Photochromic rare earth polymer as well as preparation method and application thereof

Abstract

The invention discloses a photochromic rare earth polymer as well as a preparation method and application thereof, belongs to the field of photochromic anti-counterfeiting material research, and particularly relates to a photochromic rare earth polymer as well as a preparation method and application thereof. The problems that an existing anti-counterfeiting technology is prone to being counterfeited, high in cost, difficult to visually identify and the like in practical application are solved. The preparation method of the photochromic rare earth polymer is carried out under mild conditions, is simple, rapid, energy-saving and efficient, is wide in raw material and reagent source and low in price, effectively reduces the overall manufacturing cost of an anti-counterfeiting technology, and is beneficial to large-scale production and application. The color generation rate of the photochromic rare earth polymer in a strong light environment is 1t; in one second, the color fading rate in a weak light environment is lt; the unique optical characteristics of the rare earth polymer material come from the molecular structure and the characteristics of rare earth elements, so that the anti-counterfeiting bar code prepared from the photochromic rare earth polymer has higher safety and is difficult to copy.

Description

Technical Field

[0001] The invention belongs to the research field of photochromic anti-counterfeiting materials, and specifically relates to a photochromic rare earth polymer and a preparation method and application thereof. Background Art

[0002] Anti-counterfeiting barcodes play a vital role in modern society. They not only effectively protect the rights and interests of consumers and prevent them from buying counterfeit and shoddy products, but also help companies maintain their brand reputation and reduce economic losses caused by counterfeit products. With the popularization of barcodes, they have been widely used in various fields such as finance, medicine, food, and electronic products. However, with the development of science and technology, the means of producing counterfeit and shoddy products are also constantly upgrading, and traditional anti-counterfeiting technologies are difficult to cope with the increasingly complex counterfeiting methods. Therefore, new and more reliable anti-counterfeiting technologies are urgently needed to ensure the security and reliability of barcodes.

[0003] The anti-counterfeiting technologies currently on the market mainly include ink anti-counterfeiting, laser anti-counterfeiting and texture anti-counterfeiting. However, these anti-counterfeiting technologies all have certain limitations and problems. Although the ink anti-counterfeiting method has a low cost, it is easy to be counterfeited, and the anti-counterfeiting mark is easy to copy, and it is difficult to ensure a long-term anti-counterfeiting effect. Although the laser anti-counterfeiting method has a good anti-counterfeiting effect, it is expensive and has a long production cycle, and it is not easy to be promoted and applied on a large scale. Although the texture anti-counterfeiting method has certain uniqueness, it is expensive and has a limited scope of application, making it difficult to popularize in the market. In addition, these traditional anti-counterfeiting technologies are often difficult for consumers to intuitively identify in actual applications, resulting in unsatisfactory anti-counterfeiting effects. Summary of the invention

[0004] In order to solve the problems of easy counterfeiting, high cost and difficulty in intuitive identification faced by existing anti-counterfeiting technologies in practical applications, the present invention provides a preparation method of a photochromic rare earth polymer and its application.

[0005] The structural formula of the photochromic rare earth polymer of the present invention is:

[0006]

[0007] The general structural formula of the photochromic rare earth polymer is [Eu 2 L 3 (BTFPO) 2 ] n The photochromic rare earth polymer is composed of ligand L, auxiliary ligand BTFPO and rare earth Eu 3+ composition;

[0008] The structural formula of the auxiliary ligand BTFPO is:

[0009]

[0010] The structural formula of the ligand L is:

[0011]

[0012] The preparation method of the photochromic rare earth polymer is carried out according to the following steps:

[0013] Step 1. Synthesis of 2-methylbenzofuran

[0014] at -78 °C and N 2 Under protective conditions, 2-3 g of benzofuran was dissolved in a three-necked flask containing 40-50 mL of anhydrous tetrahydrofuran. After 10-15 minutes, 15-16 mL of butyl lithium was added. The mixture was stirred at -78 °C for 20 min. Then 4-5 mL of iodomethane was added dropwise to the reaction solution, and the reaction solution was restored to room temperature. 2 The reaction mixture was stirred at room temperature overnight under protective conditions, and then 0.2 mol / L aqueous ammonium chloride solution was added to the reaction solution to quench butyl lithium, and then tetrahydrofuran was removed by distillation to obtain a crude product, and finally the crude product was recrystallized and purified with n-hexane to obtain 2-methylbenzofuran; it was a white granular crystal with a yield of 80% to 90%;

[0015] Step 2: Synthesis of 2-methyl-3-bromobenzofuran

[0016] At 0°C, 5-6 g of 2-methylbenzofuran is dissolved in a mixed solution of 80-100 mL of glacial acetic acid and chloroform, 6-7 g of N-bromosuccinimide is added in a dark environment, the temperature is restored to room temperature, and the reaction is continued with stirring for 8 hours. Sodium carbonate is added to the reaction solution to neutralize the pH to 6-7, 30-50 mL of sodium thiosulfate solution is added to remove bromine, and the reaction solution is extracted with ethyl acetate, dried and concentrated to obtain a crude product, and the crude product is recrystallized and purified with n-hexane to obtain 2-methyl-3-bromobenzofuran as colorless crystals with a yield of 85%-95%;

[0017] The volume ratio of glacial acetic acid to chloroform in the mixed solution of glacial acetic acid and chloroform is 1:1;

[0018] The concentration of the sodium thiosulfate solution is 0.5 mol / L;

[0019] Step 3: Synthesis of 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene

[0020] at -78 °C and N 29-11 g of 2-methyl-3-bromobenzofuran was dissolved in 120-150 mL of dry tetrahydrofuran under the conditions of 15°C. After 15 minutes, 40-50 mL of n-butyl lithium was added dropwise to the reaction solution. The mixture was stirred at -78°C for 30 minutes. 2-4 mL of octafluorocyclopentene diluted with tetrahydrofuran was added dropwise to the reaction solution. After reacting at -78°C for 30 minutes, the reaction solution was restored to room temperature and then heated under N 2 The mixture was stirred overnight under the conditions. After the reaction was completed, water was added to the reaction bottle to quench the reaction. After the tetrahydrofuran solvent was removed by distillation under reduced pressure, ethyl acetate was added for extraction for 3 times, 20 to 30 mL each time, and finally dried and concentrated to obtain a crude product. The crude product was subjected to column chromatography under the condition of petroleum ether as an eluent, and then recrystallized from n-hexane to obtain 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene; it was white block crystals with a yield of 60% to 70%;

[0021] The volume ratio of tetrahydrofuran to octafluorocyclopentene is 5:1;

[0022] Step 4: Synthesis of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene

[0023] Add 2-3 g 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene, 2-4 mL 18.4 mol / L sulfuric acid, 6-8 mL water and 140-160 mL glacial acetic acid into the reaction bottle, heat the reaction solution to 60-70 °C, then add 1-2 g iodine and 0.3-0.4 g H 5 IO 6 Add to the reaction solution and react for 3 hours; then pour the reaction solution into 140-160 mL of water, add sodium carbonate to neutralize to pH 6-7, extract the organic layer with dichloromethane for 3 times, 30-40 mL each time, and then dry and concentrate to obtain a crude product, the crude product is subjected to column chromatography under the condition of petroleum ether as eluent, and then recrystallized with n-hexane to obtain 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene; it is white block crystals with a yield of 70%-80%;

[0024] Step 5: Synthesis of auxiliary ligand BTFPO

[0025] 1-3 g of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene and 3-4 g of triphenylphosphine borate were added to a mixed solvent containing 50-70 mL of toluene and 13-15 mL of isopropanol, and then 0.2-0.5 g of Pd(PPh 3 ) 2 Cl 2, heated to reflux for 24h; after the reaction was completed, the reaction solution was returned to room temperature, 50-60mL of water was added, and extracted with ethyl acetate 3 times, 20-30mL each time, and Na 2 SO 4 The organic layer is dried and concentrated to obtain a crude product, and the crude product is subjected to column chromatography under the condition of ethyl acetate as an eluent to obtain the auxiliary ligand BTFPO; it is in the form of a white powder, and the yield is 80% to 90%.

[0026] Step 6. Synthesis of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol)

[0027] In N 2 Under protection, 1-3g of 1,2-propylene glycol, 3-4g of anhydrous potassium carbonate and 5-6g of 4′-fluoroacetophenone are added to a three-necked flask containing 20-30mL of N,N-dimethylformamide solvent, the reaction solution is heated to 155°C and the reaction is continued for 19 hours. After the reaction is completed, the reaction solution is cooled to room temperature, the anhydrous potassium carbonate solid is removed by vacuum filtration, and the N,N-dimethylformamide solvent is removed from the remaining solution by vacuum distillation to obtain a crude product. The crude product is recrystallized in a methanol solvent to obtain 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol); it is a light yellow block crystal with a yield of 70% to 80%;

[0028] Step 7. Synthesis of ligand L

[0029] 0.5-0.8g of sodium methoxide and 1.5-2.0g of ethyl trifluoroacetate are added to a round-bottom flask containing 10-20mL of ethylene glycol dimethyl ether solution, and stirred for 10 minutes until the sodium methoxide is completely dissolved, and 1-2g of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol) is added, and stirred at room temperature for 24h; after the reaction is completed, the reaction solution is poured into a beaker containing 100-120mL of ice water, and the pH value of the ice water is adjusted to 2-3 with dilute hydrochloric acid (2mol / L) to obtain a yellow solid, which is filtered and dried naturally, and finally recrystallized in a n-hexane solution to obtain ligand L; it is a yellow needle-shaped crystal with a yield of 70%-80%;

[0030] Step 8: Complex Eu 2 L 3 Synthesis

[0031] Dissolve 0.03-0.05 g triethylamine and 0.03-0.05 g ligand L in 20-30 mL methanol solvent, add 0.50-0.80 mmol EuCl 3 6H 2 O, after stirring for 24 hours, the reaction solution was poured into water, filtered and dried to obtain the complex Eu 2 L 3; The white precipitate produced has a yield of 70% to 80%;

[0032] Step 9: Preparation of photochromic rare earth polymer [Eu 2 L 3 (BTFPO) 2 ] n

[0033] 0.1~0.2gEu 2 L 3 and 0.1-0.2 g BTFPO were dissolved in 20-30 mL methanol, stirred at 70 ° C overnight, the reaction solution was poured into water, filtered and dried to obtain a photochromic rare earth polymer [Eu 2 L 3 (BTFPO) 2 ] n ; The yield is 70% to 80%.

[0034] The method for preparing an anti-counterfeiting barcode using the photochromic rare earth polymer of the present invention is carried out according to the following steps:

[0035] 1. dissolving the photochromic rare earth polymer in tetrahydrofuran solvent to obtain a photochromic rare earth polymer solution;

[0036] The concentration of the photochromic rare earth polymer solution is 1×10 -5 ~1×10 -2 mol / L;

[0037] 2. Printing a barcode model on a substrate using 3D printing technology, wherein the recessed area of ​​the barcode model is a filling and molding area of ​​the photochromic rare earth polymer;

[0038] 3. Filling the photochromic rare earth polymer solution obtained in step 1 into the concave area of ​​the barcode model, curing after irradiation with 350-370nm ultraviolet light for 5-10 minutes to obtain a barcode with photochromic properties;

[0039] Fourth, placing the barcode with photochromic properties obtained in step 3 in an environment with ultraviolet light, the photochromic rare earth polymer changes color when exposed to light, and the barcode with complete information can be displayed;

[0040] When the barcode with photochromic properties obtained in step 4 is placed in an environment without ultraviolet light, the area covered by the rare earth polymer material appears light-colored and the complete barcode pattern cannot be displayed; the barcode information cannot be read when scanned with a mobile phone.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] 1. The preparation method of the photochromic rare earth polymer of the present invention is carried out under relatively mild conditions, which is not only simple and rapid but also energy-saving and efficient. The raw materials and reagents are widely available and inexpensive, which effectively reduces the overall cost of anti-counterfeiting technology and is conducive to large-scale production and application.

[0043] 2. The photochromic rare earth polymer of the present invention is a spiral polymer with a hole structure composed of two ligands and a metal, which allows the photochromic unit to rotate freely under light. This structural design effectively solves the problem of limited molecular motion space in the solid state of the color-changing material. In addition, microporous structures are formed during the synthesis of the polymer. These pore structures not only increase the free volume of the material, but also provide more space for the movement of molecules, making the photochromic process more efficient, thereby improving the color-changing performance in the film-forming material.

[0044] The photochromic rare earth polymer of the present invention has a coloring rate of less than 1 second in a strong light environment and a fading rate of less than 30 seconds in a weak light environment, and has good fatigue resistance and can be reused.

[0045] 3. The anti-counterfeiting barcode prepared by the photochromic rare earth polymer of the present invention involves the dual technical barriers of multi-step complex chemical synthesis and physical processing, forming an innovative defense line that is difficult to copy. The uniqueness lies in the use of the photochromic principle, which is based on the scientific phenomenon that rare earth materials produce color changes under specific ultraviolet light irradiation, giving the anti-counterfeiting barcode extremely high security and difficult-to-copy technical characteristics, greatly increasing the difficulty of counterfeiting. In addition, the application field of the rare earth polymer anti-counterfeiting barcode is commodity anti-counterfeiting. Therefore, even if it is photographed and printed under ultraviolet light, although information can be obtained, the unique optical properties of the rare earth polymer material are derived from its molecular structure and the properties of the rare earth elements. Ordinary photography and printing cannot reproduce these material properties, making the anti-counterfeiting barcode prepared by the photochromic rare earth polymer highly secure and difficult to copy.

[0046] 4. The principle of the anti-counterfeiting barcode prepared by the photochromic rare earth polymer of the present invention is that the barcode pattern is not fully displayed in an environment without ultraviolet light, and the barcode pattern can only be fully displayed under ultraviolet light, forming a dynamic anti-counterfeiting effect. This feature facilitates intuitive identification and verification of barcode information, greatly improving the recognizability and ease of use of the anti-counterfeiting mark. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a picture of the barcode with photochromic properties in Example 1 under natural light;

[0048] Figure 2 This is a picture of the barcode with photochromic properties in Example 1 under ultraviolet light. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0050] Specific implementation method 1: The structural formula of the photochromic rare earth polymer in this implementation method is:

[0051]

[0052] The general structural formula of the photochromic rare earth polymer is [Eu 2 L 3 (BTFPO) 2 ] n The photochromic rare earth polymer is composed of ligand L, auxiliary ligand BTFPO and rare earth Eu 3+ composition;

[0053] The structural formula of the auxiliary ligand BTFPO is:

[0054]

[0055] The structural formula of the ligand L is:

[0056]

[0057] This embodiment has the following beneficial effects:

[0058] 1. The preparation method of the photochromic rare earth polymer of this embodiment is carried out under relatively mild conditions, which is not only simple and rapid but also energy-saving and efficient. The raw materials and reagents are widely available and inexpensive, which effectively reduces the overall cost of anti-counterfeiting technology and is conducive to large-scale production and application.

[0059] 2. The photochromic rare earth polymer of this embodiment is a spiral polymer with a hole structure composed of two ligands and a metal, which allows the photochromic unit to rotate freely under light. This structural design effectively solves the problem of limited molecular motion space in the solid state of the color-changing material. In addition, microporous structures are formed during the synthesis of the polymer. These pore structures not only increase the free volume of the material, but also provide more space for the movement of molecules, making the photochromic process more efficient, thereby improving the color-changing performance in the film-forming material.

[0060] The photochromic rare earth polymer of this embodiment has a color development rate of less than 1 second in a strong light environment and a fading rate of less than 30 seconds in a weak light environment, and has good fatigue resistance and can be reused.

[0061] 3. The anti-counterfeiting barcode prepared by the photochromic rare earth polymer of this embodiment involves the dual technical barriers of multi-step complex chemical synthesis and physical processing, forming an innovative defense line that is difficult to copy. The uniqueness lies in the use of the photochromic principle, which is based on the scientific phenomenon that rare earth materials produce color changes under specific ultraviolet light irradiation, giving the anti-counterfeiting barcode extremely high security and difficult-to-copy technical characteristics, greatly increasing the difficulty of counterfeiting. In addition, the application field of rare earth polymer anti-counterfeiting barcodes is commodity anti-counterfeiting. Therefore, even if you take a photo and print it out under ultraviolet light, although you can obtain information, because the unique optical properties of rare earth polymer materials come from their molecular structure and the properties of rare earth elements, ordinary photography and printing cannot reproduce these material properties, making the anti-counterfeiting barcode prepared by photochromic rare earth polymers have high security and are difficult to copy.

[0062] 4. The principle of the anti-counterfeiting barcode prepared by the photochromic rare earth polymer in this embodiment is that the barcode pattern is not fully displayed in an environment without ultraviolet light, and the barcode pattern can only be fully displayed under ultraviolet light, forming a dynamic anti-counterfeiting effect. This feature facilitates intuitive identification and verification of barcode information, greatly improving the recognizability and ease of use of the anti-counterfeiting mark.

[0063] Specific implementation method 2: The preparation method of the photochromic rare earth polymer in this implementation method is carried out according to the following steps:

[0064] Step 1. Synthesis of 2-methylbenzofuran

[0065] at -78 °C and N 2 Under protective conditions, 2-3 g of benzofuran was dissolved in a three-necked flask containing 40-50 mL of anhydrous tetrahydrofuran. After 10-15 minutes, 15-16 mL of butyl lithium was added. The mixture was stirred at -78 °C for 20 min. Then 4-5 mL of iodomethane was added dropwise to the reaction solution, and the reaction solution was restored to room temperature. 2 The reaction mixture was stirred at room temperature overnight under protective conditions, and then 0.2 mol / L aqueous ammonium chloride solution was added to the reaction solution to quench butyl lithium, and then tetrahydrofuran was removed by distillation to obtain a crude product, and finally the crude product was recrystallized and purified with n-hexane to obtain 2-methylbenzofuran; it was a white granular crystal with a yield of 80% to 90%;

[0066] Step 2: Synthesis of 2-methyl-3-bromobenzofuran

[0067] At 0°C, 5-6 g of 2-methylbenzofuran is dissolved in a mixed solution of 80-100 mL of glacial acetic acid and chloroform, 6-7 g of N-bromosuccinimide is added in a dark environment, the temperature is restored to room temperature, and the reaction is continued with stirring for 8 hours. Sodium carbonate is added to the reaction solution to neutralize the pH to 6-7, 30-50 mL of sodium thiosulfate solution is added to remove bromine, and the reaction solution is extracted with ethyl acetate, dried and concentrated to obtain a crude product, and the crude product is recrystallized and purified with n-hexane to obtain 2-methyl-3-bromobenzofuran as colorless crystals with a yield of 85%-95%;

[0068] Step 3: Synthesis of 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene

[0069] at -78 °C and N 2 9-11 g of 2-methyl-3-bromobenzofuran was dissolved in 120-150 mL of dry tetrahydrofuran under the conditions of 15 ° C. After 15 minutes, 40-50 mL of n-butyl lithium was added dropwise to the reaction solution, and the mixture was stirred at -78 ° C for 30 minutes. 4-5 mL of octafluorocyclopentene diluted with tetrahydrofuran was added dropwise to the reaction solution, and the mixture was reacted at -78 ° C for 30 minutes. The reaction solution was restored to room temperature and then heated under N 2 The mixture was stirred overnight under the conditions. After the reaction was completed, water was added to the reaction bottle to quench the reaction. After the tetrahydrofuran solvent was removed by distillation under reduced pressure, ethyl acetate was added for extraction for 3 times, 20 to 30 mL each time, and finally dried and concentrated to obtain a crude product. The crude product was subjected to column chromatography under the condition of petroleum ether as an eluent, and then recrystallized from n-hexane to obtain 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene; it was white block crystals with a yield of 60% to 70%;

[0070] Step 4: Synthesis of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene

[0071] Add 2-3 g 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene, 2-4 mL 18.4 mol / L sulfuric acid, 6-8 mL water and 140-160 mL glacial acetic acid into the reaction bottle, heat the reaction solution to 60-70 °C, then add 1-2 g iodine and 0.3-0.4 g H 5 IO 6Add to the reaction solution and react for 3 hours; then pour the reaction solution into 140-160 mL of water, add sodium carbonate to neutralize to pH 6-7, extract the organic layer with dichloromethane for 3 times, 30-40 mL each time, and then dry and concentrate to obtain a crude product, the crude product is subjected to column chromatography under the condition of petroleum ether as eluent, and then recrystallized with n-hexane to obtain 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene; it is white block crystals with a yield of 70%-80%;

[0072] Step 5: Synthesis of auxiliary ligand BTFPO

[0073] 1-3 g of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene and 3-4 g of triphenylphosphine borate were added to a mixed solvent containing 50-70 mL of toluene and 13-15 mL of isopropanol, and then 0.2-0.5 g of Pd(PPh 3 ) 2 Cl 2 , heated to reflux for 24 h; after the reaction was completed, the reaction solution was returned to room temperature, 50-60 mL of water was added, extracted with ethyl acetate three times, and then washed with Na 2 SO 4 The organic layer is dried and concentrated to obtain a crude product, and the crude product is subjected to column chromatography under the condition of ethyl acetate as an eluent to obtain the auxiliary ligand BTFPO; it is in the form of a white powder, and the yield is 80% to 90%.

[0074] Step 6. Synthesis of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol)

[0075] In N 2 Under protection, 1-3g of 1,2-propylene glycol, 3-4g of anhydrous potassium carbonate and 5-6g of 4′-fluoroacetophenone are added to a three-necked flask containing 20-30mL of N,N-dimethylformamide solvent, the reaction solution is heated to 155°C and the reaction is continued for 19 hours. After the reaction is completed, the reaction solution is cooled to room temperature, the anhydrous potassium carbonate solid is removed by vacuum filtration, and the N,N-dimethylformamide solvent is removed from the remaining solution by vacuum distillation to obtain a crude product. The crude product is recrystallized in a methanol solvent to obtain 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol); it is a light yellow block crystal with a yield of 70% to 80%;

[0076] Step 7. Synthesis of ligand L

[0077] 0.5-0.8g of sodium methoxide and 1.5-2.0g of ethyl trifluoroacetate are added to a round-bottom flask containing 10-20mL of ethylene glycol dimethyl ether solution, and stirred for 10 minutes until the sodium methoxide is completely dissolved, and 1-2g of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol) is added, and stirred at room temperature for 24h; after the reaction is completed, the reaction solution is poured into a beaker containing 100-120mL of ice water, and the pH value of the ice water is adjusted to 2-3 with dilute hydrochloric acid (2mol / L) to obtain a yellow solid, which is filtered and dried naturally, and finally recrystallized in a n-hexane solution to obtain ligand L; it is a yellow needle-shaped crystal with a yield of 70%-80%;

[0078] Step 8: Complex Eu 2 L 3 Synthesis

[0079] Dissolve 0.03-0.05 g triethylamine and 0.1-0.3 g ligand L in 20-30 mL methanol solvent, add 0.50-0.80 mmol EuCl 3 6H 2 O, after stirring for 24 hours, the reaction solution was poured into water, filtered and dried to obtain the complex Eu 2 L 3 ; The white precipitate produced has a yield of 70% to 80%;

[0080] Step 9: Preparation of photochromic rare earth polymer [Eu 2 L 3 (BTFPO) 2 ] n

[0081] 0.1~0.2gEu 2 L 3 and 0.1-0.2 g BTFPO were dissolved in 20-30 mL methanol, stirred at 70 ° C overnight, the reaction solution was poured into water, filtered and dried to obtain a photochromic rare earth polymer [Eu 2 L 3 (BTFPO) 2 ] n ; The yield is 70% to 80%.

[0082] 1. The preparation method of the photochromic rare earth polymer of this embodiment is carried out under relatively mild conditions, which is not only simple and rapid but also energy-saving and efficient. The raw materials and reagents are widely available and inexpensive, which effectively reduces the overall cost of anti-counterfeiting technology and is conducive to large-scale production and application.

[0083] 2. The photochromic rare earth polymer of this embodiment is a spiral polymer with a hole structure composed of two ligands and a metal, which allows the photochromic unit to rotate freely under light. This structural design effectively solves the problem of limited molecular motion space in the solid state of the color-changing material. In addition, microporous structures are formed during the synthesis of the polymer. These pore structures not only increase the free volume of the material, but also provide more space for the movement of molecules, making the photochromic process more efficient, thereby improving the color-changing performance in the film-forming material.

[0084] The photochromic rare earth polymer of this embodiment has a color development rate of less than 1 second in a strong light environment and a fading rate of less than 30 seconds in a weak light environment, and has good fatigue resistance and can be reused.

[0085] 3. The anti-counterfeiting barcode prepared by the photochromic rare earth polymer of this embodiment involves the dual technical barriers of multi-step complex chemical synthesis and physical processing, forming an innovative defense line that is difficult to copy. The uniqueness lies in the use of the photochromic principle, which is based on the scientific phenomenon that rare earth materials produce color changes under specific ultraviolet light irradiation, giving the anti-counterfeiting barcode extremely high security and difficult-to-copy technical characteristics, greatly increasing the difficulty of counterfeiting. In addition, the application field of rare earth polymer anti-counterfeiting barcodes is commodity anti-counterfeiting. Therefore, even if you take a photo and print it out under ultraviolet light, although you can obtain information, because the unique optical properties of rare earth polymer materials come from their molecular structure and the properties of rare earth elements, ordinary photography and printing cannot reproduce these material properties, making the anti-counterfeiting barcode prepared by photochromic rare earth polymers have high security and are difficult to copy.

[0086] 4. The principle of the anti-counterfeiting barcode prepared by the photochromic rare earth polymer in this embodiment is that the barcode pattern is not fully displayed in an environment without ultraviolet light, and the barcode pattern can only be fully displayed under ultraviolet light, forming a dynamic anti-counterfeiting effect. This feature facilitates intuitive identification and verification of barcode information, greatly improving the recognizability and ease of use of the anti-counterfeiting mark.

[0087] Specific implementation method three: This implementation method is different from specific implementation method two in that: in the mixed solution of glacial acetic acid and chloroform in step one, the volume ratio of glacial acetic acid to chloroform is 1:1.

[0088] Specific implementation method 4: This implementation method is different from specific implementation method 2 in that the concentration of the sodium thiosulfate solution in step 1 is 0.5 mol / L.

[0089] Specific implementation mode 5: This implementation mode is different from specific implementation mode 2 in that: the volume ratio of tetrahydrofuran and octafluorocyclopentene in step 3 is 5:1.

[0090] Specific implementation method 6: This implementation method is different from specific implementation method 2 in that: in step 3, ethyl acetate is added for extraction 3 times, with 20 to 30 mL of ethyl acetate added each time.

[0091] Specific embodiment 7: This embodiment differs from specific embodiment 2 in that: in step 4, the organic layer is extracted with dichloromethane for 3 times, using 30-40 mL of dichloromethane each time.

[0092] Specific embodiment eight: This embodiment differs from specific embodiment two in that: Step five is to extract with ethyl acetate three times, using 20 to 30 mL of ethyl acetate each time.

[0093] Specific embodiment 9: The method for preparing anti-counterfeiting barcodes using photochromic rare earth polymers in this embodiment is carried out according to the following steps:

[0094] 1. dissolving the photochromic rare earth polymer in tetrahydrofuran solvent to obtain a photochromic rare earth polymer solution;

[0095] 2. Printing a barcode model on a substrate using 3D printing technology, wherein the recessed area of ​​the barcode model is a filling and molding area of ​​the photochromic rare earth polymer;

[0096] 3. Filling the photochromic rare earth polymer solution obtained in step 1 into the concave area of ​​the barcode model, curing after irradiation with 350-370nm ultraviolet light for 5-10 minutes to obtain a barcode with photochromic properties;

[0097] Fourth, the barcode with photochromic properties obtained in step three is placed in an environment with ultraviolet light, and the photochromic rare earth polymer changes color when exposed to light, showing a barcode with complete information that can be read.

[0098] 1. The preparation method of the photochromic rare earth polymer of this embodiment is carried out under relatively mild conditions, which is not only simple and rapid but also energy-saving and efficient. The raw materials and reagents are widely available and inexpensive, which effectively reduces the overall cost of anti-counterfeiting technology and is conducive to large-scale production and application.

[0099] 2. The photochromic rare earth polymer of this embodiment is a spiral polymer with a hole structure composed of two ligands and a metal, which allows the photochromic unit to rotate freely under light. This structural design effectively solves the problem of limited molecular motion space in the solid state of the color-changing material. In addition, microporous structures are formed during the synthesis of the polymer. These pore structures not only increase the free volume of the material, but also provide more space for the movement of molecules, making the photochromic process more efficient, thereby improving the color-changing performance in the film-forming material.

[0100] The photochromic rare earth polymer of this embodiment has a color development rate of less than 1 second in a strong light environment and a fading rate of less than 30 seconds in a weak light environment, and has good fatigue resistance and can be reused.

[0101] 3. The anti-counterfeiting barcode prepared by the photochromic rare earth polymer of this embodiment involves the dual technical barriers of multi-step complex chemical synthesis and physical processing, forming an innovative defense line that is difficult to copy. The uniqueness lies in the use of the photochromic principle, which is based on the scientific phenomenon that rare earth materials produce color changes under specific ultraviolet light irradiation, giving the anti-counterfeiting barcode extremely high security and difficult-to-copy technical characteristics, greatly increasing the difficulty of counterfeiting. In addition, the application field of rare earth polymer anti-counterfeiting barcodes is commodity anti-counterfeiting. Therefore, even if you take a photo and print it out under ultraviolet light, although you can obtain information, because the unique optical properties of rare earth polymer materials come from their molecular structure and the properties of rare earth elements, ordinary photography and printing cannot reproduce these material properties, making the anti-counterfeiting barcode prepared by photochromic rare earth polymers have high security and are difficult to copy.

[0102] 4. The principle of the anti-counterfeiting barcode prepared by the photochromic rare earth polymer in this embodiment is that the barcode pattern is not fully displayed in an environment without ultraviolet light, and the barcode pattern can only be fully displayed under ultraviolet light, forming a dynamic anti-counterfeiting effect. This feature facilitates intuitive identification and verification of barcode information, greatly improving the recognizability and ease of use of the anti-counterfeiting mark.

[0103] Specific embodiment 10: This embodiment differs from the first to ninth embodiments in that the concentration of the photochromic rare earth polymer solution in step 1 is 1×10 -5 ~1×10 -2 mol / L.

[0104] Example 1

[0105] The structural formula of the photochromic rare earth polymer in this embodiment is:

[0106]

[0107] The general structural formula of the photochromic rare earth polymer is [Eu 2 L 3 (BTFPO) 2 ] n The photochromic rare earth polymer is composed of ligand L, auxiliary ligand BTFPO and rare earth Eu 3+ composition;

[0108] The structural formula of the auxiliary ligand BTFPO is:

[0109]

[0110] The structural formula of the ligand L is:

[0111]

[0112] The preparation method of the photochromic rare earth polymer of this embodiment is carried out according to the following steps:

[0113] Step 1. Synthesis of 2-methylbenzofuran

[0114] at -78 °C and N 2 Under protective conditions, 2.55 g of benzofuran was dissolved in a three-necked flask containing 50 mL of anhydrous tetrahydrofuran. After 10 minutes, 15.14 mL of butyl lithium was added. The mixture was stirred at -78 °C for 20 min. Then 4.65 mL of iodomethane was added dropwise to the reaction solution, and the reaction solution was returned to room temperature. 2 The reaction mixture was stirred at room temperature overnight under protective conditions, and then 0.2 mol / L aqueous ammonium chloride solution was added to the reaction solution to quench butyl lithium, and then tetrahydrofuran was removed by distillation to obtain a crude product, and finally the crude product was recrystallized and purified with n-hexane to obtain 2-methylbenzofuran; it was white granular crystals, and the yield was 87%;

[0115] Step 2: Synthesis of 2-methyl-3-bromobenzofuran

[0116] At 0°C, 5.0 g of 2-methylbenzofuran was dissolved in a mixed solution of 80 mL of glacial acetic acid and chloroform, 6.6 g of N-bromosuccinimide was added in a dark environment, the temperature was restored to room temperature, and the reaction was continued with stirring for 8 hours. Sodium carbonate was added to the reaction solution to neutralize it to a pH of 7, 50 mL of sodium thiosulfate solution was added to remove the bromine element, and the reaction solution was extracted with ethyl acetate, dried and concentrated to obtain a crude product, and the crude product was recrystallized and purified with n-hexane to obtain 2-methyl-3-bromobenzofuran as colorless crystals with a yield of 92%;

[0117] The volume ratio of glacial acetic acid to chloroform in the mixed solution of glacial acetic acid and chloroform is 1:1;

[0118] The concentration of the sodium thiosulfate solution is 0.5 mol / L;

[0119] Step 3: Synthesis of 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene

[0120] at -78 °C and N 210.0 g of 2-methyl-3-bromobenzofuran was dissolved in 150 mL of dry tetrahydrofuran under the conditions of 1% ethyl acetate, and 43.2 mL of n-butyl lithium was added dropwise to the reaction solution after 15 min of stirring at -78 °C for 30 min. 3 mL of octafluorocyclopentene diluted with tetrahydrofuran was added dropwise to the reaction solution, and after reacting at -78 °C for 30 min, the reaction solution was returned to room temperature and then heated under N 2 The stirring was continued overnight under the conditions. After the reaction was completed, water was added to the reaction bottle to quench the reaction. After the tetrahydrofuran solvent was removed by distillation under reduced pressure, ethyl acetate was added for extraction for 3 times, 30 mL each time, and finally dried and concentrated to obtain a crude product. The crude product was subjected to column chromatography under the condition of petroleum ether as an eluent, and then recrystallized from n-hexane to obtain 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene; it was white block crystals with a yield of 60.7%;

[0121] The volume ratio of tetrahydrofuran to octafluorocyclopentene is 5:1;

[0122] Step 4: Synthesis of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene

[0123] 2.0 g of 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene, 3 mL of 18.4 mol / L sulfuric acid, 7 mL of water and 150 mL of glacial acetic acid were added to the reaction flask. The reaction solution was heated to 65 °C. Then, 1.2 g of iodine and 0.39 g of H 5 IO 6 Add to the reaction solution and react for 3 hours; then pour the reaction solution into 150 mL of water, add sodium carbonate to neutralize to pH 7, extract the organic layer with dichloromethane 3 times, 40 mL each time, and then dry and concentrate to obtain a crude product, the crude product is subjected to column chromatography under the condition of petroleum ether as eluent, and then recrystallized with n-hexane to obtain 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene; it is a white block crystal with a yield of 75%;

[0124] Step 5: Synthesis of auxiliary ligand BTFPO

[0125] 2.0 g of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene and 3.36 g of triphenylphosphine borate were added to a mixed solvent containing 60 mL of toluene and 14 mL of isopropanol, and then 0.3 g of Pd(PPh 3 ) 2 Cl 2 , heated to reflux for 24 h; after the reaction was completed, the reaction solution was returned to room temperature, 50 mL of water was added, extracted with ethyl acetate 3 times, 30 mL each time, and Na 2 SO4 The organic layer was dried and concentrated to obtain a crude product, and the crude product was subjected to column chromatography under the condition of ethyl acetate as an eluent to obtain the auxiliary ligand BTFPO; it was in the form of a white powder with a yield of 84%.

[0126] Step 6. Synthesis of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol)

[0127] In N 2 Under protection, 1.0g of 1,2-propylene glycol, 3.63g of anhydrous potassium carbonate and 5.4g of 4′-fluoroacetophenone were added to a three-necked flask containing 20mL of N,N-dimethylformamide solvent, the reaction solution was heated to 155°C and the reaction was continued for 19 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the anhydrous potassium carbonate solid was removed by vacuum filtration. The remaining solution was distilled under reduced pressure to remove the N,N-dimethylformamide solvent to obtain a crude product. The crude product was recrystallized in methanol solvent to obtain 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol); it was light yellow block crystals with a yield of 70%;

[0128] Step 7. Synthesis of ligand L

[0129] 0.69 g of sodium methoxide and 1.82 g of ethyl trifluoroacetate were added to a round-bottom flask containing 10 mL of ethylene glycol dimethyl ether solution, and the mixture was stirred for 10 minutes until all the sodium methoxide was dissolved. 1.0 g of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol) was added, and the mixture was stirred at room temperature for 24 h. After the reaction was completed, the reaction solution was poured into a beaker containing 100 mL of ice water, and the pH value of the ice water was adjusted to 3 with dilute hydrochloric acid (2 mol / L) to obtain a yellow solid. The solid was filtered and dried naturally, and finally recrystallized in a n-hexane solution to obtain ligand L, which was yellow needle-shaped crystals with a yield of 75%.

[0130] Step 8: Complex Eu 2 L 3 Synthesis

[0131] 0.05 g triethylamine and 0.2 g ligand L were dissolved in 30 mL methanol solvent and 0.80 mmol EuCl was added. 3 6H 2 O, after stirring for 24 hours, the reaction solution was poured into water, filtered and dried to obtain the complex Eu 2 L 3 ; The white precipitate produced has a yield of 80%;

[0132] Step 9: Preparation of photochromic rare earth polymer [Eu 2 L 3 (BTFPO) 2 ] n

[0133] 0.1gEu 2 L 3 and 0.11 g BTFPO were dissolved in 20 mL methanol, stirred at 70 ° C overnight, the reaction solution was poured into water, filtered and dried to obtain a photochromic rare earth polymer [Eu 2 L 3 (BTFPO) 2 ] n ; The yield is 68%.

[0134] Application of the photochromic rare earth polymer of the present invention:

[0135] 1. Dissolving the photochromic rare earth polymer in tetrahydrofuran solvent to obtain a photochromic rare earth polymer solution; the concentration of the photochromic rare earth polymer solution is 1×10 -3 mol / L;

[0136] 2. Printing a barcode model on a substrate using 3D printing technology, wherein the recessed area of ​​the barcode model is a filling and molding area of ​​the photochromic rare earth polymer;

[0137] 3. Filling the photochromic rare earth polymer solution obtained in step 1 into the concave area of ​​the barcode model, curing after irradiation with 365nm ultraviolet light for 10 minutes, to obtain a barcode with photochromic properties;

[0138] Fourth, placing the barcode with photochromic properties obtained in step 3 in an environment with ultraviolet light, the photochromic rare earth polymer changes color when exposed to light, and the barcode with complete information can be displayed;

[0139] When the barcode with photochromic properties obtained in step 4 is placed in an environment without ultraviolet light, the area covered by the rare earth polymer material appears light-colored and the complete barcode pattern cannot be displayed; the barcode information cannot be read when scanned with a mobile phone; Figure 1 This is a picture of the barcode with photochromic properties in Example 1 under natural light; Figure 1 In the middle, a is a concave area, and the photochromic rare earth polymer solution inside has been solidified; Figure 2 This is a picture of the barcode with photochromic properties in Example 1 under ultraviolet light; it can be seen that the barcode pattern can be fully displayed under ultraviolet light, forming a dynamic anti-counterfeiting effect.

Claims

1. A photochromic rare earth polymer, characterized in that: The structural formula of photochromic rare earth polymer is: The general structural formula of the photochromic rare earth polymer is [Eu2L3(BTFPO)2] n The photochromic rare earth polymer is composed of ligand L, auxiliary ligand BTFPO and rare earth Eu 3+ composition; The structural formula of the auxiliary ligand BTFPO is: The structural formula of the ligand L is:

2. The method for preparing a photochromic rare earth polymer according to claim 1, characterized in that: The preparation method of the photochromic rare earth polymer is carried out according to the following steps: Step 1. Synthesis of 2-methylbenzofuran At -78°C and N2 protection, 2-3 g of benzofuran is dissolved in a three-necked flask containing 40-50 mL of anhydrous tetrahydrofuran, and 15-16 mL of butyl lithium is added after 10-15 minutes, and the mixture is stirred at -78°C for 20 minutes, and then 4-5 mL of methyl iodide is added dropwise to the reaction solution, and the reaction solution is restored to room temperature; under N2 protection, the mixture is stirred at room temperature overnight, and then a 0.2 mol / L aqueous solution of ammonium chloride is added to the reaction solution to quench the butyl lithium, and then tetrahydrofuran is removed by distillation to obtain a crude product, and finally the crude product is recrystallized and purified with n-hexane to obtain 2-methylbenzofuran; the product is white granular crystals, and the yield is 80%-90%; Step 2: Synthesis of 2-methyl-3-bromobenzofuran At 0°C, 5-6 g of 2-methylbenzofuran is dissolved in a mixed solution of 80-100 mL of glacial acetic acid and chloroform, 6-7 g of N-bromosuccinimide is added in a dark environment, the temperature is restored to room temperature, and the reaction is continued with stirring for 8 hours. Sodium carbonate is added to the reaction solution to neutralize the pH to 6-7, 30-50 mL of sodium thiosulfate solution is added to remove bromine, and the reaction solution is extracted with ethyl acetate, dried and concentrated to obtain a crude product, and the crude product is recrystallized and purified with n-hexane to obtain 2-methyl-3-bromobenzofuran as colorless crystals with a yield of 85%-95%; Step 3: Synthesis of 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene 9-11 g of 2-methyl-3-bromobenzofuran was dissolved in 120-150 mL of dry tetrahydrofuran at -78°C and N2. After 15 minutes, 40-50 mL of n-butyl lithium was added dropwise to the reaction solution. The mixture was stirred at -78°C for 30 minutes. 4-5 mL of octafluorocyclopentene diluted with tetrahydrofuran was added dropwise to the reaction solution. After reacting at -78°C for 30 minutes, the reaction solution was returned to room temperature. Stirring was continued overnight under N2. After the reaction was completed, water was added to the reaction bottle to quench the reaction. After removing the tetrahydrofuran solvent by vacuum distillation, ethyl acetate was added for extraction 3 times, each time 20-30 mL. Finally, the mixture was dried and concentrated to obtain a crude product. The crude product was subjected to column chromatography under the condition of petroleum ether as an eluent, and then recrystallized from n-hexane to obtain 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene. The product was white block crystals with a yield of 60% to 70%. Step 4: Synthesis of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene 2-3 g of 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene, 2-4 mL of 18.4 mol / L sulfuric acid, 6-8 mL of water and 140-160 mL of glacial acetic acid are added into a reaction bottle, and the reaction solution is heated to 60-70° C. Subsequently, 1-2 g of iodine and 0.3-0.4 g of H5IO6 are added to the reaction solution for reaction for 3 h; then the reaction solution is poured into 140-160 mL of water, and sodium carbonate is added to neutralize to a pH of 6-7, and the organic layer is extracted with dichloromethane for 3 times, 30-40 mL each time, and then dried and concentrated to obtain a crude product, and the crude product is subjected to column chromatography under the condition of petroleum ether as an eluent, and then recrystallized with n-hexane to obtain 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene; it is a white block crystal with a yield of 70%-80%; Step 5: Synthesis of auxiliary ligand BTFPO 1-3 g of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene and 3-4 g of triphenylphosphine borate are added to a mixed solvent containing 50-70 mL of toluene and 13-15 mL of isopropanol, and then 0.2-0.5 g of Pd(PPh3)2Cl2 is added to the reaction solution under nitrogen protection, and heated to reflux for 24 hours; after the reaction is completed, the reaction solution is restored to room temperature, 50-60 mL of water is added, extracted with ethyl acetate for 3 times, and the organic layer is dried with Na2SO4 and concentrated to obtain a crude product, and the crude product is subjected to column chromatography under the condition of ethyl acetate as an eluent to obtain a co-ligand BTFPO; it is a white powder with a yield of 80% to 90%. Step 6. Synthesis of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol) Under N2 protection, 1-3 g of 1,2-propylene glycol, 3-4 g of anhydrous potassium carbonate and 5-6 g of 4′-fluoroacetophenone are added to a three-necked flask containing 20-30 mL of N,N-dimethylformamide solvent, the reaction solution is heated to 155°C and the reaction is continued for 19 hours. After the reaction is completed, the reaction solution is cooled to room temperature, the anhydrous potassium carbonate solid is removed by vacuum filtration, and the N,N-dimethylformamide solvent is removed from the remaining solution by vacuum distillation to obtain a crude product. The crude product is recrystallized in methanol solvent to obtain 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol); it is light yellow block crystals with a yield of 70% to 80%; Step 7. Synthesis of ligand L 0.5-0.8g of sodium methoxide and 1.5-2.0g of ethyl trifluoroacetate are added to a round-bottom flask containing 10-20mL of ethylene glycol dimethyl ether solution, and stirred for 10 minutes until the sodium methoxide is completely dissolved, and 1-2g of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol) is added, and stirred at room temperature for 24h; after the reaction is completed, the reaction solution is poured into a beaker containing 100-120mL of ice water, and the pH value of the ice water is adjusted to 2-3 with dilute hydrochloric acid (2mol / L) to obtain a yellow solid, which is filtered and dried naturally, and finally recrystallized in a n-hexane solution to obtain ligand L; it is a yellow needle-shaped crystal with a yield of 70%-80%; Step 8. Synthesis of the complex Eu2L3 Dissolve 0.03-0.05g triethylamine and 0.1-0.3g ligand L in 20-30mL methanol solvent, add 0.50-0.80mmol EuCl3·6H2O, stir for 24 hours, pour the reaction solution into water, filter and dry to obtain the complex Eu2L3; the white precipitate is produced, and the yield is 70%-80%; Step 9: Preparation of photochromic rare earth polymer [Eu2L3(BTFPO)2] n Dissolve 0.1-0.2g Eu2L3 and 0.1-0.2g BTFPO in 20-30mL methanol, stir overnight at 70°C, pour the reaction solution into water, filter and dry to obtain a photochromic rare earth polymer [Eu2L3(BTFPO)2] n ; The yield is 70% to 80%.

3. The method for preparing the photochromic rare earth polymer according to claim 2, characterized in that: In step 1, the volume ratio of glacial acetic acid to chloroform in the mixed solution of glacial acetic acid and chloroform is 1:

1.

4. The method for preparing a photochromic rare earth polymer according to claim 2, characterized in that: The concentration of the sodium thiosulfate solution in step 1 is 0.5 mol / L.

5. The method for preparing the photochromic rare earth polymer according to claim 2, characterized in that: In step 3, the volume ratio of tetrahydrofuran to octafluorocyclopentene is 5:

1.

6. The method for preparing the photochromic rare earth polymer according to claim 2, characterized in that: Step 3: Add ethyl acetate to extract 3 times, adding 20-30 mL of ethyl acetate each time.

7. The method for preparing a photochromic rare earth polymer according to claim 2, characterized in that: Step 4: Extract the organic layer with dichloromethane three times, using 30-40 mL of dichloromethane each time.

8. The method for preparing a photochromic rare earth polymer according to claim 2, characterized in that: Step 5: Extract with ethyl acetate three times, using 20-30 mL of ethyl acetate each time.

9. The use of the photochromic rare earth polymer according to claim 1, characterized in that: The method for preparing an anti-counterfeiting barcode using a photochromic rare earth polymer is carried out according to the following steps:

1. dissolving the photochromic rare earth polymer in tetrahydrofuran solvent to obtain a photochromic rare earth polymer solution; 2. Printing a barcode model on a substrate using 3D printing technology, wherein the recessed area of ​​the barcode model is a filling and molding area of ​​the photochromic rare earth polymer; 3. Filling the photochromic rare earth polymer solution obtained in step 1 into the concave area of ​​the barcode model, curing after irradiation with 350-370nm ultraviolet light for 5-10 minutes to obtain a barcode with photochromic properties; Fourth, the barcode with photochromic properties obtained in step three is placed in an environment with ultraviolet light, and the photochromic rare earth polymer changes color when exposed to light, showing a barcode with complete information that can be read.

10. The use according to claim 9, characterized in that: The concentration of the photochromic rare earth polymer solution in step 1 is 1×10 -5 ~1×10 -2 mol / L.

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