CN111116911B

CN111116911B - Polyimide containing benzoxazole and carbazole structures and preparation method and application thereof

Info

Publication number: CN111116911B
Application number: CN201911398995.0A
Authority: CN
Inventors: 张艺; 吴慧焱; 龙禹波; 陈玥琪; 蒋星; 池振国; 刘四委; 许家瑞
Original assignee: National Sun Yat Sen University
Current assignee: National Sun Yat Sen University
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2020-12-29
Anticipated expiration: 2039-12-30
Also published as: CN111116911A

Abstract

The invention discloses polyimide containing benzoxazole and carbazole structures and a preparation method and application thereof, starting from dihalogenated carbazole, grafting a benzoxazole-containing structural unit by using active hydrogen in monomer carbazole, preparing a novel functional diamine monomer with benzoxazole and carbazole structures through Suzuki reaction or direct liquid ammonia ammoniation, and then using the diamine compound for synthesizing high-performance and functional polymers such as novel polyimide, polyamide, polyesterimide and the like; the polyimide material synthesized by the diamine monomer has high thermal stability, obvious fluorescence characteristic and high luminous intensity.

Description

Polyimide containing benzoxazole and carbazole structures and preparation method and application thereof

Technical Field

The invention relates to the technical field of material science, in particular to polyimide containing benzoxazole and carbazole structures, and a preparation method and application thereof.

Background

Polyimide is a high-performance polymer containing imide rings on a main chain, is one of the best heat-resistant varieties in the existing industrialized engineering plastics, has outstanding performances incomparable with other materials, such as high mechanical strength, high and low temperature resistance, chemical corrosion resistance, good dimensional stability, excellent film forming property and the like, and therefore has wide application in the fields of aerospace, microelectronics, military industry, liquid crystal display and the like. On the other hand, with the progress of display technology, organic light emitting diodes have become one of the research hotspots in the field of organic photovoltaics in the last decade due to their advantages of active light emission, full-color display, low power consumption, low starting voltage, high brightness, fast response, simple processing technology, low cost, etc. Compared with organic micromolecule luminescent materials, the polymer luminescent material can be formed into a film in a large area through various technologies such as spin coating, dipping, ink-jet printing and the like, a flexible device with a simple structure is prepared, the cost is low, the designability of the luminescent polymer is high, and the luminescent color of the luminescent polymer can be adjusted by changing the molecular structure. However, the preparation and purification processes of the polymer luminescent material are complicated, the colorization is difficult, and the service life is short, which are bottlenecks that limit the application of the polymer luminescent material in the display field. Particularly, in the process of manufacturing devices, the organic materials can have chemical changes such as oxidation and photodegradation, and the stability and the service life of the devices are seriously influenced due to the unstable size and easy crystallization of the organic materials at high temperature. Therefore, the polyimide material with excellent thermal stability can overcome the defects of common organic materials and is applied to the field of PLED luminescent materials.

Benzoxazoles have strong fluorescence and laser performance, and are often used as fluorescent probes, fluorescent whitening agents, near-ultraviolet laser dyes and sensitizing dyes and supersensitizing agents in photosensitive emulsions. In recent years, studies on some of them have been actively made because they have been found to have biological activity and to be useful as bactericides, antiseptics and antitumor agents, such as CN103333131A, CN107778301A and the like. At present, researches on benzoxazole compounds in the field of polymer luminescence are rarely reported, and the good electronic transmission capability and excellent fluorescence property of the benzoxazole compounds are utilized, and the fluorescence property and high luminescence intensity of polyimide can be effectively improved through molecular structure design.

In order to obtain polyimide with high-efficiency luminescence, different functional groups are generally introduced into diamine monomers with excellent structure designability, so that the polyimide is endowed with unique photoelectric properties. At present, polyimide with certain photoluminescence efficiency is generally introduced with organic conjugated chromophoric groups in diamine or dianhydride monomers. Such as US 5777417, CN1371932 and JP 2008297354, etc. However, in the polyimide, strong interaction exists among main chains, side groups or between the main chains and the side groups, the number of charge transfer complexes cannot be reduced, and the charge transfer effect is still strong.

Disclosure of Invention

In order to solve the technical problems, the invention provides polyimide containing benzoxazole and carbazole structures, and a preparation method and application thereof. Starting from dihalogenated carbazole, grafting a benzoxazole-containing structural unit by using active hydrogen in monomer carbazole, preparing a novel functional diamine monomer with benzoxazole and carbazole structures through Suzuki reaction or direct liquid ammonia ammoniation, and then using the diamine compound to synthesize high-performance and functional polymers such as novel polyimide, polyamide, polyesterimide and the like; the polyimide material synthesized by the diamine monomer has high thermal stability, obvious fluorescence characteristic and high luminous intensity.

One of the technical schemes of the invention is a polyimide containing benzoxazole and carbazole structures, and the structural formula of the polyimide is as follows:

wherein n and m represent polymerization degree, n/m is 1/99-100/0, X and W are tetravalent aromatic hydrocarbon group or aliphatic hydrocarbon group, Z is divalent aromatic hydrocarbon group or aliphatic hydrocarbon group, Y is one or two mixtures of groups represented by the general structural formula Y-1 or Y-2:

preferably, R in the general structural formula Y-1 or Y-2₁、R₂、R₃、R₄Selected from any one of the following structural formulas:

preferably, the preparation method of the group Y of the diamine compound containing carbazole and benzoxazole structures shown in the structural general formula Y-1 or Y-2 comprises the following steps:

(1) coupling substituted p-fluorobenzeneboronic acid and 2-chlorobenzoxazole through a Suzuki reaction to obtain a 2-substituted phenylbenzoxazole structure;

(2) grafting the group containing the benzoxazole structure obtained in the step (1) by using active hydrogen in dihalogenated carbazole monomer carbazole;

(3) preparing diamine by Suzuki coupling reaction of the structure obtained in the step (2) and p-aminobenzoic acid or m-aminobenzoic acid to obtain planar diamine containing benzoxazole and carbazole structures as described in Y-1 or Y-2.

Preferably, X or W are the same or different and are selected from one or more than one of the following tetravalent aromatic hydrocarbon group or aliphatic hydrocarbon group structural formulas:

preferably, Z is selected from any one of the following divalent aromatic or aliphatic hydrocarbon groups structural formulas:

in the second technical scheme of the invention, the preparation method of the polyimide containing the benzoxazole and carbazole structures comprises the following steps: in an argon or nitrogen atmosphere, a diamine monomer containing a Y structure or a mixed diamine containing an Y, Z structure and a dianhydride containing an X structure or a mixed dianhydride containing a X, W structure are mixed according to a molar ratio of 1: (1-1.1) dissolving in an aprotic polar organic solvent, stirring and reacting at-10-40 ℃ for 6-72 hours to obtain a polyamic acid solution, and then performing imidization by a thermal imidization method or a chemical imidization method to obtain the polyimide.

Preferably, the total mass of the diamine monomer containing a Y structure or the mixed diamine monomer containing Y and Z structures and the dianhydride monomer containing an X structure or the mixed dianhydride monomer containing X and W structures accounts for 5-50% of the total mass of the reaction material.

Preferably, the aprotic polar organic solvent is one or a mixture of two or more selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, dimethyl sulfone, 1, 4-dioxane, tetrahydrofuran and m-cresol.

Preferably, the thermal imidization method for preparing polyimide comprises the following steps: placing a polyamic acid solution in a vacuum oven, carrying out bubble pumping treatment, after bubbles are eliminated, coating the polyamic acid solution on a clean substrate in a blade mode, then placing the substrate in a high-temperature vacuum oven, and heating according to a set program: heating from room temperature to 100 ℃, keeping at 100 ℃ +/-2 ℃ for 1h, then heating to 200 ℃, keeping at 200 ℃ +/-2 ℃ for 1h, then heating to 300 ℃, keeping at 300 ℃ +/-2 ℃ for 1h, then heating to 370 ℃, and keeping at 370 ℃ +/-2 ℃ for 0.5 h; and cooling to room temperature after the treatment is finished, taking out the substrate with the polyimide film, soaking in hot water at 80-100 ℃ to strip the film, drying in vacuum at 180 ℃, and removing residual solvent to obtain the polyimide film.

Preferably, the bubbling treatment time is 0.5-1h, and the substrate is glass, copper, aluminum, iron or silicon.

Preferably, the chemical imidization method for preparing polyimide comprises the following steps:

(1) adding acetic anhydride and pyridine into a polyamic acid solution, respectively serving as a dehydrating agent and a catalyst, enabling the molar ratio of-COOH in the acetic anhydride and the polyamic acid solution to be 10:1 and the molar ratio of the acetic anhydride to the pyridine to be 5:2, stirring for 8-15 hours under the conditions that the ambient humidity is lower than 40%, the ambient temperature is 0-30 ℃ and argon is used, dropwise adding the obtained solution into an absolute ethyl alcohol or methanol solution to precipitate out, filtering and then washing with excessive distilled water, and then placing the obtained polyimide fiber in a 150 ℃ vacuum oven to be fully dried to obtain a polyimide powder material;

(2) dissolving the polyimide powder material in an aprotic polar organic solvent, placing the solution in a vacuum oven at room temperature, vacuumizing to remove bubbles, scraping the polyimide solution on a clean substrate after bubbles are removed, placing the substrate in a high-temperature vacuum oven, heating to 70-300 ℃, drying, and cooling to obtain the polyimide film.

Preferably, the aprotic polar organic solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, dimethyl sulfone, 1, 4-dioxane, tetrahydrofuran or m-cresol, the bubbling treatment time is 0.5-1h, and the substrate is glass, copper, aluminum, iron or silicon.

In the third technical scheme of the invention, the polyimide containing benzoxazole and carbazole structures is applied to preparation of luminescent layer materials, photoluminescent materials and flexible electroluminescent devices in optical equipment.

Compared with the prior art, the invention has the following beneficial effects:

the polyimide material synthesized by the diamine compound containing carbazole and benzoxazole structures has a weak electron-withdrawing luminescent element benzoxazole structure, can effectively reduce a charge transfer effect, and has good thermal stability, so that the polyimide material synthesized by taking the diamine compound as a monomer has high thermal stability, obvious fluorescence characteristic and high luminous intensity, can be widely applied to preparation of luminescent layer materials, photoluminescent materials and flexible electroluminescent devices in optical equipment, and solves the technical problems that strong interaction exists among main chains, side groups or main chains and side groups of polyimide in the prior art, the number of charge transfer complexes cannot be reduced, and the charge transfer effect is still strong.

Drawings

FIG. 1 is a thermogravimetric analysis spectrum of a polyimide prepared in example 1;

FIG. 2 is a fluorescence spectrum of a polyimide prepared in example 1;

FIG. 3 is an IR spectrum of a polyimide prepared in example 1;

FIG. 4 is a nuclear magnetic diagram of a diamine monomer prepared in example 1;

FIG. 5 is a mass spectrum of a diamine monomer prepared in example 1;

FIG. 6 is an IR spectrum of a diamine monomer prepared in example 1.

Detailed Description

The invention relates to polyimide containing benzoxazole and carbazole structures, which can be applied to preparing luminescent layer materials, photoluminescent materials and flexible electroluminescent devices in optical equipment, and has a structural general formula shown as a structural formula (I):

wherein, R in the structural general formula Y-1 or Y-2₁、R₂、R₃、R₄Selected from any one of the following structural formulas:

the preparation method of the group Y of the diamine compound containing carbazole and benzoxazole structures, which is shown in the structural general formula Y-1 or Y-2, comprises the following steps:

(1) the substituted p-fluorobenzeneboronic acid and the 2-chlorobenzoxazole are coupled through a Suzuki reaction to obtain a 2-substituted phenylbenzoxazole structure, and the structural general formula of the 2-substituted phenylbenzoxazole structure is shown as a structural formula (II):

(2) grafting active hydrogen in carbazole of a dihalogenated carbazole monomer in the step (1) to obtain a dihalogenated structure containing a carbazole benzoxazole structure, wherein the structural general formula is shown as a structural formula (III);

wherein X can be fluorine, chlorine, bromine or iodine.

(3) And (3) preparing diamine by carrying out Suzuki coupling reaction on the dihalo-structure obtained in the step (2) and 4-aminophenylboronic acid or 3-aminophenylboronic acid, wherein the diamine is reacted with the 4-aminophenylboronic acid to obtain a diamine monomer containing a Y-1 structure, as shown in a structural formula (IV), and the diamine monomer is reacted with the 3-aminophenylboronic acid to obtain a planar diamine monomer containing a Y-2 structure, as shown in a structural formula (V).

Wherein, X or W are same or different and are selected from one or more than one of the following quadrivalent aromatic hydrocarbon group or aliphatic hydrocarbon group structural formulas:

wherein Z is selected from any one of the following divalent aromatic hydrocarbon groups or aliphatic hydrocarbon groups:

example 1

(1) Preparation of diamine monomer

a. Synthesis of intermediate 2- (4-fluorophenyl) -benzoxazole

Adding 7.65g (50mmol) of 2-chlorobenzoxazole, 7.0g (50mmol) of p-fluorobenzeneboronic acid and 10.28g of potassium carbonate (75mmol) into a 250mL three-neck round-bottom flask, adding 100mL of tetrahydrofuran solution and 50mL of deionized water, magnetically stirring and introducing argon, then adding 0.05g of palladium tetratriphenylphosphine, heating to 90 ℃, stirring and reacting for 12 hours, cooling, pouring the reaction solution into water for precipitation, extracting with ethyl acetate, separating to obtain an organic layer, spinning, and purifying by column chromatography to obtain 7.67g of a white product, namely 2- (4-fluorophenyl) -benzoxazole, wherein the yield is about 72%, and the structural formula is as follows:

b. synthesis of intermediate substituted dibromocarbazole derivatives

Adding 6.39g (30mmol) of 2- (4-fluorophenyl) -benzoxazole prepared in the step a, 9.75g (30mmol) of 3, 6-dibromocarbazole and 11.7g (36mmol) of cesium carbonate into a 500mL three-neck round-bottom flask, adding 300mL of anhydrous DMF, magnetically stirring and introducing argon for protection, heating to 150 ℃, reacting for 12h, cooling, pouring the reaction liquid into water for precipitation, filtering, fully washing with methanol, recrystallizing in ethyl acetate and petroleum ether, and drying in a vacuum drying oven at 80 ℃ for 12h to obtain 12.4g of a white intermediate product with the yield of about 80%. The intermediate has the following structural formula:

c. synthesis of para-substituted target diamine monomer Y-1

Adding 5.18g (10mmol) of the substituted dibromocarbazole derivative prepared in the step b, 6.64g (24mmol) of potassium carbonate and 6.58g (24mmol) of 4-aminobenzeneboronic acid into a 250mL double-neck round-bottom flask, adding 80mL of tetrahydrofuran and 40mL of deionized water, magnetically stirring and introducing argon for protection, then adding 0.05g of palladium tetratriphenylphosphine, heating to 90 ℃ for reaction for 24 hours, cooling to room temperature, pouring the reaction liquid into water for precipitation, filtering, fully washing with methanol, drying, and purifying by column chromatography to obtain 4.45g of the target diamine monomer, wherein the yield is about 82%, and the structural formula is as follows:

(2) preparation of polyimide

2.7110g (5mmol) of the diamine monomer prepared in step (1), 4.0048g (20mmol) of 4,4' -diaminodiphenyl ether and 30.5mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and purged with argon. After stirring and complete dissolution, 5.6603g (25.25mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

(3) 47.26ml of acetic anhydride and 18.91ml of pyridine are dropwise added into the polyamic acid solution prepared in the step (2), the mixture is continuously stirred for 10 hours under the conditions of the ambient humidity of 30 percent, the temperature of 25 ℃ and the argon gas, the obtained polyimide solution is slowly poured into 1L of absolute ethyl alcohol, precipitates and is separated out, the mixture is washed by distilled water after being filtered, and the mixture is placed in a vacuum oven at the temperature of 150 ℃ and dried to obtain polyimide powder.

(4) And (3) dissolving the polyimide powder prepared in the step (3) in 30mL of N, N-dimethylformamide, placing the polyimide solution in a vacuum oven after the polyimide powder is completely dissolved, carrying out bubble extraction treatment for 0.5h, blade-coating the polyimide solution on a clean glass substrate after bubbles are eliminated, placing the substrate in a high-temperature vacuum oven, heating to 220 ℃, drying to remove the solvent, and cooling to obtain the polyimide film. The thermal weight loss curve of the polyimide film is shown in figure 1, the fluorescence spectrum is shown in figure 2, the infrared spectrum is shown in figure 3, and the nuclear magnetic spectrum is shown in figure 4. As can be seen from FIG. 3, at 1721cm^-1And 1776cm^-1Symmetric and asymmetric stretching vibration absorption peaks of carbonyl on an imide ring appear, the 5% thermal decomposition temperature of the polyimide film is 488 ℃, and the strongest fluorescence absorption peak of the polyimide film is 445 nm.

(5) The molecular structural formula of the luminescent polyimide in the embodiment is as follows:

example 2

(1) Synthesis of meta-substituted target diamine monomer 2

5.18g (10mmol) of the substituted dibromocarbazole derivative prepared in the step b of example 1, 6.64g (24mmol) of potassium carbonate and 6.58g (24mmol) of 3-aminobenzeneboronic acid are added into a 250mL double-neck round-bottom flask, 80mL of tetrahydrofuran and 40mL of deionized water are added, magnetic stirring is carried out, argon protection is introduced, then a catalytic amount of palladium tetratriphenylphosphine is added, the temperature is increased to 90 ℃ for reaction for 24 hours, the reaction solution is cooled to room temperature, poured into water for precipitation, filtered, fully washed by methanol, dried and purified by column chromatography to obtain 4.07g of the target diamine monomer, the yield is about 75%, and the structural formula is as follows:

(2) 2.1688g (4mmol) of the diamine monomer prepared in step (1), 3.2038g (16mmol) of 4,4' -diaminodiphenyl ether and 24.4mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and purged with argon. After stirring and complete dissolution, 4.5282g (20.2mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

(3) 37.81ml of acetic anhydride and 15.13ml of pyridine are dripped into the obtained polyamic acid solution drop by drop, the mixture is continuously stirred for 10 hours under the conditions of the ambient humidity of 30 percent, the temperature of 25 ℃ and the argon gas, the obtained polyimide solution is slowly poured into 1L of absolute ethyl alcohol, precipitates and is separated out, the polyimide solution is washed by distilled water after being filtered, and the polyimide solution is dried in a vacuum oven at the temperature of 150 ℃ to obtain polyimide powder.

(4) And dissolving the polyimide powder in 24mL of N, N-dimethylformamide, placing the polyimide solution in a vacuum oven after the polyimide powder is completely dissolved, carrying out bubble extraction treatment for 0.5h, carrying out blade coating on the polyimide solution on a clean glass substrate after bubbles are eliminated, placing the substrate in a high-temperature vacuum oven, heating to 150 ℃, drying to remove the solvent, and cooling to obtain the polyimide film.

example 3

(1) Preparation of diamine monomer

a. Synthesis of intermediate 2- (4-fluoro-2-methylphenyl) -benzoxazole

Adding 7.65g (50mmol) of 2-chlorobenzoxazole, 7.7g (50mmol) of 4-fluoro-2-methylbenzeneboronic acid and 10.28g of potassium carbonate (75mmol) into a 250mL three-neck round-bottom flask, adding 100mL of tetrahydrofuran solution and 50mL of deionized water, magnetically stirring and introducing argon, then adding 0.05g of palladium tetratriphenylphosphine, heating to 90 ℃, stirring and reacting for 12 hours, cooling, pouring the reaction liquid into water for precipitation, extracting with ethyl acetate, separating to obtain an organic layer, spinning to dry, and purifying by column chromatography to obtain 8.52g of a white product, namely 2- (4-fluoro-2-methylphenyl) -benzoxazole, wherein the yield is about 75 percent:

b. synthesis of intermediate substituted dibromocarbazole derivatives

6.81g (30mmol) of 2- (4-fluoro-2-methylphenyl) -benzoxazole, 9.75g (30mmol) of 3, 6-dibromocarbazole and 11.7g (36mmol) of cesium carbonate are added into a 500mL three-neck round-bottom flask, 300mL of anhydrous DMF is added, magnetic stirring is carried out, argon protection is introduced, the temperature is increased to 150 ℃, after 12 hours of reaction, cooling is carried out, the reaction liquid is poured into water for precipitation, after filtration, methanol is used for full washing, recrystallization is carried out in ethyl acetate and petroleum ether, and drying is carried out in a vacuum drying oven at 80 ℃ for 12 hours, so that 11.81g of white intermediate product is obtained, and the yield is about 74%. The intermediate has the following structural formula:

c. synthesis of para-substituted target diamine monomer 3

Adding 5.32g (10mmol) of substituted dibromocarbazole derivative, 6.64g (24mmol) of potassium carbonate and 6.58g (24mmol) of 4-aminobenzeneboronic acid in the previous step into a 250mL double-mouth round-bottom flask, adding 80mL of tetrahydrofuran and 40mL of deionized water, magnetically stirring and introducing argon for protection, then adding 0.05g of palladium tetratriphenylphosphine, heating to 90 ℃ for reaction for 24 hours, cooling to room temperature, pouring the reaction solution into water for precipitation, filtering, fully washing with methanol, drying, and purifying by column chromatography to obtain 4.23g of target diamine monomer, wherein the yield is about 76%, and the structural formula is as follows:

(2) 1.6687g (3mmol) of the diamine monomer prepared in step (1), 2.4029g (12mmol) of 4,4' -diaminodiphenyl ether and 18mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and purged with argon. After stirring and complete dissolution, 3.3962g (15.15mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

(3) Dropwise adding 28.37ml of acetic anhydride and 11.35ml of pyridine into the obtained polyamic acid solution, continuously stirring for 10 hours under the conditions of the ambient humidity of 30%, the temperature of 25 ℃ and the argon gas, slowly pouring the obtained polyimide solution into 1L of absolute ethyl alcohol, precipitating, filtering, washing with distilled water, and drying in a vacuum oven at the temperature of 150 ℃ to obtain polyimide powder.

(4) Dissolving the polyimide powder in 18mL of N, N-dimethylformamide, placing the polyimide solution in a vacuum oven after the polyimide powder is completely dissolved, carrying out bubble extraction treatment for 0.5h, carrying out blade coating on the polyimide solution on a clean glass substrate after bubbles are eliminated, placing the substrate in a high-temperature vacuum oven, heating to 220 ℃, drying to remove the solvent, and cooling to obtain the polyimide film.

example 4

(1) Synthesis of meta-substituted target diamine monomer 4

5.32g (10mmol) of substituted dibromo derivative in example 3, 6.64g (24mmol) of potassium carbonate and 6.58g (24mmol) of 3-aminobenzeneboronic acid are added into a 250mL double-neck round-bottom flask, 80mL of tetrahydrofuran and 40mL of deionized water are added, magnetic stirring is carried out, argon protection is introduced, then a catalytic amount of tetrakistriphenylphosphine palladium is added, the temperature is increased to 90 ℃, after 24 hours of reaction, the reaction solution is cooled to room temperature, poured into water for precipitation, filtered, fully washed by methanol, dried and purified by column chromatography to obtain 4.06g of target diamine monomer, the yield is about 73%, and the structural formula is as follows:

(2) 2.7812g (5mmol) of the diamine monomer, 4.0048g (20mmol) of 4,4' -diaminodiphenyl ether and 30mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and argon gas was introduced thereinto. After stirring and complete dissolution, 5.6603g (25.25mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

(3) 47.26ml of acetic anhydride and 18.91ml of pyridine are dripped into the obtained polyamic acid solution dropwise, the mixture is continuously stirred for 10 hours under the conditions of the ambient humidity of 30 percent, the temperature of 25 ℃ and the argon gas, the obtained polyimide solution is slowly poured into 1L of absolute ethyl alcohol, precipitates and is separated out, the mixture is washed by distilled water after being filtered, and the mixture is placed in a vacuum oven at the temperature of 150 ℃ to be dried to obtain polyimide powder.

(4) And (2) dissolving the polyimide powder in 30mL of N, N-dimethylformamide, placing the polyimide solution in a vacuum oven after the polyimide powder is completely dissolved, carrying out bubble extraction treatment for 0.5h, carrying out blade coating on the polyimide solution on a clean glass substrate after bubbles are eliminated, placing the substrate in a high-temperature vacuum oven, heating to 220 ℃, drying to remove the solvent, and cooling to obtain the polyimide film.

example 5

Step (1) same as example 1;

(2) 2.7110g (5mmol) of the diamine monomer synthesized in example 1, 4.0048g (20mmol) of 4,4' -diaminodiphenyl ether and 30.5mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and purged with argon. After stirring and complete dissolution, 5.6603g (25.25mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

(3) Placing the polyamic acid solution in a vacuum oven, carrying out bubble pumping treatment for 1h, after bubbles are eliminated, scraping and coating the polyamic acid solution on a clean glass substrate, then placing the substrate in a high-temperature vacuum oven, and heating according to a set program: raising the temperature from room temperature to 100 ℃, keeping the temperature at 100 +/-2 ℃ for 1h, then raising the temperature to 200 ℃, keeping the temperature at 200 +/-2 ℃ for 1h, then raising the temperature to 300 ℃, keeping the temperature at 300 +/-2 ℃ for 1h, then raising the temperature to 370 ℃, and keeping the temperature at 370 +/-2 ℃ for 0.5 h. And cooling to room temperature after the treatment is finished, taking out the substrate with the polyimide film, and soaking in hot water at 100 ℃ to strip the film. And (3) drying the obtained polyimide film at 180 ℃ in vacuum, and removing residual solvent to obtain the polyimide film.

Example 6

The procedure of step (1) was the same as in example 2;

(2) 2.1688g (4mmol) of the diamine monomer synthesized in example 2, 3.2038g (16mmol) of 4,4' -diaminodiphenyl ether and 24.4mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and purged with argon. After stirring and complete dissolution, 4.5282g (20.2mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

Example 7

Step (1) same as example 3;

(2) 2.7812g (5mmol) of the diamine monomer synthesized in example 3, 4.0048g (20mmol) of 4,4' -diaminodiphenyl ether and 30mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and purged with argon. After stirring and complete dissolution, 5.6603g (25.25mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

Example 8

Step (1) same as example 4;

(2) 1.6687g (3mmol) of the diamine monomer synthesized in example 4, 2.4029g (12mmol) of 4,4' -diaminodiphenyl ether and 184mL of N-N dimethylformamide were placed in a 150mL three-necked flask at-10 ℃ and purged with argon. After stirring and complete dissolution, 3.3962g (15.15mmol) of hydrogenated pyromellitic anhydride is added, and stirring reaction is continued for 72h at room temperature to obtain a homogeneous, transparent and viscous polyamic acid solution.

Claims

1. A polyimide containing benzoxazole and carbazole structures is characterized in that the structural formula of the polyimide is as follows:

wherein n and m represent polymerization degrees, n/m is 1/99-100/0, X and W are tetravalent aromatic groups or aliphatic groups, Z is a divalent aromatic group or aliphatic group, and Y is one or two mixtures of groups represented by the general structural formula Y-1 or Y-2:

r in the general structural formula Y-1 or Y-2₁、R₂、R₃、R₄Selected from any one of the following structural formulas:

the X or W is the same or different and is selected from one or more than one of the following quadrivalent aromatic group or aliphatic group structural formulas:

z is selected from any one of the following bivalent aromatic group or aliphatic group structural formulas:

2. the method for preparing polyimide containing benzoxazole and carbazole structures according to claim 1, comprising the steps of: in an argon or nitrogen atmosphere, a diamine monomer containing a Y structure or a mixed diamine containing an Y, Z structure and a dianhydride containing an X structure or a mixed dianhydride containing a X, W structure are mixed according to a molar ratio of 1: (1-1.1) dissolving in an aprotic polar organic solvent, stirring and reacting at-10-40 ℃ for 6-72 hours to obtain a polyamic acid solution, and then performing imidization by a thermal imidization method or a chemical imidization method to obtain the polyimide.

3. The preparation method of the polyimide containing the benzoxazole and carbazole structures according to claim 2, wherein the total mass of the diamine monomer containing the Y structure or the mixed diamine monomer containing the Y and Z structures and the dianhydride monomer containing the X structure or the mixed dianhydride monomer containing the X and W structures accounts for 5-50% of the total mass of the reaction materials.

4. The method of claim 2, wherein the aprotic polar organic solvent is one or a mixture of two or more selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, dimethylsulfone, 1, 4-dioxane, tetrahydrofuran, and m-cresol.

5. The method for preparing polyimide containing benzoxazole and carbazole structures according to claim 2, wherein said thermal imidization method is used to prepare polyimide, and comprises the following steps: placing a polyamic acid solution in a vacuum oven, carrying out bubble pumping treatment, coating the polyamic acid solution on a clean substrate in a blade mode, then placing the substrate in a high-temperature vacuum oven, and heating according to a set program: heating from room temperature to 100 ℃, keeping at 100 ℃ +/-2 ℃ for 1h, then heating to 200 ℃, keeping at 200 ℃ +/-2 ℃ for 1h, then heating to 300 ℃, keeping at 300 ℃ +/-2 ℃ for 1h, then heating to 370 ℃, and keeping at 370 ℃ +/-2 ℃ for 0.5 h; and cooling to room temperature after the treatment is finished, taking out the substrate with the polyimide film, soaking in hot water at the temperature of 80-100 ℃ to strip the film, and drying in vacuum at the temperature of 180 ℃ to obtain the polyimide film.

6. The method for preparing polyimide containing benzoxazole and carbazole structures according to claim 2, wherein said chemical imidization method comprises the following steps:

(1) adding acetic anhydride and pyridine into a polyamic acid solution to ensure that the molar ratio of-COOH in the acetic anhydride and the polyamic acid solution is 10:1 and the molar ratio of the acetic anhydride to the pyridine is 5:2, stirring for 8-15h under the conditions that the ambient humidity is lower than 40%, the ambient temperature is 0-30 ℃ and argon is used, dropwise adding the obtained solution into an absolute ethyl alcohol or methanol solution to precipitate out, filtering, washing with distilled water, and fully drying in a vacuum oven at 150 ℃ to obtain a polyimide powder material;

7. Use of the polyimide containing benzoxazole and carbazole structures according to claim 1 in the preparation of light-emitting layer materials, photoluminescent materials, and flexible electroluminescent devices in optical devices.