A cellulose-based membrane with hydrophobic and fluorescent properties, and its preparation method and application

Abstract

The present invention belongs to the technical field of anti-counterfeiting films, and specifically discloses a cellulose-based film with hydrophobic and fluorescent properties, a preparation method and application thereof. Biomass-based cellulose is used as a template, and RAFT active sites are introduced on its surface by an esterification method. RAFT polymerization is initiated on the surface in situ to quickly prepare a cellulose-based film with hydrophobic and fluorescent properties in one step. The preparation method is simple, and the raw materials are biodegradable, realizing a new rapid, green and environmentally friendly preparation method. The prepared cellulose-based film has good superhydrophobic properties and aggregation-induced emission properties. It can be introduced onto the surfaces of various substrates by inkjet printing, screen printing, and dip coating methods to construct a multi-mode anti-counterfeiting film with superhydrophobicity and fluorescent properties.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-counterfeiting films, in particular to a cellulose-based film with hydrophobic and fluorescent properties, and a preparation method and application thereof. Background Art

[0002] Counterfeit and substandard products are an inevitable problem associated with commodity transactions. They permeate all industries, severely harming consumer rights and disrupting market order. Therefore, the development and application of anti-counterfeiting technologies are extremely important. Many anti-counterfeiting and information encryption technologies have been widely used in commodities, such as color-changing inks, luminescent patterns, holograms, and watermarks. Among them, fluorescent anti-counterfeiting technology has become one of the most important anti-counterfeiting technologies due to its advantages such as concealment, ease of design and application, and easy identification. In recent years, fluorescent materials such as rare earth complexes, carbon quantum dots, and organic dyes have been developed. However, these materials often suffer from poor photostability, low quantum yield, and high toxicity. In addition, these materials are subject to aggregation-induced quenching, which greatly limits their application at high concentrations and in the solid state. Aggregation-induced emission (AIE) materials, as a new type of fluorescent material, offer advantages such as good photostability, high quantum yield, low toxicity, and easy modification. Most importantly, AIE materials overcome the aggregation-induced quenching problem of traditional fluorescent dyes, making them well suited for use in the solid state or at high concentrations.

[0003] Meanwhile, traditional fluorescent anti-counterfeiting materials primarily focus on a single level of protection, making these measures easily circumvented and counterfeited, which, to a certain extent, limits their further application and development in anti-counterfeiting. Multi-level anti-counterfeiting and information encryption technologies combine multiple anti-counterfeiting and information encryption methods, increasing the complexity of encryption and decryption processes or introducing stimulus-responsive mechanisms to create a solid protective barrier. However, these multi-level anti-counterfeiting materials often present technical complexity and difficulty for consumers to identify. Therefore, anti-counterfeiting materials with multiple advantages, such as multi-level protection, difficulty in counterfeiting, and ease of identification, will have broad application prospects in the anti-counterfeiting and information encryption fields.

[0004] Therefore, developing a simple and rapid method to prepare a temperature-controlled cellulose-based multimodal anti-counterfeiting film with hydrophobic and fluorescent properties has potential application value in the fields of fluorescent multiple anti-counterfeiting and information encryption. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a cellulose-based membrane with hydrophobic and fluorescent properties, and a preparation method and application thereof.

[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing a cellulose-based membrane having hydrophobic and fluorescent properties, comprising the following steps:

[0008] S1, molar ratio (3-30): (3-10): (5-20): 1 Take cellulose, RAFT reagent, dicyclohexylcarbodiimide solution and 4-dimethylaminopyridine, dissolve cellulose, RAFT reagent, and 4-dimethylaminopyridine in an organic solvent, stir in an ice-water bath at 0-10°C for 30 minutes under a nitrogen atmosphere, add dicyclohexylcarbodiimide solution dropwise, continue to react at room temperature for 48 hours, add organic solvent to dilute and filter, evaporate the filtered solution to remove the organic solvent, add it to a sodium bicarbonate solution for precipitation and washing, and then dissolve it in an organic solvent. Repeat this process 3 times, finally wash with deionized water, and place it in a vacuum drying oven to dry to constant weight to obtain a cellulose-based macromolecular RAFT reagent;

[0009] S2, taking a fluorine-containing polymer monomer, an aggregation-induced emission fluorescent polymer monomer, a cellulose-based macromolecular RAFT agent and an initiator in a molar ratio of (100-500): (0.1-25): (0.3-2): 0.1, adding them to a reaction medium, deoxygenating with nitrogen, heating the reaction for 12-24 hours, and after the reaction, adding the reaction solution dropwise to a poor solvent for precipitation three times, and vacuum drying to obtain a cellulose-based graft copolymer;

[0010] S3. Dissolving the cellulose-based graft copolymer in ethanol to form a polymer solution, then coating the polymer solution on the surface of filter paper, and then immersing the filter paper in a poor solvent to induce phase separation, and obtaining a cellulose-based membrane with hydrophobic and fluorescent properties after drying.

[0011] Furthermore, the RAFT agent is a dithioformate or trithioformate compound, and its chemical structure is as follows:

[0012]

[0013] Wherein, R, R1, R2 are leaving groups, and Z is an activating group. Preferably, typical leaving groups include the following groups:

[0014]

[0015] Typical activating groups include aryl, amine, alkoxy and the following groups:

[0016]

[0017] More preferably, the carboxyl-containing trithioformate RAFT agent has the following structural formula:

[0018]

[0019] Wherein, R is an alkane containing 1 to 16 carbon atoms, that is, a saturated chain hydrocarbon.

[0020] More preferably, the R group is an ethyl group (correspondingly, the carboxyl-containing RAFT agent is abbreviated as EDMAT), an octyl group (correspondingly, the carboxyl-containing RAFT agent is abbreviated as ODMAT) or a dodecyl group (correspondingly, the carboxyl-containing RAFT agent is abbreviated as DDMAT), and R' is a benzene ring (correspondingly, the carboxyl-containing RAFT agent is abbreviated as BTPA).

[0021] More preferably, the structural formula of the hydroxyl-containing trithioformate RAFT agent (BHCT) is as follows:

[0022]

[0023] Furthermore, the cellulose is one or more of ethyl cellulose, hydroxypropyl cellulose, microcrystalline cellulose and carboxymethyl cellulose. Preferably, the cellulose is one or both of ethyl cellulose and carboxymethyl cellulose.

[0024] Furthermore, the organic solvent is one or more of tetrahydrofuran, dioxane, N,N-dimethylformamide, toluene and acetone. Preferably, the organic solvent is one or more of tetrahydrofuran, N,N-dimethylformamide and toluene.

[0025] Furthermore, the fluorine-containing polymer monomer is hexafluorobutyl methacrylate, hexafluorobutyl acrylate, dodecafluoroheptyl methacrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, 2,2,3,4,4,4,-hexafluorobutyl acrylate, 2,2,2-trifluoroethyl methacrylate, 3-(perfluoro-5-methylethyl)-2-hydroxypropyl methacrylate, 1,1,2,2-tetrahydroperfluorohexyl methacrylate, 1,1,2,2-tetrahydroperfluoro One or more of decyl methacrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, perfluorododecyl ethyl acrylate, perfluoroalkylpropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, perfluorohexylethylene, perfluorobutylethylene, perfluorododecylethyl methacrylate and 1,1,2,2-tetrahydroperfluorododecyl methacrylate.

[0026] Furthermore, the aggregation-induced emission fluorescent polymer monomer is a tetraphenylethylene derivative, and its structural formula is as follows:

[0027]

[0028] Wherein: the group R is one of vinyl, propenyl, acrylate, methacrylate and acrylamide.

[0029] Furthermore, the initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl hydroperoxide and tert-butyl perbenzoate.

[0030] Furthermore, the poor solvent is one or more of n-hexane, n-heptane, petroleum ether, ethyl acetate and butyl acetate.

[0031] The second technical solution of the present invention is to provide a cellulose-based membrane with hydrophobic and fluorescent properties prepared by the above method.

[0032] The third technical solution of the present invention is to provide an application of a cellulose-based film with hydrophobic and fluorescent properties in the preparation of a multi-mode anti-counterfeiting film. Specifically, after the square mold is heated to 60-150°C, certain information is recorded on the surface of the cellulose-based film with hydrophobic and fluorescent properties, so that the fluorescence intensity of the heated area is enhanced, and the contact angle is changed from a super-hydrophobic state to a hydrophobic state, thereby hiding the encrypted information on the cellulose-based film with hydrophobic and fluorescent properties. The final encrypted information needs to be read separately by two stimuli: 254nm-395nm ultraviolet light (the first key) and water (the second key), thereby realizing multi-stage information encryption and decryption. At the same time, due to the stimulative response of the super-hydrophobic coating of the cellulose-based film with hydrophobic and fluorescent properties to temperature, it can be heated after reading the encrypted information to destroy the second layer of encrypted information, while the first layer of encrypted information is not affected, thereby better encrypting the information.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention uses biomass-based cellulose as a template, introduces RAFT active sites on its surface by esterification, and rapidly prepares a cellulose-based membrane with hydrophobic and fluorescent properties in one step through in situ surface-initiated RAFT polymerization. The preparation method is simple and the raw materials are biodegradable, thus realizing a new rapid, green and environmentally friendly preparation method.

[0035] (2) The cellulose-based film prepared by the present invention has good superhydrophobicity and aggregation-induced emission properties; it can be introduced onto the surface of various substrates through inkjet printing, screen printing, and dip coating methods to construct a multi-mode anti-counterfeiting film with superhydrophobicity and fluorescent properties.

[0036] (3) When the present invention uses a cellulose-based film with hydrophobic and fluorescent properties to prepare a multi-mode anti-counterfeiting film, the surface microstructure of the fluorescent film can be changed by regulating the temperature, thereby regulating its fluorescence intensity and hydrophobic property changes. This characteristic can be used in the fields of multiple anti-counterfeiting and information encryption, which can greatly increase the difficulty of counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 These are fluorescence effect diagrams of the cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) obtained in Example 1 inkjet printed on A4 paper: a is the pattern of the inkjet-printed kitten pattern under 365nm ultraviolet light; b is the pattern of the inkjet-printed kitten pattern under visible light.

[0038] Figure 2 The effect diagram of the superhydrophobic coating constructed by impregnation coating the cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) obtained in Example 2 on filter paper and then inducing phase separation by n-hexane: a is the contact angle coated on the filter paper surface; b is the contact angle of the modified filter paper surface after soaking in the poor solvent n-hexane; c is a picture of the modified filter paper sample under visible light; d is a picture of the modified filter paper sample under ultraviolet light; Figures a1-a4 respectively show the process of easily cleaning the dust on the filter paper surface by dripping water under visible light; b1-b4 respectively show the process of easily cleaning the dust on the filter paper surface by dripping water under ultraviolet light; c1-c4 respectively show the process of the modified filter paper resisting finger friction.

[0039] Figure 3 The cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) obtained in Example 3 was impregnated and coated on filter paper, followed by n-hexane-induced phase separation to construct a superhydrophobic coating. The fluorescent superhydrophobic paper with multiple anti-counterfeiting and information destruction effects was constructed by temperature control.

[0040] Figure 4 A superhydrophobic coating constructed by inkjet printing the cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) obtained in Example 4 on filter paper and then inducing phase separation via n-hexane is shown. The dual information encryption and decryption effects of the fluorescent superhydrophobic paper constructed by temperature control are shown. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] Example 1

[0043] 1) Add ethyl cellulose (EC) (0.7 g) and anhydrous tetrahydrofuran (THF) (50 mL) to a 100 mL single-necked flask and stir to dissolve. Then add DDMAT (0.65 g, 1.79 mmol) and 4-dimethylaminopyridine (0.031 g, 0.26 mmol). After nitrogen bubbling for 30 min, add a solution of dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) in tetrahydrofuran (20 mL) dropwise in an ice-water bath and continue the reaction at room temperature for 48 h. After the reaction is complete, dilute with tetrahydrofuran and filter. The filtered solution is concentrated by rotary evaporation and then added dropwise to an 8% aqueous sodium bicarbonate solution for precipitation and washing. Dissolve in tetrahydrofuran (THF) and then precipitate and wash with an 8% aqueous sodium bicarbonate solution. Repeat this process three times. Finally, rinse with distilled water and dry under vacuum to obtain the EC-DDMAT macro-RAFT agent. The macro-RAFT agent reaction formula is shown below:

[0044]

[0045] 2) EC-DDMAT (0.11 g containing 0.3 mmol of dithio groups), hexafluorobutyl methacrylate (HFBMA) (15.00 g, 60 mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.15 g, 1% wt), and azobisisobutyronitrile (AIBN) (5 mg, 0.03 mmol) were dissolved in 15 mL of dioxane. After nitrogen bubbling for 30 minutes, the mixture was reacted in an oil bath at 75°C for 24 hours. After the reaction, the reaction flask was cooled with ice water and opened to air. The solution was added dropwise to 500 mL of icy n-hexane for precipitation. The precipitation-dissolution-precipitation cycle was repeated three times. The product was dried in a vacuum oven at 40°C to obtain a cellulose-based graft copolymer, EC-gP(HFBMA-co-TPEE). The reaction equation is shown below:

[0046]

[0047] 3) The cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) (5.0 g) was dissolved in ethanol to prepare a polymer solution with a mass concentration of 10%, which was then coated on the paper surface by inkjet printing and applied as a fluorescent anti-counterfeiting agent under 365 nm ultraviolet light; the effect is shown in the figure below. Figure 1 As shown, Figure 1 a and Figure 1 Figure b shows the inkjet-printed kitten pattern under 365nm ultraviolet light and visible light, which exhibits obvious photoluminescence properties and can be used for fluorescent anti-counterfeiting.

[0048] Example 2

[0049] 1) Add ethyl cellulose (EC) (0.7 g) and anhydrous tetrahydrofuran (THF) (50 mL) to a 100 mL single-necked flask and stir to dissolve. Then add DDMAT (0.65 g, 1.79 mmol) and 4-dimethylaminopyridine (0.031 g, 0.26 mmol). After nitrogen bubbling for 30 minutes, add a solution of dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) in tetrahydrofuran (20 mL) dropwise in an ice-water bath and continue the reaction at room temperature for 48 hours. After completion of the reaction, dilute with THF and filter. The filtered solution is concentrated by rotary evaporation and then added dropwise to an 8% aqueous sodium bicarbonate solution for precipitation and washing. Dissolve in THF and then precipitate and wash with an 8% aqueous sodium bicarbonate solution. Repeat this process three times. Finally, rinse with distilled water and dry under vacuum to obtain the EC-DDMAT macro-RAFT agent. The macro-RAFT agent reaction formula is shown below:

[0050]

[0051] 2) EC-DDMAT (0.11 g containing 0.3 mmol of dithio groups), hexafluorobutyl methacrylate (HFBMA) (22.51 g, 90 mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.45 g, 2% wt), and azobisisobutyronitrile (AIBN) (10 mg, 0.06 mmol) were dissolved in 30 mL of dioxane. After nitrogen bubbling for 30 minutes, the mixture was reacted in an oil bath at 75°C for 24 hours. After the reaction, the reaction flask was cooled with ice water and opened to air. The solution was then added dropwise to 500 mL of icy n-hexane for precipitation. The precipitation-dissolution-precipitation cycle was repeated three times. The product was dried in a vacuum oven at 40°C to obtain a cellulose-based graft copolymer, EC-gP(HFBMA-co-TPEE). The reaction equation is shown below:

[0052]

[0053] 3) A cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) (5.0 g) was dissolved in ethanol to prepare a polymer solution with a mass concentration of 10%. The solution was then coated on the surface of the filter paper by dip coating. The solution was then immersed in a poor solvent, n-hexane, to induce phase separation. After drying, a cellulose-based membrane with hydrophobic and fluorescent properties was obtained. The fluorescent hydrophobic properties and self-cleaning properties under 365 nm ultraviolet light were applied. The effect diagram is shown in FIG. Figure 2 As shown by Figure 2 As can be seen from a in the figure, the contact angle of the synthesized polymer applied to the filter paper surface by dip coating is 137.9°, showing hydrophobic properties. Figure 2b in the figure is the contact angle of the modified filter paper surface after being soaked in a poor solvent n-hexane, which is 151.7°, showing superhydrophobic properties. Figure 2 Figures c and d are pictures of the modified filter paper samples under visible light and ultraviolet light. It can be seen from the pictures that the filter paper modified by poor solvent-induced phase separation has superhydrophobicity and photoluminescence properties. Figure 2 a1-a4 and b1-b4 are applications of the self-cleaning properties of the modified filter paper under visible light and ultraviolet light. Dust on the surface of the filter paper can be easily cleaned by adding water, and the filter paper has self-cleaning and photoluminescent properties. Figure 2 C1-c4 in the figure are applications of the finger friction resistance of the modified filter paper. After being rubbed by fingers, the modified filter paper still has super hydrophobic properties.

[0054] Example 3

[0055] 1) Add ethyl cellulose (EC) (0.7 g) and anhydrous tetrahydrofuran (THF) (50 mL) to a 100 mL single-necked flask and stir to dissolve. Then add DDMAT (0.65 g, 1.79 mmol) and 4-dimethylaminopyridine (0.031 g, 0.26 mmol). After nitrogen bubbling for 30 minutes, add a solution of dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) in tetrahydrofuran (20 mL) dropwise in an ice-water bath and continue the reaction at room temperature for 48 hours. After completion of the reaction, dilute with THF and filter. The filtered solution is concentrated by rotary evaporation and then added dropwise to an 8% aqueous sodium bicarbonate solution for precipitation and washing. Dissolve in THF and then precipitate and wash with an 8% aqueous sodium bicarbonate solution. Repeat this process three times. Finally, rinse with distilled water and dry under vacuum to obtain the EC-DDMAT macro-RAFT agent. The macro-RAFT agent reaction formula is shown below:

[0056]

[0057] 2) EC-DDMAT (0.11 g containing 0.3 mmol of dithio groups), hexafluorobutyl methacrylate (HFBMA) (22.51 g, 90 mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.45 g, 2% wt), and azobisisobutyronitrile (AIBN) (10 mg, 0.06 mmol) were dissolved in 30 mL of dioxane. After nitrogen bubbling for 30 minutes, the mixture was reacted in an oil bath at 75°C for 24 hours. After the reaction, the reaction flask was cooled with ice water and opened to air. The solution was then added dropwise to 500 mL of icy n-hexane for precipitation. The precipitation-dissolution-precipitation cycle was repeated three times. The product was dried in a vacuum oven at 40°C to obtain a cellulose-based graft copolymer, EC-gP(HFBMA-co-TPEE). The reaction equation is shown below:

[0058]

[0059] 3) The cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) (5.0g) was dissolved in ethanol to prepare a polymer solution with a mass concentration of 10%, which was coated on the surface of the filter paper by dip coating, and then immersed in a poor solvent n-hexane to induce phase separation. After drying, a cellulose-based membrane with hydrophobic and fluorescent properties was obtained. After heating the square mold to 100°C, certain information was recorded on the surface of the cellulose-based membrane, so that the fluorescence intensity of the heated area was enhanced, and the contact angle was changed from a superhydrophobic state to a hydrophobic state, thereby hiding the encrypted information on the superhydrophobic coating of the cellulose-based membrane. The final encrypted information needs to be read separately through two stimuli: 365nm ultraviolet light (the first key) and water (the second key), thereby achieving multiple anti-counterfeiting. At the same time, due to the stimulative response of the superhydrophobic coating to temperature, it can be heated after reading the encrypted information to destroy the second layer of encrypted information. The effect diagram is as shown Figure 3 As shown, from Figure 3 As can be seen in the figure, the encrypted information recorded by the prepared modified filter paper through the heating module can be verified by two decryption methods: irradiation with ultraviolet light or exposure to water. When both ultraviolet light and underwater decryption methods are used simultaneously, the encrypted information disappears. By changing the viewing angle, the encrypted information reappears, and this property is used to verify the authenticity of the encrypted information. Finally, the encrypted information can be erased by heating, achieving a read-and-burn effect. Based on this characteristic, fluorescent superhydrophobic anti-counterfeiting paper can achieve multiple security measures, increasing the difficulty of counterfeiting.

[0060] Example 4

[0061] 1) Add ethyl cellulose (EC) (0.7 g) and anhydrous tetrahydrofuran (THF) (50 mL) to a 100 mL single-necked flask and stir to dissolve. Then add DDMAT (0.65 g, 1.79 mmol) and 4-dimethylaminopyridine (0.031 g, 0.26 mmol). After nitrogen bubbling for 30 minutes, add a solution of dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) in tetrahydrofuran (20 mL) dropwise in an ice-water bath and continue the reaction at room temperature for 48 hours. After completion of the reaction, dilute with THF and filter. The filtered solution is concentrated by rotary evaporation and then added dropwise to an 8% aqueous sodium bicarbonate solution for precipitation and washing. Dissolve in THF and then precipitate and wash with an 8% aqueous sodium bicarbonate solution. Repeat this process three times. Finally, rinse with distilled water and dry under vacuum to obtain the EC-DDMAT macro-RAFT agent. The macro-RAFT agent reaction formula is shown below:

[0062]

[0063] 2) EC-DDMAT (0.11 g containing 0.3 mmol of dithio groups), hexafluorobutyl methacrylate (HFBMA) (15.00 g, 60 mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.15 g, 1% wt), and azobisisobutyronitrile (AIBN) (5 mg, 0.03 mmol) were dissolved in 15 mL of dioxane. After nitrogen bubbling for 30 minutes, the mixture was reacted in an oil bath at 75°C for 24 hours. After the reaction, the reaction flask was cooled with ice water and opened to air. The solution was added dropwise to 500 mL of icy n-hexane for precipitation. The precipitation-dissolution-precipitation cycle was repeated three times. The product was dried in a vacuum oven at 40°C to obtain a cellulose-based graft copolymer, EC-gP(HFBMA-co-TPEE). The reaction equation is shown below:

[0064]

[0065] 3) The cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) (5.0g) was dissolved in ethanol to prepare a polymer solution with a mass concentration of 10%, which was coated on the surface of the filter paper by inkjet printing, and then immersed in a poor solvent n-hexane to induce phase separation. After drying, a cellulose-based membrane with hydrophobic and fluorescent properties was obtained. After heating the square mold to 100°C, certain information was recorded on the surface of the cellulose-based membrane, so that the fluorescence intensity of the heated area was enhanced, and the contact angle was changed from a superhydrophobic state to a hydrophobic state, thereby hiding the encrypted information on the superhydrophobic coating of the cellulose-based membrane. The final encrypted information needs to be read separately through two stimuli: 365nm ultraviolet light (the first key) and water (the second key), thereby realizing multi-stage information encryption and decryption. At the same time, due to the stimulative response of the superhydrophobic coating of the cellulose-based membrane to temperature, it can be heated after reading the encrypted information to destroy the second layer of encrypted information, while the first layer of encrypted information is not affected, thereby better encrypting the information. The effect diagram is as shown below. Figure 4 As shown, from Figure 4 As shown in the figure, a photoluminescent flower pattern is printed on A4 paper via inkjet printing as message 1. A layer of resin is then dip-coated on top, and a poor solvent is used to induce a superhydrophobic coating. Then, a hot press module is used to create message 2. Under 365nm UV light, the flower pattern of message 1 appears, and when the paper is immersed in water, message 2 appears. The encrypted message is then read using two stimuli: 365nm UV light (the first key) and water (the second key), achieving multi-stage encryption and decryption.

[0066] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a cellulose-based membrane having hydrophobic and fluorescent properties, characterized in that: The following steps are involved: S1, molar ratio (3-30): (3-10): (5-20): 1 Take cellulose, RAFT agent, dicyclohexylcarbodiimide solution and 4-dimethylaminopyridine, dissolve cellulose, RAFT agent and 4-dimethylaminopyridine in an organic solvent, stir at 0-10 ° C in an ice-water bath under a nitrogen atmosphere for 30 minutes, add dicyclohexylcarbodiimide solution dropwise, after the addition is completed, continue to react at room temperature for 48 hours, add organic solvent to dilute and filter, evaporate the filtered solution to remove the organic solvent, add it to a sodium bicarbonate solution for precipitation and washing, and then dissolve it in an organic solvent. Repeat this process 3 times, finally wash with deionized water, and place it in a vacuum drying oven to dry to constant weight to obtain a cellulose-based macromolecular RAFT agent; S2, take the molar ratio of (100-500): (0.1-25): (0.3-2): 0.1% of a fluorine-containing polymer monomer, an aggregation-induced emission fluorescent polymer monomer, a cellulose-based macromolecular RAFT agent, and an initiator are added to the reaction medium, and after nitrogen is passed through to deoxygenate, the reaction is heated for 12-24 hours. After the reaction is completed, the reaction solution is dropwise added to a poor solvent for precipitation three times, and vacuum dried to obtain a cellulose-based graft copolymer. S3. Dissolving the cellulose-based graft copolymer in ethanol to form a polymer solution, then coating the polymer solution on the surface of filter paper, and then immersing the filter paper in a poor solvent to induce phase separation, and obtaining a cellulose-based membrane with hydrophobic and fluorescent properties after drying.

2. The method for preparing a cellulose-based film having hydrophobic and fluorescent properties according to claim 1, wherein: The RAFT agent is a dithioformate or trithioformate compound, and its chemical structure is as follows: Among them, R, R1, R2 are leaving groups, and Z is an activating group.

3. The method for preparing a cellulose-based film having hydrophobic and fluorescent properties according to claim 1, wherein: The cellulose is one or more of ethyl cellulose, hydroxypropyl cellulose, microcrystalline cellulose and carboxymethyl cellulose.

4. The method for preparing a cellulose-based film having hydrophobic and fluorescent properties according to claim 1, wherein: The organic solvent is one or more of tetrahydrofuran, dioxane, N,N-dimethylformamide, toluene and acetone.

5. The method for preparing a cellulose-based film having hydrophobic and fluorescent properties according to claim 1, wherein: The fluorine-containing polymerization monomer is one or more of hexafluorobutyl methacrylate, hexafluorobutyl acrylate, dodecafluoroheptyl methacrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, 2,2,3,4,4,4,-hexafluorobutyl acrylate, 2,2,2-trifluoroethyl methacrylate, 3-(perfluoro-5-methylethyl)-2-hydroxypropyl methacrylate, 1,1,2,2-tetrahydroperfluorohexyl methacrylate, 1,1,2,2-tetrahydroperfluorodecyl methacrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, perfluorododecyl ethyl acrylate, perfluoroalkylpropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, perfluorohexylethylene, perfluorobutylethylene, perfluorododecylethyl methacrylate and 1,1,2,2-tetrahydroperfluorododecyl methacrylate.

6. The method for preparing a cellulose-based film having hydrophobic and fluorescent properties according to claim 1, wherein: The aggregation-induced luminescence fluorescent polymer monomer is a tetraphenylethylene derivative, and its structural formula is as follows: Wherein: the group R is one of vinyl, propenyl, acrylate, methacrylate and acrylamide.

7. The method for preparing a cellulose-based film having hydrophobic and fluorescent properties according to claim 1, wherein: The initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl hydroperoxide and tert-butyl perbenzoate.

8. The method for preparing a cellulose-based film having hydrophobic and fluorescent properties according to claim 1, wherein: The poor solvent is one or more of n-hexane, n-heptane, petroleum ether, ethyl acetate and butyl acetate.

9. A cellulose-based film having hydrophobic and fluorescent properties prepared by the method according to any one of claims 1 to 8.

10. Use of the cellulose-based film having hydrophobic and fluorescent properties as claimed in claim 8 in the preparation of a multi-mode anti-counterfeiting film.

Images