Photochromic polyimide material, method for its preparation, coating, coating layer, optical device and applications

Abstract

Photochromic polyimide material and preparation method, coating, coating, optical device and application; photochromic polyimide material, by introducing photochromic unit into polyimide structure, the material can quickly respond and present color change under ultraviolet light irradiation, and restore to colorless state by visible light or heating; and the polyimide matrix provides high mechanical strength, thermal stability and chemical resistance, so that the material maintains stable color changing ability in multiple light-color changing cycles. At the same time, the weather resistance of the material is greatly improved, which can adapt to outdoor and harsh environment, and expands the application prospect of the material in the fields of intelligent coating, optical device, sensor and the like, thereby solving the problem that the existing photochromic material cannot simultaneously have photoresponsivity, mechanical performance, chemical stability and weather resistance.

Description

Technical Field

[0001] This invention relates to the field of photochromic materials, and more particularly to a photochromic polyimide material, its preparation method, coating, coating layer, optical device, and application. Background Technology

[0002] Existing photochromic materials, due to their reversible color change under light stimulation, are widely used in smart coatings, optical devices, sensors, and information storage. Among them, naphthol pyran compounds are typical photochromic materials. Ultraviolet light irradiation induces heterolytic cleavage of CO bonds, leading to a significant change in molecular structure, typically manifesting as a color change from a colorless state to a colored state, with absorption spectra in the 400-500 nm range. Removal of light or heating can restore the molecules to a colorless, closed-ring state. This property makes naphthol pyran materials highly promising for reversible color-changing applications.

[0003] Although existing naphthol-pyran-based photochromic materials exhibit good photoresponse capabilities, they still have the following shortcomings in practical applications: ① Poor stability of photochromic materials: Most photochromic materials are prone to irreversible degradation or degeneration of molecular structure during multiple light exposure-color change cycles, which leads to weakened color change depth, prolonged reaction time, and affects the service life of the material. ② Insufficient mechanical properties: Most photochromic materials are small molecules or polymers with low mechanical strength, making it difficult to maintain structural stability in high-stress environments. Especially in coating applications, existing materials have poor wear resistance, tensile strength, and impact resistance, making it difficult to meet the requirements of application scenarios with high mechanical property requirements; ③ Poor chemical stability: Most photochromic materials have low chemical stability under conditions of moisture, oxygen, and temperature changes, and are prone to degradation, leading to a rapid decline in photochromic performance. In high-temperature or acidic / alkaline environments, the color-changing ability of the material decreases significantly or even completely fails, limiting its application under harsh conditions; ④ Poor weather resistance: Most photochromic materials require good resistance to ultraviolet aging if used outdoors or in high-humidity environments. However, the weather resistance of existing materials is insufficient to support long-term outdoor use, affecting their application in construction, automobiles, and other exposed environments. Summary of the Invention

[0004] The purpose of this invention is to provide a photochromic polyimide material that incorporates photochromic units into the polyimide structure. This material responds rapidly to ultraviolet light and exhibits a color change, returning to a colorless state upon exposure to visible light or heating. Simultaneously, the polyimide matrix provides high mechanical strength, thermal stability, and chemical resistance.

[0005] The present invention also proposes a method for preparing a photochromic polyimide material, which is used to prepare the above-mentioned photochromic polyimide material.

[0006] To achieve this objective, the present invention adopts the following technical solution: A photochromic polyimide material has the following chemical structural formula: ; It has a diimide structure, where R represents a divalent group that connects two imide groups.

[0007] Optimally, the diimide structure is selected from one of the following structural formulas: .

[0008] A method for preparing a photochromic polyimide material includes the following steps: The diamine compound and dianhydride were dissolved in a solvent, stirred, and a protective gas was introduced. The reaction was carried out at room temperature to obtain a polyamic acid intermediate. The reaction system was gradually heated to 150-200℃ and the reaction was continued to generate polyimide through dehydration and cyclization. After the reaction was completed, the polyimide product was precipitated, the solid was collected by filtration, washed and dried to obtain the polyimide material. The chemical structural formula of the diamine compound is: ; The chemical structural formula of dianhydride is: R represents a divalent group that connects two imide groups; The chemical structural formula of polyimide material is: ; It has a diimide structure, where R represents a divalent group that connects two imide groups.

[0009] Alternatively, the method for preparing the diamine compound may include the following steps: S1-1: Compounds A-1 and A-2 are dissolved in a solvent, stirred, and heated to 100-120℃ under a protective atmosphere; after cooling to room temperature, the solvent is removed, and the mixture is purified to obtain intermediate A-3; compound A-1 is... Compound A-2 is sodium acetylene; intermediate A-3 is... ; S1-2: Dissolve intermediate A-3 in a flux, add naphthol as compound A-4, add sodium hydroxide, and react with stirring until the nucleophilic substitution reaction is complete; after the reaction, separate the organic phase, dry, filter, and remove the solvent to obtain compound A-5; compound A-5 is... ; S1-3: Dissolve compound A-5 in concentrated sulfuric acid, add concentrated nitric acid dropwise, control the reaction temperature at 0-5℃, and stir the reaction in an ice bath; after the reaction is complete, slowly pour the reaction mixture into ice water, filter and collect the precipitate, wash the precipitate to obtain intermediate A-6; intermediate A-6 is ; S1-4: Dissolve intermediate A-6 in a solvent, add a reducing agent and concentrated hydrochloric acid, and react at 30-90℃ with stirring, maintaining an acidic environment during the reaction; after the reaction is complete, remove the reducing agent, concentrate the filtrate to dryness, dissolve the concentrate in water and adjust to alkalinity, collect the precipitated product by vacuum filtration to obtain intermediate A-7; intermediate A-7 is ; S1-5: Dissolve intermediate A-7 in acid, and slowly add sodium nitrite solution at 0-5℃ to generate a diazonium salt; after the reaction is complete, add ice water and stir; add excess water, filter the product, collect the product, and wash with water until neutral to obtain intermediate A-8; intermediate A-8 is... ; S1-6: Dissolve intermediate A-8 in solvent by stirring, add Boc anhydride-protected bromoalkylamine derivative A-9 and triethylamine, and stir to react; after the reaction is complete, wash the organic phase with water, separate the organic layer, dry and purify to obtain compound A-10; A-9, a bromoalkylamine derivative, is Intermediate A-10 is: ; S1-7: Dissolve intermediate A-10 in a solvent, add trifluoroacetic acid, remove the Boc protecting group, and generate a diamine compound.

[0010] A photoinitiator, comprising: a photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0011] A coating, the raw materials of which include: photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0012] A coating comprising: a photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0013] An optical device using photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0014] An application of a polymer in optical devices, wherein the polymer is the aforementioned photochromic polyimide material, or is prepared by the aforementioned method for preparing a photochromic polyimide material.

[0015] The application of a polymer in the preparation of smart coatings, wherein the polymer is the above-mentioned photochromic polyimide material, or is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0016] Compared with the prior art, one of the above technical solutions has the following beneficial effects: This invention introduces a photochromic unit into the polyimide structure, developing a novel polyimide material with excellent photochromic properties. This material responds rapidly to ultraviolet light irradiation and exhibits a color change, returning to a colorless state upon exposure to visible light or heating. Simultaneously, the polyimide matrix provides high mechanical strength, thermal stability, and chemical resistance, enabling the material to maintain stable color-changing ability through multiple light-induced color-changing cycles. Furthermore, the material exhibits significantly improved weather resistance, making it suitable for outdoor and harsh environments, expanding its application prospects in smart coatings, optical devices, sensors, and other fields. This addresses the problem that existing photochromic materials cannot simultaneously possess excellent photoresponsiveness, mechanical properties, chemical stability, and weather resistance. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more comprehensive description is provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0018] A photochromic polyimide material has the following chemical structural formula: ; It has a diimide structure, where R represents a divalent group that connects two imide groups.

[0019] This invention introduces a photochromic unit into the polyimide structure, developing a novel polyimide material with excellent photochromic properties. This material responds rapidly to ultraviolet light irradiation and exhibits a color change, returning to a colorless state upon exposure to visible light or heating. Simultaneously, the polyimide matrix provides high mechanical strength, thermal stability, and chemical resistance, enabling the material to maintain stable color-changing ability through multiple light-induced color-changing cycles. Furthermore, the material exhibits significantly improved weather resistance, making it suitable for outdoor and harsh environments, expanding its application prospects in smart coatings, optical devices, sensors, and other fields. This addresses the problem that existing photochromic materials cannot simultaneously possess excellent photoresponsiveness, mechanical properties, chemical stability, and weather resistance.

[0020] Optimally, the diimide structure is selected from one of the following structural formulas: .

[0021] The solvent used in this invention refers to any solvent capable of dissolving the reactants. The role of the solvent is to achieve a uniform molecular dispersion of the reactants, i.e., the dissolution process. The dissolution process includes two steps: the diffusion (endothermic) of solute molecules (or ions) and the interaction with solvent molecules to form solvated molecules (exothermic). Based on the principle of "dissolving what resembles," polar solvents are suitable for dissolving polar compounds, and nonpolar solvents are suitable for dissolving nonpolar compounds. Those skilled in the art can select an appropriate solvent based on the polarity characteristics of the reactants.

[0022] A method for preparing a photochromic polyimide material includes the following steps: A diamine compound and a dianhydride are dissolved in a solvent, stirred, and a protective gas is introduced. The reaction is carried out at room temperature to obtain a polyamic acid intermediate. The reaction system is gradually heated to 150-200℃ and the reaction is continued to dehydrate and cyclize to generate polyimide. After the reaction is complete, the polyimide product is precipitated, the solid is collected by filtration, washed, and dried to obtain the polyimide material. The solvent for this step can be anhydrous dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), etc. The molar ratio of the diamine compound to the dianhydride can be 1:(0.1-10), for example, 1:1, 1:1.05, 1:1.1, 1:1.2, etc.

[0023] The chemical structural formula of the diamine compound is: The chemical structural formula of dianhydride is: R represents a divalent group that links two imide groups; the chemical structural formula of polyimide material is: ; It has a diimide structure, where R represents a divalent group that connects two imide groups.

[0024] R represents a divalent group that connects two imide groups, and can be an atom, chain, ring, or other structure.

[0025] Alternatively, the method for preparing the diamine compound may include the following steps: S1-1: Dissolve compounds A-1 and A-2 in a solvent, stir, heat to 100-120℃, and react under a protective atmosphere; cool to room temperature, remove the solvent, and separate and purify to obtain intermediate A-3; Compound A-1 is Compound A-2 is sodium acetylene; intermediate A-3 is... ; The solvent for this step can be selected from one or a combination of anhydrous toluene, xylene, petroleum ether, n-hexane, etc. The molar ratio of compound A-1 to compound A-2 can be 1:(0.1-10), for example 1:1, 1:1.05, 1:1.1, 1:2, etc.

[0026] S1-2: Dissolve intermediate A-3 in a flux, add naphthol as compound A-4, add sodium hydroxide, and react with stirring until the nucleophilic substitution reaction is complete; after the reaction, separate the organic phase, dry, filter, and remove the solvent to obtain compound A-5; compound A-5 is... ; The solvent used in this step can be selected from one or a combination of halogenated hydrocarbon solvents (anhydrous dichloromethane, chloroform, anhydrous dichloroethane, dichloropropane, etc.), N-methylpyrrolidone, ethylene glycol ether solvents, ester solvents, etc. The molar ratio of compound A-3 to compound A-4 can be 1:(0.1-10), for example 1:1, 1:1.05, 1:1.1, 1:2, etc.

[0027] S1-3: Dissolve compound A-5 in concentrated sulfuric acid, add concentrated nitric acid dropwise, control the reaction temperature at 0-5℃, and stir the reaction in an ice bath; after the reaction is complete, slowly pour the reaction mixture into ice water, filter and collect the precipitate, wash the precipitate to obtain intermediate A-6; intermediate A-6 is ; S1-4: Dissolve intermediate A-6 in a solvent, add a reducing agent and concentrated hydrochloric acid, and react at 30-90℃ with stirring, maintaining an acidic environment during the reaction; after the reaction is complete, remove the reducing agent, concentrate the filtrate to dryness, dissolve the concentrate in water and adjust to alkalinity, collect the precipitated product by vacuum filtration to obtain intermediate A-7; intermediate A-7 is ; The solvent for this step can be selected from one or a combination of ethanol, methanol, butanol, n-propanol, isopropanol, ethylene glycol, acetone, and diethyl ether. The reducing agent can be selected from elemental metals such as magnesium (Mg), aluminum (Al), zinc (Zn), and iron (Fe).

[0028] S1-5: Dissolve intermediate A-7 in acid, and slowly add sodium nitrite solution at 0-5℃ to generate a diazonium salt; after the reaction is complete, add ice water and stir; add excess water, filter the product, collect the product, and wash with water until neutral to obtain intermediate A-8; intermediate A-8 is... ; The acid used in this step can be an acidic solution such as hydrochloric acid or sulfuric acid.

[0029] S1-6: Dissolve intermediate A-8 in solvent by stirring, add Boc anhydride-protected bromoalkylamine derivative A-9 and triethylamine, and stir to react; after the reaction is complete, wash the organic phase with water, separate the organic layer, dry and purify to obtain compound A-10; The solvent for this step can be selected from one or a combination of ethanol, methanol, butanol, n-propanol, isopropanol, ethylene glycol, acetone, diethyl ether, etc. The molar ratio of compound A-8 to compound A-9 can be 1:(0.1-10), for example 1:1, 1:2, 1:2.1, 1:2.2, etc.

[0030] A-9, a bromoalkylamine derivative, is Intermediate A-10 is: ; S1-7: Dissolve intermediate A-10 in a solvent, add trifluoroacetic acid, remove the Boc protecting group, and generate a diamine compound.

[0031] The solvent for this step can be selected from one or a combination of halogenated hydrocarbon solvents (anhydrous dichloromethane, chloroform, anhydrous dichloroethane, dichloropropane, etc.), N-methylpyrrolidone, ethylene glycol ether solvents, ester solvents, etc. The molar ratio of intermediate A-10 to trifluoroacetic acid can be 1:(0.1-10), for example 1:2, 1:2.05, 1:2.1, 1:2.2, etc.

[0032] The reaction formulas for steps S1 to S2 are as follows: .

[0033] A photoinitiator, comprising: a photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0034] A coating, the raw materials of which include: photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0035] A coating comprising: a photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0036] An optical device using photochromic polyimide material; The photochromic polyimide material is one of the above-mentioned photochromic polyimide materials, or it is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0037] Optical devices mainly include two categories: optical elements and fiber optic devices. Optical elements encompass planar optical elements, spherical optical elements, molded glass aspherical lenses, etc.; fiber optic devices include coated fiber optic devices, collimators, acousto-optic devices, etc. Their application areas cover WSS in optical communication, coherent optical modules, 5G fronthaul optical modules, data center optical modules, as well as beam combiners and splitters for lithography machine optical systems.

[0038] An application of a polymer in optical devices, wherein the polymer is the aforementioned photochromic polyimide material, or is prepared by the aforementioned method for preparing a photochromic polyimide material.

[0039] The application of a polymer in the preparation of smart coatings, wherein the polymer is the above-mentioned photochromic polyimide material, or is prepared by the above-mentioned method for preparing a photochromic polyimide material.

[0040] Example: Example 1 - Synthesis of photochromic polyimide material T-1: S1: In a dry three-necked flask, weigh 384.5 g of compound A-1 (2 mol) and add an appropriate amount of anhydrous toluene as solvent. Stir under nitrogen protection, and slowly add 96 g of compound A-2 (2 mol). Heat the reaction system to reflux temperature and maintain for 6 hours to ensure complete reaction. After the reaction is complete, cool to room temperature and remove the solvent from the reaction mixture using a rotary evaporator. Pour the residue into ice water and stir to precipitate a solid. Collect the product by filtration and wash repeatedly with deionized water until the filtrate is neutral. Recrystallize the crude product from anhydrous ethyl acetate to give 388.56 g of intermediate A-3, with a yield of 89%.

[0041] 1 H NMR (500 MHz, CDCl3) δ 7.13 (d, J = 14.8 Hz, 2H), 7.02 (d, J= 15.0Hz, 2H), 2.64 (s, 1H), 1.86 (s, 1H).

[0042] S2: In a dry three-necked flask, weigh 381.01 g of compound A-3 (1.75 mol) and add an appropriate amount of anhydrous toluene as a solvent. Under nitrogen protection, stir and slowly add 252.30 g of compound A-4 (1.75 mol). Heat the reaction system to reflux temperature and maintain for 5 hours to ensure complete reaction. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, and pour the residue into ice water while stirring to precipitate a solid. Collect the product by filtration and wash with deionized water until the filtrate is neutral. Recrystallize the crude product with anhydrous ethanol to finally obtain 482.68 g of compound A-5, with a yield of 80%. 1 H NMR (500MHz, CDCl3) δ 8.35 – 8.21 (m, 1H), 8.11 – 7.94 (m, 1H), 7.68 – 7.41 (m, 3H), 7.32 (dd, J = 14.9, 3.0 Hz, 1H), 7.13 (d, J = 14.8 Hz, 2H), 7.02 (d, J = 15.0Hz, 2H), 6.76 (d, J = 21.8 Hz, 1H), 6.59 (d, J = 21.8 Hz, 1H).

[0043] S3: Dissolve A-5 (344.45 g / mol, 1.75 mol, 602.79 g) in 1000 mL of concentrated sulfuric acid, and slowly add concentrated nitric acid (2.0 equivalents) dropwise, maintaining the reaction temperature between 0 and 5°C. After the addition is complete, continue stirring in an ice bath for 2 hours to ensure complete nitration. After the reaction is complete, slowly pour the reaction mixture into a large amount of ice water. Collect the precipitated solid by filtration and wash with cold water until neutral. Recrystallize the crude product from anhydrous ethanol to give 645.95 g of compound A-6, with a yield of 85%.

[0044] 1 H NMR (500 MHz, CDCl3) δ 9.01 (s, 2H), 8.35 – 8.24 (m, 1H), 8.08 –7.92 (m, 1H), 7.67 – 7.39 (m, 3H), 7.32 (dd, J = 14.9, 3.0 Hz, 1H), 6.80 (d,J = 21.8 Hz, 1H), 6.62 (d, J = 21.8 Hz, 1H).

[0045] S4: 651 g of compound A-6 (434 g / mol, 1.5 mol) was added to a reactor and dissolved in 1000 mL of ethanol. Iron powder (5 equivalents) and concentrated hydrochloric acid (3 equivalents) were added, and the mixture was heated and stirred at 60°C for 5 hours. After the reaction was complete, the mixture was filtered while hot to remove insoluble iron residue. The filtrate was concentrated to dryness using a rotary evaporator. The concentrate was dissolved in water and adjusted to alkalinity with ammonia. The precipitated product was collected by vacuum filtration to obtain 472.04 g of compound A-7, with a yield of 84%.

[0046] 1 H NMR (500 MHz, CDCl3) δ 8.29 (dd, J = 7.3, 1.6 Hz, 1H), 8.02 (dt, J =7.3, 1.5 Hz, 1H), 7.61 (d, J = 7.5 Hz, 1H), 7.51 (dtd, J = 21.4, 7.5, 1.6 Hz,2H), 7.32 (dd, J = 7.5, 1.4 Hz, 1H), 6.76 (d, J = 10.8 Hz, 1H), 6.61 (d, J =10.8 Hz, 1H), 5.88 (s, 2H).

[0047] S5: Compound A-7 (374.48 g / mol, 1 mol, 374.48 g) was dissolved in 300 mL of hydrochloric acid. Sodium nitrite solution (1.1 equivalents) was added at 0–5°C to form a diazonium salt. After the reaction was complete, ice water was added and stirring continued to generate compound A-8 containing a hydroxyl group. The resulting solid was collected by filtration, washed with water until neutral, and finally yielded 300.96 g of A-8, with a yield of 80%. 1 H NMR (500 MHz, CDCl3) δ 8.39 – 8.22 (m, 1H), 8.10 – 7.91(m, 1H), 7.68 – 7.21 (m, 4H), 6.93 – 6.69 (m, 3H), 6.56 (d, J = 21.8 Hz, 1H), 3.80 (s, 2H).

[0048] S6: In a dry three-necked flask, weigh A-8 (0.75 mol, 282.33 g) and dissolve it in 300 mL of anhydrous dichloromethane with stirring. Slowly add the bromoalkylamine derivative A-9 (0.75 mol, 273.04 g) and triethylamine (1.5 equivalents, 112.5 g), and stir the reaction at room temperature for 6 hours. After the reaction is complete, wash the organic phase with water, separate the organic layer, remove the solvent by rotary evaporation, and obtain the crude product. Purify by column chromatography to obtain A-10, with a yield of 440.64 g, which is 85%. 1 HNMR (500 MHz, CDCl3) δ 8.38 – 8.10 (m, 1H), 8.10 – 7.75 (m, 1H), 7.72 – 7.11(m, 4H), 6.93 – 6.28 (m, 4H), 4.39 (s, 2H), 4.21 – 3.93 (m, 4H), 3.31 – 2.98 (m, 4H), 2.15 – 1.86 (m, 4H), 1.42 (s, 18H).

[0049] S7: A-10 (0.5 mol, 345.12 g) was dissolved in 200 mL of dichloromethane, and trifluoroacetic acid (2.0 equivalents, 103.0 g) was added. The mixture was stirred at room temperature for 4 hours to remove the Boc protecting group. After the reaction was complete, the solvent was removed by rotary evaporation, and the residue was washed with saturated sodium bicarbonate solution until neutral to obtain A-11, with a yield of 333.30 g and a yield of 85%.

[0050] 1 H NMR (500 MHz, CDCl3) δ 8.34 – 8.15 (m, 1H), 8.08 – 7.83 (m, 1H), 7.78 – 7.10 (m, 4H), 6.98 – 6.21 (m, 4H), 4.11 (t, J = 9.8 Hz, 4H), 3.13 –2.54 (m, 4H), 2.27 – 1.79 (m, 4H), 1.40 (s, 4H).

[0051] S8: In a dry three-necked flask, weigh out the diamine compound (A-11, 0.1 mol, 49.0 g) and the dianhydride (AN-1, 0.1 mol, 41.8 g), and add 300 mL of anhydrous dimethylformamide (DMF) as solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-1.

[0052] 1 H NMR (500 MHz, CDCl3) δ 8.56 – 8.12 (m, 1H), 8.16 – 7.84 (m, 2H), 7.77 – 6.96 (m, 6H), 6.93 – 5.73 (m, 2H), 4.50 – 3.53 (m, 3H), 2.35 – 1.42(m, 2H), 1.11(td, J = 27.2, 2.2 Hz, 1H).

[0053] The reaction formula for Example 1: .

[0054] Example 2 - Synthesis of photochromic polyimide material T-2: The basic steps of Example 2 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-2, 0.1 mol, 22.0 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-2.

[0055] 1H NMR (500 MHz, CDCl3) δ 8.42 – 7.79 (m, 2H), 7.73 – 7.09 (m, 4H), 6.94 – 5.79 (m, 4H), 4.07 (ddd, J = 56.2, 32.4, 12.0 Hz, 6H), 2.21 – 1.75 (m,2H), 1.77 – 1.31 (m, 2H), 0.95 (td, J = 27.2, 2.3 Hz, 2H).

[0056] The reaction formula for Example 2: .

[0057] Example 3 - Synthesis of photochromic polyimide material T-3: The basic steps of Example 3 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-3, 0.1 mol, 29.4 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-3.

[0058] 1 H NMR (500 MHz, CDCl3) δ 8.51 – 7.75 (m, 8H), 7.72 – 7.09 (m, 4H), 7.02 – 5.92 (m, 4H), 4.50 – 3.77 (m, 6H), 2.39 – 1.44 (m, 4H), 0.94 (td, J =27.2, 1.8 Hz, 2H).

[0059] The reaction formula for Example 3: .

[0060] Example 4 - Synthesis of photochromic polyimide material T-4: The basic steps of Example 4 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-4, 0.1 mol, 21.8 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-4.

[0061] 1 H NMR (500 MHz, CDCl3) δ 8.51 – 7.79 (m, 4H), 7.70 – 7.00 (m, 4H), 6.94 – 5.79 (m, 4H), 4.52 – 3.64 (m, 6H), 2.35 – 1.82 (m, 2H), 1.78 – 1.23(m, 2H), 0.96 (td, J = 27.1, 2.2 Hz, 2H).

[0062] The reaction formula for Example 4: .

[0063] Example 5 - Synthesis of photochromic polyimide material T-5: The basic steps of Example 5 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-5, 0.1 mol, 32.2 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-5.

[0064] 1 H NMR (500 MHz, CDCl3) δ 8.43 – 7.00 (m, 12H), 6.93 – 5.70 (m, 4H), 4.47 – 3.57 (m, 6H), 2.34 – 1.38 (m, 4H), 0.87 (td, J = 27.1, 1.7 Hz, 2H).

[0065] The reaction formula for Example 5: .

[0066] Example 6 - Synthesis of photochromic polyimide material T-6: The basic steps of Example 6 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-6, 0.1 mol, 35.8 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-6.

[0067] 1 H NMR (500 MHz, CDCl3) δ 8.82 – 7.81 (m, 8H), 7.90 – 7.09 (m, 4H), 7.00 – 5.95 (m, 4H), 4.35 – 3.77 (m, 6H), 2.21 – 1.34 (m, 4H), 1.05 (td, J =27.2, 2.4 Hz, 2H).

[0068] The reaction formula for Example 6: .

[0069] Example 7 - Synthesis of photochromic polyimide material T-7: The basic steps of Example 7 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-7, 0.1 mol, 33.6 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-7.

[0070] 1 H NMR (500 MHz, CDCl3) δ 8.54 – 7.16 (m, 12H), 6.51 (dd, J = 235.5,127.2 Hz, 4H), 4.13 (d, J = 20.0 Hz, 6H), 2.35 – 1.49 (m, 10H), 0.98 (s, 2H).

[0071] The reaction formula for Example 7: .

[0072] Example 8 - Synthesis of photochromic polyimide material T-8: The basic steps of Example 8 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-8, 0.1 mol, 25.0 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-8.

[0073] 1 H NMR (500 MHz, CDCl3) δ 8.49 – 7.07 (m, 6H), 6.67 (dd,J = 47.2, 34.1Hz, 4H), 4.11 (s, 4H), 3.24 (d, J = 65.0 Hz, 6H), 2.56 (s, 2H), 1.81 (dd, J =127.0, 43.1 Hz, 8H), 0.97 (s, 2H).

[0074] The reaction formula for Example 8: .

[0075] Example 9 - Synthesis of photochromic polyimide material T-9: The basic steps of Example 9 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-9, 0.1 mol, 25.0 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-9.

[0076] 1 H NMR (500 MHz, CDCl3) δ 8.49 – 7.77 (m, 2H), 7.70 – 7.05 (m, 4H), 7.02 – 6.23 (m, 4H), 4.85 – 3.70 (m, 4H), 3.58 – 2.34 (m, 9H), 2.23 – 1.09(m, 7H), 0.93 (td, J = 27.2, 1.6 Hz, 2H).

[0077] The reaction formula for Example 9: .

[0078] Example 10 - Synthesis of photochromic polyimide material T-10: The basic steps of Example 10 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-10, 0.1 mol, 24.8 g) were weighed, and 300 mL of anhydrous dimethylformamide (DMF) was added as a solvent. Under nitrogen protection, the reaction mixture was stirred at room temperature for 4 hours to form a polyamic acid intermediate. Then, the reaction system was gradually heated to 200°C and the reaction was continued for 12 hours to dehydrate and cyclize to generate polyimide. After the reaction was completed, the solution was slowly poured into excess methanol to precipitate the polyimide product. The solid was collected by filtration and repeatedly washed with methanol to remove residual solvent and unreacted substances. Finally, the product was dried in a vacuum drying oven to obtain pure polyimide material T-10.

[0079] 1 H NMR (500 MHz, CDCl3) δ 8.53 – 6.94 (m, 6H), 6.98 – 5.66 (m, 6H), 4.32 – 3.93 (m, 4H), 3.77 – 2.72 (m, 8H), 2.23 – 1.36 (m, 4H), 0.93 (td, J =27.2, 1.6 Hz, 2H).

[0080] The reaction formula for Example 10: .

[0081] Example 11 - Synthesis of photochromic polyimide material T-11: The basic steps of Example 11 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-11, 0.1 mol, 30.6 g equivalent) were weighed, and 300 mL of anhydrous dimethylformamide (DMF) was added as a solvent. Under nitrogen protection, the reaction mixture was stirred at room temperature for 4 hours to form a polyamic acid intermediate. Then, the reaction system was gradually heated to 200°C and the reaction was continued for 12 hours to dehydrate and cyclize to generate polyimide. After the reaction was completed, the solution was slowly poured into excess methanol to precipitate the polyimide product. The solid was collected by filtration and repeatedly washed with methanol to remove residual solvent and unreacted substances. Finally, the product was dried in a vacuum drying oven to obtain pure polyimide material T-11.

[0082] 1H NMR (500 MHz, CDCl3) δ 8.42 – 7.13 (m, 6H), 7.13 – 6.04 (m, 4H), 4.60 – 3.83 (m, 4H), 3.42 – 2.15 (m, 8H), 2.15 – 1.01 (m, 16H), 0.94 (td, J =27.1, 1.7 Hz, 2H).

[0083] The reaction formula for Example 11: .

[0084] Example 12 - Synthesis of photochromic polyimide material T-12: The basic steps of Example 12 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out the diamine compound (A-11, 0.1 mol, 49.0 g) and the dianhydride (AN-12, 0.1 mol, 22.4 g), and add 300 mL of anhydrous dimethylformamide (DMF) as solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-12.

[0085] 1 H NMR (500 MHz, CDCl3) δ 8.42 – 7.11 (m, 6H), 7.15 – 6.17 (m, 4H), 4.26 – 3.88 (m, 4H), 3.75 – 2.55 (m, 6H), 2.24 – 1.14 (m, 8H), 0.82 (td, J =27.2, 1.6 Hz, 2H).

[0086] The reaction formula for Example 12: .

[0087] Example 13 - Synthesis of photochromic polyimide material T-13: The basic steps of Example 13 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-13, 0.1 mol, 22.4 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-13.

[0088] 1 H NMR (500 MHz, CDCl3) δ 8.65 – 7.79 (m, 1H), 7.88 – 7.05 (m, 2H), 7.11 – 6.19 (m, 2H), 4.32 – 3.86 (m, 2H), 3.49 – 2.74 (m, 4H), 2.30 – 1.31(m, 3H), 0.94 (td, J = 27.2, 1.6 Hz, 1H).

[0089] The reaction formula for Example 13: .

[0090] Example 14 - Synthesis of photochromic polyimide material T-14: The basic steps of Example 14 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-14, 0.1 mol, 21.2 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-14.

[0091] 1H NMR (500 MHz, CDCl3) δ 8.38 – 6.94 (m, 6H), 6.63 (dd, J = 122.8,51.0 Hz, 4H), 4.06 (d, J = 55.0 Hz, 6H), 2.49 (d, J = 13.5 Hz, 8H), 1.90 (d, J =79.4 Hz, 4H), 0.95 (s, 2H).

[0092] The reaction formula for Example 14: .

[0093] Example 15 - Synthesis of photochromic polyimide material T-15: The basic steps of Example 15 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-15, 0.1 mol, 30.4 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-15.

[0094] 1 H NMR (500 MHz, CDCl3) δ 8.53 – 7.00 (m, 6H), 7.00 – 6.26 (m, 4H), 4.32 – 3.81 (m, 4H), 3.34 – 0.57 (m, 24H).

[0095] The reaction formula for Example 15: .

[0096] Example 16 - Synthesis of photochromic polyimide material T-16: The basic steps of Example 16 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out the diamine compound (A-11, 0.1 mol, 49.0 g) and the dianhydride (AN-16, 0.1 mol, 17.0 g), and add 300 mL of anhydrous dimethylformamide (DMF) as solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-16.

[0097] 1 H NMR (500 MHz, CDCl3) δ 8.62 – 7.75 (m, 2H), 7.83 – 7.00 (m, 5H), 6.72 (dd, J = 143.1, 42.0 Hz, 3H), 5.41 (s, 2H), 4.85 – 3.64 (m, 4H), 3.18 (t, J = 21.9 Hz, 2H), 2.41 – 1.45 (m, 4H), 1.09 (td, J = 27.2, 2.0 Hz, 2H).

[0098] The reaction formula for Example 16: .

[0099] Example 17 - Synthesis of photochromic polyimide material T-17: The basic steps of Example 17 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-17, 0.1 mol, 26.8 g), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-17.

[0100] 1 H NMR (500 MHz, CDCl3) δ 8.62 (s, 4H), 8.40 – 7.11 (m, 6H), 7.04 –6.08 (m, 4H), 4.45 – 3.90 (m, 4H), 3.72 (t, J = 22.0 Hz, 2H), 2.28 – 1.42 (m,4H), 0.97 (td, J = 27.2, 1.7 Hz, 2H).

[0101] The reaction formula for Example 17: .

[0102] Example 18 - Synthesis of photochromic polyimide material T-18: The basic steps of Example 18 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-1, 0.1 mol, 31.0 g) were weighed, and 300 mL of anhydrous dimethylformamide (DMF) was added as a solvent. Under nitrogen protection, the reaction mixture was stirred at room temperature for 4 hours to form a polyamic acid intermediate. Then, the reaction system was gradually heated to 200°C and the reaction was continued for 12 hours to dehydrate and cyclize to generate polyimide. After the reaction was completed, the solution was slowly poured into excess methanol to precipitate the polyimide product. The solid was collected by filtration and repeatedly washed with methanol to remove residual solvent and unreacted substances. Finally, the product was dried in a vacuum drying oven to obtain pure polyimide material T-18.

[0103] 1 H NMR (500 MHz, CDCl3) δ 8.42 – 7.05 (m, 12H), 6.93 – 5.90 (m, 4H), 4.32 – 3.73 (m, 6H), 2.32 – 1.84 (m, 2H), 1.82 – 1.40 (m, 2H), 1.06 (td, J =27.2, 2.4 Hz, 2H).

[0104] The reaction formula for Example 18: .

[0105] Example 19 - Synthesis of photochromic polyimide material T-19: The basic steps of Example 19 are the same as steps S1-S7 of Example 1, except for step S8; S8: In a dry three-necked flask, weigh out a diamine compound (A-11, 0.1 mol, 49.0 g) and a dianhydride (AN-19, 0.1 mol, 35.2 g equivalent), and add 300 mL of anhydrous dimethylformamide (DMF) as a solvent. Under nitrogen protection, stir the reaction mixture at room temperature for 4 hours to form a polyamic acid intermediate. Then, gradually heat the reaction system to 200°C and continue the reaction for 12 hours to dehydrate and cyclize to form polyimide. After the reaction is complete, slowly pour the solution into excess methanol to precipitate the polyimide product. Collect the solid using filtration and wash repeatedly with methanol to remove residual solvent and unreacted substances. Finally, dry the product in a vacuum drying oven to obtain pure polyimide material T-19.

[0106] 1 H NMR (500 MHz, CDCl3) δ 8.54 – 7.72 (m, 8H), 7.75 – 7.00 (m, 4H), 6.70 (d, J = 21.8 Hz, 1H), 6.33 (d, J = 21.8 Hz, 1H), 5.85 (d, J = 14.5 Hz, 2H), 4.35 – 3.81 (m, 6H), 2.17 – 1.81 (m, 2H), 1.52 (ddtd, J = 26.7, 20.8, 18.5,2.3 Hz, 2H), 1.08 – 0.84 (m, 2H), 0.66 (s, 6H).

[0107] The reaction formula for Example 19: .

[0108] The performance tests were performed on T1-T19 corresponding to Examples 1-19, and the results are shown in Table 1: ① Photochromic performance test: To test the photochromic properties of the material, a polyimide film was exposed to a UV light source (wavelength around 350 nm), and its color change process was observed. The absorption peak changes at different time points were recorded using a UV-Vis spectrometer, and the color change depth (ΔOD) and response time (coloring time and fading time) of the material were measured. Repeated light-dark cycles were performed to test the retention rate of the photochromic properties after multiple cycles, evaluating its cyclic stability.

[0109] ② Thermal stability test: The thermal stability of polyimide materials was tested using a thermogravimetric analyzer (TGA). Material samples were heated from room temperature to 600°C, and the thermal decomposition temperature (Td) was recorded. The glass transition temperature (Tg) was measured using differential scanning calorimetry (DSC) to assess the material's adaptability to high-temperature environments.

[0110] ③ Mechanical performance testing: Tensile testing was performed on polyimide films using a tensile testing machine to measure their tensile strength and elongation at break. The tensile speed was set to 5 mm / min, and the film was stretched until fracture. Mechanical property testing ensured the structural integrity of the material in optical devices and smart coating applications.

[0111] ④ Weather resistance test: The thin film samples were subjected to accelerated aging tests in an environment with ultraviolet light, 85% humidity, and 60°C for 1000 hours. The photochromic properties of the material were periodically tested, and the changes in photochromic properties at multiple time points were measured to observe the color retention rate and color change effect, thereby evaluating its photochromic performance retention rate in long-term outdoor applications.

[0112] illustrate: Examples 1-19 all exhibited excellent thermal stability at high temperatures and maintained high photochromic stability under prolonged ultraviolet light irradiation. Mechanical property tests highlighted the material's tensile strength and flexibility, making it particularly suitable for applications requiring durability. Weather resistance tests showed that the material maintained good photosensitivity under ultraviolet light, high temperature, and high humidity conditions, making it suitable for applications with long-term outdoor exposure.

[0113] 1. Regarding its highly efficient photochromic properties, the coloring time is 2-4 seconds, and the fading time is 6-10 seconds, indicating that it can rapidly respond and exhibit color change under ultraviolet light irradiation, and recover to a colorless state through visible light or heating, demonstrating highly efficient photochromic characteristics. This material has a faster light response speed, higher stability, and the photochromic process is unaffected by environmental factors, exhibiting good recyclability. This design solves the problems of weakened light response and reduced color change depth in traditional naphthol-pyran materials, making it particularly suitable for applications such as smart coatings and optical devices.

[0114] 2. The decomposition temperature is 475-505℃, and the thermal glutaraldehyde (Tg) is 220-245℃. These results indicate that the material is suitable for high-temperature applications. The polyimide matrix imparts higher thermal decomposition temperature and mechanical strength to the material, giving it superior durability and environmental adaptability.

[0115] 3. Regarding the improvement of mechanical properties and durability, the tensile strength is 84-95 MPa and the elongation at break is 6-10%. After introducing the polyimide matrix, the material shows a significant improvement in mechanical properties, especially in tensile strength.

[0116] 4. Regarding weather resistance, the photochromic retention rate is 87-93%. This characteristic enables the material to maintain its functional integrity during long-term use, demonstrating its resistance to ultraviolet aging and its long-term stability in harsh environments. It is particularly suitable for applications requiring high mechanical strength, such as intelligent building coatings and exterior coatings for vehicles.

[0117] In summary, this invention introduces a photochromic unit into the polyimide structure, developing a novel polyimide material with excellent photochromic properties. This material responds rapidly to ultraviolet light irradiation and exhibits a color change, returning to a colorless state upon exposure to visible light or heating. Simultaneously, the polyimide matrix provides high mechanical strength, thermal stability, and chemical resistance, enabling the material to maintain stable color-changing ability through multiple light-induced color-changing cycles. Furthermore, the material exhibits significantly improved weather resistance, making it suitable for outdoor and harsh environments, expanding its application prospects in fields such as smart coatings, optical devices, and sensors. This invention overcomes the limitations of existing technologies in terms of light response, durability, and processing adaptability.

[0118] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A photochromic polyimide material, characterized in that, Its chemical structural formula is: ; It has a diimide structure, where R represents a divalent group that connects two imide groups.

2. The photochromic polyimide material according to claim 1, characterized in that, The diimide structure is selected from one of the following structural formulas: 。 3. A method for preparing a photochromic polyimide material, characterized in that, Includes the following steps: The diamine compound and dianhydride were dissolved in a solvent, stirred, and a protective gas was introduced. The reaction was carried out at room temperature to obtain a polyamic acid intermediate. The reaction system was gradually heated to 150-200℃ and the reaction was continued to generate polyimide through dehydration and cyclization. After the reaction is complete, the polyimide product precipitates out, the solid is collected by filtration, and after washing and drying, the polyimide material is obtained. The chemical structural formula of the diamine compound is: ; The chemical structural formula of dianhydride is: R represents a divalent group that connects two imide groups; The chemical structural formula of polyimide material is: ; It has a diimide structure, where R represents a divalent group that connects two imide groups.

4. The method for preparing a photochromic polyimide material according to claim 3, characterized in that, The preparation method of the diamine compound includes the following steps: S1-1: Compounds A-1 and A-2 are dissolved in a solvent, stirred, and heated to 100-120℃ under a protective atmosphere; after cooling to room temperature, the solvent is removed, and the mixture is purified to obtain intermediate A-3; compound A-1 is... Compound A-2 is sodium acetylene; intermediate A-3 is... ; S1-2: Dissolve intermediate A-3 in a flux, add naphthol as compound A-4, add sodium hydroxide, and react with stirring until the nucleophilic substitution reaction is complete; after the reaction, separate the organic phase, dry, filter, and remove the solvent to obtain compound A-5; compound A-5 is... ; S1-3: Dissolve compound A-5 in concentrated sulfuric acid, add concentrated nitric acid dropwise, control the reaction temperature at 0-5℃, and stir the reaction in an ice bath; after the reaction is complete, slowly pour the reaction mixture into ice water, filter and collect the precipitate, wash the precipitate to obtain intermediate A-6; intermediate A-6 is ; S1-4: Dissolve intermediate A-6 in a solvent, add a reducing agent and concentrated hydrochloric acid, and react at 30-90℃ with stirring, maintaining an acidic environment during the reaction; after the reaction is complete, remove the reducing agent, concentrate the filtrate to dryness, dissolve the concentrate in water and adjust to alkalinity, collect the precipitated product by vacuum filtration to obtain intermediate A-7; intermediate A-7 is ; S1-5: Dissolve intermediate A-7 in acid, and slowly add sodium nitrite solution at 0-5℃ to generate a diazonium salt; after the reaction is complete, add ice water and stir; add excess water, filter the product, collect the product, and wash with water until neutral to obtain intermediate A-8; intermediate A-8 is... ; S1-6: Dissolve intermediate A-8 in solvent by stirring, add Boc anhydride-protected bromoalkylamine derivative A-9 and triethylamine, and stir to react; after the reaction is complete, wash the organic phase with water, separate the organic layer, dry and purify to obtain compound A-10; A-9, a bromoalkylamine derivative, is Intermediate A-10 is: ; S1-7: Dissolve intermediate A-10 in a solvent, add trifluoroacetic acid, remove the Boc protecting group, and generate a diamine compound.

5. A photoinitiator, characterized in that, include: Photochromic polyimide materials; The photochromic polyimide material is a photochromic polyimide material according to any one of claims 1-3, or is prepared by the preparation method of a photochromic polyimide material according to claim 4.

6. A coating, characterized in that, Its raw materials include: photochromic polyimide material; The photochromic polyimide material is a photochromic polyimide material according to any one of claims 1-3, or is prepared by the preparation method of a photochromic polyimide material according to claim 4.

7. A coating, characterized in that, Its raw materials include: photochromic polyimide material; The photochromic polyimide material is a photochromic polyimide material according to any one of claims 1-3, or is prepared by the preparation method of a photochromic polyimide material according to claim 4.

8. An optical device, characterized in that, Use photochromic polyimide material; The photochromic polyimide material is a photochromic polyimide material according to any one of claims 1-3, or is prepared by the preparation method of a photochromic polyimide material according to claim 4.

9. An application of a polymer in optical devices, characterized in that, The polymer is a photochromic polyimide material according to any one of claims 1-3, or is prepared by the preparation method of a photochromic polyimide material according to claim 4.

10. The application of a polymer in the preparation of smart coatings, characterized in that, The polymer is a photochromic polyimide material according to any one of claims 1-3, or is prepared by the preparation method of a photochromic polyimide material according to claim 4.

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