A photochromic rare earth polymer, its preparation method and application

Abstract

A photochromic rare earth polymer, its preparation method and application belong to the research field of photochromic anti-counterfeiting materials, and specifically relate to a photochromic rare earth polymer, its preparation method and application. In order to solve the problems faced by existing anti-counterfeiting technologies in practical applications, such as being easily counterfeited, having high costs, and being difficult to visually identify. 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 sourced and inexpensive, effectively reducing the overall cost of the anti-counterfeiting technology and facilitating large-scale production and application. The coloration rate of the photochromic rare earth polymer is <1 second in a strong light environment, and the fading rate is <30 seconds in a weak light environment. The unique optical properties of the rare earth polymer material are derived from its molecular structure and the properties of rare earth elements, making the anti-counterfeiting barcodes prepared from the photochromic rare earth polymer have high security and are difficult to copy.

Description

Technical Field

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

[0002] Anti-counterfeiting barcodes play a crucial role in modern society. They not only effectively protect the rights and interests of consumers, preventing them from purchasing counterfeit and shoddy products, but also help enterprises 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 technology, the manufacturing methods of counterfeit and shoddy products are also constantly evolving, and traditional anti-counterfeiting technologies are difficult to cope with the increasingly complex counterfeiting means. Therefore, there is an urgent need for new and more reliable anti-counterfeiting technologies to ensure the security and reliability of barcodes.

[0003] Currently, the anti-counterfeiting technologies on the market mainly include ink anti-counterfeiting method, laser anti-counterfeiting method, and texture anti-counterfeiting method, etc. However, these anti-counterfeiting technologies all have certain limitations and problems. Although the ink anti-counterfeiting method has a relatively low cost, it is easily counterfeited, and the anti-counterfeiting marks are easily replicated, making it difficult to ensure long-term anti-counterfeiting effects. Although the laser anti-counterfeiting method has good anti-counterfeiting effects, it has a high cost and a long production cycle, and is not easy to be widely promoted and applied on a large scale. Although the texture anti-counterfeiting method has a certain uniqueness, its cost is high and the application range is limited, making it difficult to be popularized in the market. In addition, these traditional anti-counterfeiting technologies are often difficult to be directly recognized by consumers in actual applications, resulting in unsatisfactory anti-counterfeiting effects. Summary of the Invention

[0004] In order to solve the problems of being easily counterfeited, high cost, and difficult to be directly recognized in actual applications faced by existing anti-counterfeiting technologies, the present invention provides a preparation method and an application of a photochromic rare earth polymer.

[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 [Eu2L3(BTFPO)2] n , and the photochromic rare earth polymer is composed of a ligand L, a co-ligand BTFPO, and a rare earth Eu 3+ ;

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

[0009]

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

[0011]

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

[0013] Step 1: Synthesis of 2-methylbenzofuran

[0014] Under the conditions of -78 °C and N2 protection, dissolve 2-3 g of benzofuran in a three-necked flask containing 40-50 mL of anhydrous tetrahydrofuran. After 10-15 minutes, add 15-16 mL of butyllithium. Stir at -78 °C for 20 min, then dropwise add 4-5 mL of iodomethane to the reaction solution, and restore the reaction solution to room temperature; stir at room temperature overnight under N2 protection, then add 0.2 mol / L ammonium chloride aqueous solution to quench butyllithium, then distill off tetrahydrofuran to obtain a crude product, and finally recrystallize and purify the crude product with n-hexane to obtain 2-methylbenzofuran; it is a white granular crystal with a yield of 80% - 90%;

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

[0016] Under the condition of 0 °C, dissolve 5-6 g of 2-methylbenzofuran in a mixed solution of 80-100 mL of glacial acetic acid and chloroform. Add 6-7 g of N-bromosuccinimide in the dark, restore to room temperature, and continuously stir and react for 8 hours. Then add sodium carbonate to the reaction solution to neutralize to pH 6-7, add 30-50 mL of sodium thiosulfate solution to remove bromine, extract the reaction solution with ethyl acetate, dry and concentrate to obtain a crude product, and recrystallize and purify the crude product with n-hexane to obtain 2-methyl-3-bromobenzofuran, which is a colorless crystal 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] Dissolve 9 - 11 g of 2 - methyl - 3 - bromobenzofuran in 120 - 150 mL of dry tetrahydrofuran under - 78 °C and N₂ conditions. After 15 min, add 40 - 50 mL of n - butyllithium dropwise to the reaction solution, stir at - 78 °C for 30 min, then add octafluorocyclopentene diluted with 2 - 4 mL of tetrahydrofuran dropwise to the reaction solution. React at - 78 °C for 30 min, then restore the reaction solution to room temperature, and then continue to stir overnight under N₂ conditions. After the reaction is completed, add water to the reaction flask to quench the reaction; remove the tetrahydrofuran solvent by vacuum distillation, then extract with ethyl acetate 3 times, 20 - 30 mL each time, and finally dry and concentrate to obtain the crude product. The crude product is subjected to column chromatography with petroleum ether as the eluent, and then recrystallized with n - hexane to obtain 1,2 - bis(2 - methyl - 1 - benzofuran - 3 - yl)perfluorocyclopentene; it is a white blocky crystal with a yield of 60% - 70%;

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

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

[0023] Put 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 into the reaction flask, heat the reaction solution to 60 - 70 °C, then add 1 - 2 g of iodine and 0.3 - 0.4 g of H₅IO₆ to the reaction solution and react for 3 h; 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 3 times, 30 - 40 mL each time, and then dry and concentrate to obtain the crude product. The crude product is subjected to column chromatography with petroleum ether as the 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 blocky crystal with a yield of 70% - 80%;

[0024] Step Five: Synthesis of co - 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 are added to a mixed solvent containing 50-70 mL of toluene and 13-15 mL of isopropanol. Then, 0.2-0.5 g of Pd(PPh3)2Cl2 is added to the reaction solution under nitrogen protection, and the mixture is heated under reflux for 24 h. After the reaction is completed, the reaction solution is cooled to room temperature, 50-60 mL of water is added, and the mixture is extracted with ethyl acetate three times, 20-30 mL each time. The organic layer is dried with Na2SO4 and concentrated to obtain a crude product. The crude product is subjected to column chromatography using ethyl acetate as an eluent to obtain the auxiliary ligand BTFPO; it is a white powder with a yield of 80%-90%.

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

[0027] Under N2 protection, 1-3 g of 1,2-propanediol, 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 reacted for 19 hours. After the reaction is completed, the reaction solution is cooled to room temperature, and anhydrous potassium carbonate solid is removed by vacuum filtration. The remaining solution is concentrated under reduced pressure to remove the N,N-dimethylformamide solvent to obtain a crude product. The crude product is recrystallized in methanol solvent to obtain 1,2-bis(4,4′-bis(acetophenoxy)isopropanol); it is a light yellow block crystal with a yield of 70%-80%.

[0028] Step VII. Synthesis of ligand L

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

[0030] Step VIII. Synthesis of complex Eu2L3

[0031] Dissolve 0.03 - 0.05 g of triethylamine and 0.03 - 0.05 g of ligand L in 20 - 30 mL of methanol solvent, add 0.50 - 0.80 mmol of EuCl3·6H2O, stir for 24 hours, then pour the reaction solution into water, filter and dry to obtain the complex Eu2L3; it is a white precipitate produced, and the yield is 70% - 80%;

[0032] Step Nine: Prepare the photochromic rare - earth polymer [Eu2L3(BTFPO)2] n

[0033] Dissolve 0.1 - 0.2 g of Eu2L3 and 0.1 - 0.2 g of BTFPO in 20 - 30 mL of methanol, stir overnight at 70 °C, pour the reaction solution into water, filter and dry to obtain the photochromic rare - earth polymer [Eu2L3(BTFPO)2] n ; the yield is 70% - 80%.

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

[0035] One: Dissolve the photochromic rare - earth polymer in a tetrahydrofuran solvent to obtain a solution of the photochromic rare - earth polymer;

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

[0037] Two: Use 3D printing technology to print a barcode model on a substrate. The sunken area of the barcode model is the filling and molding area for the photochromic rare - earth polymer;

[0038] Three: Fill the solution of the photochromic rare - earth polymer obtained in Step One into the sunken area of the barcode model, and after irradiating with ultraviolet light of 350 - 370 nm for 5 - 10 minutes, cure and mold to obtain a barcode with photochromic properties;

[0039] Four: Place the barcode with photochromic properties obtained in Step Three in an environment with ultraviolet light irradiation. The photochromic rare - earth polymer senses light and changes color, showing a complete barcode whose information can be read;

[0040] While placing the barcode with photochromic properties obtained in Step Four in an environment without ultraviolet light irradiation, the area covered by the rare - earth polymer material is in a light - colored state and cannot display a complete barcode pattern; when scanned with a mobile phone, the barcode information reading fails.

[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 following specific embodiments, and also includes any reasonable combination between specific embodiments.

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

[0051]

[0052] The general structural formula of the photochromic rare earth polymer is [Eu2L3(BTFPO)2] n , and the photochromic rare earth polymer is composed of ligand L, co-ligand BTFPO and rare earth Eu 3+ .

[0053] The structural formula of the co-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 in this embodiment is carried out under relatively mild conditions, which is not only simple and fast but also energy-saving and efficient. The raw materials and reagents are widely sourced and inexpensive, effectively reducing the overall cost of the anti-counterfeiting technology and facilitating large-scale production and application.

[0059] 2. The photochromic rare earth polymer in this embodiment is a helical polymer with a cavity structure composed of two ligands and a metal, which allows the photochromic unit to rotate freely under light irradiation. This structural design effectively solves the problem of limited molecular movement space of the color-changing material in the solid state. In addition, a microporous structure is 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 and thus improving the color-changing performance of the film-forming material.

[0060] The coloration rate of the photochromic rare earth polymer in this embodiment is <1 second in a strong light environment, the fading rate is <30 seconds in a weak light environment, and it has good anti-fatigue properties and can be reused.

[0061] 3. The anti-counterfeiting barcode prepared from the photochromic rare-earth polymer in this embodiment involves dual technical barriers of multi-step complex chemical synthesis and physical processing, forming an innovative defense line that is difficult to replicate. Its uniqueness lies in the application of the photochromic principle, which is based on the scientific phenomenon of color change in rare-earth materials under specific ultraviolet light irradiation, endowing the anti-counterfeiting barcode with extremely high security and technical characteristics that are difficult to replicate, 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, due to the unique optical properties of the rare-earth polymer material originating from its molecular structure and the properties of rare-earth elements, ordinary photographing and printing cannot reproduce these material properties, making the anti-counterfeiting barcode prepared from the photochromic rare-earth polymer highly secure and difficult to replicate.

[0062] 4. The principle of the anti-counterfeiting barcode prepared from the photochromic rare-earth polymer in this embodiment is that the barcode pattern does not appear completely in the absence of ultraviolet light, and only appears completely under ultraviolet light irradiation, forming a dynamic anti-counterfeiting effect. This characteristic facilitates the intuitive identification and verification of barcode information, greatly improving the recognizability and usability of the anti-counterfeiting mark.

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

[0064] Step 1: Synthesis of 2-methylbenzofuran

[0065] Under the conditions of -78°C and N2 protection, dissolve 2-3 g of benzofuran in a three-necked flask containing 40-50 mL of anhydrous tetrahydrofuran. After 10-15 minutes, add 15-16 mL of butyllithium, stir at -78°C for 20 min, then dropwise add 4-5 mL of iodomethane to the reaction solution, and restore the reaction solution to room temperature; stir at room temperature overnight under N2 protection, then add 0.2 mol / L ammonium chloride aqueous solution to quench the butyllithium, then distill off the tetrahydrofuran to obtain a crude product, and finally recrystallize and purify the crude product with n-hexane to obtain 2-methylbenzofuran; it is a white granular crystal with a yield of 80%-90%;

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

[0067] Under the condition of 0 °C, dissolve 5-6 g of 2-methylbenzofuran in a mixed solution of 80-100 mL of glacial acetic acid and chloroform. Add 6-7 g of N-bromosuccinimide in the dark, restore to room temperature, and continuously stir the reaction for 8 hours. Then, add sodium carbonate to the reaction solution to neutralize it to pH 6-7. Add 30-50 mL of sodium thiosulfate solution to remove bromine. Extract the reaction solution with ethyl acetate, dry and concentrate it to obtain the crude product. Recrystallize and purify the crude product with n-hexane to obtain 2-methyl-3-bromobenzofuran, which is a colorless crystal with a yield of 85%-95%;

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

[0069] Under the conditions of -78 °C and N2, dissolve 9-11 g of 2-methyl-3-bromobenzofuran in 120-150 mL of dry tetrahydrofuran. After 15 minutes, dropwise add 40-50 mL of n-butyllithium to the reaction solution, stir at -78 °C for 30 minutes, then dropwise add octafluorocyclopentene diluted with 4-5 mL of tetrahydrofuran to the reaction solution. After reacting at -78 °C for 30 minutes, restore the reaction solution to room temperature, and then continue to stir overnight under N2. After the reaction is completed, add water to the reaction flask to quench the reaction; After removing the tetrahydrofuran solvent by vacuum distillation, extract with ethyl acetate 3 times, 20-30 mL each time, and finally dry and concentrate to obtain the crude product. The crude product is subjected to column chromatography with petroleum ether as the eluent, and then recrystallized with n-hexane to obtain 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene; it is a white block crystal with a yield of 60%-70%;

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

[0071] Put 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 into the reaction flask. Heat the reaction solution to 60-70 °C, and then add 1-2 g of iodine and 0.3-0.4 g of H5IO6 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 it to pH 6-7, extract the organic layer with dichloromethane 3 times, 30-40 mL each time, and then dry and concentrate to obtain the crude product. The crude product is subjected to column chromatography with petroleum ether as the 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%;

[0072] Step 5: Synthesis of co-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 are added to a mixed solvent containing 50 - 70 mL of toluene and 13 - 15 mL of isopropanol. Then, 0.2 - 0.5 g of Pd(PPh3)2Cl2 is added to the reaction solution under nitrogen protection, and the mixture is heated under reflux for 24 h. After the reaction is completed, the reaction solution is cooled to room temperature, 50 - 60 mL of water is added, and the mixture is extracted with ethyl acetate three times. The organic layer is dried with Na2SO4 and concentrated to obtain a crude product. The crude product is subjected to column chromatography using ethyl acetate as the eluent to obtain the auxiliary ligand BTFPO; it is a white powder, and the yield is 80% - 90%.

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

[0075] Under N2 protection, 1 - 3 g of 1,2 - propanediol, 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 reacted for 19 hours. After the reaction is completed, the reaction solution is cooled to room temperature, and anhydrous potassium carbonate solid is removed by vacuum filtration. The remaining solution is distilled under reduced pressure to remove the N,N - dimethylformamide solvent 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 a light yellow block - shaped crystal, and the yield is 70% - 80%.

[0076] Step Seven: Synthesis of Ligand L

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

[0078] Step Eight: Synthesis of Complex Eu2L3

[0079] Dissolve 0.03 - 0.05 g of triethylamine and 0.1 - 0.3 g of ligand L in 20 - 30 mL of methanol solvent, add 0.50 - 0.80 mmol of EuCl3·6H2O, stir for 24 hours, then pour the reaction solution into water, filter and dry to obtain the complex Eu2L3; it is a white precipitate produced, and the yield is 70% - 80%;

[0080] Step Nine: Prepare the photochromic rare - earth polymer [Eu2L3(BTFPO)2] n

[0081] Dissolve 0.1 - 0.2 g of Eu2L3 and 0.1 - 0.2 g of BTFPO in 20 - 30 mL of methanol, stir overnight at 70 °C, pour the reaction solution into water, filter and dry to obtain the photochromic rare - earth polymer [Eu2L3(BTFPO)2] n ; the yield is 70% - 80%.

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

[0083] 2. The photochromic rare - earth polymer in this embodiment is a helical polymer with a hole structure composed of two ligands and a metal, which enables the photochromic unit to rotate freely under light irradiation. This structural design effectively solves the problem of limited molecular motion space of the color - changing material in the solid state. In addition, a microporous structure is 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 and thus improving the color - changing performance of the film - forming material.

[0084] The color - forming rate of the photochromic rare - earth polymer in this embodiment is < 1 second in a strong - light environment, the fading rate is < 30 seconds in a weak - light environment, and it has good anti - fatigue properties 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. Dissolve the photochromic rare earth polymer in a tetrahydrofuran solvent to obtain a solution of the photochromic rare earth polymer.

[0095] 2. Use 3D printing technology to print a bar code model on a substrate. The sunken area of the bar code model is the filling and molding area for the photochromic rare earth polymer.

[0096] 3. Fill the solution of the photochromic rare earth polymer obtained in step 1 into the sunken area of the bar code model, and cure and form it after irradiating with ultraviolet light of 350 - 370 nm for 5 - 10 minutes to obtain a bar code with photochromic properties.

[0097] 4. Place the bar code with photochromic properties obtained in step 3 in an environment with ultraviolet light irradiation. The photochromic rare earth polymer is photosensitive and changes color, showing a bar code with complete information that can be read.

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

[0099] 2. The photochromic rare earth polymer in this embodiment is a helical polymer with a cavity structure composed of two ligands and a metal, which enables the photochromic unit to rotate freely under light irradiation. This structural design effectively solves the problem of limited molecular motion space of the color - changing material in the solid state. In addition, a microporous structure is 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 and thus improving the color - changing performance of the film - forming material.

[0100] The color - forming rate of the photochromic rare earth polymer in this embodiment is < 1 second in a strong light environment, the fading rate is < 30 seconds in a weak light environment, and it has good anti - fatigue properties 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 [Eu2L3(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] Under the conditions of -78 °C and N2 protection, dissolve 2.55 g of benzofuran in a three-necked flask containing 50 mL of anhydrous tetrahydrofuran. After 10 minutes, add 15.14 mL of butyllithium, stir at -78 °C for 20 min, then dropwise add 4.65 mL of methyl iodide to the reaction solution, and restore the reaction solution to room temperature. Stir at room temperature overnight under N2 protection, then add 0.2 mol / L ammonium chloride aqueous solution to the reaction solution to quench butyllithium, then distill off tetrahydrofuran to obtain a crude product, and finally recrystallize and purify the crude product with n-hexane to obtain 2-methylbenzofuran; it is a white granular crystal with a yield of 87%;

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

[0116] Under the condition of 0 °C, dissolve 5.0 g of 2-methylbenzofuran in a mixed solution of 80 mL of glacial acetic acid and chloroform, add 6.6 g of N-bromosuccinimide in the dark, restore to room temperature, continuously stir and react for 8 hours, then add sodium carbonate to the reaction solution to neutralize to pH 7, add 50 mL of sodium thiosulfate solution to remove bromine, extract the reaction solution with ethyl acetate, dry and concentrate to obtain a crude product, and recrystallize and purify the crude product with n-hexane to obtain 2-methyl-3-bromobenzofuran, which is a colorless crystal 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] Under the conditions of -78 °C and N2, dissolve 10.0 g of 2-methyl-3-bromobenzofuran in 150 mL of dry tetrahydrofuran. After 15 min, dropwise add 43.2 mL of n-butyllithium to the reaction solution, stir at -78 °C for 30 min, dropwise add octafluorocyclopentene diluted with 3 mL of tetrahydrofuran to the reaction solution, react at -78 °C for 30 min, then restore the reaction solution to room temperature, and then continue to stir overnight under N2 conditions. After the reaction is completed, add water to the reaction flask to quench the reaction; after distilling off the tetrahydrofuran solvent under reduced pressure, extract with ethyl acetate 3 times, 30 mL each time, and finally dry and concentrate to obtain a crude product. The crude product is subjected to column chromatography with petroleum ether as the eluent, and then recrystallized with n-hexane to obtain 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene; it is a white massive crystal with a yield of 60.7%;

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

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

[0123] Put 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 into the reaction flask, heat the reaction solution to 65 °C, and then add 1.2 g of iodine and 0.39 g of H5IO6 to the reaction solution for reaction for 3 h; 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 carry out drying and concentration to obtain the crude product. The crude product is subjected to column chromatography under the condition of petroleum ether as the 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 blocky crystal with a yield of 75%;

[0124] Step 5. Synthesis of the auxiliary ligand BTFPO

[0125] Put 2.0 g of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene and 3.36 g of triphenylphosphine borate into a mixed solvent containing 60 mL of toluene and 14 mL of isopropanol, and then add 0.3 g of Pd(PPh3)2Cl2 to the reaction solution under nitrogen protection, and heat to reflux for 24 h; after the reaction is completed, restore the reaction solution to room temperature, add 50 mL of water, extract with ethyl acetate 3 times, 30 mL each time, and dry the organic layer with Na2SO4, and concentrate to obtain the crude product. The crude product is subjected to column chromatography under the condition of ethyl acetate as the eluent to obtain the auxiliary ligand BTFPO; it is a white powder with a yield of 84%.

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

[0127] Under N2 protection, put 1.0 g of 1,2-propanediol, 3.63 g of anhydrous potassium carbonate and 5.4 g of 4′-fluoroacetophenone into a three-necked flask equipped with 20 mL of N,N-dimethylformamide solvent, heat the reaction solution to 155 °C and continue the reaction for 19 hours. After the reaction is completed, cool the reaction solution to room temperature, filter off the anhydrous potassium carbonate solid by vacuum filtration, and remove the N,N-dimethylformamide solvent from the remaining solution by vacuum distillation to obtain the crude product. The crude product is recrystallized in methanol solvent to obtain 1,2-bis(4,4′-bis(acetophenoxy)isopropanol); it is a light yellow blocky crystal with a yield of 70%;

[0128] Step 7: Synthesis of ligand L

[0129] Add 0.69 g of sodium methoxide and 1.82 g of ethyl trifluoroacetate to a round-bottom flask containing 10 mL of ethylene glycol dimethyl ether solution, stir for 10 minutes until the sodium methoxide is completely dissolved, add 1.0 g of 1,2-bis(4,4′-bis(acetylphenoxy)isopropanol), and stir at room temperature for 24 h; after the reaction is completed, pour the reaction solution into a beaker containing 100 mL of ice water, adjust the pH value of the ice water to 3 with dilute hydrochloric acid (2 mol / L) to obtain a yellow solid, filter by suction and air-dry naturally, and finally recrystallize in n-hexane solution to obtain ligand L; it is a yellow needle crystal with a yield of 75%;

[0130] Step 8: Synthesis of complex Eu2L3

[0131] Dissolve 0.05 g of triethylamine and 0.2 g of ligand L in 30 mL of methanol solvent, add 0.80 mmol of EuCl3·6H2O, stir for 24 hours, then pour the reaction solution into water, filter and dry to obtain complex Eu2L3; it is a white precipitate produced with a yield of 80%;

[0132] Step 9: Preparation of photochromic rare earth polymer [Eu2L3(BTFPO)2] n

[0133] Dissolve 0.1 g of Eu2L3 and 0.11 g of BTFPO in 20 mL of methanol, stir overnight at 70 °C, pour the reaction solution into water, filter and dry to obtain the photochromic rare earth polymer [Eu2L3(BTFPO)2] n ; the yield is 68%.

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

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

[0136] II. Use 3D printing technology to print a bar code model on the substrate, and the sunken area of the bar code model is the filling and molding area of the photochromic rare earth polymer;

[0137] III. Fill the solution of the photochromic rare earth polymer obtained in step I into the sunken area of the bar code model, irradiate with ultraviolet light of 365 nm for 10 minutes and then cure and mold to obtain a bar code with photochromic properties;

[0138] IV. Place the bar code with photochromic properties obtained in Step III in an environment irradiated with ultraviolet light. The photochromic rare earth polymer undergoes photochromism, and a bar code with complete information that can be read is displayed;

[0139] While placing the bar code with photochromic properties obtained in Step IV in an environment without ultraviolet light irradiation, the area covered by the rare earth polymer material is in a light color state, and the complete bar code pattern cannot be displayed; the bar code information fails to be read when scanned with a mobile phone; Figure 1 It is a picture of the bar code with photochromic properties in Example 1 under natural light irradiation; Figure 1 In it, a is the sunken area, and the photochromic rare earth polymer solution inside has been solidified and formed; Figure 2 It is a picture of the bar code with photochromic properties in Example 1 under ultraviolet light irradiation; it can be seen that the bar code pattern can be completely displayed under ultraviolet light irradiation, forming a dynamic anti-counterfeiting effect.

Claims

1. A method for preparing a photochromic rare earth polymer, characterized in that: The structural formula of the 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: ； 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 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, and 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. Under N2 protection, the mixture was stirred at room temperature overnight, and then 0.2 mol / L aqueous ammonium chloride solution was added to the reaction solution to quench the butyl lithium. Then, tetrahydrofuran was removed by distillation to obtain a crude product. Finally, the crude product was recrystallized and purified with n-hexane to obtain 2-methylbenzofuran. It was white granular crystals with a yield of 80%-90%. Step 2: Synthesis of 2-methyl-3-bromobenzofuran At 0°C, 5-6 g of 2-methylbenzofuran was dissolved in a mixed solution of 80-100 mL of glacial acetic acid and chloroform, 6-7 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 6-7, 30-50 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 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 min, 40-50 mL of n-butyl lithium was added dropwise to the reaction solution. The mixture was stirred at −78 °C for 30 min. 4-5 mL of octafluorocyclopentene diluted with tetrahydrofuran was added dropwise to the reaction solution. After reacting at −78 °C for 30 min, the reaction solution was returned to room temperature and then stirred 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 the 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%-70%. The volume ratio of tetrahydrofuran to octafluorocyclopentene in step 3 is 5:1; Step 4: Synthesis of 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene 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 were added into the reaction bottle, and the reaction solution was heated to 60-70°C, and then 1-2 g iodine and 0.3-0.4 g H5IO6 were added to the reaction solution for 3 h; then the reaction solution was poured into 140-160 mL water, and sodium carbonate was added to neutralize to pH 6-7, and the organic layer was 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 was subjected to column chromatography under the condition of petroleum ether as the eluent, and then recrystallized with n-hexane to obtain 1,2-bis(6-iodo-2-methyl-1-benzofuran-3-yl)hexafluorocyclopentene; it was white block crystals 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 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(PPh3)2Cl2 was added to the reaction solution under nitrogen protection, and heated to reflux for 24 h; after the reaction was completed, the reaction solution was restored to room temperature, 50-60 mL of water was added, and extracted with ethyl acetate for 3 times, and the organic layer was dried with Na2SO4 and concentrated to obtain a crude product, and the crude product was subjected to column chromatography under the condition of ethyl acetate as the eluent to obtain the auxiliary ligand BTFPO; it was a white powder with a yield of 80%-90%; Step 6. Synthesis of 1,2-bis(4,4ʹ-bis(acetylphenoxy)isopropanol) Under N2 protection, 1-3 g 1,2-propylene glycol, 3-4 g anhydrous potassium carbonate and 5-6 g 4′-fluoroacetophenone were added to a three-necked flask containing 20-30 mL N,N-dimethylformamide solvent, and the reaction solution was heated to 155°C and continued to react for 19 hours. After the reaction, 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(4,4ʹ-bis(acetylphenoxy)isopropanol); it was light yellow block crystals with a yield of 70%-80%. Step 7. Synthesis of ligand L Add 0.5-0.8 g of sodium methoxide and 1.5-2.0 g of ethyl trifluoroacetate to a round-bottom flask containing 10-20 mL of ethylene glycol dimethyl ether solvent, stir for 10 minutes until all the sodium methoxide is dissolved, add 1-2 g of 1,2-bis(4, 4ʹ-bis(acetylphenoxy)isopropanol), and stir at room temperature for 24 h; after the reaction, pour the reaction solution into a beaker containing 100-120 mL of ice water, adjust the pH value of the ice water to 2-3 with 2 mol / L dilute hydrochloric acid, and obtain a yellow solid. After suction filtration and natural drying, recrystallize from n-hexane solution to obtain ligand L; it is yellow needle-shaped crystals with a yield of 70%-80%; Step 8. Synthesis of the complex Eu2L3 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 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 0.1-0.2 g Eu2L3 and 0.1-0.2 g BTFPO in 20-30 mL methanol, stir overnight at 70 °C, pour the reaction solution into water, filter and dry to obtain the photochromic rare earth polymer [Eu2L3(BTFPO)2] n ; The yield is 70%~80%.

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

1.

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

4. The method for preparing a photochromic rare earth polymer according to claim 1, characterized in that: Step 5: Extract with ethyl acetate three times, using 20-30 mL of ethyl acetate each time.

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