A dihydric acid monomer containing a half ester ring structure, and a preparation method and application thereof

Abstract

The application discloses a diacid monomer containing a half-ester ring structure and a preparation method and application thereof. The diacid monomer containing the half-ester ring structure is a diacid monomer containing a norbornyl double benzocyclobutane structure, and the diacid monomer containing the norbornyl double benzocyclobutane structure has a structure shown in any one of the following structural formulae: The diacid monomer containing the half-ester ring structure and a diamine monomer are used in the application to prepare a colorless and transparent polyimide film through one-step polymerization, and the film has excellent optical transmittance, thermal stability and mechanical strength, and has great application potential in the fields of high-transparency flexible display devices and microelectronics.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology and organic polymer materials technology, and relates to a dianhydride monomer containing a half-ester ring structure, its preparation method and application, and particularly to a dianhydride monomer containing a norbornel dibenzocyclobutane structure and its preparation method, and a polyimide film prepared from the dianhydride monomer containing the norbornel dibenzocyclobutane structure. Background Technology

[0002] The development of microelectronic components is increasingly trending towards lightweight, high-toughness, and ultra-thin designs. Glass, as a traditional transparent substrate material, can no longer meet the future development requirements of microelectronics. Polymer materials with high light transmittance, flexibility, lightweight, and high impact resistance have become the preferred flexible materials for future microelectronics and broadcasting applications. Traditional transparent polymer materials include polyethylene terephthalate, polycarbonate, and polymethyl methacrylate. While they possess good light transmittance, their poor heat resistance and low mechanical properties cannot meet the high-temperature processing requirements of optoelectronic components. Polyimide (PI) film materials possess excellent heat resistance, thermal stability, chemical resistance, and mechanical properties, meeting the requirements of optoelectronic component processing. Therefore, colorless transparent polyimide (CPI) has become a research focus. Traditional aromatic PI films are mostly yellowish-brown in color, and their transmittance in the visible light wavelength range is low, failing to meet the application requirements of optoelectronic materials. Currently, using semi-aromatic, semi-aliphatic, or fully aliphatic polyimides can effectively reduce the color of polyimide films, but the introduction of aliphatic compounds inevitably leads to a decrease in thermal stability. Additionally, introducing rigid twisted structures or large-volume side groups into the molecular structure can also improve the color of polyimide films, but the coefficient of thermal expansion of the film increases significantly, affecting its application in the optoelectronic field. In specific practical applications, different optoelectronic applications have varying requirements for colorless and transparent polyimides. Therefore, developing polyimides with high heat resistance, low expansion, high transparency, and high mechanical properties remains a goal for researchers.

[0003] Patent CN115536666A discloses a dianhydride monomer containing a benzobisnorbornene cyclobutane structure, its preparation method, and its application. The polyimide prepared in this method has a high aliphatic ring content, which is not conducive to improving the thermal stability and mechanical properties of the polyimide film. This makes it unsuitable for applications in flexible display cover plates, flexible transparent solar cell substrate materials, and other optically transparent components. Therefore, providing an imide film with higher thermal stability and mechanical properties while maintaining excellent optical performance is an urgent problem to be solved. Summary of the Invention

[0004] The main objective of this invention is to provide a dianhydride monomer containing a half-ester ring structure, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a dianhydride monomer containing a half-ester ring structure, wherein the dianhydride monomer containing a half-ester ring structure is a dianhydride monomer containing a norbornel dibenzocyclobutane structure, and the dianhydride monomer containing the norbornel dibenzocyclobutane structure has a structure as shown in any one of formulas (I)-(VI):

[0007]

[0008] This invention provides a method for preparing the dianhydride monomer containing a half-ester ring structure, comprising:

[0009] A first mixed reaction system containing halophthalic anhydride, aqueous methylamine and a first solvent is subjected to an imide reaction at 110℃~120℃ for 12~24h to obtain halophthalic imide compounds.

[0010] Furthermore, a second mixed reaction system comprising the halophthalimide compound, norbornene, a first inorganic base, a first catalyst, a second catalyst, and a second solvent is reacted at 130°C to 150°C for 48-120 h to obtain a diimide compound containing a norbornene dibenzocyclobutane structure.

[0011] Furthermore, a third mixed reaction system comprising the diimide compound containing the norbornel dibenzocyclobutane structure, a second inorganic base, and a third solvent is reacted at 100°C to 120°C for 12-24 hours, and then the pH is adjusted to 1-2 to obtain a tetracarboxylic acid compound.

[0012] Furthermore, the tetraacid compound is subjected to high-temperature dehydration or catalytic dehydration treatment to obtain a dianhydride monomer containing a half-ester ring structure.

[0013] This invention also provides a polyimide containing a half-ester ring structure, wherein the polyimide is prepared using the aforementioned dianhydride monomer containing a half-ester ring structure.

[0014] This invention provides a method for preparing a polyimide film, comprising:

[0015] Provide the aforementioned dianhydride monomer containing a half-ester ring structure;

[0016] Under a protective atmosphere, a fourth mixed reaction system containing the dianhydride monomer, diamine monomer, third catalyst, and polar organic solvent is first heated to 80°C to dissolve, and then reacted at 180-200°C for 12-24 hours to obtain a polyimide solution.

[0017] The polyimide solution was diluted to 5-10 wt% and cooled to 80-100°C, then poured into a stirred precipitant to obtain a polyimide filament polymer.

[0018] The polyimide filaments were extracted, washed, and dried under low-boiling-point solvent conditions to obtain polyimide powder.

[0019] Furthermore, the polyimide powder is dissolved in a polar organic solvent to form a polyimide solution, and the solid content is controlled to be 8-15 wt%. Then, the polyimide solution is spread onto the substrate by a casting method and dried at 50-80°C for 4-8 hours. Finally, the film is heat-treated to obtain a polyimide film.

[0020] The present invention also provides a polyimide film prepared by the above preparation method, characterized in that the thickness of the polyimide film is 20-50 μm; the total transmittance of the polyimide film is greater than 90%, the glass transition temperature is higher than 400°C, and the optical transmittance of the film at 400 nm is greater than 80%.

[0021] The present invention also provides the use of the aforementioned polyimide or polyimide film containing a half-ester ring structure in the fields of flexible displays, thin-film solar cells, or optoelectronic engineering.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The colorless and transparent polyimide prepared by this invention has higher heat resistance, with a glass transition temperature up to 473℃, good mechanical properties, high optical transparency, and a low coefficient of thermal expansion. The obtained polymer has good solubility in various organic solvents such as N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and m-cresol. The prepared polyimide film has good mechanical properties and excellent optical transmittance. The cutoff wavelength of the colorless polyimide film is between 285 and 315 nm, and the optical transmittance of the prepared colorless polyimide film at 400 nm is >80%, reaching a maximum of 86%.

[0024] (2) This invention is the first to synthesize a dianhydride monomer containing norbornel dibenzocyclobutane structure and apply it to the preparation of colorless and transparent polyimide films. The dianhydride monomer preparation method of this invention uses readily available raw materials, is inexpensive, and has a considerable yield (greater than 51%). The colorless and transparent polyimide film prepared by this invention has good solubility, thermal stability, mechanical properties and optical properties. This material has good applications in flexible displays, solar cells and optoelectronic communications. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is the 1H NMR spectrum of the dianhydride monomer CANAL-1 prepared in Examples 3 and 4 of this invention.

[0027] Figure 2 This is the 1H NMR spectrum of the dianhydride monomer CANAL-2 prepared in Examples 3 and 4 of this invention.

[0028] Figure 3 This is the 1H NMR spectrum of the dianhydride monomer CANAL-4 prepared in Examples 1 and 2 of this invention.

[0029] Figure 4 These are the infrared spectra of the polyimides prepared in polymer synthesis 1-8 of the embodiments of the present invention. Detailed Implementation

[0030] Given the lack of dianhydride monomers containing a norbornene-bisbenzocyclobutane structure, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The main approach involves using norbornene and halophthalic anhydrides and / or derivatives of halophthalic anhydrides as initial reaction materials. First, halophthalimides are synthesized by reacting halophthalic anhydrides in acetic acid solution under acidic catalysis. Then, under alkaline conditions, the halophthalimides react with norbornene-bisbenzocyclobutane in an aromatic cyclization (CANAL) reaction catalyzed by palladium. A bisimide containing a norbornel-bisbenzocyclobutane structure was synthesized under the catalysis of a catalyst. A tetracarboxylic acid compound was then prepared via hydrolysis, followed by sublimation to obtain a dianhydride monomer. Using the prepared dianhydride monomer containing the norbornel-bisbenzocyclobutane structure and some commercially available diamine monomers as raw materials, a hemicyclic polyimide was obtained through a one-step condensation polymerization reaction and purification steps. A colorless and transparent polyimide film was then obtained by casting. The optical and thermodynamic properties of the polyimide obtained in this method were characterized by analytical testing.

[0031] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Specifically, as one aspect of the technical solution of the present invention, the dianhydride monomer containing a half-ester ring structure is a dianhydride monomer containing a norbornel bisbenzocyclobutane structure, wherein the dianhydride monomer containing a norbornel bisbenzocyclobutane structure has a structure as shown in any one of formulas (I)-(IV):

[0033]

[0034] This invention provides a method for preparing the dianhydride monomer containing the half-ester ring structure, comprising:

[0035] A first mixed reaction system containing halophthalic anhydride, aqueous methylamine and a first solvent is subjected to an imide reaction at 110℃~120℃ for 12~24h to obtain halophthalic imide compounds.

[0036] Furthermore, a second mixed reaction system comprising the halophthalimide compound, norbornene, a first inorganic base, a first catalyst, a second catalyst, and a second solvent is reacted at 130°C to 150°C for 48-120 h to obtain a diimide compound containing a norbornene dibenzocyclobutane structure.

[0037] Furthermore, a third mixed reaction system comprising the diimide compound containing the norbornel dibenzocyclobutane structure, a second inorganic base, and a third solvent is reacted at 100°C to 120°C for 12-24 hours, and then the pH is adjusted to 1-2 to obtain a tetracarboxylic acid compound.

[0038] Furthermore, the tetraacid compound is subjected to high-temperature dehydration or catalytic dehydration treatment to obtain a dianhydride monomer containing a half-ester ring structure.

[0039] In some preferred embodiments, the preparation method specifically includes: dissolving halophthalic anhydride in a first solvent, and then adding an aqueous methylamine solution dropwise to form the first mixed reaction system.

[0040] Furthermore, the halogenated phthalic anhydride includes any one or a combination of two or more of bromophthalic anhydride, chlorophthalic anhydride, and iodophthalic anhydride, and is not limited thereto.

[0041] Furthermore, the halophthalic anhydride is a bromophthalic anhydride.

[0042] In some preferred embodiments, the first solvent includes any one or a combination of two or more of acetic acid, formic acid, and propionic acid, and is not limited thereto.

[0043] Furthermore, the first solvent is acetic acid.

[0044] In some preferred embodiments, the molar ratio of the halophthalic anhydride to the aqueous methylamine solution is 1:5 to 1:10.

[0045] In some preferred embodiments, the mass ratio of the halophthalic anhydride to the first solvent is 1:10 to 1:12.

[0046] In some preferred embodiments, the first inorganic base includes any one or a combination of two or more of potassium carbonate, sodium carbonate, cesium carbonate, calcium carbonate, magnesium carbonate, sodium phosphate, potassium hydrogen phosphate, and sodium hydrogen phosphate.

[0047] Furthermore, the first inorganic base is cesium carbonate.

[0048] In some preferred embodiments, the first catalyst comprises any one or a combination of two or more of tris(dibenzylacetone)palladium, palladium acetate, tris(dibenzylacetone)palladium, tetra(triphenylphosphine)palladium, and di(tri-tert-butylphosphine)palladium.

[0049] Furthermore, the first catalyst is palladium acetate.

[0050] In some preferred embodiments, the second catalyst comprises any one or a combination of two or more of tricyclohexylphosphine, tri-tert-butylphosphine, triphenylphosphine, tri(o-methylphenyl)phosphine, tribenzylphosphine, and tetra(triphenylphosphine).

[0051] Furthermore, the second catalyst is triphenylphosphine and / or tetra(triphenylphosphine).

[0052] In some preferred embodiments, the second solvent comprises toluene and / or dioxane.

[0053] Furthermore, the second solvent is toluene.

[0054] In some preferred embodiments, the second inorganic base includes any one or a combination of two or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide.

[0055] Furthermore, the second inorganic base is sodium hydroxide.

[0056] In some preferred embodiments, the third solvent includes any one or a combination of two or more of deionized water, ethanol, and methanol.

[0057] Furthermore, the third solvent includes deionized water and / or ethanol.

[0058] In some preferred embodiments, the inorganic acids used to adjust the pH value include sulfuric acid and / or hydrochloric acid.

[0059] Furthermore, the inorganic acid used to adjust the pH value is hydrochloric acid.

[0060] In some preferred embodiments, the molar ratio of the halophthalimide compound to norbornene is 2.1:1 to 2.2:1.

[0061] In some preferred embodiments, the mass ratio of norbornene to the first inorganic base is 1:2 to 1:2.2.

[0062] In some preferred embodiments, the mass ratio of norbornene to the first catalyst and the second catalyst is 1:0.05 to 0.1:0.2 to 0.4.

[0063] In some preferred embodiments, the molar ratio of the bisimide compound containing the norbornel dibenzocyclobutane structure to the second inorganic base is 1:24 to 1:40.

[0064] Furthermore, the tetracarboxylic acid compound is sublimated under vacuum at 280–320°C to obtain a dianhydride monomer containing a half-ester ring structure, namely a dianhydride monomer containing a norbornel dibenzocyclobutane structure.

[0065] In some preferred embodiments, the halophthalimide compound has a structure shown in any one of the following formulas:

[0066]

[0067] Wherein, X is one of -Br, -Cl, and -I, but is not limited to this; preferably, it is -Br.

[0068] In some preferred embodiments, the bisimide compound containing the norbornel dibenzocyclobutane structure has any one of the structures shown in the following formulas:

[0069]

[0070] In some preferred embodiments, the tetracarboxylic acid compound has a structure shown in any one of the following formulas:

[0071]

[0072] In some preferred embodiments, the synthesis of the dianhydride monomer containing the half-ester ring structure is as follows:

[0073]

[0074] Wherein, X is one of -Br, -Cl, and -I, but is not limited to this; preferably -Br.

[0075] Another aspect of the present invention provides a polyimide containing a half-ester ring structure, wherein the polyimide is prepared using the dianhydride monomer containing the half-ester ring structure.

[0076] In some preferred embodiments, the polyimide has a structure as shown in any of formulas (V) to (VIII):

[0077]

[0078] Where n is a positive integer from 50 to 500, and the R group is selected from any of the structures shown in the following formula:

[0079]

[0080] Here, --- represents the key connection position.

[0081] Furthermore, the R residue has the structure shown in any of the following formulas:

[0082]

[0083] This invention also provides a method for preparing a polyimide film, comprising:

[0084] Provide the aforementioned dianhydride monomer containing a half-ester ring structure;

[0085] Under a protective atmosphere, a fourth mixed reaction system containing the dianhydride monomer, diamine monomer, third catalyst, and polar organic solvent is first heated to 80°C to dissolve, and then reacted at 180-200°C for 12-24 hours to obtain a polyimide solution.

[0086] The polyimide solution was diluted to 5-10 wt% and cooled to 80-100°C, then poured into a stirred precipitant to obtain a polyimide filament polymer.

[0087] The polyimide filaments were extracted, washed, and dried under low-boiling-point solvent conditions to obtain polyimide powder.

[0088] Furthermore, the polyimide powder is dissolved in a polar organic solvent to form a polyimide solution, and the solid content is controlled to be 8-15 wt%. Then, the polyimide solution is spread onto the substrate by a casting method and dried at 50-80°C for 4-8 hours. Finally, the film is heat-treated to obtain a polyimide film.

[0089] In some preferred embodiments, the preparation method specifically includes:

[0090] The diamine monomer is selected from any of the structures shown in formula (VIII):

[0091]

[0092] Furthermore, the diamine monomer is selected from any of the structures shown in the following formula:

[0093]

[0094] Furthermore, the protective atmosphere includes, but is not limited to, argon and / or nitrogen.

[0095] Further, the third catalyst comprises benzoic acid and isoquinoline; the molar ratio of the dianhydride monomer, benzoic acid, and isoquinoline is 1:0–0.5:0–0.5. Even further, the molar ratio of the dianhydride monomer, benzoic acid, and isoquinoline is 1:0.2–0.4:0.2–0.4.

[0096] Furthermore, the solid content of the fourth mixed reaction system is 10-35 wt%.

[0097] Furthermore, the molar ratio of the dianhydride monomer to the diamine monomer is 0.95 to 1.05:1.

[0098] Furthermore, the molar ratio of the fourth catalyst to the dianhydride monomer is 0.2 to 0.5:1.

[0099] Furthermore, the precipitant includes any one or a combination of two of ethanol, methanol, deionized water, and petroleum ether, and is not limited thereto.

[0100] Furthermore, the polar organic solvent includes any one or a combination of two or more of m-cresol, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide, and is not limited thereto.

[0101] Furthermore, the low-boiling-point solvent includes, but is not limited to, methanol and / or ethanol.

[0102] Furthermore, the extraction process is performed at 100–130°C for 24–48 hours.

[0103] Furthermore, the heat treatment is a stepped heating process, including 5 to 6 holding stages, each with a temperature of 100 to 300°C and a holding time of 1 to 5 hours. More specifically, the stepped heating process includes: 100°C, 150°C, 200°C, 250°C, and 300°C, each temperature held for 1 to 5 hours, preferably 1 to 2 hours per temperature, to dry the solvent.

[0104] Furthermore, the substrate comprises a glass plate and / or a polytetrafluoroethylene plate.

[0105] The present invention also provides a polyimide film prepared by the aforementioned preparation method, wherein the thickness of the polyimide film is 20-50 μm; the total light transmittance of the polyimide film is >90%, the glass transition temperature is higher than 400℃, and the maximum is 473℃, and the optical transmittance of the film at 400 nm is >80%.

[0106] The present invention also provides the use of the aforementioned polyimide or polyimide film containing a half-ester ring structure in the fields of flexible displays, thin-film solar cells, or optoelectronic engineering.

[0107] Furthermore, the uses include applications in flexible display cover plates, flexible transparent solar cell substrate materials, or optically transparent components.

[0108] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0109] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0110] Example 1

[0111] Monomer Synthesis 1:

[0112] 3-Bromophthalic anhydride (2.27 g, 10.0 mmol) was dissolved in acetic acid (22.70 g), and then a 25%-30% aqueous solution of methylamine (6.21 g, 50.0 mmol) was added dropwise to form a mixture. The mixture was refluxed at 110 °C for 12 h to induce an imide reaction. The reaction mixture was then poured into deionized water, and an insoluble precipitate formed. The precipitate was filtered, washed with plenty of deionized water, and dried. 4-Bromophthalimide compound (2.05 g, 8.54 mmol, yield 85.4%) was obtained.

[0113] Furthermore, a mixture comprising the 3-bromophthalimide compound (1.51 g, 6.3 mmol), norbornadiene (0.28 g, 3 mmol), cesium carbonate (1.95 g, 6 mmol), triphenylphosphine (0.16 g, 0.6 mmol), palladium acetate (0.034 g, 0.15 mmol), and dioxane (70 ml) was reacted at 130 °C for 48 h. After the reaction was completed, the reaction system was washed with sodium chloride aqueous solution, and the organic phase was extracted with dichloromethane. The mixture was then rotary evaporated, dried, and recrystallized to obtain two diimide compounds containing the dibenzocyclobutane norbornane structure (CANAL-Imide-3, product 0.51 g, 1.24 mmol, yield 41.3%; CANAL-Imide-4, product 0.44 g, 1.07 mmol, yield 35.7%, total yield 77%).

[0114] Furthermore, the above-mentioned diimide compounds containing the dibenzocyclobutanenorbornene structure were reacted with a mixture of sodium hydroxide, water, and ethanol at 100°C for 12 h. After cooling, the pH was adjusted to 1-2 with hydrochloric acid aqueous solution to obtain tetraacid compounds (CANAL-Acid-3 product 0.38 g, 0.90 mmol, yield 72.6%) and CANAL-Acid-4 product 0.35 g, 0.83 mmol, yield 77.6%).

[0115] Furthermore, by sublimating the aforementioned tetracarboxylic acid compound under vacuum at 280 °C, two dianhydride monomers containing bisbenzocyclobutanenorbornene structures were prepared (CANAL-3 product 0.30 g, 0.78 mmol, yield 86.7%, CANAL-4 product 0.28 g, 0.73 mmol, yield 88.0%); (the 1H NMR spectrum of CANAL-4 is shown in...) Figure 3 )

[0116] In this embodiment, the synthetic route for preparing dianhydride monomers (CANAL-3, CANAL-4) containing norbornel dibenzocyclobutane structures is shown below:

[0117]

[0118] Polymer Synthesis 1:

[0119] In this embodiment, the structural formula of polyimide is as follows:

[0120]

[0121] The specific implementation method is as follows: Under nitrogen atmosphere, ambient humidity of 42%, and temperature of 31℃, the CANAL-3 dianhydride monomer (0.3651g, 0.95mmol) obtained above was dissolved in m-cresol (1.27ml) at 80℃ with commercial diamine 2,2′-bis(trifluoromethyl)diaminobiphenyl (TFMB) (0.3203g, 1.00mmol), benzoic acid (0.0224g, 0.2mmol), and isoquinoline (0.0258g, 0.2mmol). After complete dissolution, the temperature was raised to 180℃ for condensation polymerization for 12h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 5wt% and the temperature was lowered to 80℃. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was refluxed in ethanol at 100°C for 24 hours to remove benzoic acid and isoquinoline. The polymer was then dried at 150°C for 8 hours to obtain a pure polymer (0.58 g, yield 87.0%).

[0122] Weigh 0.3g of the purified polymer and dissolve it in 3.5ml of m-cresol to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 50℃, 60℃, 70℃, and 80℃ for two hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for two hours each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0123] Example 2

[0124] Monomer Synthesis 2:

[0125] 3-Bromophthalic anhydride (6.81 g, 30.0 mmol) was dissolved in acetic acid (81.70 g), and then a 25%-30% aqueous solution of methylamine (37.27 g, 300.0 mmol) was added dropwise to form a mixture. The mixture was refluxed at 120 °C for 12 h to induce an imide reaction. The reaction mixture was then poured into deionized water, and an insoluble precipitate formed. The precipitate was filtered, washed with plenty of deionized water, and dried. 4-Bromophthalimide compound (6.70 g, 27.9 mmol, yield 93.0%) was obtained.

[0126] Furthermore, a mixture comprising the 3-bromophthalimide compound (6.34 g, 26.4 mmol), norbornadiene (1.11 g, 12 mmol), cesium carbonate (8.60 g, 26.4 mmol), triphenylphosphine (1.26 g, 4.8 mmol), palladium acetate (0.27 g, 0.15 mmol), and dioxane (150 ml) was reacted at 150 °C for 120 h. After the reaction was completed, the reaction system was washed with sodium chloride aqueous solution, and the organic phase was extracted with dichloromethane. The mixture was then rotary evaporated, dried, and recrystallized to obtain two diimide compounds containing the dibenzocyclobutane norbornane structure (CANAL-Imide-3, product 2.09 g, 5.09 mmol, yield 42.4%; CANAL-Imide-4, product 1.78 g, 4.34 mmol, yield 36.1%, total yield 78.5%).

[0127] (CANAL-Acid-3 product 1.69 g, 4.02 mmol, yield 79.0%), CANAL-Acid-4 product 1.45 g, 3.45 mmol, yield 79.5%).

[0128] Furthermore, by sublimating the aforementioned tetracarboxylic acid compound under vacuum at 280 °C, two dianhydride monomers containing bisbenzocyclobutanenorbornene structures were prepared (CANAL-3 product 1.32 g, 3.43 mmol, yield 85.3%, CANAL-4 product 1.17 g, 3.04 mmol, yield 88.1%); (the 1H NMR spectrum of CANAL-4 is shown in...) Figure 3 ).

[0129] In this embodiment, the synthetic route for preparing dianhydride monomers (CANAL-3, CANAL-4) containing norbornel dibenzocyclobutane structures is shown below:

[0130]

[0131] Polymer Synthesis 2:

[0132] In this embodiment, the structural formula of polyimide is as follows:

[0133]

[0134] The specific implementation method is as follows: Under nitrogen atmosphere, ambient humidity of 42%, and temperature of 31℃, the CANAL-4 dianhydride monomer (0.4036g, 1.05mmol) obtained above was dissolved in DMAc (5.54ml) with commercial diamine 2,2′-bis(trifluoromethyl)diaminobiphenyl (DMBZ) (0.2123g, 1.00mmol), benzoic acid (0.0448g, 0.4mmol), and isoquinoline (0.0516g, 0.4mmol) at 80℃. After complete dissolution, the temperature was raised to 200℃ for condensation polymerization for 24h to obtain a viscous polyimide solution. After the reaction was completed, DMAc was added to dilute the solid content to 10wt% and the temperature was lowered to 100℃. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was refluxed in ethanol at 130°C for 48 hours to remove benzoic acid and isoquinoline. The polymer was then dried at 150°C for 8 hours to obtain a pure polymer (0.50 g, yield 83.8%).

[0135] Weigh 0.3g of the purified polymer and dissolve it in 1.7ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 50℃, 60℃, 70℃, and 80℃ for one hour each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0136] Example 3

[0137] Monomer Synthesis 3:

[0138] 4-Bromophthalic anhydride (20.43 g, 90 mmol) was dissolved in acetic acid (220 g), and then a solution of methylamine aqueous solution (28.0 g) was slowly added dropwise to form a mixture. The mixture was refluxed at 120 °C for 12 h to induce an imide reaction. The reaction mixture was then poured into deionized water, and an insoluble precipitate formed. The precipitate was filtered, washed with a large amount of deionized water, and dried. 4-Bromophthalimide compound (20.89 g, 78.3 mmol, yield 87.0%) was obtained.

[0139] Furthermore, a mixture comprising the 4-bromophthalimide compound (5.04 g, 21 mmol), norbornadiene (0.92 g, 10 mmol), cesium carbonate (6.52 g, 20 mmol), triphenylphosphine (1.05 g, 0.4 mmol), palladium acetate (0.18 g, 0.8 mmol), and dioxane (120 ml) was reacted at 140 °C for 80 h. After the reaction was complete, the reaction system was washed with sodium chloride aqueous solution, and the organic phase was extracted with dichloromethane. The mixture was then rotary evaporated, dried, and recrystallized to obtain two diimide compounds containing norbornyl dibenzocyclobutane structures (CANAL-Imide-1 product 1.56 g, 3.8 mmol, yield 38%; CANAL-Imide-2 product 1.12 g, 2.7 mmol, yield 27%; total yield 65%).

[0140] Furthermore, the two diimide compounds containing norbornel dibenzocyclobutane structures were reacted with a mixture of sodium hydroxide, water, and ethanol at 110°C for 18 h, respectively. After cooling, the pH was adjusted to 1-2 with hydrochloric acid aqueous solution to obtain two tetraacid compounds (CANAL-Acid-1 product 1.09 g, 2.66 mmol, yield 70.0%; CANAL-Acid-2 product 0.72 g, 1.73 mmol, yield 64.1%).

[0141] Furthermore, by sublimating the two tetracarboxylic acid compounds at 280 °C under vacuum, two dianhydride monomers containing norbornel dibenzocyclobutane structures were prepared (CANAL-1 product 0.92 g, 2.23 mmol, yield 83.8%; CANAL-2 product 0.61 g, 1.47 mmol, yield 85.0%); (the 1H NMR spectra of CANAL-1 and CANAL-2 are shown in [reference needed]). Figure 1 , Figure 2 );

[0142] In this embodiment, the synthetic routes for preparing the two dianhydride monomers (CANAL-1, CANAL-2) containing norbornyl dibenzocyclobutane structures are shown below:

[0143]

[0144] Polymer Synthesis 3:

[0145] In this embodiment, the structural formula of polyimide is as follows:

[0146]

[0147] Under a nitrogen atmosphere, ambient humidity of 46%, and temperature of 30°C, the CANAL-1 dianhydride monomer (0.3843 g, 1 mmol) obtained above was dissolved in NMP (2.0 ml) with commercial diamine 2,2′-bis(trifluoromethyl)diaminobiphenyl (TFMB) (0.3203 g, 1 mmol), benzoic acid (0.0256 g), and isoquinoline (0.0294 g, 0.21 mmol) at 80°C. After complete dissolution, the temperature was raised to 190°C for condensation polymerization for 16 h to obtain a viscous polyimide solution. After the reaction was completed, NMP was added to dilute the solid content to 8 wt%. The polymer solution was poured into a stirred methanol solvent, and white filamentous polymer precipitated. The polymer was extracted by reflux in ethanol solvent for 36 h to remove benzoic acid and isoquinoline. The polymer was then dried at 150°C for 6 h to obtain a pure polymer (0.61 g, yield 86.6%).

[0148] Weigh 0.3g of the purified polymer and dissolve it in 1.9ml of NMP to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 50℃, 60℃, 70℃, 80℃, 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0149] Polymer Synthesis 4:

[0150] In this embodiment, the structural formula of polyimide is as follows:

[0151]

[0152] The specific implementation method is as follows: Under a nitrogen atmosphere, ambient humidity of 45%, and temperature of 29℃, the CANAL-1 dianhydride monomer (0.3843 g, 1 mmol) obtained above was dissolved in m-cresol (2.5 ml) at 80℃ with commercial diamine 2,2′-dimethylbenzidine (DMBZ) (0.2123 g, 1 mmol), benzoic acid (0.0366 g, 0.3 mmol), and isoquinoline (0.0387 g, 0.3 mmol). After complete dissolution, the temperature was raised to 190℃ for condensation polymerization for 14 h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 10 wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted under reflux of ethanol solvent for 42 h to remove benzoic acid and isoquinoline. Then, the polymer was dried at 150℃ for 7 h to obtain a pure polymer (0.51 g, yield 85.5%).

[0153] Weigh 0.27g of the purified polymer and dissolve it in 5.0ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 60℃, 70℃, 80℃, 100℃, and 150℃ for two hours each, and at 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0154] Polymer Synthesis 5:

[0155] In this embodiment, the structural formula of polyimide is as follows:

[0156]

[0157] The specific implementation method is as follows: Under a nitrogen atmosphere, ambient humidity of 45%, and temperature of 30℃, the CANAL-2 dianhydride monomer (0.3843 g, 1 mmol) obtained above was dissolved in m-cresol (2.1 ml) at 80℃ along with commercial diamine 2,2′-bis(trifluoromethyl)diaminobiphenyl (TFMB) (0.3203 g, 1 mmol), benzoic acid (0.0244 g, 0.2 mmol), and isoquinoline (0.0258 g, 0.2 mmol). After complete dissolution, the temperature was raised to 180℃ for condensation polymerization for 12 h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 8 wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted under reflux conditions of ethanol solvent for 42 h to remove benzoic acid and isoquinoline. Then, the polymer was dried at 130℃ for 8 h to obtain a pure polymer. (0.63g, yield 84.4%)

[0158] Weigh 0.3g of the purified polymer and dissolve it in 6.0ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 60℃, 70℃, and 80℃ for two hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0159] Example 4

[0160] Monomer Synthesis 4:

[0161] A mixture comprising the 4-bromophthalimide compound (10.32 g, 43 mmol), norbornadiene (1.84 g, 20 mmol), cesium carbonate (13.68 g, 42 mmol), triphenylphosphine (1.57 g, 6 mmol), palladium acetate (0.36 g, 0.16 mmol), and dioxane (350 ml) was reacted at 150 °C for 110 h. After the reaction was complete, the reaction system was washed with sodium chloride aqueous solution, and the organic phase was extracted with dichloromethane. The mixture was then rotary evaporated, dried, and recrystallized to obtain two diimide compounds containing norbornyl dibenzocyclobutane structures (CANAL-Imide-1 product: 3.51 g, 8.76 mmol, yield 43.8%; CANAL-Imide-2 product: 6.96 mmol, 2.86 g, yield 34.8%; total yield 78.6%).

[0162] Furthermore, the two diimide compounds containing norbornel dibenzocyclobutane structures were reacted with a mixture of sodium hydroxide, water, and ethanol at 115°C for 20 h, respectively. After cooling, the pH was adjusted to 1-2 with hydrochloric acid aqueous solution to obtain two tetraacid compounds (CANAL-Acid-1 product 3.05 g, 7.26 mmol, yield 82.9%; CANAL-Acid-2 product 2.24 g, 5.33 mmol, yield 76.6%).

[0163] Furthermore, by sublimating the two tetracarboxylic acid compounds at 280°C under vacuum, two dianhydride monomers containing norbornel dibenzocyclobutane structures were prepared (CANAL-1 product 2.35 g, yield 84.2%; CANAL-2 product 1.72 g, yield 84.1%); (the 1H NMR spectra of CANAL-1 and CANAL-2 are shown in [reference needed]). Figure 1 , Figure 2 );

[0164] In this embodiment, the synthetic routes for preparing the two dianhydride monomers (CANAL-1, CANAL-2) containing norbornyl dibenzocyclobutane structures are shown below:

[0165]

[0166] Polymer Synthesis 6:

[0167] In this embodiment, the structural formula of polyimide is as follows:

[0168]

[0169] The specific implementation method is as follows: Under nitrogen atmosphere, ambient humidity of 45%, and temperature of 32℃, the CANAL-1 dianhydride monomer (0.3843g, 1mmol) obtained above was dissolved in m-cresol (2.8ml) at 80℃ with commercial diamine 2,2′-bis(trifluoromethyl)-4,4′-diaminophenyl ether (6FODA) (0.3362g, 1mmol), benzoic acid (0.0366g, 0.3mmol), and isoquinoline (0.0387g, 0.3mmol). After complete dissolution, the temperature was raised to 185℃ for condensation polymerization for 13h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 9wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted with ethanol solvent under reflux for 40 h to remove benzoic acid and isoquinoline. The polymer was then dried at 150 °C for 6 h to obtain pure polymer (0.65 g, yield 90%).

[0170] Weigh 0.27g of the purified polymer and dissolve it in 6ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 60℃, 70℃, and 80℃ for three hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0171] Polymer Synthesis 7:

[0172] In this embodiment, the structural formula of polyimide is as follows:

[0173]

[0174] The specific implementation method is as follows: Under nitrogen atmosphere, ambient humidity of 43%, and temperature of 33℃, the CANAL-1 dianhydride monomer (0.3843g, 1mmol) obtained above was dissolved in m-cresol (3ml) at 80℃ with commercial diamine 4,4′-[1,4-phenylbis(oxy)]bis[3-(trifluoromethyl)aniline](6FAPB) (0.4283g, 1mmol), benzoic acid (0.0366g, 0.3mmol), and isoquinoline (0.0387g, 0.3mmol). After complete dissolution, the temperature was raised to 180℃ for condensation polymerization for 15h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 11wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted with ethanol solvent under reflux for 36 h to remove benzoic acid and isoquinoline. The polymer was then dried at 150 °C for 7 h to obtain pure polymer (0.76 g, yield 94%).

[0175] Weigh 0.26g of the purified polymer and dissolve it in 5.3ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 60℃, 70℃, and 80℃ for three hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0176] Polymer Synthesis 8:

[0177] In this embodiment, the structural formula of polyimide is as follows:

[0178]

[0179] The specific implementation method is as follows: Under a nitrogen atmosphere, ambient humidity of 42%, and temperature of 33℃, the CANAL-1 dianhydride monomer (0.3843 g, 1 mmol) obtained above was dissolved in m-cresol (2.6 ml) at 80℃ with commercial diamine 9,9-bis(4-amino-3-fluorophenyl)fluorene (FFDA) (0.3844 g, 1 mmol), benzoic acid (0.0244 g, 0.2 mmol), and isoquinoline (0.0387 g, 0.3 mmol). After complete dissolution, the temperature was raised to 190℃ for condensation polymerization for 15 h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 8 wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted under reflux of ethanol solvent for 48 h to remove benzoic acid and isoquinoline. Then, the polymer was dried at 150℃ for 7 h to obtain pure polymer (0.69 g, yield 90%).

[0180] Weigh 0.3g of the purified polymer and dissolve it in 6ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 60℃, 70℃, and 80℃ for two hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0181] Polymer Synthesis 9:

[0182] In this embodiment, the structural formula of polyimide is as follows:

[0183]

[0184] The specific implementation method is as follows: Under a nitrogen atmosphere, ambient humidity of 40%, and temperature of 29℃, the CANAL-1 dianhydride monomer (0.3843 g, 1 mmol) obtained above was dissolved in m-cresol (2.5 ml) at 80℃ with commercial diamine 9,9-bis(4-aminophenyl)fluorene (FDA) (0.3484 g, 1 mmol), benzoic acid (0.0366 g, 0.3 mmol), and isoquinoline (0.0258 g, 0.2 mmol). After complete dissolution, the temperature was raised to 200℃ for condensation polymerization for 12 h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 10 wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted under reflux of ethanol solvent for 24 h to remove benzoic acid and isoquinoline. Then, the polymer was dried at 150℃ for 7 h to obtain a pure polymer (0.64 g, yield 87%).

[0185] Weigh 0.25g of the purified polymer and dissolve it in 5.5ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate measuring 5*10cm and vacuum dry it at 60℃, 70℃, and 80℃ for four hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0186] Polymer Synthesis 10:

[0187] In this embodiment, the structural formula of polyimide is as follows:

[0188]

[0189] The specific implementation method is as follows: Under a nitrogen atmosphere, ambient humidity of 49%, and temperature of 36℃, the CANAL-2 dianhydride monomer (0.3843 g, 1 mmol) obtained above was dissolved in m-cresol (2.9 ml) at 80℃ along with commercial diamine 2,2′-bis(trifluoromethyl)-4,4′-diaminophenyl ether (6FODA) (0.3362 g, 1 mmol), benzoic acid (0.0244 g, 0.2 mmol), and isoquinoline (0.0258 g, 0.2 mmol). After complete dissolution, the temperature was raised to 190℃ for condensation polymerization for 16 h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 12 wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted under reflux of ethanol solvent for 48 h to remove benzoic acid and isoquinoline. Then, the polymer was dried at 150℃ for 8 h to obtain a pure polymer. (0.66g, yield 92%)

[0190] Weigh 0.30g of the purified polymer and dissolve it in 6.0ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 60℃, 70℃, and 80℃ for two hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0191] Polymer Synthesis 11:

[0192] In this embodiment, the structural formula of polyimide is as follows:

[0193]

[0194] The specific implementation method is as follows: Under a nitrogen atmosphere, ambient humidity of 41%, and temperature of 27℃, the CANAL-2 dianhydride monomer (0.3843 g, 1 mmol) obtained above was dissolved in m-cresol (3 ml) at 80℃ along with commercial diamine 4,4′-[1,4-phenylbis(oxy)]bis[3-(trifluoromethyl)aniline](6FAPB) (0.4283 g, 1 mmol), benzoic acid (0.0488 g, 0.4 mmol), and isoquinoline (0.0258 g, 0.2 mmol). After complete dissolution, the temperature was raised to 200℃ for condensation polymerization for 10 h to obtain a viscous polyimide solution. After the reaction was completed, m-cresol was added to dilute the solid content to 15 wt%. The polymer solution was poured into a stirred ethanol solvent, and white filamentous polymer precipitated. The polymer was extracted under reflux of ethanol solvent for 36 h to remove benzoic acid and isoquinoline. Then, the polymer was dried at 120℃ for 8 h to obtain a pure polymer. (0.75g, yield 92%)

[0195] Weigh 0.26g of the purified polymer and dissolve it in 5.3ml of DMAc to obtain a clear polymer solution. Then, cast the polymer solution onto a clean, dry glass plate (5*10cm). Vacuum dry the plate at 60℃, 70℃, and 80℃ for two hours each, and at 100℃, 150℃, 200℃, 250℃, and 300℃ for one hour each to remove the solvent. Then, immerse the glass plate in deionized water to remove the polyimide film. Remove the surface moisture of the film in an oven to obtain a colorless and transparent polyimide film.

[0196] Table 1. Optical and thermal properties of the thin film.

[0197]

[0198]

[0199] As can be seen from the test results in Table 1, the semi-aromatic high-transparency polyimide film prepared by this invention possesses excellent optical properties, heat resistance, and good mechanical properties; specifically, the transmittance of the film at 400 nm is >80%, and λ cut-off Below 325nm; glass transition temperature above 409℃.

[0200] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0201] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A dianhydride monomer containing a half-ester ring structure, characterized in that, The semi-ester ring structure-containing dianhydride monomer is a norbornyl double benzocyclobutane structure-containing dianhydride monomer, and the norbornyl double benzocyclobutane structure-containing dianhydride monomer has a structure as shown in any one of formulas (I)-(IV): 。 2. The method of claim 1, wherein the semi-ester ring-containing dianhydride monomer is prepared by the reaction of the semi-ester ring-containing diol monomer and the acid chloride. Comprise: The first mixed reaction system comprising halogenated phthalic anhydride, aqueous methylamine solution, first solvent is subjected to imide reaction at 110-120℃ for 12-24h to obtain halogenated phthalimide compound; wherein the halogenated phthalic anhydride comprises any one or combination of two or more of brominated phthalic anhydride, chlorinated phthalic anhydride, iodinated phthalic anhydride; The second mixed reaction system comprising the halogenated phthalimide compound, norbornadiene, first inorganic base, first catalyst, second catalyst, second solvent is reacted at 130-150℃ for 48-120h to obtain norbornyl double benzocyclobutane structure-containing bisimide compound; wherein the molar ratio of the halogenated phthalimide compound to norbornadiene is 2.1:1-2.2:1; The third mixed reaction system comprising the norbornyl double benzocyclobutane structure-containing bisimide compound, second inorganic base, third solvent is reacted at 100-120℃ for 12-24h, and then the pH value is adjusted to 1-2 to obtain tetraacid compound; And the tetraacid compound is subjected to sublimation treatment in a vacuum environment at 280-320℃ to obtain semi-ester ring structure-containing dianhydride monomer.

3. The method of claim 2, wherein the semi-ester ring-containing dianhydride monomer is prepared by the reaction of the semi-ester ring-containing diacid monomer and the phosphorus compound. The preparation method of the semi-ester ring structure-containing dianhydride monomer specifically comprises: dissolving halogenated phthalic anhydride in a first solvent, and then adding aqueous methylamine solution dropwise to form the first mixed reaction system; wherein the halogenated phthalic anhydride is brominated phthalic anhydride; the concentration of the aqueous methylamine solution is 25-30wt%.

4. The process for the preparation of semi-ester ring containing dianhydride monomers as claimed in claim 2, wherein: The first solvent comprises any one or combination of two or more of acetic acid, formic acid, propionic acid; And / or, the molar ratio of the halogenated phthalic anhydride to the aqueous methylamine solution is 1:5-1:10; And / or, the mass ratio of the halogenated phthalic anhydride to the first solvent is 1:10-1:12; And / or, the first inorganic base comprises any one or combination of two or more of potassium carbonate, sodium carbonate, cesium carbonate, calcium carbonate, magnesium carbonate, sodium phosphate, potassium hydrogen phosphate, sodium hydrogen phosphate; And / or, the first catalyst comprises any one or combination of two or more of tris(dibenzylideneacetone)dipalladium, palladium acetate, tris(dibenzylideneacetone)dipalladium, tetrakis(triphenylphosphine)palladium, bis(tri-tert-butylphosphine)palladium; And / or, the second catalyst comprises any one or combination of two or more of tricyclohexylphosphine, tri-tert-butylphosphine, triphenylphosphine, tri(o-methylphenyl)phosphine, tribenzylphosphine, tetrakis(triphenylphosphine); And / or, the second solvent comprises toluene and / or dioxane; And / or, the second inorganic base comprises any one or combination of two or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide; And / or, the third solvent comprises any one or combination of two or more of deionized water, ethanol, methanol; And / or, the inorganic acid used for adjusting the pH value comprises sulfuric acid and / or hydrochloric acid; And / or, the mass ratio of the norbornadiene and the first inorganic base is 1:2~1:2.2; And / or, the molar ratio of the norbornadiene and the first catalyst, the second catalyst is 1:0.05~0.1:0.2~0.4; And / or, the molar ratio of the double imide compound containing the norbornyl double benzocyclobutane structure and the second inorganic base is 1:24~1:

40.

5. A polyimide containing a half ester ring structure, characterized in that, The polyimide is prepared by using the dianhydride monomer containing the half-ester ring structure in claim 1.

6. The polyimide containing a half-ester ring structure according to claim 5, wherein The polyimide containing the half-ester ring structure has a structure as shown in any one of formula (V)~formula (VII): ， Wherein, n is a positive integer of 50~500, and the R group is selected from any one of the structures shown in the following formula: ； Wherein, ---represents the position of bond connection.

7. A method for producing a polyimide film, characterized by Comprise: Providing the dianhydride monomer containing the half-ester ring structure in claim 1; Under a protective atmosphere, a fourth mixed reaction system containing the dianhydride monomer, the diamine monomer, a third catalyst, and a polar organic solvent is heated and dissolved at 80℃, and then reacted at 180~200℃ for 12~24h to prepare a polyimide solution; The polyimide solution is diluted to 5~10wt% and cooled to 80~100℃, and then poured into a stirring precipitator to obtain a polyimide filamentous polymer; The polyimide filament is subjected to soxhlet treatment, washing, and drying under a low-boiling-point solvent condition to prepare a polyimide powder; And the polyimide powder is dissolved in a polar organic solvent to form a polyimide solution with a solid content of 8~15wt%, and then the polyimide solution is spread on a substrate by a flow extension method and dried at 50~80℃ for 4~8h, and then the film is subjected to heat treatment to prepare a polyimide film.

8. The method of producing a polyimide film according to claim 7, characterized by: The diamine monomer is selected from any one of the structures shown in the following formula: ； And / or, the protective atmosphere comprises argon and / or nitrogen; And / or, the third catalyst comprises benzoic acid and / or isoquinoline; the molar ratio of the dianhydride monomer, benzoic acid, and isoquinoline is 1:0~0.5:0~0.5; And / or, the solid content of the fourth mixed reaction system is 10~35wt%; And / or, the molar ratio of the dianhydride monomer and the diamine monomer is 0.95~1.05:1; And / or, the polar organic solvent comprises any one or a combination of two or more of m-cresol, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; And / or, the low-boiling-point solvent comprises methanol and / or ethanol; And / or, the soxhlet treatment is performed at 100~130℃ for 24~48h; And / or, the heat treatment is a stepwise heat treatment comprising 5~6 holding stages, and the temperature of each holding stage is 100~300℃, and the holding time is 1~2h; And / or, the substrate comprises a glass plate and / or a polytetrafluoroethylene plate.

9. The method of producing a polyimide film according to claim 8, characterized by: The molar ratio of the dianhydride monomer, benzoic acid, and the isoquinoline is 1:0.2~0.4:0.2~0.

4.

10. The polyimide film produced by the production method according to any one of claims 7 to 9, characterized by: The thickness of the polyimide film is 20~50μm; the total light transmittance of the polyimide film is greater than 90%, the glass transition temperature is higher than 400℃, and the optical transmittance of the film at 400nm is greater than 80%.

11. Use of the polyimide containing a half-ester ring structure as described in claim 5 or 6, or the polyimide film as described in claim 10, in the fields of flexible displays, thin-film solar cells, or optoelectronic engineering.

12. Use according to claim 11, characterized in that: The applications include those in flexible display cover plates, flexible transparent solar cell substrate materials, or optically transparent components.

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