A polyimide polymer and its preparation method, a polyimide film and its applications

Abstract

This invention discloses a polyimide polymer, its preparation method, a polyimide film, and its applications. The polyimide polymer has the structure shown in Formula I. The polyimide film formed from this polymer exhibits high transparency and a low dielectric constant, while also maintaining the excellent thermal and mechanical properties of the polyimide film. It has broad application prospects in the fields of liquid crystal display materials, integrated circuits, and microelectronics.

Description

Technical Field

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

[0002] Polyimide (PI) films possess excellent thermal stability, chemical resistance, and good mechanical and electrical properties, making them important polymers in advanced liquid crystal display technology, integrated circuits, and the microelectronics industry. With the rapid development of these technologies, higher performance requirements are being placed on PI films. For example, the development of 5G communication technology demands PI materials with lower dielectric constants. In the liquid crystal display field, PI alignment films require stable pretilt angles for liquid crystal molecules, along with high-temperature resistance and good transparency. High-frequency, high-speed, ultra-large-scale integrated circuits require PI films with lower dielectric constants and dielectric losses to reduce signal transmission delays and crosstalk, achieving efficient signal transmission. Optoelectronic devices require PI films with excellent heat resistance and low coefficients of thermal expansion to meet the requirements of electrode deposition and annealing processes.

[0003] Traditional PI films, due to their electronic conjugated structure and the formation of intramolecular and intermolecular charge transfer complexes (CTCs), typically exhibit high dielectric constants, low transparency, and poor solubility in organic solvents, failing to meet the aforementioned industrial requirements.

[0004] Therefore, it is crucial to develop PI films that simultaneously possess high transparency, high heat resistance, high mechanical properties, low dielectric constant, and solubility. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, a first aspect of this invention provides a polyimide polymer. A polyimide film formed from this polyimide polymer exhibits high transparency and a low dielectric constant; simultaneously, it retains the excellent thermal and mechanical properties of the polyimide film.

[0006] A second aspect of the present invention also provides a method for preparing a polyimide polymer.

[0007] A third aspect of the present invention also provides a polyimide film.

[0008] A fourth aspect of the present invention also provides a method for preparing a polyimide film.

[0009] The fifth aspect of the present invention also provides an application of a polyimide film.

[0010] The polyimide polymer provided according to a first aspect of the present invention has the structure shown in Formula I:

[0011]

[0012] Where m and n are each independently selected from any integer from 10 to 100;

[0013] R 1 Selected from H, C 1～3 Alkyl groups;

[0014] R 2 Selected from

[0015] R 3 Selected from Where X is selected from any integer from 0 to 15.

[0016] The polyimide polymer according to embodiments of the present invention has at least the following beneficial effects:

[0017] The polyimide (PI) polymer of this invention incorporates alkyl chains in its structural formula. The rigid benzimidazole structure within the PI backbone imparts excellent thermal and mechanical properties. Furthermore, the introduction of alkyl chains and the presence of bulky fluorenyl Cardo structures significantly reduce the molecular chain packing density, backbone orientation, and the formation of charge transfer complexes (CTCs), thereby improving the dielectric constant, transmittance, and solubility of the PI film. This results in broad application prospects in liquid crystal displays, integrated circuits, and microelectronics.

[0018] According to a preferred embodiment of the present invention, m and n are each independently selected from any integer from 10 to 100, such as including 10, 20, 30, 40, 50, 60, 80, 90, 100 or any subrange composed of two values.

[0019] According to a preferred embodiment of the present invention, the R 3 Selected from

[0020] At least one of them.

[0021] According to a preferred embodiment of the present invention, the polyimide polymer is selected from at least one of the following structural formulas:

[0022]

[0023]

[0024] Where m and n are each independently selected from any integers from 10 to 100.

[0025] A method for producing polyimide polymers according to a second aspect of the present invention includes the following steps:

[0026] S1. Under an inert atmosphere, diamine monomer 1, diamine monomer 2, catalyst, aromatic dianhydride monomer and first strongly polar solvent are mixed and reacted in reaction I. The temperature is raised to 100-180℃ and reaction II is continued to obtain the first reaction solution.

[0027] S2. The first reaction solution is added dropwise to an alcohol solvent to produce a precipitate, thus obtaining an intermediate;

[0028] S3. Under an inert atmosphere, the intermediate, R3-OR3, triethylamine, and a second strongly polar solvent are mixed and reacted in reaction III to obtain a second reaction solution;

[0029] S4. The second reaction solution is added dropwise to an alcohol solvent to produce a precipitate, thereby obtaining the polyimide polymer;

[0030] The aromatic dianhydride monomer is selected from one of 4,4'-(hexafluoroisopropene) phthalic anhydride, 4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride or 4,4'-oxobisphthalic anhydride.

[0031] The structural formulas of diamine monomer 1, diamine monomer 2, and the intermediate are as follows:

[0032]

[0033] In the structural formulas of diamine monomer 1, diamine monomer 2, intermediate, and R3-O--R3, m, n, and R 1 R 2 R 3 The definitions of m, n, and R as described in the first aspect 1 R 2 R 3 The definitions correspond to the same.

[0034] According to a preferred embodiment of the present invention, in step S1, the catalyst is selected from at least one of isoquinoline, acetic anhydride, triethylamine or pyridine.

[0035] According to a preferred embodiment of the present invention, in step S1, the molar ratio of the catalyst to the diamine monomer 1 is 0.01 to 0.1:1.

[0036] According to a preferred embodiment of the present invention, the molar ratio of the diamine monomer 1, the diamine monomer 2 and the aromatic dianhydride monomer is (0.45-0.55):(0.45-0.55):1.

[0037] According to a preferred embodiment of the present invention, the molar ratio of the intermediate, R3-O-R3 and triethylamine is 1:(1-5):(1-5).

[0038] According to a preferred embodiment of the present invention, in steps S2 and S4, the alcohol solvent is independently selected from at least one of methanol, ethanol, propanol or isopropanol.

[0039] According to a preferred embodiment of the present invention, in step S1, the temperature of reaction I is 20–30°C. For example, it is 20°C, 25°C, or 30°C.

[0040] According to a preferred embodiment of the present invention, in step S1, the reaction time of reaction I is 10 to 25 hours. For example, it is 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 25 hours.

[0041] According to a preferred embodiment of the present invention, in step S1, the reaction time of reaction II is ≥3h.

[0042] According to a preferred embodiment of the present invention, in step S1, the reaction time of reaction II is ≤36h. For example, the reaction time is 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 28h, 30h, 36h, etc.

[0043] According to a preferred embodiment of the present invention, the temperature of reaction III is 20–30°C. For example, it is 20°C, 25°C, or 30°C.

[0044] According to a preferred embodiment of the present invention, the reaction time of reaction III is 10 to 32 hours. For example, it is 10 hours, 12 hours, 24 hours, 26 hours, 28 hours, 30 hours, or 32 hours.

[0045] According to a preferred embodiment of the present invention, the polarity of the first strongly polar solvent and the second strongly polar solvent is 4.0 or higher.

[0046] According to a preferred embodiment of the present invention, the first strongly polar solvent and the second strongly polar solvent are independently selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide and m-methylphenol.

[0047] According to a preferred embodiment of the present invention, in step S2, the amount of ethanol used is 10 to 15 times the volume of the first reaction liquid.

[0048] According to a preferred embodiment of the present invention, in step S4, the amount of ethanol used is 10 to 15 times the volume of the second reaction liquid.

[0049] According to a preferred embodiment of the present invention, the method further includes: filtering the precipitate obtained in step S2 and then performing a first drying treatment to obtain the intermediate.

[0050] According to a preferred embodiment of the present invention, the method further includes: filtering the precipitate obtained in step S4 and then performing a second drying treatment to obtain the polyimide polymer.

[0051] According to a preferred embodiment of the present invention, in step S2 or S4, the conditions for the first drying treatment and the second drying treatment are each independently vacuum drying at 80-100°C for 8-12 hours.

[0052] A third aspect of the present invention provides a polyimide film comprising the polyimide polymer described in the first aspect of the present invention.

[0053] Therefore, the polyimide film of the present invention has high light transmittance, low dielectric constant, and excellent thermal and mechanical properties.

[0054] A fourth aspect of the present invention provides a method for preparing a polyimide film, comprising the following steps:

[0055] The polyimide polymer described in the first aspect and the third organic solvent are mixed and stirred to obtain solution A; solution A is coated on a substrate, vacuumed, heated and kept warm; after the treatment is completed, it is cooled, the substrate is peeled off and dried to obtain the final product.

[0056] The method for preparing polyimide films according to embodiments of the present invention has at least the following beneficial effects:

[0057] The raw materials used in the preparation method of this invention are readily available, and the preparation process is simple and controllable, which is conducive to industrial production. The polyimide film containing alkyl fluorene Cardo and benzimidazole structures obtained by this method has high thermal stability and excellent mechanical properties, and its dielectric properties, light transmittance, and solubility are all improved. The polyimide film prepared by this invention is suitable for applications in integrated circuits, electronics, microelectronics, and liquid crystal displays.

[0058] According to a preferred embodiment of the present invention, the solid content of solution A is 8-18 wt%.

[0059] According to a preferred embodiment of the present invention, the heating and heat preservation steps are as follows:

[0060] Maintain at 50±2℃ for 8–12 hours, at 100±2℃ for 2–4 hours, at 150±2℃ for 2–4 hours, and at 200±2℃ for 2–4 hours.

[0061] According to a preferred embodiment of the present invention, the substrate is a silicon dioxide glass plate.

[0062] According to a preferred embodiment of the present invention, the third organic solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylacetamide.

[0063] The fifth aspect of the present invention provides a polyimide polymer as described above; or the application of the polyimide film as described above in integrated circuits, electronics, microelectronics and flexible display materials.

[0064] In this invention Indicates the linking site of a functional group.

[0065] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0066] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0067] Figure 1 The infrared spectra of the polyimide films prepared in Examples 6-10 and Comparative Example 1 of this invention are shown below.

[0068] Figure 2 The above are the proton NMR spectra of the polyimide films obtained in Comparative Example 1 and Example 8 of the present invention.

[0069] Figure 3 The UV-Vis spectra of the polyimide films prepared in Examples 6-10 and Comparative Example 1 of this invention are shown below.

[0070] Figure 4 The dielectric constant and loss-frequency curves of the polyimide films prepared in Examples 6-10 and Comparative Example 1 of this invention are shown. Detailed Implementation

[0071] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0072] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0073] Some of the raw materials used in this invention are as follows:

[0074] Synthesis of diamine monomer 1: The structural formula and preparation method are as follows:

[0075]

[0076] (1) Weigh 0.05 mol of 2,7-dihydroxy-9-fluorenone and add it to a 500 mL single-necked flask. Add 0.4 mol of 2,6-dimethylaniline, and then add 0.025 mol of methanesulfonic acid (CH3SO3H) as a catalyst. Under nitrogen protection, the temperature is raised to 150 °C and the reaction is carried out for 15 hours. After the reaction is completed, the reaction solution is cooled to 110 °C, 200 mL of triethylamine is added, and the mixture is refluxed at 110 °C for 20 minutes.

[0077] (2) After the reaction was stopped, the mixture was cooled to room temperature, and an appropriate amount of ethanol was added to precipitate a black viscous solid. After standing, the mixture was filtered to obtain a crude product. The black viscous solid was washed with ethanol several times until a light yellow powder solid was obtained. The solid sample was filtered and dried in a vacuum drying oven at 110°C for 12 hours to finally obtain 15.61g of pure diamine monomer 1.

[0078] Example 1

[0079] This example provides a polyimide polymer I-1, the structural formula of which and its preparation method are as follows:

[0080]

[0081] S1. Place 1.7769 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 0.8731 g of diamine monomer 1, and 0.4485 g of diamine monomer 2 in a two-necked flask; pour 14.06 mL of N-methylpyrrolidone (NMP) solvent into the two-necked flask, and finally add 0.13 g of isoquinoline. Mix thoroughly with magnetic stirring, and react at room temperature for 12 hours under nitrogen protection, then raise the temperature to 120°C and react for 1 hour, and continue to raise the temperature to 180°C and react for 3 hours to obtain the first reaction solution;

[0082] S2. The first reaction solution was added dropwise to 400 mL of ethanol, producing a fibrous precipitate, which was then allowed to stand and filtered. The precipitate was dried under vacuum at 80 °C for 10 hours to obtain the intermediate.

[0083] S3. Dissolve 1.4773g of the above intermediate in 30mL of N,N-dimethylformamide (DMF), add 0.51g of acetic anhydride and 0.505g of triethylamine, and react under nitrogen protection for 24 hours to obtain the second reaction solution.

[0084] S4. The second reaction liquid is added dropwise to 400 mL of ethanol, producing a fibrous precipitate, which is then allowed to stand and filtered. The precipitate is then vacuum dried at 80 °C for 10 hours to obtain the polyimide polymer.

[0085] The number-average molecular weight, determined by GPC, was 2.62 × 10⁻⁶. 4g·mol -1 PDI = 1.70, and the average number of repeating units, m and n, are both 17.

[0086] Example 2

[0087] This example provides a polyimide polymer I-2, the structural formula of which and its preparation method are as follows:

[0088]

[0089] The preparation method is basically the same as in Example 1, except that the 0.51g acetic anhydride in step S3 is replaced with 0.791g butyric anhydride.

[0090] The number-average molecular weight, determined by GPC, was 3.10 × 10⁻⁶. 4 g·mol -1 PDI = 1.92, and the average number of repeating units, m and n, are both 19.

[0091] Example 3

[0092] This example provides a polyimide polymer I-3, the structural formula of which and its preparation method are as follows:

[0093]

[0094] The preparation method is basically the same as in Example 1, except that the 0.51g acetic anhydride in step S3 is replaced with 1.072g hexanoic anhydride.

[0095] The number-average molecular weight, determined by GPC, was 2.95 × 10⁻⁶. 4 g·mol -1 PDI = 1.94, and the average number of repeating units, m and n, are both 18.

[0096] Example 4

[0097] This example provides a polyimide polymer I-4, whose structural formula and preparation method are as follows:

[0098]

[0099] The preparation method is basically the same as in Example 1, except that the 0.51g acetic anhydride in step S3 is replaced with 1.352g octanoic anhydride.

[0100] The number-average molecular weight, determined by GPC, was 3.90 × 10⁻⁶. 4 g·mol -1 PDI = 1.97, and the average number of repeating units m and n are both 23.

[0101] Example 5

[0102] This example provides a polyimide polymer I-5, the structural formula of which and its preparation method are as follows:

[0103]

[0104] The preparation method is basically the same as in Example 1, except that 0.51g of acetic anhydride in step S3 is replaced with 1.633g of decanoic anhydride.

[0105] The number-average molecular weight, determined by GPC, was 3.46 × 10⁻⁶. 4 g·mol -1 PDI = 1.99, and the average number of repeating units, m and n, are both 19.

[0106] Example 6

[0107] This example provides a polyimide film, the preparation method of which is as follows:

[0108] The polyimide polymer I-1 prepared in Example 1 of this invention was dissolved in DMF, and the solid content of the solution was controlled to be 10%. After thorough stirring and dissolution, it was uniformly coated on a clean silica glass plate, vacuumed and left to stand for 2 hours, then heated to 50°C and dried for 8 hours. Then it was kept at 100°C, 150°C and 200°C for 3 hours each, and after cooling, a highly transparent and low dielectric polyimide film (named: 6FDA-OAc-NH) was obtained.

[0109] Example 7

[0110] This example provides a polyimide film (named: 6FDA-OBu-NH), which is prepared by the same method as in Example 6, except that the polyimide polymer I-2 prepared in Example 2 is used instead of polyimide polymer I-1.

[0111] Example 8

[0112] This example provides a polyimide film (named: 6FDA-OHe-NH), which is prepared by the same method as in Example 6, except that the polyimide polymer I-3 prepared in Example 2 is used instead of polyimide polymer I-1.

[0113] Example 9

[0114] This example provides a polyimide film (named: 6FDA-OOc-NH), which is prepared using the same method as in Example 6, except that the polyimide polymer I-4 prepared in Example 2 is used instead of polyimide polymer I-1.

[0115] Example 10

[0116] This example provides a polyimide film (named: 6FDA-ODe-NH), which is prepared by the same method as in Example 6, except that the polyimide polymer I-5 prepared in Example 2 is used instead of polyimide polymer I-1.

[0117] Comparative Example 1

[0118] Comparative Example 1 provides a polyimide film with the following structural formula and preparation method:

[0119]

[0120] S1. Place 1.7769 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 0.8731 g of diamine monomer 1, and 0.4485 g of diamine monomer 2 in a two-necked flask; pour 14.06 mL of N-methylpyrrolidone (NMP) solvent into the two-necked flask, and finally add 0.13 g of isoquinoline. Mix thoroughly with magnetic stirring, and react at room temperature for 12 hours under nitrogen protection, then raise the temperature to 120°C and react for 1 hour, and continue to raise the temperature to 180°C and react for 3 hours to obtain the first reaction solution;

[0121] S2. The first reaction solution was added dropwise to 400 mL of ethanol, producing a fibrous precipitate, which was then allowed to stand and filtered. The precipitate was then vacuum dried at 80 °C for 10 hours to obtain polyimide resin.

[0122] S3. Dissolve a portion of the above-mentioned polyimide resin in DMF, controlling the solid content to 10%. After thorough stirring and dissolution, coat the solution evenly onto a clean silica glass plate, vacuum and let it stand for 2 hours, then heat it to 50°C and dry it for 8 hours. Then, heat it at 100°C, 150°C, and 200°C for 3 hours each, and cool it to obtain a polyimide film (named: 6FDA-OH-NH).

[0123] The number-average molecular weight, determined by GPC, was 2.55 × 10⁻⁶. 4 g·mol -1 PDI = 1.73, and the average number of repeating units m and n are both 17.

[0124] Performance testing

[0125] Infrared spectroscopy testing: The polyimide films prepared in Examples 6-10 and Comparative Example 1 of this invention were subjected to infrared spectroscopy testing, and the results are as follows: Figure 1 As shown:

[0126] Its structure was confirmed by infrared spectroscopy. The infrared (IR) spectrum of the prepared thin film product (Comparative Example 1) is shown in Figure 1, with the spectrum ranging from 3105 to 3629 cm⁻¹. -1The broad absorption band is characterized by the broad absorption peaks of -OH and -NH-, 2957-2861 cm⁻¹. -1 The absorption peak for the CH stretching vibration of methyl groups is 1776-1785 cm⁻¹. -1 and 1708-1726cm -1 The absorption peaks correspond to the asymmetric and symmetric stretching vibrations of C=O in the imide ring, respectively, at 1608 cm⁻¹. -1 1596cm -1 and 1484cm -1 Corresponding to the vibration of the aromatic ring skeleton, 1366-1369 cm -1 This corresponds to the CN stretching vibration.

[0127] The IR spectra of Examples 6-10 are shown in Figure 1. Compared with the IR spectrum of Comparative Example 1, the range of 3105-3629 cm⁻¹ is significantly larger. -1 The characteristic absorption broad peak intensity weakens, 2957-2861 cm⁻¹ -1 The characteristic peak of the CH stretching vibration at 1763 cm⁻¹ is enhanced, and the absorption peak of the C=O symmetric stretching vibration in the imide ring undergoes a blue shift, and is located at 1763 cm⁻¹. -1 New characteristic peaks of C=O stretching vibration appeared on both sides.

[0128] Furthermore, the polyimide films obtained in Example 8 and Comparative Example 1 of this invention were dissolved in deuterated DMSO and subjected to proton nuclear magnetic resonance spectroscopy (NMR) analysis. The results are as follows: Figure 2 As shown:

[0129] The proton NMR spectrum (600MHz, CD3Cl) of the thin film product is shown in the attached image. Figure 2 As shown, for Comparative Example 1, 9.48 ppm and 13.28 ppm correspond to the proton signal singlets of -OH and -NH-, respectively; 2.03 ppm corresponds to the methyl proton signal singlet; and 6.77-8.35 ppm corresponds to the aromatic proton signal peaks. Compared to the 1H NMR spectrum of Comparative Example 1, the -OH proton signal singlet at 9.48 ppm in Example 8 disappears, and three new signal peaks appear in the aliphatic region: 2.56 ppm (H2), 1.66 ppm (H3), and 0.95 ppm (H4), corresponding to the butyryloxy groups -OCO-CH2-, -CH2-, and -CH3 in Example 8, respectively.

[0130] The polyimide films obtained in Examples 6-10 and Comparative Example 1 were subjected to the performance tests shown below, and the results are shown in Tables 1 and 2.

[0131] Glass transition temperature (T) g The results were obtained by differential scanning calorimetry (DSC) under nitrogen protection at a heating rate of 10 °C / min. The results are shown in Table 1.

[0132] Tensile strength (T) s The tensile properties of polyimide films were tested using an electronic universal testing machine at room temperature with a tensile rate of 5 mm / min and a tensile load of 1000 N. Each sample was tested in parallel for 5 times and the average value was taken. The results are shown in Table 1.

[0133] Light transmittance (T) 450 The transmittance of the thin film (thickness 25±2 μm) at 450 nm was measured using a UV-Vis spectrophotometer. The results are as follows: Figure 3 As shown in Table 1.

[0134] Dielectric constant (D) k ), dielectric loss (D) f The dielectric constant and dielectric loss of polyimide films at 1 MHz were measured using a capacitance test method. The results are as follows: Figure 4 As shown in Table 1.

[0135] Solubility: 10 mg of the film sample was dissolved in 1 mL of solvent. After being sealed at room temperature for 24 h, the solubility of the film was observed. For films that could not be dissolved, the solvent was heated to its boiling point to observe whether the film would dissolve: ++, soluble at room temperature; +, soluble upon heating; ±, partially dissolved or expanded upon heating; --, insoluble even upon heating. The results are shown in Table 2.

[0136] Table 1: Performance test results of polyimide films obtained in Examples 6-10 and Comparative Example 1

[0137]

[0138] Table 2: Results of solubility tests on polyimide films obtained in Examples 6-10 and Comparative Example 1

[0139]

[0140]

[0141] As can be seen from the above test results, the polyimide film prepared by the method provided by the present invention has a low dielectric constant and a high light transmittance, while also maintaining the excellent thermal, mechanical and solubility properties of polyimide film, making it suitable for integrated circuits, electronics, microelectronics and liquid crystal displays and other fields.

[0142] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A polyimide polymer, characterized in that, It has the structure shown in Equation I: ； Where m and n are each independently selected from any integers from 10 to 100; R 1 Selected from H, C 1~3 Alkyl groups; R 2 Selected from , , ; R 3 Selected from , where X is any integer from 0 to 15.

2. The polyimide polymer according to claim 1, characterized in that, R 3 Selected from , , , , , , , , At least one of them.

3. The polyimide polymer according to claim 1 or 2, characterized in that, The polyimide polymer is selected from at least one of the following structural formulas: , 、 、 、 ； Where m and n are each independently selected from any integer between 10 and 100.

4. A method for preparing the polyimide polymer according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Under an inert atmosphere, diamine monomer 1, diamine monomer 2, catalyst, aromatic dianhydride monomer and first strongly polar solvent are mixed and reacted in reaction I. The temperature is raised to 100~180 ℃ and reaction II is continued to obtain the first reaction solution. S2. The first reaction solution is added dropwise to an alcohol solvent to produce a precipitate, thus obtaining an intermediate; S3. Under an inert atmosphere, the intermediate, The mixture of triethylamine and a second strongly polar solvent is reacted to produce reaction III, yielding the second reaction solution; S4. The second reaction solution is added dropwise to an alcohol solvent to produce a precipitate, thereby obtaining the polyimide polymer; The aromatic dianhydride monomer is selected from one of 4,4'-(hexafluoroisopropene) phthalic anhydride, 4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride or 4,4'-oxobisphthalic anhydride. The structural formulas of diamine monomer 1, diamine monomer 2, and the intermediate are as follows: ； ； ； In the diamine monomer 1, diamine monomer 2 and intermediate, In the structural formula, m, n, R 1 R 2 R 3 The definitions of m, n, and R as described in any one of claims 1-3 1 R 2 R 3 The definitions correspond to the same.

5. The preparation method according to claim 4, characterized in that, In step S1, the catalyst is selected from at least one of isoquinoline, acetic anhydride, triethylamine, or pyridine.

6. The preparation method according to claim 4, characterized in that, In step S1, the molar ratio of the catalyst to the diamine monomer 1 is 0.01 to 0.1:

1.

7. The preparation method according to claim 4, characterized in that, In step S1, the molar ratio of diamine monomer 1, diamine monomer 2 and aromatic dianhydride monomer is (0.45-0.55):(0.45-0.55):

1.

8. The preparation method according to claim 4, characterized in that, In step S3, the intermediate, The molar ratio of triethylamine to triethylamine is 1:(1~5):(1~5).

9. The preparation method according to claim 4, characterized in that, The polarity of the first and second strongly polar solvents is above 4.

0.

10. The preparation method according to claim 4, characterized in that, The first and second strongly polar solvents are independently selected from... N,N -Dimethylformamide, N methylpyrrolidone, dimethyl sulfoxide, N,N At least one of dimethylacetamide and m-methylphenol.

11. A polyimide film, characterized in that, The polyimide film comprises the polyimide polymer as described in any one of claims 1 to 3.

12. A method for preparing the polyimide film as described in claim 11, characterized in that, Includes the following steps: The polyimide polymer according to any one of claims 1 to 3 is mixed and stirred with a third organic solvent to obtain solution A; solution A is coated on a substrate, and vacuum is applied, followed by heating and heat preservation treatment; After processing, the substrate is cooled, peeled off, and dried to obtain the final product.

13. The use of the polyimide polymer according to any one of claims 1 to 3 or the polyimide film according to claim 11 in integrated circuits, electronics, microelectronics and flexible display materials.

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