Polyimide and synthesis method and application thereof

Abstract

This application belongs to the field of polymer materials, and more specifically, relates to a polyimide and its synthesis method and application. This application involves a polycondensation reaction of a first diamine monomer containing an X1 element (any one of sulfur, selenium, or tellurium), a second diamine monomer containing an X2 element (any one of carbon, oxygen, or sulfur), and a dianhydride monomer containing a fluorine group or trifluoromethyl group. This process designs the polymer chain of the polyimide, increasing its flexibility while reducing charge transfer effects within and between the molecular chains. This endows the polyimide material with solution-processable properties and improves the optical quality of films prepared based on this polyimide material. The resulting polyimide films exhibiting high refractive index and high transmittance are suitable for use as high-performance optical materials.

Description

Technical Field

[0001] This application belongs to the field of polymer materials, and more specifically, relates to a polyimide, its synthesis method and application. Background Technology

[0002] Polyimide is a type of polymer material containing an imine ring in its main chain. As a special engineering material, it has excellent environmental weather resistance, good dielectric properties and mechanical properties, and is known as "gold film". It has been widely used in aviation, aerospace, microelectronics, nanotechnology, liquid crystal, separation membrane, laser and other fields, and is considered to be one of the most promising engineering plastics of the 21st century.

[0003] Polyimide possesses a rigid structure and strong intermolecular interactions, making it difficult to dissolve in solvents and exhibiting a high flow temperature. This prevents solution processing and necessitates melt processing at high temperatures, resulting in poor processability. Furthermore, the refractive index of polyimide is generally below 1.6, lower than other aromatic polymers, limiting its application in optical materials. Additionally, due to charge transfer effects within and between polyimide molecular chains, commercially available polyimide films are typically brown or brownish-yellow with low light transmittance, hindering their use as high-performance optical materials. In summary, existing polyimide materials suffer from difficulties in solution processing and low refractive index. Moreover, the inherent color limitation of polyimide films prevents their application in the field of high-performance optical materials.

[0004] Therefore, providing a solution-processable polyimide material, and on this basis, providing a polyimide film with high refractive index and high light transmittance, is of great significance for broadening the application range of polyimide. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a polyimide and its synthesis method and application, aiming to solve the problems of poor solution processing performance, low refractive index, and low light transmittance of polyimide films, which prevent them from being used as high-performance optical materials.

[0006] To achieve the above objectives, in a first aspect, this application provides a polyimide with the following structural formula:

[0007] ,

[0008] Wherein, X1 is any one of sulfur, selenium, and tellurium;

[0009] X2 is any one of the elements carbon, oxygen, and sulfur;

[0010] R is selected from any of the following structures:

[0011] , , ;

[0012] n is an integer from 1 to 20, and the sum of n and m is an integer from 2 to 30.

[0013] Preferably, in the above-mentioned polyimide structural formula, n is an integer from 1 to 20, and the sum of n and m is an integer from 10 to 30.

[0014] More preferably, in the above-mentioned polyimide structural formula, n is an integer from 4 to 15, and the sum of n and m is an integer from 15 to 30.

[0015] Secondly, this application provides a method for synthesizing the above-mentioned polyimide, comprising the following steps:

[0016] S1. Under anhydrous, oxygen-free, and inert gas protection conditions, diamine monomer and dianhydride monomer are mixed and dissolved in an organic solvent to carry out a polycondensation reaction to obtain a polyamic acid solution.

[0017] The aforementioned diamine monomers include a first diamine monomer containing the aforementioned element X1 and a second diamine monomer containing the aforementioned element X2;

[0018] The aforementioned dianhydride monomers are dianhydride monomers containing fluorine groups or trifluoromethyl groups;

[0019] S2. Mix the above polyamic acid solution with a chemical imidizing reagent to carry out a chemical imidization reaction, obtaining a reaction solution. Then, after precipitation, washing, and drying, a fully imidized polyimide is obtained; or,

[0020] The above polyamic acid solution was coated onto a substrate and subjected to thermal imidization treatment to obtain a fully imidized polyimide.

[0021] Preferably, the first diamine monomer is one or more of 4,4'-diaminodiphenyltelluride, 4,4'-diaminodiphenylselenoether, and 4,4'-diaminodiphenylsulfide.

[0022] Preferably, the second diamine monomer is one or more of 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl sulfide.

[0023] Preferably, the dianhydride monomer is one or more of hexafluorodianhydride, 1,4-difluoro-2,3,5,6-benzenetetracarboxylic dianhydride, and 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride.

[0024] Preferably, the organic solvent is ultra-dry dimethyl sulfoxide, ultra-dry tetrahydrofuran, or ultra-dry... N,N - Dimethylformamide, ultra-dry N,N-Dimethylacetamide, ultra-dry N One or more of methylpyrrolidone.

[0025] Preferably, in step S1, the molar ratio of the first diamine monomer to the diamine monomer is (0.1~0.8):1.

[0026] Preferably, in step S1, the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.8~1.2).

[0027] Preferably, in step S1, the temperature of the polycondensation reaction is 15 ℃ to 45 ℃, and the reaction time is 8 h to 15 h.

[0028] Preferably, in step S2, the chemical imidizing agent is a mixture of acetic anhydride and pyridine.

[0029] Preferably, the temperature of the above chemical imidization reaction is 25 ℃~45 ℃, and the time of the chemical imidization reaction is 10~16 h.

[0030] Preferably, in step S2, the drying temperature is 30 ℃ to 80 ℃, and the drying time is 5 to 15 h.

[0031] Preferably, in step S2, the temperature of the above-mentioned thermal imidization is 80 ℃~200 ℃, and the thermal imidization time is 2~10 h.

[0032] Thirdly, this application provides the application of the aforementioned polyimide in the preparation of optical products with high refractive index and high transmittance.

[0033] Fourthly, this application provides a polyimide film, which is prepared by dissolving the above-mentioned polyimide and leveling agent in an additive to obtain a polyimide solution, then coating the above-mentioned polyimide solution onto a substrate, and drying it.

[0034] Preferably, the leveling agent is one or more of leveling agent 310, leveling agent 313, leveling agent 333, leveling agent 354, and leveling agent 381.

[0035] Preferably, the amount of the leveling agent added is 0.01 wt% to 2 wt% of the polyimide.

[0036] Preferably, the above-mentioned additives are dichloromethane, tetrahydrofuran, and dimethyl sulfoxide. N,N -Dimethylformamide, N,N -Dimethylacetamide, N One or more of methylpyrrolidone.

[0037] Preferably, the thickness of the polyimide film is 1~10 μm.

[0038] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages:

[0039] (1) This application designs the polymer chain of polyimide by performing a polycondensation reaction between a first diamine monomer containing an X1 element (any one of sulfur, selenium, or tellurium), a second diamine monomer containing an X2 element (any one of carbon, oxygen, or sulfur), and a dianhydride monomer, thereby increasing the flexibility of the polymer chain and reducing the charge transfer effect generated within and between the molecular chains. This endows the polyimide material with solution-processable properties and improves the optical quality of the film prepared based on the polyimide material. It can prepare polyimide films with high refractive index and high transmittance, which are suitable for use as high-performance optical materials.

[0040] (2) The polyimide provided in this application is soluble in tetrahydrofuran, dimethyl sulfoxide, N , N -Dimethylformamide, N,N -Dimethylacetamide, N Common organic solvents such as methylpyrrolidone have excellent solution processing properties.

[0041] (3) The polyimide film provided in this application has excellent optical quality, with a refractive index greater than 1.62 at a wavelength of 589 nm and a transmittance T at a wavelength of 500 nm. 500 The transmittance T at a wavelength of 400 nm is 100%. 400 Greater than 80%. Attached Figure Description

[0042] Figure 1 This is the reaction equation for synthesizing polyimide in the embodiments of this application;

[0043] Figure 2 This is the NMR spectrum of the polyimide provided in Example 1 of this application;

[0044] Figure 3 This is a refractive index curve of the polyimide film provided in the embodiments of this application;

[0045] Figure 4 This is a transmittance curve of the polyimide film provided in Example 1 of this application;

[0046] Figure 5 This is a transmittance curve of the polyimide film provided in Example 2 of this application;

[0047] Figure 6 This is the NMR spectrum of the polyimide provided in Example 4 of this application. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0049] In the description of this application, it should be understood that the term "and / or" describes a relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0050] In the specification and claims of this application, the terms “first” and “second” are used to distinguish different objects, rather than to describe a specific order of objects, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0051] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0052] In the description of this application, unless otherwise stated, "multiple" means two or more.

[0053] The term "ultra-dry solvent" refers to a solvent with extremely low water content, which can provide a purer reaction environment, reduce the interference of water on chemical reactions, and improve reaction efficiency and product quality.

[0054] This application provides a polyimide with the following structural formula:

[0055] ,

[0056] Wherein, X1 is any one of sulfur, selenium, and tellurium;

[0057] X2 is any one of the elements carbon, oxygen, and sulfur;

[0058] R is selected from any of the following structures:

[0059] , , ;

[0060] n is an integer from 1 to 20, and the sum of n and m is an integer from 2 to 30.

[0061] In some embodiments, the above-mentioned polyimide structural formula has n as an integer from 1 to 20, and the sum of n and m is an integer from 10 to 30.

[0062] In a preferred embodiment, the structure of the polyimide described above, n is an integer from 4 to 15, and the sum of n and m is an integer from 15 to 30.

[0063] On the other hand, this application also provides a method for synthesizing the above-mentioned polyimide, and the reaction equation for synthesizing the above-mentioned polyimide is as follows: Figure 1 As shown, the synthesis method includes the following steps:

[0064] S1. Under anhydrous, oxygen-free, and inert gas protection conditions, diamine monomer and dianhydride monomer are mixed and dissolved in an organic solvent to carry out a polycondensation reaction to obtain a polyamic acid solution.

[0065] The aforementioned diamine monomers include a first diamine monomer containing the aforementioned element X1 and a second diamine monomer containing the aforementioned element X2;

[0066] The aforementioned dianhydride monomers are dianhydride monomers containing fluorine groups or trifluoromethyl groups;

[0067] S2. The above polyamic acid solution and chemical imidizing reagent are mixed to carry out a chemical imidization reaction to obtain a reaction solution. Then, after precipitation, washing and drying, a fully imidized polyimide is obtained.

[0068] In some embodiments, in step S1, the first diamine monomer is one or more of 4,4'-diaminodiphenyltelluride, 4,4'-diaminodiphenylselenoether, and 4,4'-diaminodiphenylsulfide.

[0069] In some embodiments, in step S1, the second diamine monomer is one or more of 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl sulfide.

[0070] In some embodiments, in step S1, the dianhydride monomer is one or more of hexafluorodianhydride, 1,4-difluoro-2,3,5,6-benzenetetracarboxylic dianhydride, and 9,9-bis(trifluoromethyl)-2,3,6,7-oxanthracene tetracarboxylic dianhydride (CAS No. 139162-14-4).

[0071] In some embodiments, when the dianhydride monomer is hexafluorodianhydride, the structural formula of the polyimide is as follows:

[0072] ,

[0073] Wherein, X1 is any one of sulfur, selenium, and tellurium;

[0074] X2 is any one of the elements carbon, oxygen, and sulfur;

[0075] n is an integer from 1 to 20, and the sum of n and m is an integer from 2 to 30.

[0076] In some embodiments, when the dianhydride monomer is hexafluorodianhydride, in the structural formula of the polyimide, n is an integer from 1 to 20, and the sum of n and m is an integer from 10 to 30.

[0077] In a preferred embodiment, when the dianhydride monomer is hexafluorodianhydride, in the structural formula of the polyimide, n is an integer from 4 to 15, and the sum of n and m is an integer from 15 to 30.

[0078] In some embodiments, in step S1, the organic solvent is ultra-dry dimethyl sulfoxide, ultra-dry tetrahydrofuran, or ultra-dry... N,N - Dimethylformamide, ultra-dry N,N -Dimethylacetamide, ultra-dry N One or more of methylpyrrolidone. This application does not limit the source of the above-mentioned ultra-drying solvent, which can be purchased from commercially available products.

[0079] In some embodiments, the molar ratio of the first diamine monomer to the diamine monomer is (0.1~0.8):1.

[0080] In some embodiments, the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.8~1.2).

[0081] In some embodiments, in step S1, the temperature of the polycondensation reaction is 15 ℃ to 45 ℃, and the reaction time is 8 to 15 h.

[0082] In a preferred embodiment, in step S1, the temperature of the polycondensation reaction is 30 ℃~35 ℃, and the time of the polycondensation reaction is 10~12 h.

[0083] In some embodiments, in step S2, during the chemical imidization process, the chemical imidizing agent is a mixture of acetic anhydride and pyridine. It is understood that this application does not limit the volume fraction of acetic anhydride in the mixture, nor the ratio of the chemical imidizing agent to the polyamic acid solution; any method that can prepare a fully imidized polyimide is within the scope of protection of this application. In some embodiments, the volume fraction of acetic anhydride in the mixture can be 30% to 80%.

[0084] In some embodiments, in step S2, the temperature of the above chemical imidization reaction is 25 ℃~45 ℃, and the time of the chemical imidization reaction is 10~16 h, which can prepare fully imidized polyimide.

[0085] In a preferred embodiment, in step S2, the temperature of the above chemical imidization reaction is 33 ℃~37 ℃, and the time of the chemical imidization reaction is 12~14 h.

[0086] In some embodiments, in step S2, the specific process of precipitation is as follows: the polyimide solution and a polar solvent are mixed for precipitation treatment.

[0087] In some embodiments, the polar solvent is one or more of anhydrous methanol, ethanol, and acetone.

[0088] In some embodiments, the drying temperature is 30 ℃ to 80 ℃, and the drying time is 5 to 15 h.

[0089] In some embodiments, during step S2, the above-mentioned thermal imidization process, the coating method is not limited, and may include, but is not limited to, spin coating, brush coating, and scraping coating. In some embodiments, the substrate may be, but is not limited to, a glass plate.

[0090] In some embodiments, the above-mentioned thermal imidization temperature is 80°C to 200°C, and the thermal imidization time is 2 to 10 h, which can prepare fully imidized polyimide.

[0091] On the other hand, this application also provides the application of the above-mentioned polyimide in the preparation of optical products with high refractive index and high transmittance.

[0092] This application also provides a polyimide film, which is prepared by dissolving the above-mentioned polyimide and leveling agent in an additive to obtain a polyimide solution, then coating the above-mentioned polyimide solution onto a substrate, and drying it.

[0093] In some embodiments, the leveling agent is one or more of leveling agent 310, leveling agent 313, leveling agent 333, leveling agent 354, and leveling agent 381.

[0094] In some embodiments, the leveling agent is added at an amount of 0.01 wt% to 2 wt% of the polyimide, which can solve the problem of film shrinkage after polyimide film formation.

[0095] In some embodiments, the above-mentioned additives are tetrahydrofuran, dichloromethane, and dimethyl sulfoxide. N,N -Dimethylformamide, N,N -Dimethylacetamide, N One or more of methylpyrrolidone.

[0096] In some embodiments, the drying temperature is 35~80 °C and the drying time is 10~120 min.

[0097] In some embodiments, the thickness of the polyimide film is 1 to 10 μm.

[0098] This application designs the polymer backbone of polyimide by performing a polycondensation reaction between a first diamine monomer containing an X1 element (any one of sulfur, selenium, or tellurium), a second diamine monomer containing an X2 element (any one of carbon, oxygen, or sulfur), and a dianhydride monomer containing a fluorine group or trifluoromethyl group. This increases the flexibility of the polymer chain, reduces the charge transfer effect within and between the molecular chains, endows the polyimide material with solution-processable properties, and improves the optical quality of films prepared based on the polyimide material. It can prepare polyimide films with high refractive index and high transmittance, suitable for use as high-performance optical materials.

[0099] It should be understood that materials of the same or similar type, model, quality, properties, or function as the reagents and instruments used in the following embodiments can be used to implement this application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0100] The following are examples and comparative examples:

[0101] Example 1

[0102] The structural formula of the polyimide provided in this embodiment is shown below:

[0103] Then, using deuterated chloroform as a solvent, the above polyimide was characterized by nuclear magnetic resonance (NMR) structure testing. The proton NMR spectrum is shown below. Figure 2 As shown.

[0104] The above-mentioned method for synthesizing polyimide includes the following steps:

[0105] S1. Preparation of polyamic acid: Under an argon atmosphere, 26.32 g of 4,4'-diaminodiphenylselenoether (the first diamine monomer), 19.82 g of 4,4'-diaminodiphenylmethane (the second diamine monomer), and 89.73 g of hexafluorodianhydride (dianhydride monomer) were placed in a reaction vessel, and 600 mL of ultra-drying water was added. N,N Dimethylformamide (DMF) was stirred until completely dissolved, and the reaction temperature was maintained at 35 °C for 10 h to obtain a polyamic acid solution.

[0106] S2. Preparation of polyimide: A mixture containing 100 mL of acetic anhydride and 34 mL of pyridine was added to the polyamic acid solution prepared in step (1). The reaction temperature was maintained at 35 °C, and the mixture was stirred for 14 h to obtain a reaction solution. The reaction solution was then dropped into anhydrous methanol to precipitate the polyimide. The precipitate was collected by filtration and dried in a vacuum oven at 45 °C for 12 h to obtain polyimide, denoted as PI-1.

[0107] The method for preparing the polyimide film provided in this embodiment includes the following steps:

[0108] 0.1 g of polyimide (PI-1), 0.0008 mL of leveling agent 310, and 1 mL of tetrahydrofuran were mixed to obtain a polyimide solution. The polyimide solution was then dropped onto inorganic glass and coated into a film using a doctor blade. The film was dried at 45 °C for 0.5 h to obtain a polyimide film with a thickness of 6 μm.

[0109] The properties of the above-mentioned polyimide and polyimide film were tested using the following methods:

[0110] (1) Solution-processable properties of polyimide: 100 mg of polyimide was placed in a sample vial equipped with a small magnetic dot, and then 1 mL of dichloromethane, tetrahydrofuran, dimethyl sulfoxide, and... N,N -Dimethylformamide, N,N -Dimethylacetamide, N 1-Methylpyrrolidone was stirred at room temperature for 1 h to test the solubility of polyimide in common organic solvents, thereby determining its solution-processable properties.

[0111] (2) Refractive index of polyimide and polyimide film: tested using an ellipsometry.

[0112] (3) Transmittance of polyimide film: The transmittance of polyimide film was characterized by ultraviolet-visible spectroscopy (UV-Vis) and tested using a UV-Vis spectrophotometer.

[0113] As shown in Table 1, the polyimide prepared in this embodiment is soluble in dichloromethane (DCM), tetrahydrofuran (THF), and dimethyl sulfoxide (DMSO) at room temperature. N,N -Dimethylformamide (DMF) N,N -Dimethylacetamide (DMAc) N Organic solvents such as methylpyrrolidone (NMP) were used to demonstrate that the polyimide prepared in this embodiment possesses excellent solution-processable properties. The polyimide film prepared in this embodiment has a refractive index of 1.6261 at a wavelength of 589 nm (e.g., ...). Figure 3 As shown), the transmittance T at a wavelength of 500 nm 500The transmittance T at a wavelength of 400 nm is 100%. 400 It is 80.03% (e.g.) Figure 4 (As shown).

[0114] Example 2

[0115] The structural formula of the polyimide provided in this embodiment is shown below:

[0116] .

[0117] The above-mentioned method for synthesizing polyimide includes the following steps:

[0118] S1. Preparation of polyamic acid: Under an argon atmosphere, 11.92 g of 4,4'-diaminodiphenyl sulfide (the first diamine monomer), 33.40 g of 4,4'-diaminodiphenyl ether (the second diamine monomer), and 89.73 g of hexafluorodianhydride (dianhydride monomer) were placed in a reaction vessel, and 600 mL of ultra-drying water was added. N , N Dimethylformamide (DMF) was stirred until completely dissolved, and the reaction temperature was maintained at 35 °C for 10 h to obtain a polyamic acid solution.

[0119] S2. Preparation of polyimide: A mixture containing 100 mL of acetic anhydride and 34 mL of pyridine was added to the polyamic acid solution prepared in step (1). The reaction temperature was maintained at 35 °C, and the mixture was stirred for 14 h to obtain a reaction solution. The reaction solution was then dropped into anhydrous methanol to precipitate the polyimide. The precipitate was collected by filtration and dried in a vacuum oven at 30 °C for 15 h to obtain polyimide, denoted as PI-2.

[0120] The method for preparing the polyimide film provided in this embodiment includes the following steps:

[0121] Add 0.1 g of polyimide (PI-2), 0.0006 mL of leveling agent 310, and 1 mL of... N,N Dimethylformamide was mixed to obtain a polyimide solution, which was then dropped onto inorganic glass and coated into a film using a doctor blade. The film was dried at 60 °C for 1 h to obtain a polyimide film with a thickness of 6 μm.

[0122] The properties of the polyimide and polyimide film prepared in this example were tested according to the method provided in Example 1.

[0123] As can be seen from Table 1, the polyimide prepared in this embodiment is soluble in dimethyl sulfoxide at room temperature. N,N -Dimethylformamide, N,N -Dimethylacetamide, N-Methylpyrrolidone; when dichloromethane and tetrahydrofuran are heated to 50 °C, the above-mentioned polyimide can be completely dissolved, indicating that the polyimide prepared in this example has good solution-processable properties. The polyimide film prepared in this example has a refractive index of 1.6261 at a wavelength of 589 nm (e.g., ...). Figure 3 (As shown); transmittance T at a wavelength of 500 nm 500 The transmittance T at a wavelength of 400 nm is 100%. 400 It is 83.41% (e.g.) Figure 5 (As shown).

[0124] Example 3

[0125] The structural formula of the polyimide provided in this embodiment is shown below:

[0126] .

[0127] The above-mentioned method for synthesizing polyimide includes the following steps:

[0128] S1. Preparation of polyamic acid: Under an argon atmosphere, 18.48 g of 4,4'-diaminodiphenylselenoether (the first diamine monomer), 21.02 g of 4,4'-diaminodiphenyl ether (the second diamine monomer), and 89.73 g of hexafluorodianhydride (dianhydride monomer) were placed in a reaction vessel, and 600 mL of ultra-drying water was added. N,N Dimethylformamide (DMF) was stirred until completely dissolved, and the reaction temperature was maintained at 35 °C for 10 h to obtain a polyamic acid solution.

[0129] S2. Preparation of polyimide: A mixture containing 100 mL of acetic anhydride and 34 mL of pyridine was added to the polyamic acid solution prepared in step (1). The reaction temperature was maintained at 35 °C, and the mixture was stirred for 14 h to obtain a reaction solution. The reaction solution was then added dropwise to anhydrous methanol to precipitate the polyimide. The precipitate was collected by filtration and dried in a vacuum oven at 80 °C for 5 h to obtain polyimide, denoted as PI-3.

[0130] The method for preparing the polyimide film provided in this embodiment includes the following steps:

[0131] 0.1 g of polyimide (PI-3), 0.001 mL of leveling agent 310, and 1 mL of tetrahydrofuran were mixed to obtain a polyimide solution. The polyimide solution was then dropped onto inorganic glass and coated into a film using a doctor blade. The film was dried at 45 °C for 1 h to obtain a polyimide film with a thickness of 6 μm.

[0132] The properties of the polyimide and polyimide film prepared in this example were tested according to the method provided in Example 1.

[0133] As shown in Table 1, the polyimide prepared in this embodiment is soluble in dichloromethane, tetrahydrofuran, and dimethyl sulfoxide at room temperature. N,N -Dimethylformamide, N,N -Dimethylacetamide, N Organic solvents such as methylpyrrolidone were used to demonstrate that the polyimide prepared in this embodiment possesses excellent solution-processable properties. The polyimide film prepared in this embodiment has a refractive index of 1.6235 at a wavelength of 589 nm (e.g., methylpyrrolidone). Figure 3 (As shown); transmittance T at a wavelength of 500 nm 500 The transmittance T at a wavelength of 400 nm is 100%. 400 It is 85.17%.

[0134] Example 4

[0135] The structural formula of the polyimide provided in this embodiment is shown below:

[0136] Then, the above polyimide was characterized by nuclear magnetic resonance (NMR) analysis using deuterated chloroform as a solvent. The proton NMR spectrum is shown below. Figure 6 As shown.

[0137] In the above method for synthesizing polyimide, both the first and second diamine monomers are 4,4'-diaminodiphenyl sulfide, and the amount of diamine monomer used is 43.26 g. The remaining steps are the same as in Example 1, and polyimide, denoted as PI-4, is obtained.

[0138] The preparation process of the polyimide film provided in this embodiment includes the following steps:

[0139] Add 0.1 g of polyimide (PI-4), 0.001 mL of leveling agent 310, and 1 mL of... N,N Dimethylformamide was mixed to obtain a polyimide solution, which was then dropped onto inorganic glass and coated into a film using a doctor blade. The film was dried at 60 °C for 0.5 h to obtain a polyimide film with a thickness of 6 μm.

[0140] The properties of the polyimide and polyimide film prepared in this example were tested according to the method provided in Example 1.

[0141] As can be seen from Table 1, the polyimide prepared in this embodiment is soluble in dimethyl sulfoxide at room temperature. N,N -Dimethylformamide, N,N -Dimethylacetamide, N-Methylpyrrolidone; when tetrahydrofuran is heated to 50 °C, the above polyimide can be completely dissolved, but is insoluble in dichloromethane; indicating that the polyimide prepared in this example has good solution-processable properties. The polyimide film prepared in this example has a refractive index of 1.6201 at a wavelength of 589 nm; and a transmittance T at a wavelength of 500 nm. 500 The transmittance T at a wavelength of 400 nm is 100%. 400 It is 88.76%.

[0142] Example 5

[0143] The structural formula of the polyimide provided in this embodiment is shown below:

[0144] .

[0145] The above-mentioned method for synthesizing polyimide includes the following steps:

[0146] S1. Preparation of polyamic acid: Under an argon atmosphere, 24.95 g of 4,4'-diaminodiphenyltelluride ether (the first diamine monomer), 31.72 g of 4,4'-diaminodiphenylmethane (the second diamine monomer), and 89.73 g of hexafluorodianhydride (dianhydride monomer) were placed in a reaction vessel, and 600 mL of ultra-drying water was added. N,N Dimethylformamide (DMF) was stirred until completely dissolved, and the reaction temperature was maintained at 35 °C for 10 h to obtain a polyamic acid solution.

[0147] S2. Preparation of polyimide: A mixture containing 100 mL of acetic anhydride and 34 mL of pyridine was added to the polyamic acid solution prepared in step (1). The reaction temperature was maintained at 35 °C, and the mixture was stirred for 14 h to obtain a reaction solution. The reaction solution was then dropped into anhydrous methanol to precipitate the polyimide. The precipitate was collected by filtration and dried in a vacuum oven at 60 °C for 5 h to obtain polyimide, denoted as PI-5.

[0148] The method for preparing the polyimide film provided in this embodiment includes the following steps:

[0149] 0.1 g of polyimide (PI-5), 0.001 mL of leveling agent 310, and 1 mL of tetrahydrofuran were mixed to obtain a polyimide solution. The polyimide solution was then dropped onto inorganic glass and coated into a film using a doctor blade. The film was dried at 45 °C for 0.5 h to obtain a polyimide film with a thickness of 6 μm.

[0150] The preparation method of the polyimide film provided in this embodiment is the same as that in Embodiment 1.

[0151] The properties of the polyimide and polyimide film prepared in this example were tested according to the method provided in Example 1.

[0152] Test results show that the polyimide prepared in this embodiment is soluble in dichloromethane, tetrahydrofuran, and dimethyl sulfoxide at room temperature. N,N -Dimethylformamide, N,N -Dimethylacetamide, N Organic solvents such as methylpyrrolidone were used to demonstrate that the polyimide prepared in this embodiment possesses excellent solution-processable properties. The polyimide film prepared in this embodiment has a refractive index of 1.638 at a wavelength of 589 nm and a transmittance T at a wavelength of 500 nm. 500 The transmittance T at a wavelength of 400 nm is 100%. 400 It is 85.5%.

[0153] Comparative Example 1

[0154] The structural formula of the polyimide provided in this comparative example is shown below:

[0155] .

[0156] The above-mentioned method for synthesizing polyimide includes the following steps:

[0157] S1. Preparation of polyamic acid: Under an argon atmosphere, 26.41 g of 4,4'-diaminodiphenylselenoether and 44.40 g of hexafluorodianhydride (dianhydride monomer) were placed in a reaction vessel, and 300 mL of ultra-drying water was added. N,N Dimethylformamide (DMF) was stirred until completely dissolved, and the reaction temperature was maintained at 35 °C for 10 h to obtain a polyamic acid solution.

[0158] S2. Preparation of polyimide: A mixture containing 100 mL of acetic anhydride and 34 mL of pyridine was added to the polyamic acid solution prepared in step (1). The reaction temperature was maintained at 35 °C, and the mixture was stirred for 14 h to obtain a reaction solution. The reaction solution was then dropped into anhydrous methanol to precipitate the polyimide. The precipitate was collected by filtration and dried in a vacuum oven at 60 °C for 5 h to obtain polyimide, denoted as PI-6.

[0159] The method for preparing the polyimide film provided in this comparative example includes the following steps:

[0160] 0.1 g of polyimide (PI-6), 0.001 mL of leveling agent 310, and 1 mL of tetrahydrofuran were mixed at 50 °C to obtain a polyimide solution. The polyimide solution was then dropped onto inorganic glass and coated into a film using a doctor blade. The film was dried at 45 °C for 0.5 h to obtain a polyimide film with a thickness of 6 μm.

[0161] The preparation method of the polyimide film provided in this comparative example is the same as that in Example 1.

[0162] The properties of the polyimide and polyimide film prepared in this comparative example were tested according to the method provided in Example 1.

[0163] Test results show that the polyimide prepared in this comparative example is soluble in dichloromethane, tetrahydrofuran, and dimethyl sulfoxide when heated to 50 °C. N,N -Dimethylformamide, N,N -Dimethylacetamide, N -Methylpyrrolidone. The polyimide film prepared in this comparative example has a refractive index of 1.641 at a wavelength of 589 nm; and a transmittance T at a wavelength of 400 nm. 400 With a transmittance of only 21.2%, it does not meet the requirements and cannot be used as a high-performance optical material.

[0164] Comparative Example 2

[0165] The structural formula of the polyimide provided in this comparative example is shown below:

[0166] .

[0167] The method for synthesizing this polyimide includes the following steps:

[0168] S1. Preparation of polyamic acid: Under an argon atmosphere, 19.81 g of 4,4'-diaminodiphenylmethane and 21.82 g of pyromellitic dianhydride (dianhydride monomer) were placed in a reaction vessel, and 300 mL of ultra-drying water was added. N,N Dimethylformamide (DMF) was stirred until completely dissolved, and the reaction temperature was maintained at 35 °C for 10 h to obtain a polyamic acid solution.

[0169] S2. Preparation of polyimide: A polyamic acid solution is coated onto a glass substrate and heated in a muffle furnace at 180°C for 5 hours to obtain polyimide, denoted as PI-7, through thermal imidization.

[0170] The properties of the polyimide prepared in this comparative example were tested according to the method provided in Example 1.

[0171] Test results show that the polyimide prepared in this comparative example is insoluble in dichloromethane, tetrahydrofuran, and dimethyl sulfoxide when heated to 50 °C. N,N -Dimethylformamide, N,N -Dimethylacetamide, N Organic solvents such as methylpyrrolidone do not have solution processing properties, meaning that the polyimide prepared in this comparative example cannot be used to prepare films through solution processing.

[0172] Table 1. Properties of polyimide and polyimide films prepared in Examples 1-5

[0173]

[0174] Test results show that the polyimide prepared in this application has solution-processable properties, and the polyimide film prepared based on this has excellent optical quality, with high refractive index and high transmittance. The refractive index at 589 nm wavelength is greater than 1.62, and the transmittance at 500 nm wavelength is T 500 The transmittance T at a wavelength of 400 nm is 100%. 400 All are greater than 80%, making them suitable for use as high-performance optical materials.

[0175] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A polyimide, characterized in that, Its structural formula is as follows: ， Wherein, X1 is any one of sulfur, selenium, and tellurium; X2 can be either carbon or oxygen. n is an integer from 4 to 15, and the sum of n and m is an integer from 15 to 30, where m is not 0.

2. A method for synthesizing polyimide as described in claim 1, characterized in that, Includes the following steps: S1. Under anhydrous, oxygen-free, and inert gas protection conditions, diamine monomer and dianhydride monomer are mixed and dissolved in an organic solvent to carry out a polycondensation reaction to obtain a polyamic acid solution. The diamine monomer includes a first diamine monomer containing the X1 element and a second diamine monomer containing the X2 element; The dianhydride monomer is a dianhydride monomer containing trifluoromethyl groups; S2. The polyamic acid solution and the chemical imidizing reagent are mixed to carry out a chemical imidization reaction to obtain a reaction solution. Then, after precipitation, washing, and drying, a fully imidized polyimide is obtained; or, The polyamic acid solution was coated onto a substrate and subjected to thermal imidization to obtain a fully imidized polyimide.

3. The synthesis method according to claim 2, characterized in that, The first diamine monomer is one or more of 4,4'-diaminodiphenyltelluride, 4,4'-diaminodiphenylselenoether, and 4,4'-diaminodiphenylsulfide; and / or, The second diamine monomer is one or more of 4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenylmethane; and / or, The dianhydride monomer is hexafluorodianhydride; and / or, The organic solvent is ultra-dry dimethyl sulfoxide, ultra-dry tetrahydrofuran, or ultra-dry dimethyl sulfoxide. N,N - Dimethylformamide, ultra-dry N,N -Dimethylacetamide, ultra-dry N One or more of methylpyrrolidone.

4. The synthesis method according to claim 3, characterized in that, The molar ratio of the first diamine monomer to the diamine monomer is (0.1~0.8):1; The molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.8~1.2).

5. The synthesis method according to claim 2, characterized in that, In step S1, the temperature of the polycondensation reaction is 15℃~45℃, and the reaction time is 8 h~15 h.

6. The synthesis method according to claim 2, characterized in that, In step S2, the chemical imidizing agent is a mixture of acetic anhydride and pyridine; The temperature of the chemical imidization reaction is 25 ℃~45 ℃, and the time of the chemical imidization reaction is 10~16 h; The drying temperature is 30 ℃ to 80 ℃, and the drying time is 5 to 15 h.

7. The synthesis method according to claim 2, characterized in that, In step S2, the temperature of thermal imidization is 80℃~200℃, and the time of thermal imidization is 2~10 h.

8. The application of the polyimide as described in claim 1 in the preparation of optical products with high refractive index and high transmittance.

9. A polyimide film, characterized in that, It is prepared by dissolving the polyimide and leveling agent as described in claim 1 in an additive to obtain a polyimide solution, then coating the polyimide solution onto a substrate and drying it; The additives are dichloromethane, tetrahydrofuran, and dimethyl sulfoxide. N,N -Dimethylformamide, N,N -Dimethylacetamide, N One or more of methylpyrrolidone.

10. The polyimide film according to claim 9, characterized in that, The leveling agent is one or more of leveling agent 310, leveling agent 313, leveling agent 333, leveling agent 354, and leveling agent 381; and / or, The leveling agent is added at a rate of 0.01 wt% to 2 wt% of the polyimide; and / or, The thickness of the polyimide film is 1~10 μm.

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