Diamine monomer, self-repairing thermoplastic polyimide resin and preparation method

Abstract

The invention relates to the technical field of high-molecular compounds, in particular to a diamine monomer, self-repairing thermoplastic polyimide resin and a preparation method. The molecular structural formula of the diamine monomer is # imgabs0 #, in the formula, Y is one of N atoms or O atoms, and m is any integer between 1 and 5. The self-repairing thermoplastic polyimide resin prepared from the diamine monomer has a dynamic disulfide bond cross-linked structure, and compared with a structure containing a disulfide bond in a polyimide main chain, the polyimide resin has higher structural strength and better performance after being repaired; the technical problems that an existing polyimide material is poor in material self-repairing capacity and poor in mechanical property can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer compounds, in particular to a diamine monomer, a self-repairing thermoplastic polyimide resin and a preparation method thereof. Background Art

[0002] Polyimide (PI) has high thermal stability, good mechanical properties and excellent chemical properties, and is widely used in microelectronics, aerospace, energy storage, coating and other fields. At the same time, polyimide can be used as a dielectric protective layer and passivation layer, and is used in the packaging and manufacturing of important equipment and microelectronic devices. In addition, polyimide is increasingly used as a medical catheter due to its high temperature resistance, corrosion resistance, low friction coefficient and good biocompatibility.

[0003] However, after polyimide is molded into a catheter, the resulting PI catheter, as a functional component of a medical device, is not only susceptible to microscopic damage during post-processing and transportation, but also during use, when it is assembled and composited with a guidewire and other components, which can also cause some microscopic damage to the catheter itself. Therefore, it is necessary to develop polyimide materials with self-healing properties to prevent these damages from affecting the material's performance and effectiveness.

[0004] Currently, common polymer repair systems using microcapsules or supramolecular forces suffer from issues such as limited material repair times, insufficient material strength, and poor mechanical properties. Alternatively, polyimide repair can be achieved through dynamic covalent bonding technology. However, introducing too many flexible dynamic covalent bonds into the polyimide backbone reduces its structural strength, limiting its application scenarios. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention provides a novel lipoic acid-modified diamine monomer, a self-healing thermoplastic polyimide resin synthesized from this monomer, and a method for preparing the same. The thermoplastic polyimide resin provided by the present invention effectively addresses the technical issues of existing polyimide materials, such as poor self-healing ability and mechanical properties.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: A technical solution of the present invention provides a diamine monomer having a molecular structure as shown in Formula I:

[0007] Formula I In the formula, Y is a nitrogen atom or an oxygen atom, and m is any integer between 1 and 5.

[0008] Another technical solution of the present invention provides a method for preparing the above-mentioned diamine monomer, and the preparation route is as follows:

[0009] The specific steps include: S1: Add raw material 1, p-aminophenol, and an alkaline compound to a polar solvent, heat and stir. After the reaction is completed, pour the reaction solution into water, filter to obtain a solid, and wash and dry it to obtain intermediate 1; S2: Dissolve the intermediate 1, raw material 2, and organic base in dichloromethane, then slowly add the condensing agent solution dropwise to the dichloromethane solution, stir until the reaction is completed, dilute with ethyl acetate, and then wash the dilution with hydrochloric acid solution, saturated brine, and saturated sodium bicarbonate solution in sequence. The resulting solution is filtered with a desiccant and then rotary evaporated to obtain intermediate 2; S3: Dissolve the intermediate 2, thioctic acid, and an organic base in dichloromethane, then slowly add the condensing agent solution dropwise to the dichloromethane solution, stir until the reaction is completed, dilute with ethyl acetate, and then wash the diluted solution with hydrochloric acid solution, saturated brine, and saturated sodium bicarbonate solution in sequence. The resulting solution is filtered with a desiccant and then rotary evaporated to obtain a diamine monomer.

[0010] In some possible embodiments, in step S1, the raw material 1 is any one of 2,6-dichlorobenzoic acid and 2,6-difluorobenzoic acid.

[0011] In some possible embodiments, in step S1, the molar ratio of raw material 1 to p-aminophenol is 1:(1-5).

[0012] Preferably, in step S1, the molar ratio of raw material 1 to p-aminophenol is 1:(1.5-3).

[0013] In some possible embodiments, in step S1, the alkaline compound is any one of potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, and sodium hydride.

[0014] In some possible embodiments, in step S1, the molar ratio of the raw material 1 to the basic compound is 1:(1-5).

[0015] Preferably, in step S1, the molar ratio of raw material 1 to the basic compound is 1:(2-4).

[0016] In some possible embodiments, in step S1, the polar solvent is any one of DMF, DMAc, and NMP.

[0017] In some possible embodiments, in step S1, the concentration of raw material 1 in the polar solvent is 0.05-0.5 mol / L.

[0018] In some possible implementations, in step S1, the heating and stirring time is 2 to 24 hours, and the heating temperature is 80 to 150°C.

[0019] In some possible implementations, in step S1, the amount of water used is 2 to 5 times the volume of the polar solvent.

[0020] In some possible embodiments, in step S2, the raw material 2 has a molecular structure as shown in Formula II:

[0021] Formula II In the formula, Y is a nitrogen atom or an oxygen atom, and m is any integer between 1 and 5.

[0022] Illustratively, in step S2, the raw material 2 may be HOCH2CH2OH, HOCH2(CH2)2OH, HOCH2(CH2)3OH, HOCH2(CH2)4OH, HOCH2(CH2)5OH, NH2CH2CH2NH2, NH2CH2(CH2)2NH2, NH2CH2(CH2)3NH2, NH2CH2(CH2)4NH2, or NH2CH2(CH2)5NH2.

[0023] In some possible embodiments, in step S2, the molar ratio of intermediate 1 to raw material 2 is 1:(1-5).

[0024] Preferably, in step S2, the molar ratio of intermediate 1 to raw material 2 is 1:(1-3).

[0025] In some possible embodiments, in step S2, the organic base is any one of pyridine, 2,6-lutidine, 2,6-di-tert-butylpyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine, and 4-pyrrolidinylpyridine.

[0026] In some possible embodiments, in step S2, the molar ratio of the intermediate 1 to the organic base is 1:(1-5).

[0027] In some possible embodiments, in step S2, the condensing agent is any one of N,N'-diisopropylcarbodiimide (DIC), dicyclohexylcarbodiimide (DCC), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI).

[0028] In some possible embodiments, in step S2, the molar ratio of the intermediate 1 to the condensing agent is 1:(1-5).

[0029] In some possible embodiments, in step S2, the solvent of the condensing agent solution is selected from any one of DMF, DCM, DMAc, and NMP.

[0030] In some possible implementations, in step S2, the condensing agent solution is added at a rate of 1 to 2 mL / min.

[0031] In some possible implementations, in step S2, the desiccant is any one of anhydrous sodium sulfate and anhydrous magnesium sulfate.

[0032] In some possible embodiments, in step S2, the molar concentration of raw material 1 in dichloromethane is 0.01-1 mol / L.

[0033] In some possible embodiments, in step S2, the molar concentration of the raw material 1 in the solvent used for the condensing agent solution is 0.01-1 mol / L.

[0034] In some possible implementations, in step S2, the stirring reaction time is 2 to 24 hours.

[0035] In some possible embodiments, in step S2, the amount of ethyl acetate used is 1 to 10 times the volume of the reaction solution.

[0036] In some possible embodiments, in step S3, the molar ratio of lipoic acid to intermediate 2 is 1:(1-5).

[0037] Preferably, in step S3, the molar ratio of lipoic acid to intermediate 2 is 1:(1-3).

[0038] In some possible embodiments, in step S3, the organic base is any one of pyridine, 2,6-lutidine, 2,6-di-tert-butylpyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine, and 4-pyrrolidinylpyridine.

[0039] In some possible embodiments, in step S3, the molar ratio of lipoic acid to the organic base is 1:(1-5).

[0040] Preferably, in step S3, the molar ratio of thioctic acid to the organic base is 1:(1-3).

[0041] In some possible embodiments, in step S3, the condensing agent is any one of N,N'-diisopropylcarbodiimide (DIC), dicyclohexylcarbodiimide (DCC), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI).

[0042] In some possible embodiments, in step S3, the solvent of the condensing agent solution is selected from any one of DMF, DCM, DMAc, and NMP.

[0043] In some possible implementations, in step S3, the condensing agent solution is added at a rate of 1 to 2 mL / min.

[0044] In some possible embodiments, in step S3, the molar ratio of lipoic acid to the condensing agent is 1:(1-5).

[0045] Preferably, in step S3, the molar ratio of lipoic acid to the condensing agent is 1:(1-3.5).

[0046] In some possible implementations, in step S3, the desiccant is any one of anhydrous sodium sulfate and anhydrous magnesium sulfate.

[0047] In some possible embodiments, in step S3, the molar concentration of lipoic acid in dichloromethane is 0.01-1 mol / L.

[0048] In some possible embodiments, in step S3, the molar concentration of lipoic acid in the solvent used for the condensing agent solution is 0.01-1 mol / L.

[0049] In some possible implementations, in step S3, the stirring reaction time is 2 to 24 hours.

[0050] In some possible embodiments, in step S3, the amount of ethyl acetate used is 1 to 10 times the volume of the reaction solution.

[0051] The present invention also provides a method for preparing a self-repairing thermoplastic polyimide resin, comprising the following steps: (1) At room temperature, the dianhydride monomer is mixed with a polar solvent until it is completely dissolved; then the temperature is lowered and replaced with an inert gas, and the diamine monomer is added and stirred at low temperature to prepare a polyamic acid solution; (2) adding an organic base to the polyamic acid solution obtained in step (1), and then slowly adding a dehydrating agent dropwise, heating and stirring after the addition is completed, and slowly adding the obtained solution to an alcohol solvent after the reaction is completed to precipitate a precipitate; obtaining a resin powder by vacuum filtration, and then washing, filtering and drying the resin powder with an alcohol solvent to obtain a self-healing thermoplastic polyimide resin.

[0052] In some possible embodiments, in step (1), the diamine monomer is the above-mentioned diamine monomer or a diamine monomer prepared by the preparation method in any of the above-mentioned schemes.

[0053] In some possible embodiments, in step (1), the dianhydride monomer is an aromatic dianhydride having any one of the structures shown in the following formulas A1 to A16:

[0054] .

[0055] In some possible embodiments, in step (1), the molar ratio of the diamine monomer to the dianhydride monomer is 1:(1.05-2).

[0056] Preferably, in step (1), the molar ratio of the diamine monomer to the dianhydride monomer is 1:(1-1.5).

[0057] In some possible embodiments, in step (1), the polar solvent is any one or more of DMF, DMAc, NMP, and DMSO.

[0058] In some possible embodiments, in step (1), the molar concentration of the dianhydride monomer in the polar solvent is 0.01-0.5 mol / L.

[0059] In some possible embodiments, in step (1), the inert gas is either argon or nitrogen.

[0060] In some possible implementations, in step (1), the solid content of the polyamic acid solution is ≥5%.

[0061] In some possible embodiments, in step (1), the low-temperature stirring temperature is ≤5°C, and the low-temperature stirring time is 2 to 24 hours.

[0062] In some possible embodiments, in step (2), the organic base is any one or more of triethylamine, ethylenediamine, diisopropylethylamine, diethylamine, pyridine, 2,6-lutidine, 2,4,6-trimethylpyridine, 2,6-di-tert-butylpyridine, 4-dimethylaminopyridine, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0063] In some possible embodiments, in step (2), the dehydrating agent is any one or more of acetic anhydride, propionic anhydride, acetyl chloride, dicyclohexylcarboximide, trifluoroacetic anhydride and thionyl chloride.

[0064] In some possible embodiments, in step (2), the molar ratio of the organic base to the dehydrating agent is 1:(1-4).

[0065] Preferably, in step (2), the molar ratio of the organic base to the dehydrating agent is 1:(1.5-3).

[0066] In some possible embodiments, in step (2), the molar ratio of the dehydrating agent to the diamine monomer is (1-8):1.

[0067] Preferably, in step (2), the molar ratio of the dehydrating agent to the diamine monomer is (1.5-4):1.

[0068] In some possible embodiments, in step (2), the dehydrating agent is added at a rate of 1 to 2 mL / min.

[0069] In some possible embodiments, in step (2), the alcohol solvent is one or more of methanol, ethanol, propanol, isopropanol, hexafluoroisopropanol, butanol, tert-butanol, and acetone.

[0070] In some possible embodiments, in step (2), the amount of the alcohol solvent used is 5 to 50 times the volume of the polar solvent.

[0071] In some possible embodiments, in step (2), the temperature of heating and stirring is 65-150° C., and the heating and stirring time is 2-24 hours; The present invention also provides a self-repairing thermoplastic polyimide resin prepared by the preparation method of any of the above technical solutions, having a molecular structure as shown in Formula III:

[0072] Formula III In Formula III, Y is a nitrogen atom or an oxygen atom, m is any integer between 1 and 5, n ≥ 5, x ≥ 5. Preferably, n ≥ 50, x ≥ 50; more preferably, n ≥ 100, x ≥ 100.

[0073] The Ar portion in Formula III has any one of the structures shown in the following formulas B1 to B16: .

[0074] The present invention has the following beneficial effects: the present invention introduces thioctic acid ester or thioctic acid amide into the diamine monomer structure to modify the molecular structure, and uses the above-mentioned diamine monomer containing thioctic acid ester or thioctic acid amide and aromatic dianhydride as starting materials to prepare a self-repairing thermoplastic polyimide resin by a chemical imide method in a polar solvent. The polyimide resin provided by the present invention has a cross-linked structure with dynamic disulfide bonds. Compared with the structure containing disulfide bonds in the PI main chain, it has better structural strength and mechanical properties, excellent self-repairing properties, and extends the service life of the polyimide product. The self-repairing properties of the disulfide bonds can effectively repair some damage caused to the polyimide product during the production, manufacturing, transportation, assembly, use, etc., thereby ensuring product performance and use effect. In particular, when used as a medical catheter, it can automatically repair microscopic damage caused by post-processing, transportation, assembly, use, etc., ensuring that the use effect of the product is not affected. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0075] Figure 1 Schematic diagram of the self-repairing process of polyimide in Example 1 of the present invention; Figure 2 Schematic diagram of the self-repairing process of polyimide in Example 2 of the present invention; Figure 3 Schematic diagram of the self-repairing process of polyimide in Example 3 of the present invention; Figure 4 Schematic diagram of the self-repairing process of polyimide in Example 4 of the present invention; Figure 5 This is a diagram of the self-repair test process of the polyimide prepared in Comparative Example 1 of the present invention; Figure 6 This is a diagram of the self-healing test process of the polyimide prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0076] To make the purpose, technical solutions and advantages of the present invention more clear, the following will be described in conjunction with the accompanying drawings by specific specific embodiments to illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiments, it does not mean that the features of this invention are limited to these embodiments. Unless otherwise specified, the raw materials used in the following examples are all common commercially available products, and the reagents are analytically pure reagents.

[0077] The present invention provides a lipoic acid-modified diamine monomer having a molecular structure as shown in Formula I:

[0078] Formula I In the formula, Y is a nitrogen atom or an oxygen atom, and m is any integer between 1 and 5.

[0079] The synthetic route of the above-mentioned lipoic acid-modified diamine monomer is as follows:

[0080] The preparation method of the lipoic acid-modified diamine monomer specifically comprises the following steps: S1: Add raw material 1, p-aminophenol, and an alkaline compound to a polar solvent and stir at 80-150°C for 2-24 hours. After the reaction is completed, pour the reaction solution into water, filter to obtain a solid, and wash and dry it to obtain intermediate 1; S2: Dissolve the intermediate 1, raw material 2, and organic base in dichloromethane, then slowly add the condensing agent solution dropwise to the dichloromethane solution and stir for 2-24 hours. After the reaction is completed, dilute with ethyl acetate, and then wash the dilution with hydrochloric acid solution, saturated brine, and saturated sodium bicarbonate solution in sequence. The resulting solution is filtered with a desiccant and then rotary evaporated to obtain intermediate 2; In some embodiments, raw material 1 is any one of 2,6-dichlorobenzoic acid and 2,6-difluorobenzoic acid; In some embodiments, the raw material 2 has a molecular structure as shown in Formula II:

[0081] Formula II In Formula II, Y is one of a N atom or an O atom, and m is any integer between 1 and 5; S3: Dissolve the intermediate 2, thioctic acid, and organic base in dichloromethane, then slowly add the condensing agent solution dropwise to the dichloromethane solution and stir for 2 to 24 hours. After the reaction is completed, dilute with ethyl acetate, and then wash the dilution with hydrochloric acid solution, saturated brine, and saturated sodium bicarbonate solution in sequence. The resulting solution is filtered with a desiccant and then rotary evaporated to obtain a diamine monomer.

[0082] In some embodiments, the components and amounts are as follows: In step S1: The molar ratio of raw material 1 to p-aminophenol is 1:(1-5), preferably 1:(1.5-3); The alkaline compound is any one of potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, and sodium hydride.

[0083] The molar ratio of the raw material 1 to the basic compound is 1:(1-5), preferably 1:(2-4).

[0084] The polar solvent used was any one of DMF, DMAc, and NMP.

[0085] The amount of water used is 2 to 5 times the volume of the polar solvent.

[0086] In step S2: The molar ratio of intermediate 1 to raw material 2 is 1:(1-5), preferably 1:(1-3); The organic base is any one of pyridine, 2,6-lutidine, 2,6-di-tert-butylpyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine and 4-pyrrolidinylpyridine.

[0087] The molar ratio of intermediate 1 to the organic base is 1:(1~5).

[0088] The condensation agent is any one of N,N'-diisopropylcarbodiimide (DIC), dicyclohexylcarbodiimide (DCC), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI).

[0089] The molar ratio of the intermediate 1 to the condensing agent is 1:(1~5).

[0090] The desiccant may be any one of anhydrous sodium sulfate and anhydrous magnesium sulfate.

[0091] The molar concentration of raw material 1 in dichloromethane is 0.01~1 mol / L.

[0092] The solvent of the condensing agent solution is selected from any one of DMF, DCM, DMAc and NMP.

[0093] The dropping speed of the condensing agent solution is 1~2mL / min.

[0094] The molar concentration of the raw material 1 in the solvent used for the condensing agent solution is 0.01 to 1 mol / L.

[0095] The amount of ethyl acetate used is 1 to 10 times the volume of the reaction solution.

[0096] In step S3: The molar ratio of lipoic acid to intermediate 2 is 1:(1-5), preferably 1:(1-3).

[0097] The organic base is any one of pyridine, 2,6-lutidine, 2,6-di-tert-butylpyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine and 4-pyrrolidinylpyridine.

[0098] The molar ratio of lipoic acid to the organic base is 1:(1-5), preferably 1:(1-3); The condensation agent is any one of N,N'-diisopropylcarbodiimide (DIC), dicyclohexylcarbodiimide (DCC), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI).

[0099] The molar ratio of lipoic acid to the condensing agent is 1:(1-5), preferably 1:(1-3.5).

[0100] The desiccant may be any one of anhydrous sodium sulfate and anhydrous magnesium sulfate.

[0101] The molar concentration of lipoic acid in dichloromethane is 0.01~1 mol / L.

[0102] The solvent of the condensing agent solution is selected from any one of DMF, DCM, DMAc and NMP.

[0103] The dropping speed of the condensing agent solution is 1~2mL / min.

[0104] The molar concentration of lipoic acid in the solvent used in the condensing agent solution is 0.01~1 mol / L.

[0105] The amount of ethyl acetate used is 1 to 10 times the volume of the reaction solution.

[0106] The present invention also provides a self-repairing thermoplastic polyimide resin prepared using the above-mentioned lipoic acid-modified diamine monomer, which has a molecular structure as shown in Formula III:

[0107] Formula III In the formula, Y is a nitrogen atom or an oxygen atom, m is any integer between 1 and 5, n ≥ 5, x ≥ 5. Preferably, n ≥ 50, x ≥ 50; more preferably, n ≥ 100, x ≥ 100.

[0108] The Ar portion of the above formula has any one of the structures shown in the following formulas B1 to B16:

[0109] The preparation method of the self-repairing thermoplastic polyimide resin comprises the following steps: (1) At room temperature, the dianhydride monomer is mixed with a polar solvent until completely dissolved; then the temperature is lowered and replaced with an inert gas. After the system stabilizes and reaches a set low temperature environment (temperature ≤ 5°C), the above-mentioned diamine monomer is slowly added under an inert gas atmosphere and stirred at low temperature for 2 to 24 hours. The end-capping agent is added and the reaction is continued for 2 hours to obtain a polyamic acid solution; (2) Adding an organic base to the polyamic acid solution obtained in step (1) and then adding a dehydrating agent dropwise, heating to 65-150° C. and stirring for 2-24 hours after the addition is completed, slowly adding the obtained solution to an alcohol solvent to precipitate a precipitate; obtaining a resin powder by vacuum filtration, and then washing, filtering and drying the resin powder with an alcohol solvent to obtain a self-healing thermoplastic polyimide resin.

[0110] In some embodiments, the dianhydride monomer is an aromatic dianhydride having any one of the structures shown in the following formulas A1 to A16:

[0111]

[0112] In some embodiments, in step (1), the molar ratio of the diamine monomer to the dianhydride monomer is 1:(1.05-2), preferably 1:(1-1.5).

[0113] In some embodiments, in step (1), the polar solvent is any one or more of DMF, DMAc, NMP, and DMSO.

[0114] In some embodiments, the molar concentration of the dianhydride monomer in the polar solvent is 0.01-0.5 mol / L.

[0115] In some embodiments, in step (1), the inert gas is either argon or nitrogen.

[0116] In some embodiments, in step (1), the end-capping agent is phthalic anhydride, and the amount of the end-capping agent used is 15-25% by weight of the diamine monomer. Preferably, the amount of the end-capping agent used is 20% by weight of the diamine monomer.

[0117] In some embodiments, in step (2), the organic base is any one or more of triethylamine, ethylenediamine, diisopropylethylamine, diethylamine, pyridine, 2,6-lutidine, 2,4,6-trimethylpyridine, 2,6-di-tert-butylpyridine, 4-dimethylaminopyridine, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0118] In some embodiments, in step (2), the dehydrating agent is any one or more of acetic anhydride, propionic anhydride, acetyl chloride, dicyclohexylcarboximide, trifluoroacetic anhydride and thionyl chloride.

[0119] In some embodiments, in step (2), the molar ratio of the organic base to the dehydrating agent is 1:(1-4), preferably 1:(1.5-3).

[0120] In some embodiments, in step (2), the molar ratio of the dehydrating agent to the diamine monomer is (1-8):1, preferably (1.5-4):1.

[0121] In some embodiments, in step (2), the dehydrating agent is added at a rate of 1 to 2 mL / min.

[0122] In some embodiments, in step (2), the alcohol solvent is one or more of methanol, ethanol, propanol, isopropanol, hexafluoroisopropanol, butanol, tert-butanol, and acetone, and the amount of the alcohol solvent used is 5 to 50 times the volume of the reaction solution.

[0123] Preparation Example 1 This preparation example provides a diamine monomer, which is a 1,3-diaryl ether diamine modified by lipoic acid ester linked by ethylene glycol, and its molecular structure is:

[0124] The synthetic route of the above-mentioned diamine monomer is as follows:

[0125] The specific synthesis steps are as follows: S1. Add 1.91 g (10 mmol) of 2,6-dichlorobenzoic acid (CAS No.: 50-30-6), 1.31 g (12 mmol) of p-aminophenol (CAS No.: 123-30-8), and 1.2 g (30 mmol) of NaOH to 100 mL of NMP and stir at 120°C for 12 h. After the reaction, filter the reaction solution through diatomaceous earth and silica gel, pour it into a large amount of water, filter the solid, wash it, and dry it to obtain Intermediate 1. The molar ratio of 2,6-dichlorobenzoic acid to p-aminophenol was calculated to be 1:1.2; the molar ratio of 2,6-dichlorobenzoic acid to NaOH was 1:3.

[0126] S2. Dissolve 3.36 g (10 mmol) of intermediate 1, 1.24 g (20 mmol) of ethylene glycol, and 1.47 g (12 mmol) of 4-dimethylaminopyridine in 70 mL of dichloromethane. Add 50 mL of a DMF solution containing 2.3 g (12 mmol) of EDCI dropwise at a rate of 1.5 mL / min and stir for 16 h. After the reaction, dilute with 200 mL of ethyl acetate and wash with 100 mL of dilute hydrochloric acid, 100 mL of saturated brine, and 100 mL of saturated sodium bicarbonate, respectively. The resulting solution is dried over anhydrous magnesium sulfate, filtered, and rotary evaporated to yield intermediate 2. The calculated molar ratios of intermediate 1 to ethylene glycol are 1:2; the molar ratios of intermediate 1 to 4-dimethylaminopyridine are 1:1.2; and the molar ratios of intermediate 1 to EDCI are 1:1.2.

[0127] S3. Dissolve 2.06 g (10 mmol) of lipoic acid, 4.56 g (12 mmol) of intermediate 2, and 1.47 g (12 mmol) of 4-dimethylaminopyridine in 70 mL of dichloromethane. Add 50 mL of a DMF solution containing 2.3 g (12 mmol) of EDCI dropwise to the reaction mixture at a rate of 1.5 mL / min and stir for 16 h. After the reaction, dilute with 200 mL of ethyl acetate and wash with 100 mL of dilute hydrochloric acid, 100 mL of saturated brine, and 100 mL of saturated sodium bicarbonate, respectively. The resulting solution is dried over anhydrous magnesium sulfate, filtered, and then rotary evaporated to obtain the diamine monomer. The calculated molar ratios of lipoic acid to intermediate 2 are 1:1.2, 1:1.21, and 1:1.2.

[0128] The NMR data are: 1H NMR (500 MHz, Chloroform-d) δ 7.41 (t, J = 7.5 Hz, 1H), 6.82 (d, J= 7.5 Hz, 2H), 6.75 – 6.68 (m, 4H), 6.64 – 6.58 (m, 4H), 5.28 (ddd, J = 12.4,10.7, 1.9 Hz, 1H), 5.08 (ddd, J = 12.6, 10.8, 1.9 Hz, 1H), 3.87 (ddt, J =12.3, 10.7, 1.5 Hz, 2H), 2.66 – 2.55 (m, 2H), 2.49 (dt, J = 12.6, 7.1 Hz,1H), 2.34 (p, J = 7.0 Hz, 1H), 2.19 – 2.07 (m, 1H), 2.02 – 1.92 (m, 2H), 1.83– 1.69 (m, 2H), 1.51 (ddt, J = 12.8, 6.8, 3.3 Hz, 1H), 1.31 (tdd, J = 14.3, 8.2, 2.6 Hz, 2H), 0.99 (dtd, J = 13.3, 11.4, 10.5, 3.1 Hz, 1H).

[0129] Preparation Example 2 This comparative example provides a diamine monomer, specifically a 1,3-diaryl ether diamine modified with lipoic acid amide linked by propylene diamine, and its molecular structure is:

[0130] The synthetic route of the above-mentioned diamine monomer is as follows:

[0131] The specific synthesis steps are as follows: S1. Add 1.91 g (10 mmol) of 2,6-dichlorobenzoic acid (CAS No.: 50-30-6), 1.31 g (12 mmol) of p-aminophenol (CAS No.: 123-30-8), and 1.2 g (30 mmol) of NaOH to 100 mL of NMP and stir at 120°C for 12 h. After the reaction, filter the reaction solution through diatomaceous earth and silica gel, pour it into a large amount of water, filter the solid, wash it, and dry it to obtain Intermediate 1. The molar ratio of 2,6-dichlorobenzoic acid to p-aminophenol was calculated to be 1:1.2; the molar ratio of 2,6-dichlorobenzoic acid to NaOH was 1:3.

[0132] S2. Dissolve 3.36 g (10 mmol) of intermediate 1, 1.48 g (20 mmol) of propylenediamine, and 1.47 g (12 mmol) of 4-dimethylaminopyridine in 70 mL of dichloromethane. Add 50 mL of a DMF solution containing 2.3 g (12 mmol) of EDCI dropwise at a rate of 1.5 mL / min and stir for 16 h. After the reaction, dilute with 200 mL of ethyl acetate and wash with 100 mL of dilute hydrochloric acid, 100 mL of saturated brine, and 100 mL of saturated sodium bicarbonate, respectively. The resulting solution is dried over anhydrous magnesium sulfate, filtered, and rotary evaporated to yield intermediate 2. The calculated molar ratios of intermediate 1 to ethylene glycol are 1:2; the molar ratios of intermediate 1 to 4-dimethylaminopyridine are 1:1.2; and the molar ratios of intermediate 1 to EDCI are 1:1.2.

[0133] S3. Dissolve 2.06 g (10 mmol) of lipoic acid, 4.7 g (12 mmol) of intermediate 2, and 1.47 g (12 mmol) of 4-dimethylaminopyridine in 70 mL of dichloromethane. Add 50 mL of a DMF solution containing 2.3 g (12 mmol) of EDCI dropwise to the reaction mixture at a rate of 1.5 mL / min and stir for 16 h. After the reaction, dilute with 200 mL of ethyl acetate and wash with 100 mL of dilute hydrochloric acid, 100 mL of saturated brine, and 100 mL of saturated sodium bicarbonate, respectively. The resulting solution is dried over anhydrous magnesium sulfate, filtered, and then rotary evaporated to obtain the diamine monomer. The calculated molar ratio of lipoic acid to intermediate 2 is 1:1.78; the molar ratio of lipoic acid to 4-dimethylaminopyridine is 1:1.21; and the molar ratio of lipoic acid to EDCI is 1:1.2.

[0134] Example 1 This embodiment provides a self-repairing thermoplastic polyimide resin, the molecular structure of which is:

[0135] The specific synthesis steps are as follows: (1) At room temperature, 2.398 g (11 mmol) of pyromellitic dianhydride was mixed with 100 mL of NMP until completely dissolved. Subsequently, the temperature was lowered and argon was replaced. The reaction solution was monitored by a thermometer. After the system temperature reached -5°C, 5.68 g (10 mmol) of the diamine monomer provided in Preparation Example 1 was slowly added under an inert gas atmosphere. After stirring at low temperature for 12 h, 1.14 g of phthalic anhydride as a capping agent was added and the reaction was continued for 2 h to obtain a polyamic acid solution. The molar ratio of diamine to dianhydride was calculated to be 1:1.

[0136] (2) 0.8 mL (10 mmol) of pyridine was added to the polyamic acid solution prepared in step (1), and then 1.88 mL (20 mmol) of acetic anhydride was slowly added dropwise at a rate of 1.5 mL / min. After the addition was completed, the temperature was raised to 85 °C and stirred for 16 h. After the reaction was completed, the obtained light yellow solution was added to 250 mL of rapidly stirred ethanol solvent, and a light yellow precipitate was immediately precipitated. A light yellow resin powder was obtained by vacuum filtration, and the light yellow powder was then washed with ethanol, filtered, and dried to obtain a self-healing thermoplastic polyimide resin. Calculation showed that the molar ratio of pyridine to acetic anhydride was 1:2; the molar ratio of acetic anhydride to diamine monomer was 2:1.

[0137] The NMR data are: 1H NMR (500 MHz, Chloroform-d) δ 8.43 (s, 2H), 7.67 – 7.61 (m, 2H), 7.36 (d, J = 1.9 Hz, 2H), 7.33 – 7.27 (m, 2H), 6.97 – 6.92 (m, 2H), 6.87 (t,J = 2.0 Hz, 1H), 6.70 – 6.62 (m, 2H), 4.49 (d, J = 2.4 Hz, 4H), 2.60 (t, J =7.0 Hz, 1H), 2.48 (t, J = 7.1 Hz, 1H), 2.40 – 2.30 (m, 3H), 2.08 (q, J = 7.1Hz, 1H), 1.76 (q, J = 7.0 Hz, 1H), 1.72 – 1.54 (m, 3H), 1.28 (dq, J = 23.3,7.0 Hz, 2H), 1.19 (p, J = 7.1 Hz, 1H). Example 2 This embodiment provides a self-repairing thermoplastic polyimide resin, the molecular structure of which is:

[0138] The specific synthesis steps are as follows: (1) At room temperature, 2.398 g (11 mmol) of pyromellitic dianhydride was mixed with 100 mL of NMP until completely dissolved. The temperature was then lowered and the atmosphere was replaced with argon. The reaction solution was monitored with a thermometer. After the system temperature reached -5°C, 5.8 g (10 mmol) of the diamine monomer provided in Preparation Example 2 was slowly added under an inert gas atmosphere. After stirring at low temperature for 12 h, 1.16 g of phthalic anhydride as a capping agent was added and the reaction was continued for 2 h to obtain a polyamic acid solution. The molar ratio of diamine to dianhydride was calculated to be 1:1.

[0139] (2) Add 0.8 mL (10 mmol) of pyridine to the polyamic acid solution prepared in step (1), and then slowly add 1.88 mL (20 mmol) of acetic anhydride at a rate of 1.5 mL / min. After the addition is completed, heat to 85°C and stir for 16 h. The color of the solution changes from transparent to light yellow. Add the obtained light yellow solution to 250 mL of rapidly stirred ethanol solvent, and a light yellow precipitate will immediately precipitate. The light yellow resin powder is obtained by vacuum filtration, and then the light yellow powder is washed with ethanol, filtered and dried to obtain a self-healing thermoplastic polyimide resin. According to calculation, the molar ratio of pyridine to acetic anhydride is 1:2; the molar ratio of acetic anhydride to diamine monomer is 2:1.

[0140] Example 3 This embodiment provides a self-repairing thermoplastic polyimide resin, the molecular structure of which is:

[0141] The specific synthesis steps are as follows: (1) At room temperature, 3.54 g (11 mmol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) was mixed with 100 mL of NMP until completely dissolved. The mixture was then cooled and replaced with argon. The reaction solution was monitored by a thermometer. After the system temperature reached -5°C, 5.68 g (10 mmol) of the diamine monomer provided in Preparation Example 1 was slowly added under an inert gas atmosphere. After stirring at low temperature for 12 h, 1.14 g of phthalic anhydride as a capping agent was added and the reaction was continued for 2 h to obtain a polyamic acid solution. The molar ratio of diamine to dianhydride was calculated to be 1:1.

[0142] (2) Add 0.8 mL (10 mmol) of pyridine to the polyamic acid solution prepared in step (1), and then slowly add 1.88 mL (20 mmol) of acetic anhydride at a rate of 1.5 mL / min. After the addition is completed, heat the mixture to 85°C and stir for 16 h. The color of the solution changes from transparent to light yellow. Add the obtained light yellow solution to 250 mL of rapidly stirred ethanol solvent, and a light yellow precipitate will immediately precipitate. The light yellow resin powder is obtained by vacuum filtration, and then the light yellow powder is washed with ethanol, filtered and dried to obtain a self-healing thermoplastic polyimide resin. According to calculation, the molar ratio of pyridine to acetic anhydride is 1:2; the molar ratio of acetic anhydride to diamine monomer is 2:1.

[0143] Example 4 This embodiment provides a self-repairing thermoplastic polyimide resin, the molecular structure of which is:

[0144] The specific synthesis steps are as follows: (1) At room temperature, 3.41 g (11 mmol) of 4,4'-oxydiphthalic anhydride was mixed with 100 mL of NMP until completely dissolved. The mixture was then cooled and replaced with argon. The reaction solution was monitored by a thermometer. After the system temperature reached -5°C, 5.68 g (10 mmol) of the diamine monomer provided in Preparation Example 1 was slowly added under an inert gas atmosphere. After stirring at low temperature for 12 h, 1.14 g of phthalic anhydride as a capping agent was added and the reaction was continued for 2 h to obtain a polyamic acid solution. The molar ratio of diamine to dianhydride was calculated to be 1:1.

[0145] (2) Add 0.8 mL (10 mmol) of pyridine to the polyamic acid solution prepared in step (1), and then slowly add 1.88 mL (20 mmol) of acetic anhydride at a rate of 1.5 mL / min. After the addition is completed, heat to 85°C and stir for 16 h. The color of the solution changes from transparent to light yellow. Add the obtained light yellow solution to 250 mL of rapidly stirred ethanol solvent, and a light yellow precipitate will immediately precipitate. The light yellow resin powder is obtained by vacuum filtration, and then the light yellow powder is washed with ethanol, filtered and dried to obtain a thermoplastic polyimide resin. According to calculation, the molar ratio of pyridine to acetic anhydride is 1:2; the molar ratio of acetic anhydride to diamine monomer is 2:1.

[0146] Comparative Example 1 This comparative example 1 provides a thermoplastic polyimide, the molecular structure of which is:

[0147] The preparation method of the thermoplastic polyimide resin in this comparative example is as follows: (1) At room temperature, 2.398 g (11 mmol) of pyromellitic dianhydride was mixed with 100 mL of NMP until completely dissolved. The mixture was then cooled and replaced with argon. The reaction solution was monitored by a thermometer. When the system temperature reached -5°C, 2.92 g (10 mmol) of 1,3-bis(4'-aminophenoxy)benzene (CAS No.: 2479-46-1) was slowly added under an inert gas atmosphere. After stirring at low temperature for 12 h, 1.14 g of phthalic anhydride as a capping agent was added and the reaction was continued for 2 h to obtain a polyamic acid solution. The molar ratio of 1,3-bis(4'-aminophenoxy)benzene to pyromellitic dianhydride was calculated to be 1:1.

[0148] (2) Add 0.8 mL (10 mmol) of pyridine to the polyamic acid solution prepared in step (1), and then slowly add 1.88 mL (20 mmol) of dehydrating agent acetic anhydride at a rate of 1.5 mL / min. After the addition is completed, heat to 85 °C and stir for 16 hours. The solution turns from transparent to light yellow. Add the obtained light yellow solution to 250 mL of rapidly stirred ethanol solvent, and a light yellow precipitate immediately precipitates. The light yellow resin powder is obtained by vacuum filtration. Finally, the light yellow powder is further washed with ethanol, filtered and dried to obtain a thermoplastic polyimide resin. According to calculation, the molar ratio of pyridine to acetic anhydride is 1:2; the molar ratio of acetic anhydride to diamine monomer is 2:1.

[0149] Comparative Example 2 This comparative example 2 provides a thermoplastic polyimide, the molecular structure of which is:

[0150] The synthesis method of the thermoplastic polyimide resin of this structure is as follows: (1) At room temperature, 3.54 g (11 mmol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride was mixed with 100 mL of NMP until completely dissolved. The mixture was then cooled and replaced with argon. The reaction solution was monitored by a thermometer. After the system temperature reached -5°C, 2.92 g (10 mmol) of 1,3-bis(4'-aminophenoxy)benzene (CAS No.: 2479-46-1) was slowly added under an inert gas atmosphere. After stirring at low temperature for 12 h, 1.14 g of phthalic anhydride as a capping agent was added and the reaction was continued for 2 h to obtain a polyamic acid solution. The molar ratio of 1,3-bis(4'-aminophenoxy)benzene to 3,3',4,4'-benzophenone tetracarboxylic dianhydride was calculated to be 1:1.

[0151] (2) Add 0.8 mL (10 mmol) of pyridine to the polyamic acid solution prepared in step (1), and then slowly add 1.88 mL (20 mmol) of dehydrating agent acetic anhydride at a rate of 1.5 mL / min. After the addition is completed, heat to 85 °C and stir for 16 h, and the solution turns from transparent to light yellow. Add the obtained light yellow solution to 250 mL of rapidly stirred ethanol solvent, and a light yellow precipitate will immediately precipitate. The light yellow resin powder is obtained by vacuum filtration, and finally the light yellow powder is further washed with ethanol, filtered and dried to obtain a self-healing thermoplastic polyimide resin. According to calculation, the molar ratio of pyridine to acetic anhydride is 1:2; the molar ratio of acetic anhydride to diamine monomer is 2:1.

[0152] Experimental data Self-healing performance test method: use a blade to scratch the thermoplastic polyimide resin film obtained in Examples 1 to 4, heat it continuously at 60° C., place it under an optical microscope, and track the scratch healing state of the sample at different heating times.

[0153] from Figures 1 to 4 It can be seen that the knife scratches of the thermoplastic polyimide resins obtained in Examples 1 to 4 have achieved a certain degree of healing at 60°C for 3 hours. When the time is extended to 12 hours, the knife scratches of the films of each example have been basically repaired. It can be seen that the thermoplastic polyimide resin films prepared by the present invention have good self-healing properties. Figure 4 and Figure 5 It can be seen that the ordinary polyimide materials in Comparative Examples 1-2 did not completely repair the shear marks after being heated for the same time and temperature as in Examples 1-4, and did not have the self-repairing function.

[0154] Mechanical properties: The polyimide resin materials prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were respectively tested for tensile strength and elongation at break according to standard GB / T1040.2-2022, and for flexural strength according to standard GB / T9341-2008. The test results are shown in Table 1 below.

[0155] Table 1 Mechanical properties of polyimide resin

[0156] As can be seen from Table 1 above, the polyimide resin prepared in the present invention not only has excellent self-healing properties, but also has good mechanical properties.

[0157] Although the preferred embodiments of the present invention have been disclosed above, they are not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A diamine monomer, characterized in that It has a molecular structure as shown in Formula I: Formula I In the formula, Y is a N atom or an O atom, and m is any integer between 1 and 5.

2. A method for preparing a diamine monomer as claimed in claim 1, characterized in that: The steps include: S1: Add raw material 1, p-aminophenol and alkaline compound into a polar solvent, heat and stir, and after the reaction is completed, filter to obtain a solid, wash and dry it to obtain intermediate 1; The raw material 1 is any one of 2,6-dichlorobenzoic acid and 2,6-difluorobenzoic acid; S2: Dissolve the intermediate 1, raw material 2 and organic base in dichloromethane, then slowly drop the condensing agent solution into the dichloromethane solution, stir until the reaction is completed, dilute with ethyl acetate, and then wash the dilution with hydrochloric acid solution, saturated brine and saturated sodium bicarbonate solution in sequence. The obtained solution is filtered with a desiccant and then rotary evaporated to obtain intermediate 2; The raw material 2 has a molecular structure as shown in Formula II: Formula II In the formula, Y is one of a N atom or an O atom, and m is any integer between 1 and 5; S3: Dissolve the intermediate 2, thioctic acid and an organic base in dichloromethane, then slowly drop the condensing agent solution into the dichloromethane solution, stir until the reaction is completed, dilute with ethyl acetate, and then wash the diluted solution with hydrochloric acid solution, saturated brine and saturated sodium bicarbonate solution in sequence. Filter the obtained solution with a desiccant and then perform rotary evaporation to obtain the diamine monomer.

3. The preparation method according to claim 2, characterized in that: In step S1, the alkaline compound is any one of potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, and sodium hydride; The molar ratio of the raw material 1 to p-aminophenol is 1:(1-5); The molar ratio of the raw material 1 to the alkaline compound is 1:(1-5).

4. The preparation method according to claim 2, characterized in that: In step S2 and step S3, the organic base is any one of pyridine, 2,6-lutidine, 2,6-di-tert-butylpyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine, and 4-pyrrolidinylpyridine; The condensing agent is any one of N,N'-diisopropylcarbodiimide, dicyclohexylcarbodiimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. The solvent of the condensing agent solution is selected from any one of DMF, DCM, DMAc and NMP.

5. The preparation method according to claim 2, characterized in that: In step S2: The molar ratio of the intermediate 1 to the raw material 2 is 1:(1-5); The molar ratio of the intermediate 1 to the organic base is 1:(1-5); The molar ratio of the intermediate 1 to the condensing agent is 1:(1-5).

6. The preparation method according to claim 2, characterized in that: In step S3: The molar ratio of lipoic acid to intermediate 2 is 1:(1-5); The molar ratio of lipoic acid to organic base is 1:(1-5); The molar ratio of lipoic acid to the condensing agent is 1:(1-5).

7. A method for preparing a self-repairing thermoplastic polyimide resin, characterized in that: The steps include: (1) At room temperature, the dianhydride monomer is mixed with a polar solvent until it is completely dissolved; then the temperature is lowered and replaced with an inert gas, and the diamine monomer is added and stirred at low temperature to obtain a polyamic acid solution; (2) adding an organic base to the polyamic acid solution obtained in step (1), and then dripping a dehydrating agent, heating and stirring after the dripping is completed, and after the reaction is completed, adding the obtained solution to an alcohol solvent to precipitate a precipitate; obtaining a resin powder by vacuum filtration, and then washing, filtering and drying the resin powder with an alcohol solvent to obtain a self-healing thermoplastic polyimide resin; Wherein, the diamine monomer in step (1) is the diamine monomer according to claim 1 or a diamine monomer prepared by the preparation method according to any one of claims 2 to 6.

8. The preparation method according to claim 7, characterized in that: In step (1), the molar ratio of the diamine monomer to the dianhydride monomer is 1:(1.05-2); The dianhydride monomer has any one of the structures shown in the following formulas A1 to A16: 。 9. The preparation method according to claim 7, characterized in that: In step (2), the organic base is any one or more of triethylamine, ethylenediamine, diisopropylethylamine, diethylamine, pyridine, 2,6-lutidine, 2,4,6-trimethylpyridine, 2,6-di-tert-butylpyridine, 4-dimethylaminopyridine, and 1,8-diazabicyclo[5.4.0]undec-7-ene; The dehydrating agent is any one or more of acetic anhydride, propionic anhydride, acetyl chloride, dicyclohexylcarbodiimide, trifluoroacetic anhydride and thionyl chloride; The molar ratio of the organic base to the dehydrating agent is 1:(1-4); The molar ratio of the dehydrating agent to the diamine monomer is (1-8):

1.

10. A self-healing thermoplastic polyimide resin prepared by the preparation method according to any one of claims 7 to 9, characterized in that: It has a molecular structure as shown in formula III: Formula III In the formula, Y is one of a N atom or an O atom, m is any integer between 1 and 5, n≥5, x≥5; The Ar part has any structure shown in the following formulas B1 to B16: 。

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