Dipyrrolyl diamine and preparation method and application of polyimide prepared from dipyrrolyl diamine

Abstract

The invention discloses a preparation method and application of pyrrolopyrrole diamine and polyimide prepared from the pyrrolopyrrole diamine, a pyrrolopyrrole structure is introduced into a diamine monomer, and the pyrrolopyrrole structure reacts with specific tetracarboxy dianhydride to construct a polyimide molecule with strong electron donating characteristics of conjugated chromophores and planar rigidity. The optical and electrical properties of polyimide are improved from the molecular level while good thermal performance is maintained, and the fluorescence property of the material is further enhanced; the polyimide serving as a film material has a good application prospect in the fields of serving as a light-emitting layer of an OLED (Organic Light Emitting Diode) device or serving as a fluorescent identification layer and the like.

Description

Technical Field

[0001] This invention relates to the field of polyimide synthesis technology, and particularly to a pyrrole-based diamine, the preparation method of the polyimide therefrom, and its applications. Background Technology

[0002] In recent years, luminescent polymer materials with high photoluminescence quantum yields have been successfully applied in polymer light-emitting diodes (PLEDs), optical wavelength converters, plastic lasers, and fluorescent sensors. This is due to their additional advantages over small organic molecule luminescent materials, such as flexible structure, low cost, and ease of film formation. Currently reported luminescent polymer materials include polyacetylene, polythiophene, polyaniline, polyamide amine, and polyurethane. However, these luminescent polymer materials suffer from drawbacks such as complex polymerization and purification processes, poor thermal and dimensional stability, and weak mechanical strength of nanoscale films, limiting their in-depth application in modern optics and microelectronics technologies.

[0003] Polyimides are a class of high-performance polymers containing imide rings in their main chain, exhibiting excellent thermal and dimensional stability, as well as good mechanical properties. They have been widely used in aerospace, microelectronics and photonic devices, gas separation technology, and other fields. Fluorescent polyimides, as an important functional polymer material, have shown great application potential in optical anti-counterfeiting, optoelectronic displays, and sensors. In OLED applications, PI materials with excellent thermal stability are mainly used as transport layers, device substrates, or emissive layers for doped luminescent materials. Only a few cases have been reported of fluorescent PI being directly used as emissive layers in OLED devices. This is because traditional aromatic PI materials inevitably experience fluorescence quenching due to strong intermolecular and intramolecular charge transfer interactions and the lowest excited state (CT state), resulting in inefficient fluorescence or even no fluorescence. If a PI material possesses both excellent thermal stability and high fluorescence quantum efficiency, it is very suitable for use as an emissive layer in OLED devices. Therefore, developing fluorescent PI materials with high fluorescence quantum efficiency is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a pyrrolidinyl diamine and its preparation method that solve the above-mentioned technical problems and can enhance the fluorescence properties of polyimide materials.

[0005] Another object of the present invention is to provide a polyimide prepared using the above-mentioned pyrrolidone diamine and a method thereof.

[0006] Another object of the present invention is to provide the above-mentioned polyimide film and its application.

[0007] Therefore, the technical solution of the present invention is as follows:

[0008] A pyrrole diamine has the following chemical structural formula:

[0009]

[0010] The chemical structural formula of the R group is as follows:

[0011] This pyrrolodiamine synthesizes a diamine monomer with a planar rigid nitrogen-containing heterocyclic fluorophore by introducing a pyrrolopyrrole structure into the diamine monomer to form a strong electron-donating property of the conjugated chromophore. Then, by reacting it with a specific tetracarboxylic dianhydride and appropriately controlling the intramolecular CT effect between the diamine and dianhydride moieties, a fluorescent polymer with fluorescent properties is constructed, thereby improving the optical and electrical properties of polyimide at the molecular level and enhancing the fluorescence performance of polyimide materials.

[0012] A method for preparing pyrrolodiamine, the specific steps of which are as follows:

[0013] (1) Dissolve p-nitrobenzaldehyde and 3,4-dimethoxyaniline, or p-nitrobenzaldehyde and 3,4,5-trimethoxyaniline in organic solvent I, and react at 40℃-60℃ for 2h-4h to prepare an intermediate; specifically, the intermediate is N-(3,4-dimethoxyphenyl)-1-(4-nitrophenyl)methylimine, or N-(3,4,5-trimethoxyphenyl)-1-(4-nitrophenyl)methylimine;

[0014] (2) Dissolve the intermediate and catalyst p-methylbenzenesulfonic acid in organic solvent II, then add 2,3-butanedione, and react at 85℃-95℃ for 3h-5h under nitrogen protection to prepare the nitro compound product; specifically, the nitro compound product is 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole or 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole;

[0015] (3) Dissolve the nitro compound and the metal carbon catalyst in organic solvent III, add a reducing agent, and react at 50℃-80℃ for 3h-5h to prepare the diamine monomer.

[0016] Preferably, in step (1), the molar ratio of p-nitrobenzaldehyde to 3,4-dimethoxyaniline, or p-nitrobenzaldehyde to 3,4,5-trimethoxyaniline, is 1:(1 to 1.1).

[0017] Preferably, in step (1), organic solvent I is methanol, ethanol or N,N-dimethylformamide, more preferably ethanol; the amount of organic solvent I added is 10 to 20 times the total weight of the two monomers.

[0018] Preferably, in step (2), the molar ratio of the intermediate to 2,3-butanedione is (1.6–2):1, more preferably 2:1. In other embodiments of the present invention, when the molar amount of 2,3-butanedione exceeds the above reaction, significant side reactions occur, resulting in a significant decrease in the yield of the nitro compound.

[0019] Preferably, in step (2), the molar ratio of the intermediate to p-toluenesulfonic acid is 1:(0.05-0.3), more preferably 1:(0.08-0.1).

[0020] Preferably, in step (2), the organic solvent II is glacial acetic acid, and the amount added is 4 to 8 times the total weight of the intermediate and 2,3-butanedione.

[0021] Preferably, in step (3), the metal carbon catalyst is a palladium-carbon catalyst, a nickel-carbon catalyst, or a platinum-carbon catalyst, preferably a palladium-carbon catalyst, such as, but not limited to, 10% Pd / C or 15% Pd / C.

[0022] Preferably, in step (3), the weight ratio of the nitro compound to the metal carbon catalyst is 1:(0.05 to 0.2), more preferably 1:(0.1 to 0.15).

[0023] Preferably, in step (3), the reducing agent is hydrogen, hydrazine hydrate, formic acid, ammonium formate, or sodium formate, more preferably hydrogen. In some other embodiments of this example, if the reduction reaction time of the nitro compound exceeds the upper limit of the above range, significant side reactions will occur, seriously affecting the purity of the reduction product.

[0024] Preferably, in step (3), organic solvent III is methanol, ethanol or N,N-dimethylformamide, more preferably N,N-dimethylformamide; the amount of organic solvent III added is 25 to 120 times the weight of the nitro compound product.

[0025] A polyimide prepared using the above-mentioned pyrrolodiamine is obtained by polymerization of pyrrolodiamine and tetracarboxylic dianhydride; wherein the tetracarboxylic dianhydride is 4,4'-(hexafluoroisopropene) phthalic anhydride, 4,4'-oxophthalic anhydride or bisphenol A type diether dianhydride.

[0026] The chemical structural formula of 4,4'-(hexafluoroisopropene)phthalic anhydride is:

[0027]

[0028] The chemical structural formula of 4,4'-oxophthalic anhydride is:

[0029]

[0030] The chemical structural formula of bisphenol A type diether dianhydride is:

[0031]

[0032] Taking 4,4'-(hexafluoroisopropylidene)phthalic anhydride as an example, the chemical structural formula of the polyimide prepared from the two pyrrole diamines is as follows:

[0033]

[0034] The preparation method of the polyimide described in this invention is not particularly limited. A known method can be used to obtain the polyimide precursor—polyamic acid—and then imidization can be completed by thermal imidization or chemical imidization to obtain the polyimide. Preferably, this invention uses the thermal imidization method, and the specific preparation steps are as follows:

[0035] S1. Tetracarboxylic acid dianhydride is added in batches to organic solvent IV containing pyrrolodiamine and stirred for 18-24 hours to prepare a polyamic acid solution.

[0036] In step S1, the molar ratio of the diamine monomer to the tetracarboxylic acid dianhydride is 1:(1 to 1.02).

[0037] In step S1, the solid content of the polyamic acid solution is 20wt% to 35wt%. In some other embodiments of the present invention, if the solid content of the polyamic acid solution is too low, the film shrinkage occurs during the drying solvent step before thermal imidization, and film formation cannot continue.

[0038] In step S1, the organic solvent IV is dimethylformamide, dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide, preferably dimethyl sulfoxide; wherein, the amount of organic solvent IV added is 3.5 mL to 6.5 mL of organic solvent IV per 1 mol of diamine monomer.

[0039] S2. After degassing, the polyamic acid solution is coated into a film. After drying to remove the solvent, a thermal imidization method is performed to prepare a polyimide film.

[0040] The degassing step S2 is as follows: at room temperature, the polyamic acid solution is placed in a vacuum environment for 30 min to 90 min.

[0041] The coating step S2 is as follows: pour the polyamic acid solution onto a clean and dry glass substrate, and use a spiral fine-tuning coating tool in conjunction with an automatic coating machine to coat a polyamic acid film of controllable thickness; the film thickness is 30μm to 50μm.

[0042] The drying step S2 is as follows: drying at a temperature of 60℃~100℃ for 1h~5h to remove most of the solvent; preferably drying at 60℃~80℃ for 2h~3h.

[0043] The thermal imidization step S2 is as follows: the temperature is increased from room temperature to 250°C at a rate of 1°C / min to 2°C / min under a nitrogen atmosphere, and then maintained at 100°C, 200°C and 250°C for 40 to 60 minutes respectively. After that, it is naturally cooled to room temperature to obtain a polyimide film.

[0044] One application of the above-mentioned polyimide film is as a light-emitting layer on an OLED device, or as a fluorescent marking layer.

[0045] Compared with the prior art, the present invention introduces the structure of pyrrolopyrrole into the diamine monomer and reacts it with a specific tetracarboxylic dianhydride to construct a polyimide molecule with strong electron-donating properties of conjugated chromophores and planar rigidity. This achieves the improvement of the optical and electrical properties of polyimide at the molecular level while maintaining good thermal properties, and further enhances the fluorescence properties of the material. Attached Figure Description

[0046] Figure 1 The 1H NMR spectrum of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole in Example 1 of this invention is shown.

[0047] Figure 2 The 1H NMR spectrum of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole in Example 1 of this invention is shown.

[0048] Figure 3 This is the 1H NMR spectrum of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole in Example 5 of the present invention;

[0049] Figure 4 This is the 1H NMR spectrum of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole in Example 5 of the present invention.

[0050] Figure 5 Differential scanning calorimetry (DSC) curves of the polyimide films prepared in Examples 7 to 12 of this invention;

[0051] Figure 6 Thermogravimetric curves of the polyimide films prepared in Examples 7 to 12 of this invention are shown.

[0052] Figure 7The fluorescence emission curves of the polyimide films prepared in Examples 7 to 12 of this invention are shown.

[0053] Figure 8 This is a characterization diagram of the electrochemical behavior of the polyimide film prepared in Example 8 of this invention. Detailed Implementation

[0054] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention.

[0055] Example 1

[0056] 6.04 g (40 mmol) of p-nitrobenzaldehyde and 6.13 g (40 mmol) of 3,4-dimethoxyaniline were dissolved in 175 mL of ethanol and reacted at 50 °C for 4 h. The reaction was monitored by TLC until it ended. The mixture was allowed to cool naturally to room temperature and then filtered to obtain an intermediate product. 5.72 g (20 mmol) of the intermediate product was dissolved in 40 mL of glacial acetic acid and 0.3 g (1.6 mmol) of p-toluenesulfonic acid was added. The mixture was heated to 85 °C under a nitrogen atmosphere, and 0.86 g (10 mmol) of 2,3-butanedione was added dropwise. The mixture was then heated to 95 °C and reacted for another 4 h. The mixture was allowed to cool naturally to room temperature to precipitate a solid. The solid was filtered, washed 2-3 times with glacial acetic acid, and then slurried twice with ethyl acetate to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0057] At room temperature, 3 g (4.8 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole and 0.3 g of 10% Pd / C were dispersed in 90 mL of N,N-dimethylformamide, hydrogen gas was introduced, and a reduction reaction was carried out at 50 °C for 3 h. The reaction product was filtered, water was added to precipitate, and the mixture was stirred twice with dichloromethane at a higher temperature to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0058] Example 2

[0059] 6.04 g (40 mmol) of p-nitrobenzaldehyde and 6.43 g (42 mmol) of 3,4-dimethoxyaniline were dissolved in 175 mL of ethanol and reacted at 50 °C for 4 h. The reaction was monitored by TLC until it ended. After cooling to room temperature, the intermediate product was obtained by filtration. 5.72 g (20 mmol) of the intermediate product was dissolved in 40 mL of glacial acetic acid, and 0.38 g (2 mmol) of p-toluenesulfonic acid was added. Under a nitrogen atmosphere, the temperature was raised to 85 °C, and 0.86 g (10 mmol) of 2,3-butanedione was added dropwise. The temperature was raised to 95 °C and the reaction was continued for 4 h. After cooling to room temperature, a solid precipitated. The solid was filtered, washed 2-3 times with glacial acetic acid, and then slurried twice with ethyl acetate to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0060] At room temperature, 3 g (4.8 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole and 0.3 g of 10% Pd / C were dispersed in 120 mL of N,N-dimethylformamide, hydrogen gas was introduced, and a reduction reaction was carried out at 50 °C for 3 h. The reaction product was filtered, water was added to precipitate, and the mixture was stirred twice with dichloromethane at a higher temperature to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0061] Example 3

[0062] 6.04 g (40 mmol) of p-nitrobenzaldehyde and 6.43 g (42 mmol) of 3,4-dimethoxyaniline were dissolved in 175 mL of ethanol and reacted at 50 °C for 4 h. The reaction was monitored by TLC until it ended. The mixture was allowed to cool naturally to room temperature and filtered to obtain an intermediate product. 5.72 g (20 mmol) of the intermediate product was dissolved in 40 mL of glacial acetic acid and 0.38 g (2 mmol) of p-toluenesulfonic acid was added. The mixture was heated to 85 °C under a nitrogen atmosphere, and 1.03 g (12 mmol) of 2,3-butanedione was added dropwise. The mixture was then heated to 95 °C and reacted for another 4 h. The mixture was allowed to cool naturally to room temperature to precipitate a solid. The solid was filtered and washed 2-3 times with glacial acetic acid and then slurried twice with ethyl acetate to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0063] At room temperature, 3 g (4.8 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole and 0.3 g of 10% Pd / C were dispersed in 120 mL of N,N-dimethylformamide, hydrogen gas was introduced, and a reduction reaction was carried out at 80 °C for 4 h. The reaction product was filtered, water was added to precipitate, and the mixture was stirred twice with dichloromethane at a higher temperature to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0064] Example 4

[0065] 6.04 g (40 mmol) of p-nitrobenzaldehyde and 6.43 g (42 mmol) of 3,4-dimethoxyaniline were dissolved in 175 mL of ethanol and reacted at 50 °C for 4 h. The reaction was monitored by TLC until it ended. After cooling to room temperature, the intermediate product was obtained by filtration. 5.72 g (20 mmol) of the intermediate product was dissolved in 40 mL of glacial acetic acid, and 0.38 g (2 mmol) of p-toluenesulfonic acid was added. Under a nitrogen atmosphere, the temperature was raised to 85 °C, and 0.86 g (10 mmol) of 2,3-butanedione was added dropwise. The temperature was raised to 95 °C and the reaction was continued for 4 h. After cooling to room temperature, a solid precipitated. The solid was filtered, washed 2-3 times with glacial acetic acid, and then slurried twice with ethyl acetate to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0066] At room temperature, 3 g (4.8 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole and 0.45 g of 15% Pd / C were dispersed in 120 mL of N,N-dimethylformamide, hydrogen gas was introduced, and a reduction reaction was carried out at 50 °C for 4 h. The reaction product was filtered, water was added to precipitate, and the mixture was stirred twice with dichloromethane at a higher temperature to obtain 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0067] Example 5

[0068] 6.04 g (40 mmol) of p-nitrobenzaldehyde and 8.06 g (44 mmol) of 3,4,5-trimethoxyaniline were dissolved in 280 mL of ethanol and reacted at 50 °C for 4 h. The reaction was monitored by TLC until it ended. After cooling to room temperature, the intermediate product was obtained by filtration. 6.32 g (20 mmol) of the intermediate product was dissolved in 40 mL of glacial acetic acid, and 0.3 g (1.6 mmol) of p-toluenesulfonic acid was added. Under a nitrogen atmosphere, the temperature was raised to 85 °C, and 0.86 g (10 mmol) of 2,3-butanedione was added dropwise. The temperature was raised to 95 °C and the reaction was continued for 4 h. After cooling to room temperature, a solid precipitated. The solid was filtered, washed 2-3 times with glacial acetic acid, and then slurried twice with ethyl acetate to obtain 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0069] At room temperature, 2 g (2.9 mmol) of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole and 0.2 g of 10% Pd / C were dispersed in 250 mL of N,N-dimethylformamide, hydrogen gas was introduced, and a reduction reaction was carried out at 50 °C for 4 h. The reaction product was filtered, water was added to precipitate, and the mixture was stirred twice with dichloromethane at a higher temperature to obtain 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0070] Example 6

[0071] 6.04 g (40 mmol) of p-nitrobenzaldehyde and 8.06 g (44 mmol) of 3,4,5-trimethoxyaniline were dissolved in 280 mL of ethanol and reacted at 50 °C for 4 h. The reaction was monitored by TLC until it ended. After cooling to room temperature, the product was filtered to obtain an intermediate. 6.32 g (20 mmol) of the intermediate was dissolved in 40 mL of glacial acetic acid and 0.38 g (2 mmol) of p-methanesulfonic acid catalyst was added. Under a nitrogen atmosphere, the temperature was raised to 85 °C and 0.86 g (10 mmol) of 2,3-butanedione was added dropwise. The temperature was raised to 95 °C and the reaction was continued for 4 h. After cooling to room temperature, a solid precipitated. The solid was filtered and washed 2-3 times with glacial acetic acid and then slurried twice with ethyl acetate to obtain 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0072] At room temperature, 2 g (2.9 mmol) of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole and 0.3 g of 15% Pd / C were dispersed in 250 mL of N,N-dimethylformamide, and hydrogen gas was introduced. The reaction was carried out at 60 °C for 4 h. The reaction product was filtered, water was added to precipitate the product, and the mixture was stirred twice with dichloromethane at a higher temperature to obtain 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole.

[0073] Example 7

[0074] In a nitrogen atmosphere, 0.56 g (1 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.45 g (1.02 mmol) of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in three portions, with 2 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 22 wt% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0075] The thermal amidation step is as follows: the temperature is increased from room temperature to 250°C at a rate of 1°C / min to 2°C / min under a nitrogen atmosphere, and then maintained at 100°C, 200°C and 250°C for 60 min each, and then naturally cooled to room temperature; the thermal amidation steps of Examples 8-12, as well as Comparative Examples 1, 2 and 3 are the same.

[0076] Example 8

[0077] In a nitrogen atmosphere, 0.56 g (1 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.316 g (1.02 mmol) of 4,4'-oxophthalic anhydride was added in three portions, with 1.7 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 35 wt% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0078] Example 9

[0079] In a nitrogen atmosphere, 0.56 g (1 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.53 g (1.02 mmol) of bisphenol A diether dianhydride was added in three portions, with 2.2 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 34 wt% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0080] Example 10

[0081] In a nitrogen atmosphere, 0.62 g (1 mmol) of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 5 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.53 g (1.02 mmol) of bisphenol A type diether dianhydride was added in three portions, with 3.4 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 26.5 wt% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0082] Example 11

[0083] In a nitrogen atmosphere, 0.62 g (1 mmol) of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 5 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.316 g (1.02 mmol) of 4,4'-oxophthalic anhydride was added in three portions, with 4.2 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 22% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0084] Example 12

[0085] In a nitrogen atmosphere, 0.62 g (1 mmol) of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 5 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.45 g (1.02 mmol) of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in three portions, with 3.4 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 25.2% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0086] Comparative Example 1

[0087] In a nitrogen atmosphere, 0.56 g (1 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.3 g (1.02 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added in three portions, with 2.14 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 30% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0088] The polyimide film exhibited significant cracks and poor film-forming properties after thermal imidization. The reason for this is that in Comparative Example 1, the carboxylic dianhydride used was 3,3',4,4'-biphenyltetracarboxylic dianhydride, which has a rigid planar structure. Its polymerization with pyrrolidinyl diamine, which itself has a certain degree of rigidity, resulted in excessively rigid polyimide molecular chains, making the film brittle and prone to cracking defects, thus preventing film formation.

[0089] Comparative Example 2

[0090] In a nitrogen atmosphere, 0.56 g (1 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.22 g (1.02 mmol) of pyromellitic dianhydride was added in three portions, with 1.66 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 30% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0091] The polyimide film cracked after thermal imidization, resulting in poor film-forming properties. The reason for this is that in Comparative Example 2, the carboxylic dianhydride used was pyromellitic dianhydride, which has a more rigid structure. When it polymerized with pyrrolidinyl diamine, which itself has a certain degree of rigidity, the molecular chain of the polyimide became too rigid, resulting in a brittle film that cracked directly after thermal imidization and could not form a film.

[0092] Comparative Example 3

[0093] In a nitrogen atmosphere, 0.56 g (1 mmol) of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1 was dissolved in 2 mL of DMAc. After heating to 50 °C, 0.45 g (1.02 mmol) of 4,4'-(hexafluoroisopropene)phthalic anhydride was added in three portions, with 2 mL of DMAc added during the process. The mixture was stirred thoroughly after each addition. After the addition was complete, the reaction was continued for 18 h to obtain a polyamic acid solution. The polyamic acid solution with a solid content of 22% was placed in a negative pressure environment for 30 min to remove air bubbles. The solution was then poured onto a clean and dry glass substrate, and a polyamic acid wet film with a thickness of about 30 μm was formed by scraping with a spiral fine-tuning coating tool in conjunction with an automatic coating machine. The polyamic acid wet film was first dried at 80 °C for 4 h to remove the solvent, and then subjected to thermal amidation to obtain a polyimide film.

[0094] After thermal imidization, the polyimide film cracked, resulting in poor film-forming properties. The reason for this failure to form a film is that, in Comparative Example 4, the thermal imidization temperature was too high, causing the film to crack and preventing film formation.

[0095] Performance testing:

[0096] (I) Chemical structural characterization of diamine monomers:

[0097] The following are the synthetic routes for 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1 and 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 6:

[0098]

[0099] The intermediates and diamine monomers prepared in Examples 1 and 6 were characterized by proton NMR spectra.

[0100] like Figure 1 The image shown is the 1H NMR spectrum of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1. Figure 2 The image shows the 1H NMR spectrum of 1,4-bis(3,4-dimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 1. These two 1H NMR spectra confirm the preparation results and... Figure 1 The synthetic routes shown are consistent.

[0101] like Figure 3 The image shown is the 1H NMR spectrum of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-nitrophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 6. Figure 4 The figures shown are the 1H NMR spectra of 1,4-bis(3,4,5-trimethoxyphenyl)-2,5-bis(4-aminophenyl)-1,4-dihydropyrrole[3,2-b]pyrrole prepared in Example 6. These two 1H NMR spectra confirm the preparation results and... Figure 1 The synthetic routes shown are consistent.

[0102] (II) Thermogravimetric analysis and differential scanning calorimetry of polyimide films:

[0103] Differential scanning calorimetry was used to determine the glass transition temperature (Tg) of the polyimide films prepared in Examples 7–12. g The test was conducted under the following conditions: sample mass 5 mg–10 mg, nitrogen atmosphere, nitrogen flow rate 50 mL / min, temperature increased from room temperature to 400 °C at a rate of 20 °C / min, held for 5 min, then cooled to 40 °C, and then increased again to 400 °C at a rate of 10 °C / min, with a nitrogen flow rate of 50 mL / min. The T value of the polymer was measured based on the second temperature curve. g The test results are as follows Figure 5 As shown in Table 1.

[0104] Table 1:

[0105]

[0106]

[0107] The thermal decomposition temperatures of the polyimide films prepared in Examples 7 to 12 were tested using a thermogravimetric analyzer. The experimental conditions were as follows: the temperature was increased from 40°C to 800°C at a rate of 10°C / min under a nitrogen atmosphere. The mass of the sample was 5 mg. The temperatures at which thermal weight loss of 5% and 10% occurred were recorded as T. d5％ and T d10％ The test results are as follows Figure 6 As shown in Table 2.

[0108] Table 2:

[0109]

[0110] Combined Table 1 and Figure 5 and Table 2 and Figure 6 It can be seen that the polyimide films prepared in Examples 7 to 12 exhibited excellent thermal properties in the test. The glass transition temperature of the polyimide films was 230°C to 290°C, the temperature at which 5% of thermal weight loss occurred was 370°C to 420°C, the temperature at which 10% of thermal weight loss occurred was 400°C to 450°C, and the residual mass percentage at 800°C was 50% to 60%.

[0111] The above test results demonstrate that the polyimide prepared based on the pyrrole diamine of this invention has a highly conjugated and planar rigid structure in its imide ring, which further restricts chain segment movement. Furthermore, the planarity of the imide ring promotes π-π stacking, resulting in a more compact molecular chain arrangement, reduced free volume, and increased glass transition temperature (Tg). Regarding the choice of anhydride, the presence of ether bonds in bisphenol A type diether dianhydrides weakens the rigidity of the molecular chain due to the flexible chain segments, leading to a decrease in Tg. When the anhydride is the same but the diamine is different, the polyimide film synthesized from a diamine monomer with three methoxy groups exhibits lower thermal properties. This is because the three methoxy groups are symmetrically distributed on both sides of the molecular chain, and the methoxy groups, as flexible groups, increase the flexibility of the molecular chain. Simultaneously, as the number of methoxy groups increases, the inter-chain stacking becomes looser, resulting in a larger free volume, thus weakening the thermal properties of the polymer film.

[0112] (III) Optical performance testing:

[0113] The emission spectrum of the polyimide film was measured using a fluorescence spectrophotometer, and the test results are as follows: Figure 7As shown in the figure, the polyimide films prepared in Examples 7 to 12 all exhibit significant fluorescence effects. Specifically, when the acid anhydride is the same but the diamine is different, the polyimide film synthesized from a diamine monomer with three methoxy groups exhibits a relatively weaker fluorescence effect. This is because with the increase of methoxy groups, the electron-withdrawing ability of the methoxy groups accelerates intramolecular charge transfer, causing more energy to be released non-radiatively during the molecule's return to the ground state after excitation. Simultaneously, the increase in methoxy groups weakens the molecular rigidity and increases the molecular degrees of freedom, thus weakening the fluorescence performance of the polyimide film. Conversely, when the diamine is the same but the acid anhydride is different, the difference in fluorescence performance between the two synthesized polyimide films is small, but the stronger the molecular rigidity of the acid anhydride, the higher the fluorescence performance.

[0114] (iv) Electrical performance testing:

[0115] Taking the polyimide film prepared in Example 8 as an example, the electrochemical behavior of the film was characterized by cyclic voltammetry, such as... Figure 8 As shown in the figure, the polyimide film exhibits obvious redox peaks. This is because the pyrrolopyrrole structure at the center of the polyimide molecule is an electron-rich planar conjugated structure. The delocalization of π electrons forms molecular orbitals, reducing the energy difference between orbitals, making the electrochemical signal more obvious, and effectively improving the electrochemical properties of the material.

[0116] In summary, this invention prepares pyrrolodiamine by introducing a pyrrolopyrrole structure into a diamine monomer, and then reacts the pyrrolodiamine with a specific tetracarboxylic dianhydride, followed by amidation, to prepare a polyimide with good thermal, fluorescent, and electrochemical properties. It has good application prospects as a film material in fields such as the light-emitting layer of OLED devices or the fluorescent marking layer.

Claims

1. A pyrrolidone diamine, characterized in that, Its chemical structural formula is: In the formula, the R basis is:

2. A method for preparing pyrrolidone diamine as described in claim 1, characterized in that, The preparation steps are as follows: (1) Dissolve p-nitrobenzaldehyde and 3,4-dimethoxyaniline, or p-nitrobenzaldehyde and 3,4,5-trimethoxyaniline in organic solvent I and react at 40℃-60℃ for 2h-4h to prepare an intermediate; (2) Dissolve the intermediate and catalyst p-toluenesulfonic acid in organic solvent II, then add 2,3-butanedione, and react at 85℃-95℃ for 3h-5h under nitrogen protection to prepare the nitro compound product. (3) Dissolve the nitro compound and the metal carbon catalyst in organic solvent III, add a reducing agent, and react at 50℃-80℃ for 3h-5h to prepare the diamine monomer.

3. The method for preparing pyrrolodiamine according to claim 2, characterized in that, In step (1), the molar ratio of p-nitrobenzaldehyde to 3,4-dimethoxyaniline, or p-nitrobenzaldehyde to 3,4,5-trimethoxyaniline, is 1:(1 to 1.1); organic solvent I is methanol, ethanol, or N,N-dimethylformamide.

4. The method for preparing pyrrolodiamine according to claim 2, characterized in that, In step (2), the molar ratio of the intermediate to 2,3-butanedione is (1.6-2):1; the molar ratio of the intermediate to p-toluenesulfonic acid is 1:(0.05-0.3); and the organic solvent II is glacial acetic acid.

5. The method for preparing pyrrolodiamine according to claim 2, characterized in that, In step (3), the metal carbon catalyst is a palladium carbon catalyst, a nickel carbon catalyst, or a platinum carbon catalyst; the weight ratio of the nitro compound to the metal carbon catalyst is 1:(0.05-0.2); the reducing agent is hydrogen, hydrazine hydrate, formic acid, ammonium formate, or sodium formate; and the organic solvent III is methanol, ethanol, or N,N-dimethylformamide, more preferably N,N-dimethylformamide.

6. A polyimide, characterized in that, The pyrrole diamine as described in claim 1 is polymerized with tetracarboxylic dianhydride and then imidized; wherein the tetracarboxylic dianhydride is 4,4'-(hexafluoroisopropene) phthalic anhydride, 4,4'-oxophthalic anhydride, or bisphenol A type diether dianhydride.

7. The method for preparing polyimide according to claim 6, characterized in that, Imidification is thermal imidization; wherein, the solid content of the polyamic acid solution used for thermal imidization is 20wt% to 35wt%; and the maximum temperature in the thermal imidization process is 250℃.

8. A polyimide film, characterized in that, It is prepared from the polyimide as described in claim 7.

9. Use of the polyimide film as described in claim 8, characterized in that, Used as a light-emitting layer in OLED devices, or as a fluorescent labeling layer.

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