Polyimide precursor, modified polyimide and preparation method thereof, and polyimide precursor solution
By grafting siloxane-containing side chains onto the polyimide backbone and hydrolyzing them to form SiO2, combined with strong electron-withdrawing groups, the problem of balancing light transmittance and heat resistance in polyimides was solved, resulting in modified polyimide materials with high light transmittance and high thermal stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-06
- Publication Date
- 2026-03-10
AI Technical Summary
Existing polyimides are difficult to improve both light transmittance and heat resistance at the same time. Introducing inorganic fillers affects optical properties, and strong electron-withdrawing groups reduce heat resistance.
Modified polyimide is prepared by grafting siloxane-containing side chains onto the polyimide backbone, forming uniformly distributed SiO2 through hydrolysis and condensation, and combining strong electron-withdrawing groups to reduce the conjugation effect.
It achieves high light transmittance and good thermal stability of polyimide materials under high temperature conditions, making it suitable for high-tech applications such as flexible displays.
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Figure CN121628099A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electronic chemicals technology, specifically relating to a polyimide precursor, a modified polyimide, a method for preparing the same, and a polyimide precursor solution. Background Technology
[0002] Currently, colored polyimides are widely used in flexible displays due to their excellent overall high-temperature resistance and mechanical properties. In contrast, high-transparency, high-temperature-resistant polyimides have even greater development potential in the flexible display field. However, the control of the optical transparency and high-temperature resistance of polyimides is mutually restrictive, making it difficult to improve both simultaneously. During the synthesis of polyimides, the molecular chains formed by the crosslinking of diamines and dianhydrides exhibit a strong conjugation effect, easily resulting in a yellow film that severely affects its light transmittance. Currently, introducing strong electron-withdrawing groups or asymmetric macromolecular groups reduces the "CTC" effect of the polyimide molecular chains, improving the transparency of polyimide films. However, this also reduces the heat resistance due to the reduced strong complexation effect of the molecular chains. Introducing inorganic fillers into the polyimide system can disperse heat, thereby improving the heat resistance of polyimides. However, due to their spatial particle size, excessive amounts can affect the optical properties of the polyimide film. Summary of the Invention
[0003] To address the problem that existing polyimides struggle to balance light transmittance and heat resistance, this invention provides a polyimide precursor, a modified polyimide, a method for preparing the same, and a polyimide precursor solution.
[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: On one hand, the present invention provides a polyimide precursor comprising a polyimide acid backbone and a segment of structural formula 1 grafted onto the polyimide acid backbone: Structural Formula 1 R1 is selected from divalent organic groups with substituted or unsubstituted C2~C9 aliphatic hydrocarbon structures; R11, R12, and R13 are each independently selected from H or C1 to C5 alkyl groups.
[0005] Optionally, the polyimide precursor includes the structural units shown in Formula 2 and Formula 3: Structural Formula 2 Structural Formula 3 The molar ratio of the structural unit shown in structural formula 2 to the structural unit shown in structural formula 3 is (0.6~0.9):(0.1~0.4). R1 is selected from C2-C9 alkyl groups or alkyl groups containing amino groups; R2 is selected from substituted or unsubstituted C6-C30 aromatic divalent organic groups or substituted or unsubstituted C1-C20 aliphatic hydrocarbon divalent organic groups. R3 is selected from tetravalent organic groups with substituted or unsubstituted C6-C30 aromatic structures; R4 is selected from substituted or unsubstituted C6-C30 aromatic trivalent organic groups and substituted or unsubstituted C1-C20 aliphatic hydrocarbon trivalent organic groups; R11, R12, and R13 are each independently selected from H or C1 to C5 alkyl groups.
[0006] Optionally, R2 is selected from substituted or unsubstituted C6-C30 aromatic divalent organic groups containing strong electron-withdrawing groups; R3 is selected from tetravalent organic groups with aromatic structures containing strong electron-withdrawing groups, either substituted or unsubstituted (C6-C30).
[0007] Optionally, R2 is selected from one or more of the following structural formulas: R3 is selected from one or more of the following structural formulas: .
[0008] Optionally, R4 is selected from one or more of the following structural formulas: .
[0009] In another aspect, the present invention provides a polyimide precursor solution, comprising a solvent and a polyimide precursor as described above, wherein the mass content of the polyimide precursor is 10% to 20% based on the total mass of the polyimide precursor solution being 100%.
[0010] In another aspect, the present invention provides a modified polyimide derived from the polyimide precursor described above, wherein the modified polyimide comprises a polyimide backbone and SiO2, wherein the SiO2 is bonded to the polyimide backbone through segments containing amide groups.
[0011] Optionally, the modified polyimide includes structural units shown in Formula 4 and Formula 5: Structural Formula 4 Structural Formula 5 The molar ratio of the structural unit shown in structural formula 4 to the structural unit shown in structural formula 5 is (0.6~0.9):(0.1~0.4). R1 is selected from C2-C9 alkyl groups or alkyl groups containing amino groups; R2 is selected from substituted or unsubstituted C6-C30 aromatic divalent organic groups or substituted or unsubstituted C1-C20 aliphatic hydrocarbon divalent organic groups. R3 is selected from tetravalent organic groups with substituted or unsubstituted C6-C30 aromatic structures; R4 is selected from substituted or unsubstituted C6-C30 aromatic trivalent organic groups and substituted or unsubstituted C1-C20 aliphatic hydrocarbon trivalent organic groups; R5 represents SiO2 particles.
[0012] In another aspect, the present invention provides a method for preparing the polyimide precursor as described above, comprising the following operations: Polyamic acid is obtained by polymerizing a diacid anhydride and a diamine, wherein at least part of the diamine has a carboxyl group. Polyamic acid was reacted with the compound shown in structural formula 6 under aqueous and acidic conditions to obtain a polyimide precursor; Structural Formula 6 Wherein, R1 is selected from C2~C9 alkyl or amino-containing alkyl; R11, R12, and R13 are each independently selected from H or C1 to C5 alkyl groups.
[0013] Furthermore, the present invention provides a method for preparing the modified polyimide as described above, comprising the following operations: The coating is performed using the polyimide precursor solution described above; The polyimide is obtained by heating and imidization. During the heating process, the siloxane in the chain segment shown in Formula 1 is partially hydrolyzed and condensed to obtain SiO2 particles, thus obtaining the modified polyimide.
[0014] The polyimide precursor provided by this invention is used to prepare modified polyimides. Compared with existing polyimide acids, the polyimide precursor provided by this invention has siloxane-containing side chains grafted onto the polyimide acid backbone. During the imidization process of the polyimide precursor, the siloxane-containing side chains hydrolyze and condense to form SiO2. This structure ensures that the formed SiO2 is uniformly distributed in the polyimide, avoiding agglomeration, thus having a low impact on the light transmittance of the polyimide. At the same time, since a small amount of SiO2 is bonded to the polyimide backbone through chemical bonds, the bonding strength between the polyimide and SiO2 is improved, and the dispersion uniformity is also improved, which is beneficial to improving the overall thermal stability of the polyimide. This makes the material suitable for applications in high-temperature environments while ensuring sufficient light transmission, which is particularly important for high-tech applications such as flexible displays. Detailed Implementation
[0015] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0016] This invention provides a polyimide precursor comprising a polyimide acid backbone and a segment of structural formula 1 grafted onto the polyimide acid backbone: Structural Formula 1 R1 is selected from divalent organic groups with substituted or unsubstituted C2~C9 aliphatic hydrocarbon structures; R11, R12, and R13 are each independently selected from H or C1 to C5 alkyl groups.
[0017] Compared to existing polyimide acids, the polyimide precursor provided by this invention incorporates siloxane-containing side chains on the polyimide backbone through grafting. During the imidization process of the polyimide precursor, the siloxane-containing side chains undergo hydrolysis and condensation to form SiO2. This structure ensures that the formed SiO2 is uniformly distributed in the polyimide, avoiding agglomeration and thus having a low impact on the light transmittance of the polyimide. At the same time, since a small amount of SiO2 is bonded to the polyimide backbone through chemical bonds, the bonding strength between the polyimide and SiO2 is improved, as is the dispersion uniformity, which is beneficial to improving the overall thermal stability of the polyimide. This makes the material suitable for applications in high-temperature environments while ensuring sufficient light transmission, which is particularly important for high-tech applications such as flexible displays.
[0018] In some embodiments, the polyimide precursor comprises the structural unit shown in Formula 2 and the structural unit shown in Formula 3: Structural Formula 2 Structural Formula 3 The molar ratio of the structural unit shown in structural formula 2 to the structural unit shown in structural formula 3 is (0.6~0.9):(0.1~0.4). R1 is selected from C2-C9 alkyl groups or alkyl groups containing amino groups; R2 is selected from substituted or unsubstituted C6-C30 aromatic divalent organic groups or substituted or unsubstituted C1-C20 aliphatic hydrocarbon divalent organic groups. R3 is selected from tetravalent organic groups with substituted or unsubstituted C6-C30 aromatic structures; R4 is selected from substituted or unsubstituted C6-C30 aromatic trivalent organic groups or substituted or unsubstituted C1-C20 aliphatic hydrocarbon trivalent organic groups. R11, R12, and R13 are each independently selected from H or C1 to C5 alkyl groups.
[0019] In the structural units shown in Structural Formula 2 and Structural Formula 3, R3 is derived from the polymeric monomer dicarboxylic acid anhydride, and R2 and R4 are derived from the polymeric monomer diamine. Therefore, in the synthesis of this polyimide precursor, a diamine with a carboxyl group is used in the polymeric monomer, and then the diamine with the carboxyl group reacts with a siloxane with a urea group to introduce the siloxane into the structural unit shown in Structural Formula 3.
[0020] In some embodiments, R2 is selected from C6-C30 aromatic divalent organic groups; R3 is selected from tetravalent organic groups with aromatic structures from C6 to C30.
[0021] In some embodiments, R2 is selected from substituted or unsubstituted C6-C30 aromatic divalent organic groups containing strong electron-withdrawing groups; R3 is selected from tetravalent organic groups with aromatic structures containing strong electron-withdrawing groups, either substituted or unsubstituted (C6-C30).
[0022] When R2 and R3 contain strong electron-withdrawing groups, the conjugation effect of the polyimide molecular chain can be greatly reduced, effectively improving the transparency of the polyimide prepared from the polyimide precursor, so that the obtained polyimide has strong light transmittance and good thermal stability.
[0023] In some embodiments, the electron-withdrawing group is selected from one or more of fluoroalkyl and carbonyl groups.
[0024] In some embodiments, R2 is selected from one or more of the following structural formulas: R3 is selected from one or more of the following structural formulas: .
[0025] In some embodiments, R4 is selected from one or more of the following structural formulas: .
[0026] Another embodiment of the present invention provides a polyimide precursor solution comprising a solvent and a polyimide precursor as described above, wherein the mass content of the polyimide precursor is 10% to 20% based on the total mass of the polyimide precursor solution being 100%.
[0027] The polyimide precursor solution is a dispersion of the polyimide precursor, which facilitates operations such as coating on the polyimide precursor.
[0028] In some embodiments, the solvent is an organic solvent.
[0029] In some embodiments, the solvent includes at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, and xylene.
[0030] In some embodiments, the polyimide precursor solution further includes HCl, which is used to promote the hydrolysis of siloxane groups in the polyimide precursor.
[0031] Another embodiment of the present invention provides a modified polyimide derived from the polyimide precursor described above. The modified polyimide comprises a polyimide backbone and SiO2, wherein the SiO2 is bonded to the polyimide backbone via segments containing amide groups, wherein the polyimide backbone is obtained by imidization of the polyimide acid backbone, and the SiO2 is obtained by hydrolysis and condensation of siloxane.
[0032] The modified polyimide contains uniformly dispersed SiO2, and the SiO2 is linked to the polyimide backbone through segmental bonds containing amide groups, which effectively improves the thermal stability of the modified polyimide and avoids the influence of SiO2 agglomeration on the light transmittance of the modified polyimide, thus achieving both high light transmittance and high thermal stability.
[0033] In some embodiments, the modified polyimide comprises the structural units shown in Formula 4 and Formula 5: Structural Formula 4 Structural Formula 5 The molar ratio of the structural unit shown in structural formula 4 to the structural unit shown in structural formula 5 is (0.6~0.9):(0.1~0.4). R1 is selected from C2-C9 alkyl groups or alkyl groups containing amino groups; R2 is selected from substituted or unsubstituted C6-C30 aromatic divalent organic groups or substituted or unsubstituted C1-C20 aliphatic hydrocarbon divalent organic groups. R3 is selected from tetravalent organic groups with substituted or unsubstituted C6-C30 aromatic structures; R4 is selected from substituted or unsubstituted C6-C30 aromatic trivalent organic groups or substituted or unsubstituted C1-C20 aliphatic hydrocarbon trivalent organic groups. R5 represents SiO2 particles.
[0034] In some embodiments, R2 is selected from substituted or unsubstituted C6-C30 aromatic divalent organic groups containing strong electron-withdrawing groups; R3 is selected from tetravalent organic groups with aromatic structures containing strong electron-withdrawing groups, either substituted or unsubstituted (C6-C30).
[0035] When R2 and R3 contain strong electron-withdrawing groups, the conjugation effect of the polyimide molecular chain can be greatly reduced, effectively improving the transparency of the modified polyimide, so that the obtained polyimide has strong light transmittance and good thermal stability.
[0036] In some embodiments, the electron-withdrawing group is selected from one or more of fluoroalkyl and carbonyl groups.
[0037] In some embodiments, R2 is selected from one or more of the following structural formulas: R3 is selected from one or more of the following structural formulas: .
[0038] In some embodiments, R4 is selected from one or more of the following structural formulas: .
[0039] Another embodiment of the present invention provides a method for preparing the polyimide precursor as described above, comprising the following operations: Polyamic acid is obtained by polymerizing a diacid anhydride and a diamine, wherein at least part of the diamine has a carboxyl group. Polyamic acid was reacted with the compound shown in structural formula 6 under aqueous and acidic conditions to obtain a polyimide precursor; Structural Formula 6 Wherein, R1 is selected from C2~C9 alkyl or amino-containing alkyl; R11, R12, and R13 are each independently selected from H or C1 to C5 alkyl groups.
[0040] The method for preparing the polyimide precursor involves polymerizing a carboxyl-containing diamine and a diacid anhydride to obtain polyimide acid. This results in a large number of stable carboxyl groups on the polyimide acid molecular chain. The carboxyl groups interact with the urea groups of the compound shown in structural formula 6 through intermolecular forces to form hydrogen bonds. This allows the compound shown in structural formula 6 to be well modified on the surface of the polyimide acid molecular chain. Under aqueous and acidic conditions, the siloxane portion of the compound shown in structural formula 6 is partially hydrolyzed to form silanol groups. These silanol groups can be dehydrated during the subsequent imidization of the polyimide acid to form stable SiO2 particles.
[0041] In some embodiments, the polymerization reaction is carried out at a temperature of 0-60°C under a protective atmosphere.
[0042] In some embodiments, the polymerization reaction is carried out in an organic solvent.
[0043] In some embodiments, the compound represented by structural formula 6 includes one or more of the following compounds:
[0044] In some embodiments, the molar ratio of the dicarboxylic anhydride to the diamine is (1~1.02):1.
[0045] In some embodiments, the diamine includes a carboxyl-containing diamine and a diamine containing a strong electron-withdrawing group, wherein the molar ratio of the carboxyl-containing diamine to the diamine containing the strong electron-withdrawing group is (1.5~9):1.
[0046] In some embodiments, the molar ratio of the compound represented by structural formula 6 to the carboxyl-containing diamine is (2~15):100.
[0047] If the amount of the compound shown in structural formula 6 is too small, it will be difficult to improve the thermal stability of the modified polyimide; if the amount of the compound shown in structural formula 6 is too large, it will easily cause the aggregation of silica particles, which is not conducive to improving the light transmittance of the modified polyimide.
[0048] Another embodiment of the present invention provides a method for preparing the modified polyimide as described above, comprising the following operations: The coating is performed using the polyimide precursor solution described above; The polyimide is obtained by heating and imidization. During the heating process, the siloxane in the chain segment shown in Formula 1 is partially hydrolyzed and condensed to obtain SiO2 particles, thus obtaining the modified polyimide.
[0049] In some embodiments, the imidization treatment is performed in a protective atmosphere.
[0050] In some embodiments, the heating temperature for the imidization treatment is 60°C to 300°C.
[0051] In a preferred embodiment, the imidization treatment is performed by gradient heating, with the heating conditions being (60~100℃) / (0.5~1.5h) + (100~140℃) / (0.5~1.5h) + (140~160℃) / (0.5~1.5h) + (160~200℃) / (0.5~1.5h) + (220~260℃) / (0.5~1.5h) + (260~300℃) / (0.5~1.5h).
[0052] In some embodiments, the polyimide precursor solution is coated onto a substrate, and after imidization treatment, the resulting modified polyimide is detached from the substrate to obtain a modified polyimide film.
[0053] In some embodiments, the substrate is selected from a glass substrate or an alumina ceramic substrate.
[0054] The present invention will be further illustrated by the following examples.
[0055] Example 1 This embodiment illustrates the modified polyimide and its preparation method disclosed in this invention, including the following operations: (1) Preparation of polyamic acid solution Under nitrogen protection at 50°C, 7.9227 g (23.44 mmol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (TFODA) and 0.8915 g (5.86 mmol) of 3,5-diaminobenzoic acid were dissolved in 88 g of DMAc (N,N-dimethylacetamide). The mixture was stirred until the solids were completely dissolved. While maintaining the temperature, 13.0 g (29.30 mmol) of hexafluorodianhydride (6FDA) was added in batches, and the mixture was stirred continuously for 6 hours to obtain a polyamic acid solution with a solid content of 22%.
[0056] (2) Preparation of polyimide precursor solution The prepared polyamic acid solution was transferred to a 500 mL three-necked flask and cooled to room temperature (25 °C) under nitrogen protection by vigorous stirring. Then, 0.1312 g (0.59 mmol) of 3-ureapropyltrimethoxysilane (TMPU), 0.1 g (5.6 mmol) of H2O, and 0.0215 g (0.59 mmol) of HCl were added to the above system and stirring was continued for 12 h to obtain a polyimide precursor solution.
[0057] (3) Preparation of modified polyimide composite film The prepared polyimide precursor solution was filtered through a 0.45 μm PTFE syringe filter to remove insoluble matter. After the filtrate was allowed to stand and degas, it was evenly coated onto a clean glass plate using a scraper. The glass plate was placed in a clean, temperature-controlled nitrogen-protected oven and subjected to thermal imidization treatment according to the following program: 80℃ / 1h + 120℃ / 1h + 150℃ / 1h + 180℃ / 1h + 250℃ / 1h + 280℃ / 1h. During this process, 3-ureapropyltrimethoxysilane pyrolyzes to form SiO2. After natural cooling, the glass plate was immersed in deionized water and then placed in a clean, forced-air drying oven to dry at 100℃ for 3 hours to obtain the modified polyimide composite film.
[0058] The synthesis process is as follows: Example 2 This embodiment illustrates the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, with the following differences: In step (2), the amount of 3-ureapropyltrimethoxysilane added is 0.01g.
[0059] Example 3 This embodiment illustrates the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, with the following differences: In step (2), the amount of 3-ureapropyltrimethoxysilane added is 0.5g.
[0060] Example 4 This embodiment illustrates the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, with the following differences: In step (2), 3-ureapropyltriethoxysilane is used instead of 3-ureapropyltrimethoxysilane.
[0061] Example 5 This embodiment illustrates the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, with the following differences: In step (2), 3-[(2-ureidoethyl)amino]propyltrimethoxysilane is used instead of 3-ureidopropyltrimethoxysilane.
[0062] Example 6 This embodiment illustrates the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, with the following differences: In step (1), 4,4'-diaminodiphenyl ether is used instead of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether.
[0063] Example 7 This embodiment illustrates the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, with the following differences: In step (1), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is used instead of hexafluorodianhydride.
[0064] Comparative Example 1 This comparative example is used to illustrate the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, with the following differences: In step (2), 3-ureapropyltrimethoxysilane is not added.
[0065] In step (3), silica particles are added, wherein the silica particles contain the same amount of silicon as the total silicon content of 3-ureapropyltrimethoxysilane in Example 1.
[0066] Comparative Example 2 This comparative example is used to illustrate the modified polyimide and its preparation method disclosed in this invention, including most of the operations in Example 1, except that...
[0067] In step (1), 3,5-diaminobenzoic acid is not added.
[0068] Performance testing The modified polyimide prepared above was subjected to the following performance tests: Transmittance test: Refer to standard GB / T2410-2008 for testing.
[0069] Thermal stability test: The thermal stability of the sample was tested using a differential scanning calorimeter. 15 mg of the thin film sample was placed in an alumina crucible, the nitrogen gas valve was opened, the pressure was set to 0.1 MPa, the flow rate was set to 150 mL / min, the low temperature was set to -75℃, the test start temperature was set to 30℃, the test end temperature was set to 600℃, and the heating rate was set to 5℃ / min. The heat flow curve was obtained, and the position of the exothermic peak was observed. The highest exothermic peak is the decomposition temperature.
[0070] The test results are entered into Table 1.
[0071] Table 1 As can be seen from the test results in Table 1, compared with Comparative Example 1 which directly added silica and Comparative Example 2 which directly added silane coupling agent, the modified polyimide prepared by the preparation method provided in this invention has significantly higher light transmittance. This indicates that by grafting siloxane-containing side chains onto the main chain of polyimide acid and then hydrolyzing and condensing the siloxane-containing side chains during imidization to form SiO2, the dispersion uniformity is better than that of the traditional method, which can reduce the impact on the light transmittance of polyimide.
[0072] As can be seen from the test results of Example 1 and Comparative Examples 1 and 2, under the same silicon content, compared with other methods of introducing SiO2, the SiO2 formed by grafting hydrolysis in Example 1 is bonded to the polyimide backbone through chemical bonds, which improves the bonding strength between polyimide and SiO2, and the resulting modified polyimide has higher thermal stability.
[0073] The test results of Examples 1, 6 and 7 show that introducing strong electron-withdrawing groups into the raw materials diacid anhydride and diamine is beneficial to reducing the conjugation effect of the polyimide molecular chain, so that the obtained polyimide has strong light transmittance and good thermal stability.
[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A polyimide precursor, characterized in that, comprising a polyimide acid main chain and a segment represented by structural formula 1 grafted to the polyimide acid main chain: structural formula 1 wherein R1 is selected from a substituted or unsubstituted divalent organic group of C2-C9 aliphatic structure; R11, R12, R13 are each independently selected from H or C1-C5 alkyl.
2. The polyimide precursor according to claim 1, wherein The polyimide precursor comprises a structural unit represented by structural formula 2 and a structural unit represented by structural formula 3: structural formula 2 structural formula 3 wherein the molar ratio of the structural unit represented by structural formula 2 to the structural unit represented by structural formula 3 is (0.6-0.9):(0.1-0.4); R1 is selected from C2-C9 alkyl or amino-containing alkyl; R2 is selected from a substituted or unsubstituted divalent organic group of C6-C30 aromatic structure, a substituted or unsubstituted divalent organic group of C1-C20 aliphatic structure; R3 is selected from a substituted or unsubstituted tetravalent organic group of C6-C30 aromatic structure; R4 is selected from a substituted or unsubstituted trivalent organic group of C6-C30 aromatic structure, a substituted or unsubstituted trivalent organic group of C1-C20 aliphatic structure; R11, R12, R13 are each independently selected from H or C1-C5 alkyl.
3. The polyimide precursor according to claim 2, wherein R2 is selected from a substituted or unsubstituted divalent organic group of C6-C30 aromatic structure containing a strong electron-withdrawing group; R3 is selected from a substituted or unsubstituted tetravalent organic group of C6-C30 aromatic structure containing a strong electron-withdrawing group.
4. The polyimide precursor according to claim 2 or 3, characterized in that, R2 is selected from one or more of the following structural formulas: R3 is selected from one or more of the following structural formulas: 。 5. The polyimide precursor according to claim 2, wherein R4 is selected from one or more of the following structural formulas: 。 6. A polyimide precursor solution characterized by comprising: comprising a solvent and the polyimide precursor according to any one of claims 1-5, wherein the mass content of the polyimide precursor is 10%-20% based on the total mass of the polyimide precursor solution.
7. A modified polyimide characterized by, derived from the polyimide precursor according to any one of claims 1-5, the modified polyimide comprising a polyimide main chain and SiO2, wherein SiO2 is linked to the polyimide main chain through a segment containing an amide group.
8. The modified polyimide according to claim 7, wherein The modified polyimide comprises a structural unit represented by structural formula 4 and a structural unit represented by structural formula 5: structural formula 4 structural formula 5 wherein the molar ratio of the structural unit represented by structural formula 4 to the structural unit represented by structural formula 5 is (0.6-0.9):(0.1-0.4); R1 is selected from C2-C9 alkyl or amino-containing alkyl; R2 is selected from a substituted or unsubstituted divalent organic group of C6-C30 aromatic structure, a substituted or unsubstituted divalent organic group of C1-C20 aliphatic structure; R3 is selected from a substituted or unsubstituted tetravalent organic group of C6-C30 aromatic structure; R4 is selected from a substituted or unsubstituted trivalent organic group of C6-C30 aromatic structure, a substituted or unsubstituted trivalent organic group of C1-C20 aliphatic structure; R5 is a SiO2 particle.
9. The method of producing a polyimide precursor according to any one of claims 1 to 5, wherein comprising the following operations: polymerizing a diacid anhydride and a diamine, at least part of which has a carboxyl group, to obtain a polyamide acid; reacting the polyamide acid with a compound represented by structural formula 6 under aqueous and acidic conditions to obtain a polyimide precursor; Structure 6 wherein R1 is selected from C2-C9 alkyl or aminoalkyl; R11, R12, R13 are each independently selected from H or C1-C5 alkyl.
10. The method for producing a modified polyimide according to claim 7 or 8, wherein The method comprises the following operations: The polyimide precursor solution according to claim 6 is used for coating; The imidization treatment is performed by heating, and in the process of heating, the siloxane part in the chain segment shown in structure 1 is hydrolyzed and condensed to obtain SiO2 particles, thereby obtaining the modified polyimide.