-mentioned hydrazine hydrate to 1,3-bis(nitrobenoxy)-2,2,4,4-tetramethylcyclobutane is (3~10):1, for example, it can be 3:1, 4:1, 5:1, 6:1, 8:1, 10:1 or any range between the two. By limiting the amount of the above-mentioned hydrazine hydrate to the above range, it can be further ensured that the above-mentioned dinitro compound intermediate (i.e. 1,3-bis(nitrobenoxy)-2,2,4,4-tetramethylcyclobutane) can fully undergo catalytic transfer hydrogenation reduction reaction in the presence of palladium on carbon catalyst and hydrazine hydrate reducing agent.

[0045] According to some specific embodiments of this application, the mass concentration of the above-mentioned hydrazine hydrate is 80% to 100%, for example, it can be 80%, 85%, 90%, 95%, 100% or any range between the two, thereby further ensuring that the above-mentioned dinitro compound intermediate (i.e., 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane) fully undergoes catalytic transfer hydrogenation reduction reaction in the presence of palladium on carbon catalyst and hydrazine hydrate reducing agent.

[0046] In the embodiments of this application, the specific type of the second organic solvent is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred embodiments, the second organic solvent includes at least one of methanol, ethanol, tetrahydrofuran, ethyl acetate and water.

[0047] According to some specific embodiments of this application, the temperature of the above-mentioned catalytic transfer hydrogenation reaction is 70°C to 100°C (e.g., it can be 70°C, 80°C, 90°C, 100°C, or any range between the two), and the reaction time is 4 hours to 12 hours (e.g., it can be 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, or any range between the two). By limiting the temperature and time of the catalytic transfer hydrogenation reaction within the above range, it can be further ensured that the above-mentioned dinitro compound intermediate (i.e., 1,3-bis(nitrobenzoxy)-2,2,4,4-tetramethylcyclobutane) undergoes sufficient catalytic transfer hydrogenation reduction reaction in the presence of palladium on carbon catalyst and hydrazine hydrate reducing agent.

[0048] In a third aspect of this application, the application of an aromatic diamine monomer prepared by the method of the first aspect or the method of the second aspect in the preparation of polyimide, polyamide, and polyurethane is proposed.

[0049] The aromatic diamine monomer of this application contains two reactive amino groups in its molecular structure, making it suitable for use as a diamine monomer in the preparation of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. Furthermore, the combination of alicyclic and aromatic ether structures in the aromatic diamine monomer of this application gives it promising application prospects in the field of high-performance polymer materials such as polyimides, polyamides, and polyurethanes. In particular, because the aromatic diamine monomer of this application simultaneously contains rigid cyclobutane and four methyl side groups, when used to prepare polymers such as polyimides, it can impart comprehensive properties such as high transparency, high glass transition temperature, good solubility, and low dielectric constant to the materials. This provides a new monomer option for the development of novel polyimides and polyamides with tunable properties.

[0050] According to some specific embodiments of this application, an aromatic diamine monomer and a dianhydride monomer are subjected to a polycondensation reaction to obtain a polyimide material. As some specific embodiments, the temperature of the above polycondensation reaction is -10℃ to 60℃ (e.g., it can be -10℃, 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, or any range between the two), and the time is 4 hours to 24 hours (e.g., it can be 4 hours, 8 hours, 10 hours, 15 hours, 20 hours, 24 hours, or any range between the two).

[0051] According to some specific embodiments of this application, the glass transition temperature of the polyimide material is 320℃~400℃, the transmittance of the polyimide material at 450nm is ≥85%, and the dielectric constant of the polyimide material at 1MHz is 3.0~3.5.

[0052] The aromatic diamine monomer described in this application serves as a key raw material for the preparation of polyimides. Through the polycondensation reaction with dianhydride monomers, a series of high-performance polyimide materials can be obtained. This preparation process is highly controllable and the reaction conditions are mild. The resulting polyimide materials have significant advantages in terms of thermal properties, mechanical properties, and dielectric properties, and can meet the application requirements of high-end fields such as aerospace, electronics, and automotive industries.

[0053] Polyimide is a class of high-performance polymer materials containing an imide ring (-CO-NR-CO-) in its main chain. Its excellent comprehensive properties mainly stem from the rigid structure of the imide ring and the conjugation effect and intermolecular forces imparted by the aromatic monomer. Using the aromatic diamine monomer described in this application as a raw material, polyimide is prepared by polycondensation reaction with a dianhydride monomer. This process mainly consists of two core stages: first, the aromatic diamine monomer and the dianhydride monomer undergo a nucleophilic addition reaction to generate a polyamic acid (PAA) prepolymer; subsequently, the polyamic acid prepolymer undergoes a ring-closure reaction under heating or chemical dehydrating agents, removing water molecules and forming an imide ring, ultimately yielding the polyimide (PI) material.

[0054] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0055] Example 1 This embodiment provides a method for preparing an aromatic diamine monomer (the compound shown in Formula I), comprising the following steps: (1) Synthesis of 1,3-bis(4-nitrophenoxy)-2,2,4,4-tetramethylcyclobutane (dinitro intermediate): Under nitrogen protection, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (20.0 g, 0.116 mol) and anhydrous potassium carbonate (48.1 g, 0.348 mol) were added to a 250 mL three-necked flask, followed by the addition of N,N-dimethylacetamide (DMAc, 100 mL). The mixture was stirred at 80 °C for 1 hour to allow the hydroxyl groups to fully convert to oxygen anions. Subsequently, p-fluoronitrobenzene (34.4 g, 0.244 mol) was slowly added dropwise, and the temperature was raised to 130 °C, continuing the reaction for 16 hours. The reaction progress was monitored by thin-layer chromatography until the CBDO starting material spot disappeared.

[0056] After the reaction was completed, the mixture was cooled to room temperature and slowly poured into 500 mL of ice water, precipitating a pale yellow solid. The solid product was collected by filtration and washed successively with deionized water (3 times, 100 mL each time) and organic solvent (2 times, 50 mL each time). The product was then dried under vacuum at 60 °C for 12 hours to obtain a pale yellow solid with a yield of approximately 88%. 1 1H NMR and FT-IR analyses confirmed it to be an intermediate of the target dinitro compound.

[0057] (2) Synthesis of 1,3-bis(4-aminophenoxy)-2,2,4,4-tetramethylcyclobutane (target aromatic diamine monomer, compound shown in Formula I): The dinitro compound intermediate (10.0 g) obtained in step (1) was dissolved in 100 mL of anhydrous ethanol, and 0.6 g of palladium on carbon catalyst (palladium mass fraction of 5%) was added. The mixture was heated to 80 °C. 8.5 g of hydrazine hydrate (hydrazine mass concentration of 80%) was slowly added dropwise under vigorous stirring. During the addition, the reaction system was refluxed violently and a large amount of gas was generated. After the addition was complete, the reaction was refluxed for another 6 hours. Thin-layer chromatography was used to monitor the disappearance of the dinitro compound starting material spot.

[0058] After the reaction was complete, the palladium catalyst on carbon was removed by hot filtration, and the filter cake was washed with a small amount of hot ethanol. The filtrates were combined, concentrated under reduced pressure to about 1 / 3 of their volume, and then cooled to room temperature. Deionized water was slowly added with stirring, and a white solid precipitated. The solid was collected by suction filtration, washed with a mixed solvent of deionized water and ethanol, and dried under vacuum at 60°C to obtain a white solid with a yield of about 85%.

[0059] (3) Analysis and characterization of the product: The white solid obtained in step (2) was characterized as follows: 1) 1 1H NMR (400 MHz, DMSO-d6) spectrum (as attached) Figure 1 Analysis (as shown) revealed the following values: δ 5.50 (s, 4H, -NH2), δ 6.61–7.10 (m, 8H, aromatic ring H), δ 0.9 (s, 12H, -CH3). The characteristic amino peak was located at approximately 5.5 ppm, the aromatic ring proton peak was located in the 6.6–7.1 ppm region, and the methyl singlet was located at approximately 0.9 ppm.

[0060] 2) Fourier transform infrared spectrum (as attached) Figure 2 Analysis (as shown) indicates that the stretching vibration peak of NH2 is located at approximately 3400 cm⁻¹. -1 The C=C skeletal vibrational peak of the aromatic ring is located at approximately 1600 cm⁻¹. -1 and 1500 cm -1 The peak of the asymmetric stretching vibration of the ether bond COC is located at approximately 1240 cm⁻¹. -1 .

[0061] 3) The results of high-resolution mass spectrometry showed that the molecular ion peak was consistent with the theoretical calculation value.

[0062] 4) High performance liquid chromatography analysis showed that the product purity was ≥98%.

[0063] above 1 ¹H NMR spectrum, infrared spectrum, high-resolution mass spectrometry results, and high-performance liquid chromatography all show that 1,3-bis(4-aminophenoxy)-2,2,4,4-tetramethylcyclobutane (the target aromatic diamine monomer, compound shown in Formula I) was successfully synthesized with high purity.

[0064] Example 2 Example 2 provides a method for preparing an aromatic diamine monomer (the compound shown in Formula II), which is basically the same as the method in Example 1, except that: Replace p-fluoronitrobenzene in step (1) with m-fluoronitrobenzene.

[0065] Calculations show that the yield of the aromatic diamine monomer (the compound shown in Formula II) obtained in this example is approximately 84%, and the purity of the product is ≥98%.

[0066] Example 3 Example 3 provides a method for preparing an aromatic diamine monomer (the compound shown in Formula III), which is basically the same as the method in Example 1, except that: Replace p-fluoronitrobenzene in step (1) with o-fluoronitrobenzene.

[0067] Calculations show that the yield of the aromatic diamine monomer (the compound shown in Formula III) obtained in this example is approximately 86%, and the purity of the product is ≥98%.

[0068] Example 4 Example 4 provides a method for preparing an aromatic diamine monomer (the compound shown in Formula I), which is basically the same as the method in Example 1, except that: (1) Under nitrogen protection, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (20.0 g, 0.116 mol) and anhydrous potassium carbonate (0.232 mol, 32.06 g) were added to a 250 mL three-necked flask, followed by the addition of N,N-dimethylacetamide (DMAc, 100 mL). The mixture was stirred at 80 °C for 1 hour to allow the hydroxyl groups to be fully converted to oxygen anions. Subsequently, p-fluoronitrobenzene (0.348 mol, 49.11 g) was slowly added dropwise, and the temperature was raised to 100 °C to continue the reaction for 24 hours. The reaction progress was monitored by thin-layer chromatography until the TMCD starting material spot disappeared.

[0069] Calculations show that the yield of the aromatic diamine monomer (the compound shown in Formula I) obtained in this example is approximately 89%, and the purity of the product is ≥98%.

[0070] Example 5 Example 5 provides a method for preparing an aromatic diamine monomer (the compound shown in Formula I), which is basically the same as the method in Example 1, except that: (2) Dissolve 10.0 g of the dinitro compound intermediate obtained in step (1) in 100 mL of anhydrous ethanol, add 0.9 g of palladium on carbon catalyst (palladium mass fraction in palladium on carbon catalyst is 5%), and heat to 100 °C. Slowly add 19 g of hydrazine hydrate (hydrazine hydrate mass concentration is 80%) dropwise under vigorous stirring. During the dropwise addition, the reaction system is refluxed vigorously and a large amount of gas is generated. After the dropwise addition is completed, continue the reflux reaction for 4 hours. Thin-layer chromatography monitors until the dinitro compound starting material spot disappears.

[0071] Calculations show that the yield of the aromatic diamine monomer (the compound shown in Formula I) obtained in this example is approximately 88%, and the purity of the product is ≥98%.

[0072] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0073] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An aromatic diamine monomer, characterized in that, Including at least one of the compounds shown in Formula I, Formula II, and Formula III: Formula I; Formula II; Formula III.

2. The aromatic diamine monomer according to claim 1, characterized in that, The aromatic diamine monomer 1 The 1H NMR spectrum includes: a singlet with a chemical shift of 5.5 ppm, multiplets with chemical shifts of 6.61 ppm to 7.10 ppm, and a singlet with a chemical shift of 0.9 ppm.

3. A method for preparing the aromatic diamine monomer according to claim 1 or 2, characterized in that, Includes the following steps: 2,2,4,4-Tetramethyl-1,3-cyclobutanediol, fluoronitrobenzene, a basic catalyst, and a first organic solvent were mixed and subjected to a nucleophilic substitution reaction to give 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane. The 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane, palladium on carbon catalyst, hydrazine hydrate, and a second organic solvent are mixed and subjected to a catalytic transfer hydrogenation reaction to obtain the aromatic diamine monomer.

4. The method according to claim 3, characterized in that, In the nucleophilic substitution reaction, the fluoronitrobenzene includes any one of p-fluoronitrobenzene, m-fluoronitrobenzene, and o-fluoronitrobenzene; And / or, the alkaline catalyst includes at least one of potassium carbonate, cesium carbonate, potassium hydroxide, and sodium hydride; And / or, the first organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

5. The method according to claim 3, characterized in that, In the nucleophilic substitution reaction, the molar ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol to fluoronitrobenzene is 1:(2~3); And / or, the molar ratio of the alkaline catalyst to the 2,2,4,4-tetramethyl-1,3-cyclobutanediol is (2~3):

1.

6. The method according to claim 3, characterized in that, In the nucleophilic substitution reaction, the temperature is 80℃~150℃ and the time is 8 hours~24 hours.

7. The method according to any one of claims 3 to 6, characterized in that, In the catalytic transfer hydrogenation reaction, the mass of the palladium catalyst on carbon is 1% to 10% of the mass of 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane; And / or, the palladium mass fraction in the palladium-on-carbon catalyst is 5% to 10%; And / or, the molar ratio of the hydrazine hydrate to the 1,3-bis(nitrophenoxy)-2,2,4,4-tetramethylcyclobutane is (3~10):1; And / or, the mass concentration of the hydrazine hydrate is 80%~100%; And / or, the second organic solvent includes at least one of methanol, ethanol, tetrahydrofuran, ethyl acetate, and water.

8. The method according to any one of claims 3 to 6, characterized in that, In the catalytic transfer hydrogenation reaction, the temperature is 70℃~100℃ and the reaction time is 4 hours~12 hours.

9. The use of the aromatic diamine monomer as described in claim 1 or 2, or the aromatic diamine monomer prepared by any one of claims 3 to 8, in the preparation of polyimide, polyamide, and polyurethane.

10. The application according to claim 9, characterized in that, The aromatic diamine monomer and the dianhydride monomer are subjected to a polycondensation reaction to obtain a polyimide material. The polycondensation reaction is carried out at a temperature of -10℃ to 60℃ for a time of 4 hours to 24 hours. The glass transition temperature of the polyimide material is 320℃ to 400℃, the transmittance of the polyimide material at 450nm is ≥85%, and the dielectric constant of the polyimide material at 1MHz is 3.0 to 3.5.

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