Transparent high-strength all-polyimide nanocomposite film and preparation method thereof

Abstract

This invention provides a method for preparing a transparent, high-strength all-polyimide nanocomposite film, comprising: Step 1: dissolving soluble polyimide in a polar organic solvent to obtain a polyimide solution; Step 2: reacting an aromatic diamine and an aromatic dianhydride to obtain a polyamic acid solution; Step 3: using the polyimide solution as the outer fluid and the polyamic acid solution as the inner fluid, performing coaxial electrospinning to obtain a core-shell nanofiber membrane with a polyimide outer shell and a polyamic acid core, followed by heating to obtain a core-shell polyimide nanofiber membrane; Step 4: immersing the core-shell polyimide nanofiber membrane in a mixed organic solvent; Step 5: hot-pressing the immersed core-shell polyimide membrane and washing it to obtain a polyimide nanofiber composite membrane. The polyimide composite membrane prepared by this invention has a light transmittance higher than 85%, a nanofilling content of over 50%, and tensile strength and Young's modulus both increased by over 100%.

Description

Technical Field

[0001] This invention relates to the field of high-performance polymer materials, specifically to a transparent, high-strength all-polyimide nanocomposite film and its preparation method. Background Technology

[0002] Today, polymer-based composite materials, as advanced functional materials, are attracting increasing attention from researchers due to their superior bonding properties with organic components, such as flexibility, low dielectric properties, high breakdown strength, durability, and ultra-high thermal stability. Among them, polyimide (PI), as a typical engineering polymer material, has been widely used in recent years as an insulating material, in microelectronics, and even in aerospace and aircraft components due to its excellent electrical insulation, thermal properties, and chemical resistance. However, the relatively low mechanical properties of pure PI limit its application in some special applications.

[0003] To improve the mechanical properties of polysiloxane (PI), an effective method is to add nanofillers through strong interfacial interactions, such as hyperbranched polysiloxanes (NH2-HBPSi), carbon nanotubes (CNTs), graphene oxide (GO), and graphene nanoribbons (GNRs). However, it is currently impossible to add nanofillers in large quantities into the PI matrix, and there are still problems such as difficulty in uniform dispersion and high cost, making large-scale industrialization difficult for most studies. Another effective strategy is to modify the structure by introducing heterocycles and hydrogen bonds to enhance intermolecular forces, but this method has complex synthetic routes, high costs, and low yields. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a transparent, high-strength polyimide nanocomposite film and its preparation method. The material contains a large number of nanoscale pores, and by controlling the volume ratio of polyimide to polyamic acid, the content of pores can be more controllable, resulting in a film with extremely low dielectric constant and high transparency.

[0005] This invention provides a method for preparing a transparent, high-strength all-polyimide nanocomposite film, comprising: Step 1: Dissolve soluble polyimide in a polar organic solvent to obtain a polyimide solution; Step 2: Add the aromatic diamine to a polar organic solvent. After the aromatic diamine dissolves, add the aromatic dianhydride to react and obtain a polyamic acid solution. Preferably, the reaction is carried out under an inert atmosphere and ice bath conditions, with a reaction temperature of 0-5°C and a reaction time of 6-12 hours.

[0006] Step 3: Using the polyimide solution as the outer diameter fluid and the polyamic acid solution as the inner diameter fluid, coaxial electrospinning is performed. This yields a core-shell nanofiber membrane without beads, with a smooth fiber surface and uniform fiber diameter. The outer shell is polyimide, and the core material is polyamic acid. The membrane is then heated to thermally imidize the polyamic acid, resulting in a core-shell polyimide nanofiber membrane. The thermal imidization process includes five stages: the temperature of the first stage is 80~110℃, the temperature of the second stage is 110~130℃, the temperature of the third stage is 150~180℃, the temperature of the fourth stage is 210~240℃, and the temperature of the fifth stage is 290~320℃. The holding time for each stage is independently 30~120 min.

[0007] Step 4: Immerse the core-shell polyimide nanofiber membrane in a mixed organic solvent. The mixed organic solvent is used to adjust the solubility and selectively dissolve the outer shell portion of the core-shell polyimide nanofiber membrane with a large specific surface area in a confined space.

[0008] Step 5: The soaked core-shell polyimide nanofiber membrane is hot-pressed and washed to obtain a fully polyimide nanofiber composite membrane. During the hot-pressing process, the dissolved portion of the outer layer serves as the filling phase, and the undissolved portion of the inner layer serves as the supporting phase. Preferably, the hot-pressing temperature is 60~180℃, the pressure is 0~4MPa, and the hot-pressing time is 10~60min. Preferably, the washing process adopts an immersion method, the immersion solution is one or more of water and ethanol, and the immersion time is 12~48h.

[0009] Further, in step 1, the polar organic solvent includes one or more of dichloromethane, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, ethanol, acetone, toluene, amyl acetate, dimethyl sulfoxide, and chloroform, and the mass fraction of the soluble polyimide solution is 10-30 wt%. Preferably, the organic solvent is N,N-dimethylacetamide.

[0010] Furthermore, in step 2, the aromatic diamine includes 4,4'-diaminodiphenyl ether.

[0011] Furthermore, in step 2, the aromatic dianhydride includes bisphenol A diether dianhydride.

[0012] Furthermore, in step 3, the ratio of the inner and outer diameter flow rates of the electrospinning is 1:1 to 1:10, the needle size is 15 to 26, the liquid flow rate is 0.1 to 3 mL / h, the receiving distance is 10 to 15 cm, the voltage is 10 to 25 Kv, the roller speed is 100 to 600 rpm, and the spinning time is 1 to 8 h.

[0013] Furthermore, in step 2, the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1.02. Preferably, the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1.

[0014] Further, in step 2, the polar organic solvent includes one or more of dichloromethane, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, ethanol, acetone, toluene, amyl acetate, dimethyl sulfoxide, and chloroform, and the polyamic acid solution has a mass fraction of 5-30 wt%. Preferably, the polyamic acid solution has a mass fraction of 12 wt%.

[0015] Furthermore, in step 3, the volume ratio of polyimide to polyamic acid is 1:4-1:2. Further still, in the coaxial electrospinning process, the ratio of inner to outer diameter flow rates is 1:1 to 1:10, the needle size is 15-26, the liquid flow rate is 0.2-3 mL / h, the receiving distance is 10-15 cm, the voltage is 10-25 Kv, and the roller speed is 100-600 rpm.

[0016] Further, in step 4, the mixed organic solvent includes a variety of dichloromethane, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, ethanol, acetone, toluene, amyl acetate, dimethyl sulfoxide, chloroform, and water, and the soaking time is 40 seconds to 10 minutes. Preferably, it is a 5 wt% ethanol solution of N,N-dimethylacetamide. Further still, in step 4, the mixed organic solvent is a mixture of DMAc and ethanol, wherein the mass percentage of DMAc is 2-50 wt%, preferably 5 wt%.

[0017] A transparent, high-strength polyimide nanocomposite film is obtained by any of the above preparation methods.

[0018] The beneficial effects of this invention are as follows: 1. This invention achieves self-fusion and self-reinforcement of nanofibers with a large specific surface area core-shell structure by selectively dissolving nanofibers within a confined space, thus successfully preparing a composite film that is transparent, high-strength, high-modulus, and highly nanofilled. Compared with traditional methods of adding nanomaterials, the composite film prepared by this method does not need to consider the problems of low addition amount, agglomeration, and uneven dispersion. The nanomaterial content can be added at the ideal level and uniformly dispersed, while solving the problem of interfacial compatibility. Compared with traditional electrospun nanofibers, this composite film overcomes the problems of opacity and structural defects, has high light transmittance (above 85%), and possesses excellent tensile strength (323.28 MPa) and Young's modulus (9.50±0.90 GPa).

[0019] 2. The composite film prepared by this invention makes up for the structural defects of electrospun fiber film. The externally dissolved fibers self-fusion and bond with the internal fibers, maintaining the orientation of the internal fibers. The good compatibility between the highly oriented polymer fibers and the matrix enables them to play a role in stress transmission and bridging during stretching or under stress, thereby significantly improving the mechanical properties of the material.

[0020] 3. In the preparation method of the present invention, since the outer shell is soluble and the core material is insoluble when preparing the core-shell polyimide nanofiber membrane, the dissolution range can be controlled during preparation, the preparation consistency is high, and nanomaterials can be directly added by coaxial electrospinning without complicated additional processing technology. The operation is simple and the nanomaterials can be added in a controlled manner, which is suitable for large-scale production. Attached Figure Description

[0021] Figure 1 These are photographs of PI-4-1 in Example 1, PI-2-1 in Example 2, PI-1 in Comparative Example 1, and PI-2 in Comparative Example 2; Figure 2 These are scanning electron microscope images of PI-4-1 from Example 1; Figure 3 These are scanning electron microscope images of PI-2-1 from Example 2; Figure 4 This is a scanning electron microscope image of PI-1 in Comparative Example 1; Figure 5 This is a scanning electron microscope image of PI-2 in Comparative Example 2; Figure 6 The transmittance spectra are those of PI-4-1 in Example 1, PI-2-1 in Example 2, PI-1 in Comparative Example 1, and PI-2 in Comparative Example 2. Figure 7 These are the stress-strain spectra of PI-1 in Comparative Example 1, PI-2 in Comparative Example 2, PI-4-1 in Example 1, and PI-2-1 in Example 2; Figure 8 The tensile strength spectra of PI-1 in Comparative Example 1, PI-2 in Comparative Example 2, PI-4-1 in Example 1, and PI-2-1 in Example 2 are shown. Figure 9 The Young's modulus spectra of PI-1 in Comparative Example 1, PI-2 in Comparative Example 2, PI-4-1 in Example 1, and PI-2-1 in Example 2 are shown. Figure 10 The infrared spectra of the core material polyimide in Examples 1 and 2 are shown. Detailed Implementation

[0022] The present invention is further illustrated below by means of examples and comparative examples. Unless otherwise specified, all pharmaceutical products used in the following examples are commercially available products, and all methods used are conventional methods in the art.

[0023] Example 1 A method for preparing a transparent, high-strength all-polyimide nanocomposite film includes the following steps: (1) Preparation of polyimide solution Weigh 4.05 g of soluble polyimide powder (molecular weight 2~10 w), add 11.95 g of N,N-dimethylacetamide, and after it is completely dissolved by stirring, continue to stir thoroughly at room temperature for 12 h to obtain a polyimide solution.

[0024] (2) Preparation of polyamic acid solution Under ice bath and nitrogen conditions, 5 mmol of 4,4'-diaminodiphenyl ether was added to a three-necked flask, followed by N,N-dimethylacetamide. After the diamine monomer was completely dissolved, 5 mmol of bisphenol A diether dianhydride was added. After stirring to dissolve, the mixture was stirred thoroughly at low temperature for 6 h to obtain a 12 wt% polyamic acid solution.

[0025] (3) Preparation of core-shell polyimide nanofiber films Pour polyimide solution into a 20mL syringe for use in the outer diameter spinning solution. The electrospinning process parameters used are: voltage 14 KV, dispensing speed 0.20 mL / h, needle size 17, receiving distance 12 cm, and roller speed 200 rpm. Pour polyamic acid solution into a 20mL syringe for use in the inner diameter spinning solution. The electrospinning process parameters used are: voltage 14 KV, dispensing speed 0.80 mL / h, needle size 23, receiving distance 11 cm, and roller speed 200 rpm. At rpm, the fibers ejected from the needle are collected onto aluminum foil to obtain a core-shell nanofiber membrane. The outer shell is polyimide, and the core material is polyamic acid. The volume ratio of polyimide to polyamic acid is 1:4. The core-shell nanofiber membrane is then subjected to programmed thermal imidization. The thermal imidization process is as follows: heat treatment at 80℃ for 1 hour, at 120℃ for 1 hour, at 180℃ for 1 hour, at 240℃ for 2 hours, and at 300℃ for 1 hour to obtain a core-shell polyimide nanofiber membrane.

[0026] (4) Selective dissolution of core-shell polyimide nanofiber membranes The above-mentioned core-shell polyimide nanofiber membrane was immersed in a mixed solvent of DMAc and C2H5OH, wherein the mass percentage of DMAc was 5 wt%, and the immersion time was 40 s. The immersed core-shell polyimide nanofiber membrane was then placed on a polytetrafluoroethylene membrane, and the C2H5OH was allowed to evaporate.

[0027] (5) Preparation of polyimide nanocomposite film The volatilized core-shell polyimide nanofiber membrane was placed between two layers of polytetrafluoroethylene membrane, preheated at 130°C for 35 min, and then subjected to a pressure of 1 MPa for 10 min. This yielded a fully polyimide nanocomposite membrane.

[0028] (6) Solvent removal by polyimide nanocomposite membrane The above-mentioned polyimide nanocomposite film was soaked in 1L of water for 12h, and then the soaked polyimide nanocomposite film was placed in an oven and dried in a vacuum environment at 80℃ for 8h to remove the residual solvent, thus obtaining a full polyimide nanocomposite film, named PI-4-1.

[0029] Example 2 (1) Preparation of polyimide solution Weigh 4.05 g of soluble polyimide powder (molecular weight 2~10 w), add 11.95 g of N,N-dimethylacetamide, and after it is completely dissolved by stirring, continue to stir thoroughly at room temperature for 12 h to obtain a polyimide solution.

[0030] (2) Preparation of polyamic acid solution Under ice bath and nitrogen atmosphere conditions, 5 mmol of 4,4'-diaminodiphenyl ether was added to a three-necked flask, followed by N,N-dimethylacetamide. After the diamine monomer was completely dissolved, 5 mmol of bisphenol A diether dianhydride was added. After stirring to dissolve, the mixture was stirred thoroughly at low temperature for 6 h to obtain a 12 wt% polyamic acid solution.

[0031] (3) Preparation of core-shell polyimide nanofiber films Pour polyimide solution into a 20mL syringe for use as the outer diameter spinning solution. The electrospinning process parameters used are: voltage 14 KV, dispensing speed 0.20 mL / h, needle size 17, receiving distance 12 cm, and roller speed 200 rpm. Pour polyamic acid solution into a 20mL syringe for use as the inner diameter spinning solution. The electrospinning process parameters used are: voltage 14 KV, dispensing speed 0.40 mL / h, needle size 23, receiving distance 10 cm, and roller speed 200 rpm. At rpm, the fibers ejected from the needle are collected onto aluminum foil to obtain a core-shell nanofiber membrane. The outer shell is polyimide, and the core material is polyamic acid. The volume ratio of polyimide to polyamic acid is 1:2. The core-shell nanofiber membrane is then subjected to programmed thermal imidization. The thermal imidization process is as follows: heat treatment at 80℃ for 1 hour, at 120℃ for 1 hour, at 180℃ for 1 hour, at 240℃ for 2 hours, and at 300℃ for 1 hour to obtain a core-shell polyimide nanofiber membrane.

[0032] (4) Selective dissolution of core-shell polyimide nanofiber membranes The above-mentioned core-shell polyimide nanofiber membrane was immersed in a mixed solvent of DMAc and C2H5OH, wherein the mass percentage of DMAc was 5 wt%, and the immersion time was 40 s. The immersed core-shell polyimide nanofiber membrane was then placed on a polytetrafluoroethylene membrane, and the C2H5OH was allowed to evaporate.

[0033] (5) Preparation of polyimide nanocomposite film The volatilized core-shell polyimide nanofiber membrane was placed between two layers of polytetrafluoroethylene membrane, preheated at 130°C for 35 min, and then subjected to a pressure of 1 MPa for 10 min. This yielded a fully polyimide nanocomposite membrane.

[0034] (6) Solvent removal by polyimide nanocomposite membrane The above-mentioned polyimide nanocomposite film was soaked in 1L of water for 12h, and then placed in an oven and dried in a vacuum environment at 80℃ for 8h to remove residual solvent, thus obtaining a full polyimide nanocomposite film, named PI-2-1.

[0035] Comparative Example 1 The polyimide solution prepared in step 1 of Example 1 was degassed under vacuum, and a film was cast onto a glass substrate using a casting method. The film was then placed in an oven and kept at 80°C for 1 hour, 120°C for 1 hour, and 180°C for 1 hour to obtain a yellow transparent polyimide film, named PI-1.

[0036] Comparative Example 2 The polyamic acid solution prepared in step 2 of Example 1 was degassed under vacuum, and a film was cast onto a glass substrate using a casting method. The film was then placed in an oven and kept at 80°C for 1 hour, 120°C for 1 hour, 180°C for 1 hour, 240°C for 2 hours, and 300°C for 1 hour to obtain a colorless and transparent polyimide film, named PI-2.

[0037] Explanation of the principle: By adjusting the proportion of mixed organic solvents, the outer shell of the core-shell polyimide nanofibers after coaxial electrospinning is selectively dissolved. The dissolved portion serves as the filling phase, while the undissolved portion of the core material serves as the nano-support phase. Through hot pressing, more dissolved fibers fill the voids inside the membrane, reducing light scattering and improving the transparency of the film. At the same time, the presence of a large number of undissolved nanofibers in the film forms a nanofiber skeleton, and the good compatibility between the highly oriented polymer fibers and the matrix enables them to play a role in stress transfer and bridging during stretching or under stress, thereby significantly improving the mechanical properties of the material.

[0038] Furthermore, the core material of the core-shell polyimide nanofiber is insoluble polyimide, while the outer shell is soluble polyimide. When the solvent dissolves, only the outer shell is dissolved, and the core fiber is retained as the supporting phase, while the outer shell is used as the filling phase. The filling content can be controlled by the outer diameter flow rate, thereby achieving the purpose of controllable dissolution.

[0039] In the "Preparation of Core-Shell Polyimide Nanofiber Film" step in Examples 1 and 2, the core-shell nanofiber film was successfully obtained by undergoing programmed thermal imidization, as shown in the infrared spectrum. Figure 10 As shown, the chemical reaction equation for the core material polyamic acid is as follows: Polyimides can be obtained through different synthetic routes, such as one-step or two-step methods. Polyimides synthesized using the two-step method have lower solubility. Through heat treatment, polyamic acid is completely imidized to form polyimides, increasing the intermolecular interactions of polyimides and thus reducing their solubility. Therefore, in the "selective dissolution of core-shell polyimide nanofiber membranes," only the soluble polyimide of the outer shell dissolves, while the core polyimide remains undissolved.

[0040] Performance testing: Figure 1 These are photographs of PI-4-1 in Example 1, PI-2-1 in Example 2, PI-1 in Comparative Example 1, and PI-2 in Comparative Example 2. It can be seen that the treated polyimide nanocomposite film still maintains high transparency.

[0041] Figure 2-5 The images show scanning electron microscope (SEM) photographs of PI-4-1 in Example 1, PI-2-1 in Example 2, PI-1 in Comparative Example 1, and PI-2 in Comparative Example 2. As shown in the figures, the cross-sections of the PI-1 and PI-2 films show no obvious defects or pores. However, the number of pores gradually increases from PI-2-1 to PI-4-1. This is because as the content of soluble polyimide in the shell gradually decreases in the core-shell nanofiber membrane, the content of dissolved fibers decreases, making it increasingly difficult to completely fill the pores.

[0042] Figure 6 The transmittance spectra of PI-1 in Comparative Example 1, PI-2 in Comparative Example 2, PI-4-1 in Example 1, and PI-2-1 in Example 2 are shown in the figure. As shown, PI-2-1 and PI-4-1 also maintain high transparency (above 85%) compared to PI-1 and PI-2. This is because when a beam of light shines on the surface of the film, part of the incident light is reflected into the air, and part of the light entering the interior of the film is scattered due to the difference in refractive index between the nanofibers and the air in the pores. Most of the light can pass through the film, thus making the film exhibit high transparency.

[0043] Figure 7 The figures show the stress-strain spectra of PI-1 in Comparative Example 1, PI-2 in Comparative Example 2, PI-4-1 in Example 1, and PI-2-1 in Example 2. As shown in the figures, the strain of PI-4-1 is 323.28 MPa, and the strain of PI-2-1 is 225.11 MPa, which are 4.94 times and 3.44 times higher than PI-1, respectively, and 2.04 times and 1.42 times higher than PI-2, respectively. This is because the polyimide composite film contains a large number of undissolved nanofiber fillers. The fibers form a nano-network structure in the matrix material, which plays a role in stress transfer and bridging during tensile or stressed processes.

[0044] Figure 8 and Figure 9 The tensile strength and Young's modulus spectra of PI-1 in Comparative Example 1, PI-2 in Comparative Example 2, PI-4-1 in Example 1, and PI-2-1 in Example 2 are shown. The Young's modulus of PI-4-1 is 9.50 ± 0.90 GPa, and that of PI-2-1 is 5.98 ± 0.59 GPa, representing increases of 2.88 times and 1.81 times compared to PI-1, and increases of 4.60 times and 2.97 times compared to PI-2, respectively. This is because the polyimide composite film contains a large number of undissolved nanofiber fillers that act like reinforced concrete to support the material. Furthermore, the good compatibility between the highly oriented polymer fibers and the matrix allows them to play a role in stress transfer and bridging during tensile or stressed processes, thereby significantly improving the mechanical properties of the material.

[0045] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing a transparent high-strength all-polyimide nanocomposite film, characterized by, include: Step 1: Dissolve soluble polyimide in a polar organic solvent to obtain a polyimide solution; Step 2: Add the aromatic diamine to a polar organic solvent. After the aromatic diamine dissolves, add the aromatic dianhydride and react to obtain a polyamic acid solution. Step 3: Using the polyimide solution as the outer diameter fluid and the polyamic acid solution as the inner diameter fluid, coaxial electrospinning is performed to obtain a core-shell nanofiber membrane with a polyimide outer shell and a polyamic acid core. The membrane is then heated to obtain a core-shell polyimide nanofiber membrane. Step 4: Immerse the core-shell polyimide nanofiber membrane in a mixed organic solvent, which is a mixture of DMAc and ethanol, wherein the mass percentage of DMAc is 2~50 wt%, and the immersion time is 40s~10min. By adjusting the ratio of the mixed organic solvent, the outer shell of the coaxial electrospun core-shell polyimide nanofiber is selectively dissolved. The dissolved part is used as the filling phase, and the undissolved part of the core material is used as the nano-support phase. Step 5: The soaked core-shell polyimide nanofiber membrane is hot-pressed. The dissolved polyimide fibers fill the voids inside the membrane as a filling phase, while polyamic acid forms a nanofiber skeleton as a nano-supporting phase. After washing, a full polyimide nanofiber composite membrane is obtained.

2. The method for preparing a transparent, high-strength all-polyimide nanocomposite film according to claim 1, characterized in that: In step 1, the polar organic solvent includes one or more of dichloromethane, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, ethanol, acetone, toluene, amyl acetate, dimethyl sulfoxide, and chloroform, and the mass fraction of the soluble polyimide solution is 10~30wt%.

3. The method for preparing a transparent, high-strength all-polyimide nanocomposite film according to claim 1, characterized in that: In step 2, the aromatic diamine is 4,4'-diaminodiphenyl ether, and the aromatic dianhydride is bisphenol A diether dianhydride.

4. The method for preparing a transparent, high-strength all-polyimide nanocomposite film according to claim 1, characterized in that: In step 3, the ratio of the inner and outer diameter flow rates of the electrospinning is 1:1 to 1:10, the needle size is 15 to 26, the liquid flow rate is 0.1 to 3 mL / h, the receiving distance is 10 to 15 cm, the voltage is 10 to 25 Kv, the roller speed is 100 to 600 rpm, and the spinning time is 1 to 8 h.

5. The method for preparing a transparent high-strength all-polyimide nanocomposite film according to claim 1, characterized in that: In step 2, the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1 to 1:1.

02.

6. The method for preparing a transparent, high-strength all-polyimide nanocomposite film according to claim 1, characterized in that: In step 2, the polar organic solvent includes one or more of dichloromethane, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, ethanol, acetone, toluene, amyl acetate, dimethyl sulfoxide, and chloroform, and the polyamic acid solution has a mass fraction of 5-30 wt%.

7. The method for preparing a transparent high-strength all-polyimide nanocomposite film according to claim 1, characterized in that: In step 3, the volume ratio of polyimide to polyamic acid is 1:4 to 1:

2.

8. A transparent high-strength all-polyimide nanocomposite film, characterized by: It is obtained by any one of the preparation methods in claims 1-7.

Images