Pyridine-containing terphenyl diamines, colorless transparent polyimides, and methods of making and using the same

Abstract

The application belongs to the field of optical films, and particularly relates to a pyridine-containing terphenyl diamine, a colorless and transparent polyimide and a preparation method and application thereof. The structural formula of the pyridine-containing terphenyl diamine is shown as formula (1). The application adjusts the substituents on the diamine monomer and changes the methyl of the nitrogen atom para-position on the pyridine, designs six different pyridine-containing terphenyl diamines introduced into the polyimide, adjusts the charge transfer effect, intermolecular distance and folding degree of the molecular chain of the polyimide, and obtains the colorless and transparent polyimide film with heat resistance, good optical performance and tensile strength. The application has potential application value in the field of flexible devices.

Description

Technical Field

[0001] This invention belongs to the field of optical materials technology, specifically relating to a pyridine-containing terphenyldiamine, a colorless and transparent polyimide, its preparation method, and its application. Background Technology

[0002] With the development of technology, novel flexible display technology has attracted increasing attention due to its numerous advantages, including low power consumption, thinness, lightness, convenience, and aesthetics. The base film material is an indispensable optical component. Traditional flexible substrate materials are prone to yellowing under high temperatures or chemical environments, affecting display performance. Furthermore, their insufficient mechanical properties make them unable to withstand repeated bending and stretching, failing to meet the high requirements of modern flexible display technology. Polyimide, due to the imide bonds in its main chain, possesses excellent comprehensive properties, such as heat resistance and mechanical properties. Traditional polyimide typically exhibits a golden-yellow color and is characterized by a highly conjugated molecular chain structure with strong intermolecular / intramolecular charge interactions, limiting its application in optical engineering. Therefore, the optical properties of polyimide can be improved by adjusting the charge transfer complexation effect between polyimide molecules, thereby meeting the requirements for use as a flexible display base film.

[0003] Currently, novel flexible display technologies require the base film to possess excellent optical and heat resistance properties, as well as superior mechanical properties to withstand repeated bending and stretching. This poses a significant challenge for colorless and transparent polyimide.

[0004] Chinese patent application CN117843499A describes a class of asymmetric diamines, high-performance polyimides, their preparation methods, and applications. This invention designs four different asymmetric diamines by adjusting the substituents at the second position on the diamine monomer and introducing them into polyimides. By adjusting the charge transfer effect and intermolecular distance of the polyimide chains, a colorless and transparent polyimide film with both heat resistance and high transmittance is obtained. However, the mechanical properties of this colorless and transparent polyimide film are still not ideal. Summary of the Invention

[0005] To address the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a pyridine-containing triphenyldiamine.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned pyridine-containing triphenyldiamine.

[0007] Another object of the present invention is to provide a colorless and transparent polyimide containing pyridine-3-phenylenediamine. The present invention introduces an electron-deficient pyridine structure into the main chain, designs a uniquely curved terphenyl structure, and adjusts the substituents to design six novel diamines with different structures. By adjusting the charge transfer effect and interchain spacing of the polyimide chain, and constructing a helical folded structure, a colorless and transparent polyimide film with heat resistance, good transmittance, and mechanical properties is obtained.

[0008] The present invention also provides the application of the above-mentioned colorless and transparent polyimide containing pyridine triphenyldiamine in the field of flexible electronics.

[0009] The technical solution of this invention is as follows:

[0010] The pyridine-containing triphenyldiamine proposed in this invention has the structural formula shown in formula (1):

[0011]

[0012] In the formula, R1 is trifluoromethyl, methyl or fluorine; R2 is hydrogen or methyl.

[0013] In this invention, the diamine with R1 being fluorine and R2 being hydrogen is abbreviated as 2F-PTPDA, and its structural formula is:

[0014]

[0015] Wherein, R1 is a trifluoromethyl and R2 is a hydrogen-containing diamine, abbreviated as 6F-PTPDA, with the following structural formula:

[0016]

[0017] In this case, the diamine with R1 being methyl and R2 being hydrogen is abbreviated as 6H-PTPDA, and its structural formula is:

[0018]

[0019] In this case, a diamine with R1 being a fluorine group and R2 being a methyl group is abbreviated as 2F-MPTPDA, and its structural formula is:

[0020]

[0021] Wherein, R1 is a trifluoromethyl and R2 is a methyl diamine, abbreviated as 6F-MPTPDA, with the following structural formula:

[0022]

[0023] In this case, the diamine with R1 being methyl and R2 being methyl is abbreviated as 6H-MPTPDA, and its structural formula is:

[0024]

[0025] The present invention provides a method for preparing pyridine-containing triphenyldiamine, comprising the following steps:

[0026] S1. A bromine-substituted 4-nitrobenzene compound, pinacol diborate, potassium acetate, 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride, and 1,4-dioxane were placed in a reaction vessel, stirred and heated to 80-90°C under inert gas conditions, and refluxed for 21-24 hours to obtain monomer M.

[0027] S2. Monomer M, dibromo-substituted pyridine compound, potassium carbonate, water, tetra(triphenylphosphine)palladium, ethanol and toluene are placed in a reaction vessel, stirred and heated to 100-120°C under inert gas conditions, and refluxed for 20.5-24 hours to obtain pyridine-containing triphenyl dinitro monomer NM.

[0028] S3. At room temperature, the pyridine-containing terphenyl dinitro monomer NM, anhydrous ethanol and Pd / C are added to the reaction vessel. Under inert gas conditions, the mixture is stirred and heated to 80°C for reflux. Hydrazine hydrate is added dropwise to the mixed solution in the reaction vessel. After the addition is complete, the reaction is maintained at 80°C for 10-12 hours to obtain the pyridine-containing terphenyl diamine.

[0029] The bromine-substituted 4-nitrobenzene compound in step S1 is 1-bromo-2-fluoro-4-nitrobenzene, 2-bromo-5-nitrotoluene, or 2-bromo-5-nitrotrifluorotoluene; the dibromine-substituted pyridine compound in step S2 is 3,5-dibromopyridine or 3,5-dibromo-4-methylpyridine.

[0030] In step S1: when the bromine-substituted 4-nitrobenzene compound is 1-bromo-2-fluoro-4-nitrobenzene, the monomer M obtained is 2-(2-fluoro-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane, with the structural formula [insert structural formula here].

[0031] When the bromine-substituted 4-nitrobenzene compound is 2-bromo-5-nitrotrifluorotoluene, the monomer M obtained in step S1 is 2-(2-trifluoromethyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxorane, with the structural formula [insert structural formula here].

[0032] When the bromine-substituted 4-nitrobenzene compound is 2-bromo-5-nitrotoluene, the monomer M obtained in step S1 is 2-(2-methyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxorane, with the structural formula [insert structural formula here].

[0033] In step S1, the molar ratio of the bromine-substituted 4-nitrobenzene compound, pinacol diborate, potassium acetate, and 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride is 10 mmol:12 mmol:32.24 mmol:0.21 mmol. The volume of 1,4-dioxane as the solvent does not need to be strictly limited.

[0034] In step S1, after the reflux is completed, the following steps are also included: cooling the reaction solution; diluting the mixture with ethyl acetate and washing it three times with deionized water; drying the organic layer with anhydrous magnesium sulfate, then removing the anhydrous magnesium sulfate by filtration, concentrating the filtrate under vacuum to obtain the crude product, and finally purifying the crude product by silica gel column chromatography.

[0035] The eluent for the silica gel column chromatography is dichloromethane:petroleum ether in a volume ratio of 1:8 to 10.

[0036] In step S2: when the monomer M is 2-(2-fluoro-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane and the dibromo-substituted pyridine compound is 3,5-dibromopyridine, the resulting pyridine-containing terphenyl dinitro monomer NM-1 has the following structural formula:

[0037] When the monomer M is 2-(2-trifluoromethyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxorane and the dibromo-substituted pyridine compound is 3,5-dibromopyridine, the resulting pyridine-containing terphenyl dinitro monomer NM-2 has the following structural formula:

[0038] When the monomer M is 2-(2-methyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxorane and the dibromo-substituted pyridine compound is 3,5-dibromopyridine, the resulting pyridine-containing terphenyl dinitro monomer NM-3 has the following structural formula:

[0039] When the monomer M is 2-(2-fluoro-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane and the dibromo-substituted pyridine compound is 3,5-dibromo-4-methylpyridine, the resulting pyridine-containing terphenyl dinitro monomer NM-4 has the following structural formula:

[0040] When the monomer M is 2-(2-trifluoromethyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane and the dibromo-substituted pyridine compound is 3,5-dibromo-4-methylpyridine, the resulting pyridine-containing terphenyl dinitro monomer NM-5 has the following structural formula:

[0041] When the monomer M is 2-(2-methyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane and the dibromo-substituted pyridine compound is 3,5-dibromo-4-methylpyridine, the resulting pyridine-containing terphenyl dinitro monomer NM-6 has the following structural formula:

[0042] In step S2, the molar ratio of monomer M, dibromo-substituted pyridine compound, potassium carbonate, and tetrakis(triphenylphosphine)palladium is 3:1:13.5:0.15. The amounts of toluene, ethanol, and water used as solvents are not strictly limited, but a preferred molar volume ratio of the dibromo-substituted pyridine compound to toluene, ethanol, and water is 2 mmol:8 mL:4 mL:8 mL.

[0043] In step S2, after the condensation and reflux are completed, the following steps are also included: diluting the mixture with dichloromethane and washing it three times with deionized water; drying the organic layer with anhydrous magnesium sulfate, then removing the anhydrous magnesium sulfate by filtration, concentrating the filtrate under vacuum to obtain the crude product, and finally purifying the crude product by silica gel column chromatography.

[0044] The eluent used in the silica gel column chromatography was dichloromethane:petroleum ether in a volume ratio of 4:1.

[0045] In step S3, the ratio of the pyridine-containing terphenyl dinitro monomer NM, Pd / C, and anhydrous ethanol is 3g:0.68g:60mL; the ratio of the pyridine-containing terphenyl dinitro monomer NM to hydrazine hydrate is 3g:6.32mL.

[0046] In step S3, the hydrazine hydrate is added at a rate of one drop every two seconds.

[0047] In step S3, after the isothermal reaction is completed, the process further includes: filtering while hot to remove Pd / C, pouring the filtrate into cold water, adding sodium chloride while stirring until a solid precipitates, filtering out the solid and washing it with an ethanol / water mixture, and vacuum drying the filtered solid to obtain a pyridine-containing triphenyldiamine monomer.

[0048] In step S1, it is preferable to perform condensation reflux at 80°C for 24 hours;

[0049] In step S2, it is preferable to stir and heat to 110°C for condensation and reflux for 24 hours;

[0050] In step S3, after the hydrazine hydrate is added, it is preferable to maintain the reaction at 80°C for 12 hours.

[0051] The present invention also provides a polyimide polymer prepared by polycondensation reaction of the above-mentioned pyridine-containing triphenyldiamine monomer, which comprises the following repeating units:

[0052]

[0053] Wherein, R1 is fluorinated, trifluoromethyl or methyl, R2 is hydrogen or methyl, and n is preferably 43 to 77.

[0054] In formula (2) of the present invention, R2 is hydrogen, R1 is fluorinated, trifluoromethyl or methyl, and the polyimide polymer is abbreviated as 6FDA-2F-PTPDA, 6FDA-6F-PTPDA or 6FDA-6H-PTPDA respectively; R2 is methyl, R1 is fluorinated, trifluoromethyl or methyl, and the polyimide polymer is abbreviated as 6FDA-2F-MPTPDA, 6FDA-6F-MPTPDA or 6FDA-6H-MPTPDA respectively.

[0055] The pyridine-containing triphenyldiamine monomer of the present invention can be further polycondensed to prepare a polyimide polymer, comprising the following steps: placing the pyridine-containing triphenyldiamine monomer of formula (1), a tetracarboxylic acid dianhydride monomer and m-cresol in a reaction vessel, heating to 60-80°C (preferably 80°C), stirring at a constant temperature for 0.5-1h (preferably 1h), adding a catalyst, then heating to 180-185°C and stirring at a constant temperature for 8-10h (preferably stirring at 180°C for 10h), and preparing a polyimide polymer by a one-step polycondensation reaction;

[0056] The structural formula of the tetracarboxylic acid dianhydride monomer is shown below (abbreviated as 6FDA):

[0057]

[0058] Preferably, the molar ratio of the tetracarboxylic acid dianhydride monomer and the pyridine-containing triphenyldiamine monomer is 1:1.

[0059] Preferably, the catalyst is isoquinoline.

[0060] Preferably, the above method further includes dissolving polyimide in N,N-dimethylacetamide, centrifuging to degas, then coating it into a film and forming the film at high temperature in a vacuum oven.

[0061] More preferably, after the polyimide is dissolved in N,N-dimethylacetamide, the solid content of the polyimide is 15%, and the centrifugation parameters are 5000 r / min. -1 The vacuum oven heating times are 80℃ for 1 hour, 150℃ for 2 hours, 200℃ for 2 hours, and 220℃ for 2 hours, respectively.

[0062] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0063] 1. A series of novel colorless and transparent polyimides containing pyridine triphenyldiamine were successfully prepared, and the effect of adjusting the diamine structure on the performance of polyimide films was systematically investigated.

[0064] 2. Different diamine groups have different electron-withdrawing effects, which can help regulate charge transfer. At the same time, the methyl group at the para position of the nitrogen atom on the pyridine can further adjust the folding effect of the polyimide molecular chain, further regulate the mechanical properties of the polyimide material, and coordinate the thermal and optical properties.

[0065] 3. The prepared colorless and transparent polyimide has good optical transparency (82.6%~89.3%), bending resistance (20,000 bends), good heat resistance (290.2℃~342.6℃), and high tensile strength (85MPa~108MPa), and has potential application value in the field of flexible displays. Attached Figure Description

[0066] Figure 1 The hydrogen and carbon spectra of the pyridine-containing terphenyl dinitro monomer NM-1 prepared in Example 1 are shown.

[0067] Figure 2 The hydrogen and carbon spectra of the pyridine-containing triphenyldiamine monomer 2F-PTPDA prepared in Example 1 are shown.

[0068] Figure 3 The hydrogen and carbon spectra of the pyridine-containing terphenyl dinitro monomer NM-2 prepared in Example 2 are shown.

[0069] Figure 4 The hydrogen and carbon spectra of the pyridine-containing triphenyldiamine monomer 6F-PTPDA prepared in Example 2 are shown.

[0070] Figure 5 The hydrogen and carbon spectra of the pyridine-containing terphenyl dinitro monomer NM-3 prepared in Example 3 are shown.

[0071] Figure 6 The hydrogen and carbon spectra of the pyridine-containing triphenyldiamine monomer 6H-PTPDA prepared in Example 3 are shown.

[0072] Figure 7 The hydrogen and carbon spectra of the pyridine-containing terphenyl dinitro monomer NM-4 prepared in Example 4 are shown.

[0073] Figure 8 The hydrogen and carbon spectra of the pyridine-containing triphenyldiamine monomer 2F-MPTPDA prepared in Example 4 are shown.

[0074] Figure 9 The hydrogen and carbon spectra of the pyridine-containing terphenyl dinitro monomer NM-5 prepared in Example 5 are shown.

[0075] Figure 10 The hydrogen and carbon spectra of the pyridine-containing triphenyldiamine monomer 6F-MPTPDA prepared in Example 5 are shown.

[0076] Figure 11 The hydrogen and carbon spectra of the pyridine-containing terphenyl dinitro monomer NM-6 prepared in Example 6 are shown.

[0077] Figure 12 The hydrogen and carbon spectra of the pyridine-containing triphenyldiamine monomer 6H-MPTPDA prepared in Example 6 are shown.

[0078] Figure 13 The hydrogen spectrum of polyimides 6FDA-2F-PTPDA, 6FDA-6F-PTPDA, 6FDA-6H-PTPDA, 6FDA-2F-MPTPDA, 6FDA-6F-MPTPDA and 6FDA-6H-MPTPDA prepared in Examples 1, 2, 3, 4, 5 and 6. Detailed Implementation

[0079] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0080] Example 1

[0081] Synthesis of pyridine-containing terphenyldiamine 2F-PTPDA monomer:

[0082] Synthesis of 2-(2-fluoro-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane monomer M1: 1-bromo-2-fluoro-4-nitrobenzene (10 mmol), pinacol diboronate (12 mmol), potassium acetate (32.24 mmol), 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride (0.21 mmol), and 60 mL of 1,4-dioxane were placed in a three-necked flask and stirred under nitrogen atmosphere. The mixture was heated to 80 °C and refluxed for 24 h. After the reaction was completed, the mixture was cooled. The mixture was diluted with 50 mL of ethyl acetate and washed three times with 50 mL of deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography to obtain a pale yellow powder with a yield of 69%.

[0083] Synthesis of the pyridine-containing terphenyl dinitro monomer NM-1: Under nitrogen atmosphere, 6 mmol of M1, 2 mmol of 3,5-dibromopyridine, 27 mmol of potassium carbonate, 8 mL of deionized water, 0.3 mmol of tetra(triphenylphosphine)palladium, 4 mL of ethanol, and 8 mL of toluene were placed in a three-necked flask and subjected to three freeze-drying cycles to remove oxygen. The mixture was stirred and heated to 110 °C and refluxed for 24 h. After the reaction was completed at this temperature, the mixture was cooled. The mixture was diluted with 100 mL of dichloromethane and washed three times with 100 mL of deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product, which was finally purified by silica gel column chromatography in 76.8% yield.

[0084] Synthesis of pyridine-containing triphenyldiamine monomer 2F-PTPDA: 3g of NM-1, 60mL of anhydrous ethanol and 0.68g of Pd / C were added to a three-necked flask. Under nitrogen atmosphere, the mixture was stirred and heated to 80℃ for reflux. The temperature was maintained, and 6.32mL of hydrazine hydrate was added dropwise to the mixed solution in the three-necked flask using a constant pressure funnel (dropping rate was one drop every two seconds). After the addition was complete, the temperature was maintained for 12h. After the constant temperature reaction was completed, the heating was stopped, and the mixture was filtered while hot to remove Pd / C. The filtrate was poured into cold water, and sodium chloride was added while stirring until a solid precipitated. The solid was filtered out and washed with an ethanol / water mixture. The filtered solid was then vacuum dried to obtain pyridine-containing triphenyldiamine monomer 2F-PTPDA.

[0085] Synthesis of polyimide 6FDA-2F-PTPDA: Under a nitrogen atmosphere, 10 mmol of 2F-PTPDA and 10 mmol of 6FDA were placed in a three-necked flask, along with 32 mL of m-cresol and 8 mL of toluene. The mixture was heated to 80 °C and stirred at this temperature for 1 h. Then, 4 mL of isoquinoline was added, and the mixture was heated to 180 °C and stirred at this temperature for 10 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 100 mL of methanol to precipitate the solid. The solid was filtered out and washed with hot methanol. The filtered solid was then dried under vacuum to obtain 6FDA-2F-PTPDA.

[0086] High-temperature film formation by blade coating: Dissolve 1.2g of 6FDA-2F-PTPDA in 6.8g of DMAc, then centrifuge to degas (5000r min). -1 (5 min) Then coat the film and heat it in a vacuum oven at high temperature for 1 hour at 80℃, 2 hours at 150℃, 2 hours at 200℃ and 2 hours at 220℃.

[0087] Example 2

[0088] Synthesis of pyridine-containing terphenyldiamine 6F-PTPDA monomer:

[0089] Synthesis of 2-(2-trifluoromethyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane monomer M2: 10 mmol of 2-bromo-5-nitrotrifluorotoluene, 12 mmol of pinacol diborate, 32.24 mmol of potassium acetate, 0.21 mmol of 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride, and 60 mL of 1,4-dioxane were placed in a three-necked flask. The mixture was stirred and heated to 80 °C under nitrogen atmosphere and refluxed for 24 h. After the reaction was completed, the mixture was cooled. The mixture was diluted with ethyl acetate and washed three times with deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography to obtain a white powder with a yield of 73%.

[0090] Synthesis of the pyridine-containing terphenyl dinitro monomer NM-2: Under nitrogen atmosphere, 6 mmol of M2, 2 mmol of 3,5-dibromopyridine, 27 mmol of potassium carbonate, 8 mL of deionized water, 0.3 mmol of tetra(triphenylphosphine)palladium, 4 mL of ethanol, and 8 mL of toluene were placed in a three-necked flask and subjected to three freeze-drying evacuations to remove oxygen. The mixture was stirred and heated to 110 °C and refluxed for 24 h. After the reaction was completed at this temperature, the mixture was cooled. The mixture was diluted with 100 mL of dichloromethane and washed three times with 100 mL of deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product, which was then purified by silica gel column chromatography in 77.2% yield.

[0091] Synthesis of pyridine-containing triphenyldiamine monomer 6F-PTPDA: 3g of NM-2, 60mL of anhydrous ethanol and 0.68g of Pd / C were added to a three-necked flask. Under nitrogen atmosphere, the mixture was stirred and heated to 80℃ for reflux. The temperature was maintained, and 6.32mL of hydrazine hydrate was added dropwise to the mixed solution in the three-necked flask using a constant pressure funnel (dropping rate was one drop every two seconds). After the addition was complete, the temperature was maintained for 12h. After the constant temperature reaction was completed, the heating was stopped, and the mixture was filtered while hot to remove Pd / C. The filtrate was poured into cold water, and sodium chloride was added while stirring until a solid precipitated. The solid was filtered out and washed with an ethanol / water mixture. The filtered solid was then vacuum dried to obtain pyridine-containing triphenyldiamine monomer 6F-PTPDA.

[0092] Synthesis of polyimide 6FDA-6F-PTPDA: Under a nitrogen atmosphere, 10 mmol of 6F-PTPDA and 10 mmol of 6FDA were placed in a three-necked flask, along with 32 mL of m-cresol and 8 mL of toluene. The mixture was heated to 80 °C and stirred at this temperature for 1 h. Then, 4 mL of isoquinoline was added, and the mixture was heated to 180 °C and stirred at this temperature for 10 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 100 mL of methanol to precipitate the solid. The solid was filtered out and washed with hot methanol. The filtered solid was then dried under vacuum to obtain 6FDA-6F-PTPDA.

[0093] High-temperature film formation by blade coating: Dissolve 1.2g of 6FDA-2F-PTPDA in 6.8g of DMAc, then centrifuge to degas (5000r min). -1 (5 min) Then coat the film and heat it in a vacuum oven at high temperature for 1 hour at 80℃, 2 hours at 150℃, 2 hours at 200℃ and 2 hours at 220℃.

[0094] Example 3

[0095] Synthesis of pyridine-containing terphenyldiamine 6H-PTPDA monomer:

[0096] Synthesis of 2-(2-methyl-4-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane monomer M3: 10 mmol of 2-bromo-5-nitrotoluene, 12 mmol of pinacol diborate, 32.24 mmol of potassium acetate, 0.21 mmol of 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride, and 60 mL of 1,4-dioxane were placed in a three-necked flask. The mixture was stirred and heated to 80 °C under nitrogen atmosphere and refluxed for 24 h. After the reaction was completed, the mixture was cooled. The mixture was diluted with ethyl acetate and washed three times with deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography to obtain a pale yellow powder with a yield of 69%.

[0097] Synthesis of the pyridine-containing terphenyl dinitro monomer NM-3: Under nitrogen atmosphere, 6 mmol of M3, 2 mmol of 3,5-dibromopyridine, 27 mmol of potassium carbonate, 8 mL of deionized water, 0.3 mmol of tetra(triphenylphosphine)palladium, 4 mL of ethanol, and 8 mL of toluene were placed in a three-necked flask and subjected to three freeze-drying cycles to remove oxygen. The mixture was stirred and heated to 110 °C and refluxed for 24 h. After the reaction was completed at this temperature, the mixture was cooled. The mixture was diluted with 100 mL of dichloromethane and washed three times with 100 mL of deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product, which was then purified by silica gel column chromatography in 79.6% yield.

[0098] Synthesis of pyridine-containing triphenyldiamine monomer 6H-PTPDA: 3g of NM-3, 60mL of anhydrous ethanol and 0.68g of Pd / C were added to a three-necked flask. Under nitrogen atmosphere, the mixture was stirred and heated to 80℃ for reflux. The temperature was maintained, and 6.32mL of hydrazine hydrate was added dropwise to the mixed solution in the three-necked flask using a constant pressure funnel (dropping rate was one drop every two seconds). After the addition was complete, the temperature was maintained for 12h. After the constant temperature reaction was completed, the heating was stopped, and the mixture was filtered while hot to remove Pd / C. The filtrate was poured into cold water, and sodium chloride was added while stirring until a solid precipitated. The solid was filtered out and washed with an ethanol / water mixture. The filtered solid was then vacuum dried to obtain pyridine-containing triphenyldiamine monomer 6H-PTPDA.

[0099] Synthesis of polyimide 6FDA-6H-PTPDA: Under a nitrogen atmosphere, 10 mmol of 6H-PTPDA and 10 mmol of 6FDA were placed in a three-necked flask, along with 32 mL of m-cresol and 8 mL of toluene. The mixture was heated to 80 °C and stirred at this temperature for 1 h. Then, 4 mL of isoquinoline was added, and the mixture was heated to 180 °C and stirred at this temperature for 10 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 100 mL of methanol to precipitate the solid. The solid was filtered out and washed with hot methanol. The filtered solid was then dried under vacuum to obtain 6FDA-6H-PTPDA.

[0100] High-temperature film formation by blade coating: Dissolve 1.2g of 6FDA-6H-PTPDA in 6.8g of DMAc, then centrifuge to degas (5000r min). -1 (5 min) Then coat the film and heat it in a vacuum oven at high temperature for 1 hour at 80℃, 2 hours at 150℃, 2 hours at 200℃ and 2 hours at 220℃.

[0101] Example 4

[0102] Synthesis of pyridine-containing terphenyldiamine 2F-MPTPDA monomer:

[0103] Synthesis of the pyridine-containing terphenyl dinitro monomer NM-4: 6 mmol of M1, 2 mmol of 3,5-dibromo-4-methylpyridine, 27 mmol of potassium carbonate, 8 mL of deionized water, 0.3 mmol of tetra(triphenylphosphine)palladium, 4 mL of ethanol, and 8 mL of toluene were placed in a three-necked flask and subjected to three freeze-drying cycles to remove oxygen. The mixture was stirred and heated to 110°C and refluxed for 24 h. After the reaction was completed, the mixture was cooled. The mixture was diluted with 100 mL of dichloromethane and washed three times with 100 mL of deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography, with a yield of 53.0%.

[0104] Synthesis of pyridine-containing triphenyldiamine monomer 2F-MPTPDA: 3g of NM-4, 60mL of anhydrous ethanol and 0.68g of Pd / C were added to a three-necked flask. Under nitrogen atmosphere, the mixture was stirred and heated to 80℃ for reflux. The temperature was maintained, and 6.32mL of hydrazine hydrate was added dropwise to the mixed solution in the three-necked flask using a constant pressure funnel (dropping rate was one drop every two seconds). After the addition was complete, the temperature was maintained for 12h. After the constant temperature reaction was completed, heating was stopped, and Pd / C was removed by hot filtration. The filtrate was poured into cold water, and sodium chloride was added while stirring until a solid precipitated. The solid was filtered out and washed with an ethanol / water mixture. The filtered solid was then vacuum dried to obtain pyridine-containing triphenyldiamine monomer 2F-MPTPDA.

[0105] Synthesis of polyimide 6FDA-2F-MPTPDA: Under a nitrogen atmosphere, 10 mmol of 2F-MPTPDA and 10 mmol of 6FDA were placed in a three-necked flask, along with 32 mL of m-cresol and 8 mL of toluene. The mixture was heated to 80 °C and stirred at this temperature for 1 h. Then, 4 mL of isoquinoline was added, and the mixture was heated to 180 °C and stirred at this temperature for 10 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 100 mL of methanol to precipitate the solid. The solid was filtered out and washed with hot methanol. The filtered solid was then dried under vacuum to obtain 6FDA-2F-MPTPDA.

[0106] High-temperature film formation by blade coating: Dissolve 1.2g of 6FDA-2F-MPTPDA in 6.8g of DMAc, then centrifuge to degas (5000 rpm). -1 (5 min) Then coat the film and heat it in a vacuum oven at high temperature for 1 hour at 80℃, 2 hours at 150℃, 2 hours at 200℃ and 2 hours at 220℃.

[0107] Example 5

[0108] Synthesis of pyridine-containing terphenyldiamine 6F-MPTPDA monomer:

[0109] Synthesis of the pyridine-containing terphenyl dinitro monomer NM-5: 6 mmol of M2, 2 mmol of 3,5-dibromo-4-methylpyridine, 27 mmol of potassium carbonate, 8 mL of deionized water, 0.3 mmol of tetra(triphenylphosphine)palladium, 4 mL of ethanol, and 8 mL of toluene were placed in a three-necked flask and subjected to three freeze-drying cycles to remove oxygen. The mixture was stirred and heated to 110 °C and refluxed for 24 h. After the reaction was completed, the mixture was cooled. The mixture was diluted with 100 mL of dichloromethane and washed three times with 100 mL of deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography, with a yield of 52.1%.

[0110] Synthesis of pyridine-containing triphenyldiamine monomer 6F-MPTPDA: 3g of NM-5, 60mL of anhydrous ethanol and 0.68g of Pd / C were added to a three-necked flask. Under nitrogen atmosphere, the mixture was stirred and heated to 80℃ for reflux. The temperature was maintained, and 6.32mL of hydrazine hydrate was added dropwise to the mixed solution in the three-necked flask using a constant pressure funnel (dropping rate was one drop every two seconds). After the addition was complete, the temperature was maintained for 12h. After the constant temperature reaction was completed, the heating was stopped, and the mixture was filtered while hot to remove Pd / C. The filtrate was poured into cold water, and sodium chloride was added while stirring until a solid precipitated. The solid was filtered out and washed with an ethanol / water mixture. The filtered solid was then dried under vacuum to obtain pyridine-containing triphenyldiamine monomer 6F-MPTPDA.

[0111] Synthesis of polyimide 6FDA-6F-MPTPDA: Under a nitrogen atmosphere, 10 mmol of 6F-MPTPDA and 10 mmol of 6FDA were placed in a three-necked flask, along with 32 mL of m-cresol and 8 mL of toluene. The mixture was heated to 80 °C and stirred at this temperature for 1 h. Then, 4 mL of isoquinoline was added, and the mixture was heated to 180 °C and stirred at this temperature for 10 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 100 mL of methanol to precipitate the solid. The solid was filtered off and washed with hot methanol. The filtered solid was then dried under vacuum to obtain 6FDA-6F-MPTPDA.

[0112] High-temperature film formation by blade coating: Dissolve 1.2g of 6FDA-6F-MPTPDA in 6.8g of DMAc, then centrifuge to degas (5000 rpm). -1 (5 min) Then coat the film and heat it in a vacuum oven at high temperature for 1 hour at 80℃, 2 hours at 150℃, 2 hours at 200℃ and 2 hours at 220℃.

[0113] Example 6

[0114] Synthesis of pyridine-containing terphenyldiamine 6H-MPTPDA monomer:

[0115] Synthesis of the pyridine-containing terphenyldinitro monomer NM-6: 6 mmol of M3, 2 mmol of 3,5-dibromo-4-methylpyridine, 27 mmol of potassium carbonate, 8 mL of deionized water, 0.3 mmol of tetra(triphenylphosphine)palladium, 4 mL of ethanol, and 8 mL of toluene were placed in a three-necked flask and subjected to three freeze-drying cycles to remove oxygen. The mixture was stirred and heated to 110 °C and refluxed for 24 h. After the reaction was completed at this temperature, the mixture was cooled. The mixture was diluted with 100 mL of dichloromethane and washed three times with 100 mL of deionized water. The organic layer was dried over anhydrous magnesium sulfate, and then the anhydrous magnesium sulfate was removed by filtration. The filtrate was concentrated under vacuum to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography, with a yield of 65.4%.

[0116] Synthesis of pyridine-containing triphenyldiamine monomer 6H-MPTPDA: 3g of NM-6, 60mL of anhydrous ethanol and 0.68g of Pd / C were added to a three-necked flask. Under nitrogen atmosphere, the mixture was stirred and heated to 80℃ for reflux. The temperature was maintained, and 6.32mL of hydrazine hydrate was added dropwise to the mixed solution in the three-necked flask using a constant pressure funnel (dropping rate was one drop every two seconds). After the addition was complete, the temperature was maintained for 12h. After the constant temperature reaction was completed, the heating was stopped, and the mixture was filtered while hot to remove Pd / C. The filtrate was poured into cold water, and sodium chloride was added while stirring until a solid precipitated. The solid was filtered out and washed with an ethanol / water mixture. The filtered solid was then dried under vacuum to obtain pyridine-containing triphenyldiamine monomer 6H-MPTPDA.

[0117] Synthesis of polyimide 6FDA-6H-MPTPDA: Under a nitrogen atmosphere, 10 mmol of 6H-MPTPDA and 10 mmol of 6FDA were placed in a three-necked flask, along with 32 mL of m-cresol and 8 mL of toluene. The mixture was heated to 80 °C and stirred at this temperature for 1 h. Then, 4 mL of isoquinoline was added, and the mixture was heated to 180 °C and stirred at this temperature for 10 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 100 mL of methanol to precipitate the solid. The solid was filtered off and washed with hot methanol. The filtered solid was then dried under vacuum to obtain 6FDA-6H-MPTPDA.

[0118] High-temperature film formation by blade coating: Dissolve 1.2g of 6FDA-6H-MPTPDA in 6.8g of DMAc, then centrifuge to degas (5000r min). -1 (5 min) Then coat the film and heat it in a vacuum oven at high temperature for 1 hour at 80℃, 2 hours at 150℃, 2 hours at 200℃ and 2 hours at 220℃.

[0119] Table 1 Performance tests of polyimide films prepared in Examples 1-6 after high-temperature blade coating

[0120]

[0121] Table 1 shows the test method for the linear thermal expansion coefficient: using a thermomechanical analyzer, 5℃ min. -1 Test at 50–200℃;

[0122] Glass transition temperature: 5℃ min using a dynamic thermomechanical analyzer. -1 Tested at 1Hz, 30~400℃;

[0123] Optical transmittance: measured using an ultraviolet spectrophotometer;

[0124] Tensile strength: Tested in accordance with the requirements of GB / T 13542.6-2006 standard.

[0125] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A polyimide, characterized in that, It includes the following repeating units: Wherein, R1 is fluorine, trifluoromethyl or methyl, R2 is hydrogen or methyl, and n is 43 to 77.

2. The method for preparing the polyimide according to claim 1, characterized in that, The process includes the following steps: placing the pyridine-containing triphenyldiamine monomer, tetracarboxylic acid dianhydride monomer and m-cresol as described in formula (1) into a reaction vessel, heating to 60-80°C, stirring at a constant temperature for 0.5-1 h, adding a catalyst, and then heating to 180-185°C and stirring at a constant temperature for 8-10 h to obtain the polyimide; The structural formula of the tetracarboxylic acid dianhydride monomer is as follows: The pyridine-containing triphenyldiamine monomer has the following structural formula: In the formula, R1 is trifluoromethyl, methyl or fluorine; R2 is hydrogen or methyl.

3. The preparation method according to claim 2, characterized in that, The pyridine-containing triphenyldiamine of formula (1) is prepared by the following steps: S1. A bromine-substituted 4-nitrobenzene compound, pinacol diborate, potassium acetate, 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride, and 1,4-dioxane were placed in a reaction vessel, stirred and heated to 80-90°C under inert gas conditions, and refluxed for 21-24 hours to obtain monomer M. S2. Monomer M, dibromo-substituted pyridine compound, potassium carbonate, water, tetra(triphenylphosphine)palladium, ethanol and toluene are placed in a reaction vessel, stirred and heated to 100-120°C under inert gas conditions, and refluxed for 20.5-24 hours to obtain pyridine-containing triphenyl dinitro monomer. S3. At room temperature, pyridine-containing terphenyl dinitro monomer, anhydrous ethanol and Pd / C are added to a reaction vessel. Under inert gas conditions, the mixture is stirred and heated to 80°C for reflux. Hydrazine hydrate is added dropwise to the mixed solution in the reaction vessel. After the addition is complete, the reaction is maintained at 80°C for 10-12 hours to obtain the pyridine-containing terphenyl diamine.

4. The preparation method according to claim 2, characterized in that, The bromine-substituted 4-nitrobenzene compound in step S1 is 1-bromo-2-fluoro-4-nitrobenzene, 2-bromo-5-nitrotoluene, or 2-bromo-5-nitrotrifluorotoluene; the dibromine-substituted pyridine compound in step S2 is 3,5-dibromopyridine or 3,5-dibromo-4-methylpyridine.

5. The preparation method according to claim 2, characterized in that, In step S1, the molar ratio of the bromine-substituted 4-nitrobenzene compound, pinacol diboronate, potassium acetate, and 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride is 10 mmol:12 mmol:32.24 mmol:0.21 mmol.

6. The preparation method according to claim 2, characterized in that, In step S2, the molar ratio of monomer M, bromosubstituted pyridine compound, potassium carbonate and tetra(triphenylphosphine)palladium is 3:1:13.5:0.

15.

7. The preparation method according to claim 2, characterized in that, In step S3, the ratio of the pyridine-containing terphenyldinitro monomer, Pd / C, and anhydrous ethanol is 3g:0.68g:60mL; the ratio of the pyridine-containing terphenyldinitro monomer to hydrazine hydrate is 3g:6.32mL. In step S3, the hydrazine hydrate is added at a rate of one drop every two seconds.

8. The preparation method according to claim 2, characterized in that, The molar ratio of the tetracarboxylic acid dianhydride monomer and the pyridine-containing triphenyldiamine monomer is 1:1; The catalyst is isoquinoline.

9. The application of the polyimide of claim 1 in the field of flexible electronics.

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