Flexible polyimide film, method for preparing the same, and use thereof

Abstract

The present application relates to the technical field of sensor, in particular to a flexible polyimide film, a preparation method and application thereof. The flexible polyimide film is mainly prepared by polycondensation and imidization of diamine and dianhydride; the diamine includes aliphatic diamine with carbon number of 6-12 and aromatic diamine with molar ratio of 1:(0.5-2); and the dianhydride includes aromatic dianhydride. In the flexible polyimide film, long-chain aliphatic diamine structure with certain length is introduced into the structure by polycondensation, and the molar ratio of aliphatic diamine and aromatic diamine is controlled, so that the polyimide is endowed with good flexibility and mechanical strength, thereby better adapting to the performance requirements of the flexible substrate of electronic skin.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a flexible polyimide film, its preparation method, and its application. Background Technology

[0002] As a biomimetic sensor system that mimics the sensory functions of human skin, electronic skin has attracted widespread attention in recent years. It can sense various signals from the physical world in real time and convert them into electrical signals for output, while also possessing excellent environmental adaptability, such as superior flexibility and mechanical stability. Based on these characteristics, electronic skin has shown broad application prospects in fields such as humanoid robots, medical health monitoring, and wearable devices.

[0003] Electronic skin structures typically consist of three parts: a flexible substrate, active materials, and electrodes. The flexible substrate not only needs good tensile and ductile properties but also requires a certain level of thermal and mechanical stability. Currently, commonly used flexible substrates can be mainly classified into elastomers, films, and hydrogels. Polydimethylsiloxane (PDMS) has become one of the most widely used flexible substrates due to its excellent flexibility, tensile strength, and corrosion resistance. With further research, polyimide (PI) has gradually been recognized as a preferred substrate for flexible electronic skin. The aromatic rings in the polyimide molecule endow it with excellent mechanical properties and thermal stability; however, its application as a flexible substrate still faces some challenges. Traditional polyimide backbones have a rigid structure and strong intermolecular forces, resulting in poor solubility, which is detrimental to subsequent processing and molding. Simultaneously, this also leads to insufficient flexibility and deformation capabilities in the final product, limiting its further application in the field of electronic skin. Therefore, researchers have conducted extensive work on the structural design and synthesis methods of polyimide.

[0004] Chinese patent application CN113583443A discloses a transparent polyimide for flexible optoelectronics, which improves polymer solubility by introducing a fluorinated m-terphenyl structure. Chinese patent application CN113527683A discloses a polyimide that improves solubility by introducing trifluoromethyl and allyl ether substitutes into its structure. Chinese patent application CN105601923A discloses a fluorinated soft-hard block polyimide film, prepared by the polycondensation reaction of a flexible fluorinated aromatic diamine with a rigid aromatic dianhydride, imparting a certain degree of flexibility, but with limited improvement. Therefore, currently prepared polyimide films still face some challenges in balancing flexibility and mechanical strength, requiring further research to improve their overall performance.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide flexible polyimide films, their preparation methods, and applications. In the flexible polyimide film of this invention, a long-chain aliphatic diamine structure of a certain length is introduced into the structure through polycondensation, while the molar ratio of aliphatic diamine and aromatic diamine is controlled to endow the polyimide with good flexibility and mechanical strength, thereby making it better suited to the performance requirements of flexible electronic skin substrates.

[0007] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides a flexible polyimide film, which is mainly prepared by polycondensation and imidization of diamine and dianhydride; wherein the diamine includes aliphatic diamines and aromatic diamines having 6 to 12 carbon atoms in a molar ratio of 1:(0.5 to 2); and the dianhydride includes aromatic dianhydrides.

[0008] In a specific embodiment of the present invention, the aromatic diamine includes at least one of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminobiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodibenzophenone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 2,5-diaminotrifluorotoluene, 2,2-bis(4-aminophenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene, preferably 2,2'-bis(trifluoromethyl)diaminobiphenyl.

[0009] In a specific embodiment of the present invention, the aliphatic diamine having 6 to 12 carbon atoms includes 1,12-dodecaneamine.

[0010] In a specific embodiment of the present invention, the aromatic dianhydride includes at least one of pyromellitic dianhydride, biphenyl dianhydride, 3,3,4,4-benzophenone tetracarboxylic dianhydride, 4,4'-oxophthalic anhydride, 4,4',5,5'-dioxophthalic anhydride, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, and bisphenol A type diether dianhydride, preferably 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride.

[0011] In a specific embodiment of the present invention, the molar ratio of the diamine to the dianhydride is 1:(0.95 to 1.05).

[0012] The second aspect of this invention provides a method for preparing the flexible polyimide film of the first aspect of this invention, comprising the following steps:

[0013] (a) Aliphatic diamines with 6 to 12 carbon atoms and aromatic diamines are mixed evenly in a solvent, and then dianhydride is added. Polycondensation reaction is carried out under a protective atmosphere to obtain a polyamic acid solution.

[0014] (b) The polyamic acid solution is formed into a film and then imidized; or, the polyamic acid solution is imidized and then formed into a film.

[0015] In a specific embodiment of the present invention, in step (a), the solvent includes at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide.

[0016] In a specific embodiment of the present invention, the imidization is carried out under the action of a catalyst and a dehydrating agent. Further, the catalyst includes at least one selected from pyridine, methylpyridine, 1-methylimidazole, 1,2-dimethylimidazole, quinoline, isoquinoline, 2-methylimidazole, and dimethylaminopyridine; the dehydrating agent includes at least one selected from acetic anhydride, trifluoroacetic anhydride, propionic anhydride, butyric anhydride, and benzoic anhydride.

[0017] The third aspect of the present invention also provides the application of the flexible polyimide film provided in the first aspect of the present invention in the preparation of electronic skin.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] In the flexible polyimide film of the present invention, the flexibility of the polyimide film is significantly enhanced by introducing a long-chain aliphatic diamine structure into the polyimide backbone, thereby improving its performance as a flexible substrate. In addition, the introduction of large sterically hindered groups (such as -CF3) into the polyimide structure can improve the solubility of the resin, creating favorable conditions for the subsequent processing and molding of the polyimide film. By controlling the molar ratio of aliphatic diamine and aromatic diamine, a good balance between flexibility and mechanical strength is achieved in the polyimide. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the structure of the flexible electronic skin provided in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the synthetic route for preparing polyimide in Example 1 of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0024] The first aspect of the present invention provides a flexible polyimide film, which is mainly prepared by polycondensation and imidization of diamine and dianhydride; the diamine includes aliphatic diamines and aromatic diamines with 6 to 12 carbon atoms in a molar ratio of 1:(0.5 to 2); the dianhydride includes aromatic dianhydrides.

[0025] In the flexible polyimide film of the present invention, the flexibility of the polyimide film is significantly enhanced by introducing a long-chain aliphatic diamine structure into the polyimide backbone, thereby improving its performance as a flexible substrate. In addition, the introduction of large steric hindrance groups (such as -CF3) into the polyimide structure can improve the solubility of the resin, creating favorable conditions for the subsequent processing and molding of the polyimide film.

[0026] In some embodiments, the molar ratio of aliphatic diamines with 6 to 12 carbon atoms to aromatic diamines in the diamine is 1:(0.5 to 2), specifically 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, or any combination thereof. By adjusting the molar ratio of aliphatic diamines to aromatic diamines, a good balance between flexibility and mechanical strength is achieved in the polyimide. When the amount of aliphatic diamines with 6 to 12 carbon atoms is too low, the improvement in the flexibility of the polyimide is not significant; when the amount of aliphatic diamines with 6 to 12 carbon atoms is too high, the solubility of the polyimide is insufficient, making it difficult to meet the requirements for processing and molding.

[0027] In some embodiments, the aliphatic diamine having 6 to 12 carbon atoms can specifically be a range of 6, 8, 9, 10, 12, or any combination thereof. Further, the aliphatic diamine having 6 to 12 carbon atoms includes 1,12-dodecaneamine.

[0028] In some embodiments, the aromatic diamine includes at least one selected from p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-diaminobiphenyl (BDA), 4,4'-diamino-3,3'-dimethylbiphenyl (DBDA), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenyl ether (DDE), 4,4'-diaminobenzophenone (DABP), 4,4'-diaminodiphenyl sulfone (DDS), 3,3'-diaminodiphenyl sulfone (SDA), 2,5-diaminotrifluorotoluene (DABTF), 2,2-bis(4-aminophenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene (APB), preferably 2,2'-bis(trifluoromethyl)diaminobiphenyl.

[0029] In some embodiments, the diamine comprises 1,12-dodecaneamine and 2,2'-bis(trifluoromethyl)diaminobiphenyl in a molar ratio of 1:1.

[0030] In some embodiments, the aromatic dianhydride includes at least one of pyromellitic dianhydride (PMDA), biphenyl dianhydride (BPDA), 3,3,4,4-benzophenone tetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic anhydride (ODPA), 4,4',5,5'-dioxydiphthalic anhydride (DODPA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA), and bisphenol A type diether dianhydride (BPADA), preferably 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride.

[0031] In some embodiments, the molar ratio of diamine to dianhydride is 1:(0.95 to 1.05), preferably 1:1.

[0032] In some embodiments, the polyimide film of the present invention has a structure as shown in Formula I:

[0033] (I);

[0034] Wherein, R1 is the residue after the condensation reaction of the dianhydride structure; R2 is the residue after the condensation reaction of the aromatic diamine; n is an integer between 3 and 6, and the ratio of x to y is 0.5 to 2.

[0035] R1 includes at least one of the following structures:

[0036]

[0037] R2 includes at least one of the following structures:

[0038]

[0039] The second aspect of this invention provides a method for preparing the flexible polyimide film of the first aspect of this invention, comprising the following steps:

[0040] (a) Aliphatic diamines with 6 to 12 carbon atoms and aromatic diamines are mixed evenly in a solvent, and then dianhydride is added. Polycondensation reaction is carried out under a protective atmosphere to obtain a polyamic acid solution.

[0041] (b) The polyamic acid solution is made into a film and then imidized; or, the polyamic acid solution is imidized and then made into a film.

[0042] In some embodiments, in step (a), the solvent includes at least one selected from N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO). Further, in step (a), the mass ratio of the aliphatic diamine, aromatic diamine, and dianhydride having 6 to 12 carbon atoms to the mass ratio of the solvent is (5 to 20):(80 to 95).

[0043] In some embodiments, the polycondensation reaction under a protective atmosphere includes: stirring the reaction at 0–5°C for 1–1.5 h under a nitrogen atmosphere, and then stirring the reaction at room temperature for 24–30 h.

[0044] In some embodiments, the method of forming the film in step (b) is not limited, and may specifically include: coating a polyamic acid solution or an imidized solution to obtain a wet film, and drying to obtain the film.

[0045] In some embodiments, in step (b), the imidization method includes thermal imidization and / or chemical imidization. Thermal imidization refers to completing the imidization reaction in a high-temperature oven. Chemical imidization refers to completing preliminary imidization with the action of a catalyst and a dehydrating agent, followed by drying, and then completing imidization in an oven.

[0046] In some embodiments, imidization is carried out in the presence of a catalyst and a dehydrating agent. Further, the catalyst includes at least one selected from pyridine, methylpyridine, 1-methylimidazole, 1,2-dimethylimidazole, quinoline, isoquinoline, 2-methylimidazole, and dimethylaminopyridine; the dehydrating agent includes at least one selected from acetic anhydride, trifluoroacetic anhydride, propionic anhydride, butyric anhydride, and benzoic anhydride.

[0047] In some embodiments, the number of moles of catalyst is 2 to 5 times the number of moles of dianhydride used in preparing the polyamic acid solution; the number of moles of dehydrating agent is 2 to 5 times the number of moles of dianhydride used in preparing the polyamic acid solution.

[0048] In some embodiments, step (b) of imidizing the polyamic acid solution to form a film includes: adding a catalyst and a dehydrating agent to the polyamic acid solution, stirring the reaction at room temperature for 10–15 h, then pouring the solution into deionized water to precipitate the polyimide, filtering and washing to collect the solid polyimide and drying it; dissolving the polyimide in a solvent and then coating it to obtain a wet film; and drying the wet film in a vacuum drying oven to obtain a polyimide film. Further, the drying process includes: drying at 80–90°C for 8–12 h, then raising the temperature to 120–130°C for 1–2 h, and then raising the temperature to 170–180°C for 1–2 h.

[0049] In some embodiments, when dissolving polyimide with a solvent, the type of solvent used is the same as that used in step (a), and will not be repeated here. Further, when dissolving polyimide with a solvent, a slurry with a polyimide mass fraction of 5% to 20% is obtained.

[0050] The third aspect of the present invention also provides the application of the flexible polyimide film provided in the first aspect of the present invention in the preparation of electronic skin.

[0051] Figure 1 This is a schematic diagram of the structure of the flexible electronic skin provided in an embodiment of the present invention. The electronic skin includes a stacked encapsulation layer, a flexible polyimide substrate layer, an rGO-CNT electrode, a nano-silver conductive film, and an encapsulation layer.

[0052] Example 1

[0053] This embodiment provides a method for preparing a flexible polyimide film. A schematic diagram of the polyimide synthesis route is shown below. Figure 2 Specifically, it includes the following steps:

[0054] (1) Add an appropriate amount of DMAc to a two-necked round-bottom flask, then add 5 mmol of 1,12-dodecaneamine and 5 mmol of 2,2'-bis(trifluoromethyl)diaminobiphenyl, and stir the mixture at room temperature until the solution is clear. Then add 10 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, and stir at 0°C for 1 h under a nitrogen atmosphere, then stir at room temperature for 24 h to obtain a polyamic acid solution. Add 25 mmol of pyridine and 25 mmol of acetic anhydride to the polyamic acid solution, mix and stir at room temperature for 10 h, then pour the mixed solution into deionized water to precipitate, filter, collect the solid, wash with ethanol, and dry for later use.

[0055] (2) Dissolve the dried polyimide from step (1) in solvent DMAc, and sonicate the solution for 30 minutes to remove bubbles. First, place the solution in an oven to evaporate to a solid content of about 40%, then transfer the solution to a clean glass plate and obtain a wet film on a vacuum adsorption coating machine. Place the glass plate coated with the wet film in a vacuum drying oven, first dry at 80℃ for 10 hours, then raise the temperature to 120℃ for 2 hours, and finally dry at 180℃ for 2 hours to obtain a polyimide film with a dry film thickness of 30±5μm, named PI-12-1: the first number 12 in the simplified formula represents the number of carbon atoms in the aliphatic diamine, with a value of 2. n ,at this time n =6; the second number 1 indicates the molar ratio of aliphatic diamine to aromatic diamine. x / y (The same applies below), its structure is as follows:

[0056]

[0057] Example 2 group

[0058] The preparation method of the flexible polyimide film in this embodiment group is the same as that in Example 1, except that the type of aliphatic diamine used in step (1) is different, as follows:

[0059] Example 2a: An equimolar amount of 1,6-diaminohexane was used to replace 1,12-dodecaneamine in Example 1; the resulting polyimide film is abbreviated as PI-6-1 ( n =3);

[0060] Example 2b: An equimolar amount of 1,8-diaminooctane was used to replace 1,12-dodecaneamine in Example 1; the resulting polyimide film is abbreviated as PI-8-1 ( n =4);

[0061] Example 2c: An equimolar amount of 1,10-diaminodecane was used to replace 1,12-dodecaneamine in Example 1; the resulting polyimide film is abbreviated as PI-10-1 ( n =5);

[0062] The structural formula of the polyimide film prepared in this embodiment is as follows:

[0063]

[0064] Example 3 Group

[0065] The preparation method of the flexible polyimide film in this embodiment group is the same as that in Example 1, except that the amounts of 2,2'-bis(trifluoromethyl)diaminobiphenyl and 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride used in step (1) are different, as are the amounts of pyridine and acetic anhydride. The specific differences are as follows:

[0066] Example 3a: The amount of 2,2'-bis(trifluoromethyl)diaminobiphenyl was 2.5 mmol, the amount of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride was 7.5 mmol, pyridine was 18.75 mmol, and acetic anhydride was 18.75 mmol; the resulting polyimide film is abbreviated as PI-12-2 ( n =6);

[0067] Example 3b: The amount of 2,2'-bis(trifluoromethyl)diaminobiphenyl was 10 mmol, the amount of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride was 15 mmol, pyridine was 37.5 mmol, and acetic anhydride was 37.5 mmol; the resulting polyimide film is abbreviated as PI-12-0.5 ( n =6);

[0068] The structural formula of the polyimide film prepared in this embodiment is as follows:

[0069]

[0070] Example 4

[0071] This embodiment refers to the preparation method of the flexible polyimide film in Example 1, the only difference being that: in step (1), an equimolar amount of o-toluidine is used to replace 2,2'-bis(trifluoromethyl)diaminobiphenyl in Example 1; the obtained polyimide film is abbreviated as PI-12-1-CH3, and its structural formula is as follows:

[0072]

[0073] Comparative Example 1

[0074] The comparative example group refers to the preparation method of the flexible polyimide film in Example 1, except that the type and / or amount of diamine used in step (1) are different, as follows:

[0075] Comparative Example 1a: 10 mmol of 1,12-dodecaneamine was used, without the addition of 2,2'-bis(trifluoromethyl)diaminobiphenyl; the resulting polyimide film is referred to as PI-12.

[0076] Comparative Example 1b: 10 mmol of 2,2'-bis(trifluoromethyl)diaminobiphenyl was used, without the addition of 1,12-dodecaneamine; the resulting polyimide film is referred to as PI-0.

[0077] The structural formula of the polyimide film prepared in this comparative example is as follows:

[0078]

[0079] Experimental Example

[0080] The polyimide films prepared in different embodiments and comparative examples were tested as follows, and the test results are shown in Table 1.

[0081] (1) Tensile properties: The tensile test of the polyimide film was performed using a high and low temperature electronic tensile testing machine. The test was conducted at room temperature and ambient humidity (50% relative humidity). The collected data included elongation at break, tensile strength, and modulus of elasticity. The test sample was prepared in a dumbbell shape with a usable central dimension of 40mm × 10mm. The tensile speed was 1mm / min. Among them, the modulus of elasticity ( E The stress in the elastic stage ( σ ) and strain ( ε The curve is obtained by calculating the slope of the elastic stage curve through linear fitting, i.e., E=(Δ σ ) / (Δ ε ).

[0082] (2) Solubility: The solubility of polyimide films was evaluated using common polar solvents, including DMAc, DMF, NMP and DMSO. Samples measuring 4cm × 4cm were placed in 50mL beakers, 10mL of solvent was added, and the mixture was stirred at room temperature for 24 hours. The dissolution status was observed at regular intervals. (where +++, ++, +, and ± represent different complete dissolution times t, respectively: +++ means t≤1h; ++ means 1h<t≤6h; + means 6h<t≤12h; ± means 12h<t≤24h).

[0083] Table 1. Performance test results of polyimide films

[0084]

[0085] The test results above show that introducing long-chain aliphatic diamine structures into the polyimide backbone enhances the flexibility and ductility of the polyimide, reflected in the tensile test results as a decrease in tensile strength and an increase in elongation at break. Therefore, the polyimide film of this invention can optimize its properties by introducing long-chain aliphatic diamines and controlling the molar ratio of aliphatic and aromatic diamines, thereby achieving a film that simultaneously possesses high mechanical strength and good ductility. This allows for applications in humanoid robots, medical testing, flexible displays, and particularly in the field of electronic skin.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible polyimide film, characterized by, is prepared mainly by polycondensation and imidization of diamines and dianhydrides; the diamines include 1,12-dodecanediamine and aromatic diamine in a molar ratio of 1:(0.8-1.2); the dianhydride is 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride; the aromatic diamine is 2,2'-bis(trifluoromethyl)diaminobiphenyl; the preparation method of the flexible polyimide film comprises: (a) mixing 1,12-dodecanediamine and aromatic diamine uniformly in a solvent, then adding dianhydride, and obtaining a polyamic acid solution by polycondensation reaction under a protective atmosphere; (b) preparing a film after imidization of the polyamic acid solution.

2. The flexible polyimide film according to claim 1, wherein The molar ratio of the diamines to the dianhydrides is 1:(0.95-1.05).

3. The method of producing the flexible polyimide film according to any one of claims 1 to 2, characterized by, comprises the following steps: (a) mixing 1,12-dodecanediamine and aromatic diamine uniformly in a solvent, then adding dianhydride, and obtaining a polyamic acid solution by polycondensation reaction under a protective atmosphere; (b) preparing a film after imidization of the polyamic acid solution.

4. The production method according to claim 3, characterized by, In step (a), the solvent comprises at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide.

5. The preparation method according to claim 3, characterized in that, The imidization is carried out under the action of a catalyst and a dehydrating agent.

6. The production method according to claim 5, wherein The catalyst comprises at least one of pyridine, methylpyridine, 1-methylimidazole, 1,2-dimethylimidazole, quinoline, isoquinoline, 2-methylimidazole and dimethylaminopyridine; and the dehydrating agent comprises at least one of acetic anhydride, trifluoroacetic anhydride, propionic anhydride, butyric anhydride and benzoic anhydride.

7. Use of the flexible polyimide film according to any one of claims 1-2 or the flexible polyimide film prepared by the preparation method according to any one of claims 3-6 in the preparation of electronic skin.

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