Diamine monomer and preparation method thereof

Abstract

The invention relates to the field of organic materials, in particular to a diamine monomer and a preparation method thereof. The diamine monomer provided by the invention has a structure as shown in a formula (IV), can effectively balance the problems of high solubility during processing and solvent resistance after molding, realizes both the solubility and the solvent resistance, and meanwhile, shows excellent anti-static capability. The preparation method provided by the invention comprises the following steps: preparing an aniline pentamer as shown in a formula (II) based on a Buchwald-Hartwisting cross-coupling reaction, then adding a Boc group to prepare an aniline pentamer-Boc as shown in a formula (III), and then removing protective groups at two ends through hydrogenation to obtain the aniline pentamer diamine monomer as shown in a formula (IV). The preparation method is simple in synthetic route, simple and convenient to operate, efficient in reaction, wide in reaction substrate application range, low in preparation cost, high in product yield and purity and capable of meeting the polymerization requirement.

Description

Technical Field

[0001] The present invention relates to the field of organic materials, and particularly relates to a diamine monomer and a preparation method thereof. Background Art

[0002] Rapid prototyping has become an important trend in the development of modern social processes. This method can not only save time and energy consumption, conform to the concept of green environmental protection, but also be applicable to the manufacture of complex parts. At present, the rapid prototyping processes of engineering plastics and their composites mainly include injection molding, 3D printing, winding molding, etc., and some of the 3D printing and winding molding belong to solution processing methods. If the solution processing method is to achieve rapid prototyping, it needs to meet two conditions: high solid content and easy removal of the solvent (if the solvent has a low boiling point, it is relatively easy to remove). Therefore, developing a resin with high solubility in a low-boiling solvent is the most ideal solution.

[0003] However, as an engineering plastic, it must have excellent processing properties, mechanical and solvent resistance properties. Otherwise, it is prone to deformation during use, affecting its practical application. How to balance the solubility during polymer processing and the solvent resistance after molding has always been the key research direction of scientific researchers.

[0004] Taking polyimide resin as an example, it is a typical engineering plastic with excellent high and low temperature resistance, radiation resistance and other properties, and is widely used in high-end fields such as aviation and aerospace. However, it also faces the problem of balancing the improvement of solubility during processing and the improvement of solvent resistance after molding.

[0005] As a crucial type of polymer monomer, diamine compounds can be used to prepare various high-molecular materials (such as polyimide, etc.) through polycondensation reactions. Traditional diamine monomers represented by ethylenediamine, p-phenylenediamine, biphenylenediamine, etc., often expose two major disadvantages when participating in polymerization reactions to form polymers: First, there is a contradictory relationship between the dissolution performance and solvent resistance performance of the materials. Generally, before the polymer is formed, we hope it shows excellent dissolution performance for easy molding. After the material is formed, we hope the material has excellent solvent resistance performance. How to find a balance between these two performances has become an important topic continuously explored by scientific researchers. Second, such materials exhibit insulating properties, and static electricity is difficult to conduct, which poses a potential safety hazard in the production process and threatens production safety.

[0006] Due to the large molecular polarity and strong intermolecular forces of traditional polyimide resins, they are insoluble in common low-boiling solvents and cannot meet the requirements of rapid prototyping, thus limiting their application scope. Currently, this type of polyimide resin process mainly uses polar aprotic solvents such as N,N′-dimethylacetamide (DMAc), N,N′-dimethylformamide (DMF), N-methylpyrrolidone (NMP), etc. These solvents have high boiling points and are difficult to remove, requiring relatively high drying temperatures to ensure complete removal of the solvents.

[0007] Currently, there are many studies on solubilizing diamine monomers, mainly including two strategies. One is to introduce a structure with affinity for the solvent to enhance the solvation effect, such as introducing fluorine-, silicon-, phosphorus-containing groups or hydroxyl groups; the other is to introduce a structure that makes the polymer structure "loose", such as bridging groups, side groups, and "loops". The following are some typical cases:

[0008] Patent CN105906808B discloses a diamine monomer containing tert-butyl and polyarylether structures, namely 4,4′-(3-tert-butyl-4-aminophenoxy)-diphenyl ether. The polyimide obtained by polymerizing this monomer with a conventional dianhydride not only weakens the intermolecular interaction of the polyimide molecular chain, changes the chain packing mode, and greatly improves its solubility due to the introduction of tert-butyl, but also hinders the rotation of the polyimide molecular chain, thereby increasing its glass transition temperature and thermal stability. Research shows that this polymer is soluble in low-boiling solvents such as chloroform and tetrahydrofuran at room temperature.

[0009] Patent CN104987506B discloses a preparation method of an aromatic diamine (3,3′-di-tert-butyl-4,4′-diaminophenyl-3′-benzofuran methane) containing tert-butyl and benzofuran structures. The polyimide prepared from this diamine has a "loose" structure due to the presence of a non-coplanar structure and substituents, greatly improving the solubility of the polyimide. This type of polymer can not only dissolve in high-boiling organic solvents but also dissolve well in low-boiling solvents such as tetrahydrofuran, chloroform, dichloromethane, ethyl acetate, and acetone.

[0010] Patent CN110256672B discloses a soluble polyimide containing phosphorus, fluorine, and large side groups synthesized from (diaminoanthracene-fluoro)phosphonic acid and bis(4-fluorophenyl)anthracenedifurantetrone. This method not only increases the interaction between the polymer and solvent molecules but also makes the polymer structure loose. Research shows that this polymer can dissolve in solvents such as tetrahydrofuran and acetone.

[0011] The above prior arts CN105906808B, CN104987506B and CN110256672B introduce non-coplanar structures, or substituents, etc. into the polyimide structure through structural design to prepare soluble polyimides. These techniques can all improve the solubility of the polymer, but they also reduce the solvent resistance of the polymer after molding. That is, they also have the problem that it is difficult to balance the solubility during processing and the solvent resistance after molding. How to further regulate the structure to both improve the solubility of the polymer and not lose or improve the solvent resistance of the material after molding has become the main scientific problem.

[0012] Regarding the research on solvent-resistant polyimide materials, it is currently mainly concentrated in the field of permeable membranes. Researchers mainly use means such as crosslinking and complexation to increase the interaction force between polymer chains. For example, Patent CN112604508A discloses a method for preparing a polyimide membrane with excellent solvent resistance by using amino cycloalcohol antibiotics and their derivatives as crosslinking agents; Patent CN104927072A discloses a method for introducing nitrile groups into the polyimide structure and using the crosslinking characteristics of nitrile groups at 280-300 °C to prepare a crosslinked solvent-resistant polyimide membrane; Patent CN114191991A discloses a method for introducing metal ions into the system and relying on the formation of coordination bonds to improve the solvent resistance of polyimide films.

[0013] The above prior arts CN112604508A, CN104927072A and CN114191991A mainly achieve the solvent resistance of polyimide films through means such as crosslinking and complexation. The preparation process of this series of polyimide films is still to dissolve polyimide resin in high-boiling solvents such as DMAc, and then cast and form. The polyimide resin used is a conventional commercial polyimide resin, and the solubility of this kind of polyimide resin in low-boiling solvents is limited, making it difficult to adapt to processes such as rapid prototyping.

[0014] There is not much research on antistatic functional monomers at present. Patent CN1088454C discloses that the terminal amino groups of aniline dimers, trimers, and tetramers are protected with polyfunctional compounds, or substituted products of diphenylamine are used to synthesize electroactive macromonomers with p-phenylenediamine at room temperature. This can be polymerized with traditional monomers to synthesize electroactive polymers, making them more widely used in antistatic materials and anti-corrosion materials. For the preparation of antistatic polymers, a relatively common method is the blending method, that is, directly adding electroactive substances to the polymer system. For example, Patent CN109880094B adds a certain amount of conductive titanium nitride and titanium carbonitride to the system, endowing the material with excellent antistatic function.

[0015] In the above prior art, the monomers disclosed in Patent CN1088454C are mainly compounds such as diacids, dihaloalkanes, and diols, and do not include diamine monomers. In the traditional blending method, there are problems such as uneven mixing, unstable interfaces, and a decrease in mechanical properties as the addition amount of electroactive substances increases.

[0016] Patent PCTUS9825555 discloses a method for preparing diamine monomers with a similar structure. The synthesized diamines include diamines containing triphenylamine oligomer segments and diamines containing heptaphenylamine oligomer segments. They use a palladium-catalyzed reaction to obtain intermediates in one pot, and finally reduce them to obtain the target monomers. Since they use the one-pot method, the purity of the monomers is difficult to meet the requirements of polymerization. At the same time, the diamine containing heptaphenylamine oligomer segments needs to undergo 2 couplings, which greatly increases the preparation cost. Summary of the Invention

[0017] In view of this, the present invention provides a diamine monomer and a preparation method thereof. The diamine monomer provided by the present invention can effectively balance the problems of high solubility required during processing and solvent resistance required after molding, achieving both of them. At the same time, it exhibits excellent antistatic ability. The preparation method provided by the present invention has a simple route, is easy to operate, has high reaction efficiency, and can improve the product yield and purity.

[0018] The present invention provides a diamine monomer having the structure shown in formula (Ⅳ):

[0019]

[0020] The present invention also provides a preparation method of the diamine monomer described in the above technical solution, including the following steps:

[0021] A) The compound shown in formula (Ⅰ) reacts with a p-phenylenediamine reactant to form a compound shown in formula (Ⅱ);

[0022] The p-phenylenediamine reactant is p-phenylenediamine and / or p-phenylenediamine hydrochloride;

[0023] B) The compound shown in formula (Ⅱ) undergoes a Boc coupling reaction with di-tert-butyl dicarbonate to form a compound shown in formula (Ⅲ);

[0024] C) The compound shown in formula (Ⅲ) undergoes deprotection and hydrogenation reactions to obtain the diamine monomer shown in formula (Ⅳ);

[0025]

[0026] Preferably, in step A), the molar ratio of the compound shown in formula (Ⅰ) to the p-phenylenediamine reactant is (2.0 - 2.5):1.

[0027] Preferably, in step A), the reaction temperature is 50 - 100 °C.

[0028] Preferably, in step A):

[0029] The reaction is carried out under the action of a catalyst; wherein, the catalyst is at least one of a metal palladium compound, a metal rhodium compound, and a metal ruthenium compound; the molar ratio of the catalyst to the compound shown in formula (I) is (0.0002 - 0.001):1;

[0030] The reaction is carried out in the presence of a ligand; wherein, the ligand is a phosphine-containing compound, including trimethylphosphine, triethylphosphine, tripropylphosphine, triisopropylphosphine, tributylphosphine, tricyclohexylphosphine, triphenylphosphine, triisopropylphosphine, bis(2-diphenylphosphinophenyl) ether, 1,1'-binaphthalene-2,2'-bis(diphenylphosphine), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, 4,5-bis(diphenylphosphino)-9,9-dimethyloxanthrene, 2-(dicyclohexylphosphino)-3,6-dimethoxy-2',4',6'-tri-I-propyl-1,1'-biphenyl, 2-dicyclohexylphosphino-2',6'-diisopropoxy-1,1'-biphenyl, 2-di-tert-butylphosphino-2',4',6'-triisopropylbiphenyl, 2-(di-tert-butylphosphino)-3,6-dimethoxy-2',4',6'-tri-1-propyl-1,1'-biphenyl, 1,1'-bis(diphenylphosphino)ferrocene, (R)-(-)-1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyldi-tert-butylphosphine, 5-di-tert-butylphosphino-1',3',5'-triphenyl-1'H-[1,4']dipyrazole, N-[2-di(1-adamantyl)phosphinophenyl]morpholine; the molar ratio of the ligand to the catalyst is (1 - 10):1;

[0031] The reaction is carried out in the presence of a basic substance; wherein, the basic substance is at least one of sodium tert-butoxide, potassium tert-butoxide, sodium amide, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, 4-dimethylaminopyridine, triethylamine, K 2 CO 3 、Na 2 CO 3 、Cs 2 CO 3 ; the molar ratio of the basic substance to the compound shown in formula (I) is (1.5 - 10):1;

[0032] The reaction is carried out in a solvent medium; wherein, the solvent is an organic solvent or a mixed solvent of an organic solvent and water; wherein, the organic solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, toluene, benzene; the mass of the solvent is 5 - 20 times the mass of the compound shown in formula (I);

[0033] The reaction is carried out under a protective atmosphere.

[0034] Preferably, in step B), the molar ratio of the compound shown in formula (II) to di-tert-butyl dicarbonate is 1:(3 - 6).

[0035] Preferably, in step B), the temperature of the reaction is 40 - 100 °C.

[0036] Preferably, in step B):

[0037] The reaction is carried out in the presence of a basic substance; wherein, the basic substance is at least one of sodium tert-butoxide, potassium tert-butoxide, sodium amide, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, 4-dimethylaminopyridine, triethylamine, KOH, NaOH, K 2 CO 3 、Na 2 CO 3 、Cs 2 CO 3 ; the molar ratio of the basic substance to the compound shown in formula (II) is (0.05 - 5):1;

[0038] The reaction is carried out in a solvent medium; wherein, the solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether.

[0039] Preferably, in step C):

[0040] The hydrogen source reagent used for the hydrogenation is at least one of H 2 、hydroxylamine hydrochloride, and ammonium formate; the molar ratio of the hydrogen source reagent to the compound shown in formula (III) is (3 - 10):1;

[0041] The reaction of step C) is carried out in a solvent medium; wherein, the solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether.

[0042] Preferably, step A) specifically includes: under a protective atmosphere, mixing the compound shown in formula (I), a p-phenylenediamine reactant, a catalyst, a ligand, a basic substance, and a solvent, heating and reacting to form the compound shown in formula (II);

[0043] Step B) specifically includes: mixing the compound shown in formula (II), di-tert-butyl dicarbonate, a basic substance, and a solvent, refluxing and reacting to form the compound shown in formula (III);

[0044] Step C) specifically includes: mixing the compound shown in formula (III), a hydrogen source reagent, a basic substance or a catalyst, and a solvent, and performing a deprotection and hydrogenation reaction to form a diamine monomer shown in formula (IV).

[0045] The diamine monomer provided by the present invention is a diamine containing an aniline pentamer. The diamine monomer introduces a solubilizing group, making the polymer obtained by polymerizing it have excellent solubility and being able to easily dissolve in a variety of common low-boiling organic solvents, greatly improving the processing performance and facilitating operations such as forming and processing in actual production. Moreover, when such a polymer is polymerized, only through specific post-treatment steps can the solubilizing group be removed. At this time, the solvent resistance of the material is extremely excellent, effectively breaking the deadlock that it is difficult to balance the solubility and solvent resistance, and achieving the balance of both. In addition, the penta-aniline oligomer segment in the polymer main chain obtained by polymerizing this diamine monomer plays a unique role, endowing the material with excellent electrical properties, being able to efficiently conduct static electricity, showing excellent antistatic ability, effectively solving the static electricity hidden danger caused by the insulation of traditional materials, and providing a strong guarantee for production safety.

[0046] The preparation method of the diamine monomer provided by the present invention first prepares an aniline pentamer shown in formula (II) based on the Buchwald-Hartwig cross-coupling reaction, then adds a Boc group to obtain an aniline pentamer-Boc shown in formula (III), and then removes the protecting groups at both ends by hydrogenation to obtain an aniline pentamer diamine monomer shown in formula (IV). The above preparation method has a simple synthesis route, convenient operation, high reaction efficiency, a wide range of applicable reaction substrates, reduces the preparation cost, and moreover, the product yield and purity are high (the yield reaches more than 90%, and the purity reaches more than 99%), and the monomer purity can meet the requirements of polymerization. Description of the Drawings

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0048] Figure 1 It is a synthesis route diagram of the preparation method of the present invention;

[0049] Figure 2 For the compound shown in formula (II) obtained in step A) in Example 1 1 1H NMR spectrum;

[0050] Figure 3 For the compound shown in formula (III) obtained in step B) in Example 1 1 1H NMR spectrum;

[0051] Figure 4 1H NMR spectrum of the diamine monomer end product shown by formula (IV) obtained in step C) of Example 1 1 1H NMR spectrum

[0052] Figure 5 Thermogravimetric curve of polyimide resin powder PI-1 prepared from the diamine monomer shown by formula (IV) provided by the present invention

[0053] Figure 6 Infrared spectra of polyimide resin powders PI-1 and PI-2 prepared from the diamine monomer shown by formula (IV) provided by the present invention Detailed implementation manners

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0055] In this document, among the technical features described in an open-ended manner, a closed technical solution composed of the listed features is included, and an open technical solution including the listed features is also included.

[0056] The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0057] In this document, regarding a numerical range, unless otherwise specified, the above numerical range is considered continuous and includes the minimum value and the maximum value of this range, as well as each value between such minimum value and maximum value. Further, when the range refers to an integer, each integer between the minimum value and the maximum value of this range is included. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0058] In this document, regarding the unit of a data range, if the unit is only attached after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 50~100 °C means that the units of the left endpoint "50" and the right endpoint "100" are both °C.

[0059] The present invention provides a diamine monomer having the structure shown by formula (IV):

[0060]

[0061] The diamine monomer provided by the present invention is a diamine containing aniline pentamer. This diamine monomer can be polymerized with compounds such as dianhydride to obtain corresponding polymers. These polymers are attached with solubilizing side groups at the bridging positions, forming a non-coplanar molecular chain structure. At the same time, the introduction of these substituents increases the solvation effect, significantly improving the solubility of the polymers. They can be easily dissolved in a variety of common low-boiling organic solvents, greatly enhancing the processing performance and facilitating operations such as forming and processing in actual production. Moreover, when such polymers are polymerized, the solubilizing groups can be removed only through specific post-treatment steps. At this time, the solvent resistance of the material is extremely excellent, effectively breaking the deadlock that it is difficult to balance the solubility and solvent resistance, and achieving the balance of both. In addition, the polyimide obtained by polymerizing the diamine monomer, after heat treatment, the main chain is transformed into a polyaniline oligomer, endowing the material with excellent solvent resistance and antistatic function. The preparation of the above-mentioned diamine monomer mainly involves reactions such as Buchwald-Hartwig cross-coupling reaction, solubilizing group grafting reaction, and reduction hydrogenation. Its main structure is a penta-aniline oligomer chain segment, and there is no relevant report on this structure and its preparation method at present.

[0062] The present invention also provides a preparation method of the diamine monomer described in the above technical solution, including the following steps:

[0063] A) React the compound shown in formula (Ⅰ) with a p-phenylenediamine reactant to form a compound shown in formula (Ⅱ);

[0064] The p-phenylenediamine reactant is p-phenylenediamine and / or p-phenylenediamine hydrochloride;

[0065] B) Perform a Boc coupling reaction on the compound shown in formula (Ⅱ) with di-tert-butyl dicarbonate to form a compound shown in formula (Ⅲ);

[0066] C) Perform deprotection and hydrogenation reactions on the compound shown in formula (Ⅲ) to obtain the diamine monomer shown in formula (Ⅳ);

[0067]

[0068] In the present invention, the synthesis route of the above preparation method is as Figure 1 shown.

[0069] [Regarding step A]:

[0070] A) React the compound shown in formula (Ⅰ) with a p-phenylenediamine reactant to form a compound shown in formula (Ⅱ).

[0071] The reaction route of this step is as follows:

[0072]

[0073] In the present invention, the Boc-group in the compound represented by formula (I) is a conventional group abbreviation in the art, representing tert-butoxycarbonyl. The compound represented by formula (I) is [(4-aminophenyl)(4-bromophenyl)amino]methanoic acid 2-methylpropan-2-yl ester, and its source has no special limitation and can be a commercially available product or prepared according to known preparation methods in the art.

[0074] In the present invention, the p-phenylenediamine reactant is p-phenylenediamine and / or p-phenylenediamine hydrochloride, and its source has no special limitation and can be a commercially available product or prepared according to known preparation methods in the art.

[0075] In the present invention, the molar ratio of the compound represented by formula (I) to the p-phenylenediamine reactant is preferably (2.0 - 2.5):1, specifically can be 2.0:1, 2.05:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, and more preferably 2.05:1.

[0076] In the present invention, the reaction is preferably carried out under the action of a catalyst. The catalyst is preferably at least one of ruthenium metal compounds, rhodium metal compounds and palladium metal compounds, and more preferably a palladium metal compound. The palladium metal compound is preferably Pd(PPh 3 ) 4 , Pd(OAc) 2 , PdCl 2 , PdCl 2 (dppf), PdCl 2 (PPh 3 ) 2 , Pd 2 (dba) 3 or at least one of them. In the present invention, the molar ratio of the catalyst to the compound represented by formula (I) is preferably (0.0002 - 0.001):1, specifically can be 0.0002:1, 0.0003:1, 0.0004:1, 0.0005:1, 0.0006:1, 0.0007:1, 0.0008:1, 0.0009:1, 0.001:1, and more preferably (0.0005 - 0.001):1.

[0077] In the present invention, the reaction is preferably carried out in the presence of a ligand. The ligand is preferably a phosphine ligand, including but not limited to trimethylphosphine, triethylphosphine, tripropylphosphine, triisopropylphosphine, tributylphosphine, tricyclohexylphosphine, triphenylphosphine, triisopropylphosphine, bis(2-diphenylphosphinophenyl) ether (DPEPhos), 1,1'-binaphthalene-2,2'-bis(diphenylphosphine) (BINAP), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (X-Phos), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (XANTPhos), 2-(dicyclohexylphosphino)-3,6-dimethoxy-2',4',6'-tri-i-propyl-1,1'-biphenyl (BrettPhos), 2-dicyclohexylphosphino-2',6'-diisopropoxy-1,1'-biphenyl (RuPhos), 2-di-tert-butylphosphino-2',4',6'-triisopropylbiphenyl (tBuXPhos), 2-(di-tert-butylphosphino)-3,6-dimethoxy-2',4',6'-tri-i-propyl-1,1'-biphenyl (tBuBrettPhos), 1,1'-bis(diphenylphosphino)ferrocene (Dppf), (R)-(-)-1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyldi-tert-butylphosphine (CyPFt-Bu), 5-di-tert-butylphosphino-1',3',5'-triphenyl-1'H-[1,4']dipyrazole (BippyPhos), N-[2-di(1-adamantyl)phosphinophenyl]morpholine (Mor-DalPhos), and further preferably at least one of DPEPhos, BINAP, X-Phos, XANTPhos, and BrettPhos. In the present invention, the molar ratio of the ligand to the catalyst is preferably (1 to 10):1, more preferably (1 to 4):1.

[0078] In the present invention, the reaction is preferably carried out in the presence of a basic substance. Among them, the basic substance includes at least one of metal compounds, organic bases, inorganic bases, and inorganic salts, and is preferably at least one of sodium tert-butoxide, potassium tert-butoxide, sodium amide, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, 4-dimethylaminopyridine, triethylamine, KOH, NaOH, K 2 CO 3 、Na 2 CO 3 、Cs 2 CO 3 and is more preferably at least one of sodium tert-butoxide, potassium tert-butoxide, Cs 2 CO 3At least one of them. In the present invention, the molar ratio of the basic substance to the compound represented by formula (I) is preferably (1.5 - 10):1, specifically it can be 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.

[0079] In the present invention, the reaction is preferably carried out in a solvent medium. The solvent is preferably an organic solvent or a mixed solvent of an organic solvent and water. Among them, the organic solvent is preferably a deoxygenated organic solvent, and the types are preferably at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, toluene, benzene. In the present invention, the solvent is more preferably at least one of tetrahydrofuran, dioxane, toluene, dioxane-water mixed solvent, toluene-water mixed solvent. In the present invention, in the mixed solvent, the volume ratio of the organic solvent to water is preferably (5 - 20):1. In the present invention, the mass of the solvent is preferably 5 - 20 times the mass of the compound represented by formula (I), more preferably 10 - 15 times.

[0080] In the present invention, the reaction is preferably carried out under a protective atmosphere, more preferably a nitrogen atmosphere and / or an argon atmosphere.

[0081] In the present invention, the temperature of the reaction is preferably 50 - 100 °C, specifically it can be 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, more preferably 60 - 80 °C. In the present invention, the reaction time is preferably 6 - 10 h, specifically it can be 6 h, 7 h, 8 h, 9 h, 10 h. In the present invention, stirring is preferably accompanied during the reaction process. Based on the Buchwald-Hartwig cross-coupling reaction, the compound represented by formula (I) reacts with the p-phenylenediamine reactant to form the aniline pentamer represented by formula (II). In the above structure represented by formula (II), the Ph-group is a conventional group abbreviation in the art and represents a phenyl group.

[0082] In the present invention, preferably, step A) specifically includes: under a protective atmosphere, mixing the compound represented by formula (I), the p-phenylenediamine reactant, the catalyst, the ligand, the basic substance and the solvent, and heating and reacting to form the compound represented by formula (II).

[0083] In the present invention, after the reaction, the following post-treatment is preferably further carried out: solid-liquid separation, washing, drying. Among them, the solid-liquid separation method is preferably filtration. The washing is to rinse the precipitate with an organic solvent, which can be rinsed while suction filtering or can be centrifugally washed; the organic solvent is preferably the solvent used in the reaction. The drying is preferably vacuum drying. The drying temperature is preferably 80 - 100 °C; the drying time is preferably 5 - 12 h. After the above post-treatment, the solid product of the aniline pentamer represented by formula (II) is obtained.

[0084] [Regarding Step B]:

[0085] B) The compound shown in formula (II) undergoes a Boc coupling reaction with di-tert-butyl dicarbonate to form the compound shown in formula (III).

[0086] The reaction route of this step is as follows:

[0087]

[0088] In the present invention, the source of the di-tert-butyl dicarbonate (abbreviated as DIBOC, chemical formula abbreviated as (Boc) 2 O) is not particularly limited and can be a commercially available product or prepared according to known preparation methods in the art.

[0089] In the present invention, the molar ratio of the compound shown in formula (II) to di-tert-butyl dicarbonate is preferably 1:(3 - 6), specifically 1:3, 1:4, 1:5, 1:6, and more preferably 1:(4 - 5).

[0090] In the present invention, the reaction is preferably carried out in the presence of a basic substance. Among them, the basic substance includes at least one of metal compounds, organic bases, inorganic bases, and inorganic salts, preferably sodium tert-butoxide, potassium tert-butoxide, sodium amide, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, 4-dimethylaminopyridine, triethylamine, KOH, NaOH, K 2 CO 3 、Na 2 CO 3 、Cs 2 CO 3 and at least one of them, more preferably 4-dimethylaminopyridine. In the present invention, the molar ratio of the basic substance to the compound shown in formula (II) is preferably (0.05 - 5):1, specifically 0.05:1, 0.1:1, 0.25:1, 0.5:1, 0.75:1, 1:1, 2:1, 3:1, 4:1, 5:1.

[0091] In the present invention, the reaction is preferably carried out in a solvent medium. The solvent is preferably an organic solvent, more preferably at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether, and further preferably at least one of chloroform and tetrahydrofuran. In the present invention, the amount of the solvent used is preferably 3 - 10 times the mass of the compound shown in formula (II).

[0092] In the present invention, the temperature of the reaction is preferably 40 to 100 °C, specifically it can be 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C; the above temperature is more preferably 60 to 70 °C, which is also a relatively mild temperature condition. The reaction time is preferably 4 to 12 h, specifically it can be 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h. The compound shown in formula (II) undergoes a Boc coupling reaction with di-tert-butyl dicarbonate to obtain the aniline pentamer-Boc shown in formula (III).

[0093] In the present invention, after the above reaction is completed, it is preferably further subjected to the following post-treatment: solid-liquid separation, washing, and drying. Among them, the solid-liquid separation method is preferably filtration.

[0094] The washing is carried out by rinsing with an organic solvent; the organic solvent is preferably ethanol. The drying is preferably vacuum drying. The drying temperature is preferably 80 to 100 °C; the drying time is preferably 5 to 12 h. After the above post-treatment, the solid product of aniline pentamer-Boc shown in formula (III) is obtained.

[0095] [Regarding step C]:

[0096] C) The compound shown in formula (III) is deprotected and hydrogenated to obtain the diamine monomer shown in formula (IV).

[0097] In the present invention, the reaction route of this step is as follows:

[0098]

[0099] In the present invention, the Ph 2 CN-groups at both ends of the compound of formula (III) are deprotected and hydrogenated to obtain the diamine monomer shown in formula (IV).

[0100] In the present invention, the reaction of step C) is preferably carried out in the presence of a hydrogen source reagent. Including but not limited to H 2 , hydroxylamine hydrochloride, ammonium formate, sodium borohydride, etc., preferably at least one of H 2 , hydroxylamine hydrochloride, ammonium formate. In the present invention, the molar ratio of the hydrogen source reagent to the compound shown in formula (III) is preferably (3 to 10):1, more preferably (3 to 5):1.

[0101] In the present invention, when hydroxylamine hydrochloride is selected as the hydrogen source reagent, the reaction in step C) can be carried out in the presence of a basic substance. Among them, the basic substance includes at least one of organic bases and inorganic bases, preferably at least one of sodium acetate, dimethylaminopyridine, triethylamine, pyridine, KOH, and NaOH, and more preferably pyridine and triethylamine. When the basic substances are pyridine and triethylamine, the molar ratio of pyridine to triethylamine is preferably 1∶(2 - 5). In the present invention, the molar ratio of the basic substance to the compound represented by formula (Ⅲ) is preferably (10 - 20)∶1.

[0102] In the present invention, when H 2 , ammonium formate is selected as the hydrogen source reagent, the reaction in step C) can be carried out under the action of a catalyst. The catalyst is preferably at least one of palladium-containing catalysts and nickel-containing catalysts, and more preferably at least one of Pd / C catalyst and Pd(OH) 2 / C catalyst. In the present invention, the molar ratio of the catalyst to the compound represented by formula (Ⅲ) is preferably (0.05 - 0.2)∶1.

[0103] In the present invention, the reaction in step C) is preferably carried out in a solvent medium. The solvent is preferably an organic solvent, more preferably at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether, and further preferably at least one of dichloromethane, chloroform, and tetrahydrofuran. In the present invention, the amount of the solvent used is preferably 5 - 20 times the mass of the compound represented by formula (Ⅲ).

[0104] In the present invention, the reaction temperature is preferably room temperature to the boiling point of the solvent, more preferably 20 - 50 °C, that is, the reaction can occur at normal temperature / room temperature. The reaction time is preferably 1 - 6 h. After the reaction, an aniline pentamer diamine monomer represented by formula (Ⅳ) is formed.

[0105] Preferably, in the present invention, step C) specifically includes: mixing the compound represented by formula (Ⅲ), the hydrogen source reagent, the basic substance, and the solvent, and carrying out deprotection and hydrogenation reactions to form the diamine monomer represented by formula (Ⅳ).

[0106] In the present invention, when hydroxylamine hydrochloride is selected as the hydrogen source reagent, after the above reaction is completed, it is preferred to further perform the following post-treatments on the obtained reaction solution: solid-liquid separation, washing, and drying. Among them, the solid-liquid separation method is preferably filtration or centrifugal separation. The washing is carried out by rinsing with an organic solvent; the organic solvent includes but is not limited to at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether, and more preferably at least one of dichloromethane, chloroform, and tetrahydrofuran. The drying is preferably vacuum drying. The drying temperature is preferably 80-100 °C; the drying time is preferably 5-12 h. After the above post-treatments, a solid product of the aniline pentamer diamine monomer shown in formula (IV) is obtained.

[0107] In the present invention, when H 2 , ammonium formate is selected as the hydrogen source reagent, after the above reaction is completed, it is preferred to further perform the following post-treatments on the obtained reaction solution: solid-liquid separation, washing, extraction, and drying. Among them, the solid-liquid separation method is preferably filtration or centrifugal separation. The washing is carried out by rinsing with an organic solvent; the organic solvent includes but is not limited to at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether, and more preferably at least one of dichloromethane, chloroform, and tetrahydrofuran. For the extraction, a Soxhlet extractor is preferably used but not limited to it. The specific steps are to put the obtained solid into the extractor, select organic solvents such as dichloromethane, chloroform, and tetrahydrofuran, and perform heating and reflux extraction. The obtained extract is further concentrated to a solid state by a rotary evaporator. The drying is preferably vacuum drying. The drying temperature is preferably 80-100 °C; the drying time is preferably 5-12 h. After the above post-treatments, a solid product of the aniline pentamer diamine monomer shown in formula (IV) is obtained.

[0108] In the present invention, by introducing a solubilizing group into the diamine monomer, the dissolution performance of the subsequent polymer is improved, enabling the polymer to dissolve in low-boiling solvents and enhancing its processing performance. Subsequently, the solubilizing group is removed through post-treatment to improve the solvent resistance of the polymer, thus effectively solving the contradiction between processing performance and solvent resistance. After removing the solubilizing group, the main chain is transformed into a polyaniline chain segment, and the intermolecular and intramolecular hydrogen bonding and π-π interactions are enhanced, making the structure more compact, thereby endowing it with excellent solvent resistance and mechanical properties. In addition, the polyaniline oligomer chain segment also imparts excellent antistatic properties to the material.

[0109] The preparation method provided by the present invention first prepares the aniline pentamer shown in formula (II) based on the Buchwald-Hartwig cross-coupling reaction, then adds the Boc group to obtain the aniline pentamer-Boc shown in formula (III), and then removes the protecting groups at both ends by hydrogenation to obtain the aniline pentamer diamine monomer shown in formula (IV). The above preparation method has a simple synthetic route, is easy to operate, has high reaction efficiency, and a wide range of applicable reaction substrates. For the prepared aniline pentamer diamine and related intermediates, after the reaction is completed, the desired target product can be obtained by filtration and washing, without purification processes such as recrystallization, which not only saves costs but also is environmentally friendly; moreover, the product yield and purity are high, and the monomer purity can meet the requirements of polymerization.

[0110] The diamine prepared by the present invention has rich solubilizing groups, and the resin powder obtained by polymerization exhibits excellent dissolution properties and processing properties. After heat treatment, it also exhibits excellent solvent resistance, effectively solving the contradiction between processing properties and solvent resistance. In the prior art, generally only one-sided problems are solved, and it is impossible to have both processing properties and solvent resistance.

[0111] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0112] Example 1

[0113] 1. Product preparation:

[0114] A) Preparation of the compound shown in formula (II):

[0115] Under argon protection, the compound shown in formula (I) (10.55 g, 0.02 mol), p-phenylenediamine (1.08 g, 0.01 mol), the catalyst Pd(PPh 3 ) 4 (11.6 mg, 0.01 mmol) and DPEPhos (5.4 mg, 0.01 mmol), the basic substance potassium tert-butoxide (3.37 g, 0.03 mol), and the solvent toluene (243 mL) were successively added to a 500 mL reaction flask. The reaction system was stirred at 90 °C for 8 h, and then the heating was stopped. The obtained reaction solution was filtered, washed, suction-filtered, and dried to finally obtain a yellow-green solid, namely the aniline pentamer shown in formula (II) (9.4 g, yield 94%).

[0116] 1 H NMR (500 MHz, DMSO-d 6) δ 7.95 (s, 2H), 7.65 (d, J = 5 Hz, 4H), 7.53 (t, J = 5 Hz, 2H), 7.46 (t, J = 7.5 Hz, 4H), 7.32 (t, J = 2.5 Hz, 6H), 7.14 (m, 4H), 7.01 (s, 4H), 6.96 (t, J = 10 Hz, 8H), 6.88 (d, J = 10 Hz, 4H), 6.63 (d, J = 10 Hz, 4H), 1.31 (s, 18H). The 1H NMR spectrum is as shown in Figure 2 as follows.

[0117] B) Preparation of the compound shown in formula (III):

[0118] Add the aniline pentamer (9.0 g, 9 mmol) shown in formula (II) obtained in step A), di-tert-butyl dicarbonate (5.89 g, 27 mmol), the basic substance 4-dimethylaminopyridine (0.05 g, 0.45 mmol), and the solvent tetrahydrofuran (30 mL) into a 100 mL reaction flask in sequence, reflux for 4 h, and then stop heating. Then, filter, wash with ethanol, and dry to finally obtain a white powder, namely aniline pentamer - Boc shown in formula (III) (10.10 g, yield 93%).

[0119] 1H NMR (500 MHz, DMSO-d6) δ 7.65 (d, J = 7.5 Hz, 4H), 7.53 (t, J = 7.5 Hz, 2H), 7.45 (t, J = 7.5 Hz, 4H), 7.28 (m, 6H), 7.19–7.04 (m, 16H), 6.96 (d, J = 7.5 Hz, 4H), 6.65 (d, J = 10 Hz, 4H), 1.33 (d, J = 30 Hz, 36H). The 1H NMR spectrum is as shown in Figure 3 as follows.

[0120] C) Preparation of the diamine monomer shown in formula (IV):

[0121] Add the aniline pentamer - Boc (9.61 g, 8 mmol) obtained in step B), the hydrogen source reagent hydroxylamine hydrochloride (1.67 g, 24 mmol), the basic substances pyridine (6.33 g, 0.08 mol) and triethylamine (16.19 g, 0.16 mol), and the solvent dichloromethane (200 mL) into a 500 mL reaction flask, stir at room temperature for 1 h, and then stop stirring. Then, filter, wash with ethanol, and dry to finally obtain a white powder, namely aniline pentamer diamine shown in formula (IV) (6.6 g, yield 94%, purity 99.2%).

[0122] 1H NMR (500 MHz, DMSO-d6) δ 7.11 (m, 12H), 6.84 (d, J = 7.5 Hz, 4H), 6.50 (d, J = 7.5 Hz, 4H), 5.11 (s, 4H), 1.35 (d, J = 5.0 Hz, 36H). The 1H NMR spectrum is as shown in Figure 4 the following.

[0123] From the above, it can be seen that the aniline pentamer diamine monomer shown in formula (IV) was successfully prepared in the present invention, and the route is simple, the operation is convenient, the reaction is efficient, the yield reaches 94%, and the purity reaches 99.2%, which can meet the requirements of polymerization.

[0124] 2. Product testing:

[0125] (2.1) Solubility test

[0126] Preparation of soluble polyimide resin powder PI-1:

[0127] The aniline pentamer diamine shown in formula (IV) obtained in Example 1 (17.46 g, 0.02 mol) and 4,4′-hydroquinone diphthalic anhydride, i.e., 4,4′-HQDPA (8.05 g, 0.02 mol) were added to N,N′-dimethylacetamide (154 mL), and stirred at room temperature for 24 h to obtain a pale yellow viscous polyamic acid solution. Then, imidization reagents triethylamine (4.24 g, 0.042 mol) and acetic anhydride (5.10 g, 0.05 mol) were added, and stirring was continued for 5 h. Subsequently, precipitation, pulverization, filtration, ethanol rinsing, and drying were carried out in ethanol to finally obtain white powder, i.e., polyimide resin powder PI-1 (22.8 g, yield 92%).

[0128] The polyimide resin powder PI-1 was mixed with various solvents respectively to investigate its solubility in various solvents. The results show that the polymer can not only dissolve in conventional high-boiling solvents, such as N,N′-dimethylacetamide (DMAc) with a boiling point of 166 °C, N,N′-dimethylformamide (DMF) with a boiling point of 153 °C, N-methylpyrrolidone (NMP) with a boiling point of 202 °C, m-cresol with a boiling point of 203 °C, etc.; but also dissolve in a variety of low-boiling solvents, such as tetrahydrofuran (THF) with a boiling point of 66 °C, ethyl acetate (EA) with a boiling point of 77 °C, chloroform (CF) with a boiling point of 61 °C, acetone (ACE) with a boiling point of 56 °C, and methyl ethyl ketone (MEK) with a boiling point of 80 °C. The test results are shown in Table 1.

[0129] (2.2) Solvent resistance test

[0130] Preparation of solvent-resistant polyimide resin powder PI-2:

[0131] The polyimide resin powder PI-1 was vacuum-treated at a constant temperature of 250 °C for 6 h to obtain a solvent-resistant polyimide resin powder PI-2.

[0132] The polyimide resin powder PI-2 was mixed with various solvents respectively to investigate its solubility in various solvents. The test results are shown in Table 1.

[0133] Table 1: Solubility of polyimide resin powder

[0134] DMAc DMF NMP THF EA m-Cresol CF ACE MEK PI-1 (solid content 15%) ++ ++ ++ + + ++ ++ + + PI-2 (solid content 0.2%) - - - - - - - - -

[0135] Note: ++ means complete dissolution, + means partial dissolution, and - means insoluble.

[0136] It can be seen from the test results in Table 1 that the polyimide resin powder prepared by polymerizing the diamine monomer shown in formula (IV) of the present invention can not only dissolve high-boiling solvents that can conventionally dissolve polyimide, but also dissolve in a variety of low-boiling organic solvents, which is suitable for rapid prototyping and improves processability. When the polyimide resin powder is subjected to simple heat treatment or chemical treatment, the Boc group is removed from the resin, and the intermolecular and intramolecular hydrogen bond interactions and π-π interactions are enhanced, making it difficult for solvent molecules to diffuse between polymer chains, and the polymer is almost insoluble in any organic solvent. Therefore, the present invention effectively balances the problem of high solubility required during processing and solvent resistance required after forming, achieving a balance between the two.

[0137] Among them, the thermogravimetric curve of the polyimide resin powder PI-1 is as Figure 5 shown. The heat treatment process of the present invention is essentially a pyrolysis process, in which the Boc group decomposes upon heating, producing carbon dioxide and isobutene and overflowing, resulting in a decrease in mass. This process can be demonstrated by thermal analysis, as Figure 5 shown, and the materials show a stepped curve upon heating, and the formation reason of this step is the thermal decomposition of the Boc group.

[0138] The infrared spectra of the polyimide resin powders PI-1 and PI-2 are as Figure 6 shown, which confirm the structural transformation of the materials before and after heat treatment. After characterization, the resistivity of the polyimide resin powder PI-2 is about 10 7 ohm·cm, meeting the anti-static index requirements, indicating that the polyimide prepared from the diamine monomer of the present invention has a good anti-static effect.

[0139] Example 2

[0140] A) Preparation of the compound shown in formula (II):

[0141] Under argon protection, the compound shown in formula (I) (10.55 g, 0.02 mol), p-phenylenediamine (0.87 g, 0.008 mol), and the catalyst Pd(OAc) 2(4.5 mg, 0.02 mmol) and X-Phos (95 mg, 0.2 mmol), the base sodium tert-butoxide (19.22 g, 0.2 mol), and the solvent tetrahydrofuran (60 mL) were successively added to a 200 mL reaction flask. The reaction system was stirred at 60 °C for 8 h, and then the heating was stopped. The resulting reaction solution was filtered, washed, suction filtered, and dried to finally obtain a yellow-green solid, namely the aniline pentamer shown in formula (II) (7.7 g, yield 96%). The NMR results were consistent with the compound obtained in step A) of Example 1, confirming its structure.

[0142] B) Preparation of the compound shown in formula (III):

[0143] The aniline pentamer shown in formula (II) obtained in step A) (9.0 g, 9 mmol), di-tert-butyl dicarbonate (11.78 g, 54 mmol), the base triethylamine (0.91 g, 9 mmol), and the solvent dichloromethane (60 mL) were successively added to a 200 mL reaction flask. The reaction was refluxed for 12 h, and then the heating was stopped. Then, filtration, ethanol rinsing, and drying were carried out to finally obtain a white powder, namely aniline pentamer-Boc shown in formula (III) (9.82 g, yield 91%). The NMR results were consistent with the compound obtained in step B) of Example 1, confirming its structure.

[0144] C) Preparation of the diamine monomer shown in formula (IV):

[0145] The aniline pentamer-Boc obtained in step B) (9.61 g, 8 mmol), the hydrogen source reagent ammonium formate (1.67 g, 24 mmol), the catalyst 10% Pd / C (0.43 g, 0.4 mmol), and the solvent tetrahydrofuran (60 mL) were added to a 200 mL reaction flask. The mixture was stirred at 50 °C for 6 h, and then the stirring was stopped. Then, filtration, ethanol rinsing, Soxhlet extraction (the solvent was tetrahydrofuran), and drying were carried out to finally obtain a white powder, namely aniline pentamer diamine shown in formula (IV) (6.3 g, yield 91%, purity 99.4%). The NMR results were consistent with the compound obtained in step C) of Example 1, confirming its structure.

[0146] The yield of the aniline pentamer diamine shown in formula (IV) was 91% and the purity was 99.4%, which could meet the requirements of polymerization.

[0147] Example 3

[0148] A) Preparation of the compound shown in formula (II):

[0149] Under argon protection, the compound shown in formula (I) (10.55 g, 0.02 mol), p-phenylenediamine (0.97 g, 0.009 mol), the catalyst Pd 2 (dba) 3(9.2 mg, 0.01 mmol) and RuPhos (9.3 mg, 0.02 mmol), the base Cs 2 CO 3 (32.58 g, 0.1 mol), the solvent dioxane (180 mL), deionized water (20 mL) were successively added into a 500 mL reaction flask. The reaction system was stirred at 90 °C for 6 h, and then the heating was stopped. The resulting reaction solution was filtered, washed, suction filtered, and dried to finally obtain a yellow-green solid, namely the aniline pentamer shown in formula (II) (8.4 g, yield 93%). The NMR results were consistent with the compound obtained in step A) of Example 1, confirming its structure.

[0150] B) Preparation of the compound shown in formula (III):

[0151] The aniline pentamer shown in formula (II) obtained in step A) (9.0 g, 9 mmol), di-tert-butyl dicarbonate (7.86 g, 36 mmol), the base potassium carbonate (6.22 g, 45 mmol), and the solvent methanol (100 mL) were successively added into a 250 mL reaction flask, and the reaction was refluxed for 8 h, and then the heating was stopped. Then, filtration, ethanol rinsing, and drying were carried out to finally obtain a white powder, namely aniline pentamer - Boc shown in formula (III) (9.52 g, yield 88%). The NMR results were consistent with the compound obtained in step B) of Example 1, confirming its structure.

[0152] C) Preparation of the diamine monomer shown in formula (IV):

[0153] The aniline pentamer - Boc obtained in step B) (9.61 g, 8 mmol), the catalyst 10% Pd(OH) 2 / C (2.25 g, 1.6 mmol), and the solvent tetrahydrofuran (100 mL) were added into a 500 mL reaction flask, and stirred at 50 °C for 6 h under H 2 atmosphere, and then the stirring was stopped. Then, filtration, ethanol rinsing, Soxhlet extraction (the solvent was dichloromethane), and drying were carried out to finally obtain a white powder, namely aniline pentamer diamine shown in formula (IV) (6.4 g, yield 92%, purity 99.6%). The NMR results were consistent with the compound obtained in step C) of Example 1, confirming its structure.

[0154] The yield of the aniline pentamer diamine shown in formula (IV) is 92%, and the purity is 99.6%, which can meet the requirements of polymerization.

[0155] In this article, specific examples are used to elaborate on the principles and implementation modes of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A diamine monomer, characterized in that It has the structure shown in formula (IV):

2. A method for preparing the diamine monomer according to claim 1, characterized in that: The following steps are involved: A) reacting the compound represented by formula (I) with a p-phenylenediamine reactant to form a compound represented by formula (II); The p-phenylenediamine reactant is p-phenylenediamine and / or p-phenylenediamine hydrochloride; B) the compound represented by formula (II) undergoes a Boc coupling reaction with di-tert-butyl dicarbonate to form a compound represented by formula (III); C) subjecting the compound represented by formula (III) to deprotection and hydrogenation to obtain a diamine monomer represented by formula (IV); 3. The preparation method according to claim 2, characterized in that: In step A), the molar ratio of the compound represented by formula (I) to the p-phenylenediamine reactant is (2.0-2.5):

1.

4. The preparation method according to claim 2, characterized in that: In step A), the reaction temperature is 50-100°C.

5. The preparation method according to claim 2, characterized in that: In step A): The reaction is carried out under the action of a catalyst; wherein the catalyst is at least one of a metal palladium compound, a metal rhodium compound and a metal ruthenium compound; the molar ratio of the catalyst to the compound represented by formula (I) is (0.0002-0.001):1; The reaction is carried out in the presence of a ligand; wherein the ligand is a phosphine-containing compound, including trimethyl phosphine, triethyl phosphine, tripropyl phosphine, triisopropyl phosphine, tributyl phosphine, tricyclohexyl phosphine, triphenyl phosphine, triisopropyl phosphine, bis(2-diphenylphosphophenyl)ether, 1,1′-binaphthyl-2,2′-bisdiphenylphosphine, 2-dicyclohexylphosphine-2′,4′,6′-triisopropylbiphenyl, 4,5-bisdiphenylphosphine-9,9-dimethylxanthene, 2-(dicyclohexylphosphine)-3,6-dimethoxy-2′,4′,6′-tri-I-propyl-11′-biphenyl, 2-dicyclohexylphosphine-2′,6′-diisopropyl -1,1′-biphenyl, 2-di-tert-butylphosphino-2′,4′,6′-triisopropylbiphenyl, 2-(di-tert-butylphosphino)-3,6-dimethoxy-2′,4′,6′tri-1-propyl-1,1′-biphenyl, 1,1′-bis(diphenylphosphino)ferrocene, (R)-(-)-1-[(S)-2-(dicyclohexylphosphino)ferrocene]ethyldi-tert-butylphosphine, 5-di-tert-butylphosphino-1′,3′,5′-triphenyl-1′H-[1,4′]dipyrazole, N-[2-di(1-adamantane)phosphophenyl]morpholine; the molar ratio of the ligand to the catalyst is (1-10):1; The reaction is carried out in the presence of an alkaline substance; wherein the alkaline substance is at least one of sodium tert-butoxide, potassium tert-butoxide, sodium amide, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, 4-dimethylaminopyridine, triethylamine, KOH, NaOH, K2CO3, Na2CO3, and Cs2CO3; and the molar ratio of the alkaline substance to the compound represented by formula (I) is (1.5-10):1; The reaction is carried out in a solvent medium; wherein the solvent is an organic solvent, or a mixed solvent of an organic solvent and water; wherein the organic solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, toluene, and benzene; and the mass of the solvent is 5 to 20 times the mass of the compound represented by formula (I); The reaction was carried out under a protective atmosphere.

6. The preparation method according to claim 2, characterized in that: In step B), the molar ratio of the compound represented by formula (II) to di-tert-butyl dicarbonate is 1:(3-6).

7. The preparation method according to claim 2, characterized in that: In step B), the reaction temperature is 40-100°C.

8. The preparation method according to claim 2, characterized in that: In step B): The reaction is carried out in the presence of an alkaline substance; wherein the alkaline substance is at least one of sodium tert-butoxide, potassium tert-butoxide, sodium amide, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, 4-dimethylaminopyridine, triethylamine, KOH, NaOH, K2CO3, Na2CO3, and Cs2CO3; and the molar ratio of the alkaline substance to the compound represented by formula (II) is (0.05-5):1; The reaction is carried out in a solvent medium; wherein the solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether.

9. The preparation method according to claim 2, characterized in that: In step C): The hydrogen source reagent used in the hydrogenation is at least one of H2, hydroxylamine hydrochloride and ammonium formate; the molar ratio of the hydrogen source reagent to the compound represented by formula (III) is (3-10):1; The reaction in step C) is carried out in a solvent medium; wherein the solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, butanone, toluene, ethyl acetate, xylene, methanol, ethanol, and ether.

10. The preparation method according to claim 2, characterized in that: Step A) specifically comprises: under a protective atmosphere, mixing the compound represented by formula (I), a p-phenylenediamine reactant, a catalyst, a ligand, an alkaline substance and a solvent, and heating the mixture to react to form a compound represented by formula (II); Step B) specifically comprises: mixing the compound represented by formula (II), di-tert-butyl dicarbonate, an alkaline substance and a solvent, and subjecting the mixture to a reflux reaction to form a compound represented by formula (III); Step C) specifically comprises: mixing the compound represented by formula (III), a hydrogen source reagent, an alkaline substance or a catalyst, and a solvent, and performing a deprotection and hydrogenation reaction to form a diamine monomer represented by formula (IV).

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