Diamine monomers containing both carboxyl and imide rings and methods for their preparation

Abstract

This invention relates to the field of organic synthesis and discloses a diamine monomer containing both a carboxyl group and an imide ring, as well as a method for its preparation. This diamine monomer simultaneously contains both a carboxyl group and an imide ring. This diamine monomer enriches the variety of carboxyl-functionalized diamine monomers currently available, and the presence of the imide ring enhances the functionality of the diamine monomer, broadening its application scenarios in different polymers and providing polymers with physical and chemical properties not possessed by existing carboxyl-functionalized diamine monomers.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and more specifically, to a diamine monomer containing both a carboxyl group and an imide ring, and a method for preparing the same. Background Technology

[0002] Polyimide, as a special engineering material, possesses excellent mechanical properties, thermal stability, and good chemical stability, and has found important applications in insulating materials, aerospace, flexible displays, and gas separation membrane materials. Diamine monomers are the basic raw materials for preparing polyimide. Based on monomer and molecular structure design, novel monomer and polyimide structures can be developed for different applications. Therefore, developing novel diamine monomers, especially those with functional groups, represents a significant breakthrough in improving the performance of polyimide materials.

[0003] Polyimide is one of the most widely used gas separation membrane materials, but it suffers from significant aging problems and plasticization challenges in the face of acidic gases. Therefore, researchers have developed carboxyl functionalization techniques to design functionalized polyimide materials, addressing these challenges through hydrogen bonding and crosslinking. The paper "Cross-linkable polyimidemembranes for improved plasticization, resistance, and permselectivity in sourgas separations" (Macromolecules 2013, 46, 6908-6921) discloses the reaction of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) with 3,5-diaminobenzoic acid (DABA) and their copolymers to obtain carboxyl functionalized polyimides. Because these polyimides can be easily crosslinked through various methods, they show great promise for natural gas separation.

[0004] The paper "Fuel cells with an operational range of -20°C to 200°C enabled by phosphoric acid-doped intrinsically ultramicroporous membranes" [J]. Nature Energy, 2022, 7(2): 153-162 discloses that diamine monomers with rigid structures can also be used to prepare self-microporous polymers with microporous properties through Choger base polymerization. These polymers have ultra-large specific surface areas and have been widely used in gas separation membranes and proton exchange membranes. Therefore, designing and developing diamine monomers with rigid structures can expand the types of self-microporous polymers and provide more choices for different applications.

[0005] Currently, there are relatively few methods and types for preparing carboxylated diamines. Industrial & Engineering Chemistry Research, 2019, 59(12):5247-5256 reported a two-step method to first prepare 2,4,6-trimethyl-3,5-dinitrobenzoic acid from 2,4,6-trimethylbenzoic acid, and then prepare 3,5-diamino-2,4,5-trimethylbenzoic acid. The synthetic route is relatively long and uses a lot of solvents and catalysts, which is not conducive to the recovery and utilization of reaction substrates, catalysts and solvents in scale-up production, resulting in high production costs.

[0006] CN118125972A discloses a diamine monomer with a nitrogen-containing heterocyclic and benzo[a]cyclobutene structure, its preparation method, and its applications, belonging to the field of functional polymer materials. The diamine monomer with the nitrogen-containing heterocyclic and benzo[a]cyclobutene structure is combined with other diamine monomers and introduced into a resin precursor to prepare a photosensitive resin composition. This diamine monomer contains a nitrogen-containing heterocyclic structure, which can promote the dehydration and cyclization reaction of the resin precursor, thereby lowering the curing temperature and solving the problem of insufficient imidization of the resin during low-temperature curing. Simultaneously, the benzo[a]cyclobutene structure can undergo ring-opening crosslinking at a low temperature of 250℃. However, the starting reactants used are expensive, and the reaction route is long, thus posing significant challenges for the development of subsequent novel diamine monomers.

[0007] CN118684593A discloses a novel diamine monomer, which is synthesized by modifying the structure of a traditional diamine monomer. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of limited types of carboxyl-functionalized diamine monomers, complex process routes, and high costs in the prior art, and to provide a diamine monomer containing both carboxyl and imide rings and a preparation method thereof. The diamine monomer contains both carboxyl and imide rings, and the preparation method of the diamine monomer is simple, easy to recover unreacted monomers and solvents, and can reduce costs while improving yield.

[0009] To achieve the above objectives, the first aspect of the present invention provides a diamine monomer, wherein the diamine monomer contains both a carboxyl group and an imide ring.

[0010] A second aspect of the present invention provides a method for preparing a diamine monomer, wherein the preparation method includes:

[0011] (1) In the presence of a protective atmosphere, monomer A, monomer B and solvent are first mixed and then a first reaction is carried out;

[0012] (2) After mixing the product of the first reaction with the dehydrating agent, a second reaction is carried out;

[0013] (3) The product of the second reaction was subjected to vacuum distillation and cooling in sequence to obtain the diamine monomer;

[0014] Wherein, monomer A is an aromatic diamine compound, and monomer B is selected from aromatic dianhydride compounds and / or alicyclic dianhydride compounds.

[0015] A third aspect of the present invention provides a diamine monomer prepared by the above-described preparation method.

[0016] Through the above technical solutions, the diamine monomer and its preparation method provided by the present invention achieve the following beneficial effects:

[0017] The diamine monomer provided by this invention contains both a carboxyl group and an imide ring, which enriches the variety of carboxyl-functionalized diamine monomers currently available. Furthermore, the presence of the imide ring enhances the functionality of the diamine monomer, broadens its application scenarios in different polymers, and provides polymers with physical and chemical properties that are not present in the original carboxyl-functionalized diamine monomers.

[0018] Furthermore, the diamine monomers provided by this invention offer a wide variety of imide ring structures, which are highly designable and can be customized to prepare carboxyl-containing diamine monomers according to different functions and synthesis requirements, thus exhibiting strong versatility.

[0019] The method for preparing diamine monomers provided by this invention employs a one-step preparation process, which simplifies the preparation process, improves the synthesis efficiency, and makes it easy to recycle unreacted monomers and solvents, thus significantly reducing production costs. Attached Figure Description

[0020] Figure 1 This is the FTIR spectrum of the carboxyl- and imide-containing cyclic diamine monomer prepared in Example 1 of this invention;

[0021] Figure 2 This is the 1H NMR spectrum of the carboxyl- and imide-cyclic diamine monomer prepared in Example 1 of this invention. 1 H-NMR);

[0022] Figure 3 This is the FTIR spectrum of the carboxyl- and imide-containing cyclic diamine monomer prepared in Example 4 of this invention;

[0023] Figure 4 This is the 1H NMR spectrum of the carboxyl- and imide-cyclic diamine monomer prepared in Example 4 of this invention. 1 H-NMR);

[0024] Figure 5This is a schematic diagram of the preparation method of the diamine monomer of the present invention. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] The first aspect of the present invention provides a diamine monomer, wherein the diamine monomer contains both a carboxyl group and an imide ring.

[0027] In this invention, the diamine monomer contains both a carboxyl group and an imide ring, which enriches the variety of carboxyl-functionalized diamine monomers currently available. Furthermore, the presence of the imide ring enhances the functionality of the diamine monomer, broadens its application scenarios in different polymers, and provides polymers with physical and chemical properties that are not present in the original carboxyl-functionalized diamine monomers.

[0028] The diamine monomer provided by this invention simultaneously possesses an imide ring structure and a carboxyl group, which facilitates the widespread application of this novel monomer in various modified polymers and provides a wealth of functional groups. The imide ring exhibits high chemical and thermal stability, imparting excellent physical and chemical properties to the polymer. The combination of the imide ring structure and the carboxyl group structure promotes hydrogen bonding between polymer chains, enhancing interchain interactions, effectively strengthening the polymer's mechanical properties, and providing physical crosslinking sites. Furthermore, the introduction of carboxyl groups into the polymer chain increases the modification methods, including chemical crosslinking and thermal crosslinking, significantly improving the polymer's resistance to aging, plasticization, and degradation.

[0029] According to the present invention, the diamine monomer has the structure shown in Formula I;

[0030]

[0031] In this compound, ring A is derived from an aromatic diamine compound, and ring B is derived from an aromatic dianhydride compound and / or an alicyclic dianhydride compound.

[0032] In this invention, when the diamine monomer has the structure shown in Formula I, the diamine monomer simultaneously possesses the characteristics of functional carboxyl groups and imide rings, which broadens the application scenarios of the diamine monomer in different polymers and can provide different modification methods for polymers.

[0033] In one specific embodiment of the present invention, ring A contains a substituent, wherein the substituent is selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0034] In one specific embodiment of the present invention, ring B contains a substituent, wherein the substituent is selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0035] In this invention, there is no particular limitation on the position of the substituent on ring A or ring B; ring A or ring B can be any position that can be substituted.

[0036] In this invention, the halogen includes, but is not limited to, fluorine, bromine, chlorine, or iodine.

[0037] In this invention, "halogenated" means that at least one H in the group is replaced by a halogen (e.g., F, Br, Cl or I).

[0038] In this invention, the unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups include unsubstituted or halogenated C1, C2, C3, C4, C5, C6, C7, C8, C9 ... 10 Straight-chain or branched alkyl groups, including but not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, trifluoromethyl, trichloromethyl, perfluoroethyl, perchloroethyl, etc.

[0039] In a preferred embodiment of the present invention, the substituent of ring A is selected from halogens, OH, COOH, H, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0040] In a preferred embodiment of the present invention, the substituent of ring B is selected from halogens, OH, COOH, H, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0041] In one specific embodiment of the present invention, A is selected from at least one of the following groups:

[0042]

[0043] In this context, the dashed lines represent the insertion positions of the groups, R1-R 11 Each is independently selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0044] In one specific embodiment of the present invention, B is selected from at least one of the following groups:

[0045]

[0046]

[0047] In this context, the dashed line indicates the insertion position of the functional group; R 12 -R 52 Each is independently selected from H, halogen, OH, COOH, SO3H, NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0048] A second aspect of the present invention provides a method for preparing a diamine monomer, wherein the preparation method includes:

[0049] (1) In the presence of a protective atmosphere, monomer A, monomer B and solvent are first mixed and then a first reaction is carried out;

[0050] (2) After mixing the product of the first reaction with the dehydrating agent, a second reaction is carried out;

[0051] (3) The product of the second reaction was subjected to vacuum distillation and cooling in sequence to obtain the diamine monomer;

[0052] Wherein, monomer A is a carboxyl-containing aromatic diamine compound, and monomer B is selected from aromatic diamine 1240827.

[0053] I96966BHY

[0054] Anhydride compounds and / or alicyclic dianhydride compounds.

[0055] In this invention, an aromatic diamine compound containing a carboxyl group is used as monomer A, and monomer B, selected from aromatic dianhydrides and / or alicyclic dianhydrides, is used as the starting reactant. A one-step method is employed to synthesize a diamine monomer containing both a carboxyl group and an imide ring. Novel diamine monomers containing both a carboxyl group and an imide ring are obtained through vacuum distillation and other methods. This preparation method is simple, has a short reaction time, and is cost-effective.

[0056] In this invention, there is no particular limitation on the type of protective atmosphere; for example, it can be nitrogen.

[0057] In one specific embodiment of the present invention, monomer A contains a substituent selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0058] In a preferred embodiment of the present invention, monomer A is selected from at least one of the following compounds:

[0059]

[0060] Among them, R 53 -R 63 Each is independently selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0061] In one specific embodiment of the present invention, monomer B contains a substituent selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0062] In a preferred embodiment of the present invention, monomer B is selected from at least one of the following compounds:

[0063]

[0064]

[0065] Among them, R 64 -R 104 Each is independently selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

[0066] According to the present invention, the boiling point of the solvent is 140-300°C.

[0067] In this invention, monomer A and monomer B are mixed with the aforementioned high-boiling-point solvent before the reaction is carried out. The aforementioned high-boiling-point solvent has the characteristics of low toxicity, low volatility, and good chemical stability, which not only enables monomer A and monomer B to be mixed evenly, but also avoids the instability of the reaction caused by the volatilization of solvents during the reaction process.

[0068] In this invention, the boiling point of the solvent refers to the boiling point of the solvent under normal temperature and pressure conditions.

[0069] Furthermore, the solvent has a boiling point of 150-260°C.

[0070] In this invention, there is no particular limitation on the type of solvent, as long as the boiling point of the solvent meets the requirements of this invention. For example, the solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol and dimethyl sulfoxide.

[0071] In one specific embodiment of the present invention, the monomer A, the monomer B and the solvent are mixed such that the solid content of the product after the first mixture is 5-35 wt%.

[0072] In this invention, when the solid content of the product after the first mixture is controlled to meet the above range, monomer A and monomer B are mixed evenly in the product after the first mixture, and the amount of dehydrating agent required for the second reaction is low, which reduces costs and energy consumption while avoiding the formation of macromolecular compounds.

[0073] Furthermore, the monomer A, the monomer B, and the solvent are mixed such that the solid content of the first mixed product is 10-25 wt%.

[0074] In one specific embodiment of the present invention, the molar ratio of monomer A to monomer B is 2-4:1.

[0075] In this invention, when the molar ratio of monomer A and monomer B is controlled to meet the above-mentioned range, the amount of monomer A and monomer B can be reduced while ensuring the purity of the final product, thereby simplifying the post-processing process and reducing production costs.

[0076] Furthermore, the molar ratio of monomer A to monomer B is 2.3-3.5:1.

[0077] In one specific embodiment of the present invention, the conditions for the first reaction include: a reaction temperature of -5°C to 120°C and a reaction time of 9-36 hours.

[0078] In this invention, the first reaction is carried out under the aforementioned relatively mild conditions, which not only ensures a full reaction between monomer A and monomer B, but also simplifies the process and reduces the energy consumption required for the reaction.

[0079] Furthermore, the conditions for the first reaction include: a reaction temperature of 15-100℃ and a reaction time of 12-30h.

[0080] In one specific embodiment of the present invention, the dehydrating agent is selected from at least one of toluene, xylene, and chlorobenzene.

[0081] In one specific embodiment of the present invention, the amount of the dehydrating agent is 20-60 vol% of the amount of the solvent.

[0082] In this invention, when the amount of dehydrating agent is controlled to meet the above range, the dehydrating agent and the solvent can form an azeotropic system better. When the amount of dehydrating agent is low, it can ensure that the product of the first reaction is dehydrated more fully and improve the degree of imidization.

[0083] Furthermore, the amount of the dehydrating agent used is 24-45 vol% of the amount of the solvent used.

[0084] In one specific embodiment of the present invention, the conditions for the second reaction include: reflux at 140-210°C for 6-36 hours.

[0085] In this invention, carrying out the second reaction under the above conditions enables the product of the first reaction to react fully with the dehydrating agent, thereby increasing the degree of imidization and further improving the purity of the final diamine monomer.

[0086] Furthermore, the conditions for the second reaction include reflux at 160-190°C for 7-24 hours.

[0087] In this invention, in the presence of a dehydrating agent and under second reaction conditions, the product of the first reaction undergoes thermal imidization dehydration to obtain a homogeneous reaction solution containing a diamine monomer containing both a carboxyl group and an imide ring, as well as unreacted monomer A.

[0088] In this invention, the homogeneous reaction solution containing the product of the second reaction (i.e., the diamine monomer containing both carboxyl and imide rings and unreacted monomer A) is subjected to vacuum distillation, which enables the recovery and reuse of the reaction solvent and unreacted diamine monomer A from step (1). By recovering the reaction solvent and diamine monomer A through vacuum distillation, separation via chromatography is eliminated, shortening the reaction process. Simultaneously, the reaction monomers and solvent are effectively recovered, increasing product yield and reducing production costs.

[0089] In one specific embodiment of the present invention, the vacuum distillation is a two-stage vacuum distillation.

[0090] In this invention, the dehydrating agent and solvent can be recovered and separated separately through two-stage vacuum distillation.

[0091] In one specific embodiment of the present invention, the vacuum distillation includes the following steps:

[0092] After distilling at 90-140℃ for 0.1-6 hours, distill at 150-210℃ for 0.1-10 hours.

[0093] In this invention, under low temperature conditions, the dehydrating agent is preferentially distilled out of the system, while under high temperature conditions, the reaction solvent is distilled out of the system.

[0094] In a preferred embodiment of the present invention, the vacuum distillation includes the following steps:

[0095] After distilling at 100-130℃ for 0.3-4 hours, distill at 155-180℃ for 0.5-8 hours.

[0096] In one specific embodiment of the present invention, the product after vacuum distillation is cooled, and the cooling is controlled to be carried out under vacuum conditions. By controlling the cooling to be carried out under vacuum conditions, side reactions such as oxidation of unreacted raw material monomers (monomer A and monomer B) and the final product diamine monomer can be avoided, thereby ensuring that the final product has high purity.

[0097] In this invention, there is no particular limitation on the vacuum level of the vacuum condition; for example, it can be 0.08-0.1 MPa.

[0098] In one specific embodiment of the present invention, the product after vacuum distillation is cooled to below 30°C under vacuum conditions to obtain a solid mixture containing a diamine monomer containing both a carboxyl group and an imide ring, as well as unreacted monomer A.

[0099] In one specific embodiment of the present invention, the method further includes:

[0100] (4) The cooled product is mixed with solvent I for the third time, and then separated into solid and liquid phases to obtain the solid phase;

[0101] (5) The solid phase, solvent II and adsorbent are mixed for the fourth time, and after the second solid-liquid separation, the liquid phase is dried to obtain the diamine monomer.

[0102] In this invention, by further processing the cooled product using the above steps, the purity and yield of the final product diamine monomer can be further improved, and the unreacted diamine monomer A can be effectively separated, thereby increasing the utilization rate of diamine monomer A and reducing the production cost.

[0103] In this invention, during the third mixing process, the unreacted diamine monomer A in the cooled product dissolves in solvent I. Through the first solid-liquid separation, a liquid phase containing the unreacted diamine monomer A and a solid phase containing both carboxyl and imide rings of the diamine monomer are obtained.

[0104] In this invention, the method of first solid-liquid separation is not particularly limited and can be a conventional solid-liquid separation method in the art, such as filtration.

[0105] In one specific embodiment of the present invention, solvent I is selected from at least one of ethanol, methanol and acetone.

[0106] In a preferred embodiment of the present invention, the liquid phase obtained from the first solid-liquid separation is mixed with water, and the unreacted diamine monomer A in the liquid phase is precipitated in the water.

[0107] In this invention, the solid phase obtained by the first solid-liquid separation (i.e., the diamine monomer containing both carboxyl and imide rings) is redissolved in solvent II. Under the action of the adsorbent, a small amount of unreacted monomer A and impurities remaining in the diamine monomer containing both carboxyl and imide rings are adsorbed by the adsorbent. After the second solid-liquid separation, as the solid phase adsorbent is removed from the diamine monomer, the purity of the obtained diamine monomer is further improved.

[0108] In this invention, there is no particular limitation on the type of solvent II, as long as it can fully dissolve the solid phase obtained from the first solid-liquid separation. For example, the solvent II is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, chloroform and dichloromethane.

[0109] In one specific embodiment of the present invention, the fourth mixing time is 2-36 hours.

[0110] In this invention, when the fourth mixing time is controlled to meet the above range, it can ensure that the adsorbent and the solid phase have sufficient contact time, thereby ensuring that the small amount of residual reactant monomer A and some impurities in the solid phase containing the diamine monomer containing carboxyl and imide rings are fully adsorbed by the adsorbent, ultimately improving the purity of the diamine monomer.

[0111] Furthermore, the fourth mixing time is 5-12 hours.

[0112] In one specific embodiment of the present invention, the adsorbent is selected from at least one of activated carbon powder, activated carbon particles, starch, and macroporous adsorption resin.

[0113] In this invention, there is no particular limitation on the specific amount of adsorbent used, as long as the small amount of residual reactant A and some impurities in the diamine monomer containing carboxyl and imide rings are fully adsorbed by the adsorbent.

[0114] In this invention, the source of the adsorbent, such as activated carbon powder, is not particularly limited and can be commercially available.

[0115] In this invention, after the second solid-liquid separation process, the solid phase is an adsorbent containing a small amount of residual reactive monomer A and some impurities, and the liquid phase is a solution containing diamine monomer. Further, the liquid phase obtained from the second solid-liquid separation is precipitated in a mixed solution of water and solvent I to obtain the target product, diamine monomer.

[0116] In this invention, there is no particular limitation on the amount of water and solvent I used. For example, the volume ratio of water to solvent I is 0.1-9:1.

[0117] In one specific embodiment of the present invention, the drying conditions include: a drying temperature of 50-120°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C, or any two of these values; and a drying time of 2-72 hours, for example, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 72 hours, or any two of these values.

[0118] According to a preferred embodiment of the present invention, such as Figure 4 As shown, the preparation method of the diamine monomer includes:

[0119] In a three-necked flask equipped with an N2 vent tube, a thermometer, and a mechanical stirrer, under an N2 atmosphere, first add diamine monomer A (a carboxyl aromatic diamine compound), then add a solvent with a boiling point of 140-300℃, such as N-methylpyrrolidone (NMP), etc. After diamine monomer A is completely dissolved, add dianhydride monomer B (an aromatic dianhydride compound and / or an alicyclic dianhydride compound), and react at -5℃ to 120℃ for 9-36 hours;

[0120] Then add a dehydrating agent such as toluene or xylene or a mixture thereof, control the reaction temperature at 140-210℃, and continue the reaction for 6-36 hours to finally obtain a homogeneous solution containing a diamine monomer containing both a carboxyl group and an imide ring and the remaining unreacted diamine monomer A.

[0121] The homogeneous solution was subjected to vacuum distillation. The dehydrating agent was gradually distilled off at 90-140℃ for 0.1-6h, and the high-boiling solvent was distilled off at 150-210℃ for 0.1-10h. The solution was then cooled to below 30℃ under vacuum to obtain a solid mixture containing a diamine monomer that simultaneously contains a carboxyl group and an imide ring, and the remaining unreacted diamine monomer A.

[0122] The resulting mixed solid was added to solvent I, which could dissolve the unreacted diamine monomer A while washing the product. Then, by filtration, a filtrate containing diamine monomer A and a diamine solid product containing carboxyl and imide rings were obtained. The filtrate was then precipitated in water to obtain solid monomer A.

[0123] The obtained diamine solid product containing carboxyl and imide rings was redissolved in solvent II, and activated carbon powder was added for adsorption for 2-36 hours. Then the activated carbon powder was filtered out, and the solid product was precipitated in a mixed solution of solvent I and water. The product was then filtered and dried.

[0124] A third aspect of the present invention provides a diamine monomer prepared by the above-described preparation method.

[0125] The present invention will be described in detail below through embodiments.

[0126] In the following examples and comparative examples:

[0127] The synthesized diamine monomer was structurally characterized using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and mass spectrometry. The FTIR spectrometer was purchased from Thermo Fisher Scientific MA, model IS 50; the NMR spectrometer was purchased from Bruker, model AVANCE Ш 600MHz spectrometer; for mass spectrometry, the sample was diluted in acetonitrile and tested using positive ion mode, with data recorded on an ESI-MS (Waters Xevo G2-XS).

[0128] In the following examples, NMP has a boiling point of 202°C and a density of 1.028 g / mL.

[0129] Example 1

[0130] S1. At 25°C, 90 mmol of diamine monomer 3,5-diaminobenzoic acid (X1) was added to a 500 mL three-necked flask under nitrogen protection, followed by 108 mL of NMP (boiling point 202°C). After the diamine was completely dissolved, 30 mmol of aromatic dianhydride 4,4'-(hexafluoroisopropene)phthalic anhydride (Y1) was added for the first mixing. The mixture was then stirred at 25°C for 12 hours. The molar ratio of diamine monomer to dianhydride monomer was 3:1, and the solid content of the product after the first mixing was 20 wt%.

[0131] S2. After the reaction is complete, 36 mL of toluene, a dehydrating agent, is added. After refluxing at 180 °C for 10 hours, a homogeneous solution is obtained, which includes a diamine monomer containing a carboxyl group and an imide ring, and the remaining unreacted diamine monomer X1. The amount of dehydrating agent used is 33 vol% of the solvent volume.

[0132] S3. The homogeneous solution was subjected to vacuum distillation. Toluene was distilled off at 120°C for 0.4 h, and NMP was distilled off at 165°C for 0.7 h. The product was cooled to 25°C under vacuum to obtain a solid mixture of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X1.

[0133] S4. Add methanol to the solid mixture obtained in step S3, stir and wash, and then filter to obtain a filtrate containing diamine monomer X1 and a diamine solid product containing carboxyl and imide rings. Precipitate the filtrate in water to obtain diamine monomer X1 solid.

[0134] S5. The obtained diamine solid product containing carboxyl and imide rings is redissolved in DMF and activated carbon powder is added for adsorption for 12 h. Then the activated carbon powder is filtered out, and the solid product is precipitated in a mixed solution of methanol and water (methanol to water volume 1:1). Then it is filtered and dried (temperature 70℃, time 12 h) to obtain diamine monomer A1 containing both carboxyl and imide rings.

[0135] The specific reaction process of diamine monomer A1 is shown below:

[0136]

[0137] The diamine monomer A1 was characterized, and its infrared spectrum is shown below. Figure 1 As shown (powder, υ, cm) -1 ): 3371cm -1 3285cm -1 3201cm -1 (NH stretching), 1780cm -1 (imide carbonyl asymmetric stretching), 1718cm -1 (symmetric stretching of imide carbonyl group), 1387cm -1 (imide-CN); 1H NMR spectrum 1 H-NMR spectrum as shown Figure 2 The values ​​(ppm) shown (600 MHz, DMSO) are 12.8, 8.14, 7.95, 7.73, 7.25, 7.11, 6.79, and 5.62. Mass spectrometry: [M+H] + Theoretical value: 712.52, Test value: 712.01.

[0138] The characterization spectra shown above indicate that the novel diamine monomer has distinct characteristic peaks of carboxyl and imide rings, and its molecular weight is consistent with the theoretical value, indicating that the novel monomer was successfully prepared.

[0139] Example 2

[0140] S1. At 30°C, the diamine monomer containing carboxyl triptene diamine (X9) (105 mmol) was added to a 500 mL three-necked flask under nitrogen protection, and then 261 mL of NMP was added. After the diamine was completely dissolved, the aromatic dianhydride triptene dianhydride (Y17) (30 mmol) was added for the first mixing, and the mixture was stirred at 30°C for 24 hours. The molar ratio of the diamine monomer to the dianhydride monomer was 3.5:1, and the solid content of the product after the first mixing was 15 wt%.

[0141] S2. After the reaction is complete, 52 mL of xylene, a dehydrating agent, is added. After refluxing at 175 °C for 8 hours, a homogeneous solution is obtained, consisting of a diamine monomer containing a carboxyl group and an imide ring, and the remaining unreacted diamine monomer X-9. The amount of dehydrating agent used is 20 vol% of the solvent volume.

[0142] S3. The reaction solution was subjected to vacuum distillation. Toluene was distilled off at 130°C for 0.5 h, and NMP was distilled off at 172°C for 1.5 h. The product was cooled to 25°C under vacuum to obtain a solid mixture of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X9.

[0143] S4. Add methanol to the solid mixture obtained in step S3, stir and wash, and then filter to obtain a filtrate containing diamine monomer X9 and a diamine solid product containing carboxyl and imide rings. Precipitate the filtrate in water to obtain solid monomer X9.

[0144] S5. The obtained diamine solid product containing carboxyl and imide rings is redissolved in DMF and activated carbon powder is added for adsorption for 15 h. Then the activated carbon powder is filtered out, and the solid product is precipitated in a mixed solution of methanol and water (volume ratio of water to methanol is 2:1). Then it is filtered and dried (temperature 60℃, time is 20 h) to obtain diamine monomer A2 containing both carboxyl and imide rings.

[0145] The specific reaction process of diamine monomer A2 is shown below:

[0146]

[0147] The diamine monomer A2 was characterized, and the infrared spectrum (powder, υ, cm) was obtained. -1 ): 3342cm -1 3217cm -1 3112cm -1 (NH stretching), 1775cm -1 (imide carbonyl asymmetric stretching), 1721 cm -1 (symmetric stretching of imide carbonyl group), 1362 cm -1 (Imidamine-CN). Mass spectrometry: [M+H]+ Theoretical value: 1015.05, Test value: 1014.66.

[0148] The characterization spectra shown above indicate that the novel diamine monomer has distinct characteristic peaks of carboxyl and imide rings, and its molecular weight is consistent with the theoretical value, indicating that the novel monomer was successfully prepared.

[0149] Example 3

[0150] S1. At 25°C, the diamine monomer 4,4-diaminobiphenyl-2,2-dicarboxylic acid (X7) (69 mmol) was added to a 500 mL three-necked flask under nitrogen protection, followed by the addition of 207 mL of NMP. After the diamine was completely dissolved, the aromatic dianhydride binaphthyl dianhydride (Y15) (30 mmol) was added for the first mixture, and the mixture was stirred at 50°C for 18 hours. The molar ratio of the diamine monomer to the dianhydride monomer was 2.3:1, and the solid content of the product after the first mixture was 13 wt%.

[0151] S2. After the reaction is complete, 83 mL of dehydrating agent chlorobenzene is added, and the mixture is refluxed at 180 °C for 8 hours to obtain a homogeneous solution of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X-7; wherein, the amount of dehydrating agent used is 40 vol% of the solvent amount;

[0152] S3. The reaction solution was subjected to vacuum distillation. Toluene was distilled off at 112°C for 0.6 h, and NMP was distilled off at 166°C for 1.3 h. The product was cooled to 25°C under vacuum to obtain a solid mixture of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X7.

[0153] S4. Add methanol to the solid mixture obtained in step S3, stir and wash, and then filter to obtain a filtrate containing diamine monomer X7 and a diamine solid product containing carboxyl and imide rings. Precipitate the filtrate in water to obtain solid monomer X7.

[0154] S5. The obtained diamine solid product containing carboxyl and imide rings was redissolved in DMF and adsorbed with activated carbon powder for 9 hours. Then the activated carbon powder was filtered out, and the solid product was precipitated in a mixed solution of methanol and water (volume ratio of water to methanol was 0.5:1). The product was then filtered and dried (temperature 110℃, time 17 hours) to obtain diamine monomer A3 containing both carboxyl and imide rings.

[0155] The specific reaction process of diamine monomer A3 is shown below:

[0156]

[0157] The diamine monomer A3 was characterized, and its infrared spectrum (powder, υ, cm⁻¹) was obtained. -1): 3329cm -1 3210cm -1 3100cm -1 (NH stretching), 1715cm -1 (Imide carbonyl asymmetric stretching), 1650cm -1 (symmetric stretching of imide carbonyl group), 1353cm -1 (Imidamine-CN). Mass spectrometry: [M+H] + Theoretical value: 902.83, Test value: 902.22.

[0158] The characterization spectra shown above indicate that the novel diamine monomer has distinct characteristic peaks of carboxyl and imide rings, and its molecular weight is consistent with the theoretical value, indicating that the novel monomer was successfully prepared.

[0159] Example 4

[0160] S1. At 25°C, 105 mmol of diamine monomer 2,5-diaminobenzoic acid (X3) was added to a 500 mL three-necked flask under nitrogen protection. 216 mL of NMP was then added. After the diamine was completely dissolved, 30 mmol of aromatic dianhydride 1,4,5,8-naphthalenetetracarboxylic anhydride (Y12) was added for the first mixing. The mixture was stirred at 100°C for 12 hours. The molar ratio of diamine monomer to dianhydride monomer was 3.5:1, and the solid content of the product after the first mixing was 10 wt%.

[0161] S2. After the reaction is complete, 54 mL of xylene, a dehydrating agent, is added. After refluxing at 175 °C for 12 hours, a homogeneous solution of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X3 is obtained; wherein, the amount of dehydrating agent is 25 vol% of the solvent volume.

[0162] S3. The homogeneous solution was subjected to vacuum distillation. Toluene was distilled off at 129°C for 0.5 h, and NMP was distilled off at 167°C for 1.5 h. The product was cooled to 25°C under vacuum to obtain a solid mixture of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X3.

[0163] S4. Add methanol to the solid mixture obtained in step S3, stir and wash, and then filter to obtain a filtrate containing diamine monomer X3 and a diamine solid product containing carboxyl and imide rings. Precipitate the filtrate in water to obtain solid monomer X3.

[0164] S5. The obtained diamine solid product containing carboxyl and imide rings is redissolved in DMAc and activated carbon powder is added for adsorption for 10 h. Then the activated carbon powder is filtered out, and the solid product is precipitated in a mixed solution of methanol and water (volume ratio of methanol to water is 1.5:1). Then it is filtered and dried (temperature 80℃, time is 30 h) to obtain diamine monomer A4 containing both carboxyl and imide rings.

[0165] The specific reaction process of diamine monomer A4 is shown below:

[0166]

[0167] The diamine monomer A4 was characterized, and its infrared spectrum (powder, μ, cm⁻¹) was obtained. -1 )like Figure 3 As shown: 3330cm -1 3212cm -1 3090cm -1 (NH stretching), 1714cm -1 (imide carbonyl asymmetric stretching), 1659cm -1 (symmetric stretching of imide carbonyl group), 1358cm -1 (imide-CN); 1H NMR spectrum 1 H-NMR spectrum as shown Figure 4 The values ​​(ppm) shown are (600 MHz, DMSO): δ 12.8, 8.76, 7.32, 7.16, 6.79, 5.59. Mass spectrometry: [M+H] + Theoretical value: 536.46, Test value: 535.87.

[0168] The characterization spectra shown above indicate that the novel diamine monomer has distinct characteristic peaks of carboxyl and imide rings, and its molecular weight is consistent with the theoretical value, indicating that the novel monomer was successfully prepared.

[0169] Example 5

[0170] S1. At 29°C, the diamine monomer 5,5'-methylenebis(2-aminobenzoic acid) (X8) (75 mmol) was added to a 500 mL three-necked flask under nitrogen protection, followed by 87 mL of NMP. After the diamine was completely dissolved, the alicyclic dianhydride bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (Y21) (30 mmol) was added for the first mixing. The mixture was then stirred at 29°C for 12 hours. The molar ratio of the diamine monomer to the dianhydride monomer was 2.5:1, and the solid content of the product after the first mixing was 25 wt%.

[0171] S2. After the reaction is complete, 26 mL of toluene, a dehydrating agent, is added. After refluxing at 180 °C for 10 hours, a homogeneous solution of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X8 is obtained. The amount of dehydrating agent used is 30 vol% of the solvent volume.

[0172] S3. The homogeneous solution was subjected to vacuum distillation. Toluene was distilled off at 129°C for 0.5 h, and NMP was distilled off at 180°C for 0.9 h. The product was cooled to 25°C under vacuum to obtain a solid mixture of a diamine monomer containing a carboxyl group and an imide ring and the remaining unreacted diamine monomer X8.

[0173] S4. Add methanol to the solid mixture obtained in step S3, stir and wash, and then filter to obtain a filtrate containing diamine monomer X8 and a diamine solid product containing carboxyl and imide rings. Obtain solid monomer X8 by precipitating the filtrate in water.

[0174] S5. The obtained diamine solid product containing carboxyl and imide rings is redissolved in DMAc and activated carbon powder is added for adsorption for 7 hours. Then the activated carbon powder is filtered out, and the solid product is precipitated in a mixed solution of methanol and water (methanol to water volume ratio of 4:1). Then it is filtered and dried (temperature 90℃, time 30 hours) to obtain diamine monomer A5 containing both carboxyl and imide rings.

[0175] The specific reaction process of diamine monomer A5 is shown below:

[0176]

[0177] The diamine monomer A5 was characterized, and the infrared spectrum (powder, υ, cm) was obtained. -1 ): 3334cm -1 3216cm -1 3101cm -1 (NH stretching), 1770cm -1 (imide carbonyl asymmetric stretching), 1731 cm -1 (symmetric stretching of imide carbonyl group), 1359cm -1 (Imidamine-CN). Mass spectrometry: [M+H] + Theoretical value: 784.73, Test value: 783.96.

[0178] The characterization spectra shown above indicate that the novel diamine monomer has distinct characteristic peaks of carboxyl and imide rings, and its molecular weight is consistent with the theoretical value, indicating that the novel monomer was successfully prepared.

[0179] Example 6

[0180] The diamine monomer was prepared according to the method in Example 5, wherein:

[0181] Steps S1 and S2 are the same as in Example 5;

[0182] S3. Pour the homogeneous solution into a mixed solution of ethanol and water (1:1), filter to obtain a mixed solid phase, and then dry it under vacuum at 80°C for 12 hours.

[0183] S4. Dissolve the mixed solid phase in N,N-dimethylacetamide, add activated carbon powder for adsorption for 7 hours, then filter out the activated carbon powder, and precipitate the solid product in a mixed solution of methanol and water (methanol to water volume ratio of 4:1), then filter and dry (temperature 90℃, time 30 hours) to obtain a diamine monomer A6 containing both carboxyl and imide rings.

[0184] Comparative Example 1

[0185] This comparative example provides a carboxylated diamine monomer, wherein the diamine monomer is 3,5-diamino-2,4,5-trimethylbenzoic acid (Abdulhamid MA, Genduso G, Wang Y, et al. Plasticization-resistant carboxyl-functionalized 6FDA-polyimide of intrinsic microporosity (PIM-PI) for membrane-based gas separation[J]. Industrial & Engineering Chemistry Research, 2019, 59(12): 5247-5256.).

[0186] Specifically, the diamine monomer was prepared from 2,4,6-trimethylbenzoic acid to 2,4,6-trimethyl-3,5-dinitrobenzoic acid via a two-step process as shown below, with the molecular weight of 3,5-diamino-2,4,5-trimethylbenzoic acid (tested at 195.13 g / mol). 2,4,6-trimethylbenzoic acid (6.1 mmol) was suspended in sulfuric acid (13 mL), and then nitric acid (20 mL) was added dropwise. The reaction mixture was stirred overnight at room temperature. The reaction mixture was then poured into water, precipitating the dinitro compound. The precipitate was filtered, washed three times with water, and then dried under vacuum at 100 °C for 24 h to obtain a 2,4,6-trimethyl-3,5-dinitrobenzoic acid powder product (1.24 g, yield 80%). 2,4,6-Trimethyl-3,5-dinitrobenzic acid (I) (0.64 g) was suspended in methanol (10 mL), followed by the addition of Pd / C (10%) (0.1 g) and N₂H₄·H₂O (3 mL). The reaction mixture was refluxed for 2 days, cooled to room temperature, filtered through a Celite filter, and then concentrated in a Rotavap system. The solution was added to dichloromethane, yielding a white precipitate. The resulting solid was filtered and dried in an oven at 90 °C for 24 hours to give pure 3,5-diamino-2,4,5-trimethylbenzoic acid (0.44 g, 90% yield).

[0187]

[0188] Comparative Example 2

[0189] This comparative example provides a novel diamine monomer (Example 1 of CN118684593A). The specific preparation process is as follows: first, 3,5-dinitro-N (3,4-dihydroxyphenylethyl) benzamide is prepared, and then 3,5-diamino-N (3,4-dihydroxyphenylethyl) benzamide is prepared with a yield of 92%.

[0190]

[0191] Comparative Example 3

[0192] This comparative example provides a diamine monomer having a nitrogen heterocycle and benzo[a]cyclobutene structure and its preparation method (CN118108661B, Synthesis Example 1). The diamine monomer is prepared by reacting 2-hydroxy-5-(pyridinyl-4-yl)benzaldehyde (9.96 g, 50 mmol), 4-bromobenzo[a]cyclobutene (9.15 g, 50 mmol), and potassium carbonate (6.91 g, 50 mmol) to obtain intermediate product X1. Then, the above product (7.53 g, 25 mmol), aniline hydrochloride (12.96 g, 0.1 mol), and aniline (23.28 g, 0.25 mol) are used to prepare diamine monomer D3, with the following structural formula:

[0193]

[0194] Performance testing

[0195] The purity and yield of the diamine monomers in the examples and comparative examples were tested, and the results are shown in Table 1.

[0196] (1) Purity: High performance liquid chromatography was used for testing. The instrument used was a Shimadzu LC-20A.

[0197] (2) Yield = (mass of final purified product / mass of theoretically calculated product) × 100%.

[0198] Table 1

[0199] purity(%) Yield (%) Example 1 99.91 92.5 Example 2 99.89 93.6 Example 3 99.93 97.2 Example 4 99.95 95.5 Example 5 99.88 92.3 Example 6 98.59 83.4 Comparative Example 1 / 90％ Comparative Example 2 / 92％ Comparative Example 3 / /

[0200] / indicates that purity and yield are not recorded in the existing technology.

[0201] As shown in the table above, the present invention provides a method for preparing a carboxyl- and imide-containing cyclic diamine monomer. The method uses a carboxyl-containing aromatic diamine compound and a dianhydride monomer as starting reactants to synthesize a carboxyl-containing diamine in a one-step process. The preparation route is simple, unreacted materials and solvents can be recovered, and the product has high purity and high yield.

[0202] As can be seen from Examples 1-6, the purity of the prepared carboxyl- and imide-containing cyclic diamine monomer is ≥98%, and the yield is ≥80%. In particular, as can be seen from Examples 5 and 6, purifying the reaction product using the specific method of this invention can further improve both the purity and yield of the final diamine monomer.

[0203] As can be seen from Comparative Example 1, although the yield of the carboxyl-containing diamine prepared by the two-step method is relatively high, the purity of the product is not disclosed. At the same time, the preparation steps of Comparative Example 1 are complex and use a variety of solvents and catalysts.

[0204] In summary, the one-step synthesis method for preparing carboxyl and imide cyclic diamines provided by this invention has a simple reaction route, can effectively recover unreacted monomers and solvents, and yields products with high purity and high yield. It can be used as a monomer raw material for preparing polyimides and related functional polymers, or provide a variety of modification methods for polymers.

[0205] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A diamine monomer, characterized in that, The diamine monomer contains both a carboxyl group and an imide ring.

2. The diamine monomer according to claim 1, wherein, The diamine monomer has the structure shown in Formula I; Wherein, ring A is derived from an aromatic diamine compound, and optionally, ring A contains a substituent selected from H, halogens, OH, COOH, SO3H, NO2, -H2PO4, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 The aryl group is selected from any one of the aromatic dianhydride compounds; ring B is derived from aromatic dianhydride compounds and / or alicyclic dianhydride compounds, optionally, ring B contains a substituent selected from H, halogen, OH, COOH, SO3H, NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

3. The diamine monomer according to claim 1 or 2, wherein, The substituents of ring A are selected from halogens, OH, COOH, H, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups; Preferably, the substituents of ring B are selected from halogens, OH, COOH, H, unsubstituted or substituted C1-C6 straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

4. The diamine monomer according to any one of claims 1-3, wherein, A is selected from at least one of the following groups: In this context, the dashed lines represent the insertion positions of the groups, R1-R 11 Each is independently selected from H, halogen, OH, COOH, SO3H, NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

5. The diamine monomer according to any one of claims 1-4, wherein, B is selected from at least one of the following groups: In this context, the dashed line indicates the insertion position of the functional group; R 12 -R 52 Each is independently selected from H, halogen, OH, COOH, SO3H, NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

6. A method for preparing a diamine monomer, characterized in that, The preparation method includes: (1) In the presence of a protective atmosphere, monomer A, monomer B and solvent are first mixed and then a first reaction is carried out; (2) After mixing the product of the first reaction with the dehydrating agent, a second reaction is carried out; (3) The product of the second reaction was subjected to vacuum distillation and cooling in sequence to obtain the diamine monomer; Wherein, monomer A is an aromatic diamine compound containing a carboxyl group, and monomer B is selected from aromatic dianhydride compounds and / or alicyclic dianhydride compounds.

7. The preparation method according to claim 6, wherein, The solvent has a boiling point of 140-300℃; Preferably, the solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol, and dimethyl sulfoxide; Preferably, the monomer A, the monomer B, and the solvent are mixed such that the solid content of the product after the first mixture is 5-35 wt%. Preferably, the molar ratio of monomer A to monomer B is 2-4:1, more preferably 2.3-3.5:1; Preferably, the conditions for the first reaction include: a reaction temperature of -5°C to 120°C and a reaction time of 9-36 hours.

8. The preparation method according to claim 6 or 7, wherein, Monomer A contains a substituent selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups; Preferably, monomer A is selected from at least one of the following compounds: Among them, R 53 -R 63 Each is independently selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

9. The preparation method according to any one of claims 6-8, wherein, Monomer B contains substituents selected from H, halogens, -OH, -COOH, -SO3H, -NO2, -H2PO4, unsubstituted or halogenated C1-C. 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups; Preferably, monomer B is selected from at least one of the following compounds: Among them, R 64 -R 104 Each is independently selected from H, halogen, OH, COOH, SO3H, NO2, -H2PO4, unsubstituted or halogenated C1-C 10 Straight-chain or branched alkyl groups, C6-C 10 Any of the aryl groups.

10. The preparation method according to any one of claims 6-9, wherein, The conditions for the second reaction include reflux at 140-210°C for 6-36 hours; Preferably, the dehydrating agent is selected from at least one of toluene, xylene, and chlorobenzene; Preferably, the amount of the dehydrating agent is 20-60 vol% of the amount of solvent, more preferably 24-45 vol%.

11. The preparation method according to any one of claims 6-10, wherein, The vacuum distillation is a two-stage vacuum distillation; Preferably, the vacuum distillation includes the following steps: Distilled at 90-140℃ for 0.1-6 hours, then distilled at 150-210℃ for 0.1-10 hours; Preferably, the cooling is carried out under vacuum conditions, and more preferably, the temperature is reduced to below 30°C.

12. The preparation method according to any one of claims 6-11, wherein, The method further includes: (4) The cooled product is mixed with solvent I for the third time, and then separated into solid and liquid phases to obtain the solid phase; (5) The solid phase, solvent II and adsorbent are mixed for the fourth time, and after the second solid-liquid separation, the liquid phase is dried to obtain the diamine monomer.

13. The preparation method according to claim 12, wherein, Solvent I is selected from at least one of ethanol, methanol, and acetone; Preferably, the method further includes: precipitating the liquid phase obtained from the first solid-liquid separation in water; Preferably, solvent II is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, and dichloromethane; Preferably, the fourth mixing time is 2-36 hours, more preferably 5-12 hours; Preferably, the adsorbent is selected from at least one of activated carbon powder, activated carbon granules, starch, and macroporous adsorption resin; Preferably, the method further includes: precipitating the liquid phase obtained from the second solid-liquid separation in a mixed solution of water and solvent I; Preferably, the drying conditions include: a drying temperature of 50-120°C and a drying time of 2-72 hours.

14. A diamine monomer prepared by any one of claims 6-13.

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