Reversible photochromic compound and preparation method and application thereof

Abstract

A reversible photochromic compound, its preparation method, and its application belong to the field of reversible photochromic materials. The present invention aims to solve the problems of existing photochromic materials, such as slow response speed, unstable color change performance, short lifespan, high preparation cost, complex synthesis, and aggregation-induced quenching. An intermediate, a benzothiophene derivative, and potassium carbonate are dissolved in a mixed solution of tetrahydrofuran / water, and then tetrakis(triphenylphosphine)palladium is added and condensed and refluxed. After the reaction is completed, vacuum distillation, extraction, drying, and column chromatography purification are performed to obtain a reversible photochromic compound; the reversible photochromic compound is used to prepare a reversible photochromic material. The present invention is used for a reversible photochromic compound, its preparation, and application.

Description

Technical Field

[0001] The invention belongs to the field of reversible photochromic materials. Background Art

[0002] In the rapidly developing digital age, information is exchanged through various channels, and the risk of information leakage has increased exponentially. Information protection has become a current research hotspot, and more advanced and secure anti-counterfeiting technologies are necessary to encrypt and protect important information such as banknotes, identity passports, and confidential documents. Therefore, researchers have created a series of anti-counterfeiting materials with various stimulus-responsive properties. Among them, photoresponsive functional materials have the advantages of simple processing, high yield, and precise design, which can realize encrypted storage and secure access of information.

[0003] Cellulose is a natural polymer found widely in plant cell walls and is one of the most abundant organic substances on Earth. It exists as microfibrils within plant cell walls, providing structural support for plants. Due to its renewability and independence from fossil fuels, the production of valuable industrial materials from bioresources has attracted significant attention in recent years. As one of the cheapest and most widely available raw materials on Earth, cellulose can be used to synthesize environmentally friendly, green, and sustainable functional materials. Furthermore, as a colorless and odorless biopolymer, cellulose offers unique advantages, including high biocompatibility, renewable sustainability, easy degradation, a polyhydroxy structure that is easily chemically modified, heat resistance, and strong adsorption capacity. Cellulose can be modified into a variety of useful materials, and chemical modification in smart fluorescent materials offers even more potential applications. Furthermore, due to cellulose's excellent plasticity, fluorescent cellulose materials have been prepared into films, fibers, paper strips, carbon dots, hydrogels, and solutions. These materials exhibit fluorescent responses to toxic metals and anions, pH, and common organic solvents, and can be used for fluorescent printing and coatings. These properties give cellulose significant advantages in anti-counterfeiting applications.

[0004] Photochromic materials, which change color in response to light, hold broad application prospects in areas such as smart glasses, smart windows, and photosensitizers. However, current photochromic materials still suffer from a number of technical drawbacks that not only limit their performance in practical applications but also hinder their further development and application. First, current photochromic materials suffer from limited response speed. Some materials exhibit slow color change rates, failing to meet real-time requirements, such as the speed required to rapidly adjust the color of smart glasses lenses. Furthermore, some materials may experience color stability issues after prolonged use, resulting in uneven or distorted color changes, impacting user experience and material reliability. Furthermore, the durability of photochromic materials is also a concern. Prolonged light exposure or frequent color-changing operations can cause material performance degradation or failure, reducing their lifespan and reliability, and increasing maintenance and replacement costs. Furthermore, the relatively high cost of photochromic materials, primarily due to the material's inherent cost and the complexity of their preparation and processing, has limited the widespread adoption and promotion of photochromic technology for large-scale applications, particularly for cost-effective consumer products. Furthermore, most photochromic switches often suffer from aggregation-induced quenching, limiting their application in various fields. These issues collectively hinder the further development and application of photochromic technology. Therefore, addressing these technical limitations and improving the performance and reliability of photochromic materials is one of the key directions for the current development of photochromic technology. Summary of the Invention

[0005] The present invention aims to solve the problems of slow response speed, unstable color change performance, short life, high preparation cost, complex synthesis and aggregation-induced quenching of existing photochromic materials, and thus provide a reversible photochromic compound and its preparation method and application.

[0006] Reversible photochromic compound, the structural formula of the reversible photochromic compound is

[0007] The preparation method of the reversible photochromic compound is carried out according to the following steps:

[0008] The intermediate, the benzothiophene derivative, and potassium carbonate are dissolved in a mixed solution of tetrahydrofuran / water, and then, under nitrogen protection, tetrakis(triphenylphosphine)palladium is added, and the reaction is carried out under condensation reflux for 17 hours to 48 hours under a nitrogen atmosphere at a temperature of 60° C. to 90° C. After the reaction is completed, the volatile solvent is removed by distillation under reduced pressure, and then the organic phase is extracted three times with ethyl acetate and deionized water. The organic phase is dried with anhydrous magnesium sulfate, and finally, the mixture is purified by column chromatography using a mixed solution of dichloromethane / petroleum ether as an eluent to obtain a reversible photochromic compound.

[0009] The structural formula of the intermediate is The benzothiophene derivative is benzothiophene-3-boric acid or 3-bromobenzothiophene.

[0010] The invention relates to an application of a reversible photochromic compound, which is used for the preparation of a reversible photochromic material.

[0011] The beneficial effects of the present invention are:

[0012] First, the present invention utilizes an organic coupling reaction, resulting in a simple material synthesis route and low production cost. Based on the reversible photochromic properties and combined with the concept of aggregation-induced emission, a new compound with aggregation-induced emission properties that can alternately respond to ultraviolet and visible light was constructed, and single crystals were successfully grown.

[0013] 2. The present invention is based on the reversible change characteristics of the color-changing filter paper material in response to light, which can realize the reversible disappearance and recovery of information after reading, improve fatigue resistance and can be reused when combined with paper, which is green and environmentally friendly.

[0014] Third, this invention cleverly addresses the issue of photochromic material photooxidation by using a solid-state matrix coating method. It has produced photochromic PMMA films, cellulose films, and cellulose composite films. A series of optical characterizations demonstrate that the composite films outperform the previous two films and offer a long service life.

[0015] Fourth, the present invention realizes a non-contact light-responsive anti-counterfeiting method based on the photochromic properties of different irradiated light. The photochromic molecules are simple to synthesize, and the color change stability of the material is excellent. This makes it have the advantages of fast response, pollution-free encoded information, and excellent reversibility compared to contact-based chemical anti-counterfeiting methods.

[0016] 5. The present invention uses three materials to make different photochromic films. Through the difference in recovery time of the response to visible light after color change, it can add time-delayed information protection to the traditional anti-counterfeiting field level and realize the anti-counterfeiting strategy of delayed encryption.

[0017] Figures in the specification

[0018] Figure 1 This is the H NMR spectrum of the 2PBS compound prepared in Example 1;

[0019] Figure 2 This is a high-resolution mass spectrum of the 2PBS compound prepared in Example 1;

[0020] Figure 3 This is the H NMR spectrum of the HPBS compound prepared in Example 2;

[0021] Figure 4This is a high-resolution mass spectrum of the HPBS compound prepared in Example 2;

[0022] Figure 5 This is the H NMR spectrum of the 2PSF compound prepared in Example 3;

[0023] Figure 6 This is a high-resolution mass spectrum of the 2PSF compound prepared in Example 3;

[0024] Figure 7 Schematic diagram of the photochemical phenomena of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 in different states;

[0025] Figure 8 Schematic diagram of the molecular structure changes of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 under ultraviolet light (365 nm);

[0026] Figure 9 The fluorescence spectra of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 under continuous ultraviolet light irradiation in tetrahydrofuran change with time;

[0027] Figure 10 UV-visible absorption spectra of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 under continuous UV irradiation in tetrahydrofuran as a function of time;

[0028] Figure 11 The time-resolved fluorescence decay curves of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3;

[0029] Figure 12 Fluorescence spectra of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 at different water contents in tetrahydrofuran / water solutions and dot-line graphs of fluorescence intensity;

[0030] Figure 13 Photochromic cycle test graphs of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3, which were alternately exposed to ultraviolet light (365 nm) and visible light in a tetrahydrofuran solution;

[0031] Figure 14 This is a diagram of the light-controlled patterning application of the reversible photochromic filter paper prepared in Example 4; in the figure, the initial filter paper does not show a pattern;

[0032] Figure 15Photochromic cycling test graph of the 2PSF@PMMA film prepared in Example 5 and the 2PSF@HPC film prepared in Example 6, which were alternately exposed to ultraviolet light and visible light;

[0033] Figure 16 UV-visible absorption spectra of the 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 under continuous UV irradiation over time;

[0034] Figure 17 Photochromic cycling test graph of 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7, alternately exposed to ultraviolet light (365 nm) and visible light;

[0035] Figure 18 The relationship curves between the normalized absorbance value and the recovery time of the 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 are shown;

[0036] Figure 19 The QR code labels based on the photochromic films with different isomerization rates prepared in Example 7;

[0037] Figure 20 Single crystal structure diagrams of 2PBS, HPBS, and 2PSF. DETAILED DESCRIPTION

[0038] Specific embodiment 1: This embodiment is a reversible photochromic compound, the structural formula of the reversible photochromic compound is

[0039] This specific embodiment prepares photochromic compounds with aggregation-induced luminescence, achieving color changes in single molecules under alternating ultraviolet and visible light. Subsequently, these compounds were combined with filter paper, polymethyl methacrylate, and hydroxypropyl cellulose to create monolayer and composite films. This enhanced the molecules' antioxidant properties, enabling reversible photochromism in multicolored cellulose and research into anti-counterfeiting strategies.

[0040] This specific embodiment combines traditional photochromic molecules with the concept of aggregation-induced emission (AIE), achieving color changes under alternating ultraviolet and visible light, as well as photochromic molecules exhibiting the AIE effect. The design and synthesis are simple, the materials are stable, and their applications are wide, providing a new strategy for light-controlled information encryption and protection. Applications include photolithographic patterning, optical anti-counterfeiting, and the preparation of multicolor cellulose composite films to improve their fatigue resistance.

[0041] The beneficial effects of this embodiment are:

[0042] First, this embodiment utilizes an organic coupling reaction, resulting in a simple material synthesis route and low production cost. Based on the reversible photochromic properties and combined with the concept of aggregation-induced emission, a new compound with aggregation-induced emission properties that can alternately respond to ultraviolet and visible light was constructed, and single crystals were successfully grown.

[0043] 2. This embodiment is based on the reversible change characteristics of the color-changing filter paper material in response to light, which can achieve reversible disappearance and recovery of information after reading, improve fatigue resistance, and can be reused when combined with paper, which is green and environmentally friendly.

[0044] Third, this embodiment cleverly addresses the issue of photochromic material photooxidation by using a solid-state matrix coating method. Photochromic PMMA films, cellulose films, and cellulose composite films were fabricated. A series of optical characterizations demonstrated that the composite films outperformed the previous two films and exhibited a long service life.

[0045] Fourth, this embodiment realizes a non-contact light-responsive anti-counterfeiting method based on the photochromic properties of different irradiated light. The photochromic molecules are simple to synthesize, and the color change stability of the material is excellent. This makes it have the advantages of fast response, pollution-free encoded information, and excellent reversibility compared to contact-based chemical anti-counterfeiting methods.

[0046] 5. This embodiment uses three materials to make different photochromic films. By taking advantage of the difference in recovery time of the response to visible light after color change, it can add time-delayed information protection to the traditional anti-counterfeiting field and implement a delayed encryption anti-counterfeiting strategy.

[0047] Specific embodiment 2: The preparation method of the reversible photochromic compound of this embodiment is carried out according to the following steps:

[0048] The intermediate, the benzothiophene derivative, and potassium carbonate are dissolved in a mixed solution of tetrahydrofuran / water, and then, under nitrogen protection, tetrakis(triphenylphosphine)palladium is added, and the reaction is carried out under condensation reflux for 17 hours to 48 hours under a nitrogen atmosphere at a temperature of 60° C. to 90° C. After the reaction is completed, the volatile solvent is removed by distillation under reduced pressure, and then the organic phase is extracted three times with ethyl acetate and deionized water. The organic phase is dried with anhydrous magnesium sulfate, and finally, the mixture is purified by column chromatography using a mixed solution of dichloromethane / petroleum ether as an eluent to obtain a reversible photochromic compound.

[0049] The structural formula of the intermediate is The benzothiophene derivative is benzothiophene-3-boric acid or 3-bromobenzothiophene.

[0050] Specific embodiment three: This embodiment differs from specific embodiment two in that: the molar ratio of the intermediate to the benzothiophene derivative is 1:(2-2.6); the molar ratio of the intermediate to potassium carbonate is 1:(2.5-3.5); the molar ratio of the intermediate to tetrakis(triphenylphosphine)palladium is 1:(0.05-0.1); the volume ratio of the molar amount of the intermediate to the tetrahydrofuran / water mixed solution is 1 mmol:(25-35) mL; the volume ratio of tetrahydrofuran to water in the tetrahydrofuran / water mixed solution is 1:(0.35-0.45); and the volume ratio of dichloromethane to petroleum ether in the dichloromethane / petroleum ether mixture is 1:(4-12). Other aspects are the same as specific embodiment two.

[0051] Specific embodiment 4: The application of the reversible photochromic compound in this embodiment is used for the preparation of reversible photochromic materials.

[0052] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the reversible photochromic material changes color under the alternating action of ultraviolet light and visible light. Other aspects are the same as specific embodiment 4.

[0053] Specific Embodiment 6: This embodiment differs from either Specific Embodiment 4 or 5 in that the reversibly photochromic material is a reversibly photochromic filter paper, a reversibly photochromic polymethyl methacrylate film, a reversibly photochromic hydroxypropyl cellulose film, or a reversibly photochromic cellulose composite film. Otherwise, this embodiment is the same as Specific Embodiment 4 or 5.

[0054] Specific embodiment 7: This embodiment differs from any one of specific embodiments 4 to 6 in that: when the reversible photochromic material is a reversible photochromic filter paper, it is specifically prepared according to the following steps:

[0055] The reversible photochromic compound is dissolved in dichloromethane to obtain a transparent solution, and the filter paper is immersed in the transparent solution at room temperature for 6 hours to 12 hours, and then dried to obtain the reversible photochromic filter paper; the mass ratio of the filter paper size to the reversible photochromic compound in the transparent solution is 1 cm 2 : (0.5-1) mg; the concentration of the reversible photochromic compound in the transparent solution is 1 mol / L-2 mol / L. Other aspects are the same as those of the fourth to sixth embodiments.

[0056] Specific embodiment eight: This embodiment differs from any one of specific embodiments four to seven in that when the reversible photochromic material is a reversible photochromic polymethyl methacrylate film, it is prepared according to the following steps:

[0057] Dissolve polymethyl methacrylate and a reversible photochromic compound in dichloromethane to obtain a transparent solution; pour the transparent solution into a mold and allow it to evaporate and dry naturally at room temperature to obtain a reversibly photochromic polymethyl methacrylate film; the mass ratio of the polymethyl methacrylate to the reversible photochromic compound is 1:(0.05-0.2); and the volume ratio of the polymethyl methacrylate to dichloromethane is 1 mg:(0.5-1) mL. Other steps are the same as those in Specific Embodiments 4 to 7.

[0058] Specific embodiment 9: This embodiment differs from any one of specific embodiments 4 to 8 in that when the reversible photochromic material is a reversible photochromic hydroxypropyl cellulose film, it is prepared according to the following steps:

[0059] A reversible photochromic compound is dissolved in dimethyl sulfoxide to obtain a transparent solution; hydroxypropyl cellulose is added to distilled water to obtain a hydroxypropyl cellulose aqueous solution; the transparent solution and the hydroxypropyl cellulose aqueous solution are mixed to obtain a mixed solution; the mixed solution is poured into a mold and heated and dried at a temperature of 60°C to 65°C to obtain a reversibly photochromic hydroxypropyl cellulose film; the mass ratio of the reversible photochromic compound to dimethyl sulfoxide is 1 mg:(0.05-0.2) mL; the mass ratio of the hydroxypropyl cellulose to distilled water is 1 mg:(0.5-1) mL; and the mass ratio of the hydroxypropyl cellulose to the reversible photochromic compound in the mixed solution is 1:(0.05-0.25). Other aspects are the same as those of Specific Embodiments 4 to 8.

[0060] Specific embodiment 10: This embodiment differs from any one of specific embodiments 4 to 9 in that when the reversible photochromic material is a reversible photochromic cellulose composite film, it is prepared according to the following steps:

[0061] The reversible photochromic compound is dissolved in dimethyl sulfoxide to obtain a transparent solution; hydroxypropyl cellulose is added to distilled water to obtain a hydroxypropyl cellulose aqueous solution; the transparent solution and the hydroxypropyl cellulose aqueous solution are mixed to obtain a mixed solution; the mixed solution is poured into a mold covered with a PMMA film, heated and dried at a temperature of 60°C to 65°C, and then the PMMA solution is poured onto the surface, and heated and dried again at a temperature of 60°C to 65°C to form a PMMA / cellulose / PMMA structure, thereby obtaining a reversible photochromic cellulose composite film; The mass ratio of the reversible photochromic compound to dimethyl sulfoxide is 1 mg:(0.05-0.2) mL; the mass ratio of the hydroxypropyl cellulose to distilled water is 1 mg:(0.5-1) mL; the mass ratio of the hydroxypropyl cellulose to the reversible photochromic compound in the mixed solution is 1:(0.05-0.25); the thickness of the single-sided PMMA film is 0.1 mm to 0.5 mm; and the mass ratio of the single-sided PMMA to the reversible photochromic compound in the reversible photochromic cellulose composite film is 1:(0.1-0.2). Other aspects are the same as those of Specific Embodiments 4 to 9.

[0062] The following examples are used to verify the beneficial effects of the present invention:

[0063] Example 1:

[0064] The preparation method of the reversible photochromic compound is carried out according to the following steps:

[0065] 1. Preparation of intermediates:

[0066] Benzophenone (0.912 g, 5 mmol), carbon tetrabromide (3.318 g, 10 mmol) and triphenylphosphine (5.259 g, 20 mmol) were added to 50 mL of anhydrous toluene under a nitrogen atmosphere and a rotation speed of 1000 rpm. The reaction system was then heated to 140° C. and stirred for 4 d under a nitrogen atmosphere at a rotation speed of 600 rpm and a temperature of 140° C. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filtrate was dried to obtain a black oil. The product was then purified by column chromatography using petroleum ether as an eluent to obtain a yellow liquid, which was the intermediate, with a yield of 40%.

[0067] The structural formula of the intermediate is It is named as 2PBS intermediate;

[0068] 2. The intermediate (1.05 g, 0.6 mmol), benzothiophene-3-boric acid (1.3 g, 1.44 mmol) and potassium carbonate (1.25 g, 1.8 mmol) were dissolved in 20 mL of a mixed solution of tetrahydrofuran / water (V / V=7:3), and then tetrakis(triphenylphosphine)palladium (200 mg, 0.03 mmol) was added under nitrogen protection. The mixture was refluxed under a nitrogen atmosphere at 85° C. for 48 h. After the reaction was completed, the volatile solvent was removed by distillation under reduced pressure, and the mixture was extracted three times with ethyl acetate and deionized water. The organic phase was dried over anhydrous magnesium sulfate, and finally purified by column chromatography using a mixture of dichloromethane / petroleum ether as an eluent to obtain a reversible photochromic compound with a yield of 35%.

[0069] The structural formula of the reversible photochromic compound is It was named as 2PBS compound;

[0070] The volume ratio of dichloromethane to petroleum ether in the dichloromethane / petroleum ether mixture is 1:5.

[0071] The reaction equation of step one is as follows:

[0072]

[0073] The reaction equation of step 2 is as follows:

[0074]

[0075] Example 2:

[0076] The preparation method of the reversible photochromic compound is carried out according to the following steps:

[0077] 1. Preparation of intermediates:

[0078] Under a nitrogen atmosphere and a rotation speed of 800 rpm, carbon tetrabromide (3.318 g, 10 mmol) and triphenylphosphine (5.259 g, 20 mmol) were respectively added dropwise to 30 mL of anhydrous dichloromethane to obtain a carbon tetrabromide solution and a triphenylphosphine solution; under a nitrogen atmosphere and a rotation speed of 600 rpm, the carbon tetrabromide solution was added dropwise to the triphenylphosphine solution, stirred for 10 minutes, and then benzaldehyde (0.531 g, 5 mmol) was added. The system was protected by nitrogen and sealed, stirred at room temperature for 2 hours, and the filtrate was filtered and dried to obtain a black oil; and then petroleum ether was used as an eluent for column chromatography purification to obtain a transparent liquid, which was the intermediate, with a yield of 76%;

[0079] The structural formula of the intermediate is It is named as HPBS intermediate;

[0080] 2. The intermediate (1.05 g, 1 mmol), benzothiophene-3-boric acid (1.7 g, 2.4 mmol) and potassium carbonate (1.66 g, 3 mmol) were dissolved in 30 mL of a mixed solution of tetrahydrofuran / water (V / V=7:3), and then tetrakis(triphenylphosphine)palladium (232 mg, 0.05 mmol) was added under nitrogen protection. The reaction was refluxed under a nitrogen atmosphere at 85° C. for 48 h. After the reaction was completed, the volatile solvent was removed by distillation under reduced pressure, and the mixture was extracted three times with ethyl acetate and deionized water. The organic phase was dried over anhydrous magnesium sulfate, and finally purified by column chromatography using a mixture of dichloromethane / petroleum ether as an eluent to obtain a reversible photochromic compound with a yield of 56%.

[0081] The structural formula of the reversible photochromic compound is It is named as HPBS compound;

[0082] The volume ratio of dichloromethane to petroleum ether in the dichloromethane / petroleum ether mixture is 1:12.

[0083] The reaction equation of step one is as follows:

[0084]

[0085] The reaction equation of step 2 is as follows:

[0086]

[0087] Example 3:

[0088] The preparation method of the reversible photochromic compound is carried out according to the following steps:

[0089] 1. Preparation of intermediates:

[0090] Diboric acid pinacol ester (4 g, 4 mmol) and tetrakis(triphenylphosphine)platinum (90 mg, 0.1 mmol) were placed in a reaction flask, and diphenylacetylene (1.24 g, 7 mmol) and 50 mL of N,N-dimethylformamide were added under a nitrogen atmosphere. The reaction was then carried out at 90°C for 24 h. After completion of the reaction, the mixture was cooled to room temperature and extracted three times with ethyl acetate and deionized water. The organic phase was then dried over anhydrous magnesium sulfate and dried under reduced pressure to obtain a crude product. The product was then washed several times with anhydrous ethanol to obtain a white solid, which was the intermediate. The yield was 42%.

[0091] The structural formula of the intermediate is It is named as 2PSF intermediate;

[0092] 2. The intermediate (1.3 g, 3 mmol), 3-bromobenzothiophene (1.5 g, 7.2 mmol) and potassium carbonate (1.3 g, 9 mmol) were dissolved in 90 mL of a mixed solution of tetrahydrofuran / water (V / V=7:3), and then tetrakis(triphenylphosphine)palladium (170 mg, 0.15 mmol) was added under nitrogen protection. The reaction was refluxed under a nitrogen atmosphere at 85° C. for 48 h. After the reaction was completed, the volatile solvent was removed by distillation under reduced pressure, and then extracted three times with ethyl acetate and deionized water. The organic phase was dried over anhydrous magnesium sulfate, and finally purified by column chromatography using a mixture of dichloromethane / petroleum ether as an eluent to obtain a reversible photochromic compound with a yield of 65%.

[0093] The structural formula of the reversible photochromic compound is It is named as 2PSF compound;

[0094] The volume ratio of dichloromethane to petroleum ether in the dichloromethane / petroleum ether mixture is 1:4.

[0095] The reaction equation of step one is as follows:

[0096]

[0097] The reaction equation of step 2 is as follows:

[0098]

[0099] Example 4:

[0100] The reversible photochromic compound (2PSF compound) prepared in Example 3 was used to prepare reversible photochromic filter paper, specifically by the following steps:

[0101] 8 mg (0.018 mol) of the reversible photochromic compound (2PSF compound) prepared in Example 3 was dissolved in 15 mL of dichloromethane to obtain a transparent solution. A 4 cm × 4 cm filter paper was immersed in the transparent solution at room temperature for 8 h and then dried to obtain a reversible photochromic filter paper.

[0102] Example 5:

[0103] Reversible photochromic polymethyl methacrylate films were prepared using the reversible photochromic compounds (2PBS compound, HPBS compound, 2PSF compound) prepared in Examples 1 to 3, respectively. Specifically, the preparation was carried out according to the following steps:

[0104] 15 mg of polymethyl methacrylate and 1.8 mg of a reversible photochromic compound were dissolved in 10 mL of dichloromethane to obtain a transparent solution. The transparent solution was poured into a mold and naturally evaporated and dried at room temperature to obtain reversible photochromic polymethyl methacrylate films, which were named 2PBS@PMMA film, HPBS@PMMA film, and 2PSF@PMMA film, respectively.

[0105] Example 6:

[0106] Reversible photochromic hydroxypropyl cellulose films were prepared using the reversible photochromic compounds (2PBS compound, HPBS compound, 2PSF compound) prepared in Examples 1 to 3, respectively. Specifically, the preparation was carried out according to the following steps:

[0107] 10 mg of the reversible photochromic compound was dissolved in 2 mL of dimethyl sulfoxide to obtain a transparent solution; 50 mg of hydroxypropyl cellulose was added to 25 mL of distilled water to obtain a hydroxypropyl cellulose aqueous solution; 1 mL of the transparent solution was mixed with 10 mL of the hydroxypropyl cellulose aqueous solution to obtain a mixed solution; the mixed solution was poured into a mold, heated and dried at 60°C to obtain reversible photochromic hydroxypropyl cellulose films, which were named 2PBS@HPC, HPBS@HPC, and 2PSF@HPC films, respectively.

[0108] Example 7:

[0109] Reversible photochromic cellulose composite films were prepared using the reversible photochromic compounds (2PBS compound, HPBS compound, 2PSF compound) prepared in Examples 1 to 3, respectively. Specifically, the preparation was carried out according to the following steps:

[0110] 10 mg of a reversible photochromic compound was dissolved in 2 mL of dimethyl sulfoxide to obtain a transparent solution; 50 mg of hydroxypropyl cellulose was added to 25 mL of distilled water to obtain a hydroxypropyl cellulose aqueous solution; 1 mL of the transparent solution was mixed with 10 mL of the hydroxypropyl cellulose aqueous solution to obtain a mixed solution; the mixed solution was poured into a mold covered with a PMMA film, heated and dried at 60°C, and then the PMMA solution was poured onto the surface, and heated and dried again at 60°C to form a PMMA / cellulose / PMMA structure to obtain reversible photochromic cellulose composite films, respectively named 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA; the thickness of the single-sided PMMA film was 0.3 mm; and the mass ratio of the single-sided PMMA to the reversible photochromic compound in the reversible photochromic cellulose composite film was 1:0.1.

[0111] Figure 1Proton NMR spectrum of the 2PBS compound prepared in Example 1; Proton NMR spectrum uses deuterated chloroform as a deuterated reagent, and after integration processing, it is shown that the singlet peak occurring at 7.12ppm is attributed to the hydrogen on thiophene, and the doublet peak occurring at 7.44ppm and 7.75ppm is attributed to the hydrogen on both sides of benzothiophene. The triplet occurring at 7.12ppm is the attributed hydrogen of the phenyl ring of benzothiophene. The split peak occurring at 7.10ppm and 7.06ppm is attributed to the attributed hydrogen on the phenyl ring connected to the double bond. And the total number of hydrogen after integration is 20, corresponding to the number of molecular hydrogen, indicating that the 2PBS product is successfully synthesized.

[0112] Figure 2 This is the high-resolution mass spectrum of the 2PBS compound prepared in Example 1; as can be seen from the figure, the peak data in the high-resolution mass spectrum is the test data, and the molecular weight result is 444.762, which is consistent with the actual molecular weight M=444, proving that the 2PBS product was successfully synthesized.

[0113] Figure 3 Proton NMR spectra of the HPBS compound prepared in Example 2; Proton NMR spectra uses deuterated chloroform as a deuterated reagent, and after integration, the triplet occurring at 8.02ppm, the doublet occurring at 7.96ppm and 7.64ppm are attributed to the hydrogen of the phenyl ring on both sides of the benzothiophene, and the triplet occurring at 7.30ppm is attributed to the hydrogen on the phenyl ring on the left side of the double bond. The split peaks occurring at 7.45ppm and 7.43ppm are attributed to the hydrogen in the aromatic region. And the total number of hydrogen after integration is 16, corresponding to the molecular hydrogen number, indicating that the HPBS product is successfully synthesized.

[0114] Figure 4 This is a high-resolution mass spectrum of the HPBS compound prepared in Example 2; as can be seen from the figure, the peak data in the high-resolution mass spectrum is test data, and the molecular weight result is 369.02, which is consistent with the actual molecular weight M=368, proving that the HPBS product was successfully synthesized.

[0115] Figure 5 The hydrogen nuclear magnetic resonance spectrum of the 2PSF compound prepared in Example 3 is shown in Figure 3; the hydrogen nuclear magnetic resonance spectrum uses deuterated chloroform as a deuterated reagent. After integration, it is shown that the singlet peak appearing at 7.01ppm is attributed to the hydrogen on thiophene, and the doublet peak appearing at 7.69ppm and 7.31ppm is attributed to the hydrogen on the benzothiophene benzene ring on both sides. The triplet appearing at 7.06ppm is the attributed hydrogen of the benzene ring on the same side of the double bond. The split peaks appearing at 7.17ppm and 7.14ppm are attributed to the attributed hydrogen in the aromatic region. And the total number of hydrogen after integration is 20, which corresponds to the number of molecular hydrogen, indicating that the 2PSF product has been successfully synthesized.

[0116] Figure 6This is the high-resolution mass spectrum of the 2PSF compound prepared in Example 3; as can be seen from the figure, the peak data in the high-resolution mass spectrum is the test data, and the molecular weight result is 444.776, which is consistent with the actual molecular weight M=444, proving that the 2PSF product was successfully synthesized.

[0117] The compounds prepared in Examples 1 to 3 are arylethylene compounds containing benzothiophene; Figure 7 Schematic diagram of the photochemical phenomena of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 in different states; As can be seen from the figure, the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 have differences in different states, with obvious photophysical changes, i.e., changes in color visible to the naked eye. In the solid powder state, different and obvious color changes occur after ultraviolet light excitation (power of 10 W, wavelength of 365 nm), and can be irradiated with visible light (power of 1.5 W, wavelength of 524 nm). The results show that the color of 2PBS is light yellow and changes to orange-red after 10s of ultraviolet light irradiation; HPBS is beige and changes to orange-yellow after 10s of ultraviolet light irradiation; 2PSF is white and changes to purple after 10s of ultraviolet light irradiation; 2PBS, HPBS and 2PSF solid powders can return to their original colors after 30s of visible light irradiation; similarly, 2PBS, HPBS and 2PSF solid powders were added into tetrahydrofuran solution (concentration of 5×10 -5 M), and under UV excitation, the solutions changed from a transparent and colorless state to a distinct yellowish color, which was recoverable. While the luminescence ability is weak in solution, it is significantly enhanced in solid-state aggregates or at high concentrations. After 10 seconds of UV irradiation (power of 10W, wavelength of 365nm), blue fluorescence (2PBS compound solid powder and HPBS compound solid powder) and blue-green fluorescence (2PSF compound solid powder) are clearly visible.

[0118] The 2PBS compound, HPBS compound and 2PSF compound prepared in Examples 1 to 3 were added to the tetrahydrofuran solution (concentration of 5×10 -5 M), and then irradiated with ultraviolet light (power of 10 W, wavelength of 365 nm) for different time periods to test its fluorescence spectrum and UV-visible absorption spectrum; Figure 8 Schematic diagram of the molecular structure changes of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 under ultraviolet light (365 nm);

[0119] Figure 9The fluorescence spectra of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 change with time under continuous ultraviolet light irradiation in tetrahydrofuran. As can be seen from the figure, the fluorescence changes indicate that the photochromic phenomenon of the molecules is occurring; Figure 10 The UV-visible absorption spectra of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 under continuous UV irradiation in tetrahydrofuran over time; As can be seen from the figure, an increase in UV absorption value occurs at 3s of illumination, indicating a fast response speed, and in the UV-visible absorption spectrum, as the irradiation time increases, the maximum absorption gradually increases. When the absorption value reaches saturation, the chromophore in the material is completely or mostly converted into a photoactive form, which involves a photochemical reaction; under UV irradiation, the structure of the material changes, resulting in changes in its absorption characteristics; the speed of this process depends on the speed of the photochemical reaction and the intensity of illumination. In the fluorescence spectrum, after a substance absorbs light energy, electrons transition from the ground state to an excited state, and then return to the ground state through radiative transitions. After the molecule absorbs energy, a transition from the excited state to the ground state occurs. In addition, the fluorescence intensity depends not only on the generation of the excited state, but also on the fluorescence lifetime, quantum yield, and possible non-radiative decay processes.

[0120] The 2PBS compound, HPBS compound and 2PSF compound prepared in Examples 1 to 3 were prepared into tetrahydrofuran solutions (concentration of 5×10 -5 M), and then irradiated under ultraviolet light (power of 10 W, wavelength of 365 nm) for 20 s to test the fluorescence decay curve; Figure 11 The time-resolved fluorescence decay curves of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 are shown; as can be seen from the figure, the fluorescence lifetimes of the three compounds are 1.02ns, 0.78ns, and 1.17ns, respectively. Fluorescence lifetime refers to the average time required for a fluorescent substance to return from an excited state to a ground state. If the fluorescence lifetime is very short, for example, within a time scale of a few nanoseconds or less, then the fluorescent substance will emit most of the fluorescent photons at the beginning, which is reflected in a higher fluorescence intensity, so the compound can be seen to emit bright fluorescence. Experimental data and theoretical analysis reveal the general light-induced reversible cyclization and reaction involved in the benzothiophene in the photochromic molecules of the examples. The introduction of the benzothiophene group successfully enables these molecules to have significant photochemical activity in addition to the unique photophysical behavior of aggregation-induced emission. The experimental results show that the position and conjugation mode of the benzothiophene group have a significant effect on the color and intensity of the photochromic effect.

[0121] The 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 were added to a tetrahydrofuran / water mixed solution to obtain a tetrahydrofuran / water solution of the compound (concentration of 5×10-5 M), the volume percentage of water in the tetrahydrofuran / water mixed solution is 0% to 90%, and the volume of the solutions with different water contents is the same; since tetrahydrofuran and water are immiscible in a certain proportion, and the synthesized molecules are also immiscible in the aqueous solution, when the water content increases, the organic solvent and the molecules are squeezed by the water. Under the condition that the total volume remains unchanged, the state of the molecules at this time is more aggregated than the state without water, so as to test the fluorescence spectra under different aggregation degrees; Figure 12 Fluorescence spectra and fluorescence intensity dotted line graphs of the 2PBS, HPBS, and 2PSF compounds prepared in tetrahydrofuran / water solutions at different water contents, as well as the prepared molecules prepared in Examples 1 to 3, are shown. The graphs show that the prepared molecules exhibit weak or no fluorescence in pure tetrahydrofuran solution. As the water content increases from 0% to 90%, the molecules gradually aggregate, and the fluorescence intensity of the molecular solution gradually increases. The dotted line graphs clearly show the rapid increase in fluorescence intensity, demonstrating typical aggregation-induced luminescence (AIE) behavior, which addresses the aggregation-induced quenching (ACQ) problem of fluorescence observed in most conventional photochromic compounds.

[0122] The 2PBS compound, HPBS compound and 2PSF compound prepared in Examples 1 to 3 were added to the tetrahydrofuran solution (concentration of 5×10 -5 M), then irradiated under UV light (power of 10 W, wavelength of 365 nm) for 20 s, and then irradiated under visible light (power of 1.5 W, wavelength of 524 nm) for 60 s to perform a photochromic cycle test; Figure 13 The photochromic cycling test graphs of the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3, alternatingly exposed to ultraviolet light (365 nm) and visible light in a tetrahydrofuran solution; as can be seen from the figure, the compounds exhibit good reversible photochromic stability under 10 cycles of ultraviolet light and visible light in tetrahydrofuran solution, and can still recover after 10 complete photoswitching cycles, demonstrating excellent cyclability.

[0123] Using different masks, different images were sequentially written on the same filter paper using ultraviolet light (power of 10 W, wavelength of 365 nm), and then erased from the same filter paper by exposure to visible light (power of 1.5 W, wavelength of 524 nm). Figure 14This is a diagram of the light-controlled patterning application of the reversible photochromic filter paper prepared in Example 4; in the figure, the initial filter paper does not show a pattern. When Mask 1 (fennec fox) covers the filter paper and is written with ultraviolet light for 15 seconds, the information on Mask 1 appears red, and the written information can be easily removed by itself by exposing it to visible light for 60 seconds. Mask 2 (Northeast Forestry University), Mask 3 (cartoon snowman), and Mask 4 (snowflake) are used to alternately write and erase. These results show that the prepared compound can be used as an anti-counterfeiting ink and can be used to produce a variety of high-precision optically rewritable patterns.

[0124] The 2PSF@PMMA film prepared in Example 5 and the 2PSF@HPC film prepared in Example 6 were irradiated with UV light (power of 10 W, wavelength of 365 nm) for 30 s and then with visible light (power of 1.5 W, wavelength of 524 nm) for 60 s to perform a photochromic cycle test pattern; Figure 15 The photochromic cycle test diagram of the 2PSF@PMMA film prepared in Example 5 and the 2PSF@HPC film prepared in Example 6 were alternately exposed to ultraviolet light and visible light. As can be seen from the figure: the 2PSF@PMMA and 2PSF@HPC two-component films can undergo multiple cycle experiments under ultraviolet light and visible light cycles, that is, the performance is stable, it can be stored and used for a long time, and the material life is long.

[0125] The 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 were irradiated with ultraviolet light (power of 10 W, wavelength of 365 nm) for different time periods to measure their UV-visible absorption spectra. Figure 16 The UV-visible absorption spectra of the 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 change with time under continuous UV light irradiation; as can be seen from the figure: the absorption values ​​of the 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films change with time under continuous UV light irradiation gradually increase significantly, indicating that the degree of discoloration of the films deepens.

[0126] The 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 were irradiated with UV light (power of 10 W, wavelength of 365 nm) for 30 s and then with visible light (power of 1.5 W, wavelength of 524 nm) for 60 s to perform a photochromic cycling test. Figure 17The photochromic cycle test diagram of 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 were alternately exposed to ultraviolet light (365nm) and visible light; Figure 13 、 15 It can be seen that the three photochromic molecules 2PBS, HPBS, and 2PSF prepared in Examples 1 to 3 were alternately exposed to ultraviolet light (365nm) and visible light in tetrahydrofuran solution, and the photochromic cycle number had good cyclicity at 10 times; Examples 5 and 6 respectively prepared 2PSF@PMMA and 2PSF@HPC two-component films, which were alternately exposed to ultraviolet light (365nm) and visible light for photochromic cycle testing. After 10 complete optical switching cycles, the cyclicity decreased significantly. The number of cycles between coloring and bleaching of 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA cellulose composite films doubled, and after so many repeated processes, no obvious fatigue was observed in each of them. As a solid matrix, the cellulose composite film can effectively isolate the air from the molecules themselves, preventing free oxygen in the air from affecting the material itself. This fatigue resistance is due to the fact that the cellulose composite film effectively inhibits the oxidation of molecules by direct contact with free oxygen.

[0127] The 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 were first irradiated with ultraviolet light (power of 10 W, wavelength of 365 nm) for 30 seconds, and then decolorized under natural light. The absorption value after ultraviolet irradiation was tested using a UV-visible spectrophotometer and recorded as 0 seconds. The films were then spontaneously decolorized under natural light, and the changes in the absorption value were measured by a UV-visible spectrophotometer every one minute. Finally, a curve was plotted based on the measurement results. Figure 18 The relationship between the normalized absorbance and recovery time of the 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 is shown in Figure 2. The results show that the change in absorbance during the decolorization process is exponentially related to the recovery time. After fitting, the recovery rate constants were 0.003s and 0.1s, respectively. -1 , 0.012s -1 , 0.019s -1 , representing the speed of recovery. In short, the large variation in bleaching duration also provides a promising strategy for creating self-erasing time-related information encryption technology.

[0128] The 2PBS@HPC / PMMA, HPBS@HPC / PMMA, and 2PSF@HPC / PMMA films prepared in Example 7 were cut and spliced ​​at different parts to obtain photochromic films based on different isomerization rates. Figure 19 This is a QR code label based on photochromic films with different isomerization rates prepared in Example 7; as can be seen from the figure: the time-dependent encryption of QR code information is achieved by using photochromic films with different decolorization rates to create a time-dependent encryption of the QR code, which can be identified within a specific time range. Its change process is divided into four stages: a, b, c, and d. Initially, in stage a, all films are transparent and colorless, and the encrypted information cannot be recognized by smartphones. In stage b, after 30 seconds of ultraviolet light irradiation (power of 10W, wavelength of 365nm), the color changes from colorless to yellow. Since the entire QR code turns yellow, the encrypted QR code cannot be recognized by smartphones. The QR code was then exposed to visible light (1.5W, 524nm) for 120 seconds. Because the fading rate of 2PBS@HPC / PMMA was higher than that of HPBS@HPC / PMMA and 2PSF@HPC / PMMA, the yellow color of the interfering portion of 2PBS@HPC / PMMA disappeared first, triggering the smartphone to recognize the encrypted QR code. The encrypted message, "Northeast Forestry University," was read as "stage c." In stage d, after exposure to visible light (1.5W, 524nm) for 5 minutes, the color of the HPBS@HPC / PMMA portion faded further, rendering the message unreadable to the smartphone, achieving time-encrypted QR code. Due to the varying fading rates of the individual photochromic films, the encrypted QR code can only be recognized within a specific timeframe. Decryption of the encrypted message requires knowing the correct encryption method and decryption time.

[0129] Crystal structure analysis is the most effective and direct means of observing molecular stacking. In order to clarify the arrangement of the target molecules 2PBS, HPBS, and 2PSF in the solid state of Examples 1 to 3, crystals were prepared and single crystal XRD experiments were used to analyze the structure of the crystals. The solvent diffusion method was used to grow crystals. After the 2PBS compound, HPBS compound, and 2PSF compound prepared in Examples 1 to 3 were dissolved in a good solvent (dichloromethane or tetrahydrofuran) in a test tube, a small amount of poor solvent (methanol or petroleum ether) was added dropwise. After shaking evenly, the test tube mouth was plugged with cotton and the test tube was placed in a sealed wide-mouth bottle containing a poor solvent. The same poor solvent was used inside and outside the test tube. The wide-mouth bottle was placed in a crystal incubator that was kept at a constant temperature, kept away from light, and prevented from vibration. High-quality single crystals can be obtained within one week. Dichloromethane-methanol (volume ratio is 3:1), THF-methanol (volume ratio is 1:1), and dichloromethane-petroleum ether (volume ratio is 3:1) mixed solutions can all grow the same single crystal, and the crystals are white needle-shaped or regular cubes under daylight.

[0130] Figure 20 Figure 1 shows the single crystal structures of 2PBS, HPBS, and 2PSF; Table 1 shows the single crystal diffraction data for 2PBS, HPBS, and 2PSF. As shown in the figure, the packing structure within the crystal is long-range ordered. Single crystal XRD experiments can reveal the molecular structure and packing structure within the crystal. Single crystal XRD experiments also reveal the crystal system and space group of each crystal. Detailed crystallographic and refinement data are listed in Table 1.

[0131] Table 1

[0132]

[0133]

Claims

1. A reversible photochromic compound, characterized in that The structural formula of the reversible photochromic compound is 2. The method for preparing a reversible photochromic compound according to claim 1, wherein It is carried out in the following steps: The intermediate, the benzothiophene derivative, and potassium carbonate are dissolved in a mixed solution of tetrahydrofuran / water, and then, under nitrogen protection, tetrakis(triphenylphosphine)palladium is added, and the reaction is carried out under condensation reflux for 17 hours to 48 hours under a nitrogen atmosphere at a temperature of 60° C. to 90° C. After the reaction is completed, the volatile solvent is removed by distillation under reduced pressure, and then the organic phase is extracted three times with ethyl acetate and deionized water. The organic phase is dried with anhydrous magnesium sulfate, and finally, the mixture is purified by column chromatography using a mixed solution of dichloromethane / petroleum ether as an eluent to obtain a reversible photochromic compound. The structural formula of the intermediate is The benzothiophene derivative is benzothiophene-3-boric acid or 3-bromobenzothiophene.

3. The method for preparing a reversible photochromic compound according to claim 2, characterized in that The molar ratio of the intermediate to the benzothiophene derivative is 1:(2-2.6); the molar ratio of the intermediate to potassium carbonate is 1:(2.5-3.5); the molar ratio of the intermediate to tetrakis(triphenylphosphine)palladium is 1:(0.05-0.1); the volume ratio of the molar amount of the intermediate to a mixed solution of tetrahydrofuran / water is 1 mmol:(25-35) mL; the volume ratio of tetrahydrofuran to water in the mixed solution of tetrahydrofuran / water is 1:(0.35-0.45); and the volume ratio of dichloromethane to petroleum ether in the mixed solution of dichloromethane / petroleum ether is 1:(4-12).

4. The use of the reversible photochromic compound according to claim 1, characterized in that It is used in the preparation of reversible photochromic materials.

5. The use of the reversible photochromic compound according to claim 4, characterized in that The reversible photochromic material changes color under the alternating effects of ultraviolet light and visible light.

6. The use of the reversible photochromic compound according to claim 4, characterized in that The reversible photochromic material is reversible photochromic filter paper, reversible photochromic polymethyl methacrylate film, reversible photochromic hydroxypropyl cellulose film or reversible photochromic cellulose composite film.

7. The use of the reversible photochromic compound according to claim 6, characterized in that When the reversible photochromic material is a reversible photochromic filter paper, it is specifically prepared according to the following steps: The reversible photochromic compound is dissolved in dichloromethane to obtain a transparent solution, and the filter paper is immersed in the transparent solution at room temperature for 6 hours to 12 hours, and then dried to obtain the reversible photochromic filter paper; the mass ratio of the filter paper size to the reversible photochromic compound in the transparent solution is 1 cm 2 : (0.5 ~ 1) mg; the concentration of the reversible photochromic compound in the transparent solution is 1 mol / L ~ 2 mol / L.

8. The use of the reversible photochromic compound according to claim 6, characterized in that When the reversible photochromic material is a reversible photochromic polymethyl methacrylate film, it is specifically prepared according to the following steps: Polymethyl methacrylate and a reversible photochromic compound are dissolved in dichloromethane to obtain a transparent solution; the transparent solution is poured into a mold and naturally evaporated and dried at room temperature to obtain a reversible photochromic polymethyl methacrylate film; the mass ratio of the polymethyl methacrylate to the reversible photochromic compound is 1:(0.05-0.2); and the volume ratio of the polymethyl methacrylate to dichloromethane is 1 mg:(0.5-1) mL.

9. The use of the reversible photochromic compound according to claim 6, characterized in that When the reversible photochromic material is a reversible photochromic hydroxypropyl cellulose film, it is specifically prepared according to the following steps: A reversible photochromic compound is dissolved in dimethyl sulfoxide to obtain a transparent solution; hydroxypropyl cellulose is added to distilled water to obtain a hydroxypropyl cellulose aqueous solution; the transparent solution and the hydroxypropyl cellulose aqueous solution are mixed to obtain a mixed solution; the mixed solution is poured into a mold, and heated and dried at a temperature of 60°C to 65°C to obtain a reversible photochromic hydroxypropyl cellulose film; the mass ratio of the reversible photochromic compound to dimethyl sulfoxide is 1 mg:(0.05-0.2) mL; the mass ratio of the hydroxypropyl cellulose to distilled water is 1 mg:(0.5-1) mL; and the mass ratio of the hydroxypropyl cellulose to the reversible photochromic compound in the mixed solution is 1:(0.05-0.25).

10. The use of the reversible photochromic compound according to claim 6, characterized in that When the reversible photochromic material is a reversible photochromic cellulose composite film, it is specifically prepared according to the following steps: The reversible photochromic compound is dissolved in dimethyl sulfoxide to obtain a transparent solution; hydroxypropyl cellulose is added to distilled water to obtain a hydroxypropyl cellulose aqueous solution; the transparent solution and the hydroxypropyl cellulose aqueous solution are mixed to obtain a mixed solution; the mixed solution is poured into a mold covered with a PMMA film, heated and dried at a temperature of 60°C to 65°C, and then the PMMA solution is poured onto the surface, and heated and dried again at a temperature of 60°C to 65°C to form a PMMA / cellulose / PMMA structure, thereby obtaining a reversible photochromic cellulose composite film; The mass ratio of the reversible photochromic compound to dimethyl sulfoxide is 1 mg:(0.05-0.2) mL; the mass ratio of the hydroxypropyl cellulose to distilled water is 1 mg:(0.5-1) mL; the mass ratio of the hydroxypropyl cellulose to the reversible photochromic compound in the mixed solution is 1:(0.05-0.25); the thickness of the single-sided PMMA film is 0.1 mm to 0.5 mm; and the mass ratio of the single-sided PMMA to the reversible photochromic compound in the reversible photochromic cellulose composite film is 1:(0.1-0.2).

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