Core-shell particle as well as preparation method and application thereof

Abstract

The invention provides a core-shell particle as well as a preparation method and application thereof, and belongs to the technical field of thermosetting resin-based composite materials. Polyimide is used as a raw material, and polyimide microspheres are obtained through a solution coprecipitation method; uniformly dispersing the polyimide microspheres in an alkaline buffer solution, then adding dopamine hydrochloride, and reacting for 1 to obtain polydopamine activated polyimide microspheres; carrying out activating treatment on carboxylated multi-walled carbon nanotubes by using an amido bond condensing agent, and then carrying out a reaction 2 on the activated carboxylated multi-walled carbon nanotubes and the polydopamine activated polyimide microspheres to obtain PI (at) C-CNTs; and coating the PI (at) C-CNTs with methyl methacrylate through a polymerization reaction to obtain the core-shell particle. The core-shell particles are added into epoxy resin, so that the mechanical property of the epoxy resin composite material is remarkably improved on the premise of ensuring the insulating property of the cured epoxy resin.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermosetting resin-based composite materials, in particular to a kind of core-shell particles and its preparation method and application. BACKGROUND

[0002] Epoxy resin is the most widely used thermosetting resin in engineering at present, which is widely used in electronic and electrical, aerospace and other fields due to its good adhesion and excellent corrosion resistance. However, the cured epoxy resin forms a three-dimensional network structure inside, which has the disadvantages of high crosslinking density, high internal stress and poor impact resistance, thus greatly limiting the application range of epoxy resin. Therefore, the toughening of epoxy resin has become a research hotspot.

[0003] In order to improve the toughness of epoxy resin, the current toughening methods of epoxy resin mainly include: rubber toughening, thermoplastic resin toughening, nano-particle toughening, core-shell particle toughening, interpenetrating network toughening, biomass toughening and hyperbranched toughening. Although the above various toughening methods can improve the toughness of thermosetting resin and its composite materials to some extent, they all have disadvantages. Rubber elastomer will reduce the glass transition temperature of the cured system, and nano-particles are easy to cause aggregation, resulting in a decrease in the mechanical properties of the resin. The system viscosity increases and the processing operation is difficult in thermoplastic resin toughening.

[0004] In recent years, core-shell structure materials have been widely used in the toughening modification of epoxy resin due to their unique structural characteristics, such as the interface interaction between the core and the shell, the protection of the shell on the core and the multifunctionality of the shell. The core-shell structure can effectively disperse stress and improve the toughness and heat resistance of the composite material. However, there are still some shortcomings and challenges in the existing technology of core-shell particles in the toughening modification of epoxy resin, such as the balance between toughness and strength: although the existing core-shell particles improve the toughness of epoxy resin to some extent, they often sacrifice part of the strength, making it difficult to achieve the balance between toughness and strength; insufficient high-temperature performance: under high-temperature conditions, the stability of the existing core-shell particles is poor, which limits the improvement of the heat resistance of the composite material and cannot meet the high-temperature application requirements. SUMMARY

[0005] Therefore, the present application aims to provide a kind of core-shell particles and its preparation method and application.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions: One of the technical solutions of the present application is a preparation method of core-shell particles, comprising the following steps: Using polyimide as raw material, polyimide microspheres are obtained by solution co-precipitation method; The polyimide microspheres are uniformly dispersed in a basic buffer solution, and then dopamine hydrochloride is added, and reaction 1 is carried out to obtain polydopamine activated polyimide microspheres; The carboxylated multi-walled carbon nanotubes are activated by using an amide bond condensing agent, and then the activated carboxylated multi-walled carbon nanotubes are subjected to reaction 2 with the polydopamine activated polyimide microspheres to obtain PI@C-CNTs. Methyl methacrylate (MMA) is coated on the PI@C-CNTs through a polymerization reaction to obtain the core-shell particles.

[0007] The core-shell particles prepared by the preparation method.

[0008] The core-shell particles prepared by the preparation method.

[0009] The present application has the following technical effects: The present application first prepares thermoplastic polyimide microspheres by using a solution co-precipitation method, and then the polyimide microspheres are coated with polydopamine, and the polydopamine structure is activated by using the rich functional groups such as hydroxyl and amino groups on the polydopamine structure, and then an amide bond condensing agent is used to form an amide bond between the carboxylated multi-walled carbon nanotubes (C-CNTs), so that the polyimide microspheres are uniformly coated with the carboxylated multi-walled carbon nanotubes, and PI@C-CNTs are prepared, and then polymethyl methacrylate (PMMA) is coated on the PI@C-CNTs through low-temperature polymerization to prepare PI@C-CNTs@PMMA, and the PI@C-CNTs@PMMA is added to the epoxy resin to prepare an epoxy resin composite material. Under the premise of ensuring the insulation performance of the cured epoxy resin, the mechanical properties of the epoxy resin composite material are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0011] Figure 1 The infrared spectrum of APBP-6FDA-50@C-CNTs@PMMA in Example 1; Figure 2 The SEM image (left) and particle size distribution graph (right) of ODA-ODPA-95 microspheres in Example 3; Figure 3 The SEM image of TDA-BPADA-120@C-CNTs@PMMA in Example 5. DETAILED DESCRIPTION

[0012] The following detailed description of various exemplary embodiments of the application will not be considered to limit the application, but rather to provide a more detailed description of certain aspects, features and embodiments of the application.

[0013] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, the use of the term "about" in relation to a value or a range of values is intended to include each individual intermediate value and each smaller range that falls within the range of values. The upper and lower limits of these smaller ranges can be included or excluded from the range.

[0014] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in further detail the methods and / or materials associated with the documents. In the event of a conflict between the content of the specification and the documents incorporated herein by reference, the content of the specification controls.

[0015] Many modifications and variations of this application can be made without departing from its spirit or scope, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is to be understood that the application is not limited in scope by the specific embodiments described herein. Rather, the specific embodiments are intended to illustrate the general principles of the application.

[0016] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended terms that are intended to mean "including but not limited to".

[0017] Unless otherwise specified, room temperature in the present application means 25±5℃.

[0018] The first aspect of the present application provides a preparation method of core-shell particles, comprising the following steps: Using polyimide as raw material, polyimide microspheres are obtained by solution co-precipitation method; The polyimide microspheres are uniformly dispersed in an alkaline buffer solution, and then dopamine hydrochloride is added, and reaction 1 is carried out to obtain polydopamine activated polyimide microspheres; The carboxylated multi-walled carbon nanotubes are activated by using an amide bond condensing agent, and then the activated carboxylated multi-walled carbon nanotubes are subjected to reaction 2 with the polydopamine activated polyimide microspheres to obtain PI@C-CNTs. The PI@C-CNTs were coated with methyl methacrylate by polymerization to obtain the core-shell particles.

[0019] This invention does not impose any special limitations on the preparation method of polyimide; conventional techniques skilled in the art can be used. Similarly, the selection of diamine monomers and dianhydride monomers is not particularly limited; commonly used diamine monomers and dianhydride monomers by those skilled in the art can be selected. As an example: The diamine monomer is at least one selected from m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminotoluene, 2,4-diaminotrifluorotoluene, 2,5-diaminotrifluorotoluene, 3,5-diaminotrifluorotoluene, 2,2'-diaminobiphenyl, 4,4'-diaminobiphenyl, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-bis(3-aminophenoxy)benzophenone, and 4,4'-bis(4-aminophenoxy)benzophenone. The dianhydride monomer is pyromellitic dianhydride, trimellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, 2,2',3,3'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride. At least one of the following: 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,3',3,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2',3,3'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfidetetracarboxylic dianhydride, 2,3',3,4'-diphenylsulfidetetracarboxylic dianhydride, 2,2',3,3'-diphenylsulfidetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylene)diphthalic anhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), and 3,3'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride).

[0020] In a preferred embodiment of the present invention, the solution coprecipitation method specifically involves: dissolving polyimide and surfactant 1 in organic solvent 1 to obtain a mixture; mixing surfactant 2 and water to obtain an emulsifier; adding the emulsifier to the mixed solution and stirring to obtain polyimide microspheres; wherein surfactant 1 is the same as surfactant 2.

[0021] In a preferred embodiment of the present invention, the surfactant 1 is at least one selected from polyvinyl alcohol, polyvinylpyrrolidone, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, polyacrylic acid, oleic acid, polyethylene glycol, sodium citrate, tetraoctylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and alkylolamide. The present invention does not impose any special limitation on the selection of organic solvent 1, as long as it can dissolve the polyimide and surfactant 1, for example, at least one selected from N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, dioxane, and tetrahydrofuran.

[0022] In a preferred embodiment of the present invention, the ratio of surfactant 1, polyimide and organic solvent 1 is 2~5 g : 2~5 g : 100 mL; the ratio of surfactant 2 and water is 2~5 g : 100 mL.

[0023] In a preferred embodiment of the present invention, after the stirring is completed, the process further includes centrifugation, washing, and drying.

[0024] In a preferred embodiment of the present invention, the alkaline buffer solution is at least one of a phosphate buffer solution, a borate buffer solution, and a tris(hydroxymethyl)aminomethane buffer solution; the pH value of the alkaline buffer solution is 7.5 to 9.5.

[0025] In a preferred embodiment of the present invention, the ratio of the polyimide microspheres to the alkaline buffer solution is 0.2-0.4 g: 100 mL; the ratio of the dopamine hydrochloride to the alkaline buffer solution is 5-8 g / 1000 mL.

[0026] In a preferred embodiment of the present invention, reaction 1 is a stirred reaction at room temperature for 12-24 h.

[0027] In a preferred embodiment of the present invention, after reaction 1 is completed, the process further includes centrifugation, washing and drying.

[0028] In a preferred embodiment of the present invention, the amide bond condensing agent is at least one selected from N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDCI), benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU) and 2-(7-azobenzotriazole)-tetramethylurea hexafluorophosphate (HATU). The specific method for activating carboxylated multi-walled carbon nanotubes using an amide bond condensing agent is as follows: under an inert atmosphere, carboxylated multi-walled carbon nanotubes, an amide bond condensing agent, and organic solvent 2 are mixed and stirred at room temperature for 12-24 h.

[0029] In a preferred embodiment of the present invention, the organic solvent 2 is at least one selected from N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, dioxane, and tetrahydrofuran; the ratio of the carboxylated multi-walled carbon nanotubes to the organic solvent 2 is 5-10 g / 1000 mL, and the ratio of the amide bond condensing agent to the organic solvent 2 is 1-3 g / 1000 mL.

[0030] In this invention, before reacting the carboxylated multi-walled carbon nanotubes, amide bond condensing agent and organic solvent 2, a pretreatment step of carboxylated multi-walled carbon nanotubes is included; the pretreatment is as follows: dispersing the carboxylated multi-walled carbon nanotubes in the organic solvent, ultrasonically dispersing them evenly, centrifuging the dispersion, discarding the supernatant, and vacuum drying.

[0031] In a preferred embodiment of the present invention, the aspect ratio of the carboxylated multi-walled carbon nanotube is 100-500, and the carboxyl content of the carboxylated multi-walled carbon nanotube is 4-8 mmol / g.

[0032] In a preferred embodiment of the present invention, the ratio of the amount of polydopamine-activated polyimide microspheres to carboxylated multi-walled carbon nanotubes is 0.25-0.5:1 (g / g).

[0033] In a preferred embodiment of the present invention, the temperature of reaction 2 is 50-70 °C and the time is 8-10 h.

[0034] In a preferred embodiment of the present invention, after reaction 2 is completed, the process further includes centrifugation, washing and drying.

[0035] In a preferred embodiment of the present invention, the polymerization reaction is carried out at a temperature of 70-80 °C for 3-5 h.

[0036] In a preferred embodiment of the present invention, methyl methacrylate is coated onto the PI@C-CNTs via a polymerization reaction. Specifically, PI@C-CNTs and methyl methacrylate (MMA) are dissolved in water, and then surfactant 3 is added and stirred to emulsify, obtaining an emulsion. Under inert gas protection, an initiator solution is added to the emulsion to carry out a polymerization reaction, obtaining the core-shell particles (denoted as PI@C-CNTs@PMMA). After the polymerization reaction is completed, the process further includes washing and drying steps.

[0037] In a preferred embodiment of the present invention, the surfactant 3 is at least one selected from polyvinyl alcohol, polyvinylpyrrolidone, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, polyacrylic acid, oleic acid, polyethylene glycol, sodium citrate, tetraoctylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and alkylolamide. The initiator is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, ammonium persulfate, potassium persulfate, and benzoyl peroxide; The ratio of PI@C-CNTs, methyl methacrylate, and water is 1 g: 2-3 g: 20-40 mL, the ratio of surfactant 3 to methyl methacrylate is 1 g: 20-50 g, and the ratio of initiator to methyl methacrylate is 1 g: 20-50 g.

[0038] The second technical solution of the present invention is a core-shell particle prepared by the above preparation method.

[0039] The third technical solution of the present invention is an epoxy resin composite material, the raw materials of which include the above-mentioned core-shell particles.

[0040] In a preferred embodiment of the present invention, the amount of core-shell particles added is 1-4 phr.

[0041] Specifically, the amount of core-shell particles added is 1 phr, 2 phr, 3 phr or 4 phr.

[0042] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0043] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0044] Example 1 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 170 mL of N,N-dimethylacetamide (DMAc), then add 19.8219 g (50 mmol) of 4,4'-bis(3-aminophenoxy)benzophenone (APBP). Stir at room temperature until 4,4'-bis(3-aminophenoxy)benzophenone is completely dissolved. Add 21.7678 g (49 mmol) of hexafluorodianhydride (6FDA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide APBP-6FDA-50 with a degree of polymerization n=50.

[0045] Step 2: Add 10 g of polyvinyl alcohol, 10 g of APBP-6FDA-50, and 500 mL of N,N-dimethylacetamide to a reaction vessel, stir and heat to 90 °C to completely dissolve the polyvinyl alcohol and APBP-6FDA-50; mix 20 g of polyvinyl alcohol and 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After addition, maintain heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain APBP-6FDA-50 microspheres.

[0046] Step 3: Add 2 g of APBP-6FDA-50 microspheres to 500 mL of tris(hydroxymethyl)aminomethane buffer solution at pH 8.5, disperse evenly by ultrasonication, then add 3 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine-activated APBP-6FDA-50 microspheres.

[0047] Step 4: Disperse 4 g of carboxylated multi-walled carbon nanotubes in 500 mL of N,N-dimethylacetamide, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0048] Step 5: Under a nitrogen atmosphere, 4 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of N,N-dimethylacetamide. 1 g of 2-(7-azobenzotriazole)-tetramethylurea hexafluorophosphate (HATU) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 2 g of polydopamine-activated APBP-6FDA-50 microspheres were added to the mixed solution. The mixture was reacted at 50 °C for 10 h, centrifuged, washed with N,N-dimethylacetamide and deionized water, and vacuum dried to obtain APBP-6FDA-50@C-CNTs.

[0049] Step 6: Disperse 1.5 g of APBP-6FDA-50@C-CNTs in 4 g of methyl methacrylate, then dissolve in 45 mL of deionized water. Add 0.2 g of sodium dodecyl sulfate to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.2 g of potassium persulfate in 45 mL of deionized water. Under nitrogen protection, add the potassium persulfate solution dropwise to the emulsion to carry out the polymerization reaction. React at 80 °C for 4 h, then wash with deionized water and vacuum dry to obtain APBP-6FDA-50@C-CNTs@PMMA.

[0050] Example 2 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 150 mL of N,N-dimethylacetamide (DMAc), followed by 7.9304 g (40 mmol) of 4,4'-diaminodiphenylmethane (MDA). Stir at room temperature until the 4,4'-diaminodiphenylmethane is completely dissolved. Add 20.5594 g (39.5 mmol) of 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) (BPADA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide MDA-BPADA-80 with a degree of polymerization n=80.

[0051] Step 2: Add 20 g of sodium dodecyl sulfate, 20 g of MDA-BPADA-80, and 500 mL of N,N-dimethylformamide to a reaction vessel, stir, and heat to 90 °C to completely dissolve the sodium dodecyl sulfate and MDA-BPADA-80. Mix 30 g of sodium dodecyl sulfate with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After the addition is complete, continue heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain MDA-BPADA-80 microspheres.

[0052] Step 3: Add 2 g of MDA-BPADA-80 microspheres to 500 mL of phosphate buffer solution with pH=8, disperse evenly by ultrasonication, then add 4 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine activated MDA-BPADA-80 microspheres.

[0053] Step 4: Disperse 3 g of carboxylated multi-walled carbon nanotubes in 500 mL of N,N-dimethylformamide, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0054] Step 5: Under a nitrogen atmosphere, 3 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of N,N-dimethylformamide. 1.5 g of benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 1.5 g of polydopamine-activated MDA-BPADA-80 microspheres were added to the mixed solution. The mixture was reacted at 60 °C for 8 h, centrifuged, washed with N,N-dimethylformamide and deionized water, and vacuum dried to obtain MDA-BPADA-80@C-CNTs.

[0055] Step 6: Disperse 2 g of MDA-BPADA-80@C-CNTs in 5 g of methyl methacrylate, then dissolve in 50 mL of deionized water. Add 0.2 g of polyvinylpyrrolidone to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.2 g of ammonium persulfate in 50 mL of deionized water. Under nitrogen protection, add the ammonium persulfate solution dropwise to the emulsion to carry out the polymerization reaction. React at 70 °C for 5 h, wash with deionized water, and vacuum dry to obtain MDA-BPADA-80@C-CNTs@PMMA.

[0056] Example 3 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 150 mL of N,N-dimethylacetamide (DMAc), then add 9.5114 g (47.5 mmol) of 4,4'-diaminodiphenyl ether (ODA). Stir at room temperature until 4,4'-diaminodiphenyl ether is completely dissolved. Add 14.5799 g (47 mmol) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide ODA-ODPA-95 with a degree of polymerization n=95.

[0057] Step 2: Add 15 g of octadecyltrimethylammonium chloride, 15 g of ODA-ODPA-95, and 500 mL of N-methylpyrrolidone to a reaction vessel, stir, and heat to 90 °C to completely dissolve the octadecyltrimethylammonium chloride and ODA-ODPA-95. Mix 40 g of octadecyltrimethylammonium chloride with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After the addition is complete, continue heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain ODA-ODPA-95 microspheres.

[0058] Step 3: Add 1 g of ODA-ODPA-95 microspheres to 500 mL of borate buffer solution with pH=9, disperse evenly by ultrasonication, then add 2.5 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine activated ODA-ODPA-95 microspheres.

[0059] Step 4: Disperse 2.5 g of carboxylated multi-walled carbon nanotubes in 500 mL of N-methylpyrrolidone, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0060] Step 5: Under a nitrogen atmosphere, 2.5 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of N-methylpyrrolidone, and 0.5 g of N,N'-dicyclohexylcarbodiimide (DCC) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 1 g of polydopamine-activated ODA-ODPA-95 microspheres were added to the mixed solution and reacted at 65 °C for 9 h. After centrifugation, the microspheres were washed with N-methylpyrrolidone and deionized water and dried under vacuum to obtain ODA-ODPA-95@C-CNTs.

[0061] Step 6: Disperse 3 g of ODA-ODPA-95@C-CNTs in 7 g of methyl methacrylate (MMA), then dissolve in 90 mL of deionized water. Add 0.3 g of polyvinyl alcohol to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.3 g of azobisisobutyronitrile in 60 mL of deionized water. Under nitrogen protection, add the azobisisobutyronitrile solution dropwise to the emulsion to carry out the polymerization reaction. React at 75 °C for 5 h, then wash with deionized water and vacuum dry to obtain ODA-ODPA-95@C-CNTs@PMMA.

[0062] Example 4 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 150 mL of N,N-dimethylacetamide (DMAc), then add 5.4070 g (50 mmol) of m-phenylenediamine (MPD). Stir at room temperature until the m-phenylenediamine is completely dissolved. Add 21.9899 g (49.5 mmol) of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120°C for 12 h to obtain a thermoplastic soluble polyimide MPD-6FDA-100 with a degree of polymerization n=100.

[0063] Step 2: Add 25 g of polyethylene glycol, 25 g of MPD-6FDA-100, and 500 mL of dimethyl sulfoxide to a reaction vessel, stir, and heat to 90 °C to completely dissolve the polyethylene glycol and MPD-6FDA-100. Mix 50 g of polyethylene glycol with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After the addition is complete, continue heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain MPD-6FDA-100 microspheres.

[0064] Step 3: Add 3 g of MPD-6FDA-100 microspheres to 800 mL of tris(hydroxymethyl)aminomethane buffer solution at pH=8, disperse evenly by ultrasonication, then add 4 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine-activated MPD-6FDA-100 microspheres.

[0065] Step 4: Disperse 5 g of carboxylated multi-walled carbon nanotubes in 500 mL of dimethyl sulfoxide, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0066] Step 5: Under a nitrogen atmosphere, 5 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of dimethyl sulfoxide. 1 g of N,N'-diisopropylcarbodiimide (DIC) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 2.5 g of polydopamine-activated MPD-6FDA-100 microspheres were added to the mixed solution and reacted at 65 °C for 9 h. After centrifugation, the microspheres were washed with dimethyl sulfoxide and deionized water and dried under vacuum to obtain MPD-6FDA-100@C-CNTs.

[0067] Step 6: Disperse 1.5 g of MPD-6FDA-100@C-CNTs in 3.5 g of methyl methacrylate (MMA), then dissolve in 50 mL of deionized water. Add 0.15 g of sodium dodecylbenzenesulfonate to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.15 g of azobisisobutyronitrile in 35 mL of deionized water. Under nitrogen protection, add the azobisisobutyronitrile solution dropwise to the emulsion to carry out the polymerization reaction. React at 70 °C for 5 h, wash with deionized water, and vacuum dry to obtain MPD-6FDA-100@C-CNTs@PMMA.

[0068] Example 5 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 160 mL of N,N-dimethylacetamide (DMAc), then add 7.3302 g (60 mmol) of 2,4-diaminotoluene (TDA). Stir at room temperature until the 2,4-diaminotoluene is completely dissolved. Add 30.9692 g (59.5 mmol) of 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) (BPADA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide TDA-BPADA-120 with a degree of polymerization n=120.

[0069] Step 2: Add 20 g of alkylphenol polyoxyethylene ether, 20 g of TDA-BPADA-120, and 500 mL of N,N-dimethylformamide to a reaction vessel, stir, and heat to 90 °C to completely dissolve the alkylphenol polyoxyethylene ether and TDA-BPADA-120. Mix 25 g of alkylphenol polyoxyethylene ether with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After the addition is complete, continue heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain TDA-BPADA-120 microspheres.

[0070] Step 3: Add 2 g of TDA-BPADA-120 microspheres to 500 mL of phosphate buffer solution with pH=9, disperse evenly by ultrasonication, then add 3 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine activated TDA-BPADA-120 microspheres.

[0071] Step 4: Disperse 4 g of carboxylated multi-walled carbon nanotubes in 500 mL of N,N-dimethylformamide, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0072] Step 5: Under a nitrogen atmosphere, 4 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of N,N-dimethylformamide. 1.5 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDCI) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 2 g of polydopamine-activated TDA-BPADA-120 microspheres were added to the mixed solution and reacted at 55 °C for 10 h. After centrifugation, the microspheres were washed with N,N-dimethylformamide and deionized water and dried under vacuum to obtain TDA-BPADA-120@C-CNTs.

[0073] Step 6: Disperse 2 g of TDA-BPADA-120@C-CNTs in 5.5 g of methyl methacrylate (MMA), then dissolve it in 70 mL of deionized water. Add 0.2 g of tetraoctylammonium bromide to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.25 g of benzoyl peroxide in 50 mL of deionized water. Under nitrogen protection, add the benzoyl peroxide solution dropwise to the emulsion to carry out the polymerization reaction. React at 80 °C for 4 h, wash with deionized water, and vacuum dry to obtain TDA-BPADA-120@C-CNTs@PMMA.

[0074] Example 6 Step 1: In a 250 mL mechanically stirred three-necked flask under nitrogen atmosphere, add 170 mL of N,N-dimethylacetamide (DMAc), then add 23.7863 g (60 mmol) of 4,4'-bis(3-aminophenoxy)benzophenone (APBP). Stir at room temperature until 4,4'-bis(3-aminophenoxy)benzophenone is completely dissolved. Add 12.8691 g (59 mmol) of pyromellitic dianhydride (PMDA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide APBP-PMDA-60 with a degree of polymerization n=60.

[0075] Step 2: Add 18 g of polyvinylpyrrolidone, 18 g of APBP-PMDA-60, and 500 mL of N,N-dimethylacetamide to a reaction vessel, stir, and heat to 90 °C to completely dissolve the polyvinylpyrrolidone and APBP-PMDA-60. Mix 25 g of polyvinylpyrrolidone with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After the addition is complete, continue heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain APBP-PMDA-60 microspheres.

[0076] Step 3: Add 2 g of APBP-PMDA-60 microspheres to 500 mL of borate buffer solution with pH=8, disperse evenly by ultrasonication, then add 4 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine activated APBP-PMDA-60 microspheres.

[0077] Step 4: Disperse 5 g of carboxylated multi-walled carbon nanotubes in 500 mL of N,N-dimethylacetamide, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0078] Step 5: Under a nitrogen atmosphere, 5 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of N,N-dimethylacetamide. 1 g of benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 2 g of polydopamine-activated APBP-PMDA-60 microspheres were added to the mixed solution. The mixture was reacted at 65 °C for 9 h, centrifuged, washed with N,N-dimethylacetamide and deionized water, and vacuum dried to obtain APBP-PMDA-60@C-CNTs.

[0079] Step 6: Disperse 2.5 g of APBP-PMDA-60@C-CNTs in 6 g of methyl methacrylate (MMA), then dissolve in 80 mL of deionized water. Add 0.3 g of octadecyltrimethylammonium chloride to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.3 g of potassium persulfate in 60 mL of deionized water. Under nitrogen protection, add the potassium persulfate solution dropwise to the emulsion to carry out the polymerization reaction. React at 75 °C for 5 h. Wash with deionized water and vacuum dry to obtain APBP-PMDA-60@C-CNTs@PMMA.

[0080] Example 7 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 150 mL of N,N-dimethylacetamide (DMAc), then add 4.5960 g (42.5 mmol) of p-phenylenediamine (PPD). Stir at room temperature until the p-phenylenediamine is completely dissolved. Add 15.0478 g (42 mmol) of 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide PPD-DSDA-85 with a degree of polymerization n=85.

[0081] Step 2: Add 23 g of hexadecyltrimethylammonium bromide, 23 g of PPD-DSDA-85, and 500 mL of N-methylpyrrolidone to a reaction vessel, stir, and heat to 90 °C to completely dissolve the hexadecyltrimethylammonium bromide and PPD-DSDA-85. Mix 35 g of hexadecyltrimethylammonium bromide with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After the addition is complete, continue heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain PPD-DSDA-85 microspheres.

[0082] Step 3: Add 2 g of PPD-DSDA-85 microspheres to 500 mL of tris(hydroxymethyl)aminomethane buffer solution at pH=8, disperse evenly by ultrasonication, then add 3.5 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine-activated PPD-DSDA-85 microspheres.

[0083] Step 4: Disperse 3.5 g of carboxylated multi-walled carbon nanotubes in 500 mL of N-methylpyrrolidone, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0084] Step 5: Under a nitrogen atmosphere, 3.5 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of N-methylpyrrolidone. 1 g of 2-(7-azobenzotriazole)-tetramethylurea hexafluorophosphate (HATU) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 1.5 g of polydopamine-activated PPD-DSDA-85 microspheres were added to the mixed solution. The mixture was reacted at 70 °C for 8 h, centrifuged, washed with N-methylpyrrolidone and deionized water, and vacuum dried to obtain PPD-DSDA-85@C-CNTs.

[0085] Step 6: Disperse 1 g of PPD-DSDA-85@C-CNTs in 3 g of methyl methacrylate (MMA), then dissolve it in 30 mL of deionized water. Add 0.1 g of hexadecyltrimethylammonium bromide to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.1 g of azobisisobutyronitrile in 60 mL of deionized water. Under nitrogen atmosphere, add the azobisisobutyronitrile solution dropwise to the emulsion to carry out the polymerization reaction. React at 80 °C for 4 h, wash with deionized water, and vacuum dry to obtain PPD-DSDA-85@C-CNTs@PMMA.

[0086] Example 8 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 150 mL of N,N-dimethylacetamide (DMAc), then add 13.8753 g (35 mmol) of 4,4'-bis(3-aminophenoxy)benzophenone (APBP). Stir at room temperature until 4,4'-bis(3-aminophenoxy)benzophenone is completely dissolved. Add 11.1169 g (34.5 mmol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide APBP-BTDA-70 with a degree of polymerization n=70.

[0087] Step 2: Add 20 g of tetraoctylammonium bromide, 20 g of APBP-BTDA-70, and 500 mL of tetrahydrofuran to a reaction vessel. Stir and heat to 90 °C to completely dissolve the tetraoctylammonium bromide and APBP-BTDA-70. Simultaneously, mix 20 g of tetraoctylammonium bromide with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After addition, maintain heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain APBP-BTDA-70 microspheres.

[0088] Step 3: Add 1 g of APBP-BTDA-70 microspheres to 500 mL of phosphate buffer solution with pH=8.5, disperse evenly by ultrasonication, then add 2.5 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine activated APBP-BTDA-70 microspheres.

[0089] Step 4: Disperse 2.5 g of carboxylated multi-walled carbon nanotubes in 500 mL of tetrahydrofuran, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0090] Step 5: Under a nitrogen atmosphere, 2.5 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of tetrahydrofuran. 1.5 g of N,N'-dicyclohexylcarbodiimide (DCC) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 1 g of polydopamine-activated APBP-BTDA-70 microspheres were added to the mixed solution. The mixture was reacted at 60 °C for 9 h, centrifuged, washed with tetrahydrofuran and deionized water, and vacuum dried to obtain APBP-BTDA-70@C-CNTs.

[0091] Step 6: Disperse 2 g of APBP-BTDA-70@C-CNTs in 5 g of methyl methacrylate (MMA), then dissolve in 60 mL of deionized water. Add 0.25 g of sodium citrate to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.2 g of ammonium persulfate in 40 mL of deionized water. Under nitrogen protection, add the ammonium persulfate solution dropwise to the emulsion to carry out the polymerization reaction. React at 80 °C for 4 h, wash with deionized water, and vacuum dry to obtain APBP-BTDA-70@C-CNTs@PMMA.

[0092] Example 9 Step 1: In a 250 mL mechanically stirred three-necked flask under nitrogen atmosphere, add 180 mL of N,N-dimethylacetamide (DMAc), then add 15.0180 g (75 mmol) of 4,4'-diaminodiphenyl ether (ODA). Stir at room temperature until the 4,4'-diaminodiphenyl ether is completely dissolved. Add 26.6919 g (74.5 mmol) of 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide ODA-DSDA-150 with a degree of polymerization n=150.

[0093] Step 2: Add 25 g of sodium fatty alcohol polyoxyethylene ether sulfate, 25 g of ODA-DSDA-150, and 500 mL of dioxane to a reaction vessel, stir, and heat to 90 °C to completely dissolve the sodium fatty alcohol polyoxyethylene ether sulfate and ODA-DSDA-150. Mix 50 g of sodium fatty alcohol polyoxyethylene ether sulfate with 1000 mL of deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After the addition is complete, continue heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain ODA-DSDA-150 microspheres.

[0094] Step 3: Add 2 g of ODA-DSDA-150 microspheres to 500 mL of borate buffer solution with pH=9, disperse evenly by ultrasonication, then add 3.5 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine activated ODA-DSDA-150 microspheres.

[0095] Step 4: Disperse 4.5 g of carboxylated multi-walled carbon nanotubes in 500 mL of dioxane, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0096] Step 5: Under a nitrogen atmosphere, 4.5 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of dioxane. 1.5 g of N,N'-diisopropylcarbodiimide (DIC) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 2 g of polydopamine-activated ODA-DSDA-150 microspheres were added to the mixed solution and reacted at 70 °C for 8 h. After centrifugation, the microspheres were washed with dioxane and deionized water and dried under vacuum to obtain ODA-DSDA-150@C-CNTs.

[0097] Step 6: Disperse 2.5 g of ODA-DSDA-150@C-CNTs in 6 g of methyl methacrylate (MMA), then dissolve in 80 mL of deionized water. Add 0.3 g of polyethylene glycol to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.25 g of azobisisobutyronitrile in 50 mL of deionized water. Under nitrogen protection, add the azobisisobutyronitrile solution dropwise to the emulsion to carry out the polymerization reaction. React at 70 °C for 5 h, wash with deionized water, and vacuum dry to obtain ODA-DSDA-150@C-CNTs@PMMA.

[0098] Example 10 Step 1: In a 250 mL mechanically stirred three-necked flask purged with nitrogen, add 150 mL of N,N-dimethylacetamide (DMAc), followed by 6.7194 g (55 mmol) of 2,4-diaminotoluene (TDA). Stir at room temperature until the 2,4-diaminotoluene is completely dissolved. Add 15.8879 g (54 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) in portions to the solution, and react for 12 h. Add 20 mL of xylene to the three-necked flask and stir until homogeneous. Then heat to 180 °C and reflux azeotropically for 9 hours, collecting water using a Dean-Stark apparatus. Cool to room temperature. Add the mixture to 500 mL of water and allow it to stand for 1 hour until the solid completely precipitates. Filter to obtain the precipitate and wash three times with deionized water. The product was dried at 120 °C for 12 h to obtain a thermoplastic soluble polyimide TDA-BPDA-55 with a degree of polymerization n=55.

[0099] Step 2: Add 15 g sodium citrate, 15 g TDA-BPDA-55, and 500 mL N,N-dimethylacetamide to a reaction vessel, stir and heat to 90 °C to completely dissolve the sodium citrate and TDA-BPDA-55; mix 45 g sodium citrate and 1000 mL deionized water to obtain an emulsifier. Then, add the emulsifier dropwise to the reaction vessel. After addition, maintain heating and stirring until all polymer microspheres are completely precipitated. Centrifuge, wash, and dry to obtain TDA-BPDA-55 microspheres.

[0100] Step 3: Add 2 g of TDA-BPDA-55 microspheres to 500 mL of tris(hydroxymethyl)aminomethane buffer solution at pH=9, disperse evenly by ultrasonication, then add 4 g of dopamine hydrochloride, stir at room temperature for 24 h, centrifuge the mixture, wash with deionized water, and vacuum dry to obtain polydopamine-activated TDA-BPDA-55 microspheres.

[0101] Step 4: Disperse 4 g of carboxylated multi-walled carbon nanotubes in 500 mL of N,N-dimethylacetamide, then centrifuge the dispersion, discard the supernatant, and vacuum dry.

[0102] Step 5: Under a nitrogen atmosphere, 4 g of the carboxylated multi-walled carbon nanotubes obtained in Step 4 were placed in 500 mL of N,N-dimethylacetamide, and 1 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDCI) was added to the above mixed solution. The mixture was sonicated and stirred at room temperature for 24 h to activate the carboxyl groups on the carboxylated multi-walled carbon nanotubes. Then, 1.5 g of polydopamine-activated TDA-BPDA-55 microspheres were added to the mixed solution and reacted at 50 °C for 10 h. After centrifugation, the microspheres were washed with N,N-dimethylacetamide and deionized water and dried under vacuum to obtain TDA-BPDA-55@C-CNTs.

[0103] Step 6: Disperse 3 g of TDA-BPDA-55@C-CNTs in 8 g of methyl methacrylate (MMA), then dissolve in 100 mL of deionized water. Add 0.4 g of alkylphenol polyoxyethylene ether to the mixed sample and stir to emulsify, obtaining an emulsion. Then, dissolve 0.4 g of ammonium persulfate in 70 mL of deionized water. Under nitrogen protection, add the ammonium persulfate solution dropwise to the emulsion to carry out the polymerization reaction. React at 80 °C for 5 h, wash with deionized water, and vacuum dry to obtain TDA-BPDA-55@C-CNTs@PMMA.

[0104] Characterization and efficacy verification (1) Characterization: The infrared spectrum of APBP-6FDA-50@C-CNTs@PMMA in Example 1 is as follows:Figure 1 As shown, the successful synthesis of APBP-6FDA-50@C-CNTs@PMMA can be seen.

[0105] SEM images and particle size distribution diagrams of ODA-ODPA-95 microspheres in Example 3 are shown below. Figure 2 As shown, the particle size distribution of ODA-ODPA-95 microspheres is relatively concentrated.

[0106] The SEM image of TDA-BPADA-120@C-CNTs@PMMA in Example 5 is shown below. Figure 3 As shown, TDA-BPADA-120 microspheres are uniformly coated with C-CNTs.

[0107] (2) Effect verification: Different amounts of core-shell particles obtained in Examples 2, 6, and 10 were added to epoxy resin using a blending modification method to prepare the required test strips, and the tensile properties, flexural properties, and impact strength of the strips were tested.

[0108] Table 1. Tensile properties, flexural properties, and impact strength of the epoxy resin composite material prepared by adding core-shell particles to epoxy resin in Example 2.

[0109] Table 2. Tensile properties, flexural properties, and impact strength of the epoxy resin composite material prepared by adding core-shell particles to epoxy resin in Example 6.

[0110] Table 3. Tensile properties, flexural properties, and impact strength of the epoxy resin composite material prepared by adding core-shell particles from Example 10 to epoxy resin.

[0111] Table 4 Tensile properties, flexural properties, and impact strength of epoxy resin composites prepared by adding core-shell particles to epoxy resin in Examples 1, 3, 4, 5, 7, 8, and 9 (the amount of core-shell particles added is fixed at 3 phr).

[0112] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing core-shell particles, characterized in that, Includes the following steps: Polyimide microspheres were obtained from polyimide using a solution co-precipitation method. The polyimide microspheres were uniformly dispersed in an alkaline buffer solution, and then dopamine hydrochloride was added. Reaction 1 was carried out to obtain polydopamine-activated polyimide microspheres. Carboxylated multi-walled carbon nanotubes were activated using an amide bond condensing agent, and then the activated carboxylated multi-walled carbon nanotubes were reacted with the polydopamine-activated polyimide microspheres to obtain PI@C-CNTs. The PI@C-CNTs were coated with methyl methacrylate by polymerization to obtain the core-shell particles.

2. The preparation method according to claim 1, characterized in that, The solution coprecipitation method specifically involves: dissolving polyimide and surfactant 1 in organic solvent 1 to obtain a mixture; mixing surfactant 2 with water to obtain an emulsifier; adding the emulsifier to the mixture and stirring to obtain polyimide microspheres; wherein surfactant 1 is the same as surfactant 2.

3. The preparation method according to claim 1, characterized in that, The alkaline buffer solution is at least one of phosphate buffer solution, borate buffer solution and tris(hydroxymethyl)aminomethane buffer solution; the pH value of the alkaline buffer solution is 7.5 to 9.

5.

4. The preparation method according to claim 1, characterized in that, The reaction 1 was carried out by stirring at room temperature for 12-24 hours.

5. The preparation method according to claim 1, characterized in that, The amide bond condensing agent is at least one of N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate, and 2-(7-azobenzotriazole)-tetramethylurea hexafluorophosphate; the activation treatment of carboxylated multi-walled carbon nanotubes using the amide bond condensing agent specifically involves: under an inert atmosphere, mixing the carboxylated multi-walled carbon nanotubes, the amide bond condensing agent, and organic solvent 2, and then stirring the mixture at room temperature for 12-24 h.

6. The preparation method according to claim 1, characterized in that, The temperature of reaction 2 is 50-70 °C, and the time is 8-10 h.

7. The preparation method according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 70-80 °C for 3-5 h.

8. Core-shell particles prepared by the preparation method according to any one of claims 1-7.

9. An epoxy resin composite material, characterized in that, The raw materials include the core-shell particles as described in claim 8.

10. The epoxy resin composite material according to claim 9, characterized in that, The amount of core-shell particles added is 1-4 phr.

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