A polyimide polymer and its preparation method and application

Abstract

The present invention discloses a polyimide polymer and a preparation method and application thereof. The polyimide polymer has a structure shown in formula (I): #imgabs0# wherein n is in the range of 50 to 500; R1 is selected from H, C 1～3 Alkyl; R 2 Selected from #imgabs1#‑OR 3 The group is monosubstituted or polysubstituted, and the R 3 At least one selected from #imgabs2#. A bulky siloxane side group is introduced into the structural formula of the polyimide polymer of the present invention. Due to the presence of a triphenylmethane structure in the PI main chain, it has excellent heat resistance and mechanical properties. On the other hand, thanks to the introduction of the siloxane side group, the packing density of the molecular chain and the formation of charge transfer complexes (CTCs) can be significantly reduced, so that the dielectric properties, transmittance and solubility of the PI film prepared therefrom are improved.

Description

Technical Field

[0001] The invention relates to the technical field of thin films, and in particular to a polyimide polymer and a preparation method and application thereof. Background Art

[0002] Polyimide (PI) films have excellent physical and chemical properties and are widely used in high-tech fields such as electrical, electronic, aerospace, and optics. With the rapid development of the microelectronics and optoelectronics industries, there is an urgent need for films with high glass transition temperatures (T g ), low dielectric constant (D k ) and loss factor (D f ), solution-processable PI films with high transmittance to meet high-temperature processing and device use conditions. However, due to its electronic conjugated structure and the formation of intramolecular and intermolecular charge transfer complexes (CTCs) between the electron donor diamine and electron acceptor dianhydride fragments, traditional aromatic PI films usually exhibit dark coloration, relatively high dielectric constant (D k >3.0) and poor solubility in organic solvents.

[0003] In order to overcome the above-mentioned shortcomings of PI films, people have devoted themselves to modifying PI at the molecular level. The above-mentioned methods mainly focus on designing and synthesizing diamine monomers containing large side groups, which have defects such as many synthesis steps, complex purification process, and low polymerization reaction activity of most synthetic monomers.

[0004] Therefore, it is necessary to develop a new polyimide polymer that has both high T g , low D k , low D f And high transparency. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first aspect of the present invention provides a polyimide polymer having a low dielectric constant, a high glass transition temperature and transparency.

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

[0007] The third aspect of the present invention also provides a polyamideimide film.

[0008] The fourth aspect of the present invention also provides an application.

[0009] According to the first aspect of the present invention, the polyimide polymer provided by the embodiment has a structure shown in formula (I):

[0010]

[0011] Where n ranges from 50 to 500;

[0012] R1 is selected from H, C 1～3 The alkyl group;

[0013] R 2 Selected from

[0014] -OR 3 The group is monosubstituted or polysubstituted, and the R 3 Selected from At least one of .

[0015] The polyimide polymer according to the embodiment of the present invention has at least the following beneficial effects:

[0016] The structural formula of the polyimide polymer of the present invention introduces bulky siloxane side groups. Due to the presence of triphenylmethane structure in the PI main chain, it has excellent heat resistance and mechanical properties. On the other hand, thanks to the introduction of siloxane side groups, the packing density of the molecular chain and the formation of charge transfer complexes (CTCs) can be significantly reduced, so that the dielectric constant, transmittance and solubility of the PI film prepared by it are improved.

[0017] According to some embodiments of the present invention, the range of n is 60-300; according to some embodiments of the present invention, the range of n is 60-201.

[0018] According to some embodiments of the present invention, R1 is selected from H and methyl.

[0019] According to some embodiments of the present invention, the polyimide polymer is selected from one of the following structural formulas:

[0020]

[0021]

[0022] According to a second aspect of the present invention, a method for preparing a polyimide polymer is provided, comprising the following steps:

[0023] S1, under an inert atmosphere, mixing compound 1, aromatic dianhydride monomer, catalyst and a first strong polar solvent, heating and reacting to obtain a first reaction solution;

[0024] S2, mixing the first reaction liquid and ethanol in a mass ratio of 1:(15-20), removing the ethanol, and drying to obtain an intermediate 1;

[0025] S3, under inert atmosphere, intermediate 1, containing R3 Mixing the halogenated silane of the group, imidazole and a second strong polar solvent, heating and reacting, and obtaining a second reaction solution;

[0026] S4, mixing the second reaction liquid and ethanol in a mass ratio of 1:(15-20), removing the ethanol, and drying to obtain a polyimide polymer;

[0027] The aromatic dianhydride monomer is selected from one of 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 4,4'-oxydiphthalic anhydride or 3,3',4,4'-benzophenonetetracarboxylic dianhydride;

[0028] The structural formulas of the compound 1 and intermediate 1 are as follows:

[0029]

[0030] According to some embodiments of the present invention, the catalyst is selected from at least one of isoquinoline, acetic anhydride, triethylamine or pyridine.

[0031] According to some embodiments of the present invention, in step S1, the amount of the catalyst used is 0.01 to 0.1 times the molar number of the aromatic diamine monomer.

[0032] According to some embodiments of the present invention, in step S1, the molar ratio of the compound 1 to the aromatic diamine monomer is 1:(0.9-1.1).

[0033] According to some embodiments of the present invention, in step S1, the amount of the first strongly polar organic solvent used is 4 to 9 times the total mass of compound 1 and the aromatic dianhydride monomer.

[0034] According to some embodiments of the present invention, in step S3, the intermediate 1, containing R 3 The molar ratio of the halogenated silane and the imidazole of the group is 1:(1-4):(1-4).

[0035] According to some embodiments of the present invention, the 3 The halogen in the halosilane group includes fluorine, chlorine, bromine or iodine.

[0036] According to some embodiments of the present invention, in step S1, the heating is performed twice; the temperature of the first heating is 25-85°C; the temperature of the second heating is 150-220°C.

[0037] According to some embodiments of the present invention, in step S1, the first heating time is 2 to 12 hours.

[0038] According to some embodiments of the present invention, in step S2, the first heating time is 2 to 24 hours.

[0039] According to some embodiments of the present invention, in step S2, the heating temperature is 10-50°C.

[0040] According to some embodiments of the present invention, in step S2, the heating time is 12 to 60 hours.

[0041] According to some embodiments of the present invention, the first strong polar solvent and the second strong polar solvent are solvents with polarity ≥ 4.0.

[0042] According to some embodiments of the present invention, the first strong polar solvent and the second strong polar solvent are independently selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide and m-cresol.

[0043] According to some embodiments of the present invention, the first drying is vacuum drying at 80-110° C. for 6-12 hours.

[0044] According to some embodiments of the present invention, the second drying is vacuum drying at 80-110° C. for 6-12 hours.

[0045] A third aspect of the present invention provides a polyimide film, wherein the polyimide film comprises the polyimide polymer described above.

[0046] The polyimide film according to the embodiment of the present invention has at least the following beneficial effects:

[0047] The polyimide film containing triphenylmethane structure with silane side groups prepared by the present invention has high thermal stability and excellent mechanical properties, and its dielectric constant, light transmittance and solvent properties are all improved. The polyimide film of the present invention is suitable for application in high-tech industries such as electronics, microelectronics, and flexible displays.

[0048] According to some embodiments of the present invention, the polyimide film is prepared by the following method:

[0049] The polyimide polymer prepared above is mixed with a third strong polar solvent to obtain a slurry, which is then coated on a substrate, and then dried and cooled to obtain a polyimide film.

[0050] According to some embodiments of the present invention, the solid content of the slurry is 10-15%.

[0051] According to some embodiments of the present invention, the substrate includes a silica glass plate or a polytetrafluoroethylene plate.

[0052] The third drying is drying at 50-90° C. for 2-8 hours, then heating to 100-150° C. for drying for 2-4 hours, and further heating to 180-200° C. for drying for 2-4 hours.

[0053] According to some embodiments of the present invention, the third strongly polar solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide and m-cresol.

[0054] The fourth aspect of the present invention provides the use of the polyimide polymer or the polyimide film described above in a dielectric layer of electronics or microelectronics or a flexible display substrate.

[0055] In the present invention Indicates the attachment site of a group.

[0056] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0058] Figure 1 The infrared spectra of the polyimide films prepared in Example 1, Example 2, Example 3 and Comparative Example 1;

[0059] Figure 2 is the hydrogen nuclear magnetic resonance spectrum of the polyimide polymer obtained in Example 1;

[0060] Figure 3 is the hydrogen nuclear magnetic resonance spectrum of the polyimide polymer obtained in Example 2;

[0061] Figure 4 is the hydrogen nuclear magnetic resonance spectrum of the polyimide polymer obtained in Example 3;

[0062] Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of the polyimide polymer obtained in Comparative Example 1. DETAILED DESCRIPTION

[0063] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0064] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0065] Example 1

[0066] Embodiment 1 provides a polyimide polymer, and its structural formula is as follows:

[0067]

[0068] The preparation method is as follows:

[0069] S1. Under nitrogen atmosphere, add 1.7769 g of 4,4'-(hexafluoroisopropylene) diphthalic anhydride and 1.3859 g of 5,5'-tetramethyl-4,4'-diamino-4"-hydroxytriphenylmethane (TPMOH) and 20 mL of N-methylpyrrolidone (NMP) and 0.13 g of isoquinoline into a 100 mL three-necked reaction bottle. Stir and react at room temperature for 12 hours. Then heat to 120°C for 1 hour, and then heat to 180°C for 3 hours to obtain a polyimide solution.

[0070] S2, the hydroxy triphenylmethane structure-containing polyimide solution was added dropwise to 400 mL of ethanol, a fibrous precipitate was precipitated, and the precipitate was vacuum dried at 90° C. for 10 hours to obtain a hydroxy triphenylmethane structure-containing polyimide resin;

[0071] S3, taking 1.7355g of the above-obtained hydroxyl triphenylmethane structure polyimide resin, dissolving it in 19g of N,N-dimethylformamide (DMF), adding 0.8665g of tert-butyldimethylsilyl chloride and 0.3914g of imidazole, reacting for 24 hours under nitrogen protection, and obtaining a silane side group triphenylmethane structure polyimide solution;

[0072] S4. The polyimide solution containing triphenylmethane structure with silane side groups is added dropwise into 400 g of ethanol, and a fibrous precipitate is precipitated. The precipitate is vacuum dried at 90° C. for 10 hours to obtain a polyimide polymer.

[0073] The number average molecular weight was measured by GPC method and was 10.3×10 4 g·mol -1 , PDI=1.91, and the average number of repeating units is 118.

[0074] The polyimide polymer prepared in Example 1 is prepared into a polyimide film, and the steps are as follows:

[0075] Take part of the dried polyimide polymer and dissolve it in DMF, control the solid content to 15%, stir thoroughly to dissolve, evenly apply it on a clean silica glass plate, evacuate and let it stand for 2 hours, then heat it to 50°C and dry it for 5 hours, then heat it to 100°C and dry it for 8 hours, continue to heat it to 200°C and dry it for 3 hours, and then cool it to obtain the polyimide film 6FDA-TPMOSi.

[0076] Its structure was confirmed by infrared spectroscopy and nuclear magnetic resonance hydrogen spectrum. The infrared (IR) spectrum of the prepared film product is shown in Figure 1a. The 2955-2856 cm -1 The CH stretching vibration peak of the methyl group is 1785 cm-1 and 1725cm -1 The characteristic peaks at 1607 cm-1 correspond to the asymmetric and symmetric stretching vibrations of C=O in the imide ring. -1 、1509cm -1 and 1485cm -1 Corresponding to the vibration of the aromatic ring skeleton, 1366 cm -1 Corresponding to CN stretching vibration; the H NMR spectrum (600 MHz, CD3Cl) of the film product is shown in the attached Figure 2 As shown, the chemical shifts were assigned as δ = 8.04 (d, J = 8.0 Hz, 2H), 7.97 (s, 2H), 7.89 (d, J = 7.3 Hz, 2H), 7.03 (d, J = 8.4 Hz, 2H), 6.95 (d, J = 6.0 Hz, 4H), 6.81 (d, J = 8.4 Hz, 2H), 5.41 (s, 1H), 2.13 (s, 12H), 0.98 (s, 9H), 0.21 (s, 6H).

[0077] Example 2

[0078] Embodiment 2 provides a polyimide polymer, and its structural formula is as follows:

[0079]

[0080] The preparation method is basically the same as that of Example 1, except that 1.7769 g of 4,4'-(hexafluoroisopropylene) diphthalic anhydride in step S1 of Example 1 is replaced with 1.2409 g of 4,4'-oxydiphthalic anhydride (ODPA).

[0081] The number average molecular weight was measured by GPC method and was 4.74×10 4 g·mol -1 , PDI=2.32, and the average number of repeating units is 65.

[0082] The polyimide polymer prepared in Example 2 is prepared into a polyimide film ODPA-TPMOSi, and the preparation method thereof is the same as that in Example 1.

[0083] Its structure was confirmed by infrared spectroscopy and nuclear magnetic resonance hydrogen spectrum. The infrared (IR) spectrum of the prepared film product is shown in Figure 1b. -1 The CH stretching vibration peak of the methyl group is 1776 cm -1 and 1719cm -1 The characteristic peaks at 1606 cm-1 correspond to the asymmetric and symmetric stretching vibrations of C=O in the imide ring, respectively. -1 、1507cm -1 and 1472cm-1 Corresponding to the vibration of the aromatic ring skeleton, 1365cm -1 Corresponding to CN stretching vibration; the H NMR spectrum (600 MHz, CD3Cl) of the film product is shown in the attached Figure 3 As shown, the chemical shifts were assigned as δ = 8.01 (d, J = 8.1 Hz, 2H), 7.56 (s, 2H), 7.50 (d, J = 8.1 Hz, 2H), 7.03 (d, J = 8.4 Hz, 2H), 6.93 (s, 4H), 6.80 (d, J = 8.4 Hz, 2H), 5.40 (s, 1H), 2.12 (s, 12H), 0.98 (s, 9H), 0.21 (s, 6H).

[0084] Example 3

[0085] Embodiment 3 provides a polyimide polymer, and its structural formula is as follows:

[0086]

[0087] The preparation method is basically the same as that of Example 1, except that 1.7769 g of 4,4'-(hexafluoroisopropylene) diphthalic anhydride in step S1 of Example 1 is replaced with 1.1769 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride.

[0088] The number average molecular weight was measured by GPC method and was 7.80×10 4 g·mol -1 , PDI=2.92, and the average number of repeating units is 104.

[0089] The polyimide polymer prepared in Example 3 is prepared into a polyimide film BTDA-TPMOSi, and the preparation method thereof is the same as that in Example 1.

[0090] Its structure was confirmed by infrared spectroscopy and nuclear magnetic resonance hydrogen spectrum. The infrared (IR) spectrum of the prepared film product is shown in Figure lc. -1 The CH stretching vibration peak of the methyl group is 1775 cm -1 and 1713cm -1 The characteristic peaks at 1607 cm-1 correspond to the asymmetric and symmetric stretching vibrations of C=O in the imide ring. -1 、1506cm -1 and 1486cm -1 Corresponding to the vibration of the aromatic ring skeleton, 1364 cm -1 Corresponding to CN stretching vibration; the H NMR spectrum (600 MHz, CD3Cl) of the film product is shown in the attached Figure 4As shown, the chemical shifts were assigned as δ = 8.26 (s, 2H), 8.11 (q, J = 8.2 Hz, 4H), 7.05 (d, J = 8.5 Hz, 2H), 6.97 (s, 4H), 6.82 (d, J = 8.4 Hz, 2H), 5.43 (s, 1H), 2.14 (s, 12H), 0.99 (s, 9H), 0.22 (s, 6H).

[0091] Example 4

[0092] Embodiment 4 provides a polyimide polymer, and its structural formula is as follows:

[0093]

[0094] The preparation method is as follows:

[0095] S1. Under nitrogen atmosphere, add 1.7769g 4,4'-(hexafluoroisopropylene) diphthalic anhydride and 1.450g 5,5'-tetramethyl-4,4'-diamino-3",5"-dihydroxytriphenylmethane (TPM2OH) and 25g N-methylpyrrolidone (NMP) and 0.2g isoquinoline into a 100mL three-necked reaction bottle. Stir and react for 12 hours at room temperature. Then heat to 120°C for 3 hours, and then heat to 190°C for 5 hours to obtain a polyimide solution containing dihydroxytriphenylmethane structure;

[0096] S2, the hydroxy triphenylmethane structure-containing polyimide solution was added dropwise to 500 mL of ethanol, a fibrous precipitate was precipitated, and the precipitate was vacuum dried at 90° C. for 10 hours to obtain a hydroxy triphenylmethane structure-containing polyimide resin;

[0097] S3, taking 1.5414g of the above-obtained polyimide resin containing dihydroxytriphenylmethane structure, dissolving it in 30g of N,N-dimethylformamide (DMF), adding 1.3260g of tert-butyldimethylchlorosilane and 0.5446g of imidazole, reacting for 48 hours under nitrogen protection, and obtaining a polyimide solution containing disilane side triphenylmethane structure;

[0098] S4. The polyimide solution containing disilane side triphenylmethane structure is added dropwise into 500 g of ethanol, and a fibrous precipitate is precipitated. The precipitate is vacuum dried at 100° C. for 12 hours to obtain a polyimide polymer.

[0099] The number average molecular weight was measured by GPC method and was 11.5×10 4 g·mol -1 , PDI=1.82, and the average number of repeating units is 115.

[0100] The polyimide polymer prepared in Example 4 is prepared into a polyimide film, and the steps are as follows:

[0101] Take part of the dried polyimide polymer and dissolve it in DMF, control the solid content to 15%, stir thoroughly to dissolve, evenly apply it on a clean silica glass plate, evacuate and let it stand for 2 hours, then heat it to 50°C and dry it for 5 hours, then heat it to 100°C and dry it for 8 hours, continue to heat it to 200°C and dry it for 3 hours, and after cooling, obtain the polyimide film 6FDA-TPM2OSi.

[0102] Example 5

[0103] Embodiment 5 provides a polyimide polymer, and its structural formula is as follows:

[0104]

[0105] The preparation method is basically the same as that of Example 4, except that 1.7769 g of 4,4'-(hexafluoroisopropylene) diphthalic anhydride in Example 4 is replaced with 1.2409 g of 4,4'-oxydiphthalic anhydride (ODPA).

[0106] The number average molecular weight was measured by GPC method and was 6.23×10 4 g·mol -1 , PDI = 2.35, the average number of repeating units is 72;

[0107] The polyimide polymer prepared in Example 5 is prepared into a polyimide film ODPA-TPM2OSi, and its preparation method is the same as that in Example 4.

[0108] Example 6

[0109] Embodiment 6 provides a polyimide polymer, and its structural formula is as follows:

[0110]

[0111] The preparation method is basically the same as that of Example 4, except that 1.7769 g of 4,4'-(hexafluoroisopropylene) diphthalic anhydride in Example 4 is replaced by 1.1769 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride.

[0112] The number average molecular weight was measured by GPC method and was 8.31×10 4 g·mol -1 , PDI = 2.12, the average number of repeating units is 95;

[0113] The polyimide polymer prepared in Example 6 is prepared into a polyimide film BTDA-TPM2OSi, and its preparation method is the same as that in Example 4.

[0114] Comparative Example 1

[0115] Comparative Example 1 provides a polyimide polymer, the structural formula of which is as follows:

[0116]

[0117] The preparation method is as follows:

[0118] S1. Under nitrogen atmosphere, add 1.7769 g of 4,4'-(hexafluoroisopropylene) diphthalic anhydride and 1.3859 g of 5,5'-tetramethyl-4,4'-diamino-4"-hydroxytriphenylmethane (TPMOH) and 20 mL of N-methylpyrrolidone (NMP) and 0.13 g of isoquinoline into a 100 mL three-necked reaction bottle. Stir and react at room temperature for 12 hours. Then heat to 120°C for 1 hour, and then heat to 180°C for 3 hours to obtain a polyimide solution.

[0119] S2, the hydroxy triphenylmethane structure-containing polyimide solution was added dropwise to 400 mL of ethanol, a fibrous precipitate was precipitated, and the precipitate was vacuum dried at 90° C. for 10 hours to obtain a hydroxy triphenylmethane structure-containing polyimide resin;

[0120] The number average molecular weight was measured by GPC method and was 9.93×10 4 g·mol -1 , PDI=2.07, and the average number of repeating units is 131.

[0121] The polyimide polymer prepared in Comparative Example 1 is prepared into a polyimide film, and the steps are as follows:

[0122] Take part of the dried polyimide polymer and dissolve it in DMF, control the solid content to 15%, stir thoroughly to dissolve, evenly apply it on a clean silica glass plate, evacuate and let it stand for 2 hours, then heat it to 50°C and dry it for 5 hours, then heat it to 100°C and dry it for 8 hours, continue to heat it to 200°C and dry it for 3 hours, and after cooling, obtain the polyimide film 6FDA-TPMOH.

[0123] Its structure was confirmed by infrared spectroscopy and nuclear magnetic resonance hydrogen spectrum. The infrared (IR) spectrum of the prepared thin film product is shown in Figure 1d. The 2957-2855 cm -1 The CH stretching vibration peak of the methyl group is 1785 cm -1 and 1718cm -1 The characteristic peaks at 1614 cm-1 correspond to the asymmetric and symmetric stretching vibrations of C=O in the imide ring, respectively. -1 、1595cm -1 、1512cm -1 and 1484cm -1 Corresponding to the vibration of the aromatic ring skeleton, 1366 cm-1 Corresponding to CN stretching vibration; the H NMR spectrum (600 MHz, DMSO-d6) of the film product is shown in the attached Figure 5 As shown, the chemical shifts were assigned as δ = 9.33 (s, 1H), 8.15 (d, J = 8.1 Hz, 2H), 7.91 (s, 4H), 7.03 (d, J = 16.0 Hz, 6H), 6.74 (d, J = 6.9 Hz, 2H), 5.48 (s, 1H), 2.05 (s, 12H).

[0124] Performance Testing

[0125] The test method for the solubility of the polyimide films prepared in Examples 1 to 6 and Comparative Example 1 is as follows: 10 mg of the sample is dissolved in 1 mL of solvent: ++, soluble at room temperature; +, soluble when heated; ±, partially dissolved or expanded when heated; -, insoluble even when heated. The test results are shown in Table 1.

[0126] Table 1 Dissolution properties of polyimide films of Examples 1 to 6 and Comparative Example 1

[0127]

[0128] It can be seen from Table 1 that the polyimide film prepared in the present application has a good solubility in most solvents; compared with Comparative Example 1, the solubility of the polyimide film prepared in the present application in low boiling point solvents such as chloroform and dichloromethane is improved.

[0129] Furthermore, the glass transition temperature of the polyimide films of Examples 1 to 6 and Comparative Example 1 was tested by differential scanning calorimetry (DSC); the dielectric constant of the polyimide film at 1 MHz was measured by a capacitance test method, and the transmittance of the film at 400 nm was measured by a UV-visible spectrophotometer. The specific results are shown in Table 2.

[0130] Table 2 Properties of polyimide films of Examples 1 to 6 and Comparative Example 1

[0131] Glass transition temperature / ℃ Dielectric constant Light transmittance / % Example 1 314 2.61 82 Example 2 327 2.85 78 Example 3 351 2.92 75 Example 4 301 2.43 85 Example 5 315 2.59 83 Example 6 345 2.71 80 Comparative Example 1 346 4.11 68

[0132] It can be seen from Table 2 that the polyimide film prepared from the polyimide polymer provided by the present invention has a high glass transition temperature, a low dielectric constant and a high transmittance; compared with Comparative Example 1, the dielectric constant of the polyimide film prepared in the application is reduced and the transmittance is improved.

[0133] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A polyimide polymer, characterized in that The polyimide polymer has a structure shown in formula (I): Where n ranges from 50 to 500; R1 is selected from H, C 1～3 The alkyl group; R 2 Selected from -OR 3 The group is monosubstituted or polysubstituted, and the R 3 Selected from At least one of .

2. The polyimide polymer according to claim 1, characterized in that R1 is selected from H and methyl.

3. The polyimide polymer according to claim 1, characterized in that The polyimide polymer is selected from one of the following structural formulas:

4. The method for preparing a polyimide polymer according to any one of claims 1 to 3, characterized in that: The steps include: S1, under an inert atmosphere, mixing compound 1, aromatic dianhydride monomer, catalyst and a first strong polar solvent, heating and reacting to obtain a first reaction solution; S2, mixing the first reaction liquid and ethanol in a mass ratio of 1:(15-20), removing the ethanol, and performing a first drying to obtain an intermediate 1; S3, under inert atmosphere, intermediate 1, containing R 3 The halogenated silane of the group, imidazole and the second strong polar solvent are mixed and heated to react to obtain a second reaction solution; S4, mixing the second reaction liquid and ethanol in a mass ratio of 1:(15-20), removing the ethanol, and performing a second drying to obtain a polyimide polymer; The aromatic dianhydride monomer is selected from one of 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 4,4'-oxydiphthalic anhydride or 3,3',4,4'-benzophenonetetracarboxylic dianhydride; The structural formulas of the compound 1 and intermediate 1 are as follows:

5. The method for preparing a polyimide polymer according to claim 4, characterized in that: The catalyst is selected from at least one of isoquinoline, acetic anhydride, triethylamine or pyridine.

6. The method for preparing a polyimide polymer according to claim 4, characterized in that: In step S1, the amount of the catalyst used is 0.01 to 0.1 times the molar number of the aromatic diamine monomer.

7. The method for preparing a polyimide polymer according to claim 4, characterized in that: In step S3, the intermediate 1, containing R 3 The molar ratio of the halogenated silane and the imidazole of the group is 1:(1-4):(1-4).

8. The method for preparing a polyimide polymer according to claim 4, characterized in that: The first strong polar solvent and the second strong polar solvent are independently selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide and m-cresol.

9. A polyimide film, characterized in that: The polyimide film comprises the polyimide polymer according to any one of claims 1 to 3.

10. Use of the polyimide polymer according to any one of claims 1 to 3 or the polyimide film according to claim 9 in a dielectric layer of electronics or microelectronics or a substrate of a flexible display.

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