Polyimide composite film for realizing high-dispersion carbon nanotubes through chemical anchoring and preparation method of polyimide composite film

Abstract

The invention relates to a polyimide composite film for realizing high-dispersion carbon nanotubes through chemical anchoring and a preparation method of the polyimide composite film, which are used for solving the problems that carbon nanotubes in the existing carbon nanotube / polyimide composite material are easy to agglomerate, poor in interfacial compatibility and low in grafting efficiency. The preparation method comprises the following steps: S1, ultrasonically dispersing aminated carbon nanotubes in anhydrous dimethylacetamide to obtain a stable dispersion liquid; s2, slowly dropwise adding pyromellitic dianhydride into the stable dispersion liquid under an ice bath condition, and enabling the pyromellitic dianhydride to react with the aminated carbon nanotubes under the assistance of triethylamine to form anchor points; s3, adding a diamine monomer 4, 4 '-diaminodiphenyl ether, and gradually adding the residual pyromellitic dianhydride to carry out in-situ polymerization; and S4, preparing a wet film by adopting a curtain coating or spin coating method, and carrying out step-by-step thermal imidization at 80-300 DEG C to obtain the covalent composite film. Controllable covalent connection of the carbon nanotubes and pure polyimide chain segments can be achieved on the molecular level, and therefore the composite film with excellent heat conductivity, electromagnetic shielding performance and mechanical performance is obtained.

Description

Technical Field

[0001] This invention relates to the field of preparation technology of aminated carbon nanotube-grafted polyimide composite films, specifically a polyimide composite film with highly dispersed carbon nanotubes achieved by chemical anchoring and its preparation method. Background Technology

[0002] The intrinsic thermal conductivity of pure polyimide (PI) is low, and it lacks effective electromagnetic wave shielding capabilities, making it difficult to meet the comprehensive requirements of high thermal conductivity, lightweight, and electromagnetic compatibility in 5G / 6G communication equipment and avionics systems. Carbon nanotubes (CNTs) have extremely high specific surface area, excellent electrical and thermal conductivity, and mechanical strength, and are considered ideal fillers for improving the overall performance of polyimide. However, since the surface of CNTs is an inert graphitized carbon layer, they are prone to agglomeration, and the interfacial bonding force between them and the polyimide matrix is ​​weak, which limits the performance improvement of composite materials. Therefore, improving the dispersibility and interfacial compatibility of CNTs in the polyimide matrix has become a key issue in current composite material research. Existing studies mostly use physical dispersion or chemical functionalization to improve the dispersibility of CNTs. Although these methods have improved the interfacial interaction between CNTs and polyimide to some extent, they still have the following shortcomings: (1) Traditional acidification methods will destroy the π-conjugated structure of CNTs, weakening their electrical and thermal conductivity. (2) Non-covalent coating is prone to failure during high-temperature imidization, leading to interfacial debonding. (3) In existing covalent grafting systems, the binding position of CNT and polyimide is uncontrollable, the grafting efficiency is low, and it is difficult to achieve quantitative control.

[0003] Furthermore, existing methods for preparing CNT / PI composites mostly employ a blending-thermal imidization route, where functionalized CNTs are directly mixed with a polyamic acid (PAA) solution before film formation. However, this method lacks a molecular-level anchoring step during CNT addition, leading to CNT agglomeration or uneven distribution during PAA polymerization, insufficient interfacial bonding strength, and significant room for improvement in the thermal conductivity and shielding performance of the final PI film.

[0004] Therefore, there is an urgent need for a novel method for preparing composite films that enables directional covalent bonding of CNTs and PI precursors at the molecular level with controllable grafting ratios. This method aims to achieve high dispersibility and strong interfacial bonding while maintaining the structural integrity of CNTs, thereby significantly improving the electromagnetic shielding effectiveness, thermal conductivity, and mechanical stability of the composite film. Summary of the Invention

[0005] The purpose of this invention is to provide a polyimide composite film with highly dispersed carbon nanotubes achieved through chemical anchoring and its preparation method, addressing the problems of easy agglomeration of carbon nanotubes (CNTs) in existing CNT / PI composite materials, poor interfacial compatibility, and low grafting efficiency. This invention enables controllable covalent bonding between CNTs and PI segments at the molecular level, significantly improving the dispersion and interfacial bonding of CNTs in the PI matrix, thereby obtaining a composite film with excellent thermal conductivity, electromagnetic shielding performance, and mechanical properties.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: a polyimide composite film of highly dispersed carbon nanotubes is achieved by chemical anchoring, comprising aminated carbon nanotubes (CNT-NH2), diamine monomer 4,4′-diaminodiphenyl ether (ODA), pyromellitic dianhydride (PMDA), anhydrous dimethylacetamide (DMAc), triethylamine (TEA), and nitrogen gas; wherein, the outer diameter of CNT-NH2 is 1-2 nm, the length is 5-30 μm, and the mass is 0.065-0.325 parts by weight; the purity of ODA is ≥99%, and the mass is 3.065 g parts by weight; the purity of PMDA is ≥99%, and the mass is 3.317-3.497 parts by weight; the purity of DMAc is ≥99.8%, and the volume is 30-40 parts by volume; and the purity of TEA is ≥99%, and the mass is 0.03 parts by weight.

[0007] This invention also provides a method for preparing a polyimide composite film with highly dispersed carbon nanotubes through chemical anchoring, comprising the following steps: S1. Aminated carbon nanotubes (CNT-NH2) were ultrasonically dispersed in anhydrous dimethylacetamide (DMAc) to obtain a stable dispersion. S2. Under ice bath conditions, pyromellitic dianhydride (PMDA) is slowly added dropwise to the stable dispersion, and triethylamine (TEA) is used as a single catalyst to help it react with CNT–NH2 to form CNT-NH-CO-PMDA anchor points. S3. Add diamine monomer 4,4′-diaminodiphenyl ether ODA and gradually add the remaining PMDA to carry out in-situ polymerization to generate CNT-PAA composite solution; S4. Prepare a wet film using casting or spin coating methods, and then perform stepwise thermal imidization at 80-300 °C to obtain a CNT / PI covalent composite film.

[0008] Furthermore, the specific steps of step S1 include: S1.1. The aminated carbon nanotubes CNT-NH2 were dried under vacuum at 80 °C for 12 h to remove adsorbed moisture and ensure the surface amino activity. S1.2 Disperse the dry CNT-NH2 in 20 parts by volume of anhydrous dimethylacetamide DMAc, and add 0.03 parts by weight of triethylamine TEA as a catalyst; S1.3. Under ice bath conditions of 0-5 ℃, use a probe to ultrasonically treat for 30 min to achieve a highly dispersed state of CNTs; S1.4. Let stand for 10 minutes, and use TEM or SEM to check the uniformity of CNT dispersion to ensure that there is no obvious agglomeration.

[0009] Furthermore, the specific steps of step S2 include: S2.1 Dissolve PMDA in 2 parts by volume of DMAc and slowly add it dropwise to the CNT-NH2 suspension at a rate of 0.1 parts by volume / min to ensure that the anhydride groups are in uniform contact with the CNT surface; S2.2. Stir at low temperature for 2 hours under TEA catalysis, then raise to room temperature and continue stirring for 1 hour to form CNT-NH-CO-PMDA anchor sites.

[0010] Furthermore, the specific steps of step S3 include: S3.1 Adding diamine monomer: Under nitrogen protection and stirring conditions, add diamine monomer 4,4′-diaminodiphenyl ether ODA to the dispersion obtained in step S2, and stir until fully dissolved; S3.2 Execute the stoichiometric compensation mechanism: Based on the amino content on the surface of the aminated carbon nanotubes CNT-NH2 and the amount of PMD molar consumed in forming chemical anchors in step S2, calculate and add the remaining pyromellitic dianhydride PMDA in portions for in-situ polymerization. 3.3 Viscosity and Chain Growth Control: Under the catalysis of triethylamine (TEA), polymerization continued for 12-24 h. By monitoring and controlling the solution viscosity within the specified range, the PAA molecular chains were ensured to grow in situ on the CNT surface and form a high molecular weight interlocking network. S3.4, CNT surface anchors and PAA molecular chains form a preliminary stable network through covalent bonding.

[0011] Furthermore, the specific steps of step S4 include: S4.1 Prepare a wet film by casting or spin coating of a uniformly dispersed CNT-PAA solution using Doctor Blade casting or spin coating, and control the dry film thickness to be 25-50 μm; S4.2. Dry the wet film under vacuum at 80 °C for 1 h to remove the solvent and obtain a preliminary dry film; S4.3, keep at 80℃ for 1 hour to remove residual solvent and bubbles; S4.4, kept at 150℃ for 1 hour, initial imidization, TEA assists in ring closure; S4.5, 200℃ for 1 hour, CNT and PAA / PI chain further covalently integrated; S4.6, held at 300℃ for 1 hour, complete imidization, forming a stable PI network, with CNTs fixed on the PI chain.

[0012] The beneficial effects of this invention are: this invention can achieve controllable covalent connection between carbon nanotubes (CNTs) and PI segments at the molecular level, significantly improving the dispersion and interfacial bonding of CNTs in the PI matrix, thereby obtaining a composite film with excellent thermal conductivity, electromagnetic shielding performance and mechanical properties. Attached Figure Description

[0013] Figure 1 A comparison diagram of the preparation process of PI / CNT composite materials; Figure 2 This is a comparison chart of FTIR values; Figure 3 One of the overall observation images of the ungrafted CNT / PI composite film; Figure 4 for Figure 3 A magnified view of a portion of the image; Figure 5 The second image shows the overall observation of the ungrafted CNT / PI composite film; Figure 6 for Figure 5 A magnified view of a portion of the image; Figure 7 Overall observation of PI / CNT composite film prepared by thermal imidization after grafting PAA onto aminated carbon nanotubes; Figure 8 for Figure 7 A magnified view of a portion of the image. Detailed Implementation

[0014] The innovation of this invention lies in the introduction of a stepwise grafting polymerization strategy to achieve controllable chemical anchoring of carbon nanotubes (CNTs) in polyimide (PI) chains. Specifically, (1) Anchoring step: using the imide precursor reaction between aminated CNTs and pyromellitic dianhydride (PMDA), amic acid-type chemical anchors are constructed on the CNT surface to achieve controllable grafting. This step accelerates the reaction with a single catalyst, triethylamine (TEA), improves the grafting uniformity, and provides stable chemical sites for subsequent polymerization. (2) In-situ polymerization step: based on the anchoring structure, diamine monomer 4,4′-diaminodiphenyl ether (ODA) and the remaining PMDA are introduced. PAA chains are directly grown on the CNT surface through in-situ polymerization to achieve molecular-level integration of CNTs and polymer chains. (3) Stepwise thermal imidization step: the CNT-polyamic acid (PAA) film is subjected to stepwise heating heat treatment to convert PAA into PI. At the same time, CNTs are fixed to the PI chains through covalent bonds to form a structurally stable and interface-firm CNT–PI covalent composite network.

[0015] like Figure 1 As shown, the method for preparing polyimide composite films with highly dispersed carbon nanotubes by chemical anchoring according to the present invention includes the following steps.

[0016] S1. Aminated carbon nanotubes (CNT-NH2) were ultrasonically dispersed in anhydrous dimethylacetamide (DMAc) to obtain a stable dispersion.

[0017] S2. Pyromellitic dianhydride (PMDA) is slowly added dropwise to the stable dispersion under ice bath conditions. With the assistance of a single catalyst, triethylamine (TEA), it reacts with CNT–NH2 to form CNT-NH-CO-PMDA anchor points.

[0018] S3. Add the diamine monomer 4,4′-diaminodiphenyl ether ODA and gradually add the remaining PMDA to carry out in-situ polymerization to generate a CNT-PAA composite solution.

[0019] S4. Prepare a wet film using casting or spin coating methods, and then perform stepwise thermal imidization at 80-300 °C to obtain a CNT / PI covalent composite film.

[0020] This invention achieves stable molecular-level dispersion of carbon nanotubes (CNT-NH2) in a precursor system by introducing a controllable proportion of polyamic acid (PAA) segments onto the surface of the CNT-NH2 matrix, and subsequently forms a continuous covalent interface with the polyimide (PI) matrix during thermal imidization. Compared with existing physically blended CNT / PI systems, this invention has the following significant advantages: 1. Controllable grafting density enables precise regulation of surface chemistry. With the aid of a catalyst, the PAA grafting density on the CNT surface can be precisely controlled by adjusting the feed ratio of acyl anhydride monomers and the grafting reaction conditions, thereby achieving tunable control over the number of functional groups and chain segment coverage on the carbon nanotube surface. The controllable grafted layer not only uniformly covers the CNT surface but also significantly alters the interfacial energy of CNTs, enabling them to achieve truly molecular-level stable dispersion in high-viscosity PAA solutions.

[0021] 2. Covalent anchoring constructs a high-strength interfacial bond. The amino group undergoes ring-opening addition with the PAA monomer to form an amide bond, establishing a stable chemical covalent connection between the CNT surface and the PI segments. Compared to traditional non-covalent interfacial structures dominated by van der Waals interactions or π-π stacking, this covalent anchoring significantly enhances interfacial load transfer efficiency and improves interfacial bonding energy, making CNTs less prone to detachment, slippage, or interfacial debonding in composite films.

[0022] 3. Enhanced surface polarity promotes uniform dispersion throughout the entire process. The grafted PAA segments significantly improve the compatibility between CNTs and PAA precursors. Their enhanced surface polarity and improved solvent affinity effectively reduce the aggregation barrier between CNTs, ensuring uniform and stable dispersion of CNTs in the solution phase, cured phase, and the final PI system. This molecular-scale dispersion avoids structural defects and performance degradation caused by micron-level aggregation.

[0023] 4. Stepwise thermal imidization constructs a stable and continuous interfacial structure. A stepwise thermal imidization strategy gradually transforms the grafted PAA segments into PI, simultaneously releasing internal stress and further solidifying the chemical bond between CNTs and PI. The resulting covalent interface not only exhibits high thermal stability and is resistant to cracking, but also maintains interfacial integrity under high temperatures or mechanical loads.

[0024] 5. Reduced interfacial impedance leads to synergistic improvement in multiple performance aspects. The presence of the grafted layer on the CNT surface breaks down interfacial thermal and electrical resistance, while simultaneously reducing scattering losses caused by agglomeration defects. This results in a comprehensive improvement in thermal conductivity, electromagnetic shielding efficiency, dielectric properties, and mechanical properties of the composite film. This improvement does not rely on high filler content but rather stems from the molecular engineering design of the interfacial structure, thus achieving a composite system that combines high performance and lightweight construction.

[0025] The stepwise grafting polymerization strategy of this invention enables controllable chemical anchoring and molecular-level dispersion of CNTs in PI precursors, providing a new technical approach for the design of high-performance PI / CNT composite materials and high-end applications such as electromagnetic shielding and thermal management. It also features simple process, good repeatability, and potential industrialization value.

[0026] A specific embodiment of the present invention is described below.

[0027] The raw materials for the polyimide composite film of the present invention include: CNT-NH2 with an outer diameter of 1–2 nm, a length of 5–30 μm, and a mass of 65–325 mg; ODA with a purity ≥99% and a mass of 3.065 g; PMDA with a purity ≥99% and a grafting amount of 0.045–0.225 g and an in-situ polymerization amount of 3.272 g; anhydrous dimethylacetamide (DMAc) with a purity ≥99.8% and a volume of 30–40 mL; TEA with a purity ≥99% and a mass of 0.03 g; and nitrogen gas. TEA, as a single catalyst, not only activates the anhydride groups of PMDA, accelerating the reaction between amino groups and anhydrides on the CNT-NH2 surface to form anchor points, but also catalyzes PAA polymerization and subsequent thermal imidization, improving the chemical integration and reaction uniformity of the entire composite system. A specific embodiment of the preparation steps of the polyimide composite film of highly dispersed carbon nanotubes achieved by chemical anchoring according to the present invention is described below.

[0028] Drying and dispersion of S1 and CNT-NH2.

[0029] S1.1. Ammoniated carbon nanotubes (CNT-NH2) were dried under vacuum at 80 °C for 12 h to remove adsorbed moisture and ensure the surface amino activity.

[0030] S1.2 Disperse the dry CNT-NH2 in 20 mL of anhydrous dimethylacetamide (DMAc) and add 0.03 g of triethylamine (TEA) as a catalyst.

[0031] S1.3 Under ice bath conditions of 0-5 ℃, use a probe to ultrasonically treat for 30 min to achieve a highly dispersed state of CNTs.

[0032] S1.4. Let stand for 10 minutes, and use TEM or SEM to check the uniformity of CNT dispersion to ensure that there is no obvious agglomeration.

[0033] The innovation in this step is that it uses low-temperature ultrasound combined with TEA catalysis to effectively expose the amino active sites on the CNT surface, providing uniform chemical reaction sites for subsequent grafting.

[0034] S2, catalyst-assisted CNT-PMDA grafting to form chemical anchors.

[0035] S2.1 Dissolve PMDA in 2 mL of DMAc and slowly add it dropwise to the CNT-NH2 suspension at a rate of 0.1 mL / min to ensure that the anhydride groups are in uniform contact with the CNT surface.

[0036] S2.2. Stir at low temperature for 2 hours under TEA catalysis, then raise to room temperature and continue stirring for 1 hour to form CNT-NH-CO-PMDA anchor sites.

[0037] The innovation in this step is that by precisely controlling the grafting rate and density through TEA, stable chemical anchors are formed, enabling controllable surface functionalization of CNTs.

[0038] S3, in-situ PAA polymerization and CNT covalent integration.

[0039] S3.1 Adding diamine monomer: Under nitrogen protection and stirring conditions, add 3.065 g of diamine monomer 4,4′-diaminodiphenyl ether ODA to the dispersion obtained in step S2, and stir until fully dissolved.

[0040] S3.2 Execute the stoichiometric compensation mechanism: Based on the amino content on the surface of the aminated carbon nanotubes CNT-NH2 and the amount of PMD molar consumed in forming chemical anchors in step S2, calculate and add the remaining 3.272g of pyromellitic dianhydride PMDA in portions for in-situ polymerization.

[0041] 3.3 Viscosity and Chain Growth Control: Under the catalysis of triethylamine (TEA), polymerization was carried out for 12-24 h. The viscosity of the solution was monitored and controlled within the specified range to ensure that PAA molecular chains grew in situ on the CNT surface and formed a high molecular weight interlocking network.

[0042] S3.4, CNT surface anchors and PAA molecular chains form a preliminary stable network through covalent bonding.

[0043] The innovation of this step is that in-situ polymerization achieves molecular-level integration of CNTs and polyamic acid chains, avoiding the aggregation of CNTs in traditional physical mixing.

[0044] S4. Film formation and preliminary drying.

[0045] S4.1 Prepare a wet film by uniformly dispersing the CNT-PAA solution using Doctor Blade casting or spin coating, and control the dry film thickness to be 25-50 μm.

[0046] S4.2. Dry the wet film under vacuum at 80 °C for 1 hour to remove the solvent and obtain a preliminary dry film.

[0047] S4.3, keep at 80℃ for 1 hour to remove residual solvent and bubbles.

[0048] S4.4, kept at 150℃ for 1 hour, initial imidization, TEA assists in ring closure.

[0049] S4.5, 200℃ for 1 hour, further covalently integrates CNT with PAA / PI chain.

[0050] S4.6, held at 300℃ for 1 hour, complete imidization, forming a stable PI network, with CNTs fixed on the PI chain.

[0051] The innovation of this step is that stepwise thermal imidization not only completes the PAA→PI conversion, but also covalently fixes CNTs onto the PI chain to form a three-dimensional cross-linked covalent network, which significantly improves the interfacial bonding and overall performance of the composite film.

[0052] Post-processing and comprehensive performance characterization: Annealing at 200℃ for 1 hour was selected to eliminate internal stress. The film was cut, the thickness was homogenized, and it was dried and stored in the dark. Comprehensive characterization: The structure and function of the CNT-PI film were comprehensively evaluated by combining TEM, FTIR, and XPS performance tests.

[0053] FTIR characterization: Infrared spectroscopy analysis was performed on pure polyimide films, ungrafted carbon nanotube / polyimide composite films, and the grafted carbon nanotube / polyimide composite films prepared in this invention. The results are as follows: Figure 2 As shown. All three exhibit typical imide structure absorption bands. Compared with pure polyimide and ungrafted composite films, the grafted carbon nanotube / polyimide composite film shows the following structural changes: (1) The absorption of -NH / -OH near 3480 cm⁻¹ is significantly reduced, indicating that the amino groups on the surface of carbon nanotubes are partially consumed in the reaction. (2) The intensity of the imide C=O peaks at 1775 cm⁻¹ and 1711 cm⁻¹ decreases overall, and there is a slight peak shift, indicating that the local chemical environment of the imide has changed. (3) The absorptions at 1360–1380 cm⁻¹ (C–N) and 1230 cm⁻¹ (COC) are significantly weakened, which is consistent with the characteristics of the amidation / imine reaction between amino groups and PAA. (4) The overall intensity of the out-of-plane vibration region of the benzene ring decreases, reflecting that the PI chain segment is disturbed by the grafted CNTs. The aforementioned changes only appeared in the grafted sample and not in the ungrafted physically mixed sample, thus ruling out the influence of physical adsorption or simple mixing. Therefore, based on infrared spectroscopy analysis, it can be confirmed that the amino groups on the surface of the carbon nanotubes reacted chemically with the polyamic acid to form a covalent structure of amide or imide bonds, proving that the present invention has successfully grafted carbon nanotubes onto polyimide segments.

[0054] XPS characterization: According to the high-resolution XPS spectrum, new characteristic peaks appeared and shifted, proving the formation of amide bonds.

[0055] TEM characterization: such as Figures 3-6 As shown, carbon nanotubes exhibit aggregation and agglomeration, indicating that physical mixing cannot effectively disperse CNTs. Figure 7 , Figure 8As shown, CNTs are uniformly distributed in the PI matrix without obvious agglomeration, and the interfacial bonding is tight, indicating that CNTs have formed stable covalent bonds with the PI molecular chains through grafting, achieving high dispersibility. By comparing the TEM images of ungrafted and grafted CNT / PI, the advantages of the method of this invention in terms of dispersibility and interfacial bonding can be intuitively demonstrated, verifying the effectiveness of the "polar anchoring – in-situ polymerization – stepwise thermal imidization" strategy.

[0056] The innovation of this step is that the method of this invention realizes the controllable chemical grafting, in-situ polymerization integration and thermal imidization fixation of CNTs, which is different from the traditional physical doping or surface modification system, and achieves molecular-level dispersion and stable covalent interface.

[0057] This invention enables controllable covalent bonding between carbon nanotubes (CNTs) and PI segments at the molecular level, significantly improving the dispersion and interfacial bonding of CNTs in the PI matrix, thereby obtaining a composite film with excellent thermal conductivity, electromagnetic shielding performance, and mechanical properties.

Claims

1. A polyimide composite film with highly dispersed carbon nanotubes achieved through chemical anchoring, characterized in that, The composition includes aminated carbon nanotubes (CNT-NH2), diamine monomer 4,4′-diaminodiphenyl ether (ODA), pyromellitic dianhydride (PMDA), anhydrous dimethylacetamide (DMAc), triethylamine (TEA), and nitrogen gas. Specifically, CNT-NH2 has an outer diameter of 1-2 nm, a length of 5-30 μm, and a mass of 0.065-0.325 parts by weight; ODA has a purity ≥99% and a mass of 3.065 g parts by weight; PMDA has a purity ≥99% and a mass of 3.317-3.497 parts by weight; DMAc has a purity ≥99.8% and a volume of 30-40 parts by volume; and TEA has a purity ≥99% and a mass of 0.03 parts by weight.

2. The method for preparing a polyimide composite film with highly dispersed carbon nanotubes through chemical anchoring according to claim 1, characterized in that, Includes the following steps: S1. Aminated carbon nanotubes (CNT-NH2) were ultrasonically dispersed in anhydrous dimethylacetamide (DMAc) to obtain a stable dispersion. S2. Under ice bath conditions, pyromellitic dianhydride (PMDA) is slowly added dropwise to the stable dispersion, and triethylamine (TEA) is used as a single catalyst to help it react with CNT–NH2 to form CNT-NH-CO-PMDA anchor points. S3. Add diamine monomer 4,4′-diaminodiphenyl ether ODA and gradually add the remaining PMDA to carry out in-situ polymerization to generate CNT-PAA composite solution; S4. Prepare a wet film using casting or spin coating methods, and then perform stepwise thermal imidization at 80-300 °C to obtain a CNT / PI covalent composite film.

3. The method for preparing a polyimide composite film with highly dispersed carbon nanotubes through chemical anchoring according to claim 2, characterized in that, The specific steps of step S1 include: S1.

1. The aminated carbon nanotubes CNT-NH2 were dried under vacuum at 80 °C for 12 h to remove adsorbed moisture and ensure the surface amino activity. S1.2 Disperse the dry CNT-NH2 in 20 parts by volume of anhydrous dimethylacetamide DMAc, and add 0.03 parts by weight of triethylamine TEA as a catalyst; S1.

3. Under ice bath conditions of 0-5 ℃, use a probe to ultrasonically treat for 30 min to achieve a highly dispersed state of CNTs; S1.

4. Let stand for 10 minutes, and use TEM or SEM to check the uniformity of CNT dispersion to ensure that there is no obvious agglomeration.

4. The method for preparing a polyimide composite film with highly dispersed carbon nanotubes via chemical anchoring according to claim 3, characterized in that, The specific steps of step S2 include: S2.1 Dissolve PMDA in 2 parts by volume of DMAc and slowly add it dropwise to the CNT-NH2 suspension at a rate of 0.1 parts by volume / min to ensure that the anhydride groups are in uniform contact with the CNT surface; S2.

2. Stir at low temperature for 2 hours under TEA catalysis, then raise to room temperature and continue stirring for 1 hour to form CNT-NH-CO-PMDA anchor sites.

5. The method for preparing a polyimide composite film with highly dispersed carbon nanotubes via chemical anchoring according to claim 4, characterized in that, The specific steps of step S3 include: S3.1 Adding diamine monomer: Under nitrogen protection and stirring conditions, add diamine monomer 4,4′-diaminodiphenyl ether ODA to the dispersion obtained in step S2, and stir until fully dissolved; S3.2 Execute the stoichiometric compensation mechanism: Based on the amino content on the surface of the aminated carbon nanotubes CNT-NH2 and the amount of PMD molar consumed in forming chemical anchors in step S2, calculate and add the remaining pyromellitic dianhydride PMDA in portions for in-situ polymerization. S3.3, Viscosity and Chain Growth Control: Under the catalysis of triethylamine (TEA), polymerization was continued for 12-24 h. By monitoring and controlling the solution viscosity within the specified range, the PAA molecular chains were ensured to grow in situ on the CNT surface and form a high molecular weight interlocking network. S3.4, CNT surface anchors and PAA molecular chains form a preliminary stable network through covalent bonding.

6. The method for preparing a polyimide composite film with highly dispersed carbon nanotubes via chemical anchoring according to claim 5, characterized in that, The specific steps of step S4 include: S4.1 Prepare a wet film by casting or spin coating of a uniformly dispersed CNT-PAA solution using Doctor Blade casting or spin coating, and control the dry film thickness to be 25-50 μm; S4.

2. Dry the wet film under vacuum at 80 °C for 1 h to remove the solvent and obtain a preliminary dry film; S4.3, keep at 80℃ for 1 hour to remove residual solvent and bubbles; S4.4, kept at 150℃ for 1 hour, initial imidization, TEA assists in ring closure; S4.5, 200℃ for 1 hour, CNT and PAA / PI chain further covalently integrated; S4.6, held at 300℃ for 1 hour, complete imidization, forming a stable PI network, with CNTs fixed on the PI chain.

Images