Cellulose-based membrane with hydrophobic and fluorescent properties as well as preparation method and application of cellulose-based membrane

Abstract

The invention belongs to the technical field of anti-counterfeiting films, and particularly discloses a cellulose-based film with hydrophobic and fluorescent properties as well as a preparation method and application of the cellulose-based film. Biomass-based cellulose is taken as a template, RAFT active sites are introduced to the surface of the cellulose-based film by adopting an esterification method, RAFT polymerization is initiated on the surface in situ, and the cellulose-based film with hydrophobic and fluorescent properties is prepared. The preparation method is simple, the raw materials are biodegradable, and a novel rapid and environment-friendly preparation method is realized; the prepared cellulose-based membrane has good super-hydrophobic performance and aggregation-induced emission performance; the super-hydrophobic fluorescent powder can be introduced to the surfaces of various base materials through ink-jet printing, silk-screen printing and dip coating methods to construct a multi-mode anti-counterfeiting film with super-hydrophobicity and fluorescence performance.

Description

Technical Field

[0001] The 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] Many anti-counterfeiting and information encryption technologies have been widely used in commodities, such as color-changing inks, luminous patterns, holograms, watermarks, etc. Among them, fluorescent anti-counterfeiting technology has become one of the most important anti-counterfeiting technologies due to its advantages of concealment, easy 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 have problems such as poor photostability, low quantum yield and high toxicity, and these materials all have aggregation-induced quenching, which greatly limits their application in high concentrations and solid states. Aggregation-induced emission (AIE) materials, as a new type of fluorescent material, have the advantages of good photostability, high quantum yield, low toxicity and easy modification. Most importantly, AIE materials solve the aggregation-induced quenching problem of traditional fluorescent dyes, and can be well used in solid states or high concentrations.

[0003] At the same time, traditional fluorescent anti-counterfeiting materials mainly focus on a single level of anti-counterfeiting, which makes these anti-counterfeiting measures easy to be cracked and forged, which to a certain extent limits their further application and development in anti-counterfeiting. Multiple anti-counterfeiting and information encryption technology integrates multiple anti-counterfeiting and information encryption methods, and builds a solid protection barrier by increasing the complexity of encryption and decryption links, or introducing stimulus response mechanisms. However, these multiple anti-counterfeiting materials often have problems such as complex technology and difficulty for consumers to identify. Therefore, anti-counterfeiting materials with multiple advantages such as multi-level anti-counterfeiting, difficult to forge and easy to identify will have broad application prospects in the field of anti-counterfeiting and information encryption.

[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 field 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 film 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 film having hydrophobic and fluorescent properties, comprising the following steps:

[0008] 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 in an ice-water bath at 0-10°C for 30 minutes under a nitrogen atmosphere, add dicyclohexylcarbodiimide solution drop by drop, continue to react at room temperature for 48 hours after the addition is completed, add an 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, place it in a vacuum drying oven and dry it to constant weight to obtain a cellulose-based macromolecular RAFT agent;

[0009] S2, adding 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 to a reaction medium, passing nitrogen gas to deoxygenate, heating to react for 12-24 hours, and after the reaction is completed, 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 ethyl (correspondingly, the carboxyl-containing RAFT agent is abbreviated as EDMAT), octyl (correspondingly, the carboxyl-containing RAFT agent is abbreviated as ODMAT) or dodecyl (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 shown below:

[0022]

[0023] Further, 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] Further, 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 polymerizable 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 luminescence 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 having 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, and the encrypted information is hidden on the cellulose-based film with hydrophobic and fluorescent properties. The final encrypted information needs to be read 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 initiates RAFT polymerization on the surface in situ to rapidly prepare a cellulose-based membrane with hydrophobic and fluorescent properties in one step. 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 by inkjet printing, screen printing, and dip coating 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 1These are fluorescence effect diagrams of the cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) obtained in Example 1, which was inkjet printed on A4 paper: a is the pattern of the inkjet-printed kitten under 365nm ultraviolet light; b is the pattern of the inkjet-printed kitten 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 surface of the filter paper; b is the contact angle of the modified filter paper surface after soaking in a 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 surface of the filter paper by dripping water under visible light; b1-b4 respectively show the process of easily cleaning the dust on the surface of the filter paper by dripping water under ultraviolet light; c1-c4 respectively show the process of the modified filter paper being resistant to 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 and then constructed by n-hexane-induced phase separation. The fluorescent super-hydrophobic paper with multiple anti-counterfeiting and information destruction effects was constructed by temperature control.

[0040] Figure 4 This is a super-hydrophobic coating constructed by inkjet printing the cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE) obtained in Example 4 on filter paper and then induced phase separation by hexane, and a dual information encryption and decryption effect diagram of the fluorescent super-hydrophobic paper constructed by temperature control. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the 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, 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 dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) tetrahydrofuran (20 mL) solution dropwise under an ice-water bath, and continue to react at room temperature for 48 h. After the reaction is completed, add tetrahydrofuran to dilute and filter, and the filtered solution is concentrated by rotary evaporation, then added dropwise to 8% sodium bicarbonate aqueous solution for precipitation and washing, then dissolved with tetrahydrofuran THF, and then precipitated and washed with 8% sodium bicarbonate aqueous solution. This process is repeated 3 times, and finally washed with distilled water and vacuum dried to obtain EC-DDMAT macromolecular RAFT agent. The reaction formula of the macromolecular RAFT agent is as follows:

[0044]

[0045] 2) EC-DDMAT (0.11g containing 0.3mmol dithio function), hexafluorobutyl methacrylate (HFBMA) (15.00g, 60mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.15g, 1%wt), azobisisobutyronitrile (AIBN) (5mg, 0.03mmol) were dissolved in 15mL dioxane, nitrogen was bubbled for 30min, and then reacted in an oil bath at 75℃ for 24h. After the reaction, the reaction bottle was cooled with ice water and the stopper was opened to ventilate. The solution was added dropwise to 500ml of ice n-hexane for precipitation, and precipitation-dissolution-precipitation was repeated three times. The product was placed in a vacuum drying oven at 40℃ and dried to obtain a cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE). The reaction formula is as follows:

[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 coated on the surface of paper by inkjet printing and applied as a fluorescent anti-counterfeit under 365 nm ultraviolet light; the effect diagram is as follows 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, 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 dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) tetrahydrofuran (20 mL) solution dropwise under an ice-water bath, and continue to react at room temperature for 48 h. After the reaction is completed, add tetrahydrofuran THF to dilute and filter, and the filtered solution is concentrated by rotary evaporation, then added dropwise to 8% sodium bicarbonate aqueous solution for precipitation and washing, then dissolved with tetrahydrofuran THF, and then precipitated and washed with 8% sodium bicarbonate aqueous solution. This process is repeated 3 times, and finally washed with distilled water and vacuum dried to obtain EC-DDMAT macromolecular RAFT agent. The reaction formula of the macromolecular RAFT agent is as follows:

[0050]

[0051] 2) EC-DDMAT (0.11g containing 0.3mmol dithio function), hexafluorobutyl methacrylate (HFBMA) (22.51g, 90mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.45g, 2%wt), azobisisobutyronitrile (AIBN) (10mg, 0.06mmol) were dissolved in 30mL dioxane, nitrogen was bubbled for 30min, and then reacted in an oil bath at 75℃ for 24h. After the reaction, the reaction bottle was cooled with ice water and the stopper was opened to ventilate. The solution was added dropwise to 500ml of ice n-hexane for precipitation, and precipitation-dissolution-precipitation was repeated three times. The product was placed in a vacuum drying oven at 40℃ and dried to obtain a cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE). The reaction formula is as follows:

[0052]

[0053] 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 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. The fluorescent hydrophobic properties and self-cleaning properties under 365 nm ultraviolet light were applied. The effect diagram is as follows Figure 2 As shown by Figure 2 From a in the figure, it can be seen that the contact angle of the synthesized polymer coated on 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 immersed 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 figures that the filter paper modified by poor solvent induced phase separation has superhydrophobic properties and photoluminescence properties. Figure 2 a1-a4 and b1-b4 are the applications of the self-cleaning performance of the modified filter paper under visible light and ultraviolet light. The dust on the surface of the filter paper can be easily cleaned by adding water, and it 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, 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 dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) tetrahydrofuran (20 mL) solution dropwise under an ice-water bath, and continue to react at room temperature for 48 h. After the reaction is completed, add tetrahydrofuran THF to dilute and filter, and the filtered solution is concentrated by rotary evaporation, then added dropwise to 8% sodium bicarbonate aqueous solution for precipitation and washing, then dissolved with tetrahydrofuran THF, and then precipitated and washed with 8% sodium bicarbonate aqueous solution. This process is repeated 3 times, and finally washed with distilled water and vacuum dried to obtain EC-DDMAT macromolecular RAFT agent. The reaction formula of the macromolecular RAFT agent is as follows:

[0056]

[0057] 2) EC-DDMAT (0.11g containing 0.3mmol dithio function), hexafluorobutyl methacrylate (HFBMA) (22.51g, 90mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.45g, 2%wt), azobisisobutyronitrile (AIBN) (10mg, 0.06mmol) were dissolved in 30mL dioxane, nitrogen was bubbled for 30min, and then reacted in an oil bath at 75℃ for 24h. After the reaction, the reaction bottle was cooled with ice water and the stopper was opened to ventilate. The solution was added dropwise to 500ml of ice n-hexane for precipitation, and precipitation-dissolution-precipitation was repeated three times. The product was placed in a vacuum drying oven at 40℃ and dried to obtain a cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE). The reaction formula is as follows:

[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 the square mold was heated 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 stimulatory 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 It can be seen that the encrypted information entered into the prepared modified filter paper through the heating module can be verified by two decryption methods: irradiating ultraviolet light or placing it underwater. When both ultraviolet light and underwater decryption methods are used at the same time, the encrypted information disappears. By changing the viewing angle, the encrypted information reappears, and this feature is used to verify the authenticity of the encrypted information. Finally, the encrypted information can be erased by heating to achieve the effect of burning after reading. Based on this feature, fluorescent super-hydrophobic anti-counterfeiting paper can achieve multiple anti-counterfeiting and increase 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, 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 dicyclohexylcarbodiimide (0.53 g, 2.6 mmol) tetrahydrofuran (20 mL) solution dropwise under an ice-water bath, and continue to react at room temperature for 48 h. After the reaction is completed, add tetrahydrofuran THF to dilute and filter, and the filtered solution is concentrated by rotary evaporation, then added dropwise to 8% sodium bicarbonate aqueous solution for precipitation and washing, then dissolved with tetrahydrofuran THF, and then precipitated and washed with 8% sodium bicarbonate aqueous solution. This process is repeated 3 times, and finally washed with distilled water and vacuum dried to obtain EC-DDMAT macromolecular RAFT agent. The reaction formula of the macromolecular RAFT agent is as follows:

[0062]

[0063] 2) EC-DDMAT (0.11g containing 0.3mmol dithio function), hexafluorobutyl methacrylate (HFBMA) (15.00g, 60mmol), (2-(4-vinylphenyl)ethylene-1,1,2-triyl)triphenyl (TPEE) (0.15g, 1%wt), azobisisobutyronitrile (AIBN) (5mg, 0.03mmol) were dissolved in 15mL dioxane, nitrogen was bubbled for 30min, and then reacted in an oil bath at 75℃ for 24h. After the reaction, the reaction bottle was cooled with ice water and the stopper was opened to ventilate. The solution was added dropwise to 500ml of ice n-hexane for precipitation, and precipitation-dissolution-precipitation was repeated three times. The product was placed in a vacuum drying oven at 40℃ and dried to obtain a cellulose-based graft copolymer EC-gP (HFBMA-co-TPEE). The reaction formula is as follows:

[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 the square mold was heated 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 by 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 follows Figure 4 As shown, from Figure 4 As can be seen in the figure, a photoluminescent flower pattern is printed on A4 paper by inkjet printing as information 1, and then a layer of resin is dipped and coated on the upper layer, and a super hydrophobic coating is constructed by inducing a poor solvent, and then information 2 is constructed by a hot pressing module. Under the irradiation of ultraviolet light 365nm, the flower pattern of information 1 appears, and then it is immersed in water, and information 2 appears. The final encrypted information needs to be read by two stimuli: 365nm ultraviolet light (the first key) and water (the second key), thereby realizing multi-stage information encryption and decryption. .

[0066] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All 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 film 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 in an ice-water bath at 0-10°C for 30 minutes under a nitrogen atmosphere, add dicyclohexylcarbodiimide solution drop by drop, 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, place it in a vacuum drying oven and dry it 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 fluorine-containing polymer monomer, aggregation-induced luminescence fluorescent polymer monomer, cellulose-based macromolecular RAFT agent and 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 added dropwise 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: The fluorine-containing polymerizable 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, characterized in that: 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, characterized in that: 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, characterized in that: The poor solvent is one or more of n-hexane, n-heptane, petroleum ether, ethyl acetate and butyl acetate.

9. A cellulose-based membrane 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 preparing a multi-mode anti-counterfeiting film.

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