Force-induced color-changing material as well as preparation method and application thereof

Abstract

The invention discloses a mechanochromic material as well as a preparation method and application thereof. The mechanochromic material comprises a base material and mechanochromic molecules bonded on the base material. According to the invention, the mechanochromic molecules are grafted into a semi-rigid polysaccharide polymer structure through chemical bonds, so that the uniform dispersion of the molecular level is ensured, the sensitivity, contrast ratio and uniformity of mechanochromism are remarkably improved, and meanwhile, the excellent mechanical properties, excellent processability and excellent environmental adaptability of a matrix polymer are inherited and maintained; various forms such as films, coatings, fibers, microspheres or micelles can be prepared.

Description

Technical Field

[0001] This invention relates to the field of tobacco anti-counterfeiting technology, specifically to a mechanochromic material, its preparation method, and its application. Background Technology

[0002] Faced with increasingly serious problems of counterfeiting and illegal unpacking, tobacco packaging anti-counterfeiting technology urgently needs new breakthroughs. Traditional anti-counterfeiting methods, such as special textured paper, laser holographic labels, and color-changing ink printing, rely heavily on static visual features. Their anti-counterfeiting information is easily forged using high-precision replication technology, making them ineffective against increasingly sophisticated counterfeiting methods. Furthermore, traditional anti-counterfeiting methods lack the ability to monitor the integrity of the packaging. Criminals can counterfeit genuine products by undamaging the packaging, replacing the contents, and resealing it. Consumers cannot visually detect whether the packaging has been illegally tampered with, allowing counterfeit cigarettes to enter the market through legitimate packaging, seriously damaging consumer health and corporate brand reputation.

[0003] Mechanochromic compounds, as a novel intelligent anti-counterfeiting material, can systematically solve the inherent defects of traditional cigarette anti-counterfeiting technologies due to their unique mechanical response color-changing properties. When these compounds are subjected to external forces (such as tearing, squeezing, or friction during unpacking), their molecular structure undergoes reversible or irreversible changes, affecting light absorption and reflection characteristics, and thus triggering a visible color change. This color-changing process is directly related to the action of mechanical force and possesses excellent dynamics, uniqueness, and difficulty in replication.

[0004] Irreversible mechanochromic materials are applied to the sealing interfaces, anti-counterfeiting label areas, or packaging film materials of tobacco packaging. When the packaging is opened, the color changes irreversibly due to external force, visually indicating that the packaging has been tampered with. Consumers can quickly determine the authenticity of the packaging and the product by observing the color difference without any tools, effectively preventing illegal tampering and counterfeiting. Compared to traditional static anti-counterfeiting features, the anti-counterfeiting mechanism of mechanochromic compounds is based on molecular-level structural changes. Its synthesis process and color-changing conditions require precise control, making it difficult for counterfeiters to imitate through conventional means, fundamentally raising the threshold of anti-counterfeiting technology. In addition, this material can be deeply integrated with packaging materials to form an integrated solution with both anti-counterfeiting and anti-tampering functions. It can visually reveal the opened state of the packaging through color changes and construct an uncopyable anti-counterfeiting label with its unique color-changing logic, effectively blocking counterfeiters from using genuine packaging for secondary processing, and building a full-chain protection system for tobacco products from production to distribution. Summary of the Invention

[0005] One objective of this invention is to provide a new technical solution for a mechanochromic material that combines high color-changing sensitivity with excellent processing performance.

[0006] According to a first aspect of the present invention, a mechanochromic material is provided, comprising a matrix material and mechanochromic molecules bonded to the matrix material, wherein the matrix material is selected from at least one of starch, chitosan, dextran, chitin, lignin, cellulose, microcrystalline cellulose, cellulose ester, and cellulose ether, and the mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole, and diarylacrylonitrile, and the degree of substitution of the mechanochromic molecule is 0.001-1.

[0007] According to a second aspect of the present invention, a method for preparing a mechanochromic material is provided, comprising the following steps:

[0008] (1) Dissolve and disperse the matrix material in a solvent to obtain a homogeneous solution of the matrix material;

[0009] (2) Add a catalyst and an acylation reagent with mechanochromic molecules or an etherification reagent with mechanochromic molecules to a homogeneous solution and carry out the reaction;

[0010] (3) Pour the solution after the reaction into the precipitant to precipitate the solid product, wash and dry it to obtain the metronidizer material.

[0011] Optionally, the solvent in step (1) is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, chloroform, pyridine, N-methylpyrrolidone and ionic liquid.

[0012] Optionally, the mass percentage concentration of the matrix material in the homogeneous solution in step (1) is 0.5-20%.

[0013] Optionally, the catalyst in step (2) is selected from at least one of 4-dimethylaminopyridine, dicyclohexylcarbodiimide, N,N'-carbonyldiimidazole, triethylamine, imidazole, pyridine, benzotriazole, sodium hydroxide and alumina;

[0014] The acylation reagent having a mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole and diarylacrylonitrile with a carboxylic acid, acid anhydride or acyl halide group.

[0015] The etherifying agent having a mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole, and diarylacrylonitrile, which have epoxy groups or haloalkyl groups.

[0016] Optionally, the mass ratio of the catalyst to the acylation reagent with mechanochromic molecules or the etherification reagent with mechanochromic molecules in step (2) is 1:1 to 1:200.

[0017] Optionally, the mass ratio of the matrix material to the acylation reagent with mechanochromic molecules or the etherification reagent with mechanochromic molecules is 1:0.001-1:2.

[0018] Optionally, the acylation reaction in step (2) is carried out at a temperature of 40-200℃ and a reaction time of 1-72h, and the etherification reaction is carried out at a temperature of 30-200℃ and a reaction time of 1-72h.

[0019] Optionally, the precipitant in step (3) is at least one of water and alcohol.

[0020] According to a third aspect of the present invention, an application of the mechanochromic material described herein in anti-counterfeiting of tobacco packaging is provided.

[0021] This invention grafts mechanochromic molecules into a semi-rigid polysaccharide polymer structure via chemical bonds, ensuring uniform dispersion at the molecular level and significantly improving the sensitivity, contrast, and uniformity of mechanochromic reactions. At the same time, it inherits and maintains the excellent mechanical properties of the matrix polymer itself, as well as its excellent processing performance and environmental adaptability. It can be prepared into various forms such as films, coatings, fibers, microspheres, or micelles.

[0022] The electrochromic material of this invention is applied to tobacco packaging anti-counterfeiting. Under normal conditions, the material is deeply integrated with the packaging, and it permanently changes color under external force, creating a one-time anti-counterfeiting verification mechanism and enhancing the anti-counterfeiting effect. Specifically, the material is transparent under normal conditions, but changes color upon being triggered by external force. The opened state of the packaging can be visually determined without the need for detection tools, combining concealment and ease of verification. This aligns with consumer habits and helps increase consumer trust. The anti-tampering requirements of tobacco packaging and the "physical damage reveals counterfeit" characteristic of the electrochromic material are highly compatible. The combination of the two forms an active anti-counterfeiting barrier, solving the pain points of static and easily replicated traditional technologies and meeting the industry's demand for high-end anti-counterfeiting technology.

[0023] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0025] Figure 1 The infrared spectrum is shown for the spiropyran-containing cellulose acetate derivative prepared in Example 6.

[0026] Figure 2 The image shows the UV-Vis absorption spectrum of the spiropyran-containing cellulose acetate membrane prepared in Example 10 before stretching.

[0027] Figure 3 The image shows the UV-Vis absorption spectrum of the stretched region of the spiropyran-containing cellulose acetate membrane prepared in Example 10.

[0028] Figure 4 These are photographs of the cellulose acetate membrane containing spiropyran prepared in Example 10 before and after stretching.

[0029] Figure 5 This is a schematic diagram of the anti-counterfeiting design of cellulose acetate containing spiropyran prepared in Example 10. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0031] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0032] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0033] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0034] The mechanochromic material provided by this invention includes a matrix material and mechanochromic molecules bonded to the matrix material. The matrix material is selected from at least one of starch, chitosan, dextran, chitin, lignin, cellulose, microcrystalline cellulose, cellulose ester, and cellulose ether. The mechanochromic molecules are selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole, and diarylacrylonitrile. The degree of substitution of the mechanochromic molecules is 0.001-1.

[0035] The matrix material is at least one of biomass polysaccharides. More specifically, the matrix material can be at least one of starch, chitosan, dextran, chitin, lignin, cellulose, microcrystalline cellulose, cellulose ester, and cellulose ether. Lignin can be selected from at least one of alkaline lignin, sulfate lignin, solvent lignin, acid-hydrolyzed lignin, and enzymatic lignin. Cellulose ester can be selected from at least one of cellulose acetate, cellulose acetate butyrate, cellulose propionate, cellulose butyrate, cellulose nitrate, cellulose sulfate, cellulose benzoate, and cellulose cinnamate. Cellulose ether can be selected from at least one of methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose.

[0036] The degree of substitution of metronic molecules in metronic materials is preferably 0.01-0.5.

[0037] The method for preparing a mechanochromic material provided by the present invention includes the following steps:

[0038] (1) Dissolve and disperse the matrix material in a solvent to obtain a homogeneous solution of the matrix material.

[0039] The solvent in step (1) is selected from at least one of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), acetone, chloroform, pyridine, N-methylpyrrolidone and ionic liquid.

[0040] The ionic liquid can be an organic molten salt with a melting point below 100°C, formed by a cation and anion. The cation of the ionic liquid is selected from any of the following: 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-allyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, N-ethylpyridine cation, N-butylpyridine cation, and N-hexylpyridine cation. Preferably, the cation of the ionic liquid is selected from any of the following: 1-ethyl-3-methylimidazolium cation, 1-allyl-3-methylimidazolium cation, and 1-butyl-3-methylimidazolium cation. The anion of the ionic liquid is selected from any of the following: chloride ion, bromide ion, formate ion, acetate ion, propionate ion, butyrate ion, and methyl phosphate ion. Preferably, the anion of the ionic liquid is selected from any of the following: chloride ion, formate ion, acetate ion, and methyl phosphate ion.

[0041] For polysaccharides such as cellulose, starch, chitosan, and chitin, ionic liquids are preferred as solvents. For cellulose derivatives, such as cellulose acetate, at least one of DMSO, DMF, DMAc, THF, acetone, chloroform, pyridine, and N-methylpyrrolidone is preferred as a solvent. Solvents can be used alone or in combination.

[0042] Ionic liquids can be single ionic liquids or mixed ionic liquids. A single ionic liquid can be an ionic liquid that can dissolve polysaccharides such as cellulose, starch, chitosan, and chitin. A mixed ionic liquid can consist entirely of ionic liquids that can dissolve polysaccharides such as cellulose, starch, chitosan, and chitin, or it can be a mixture of ionic liquids that can dissolve polysaccharides such as cellulose, starch, chitosan, and chitin and ionic liquids that cannot dissolve polysaccharides such as cellulose, starch, chitosan, and chitin.

[0043] The cosolvent is selected from at least two of the above-mentioned ionic liquids and organic solvents. For example, the cosolvent may be a cosolvent formed from at least two of the ionic liquids; a cosolvent formed from at least two of the organic solvents; or a cosolvent formed from at least one of the ionic liquids and at least one of the organic solvents.

[0044] The mass percentage concentration of the matrix material in the homogeneous solution in step (1) is 0.5-20%, preferably 1-5%.

[0045] (2) Add a catalyst and an acylation reagent with mechanochromic molecules or an etherification reagent with mechanochromic molecules to a homogeneous solution and carry out the reaction.

[0046] The catalyst in step (2) is selected from at least one of 4-dimethylaminopyridine (DMAP), dicyclohexylcarbodiimide (DCC), N,N'-carbonyldiimidazole (CDI), triethylamine, imidazole, pyridine, benzotriazole, sodium hydroxide and alumina.

[0047] The acylation reagent having a mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole, and diarylacrylonitrile, which have a carboxylic acid, acid anhydride, or acyl halide group.

[0048] The etherifying agent having a mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole, and diarylacrylonitrile, which have epoxy groups or haloalkyl groups.

[0049] The mass ratio of the catalyst to the acylation reagent or the etherification reagent with mechanochromic molecules in step (2) is 1:1-1:200, preferably 1:5-1:100.

[0050] For acylation reagents with mechanochromic molecules, an acylation reaction occurs; for etherification reagents with mechanochromic molecules, an etherification reaction occurs. The acylation reaction in step (2) occurs at a temperature of 40-200℃, preferably 100-155℃, and for a reaction time of 1-72h, preferably 1.5-4h. The etherification reaction occurs at a temperature of 30-200℃, preferably 60-155℃, and for a reaction time of 1-72h, preferably 1.5-24h.

[0051] The mass ratio of the matrix material to the acylation reagent or the etherification reagent with mechanochromic molecules is 1:0.001-1:2, preferably 1:0.005-1:1.

[0052] (3) Pour the solution after the reaction into the precipitant to precipitate the solid product, wash and dry it to obtain the metronidizer material.

[0053] The precipitant in step (3) is at least one of water and alcohol. For example, the alcohol is selected from at least one of methanol, ethanol, propanol, isopropanol, and isobutanol. The volume ratio of water to alcohol in the mixed solution is 1:1 to 20:1, preferably 1:1 to 10:1. Further, the regeneration process in the precipitant may include the coagulation, soaking, and washing of cellulose, for example, coagulation, soaking, and washing may be performed sequentially in different coagulation baths such as ionic liquid aqueous solution, water, and alcohol.

[0054] The mechanochromic material of the present invention can be prepared in various forms such as thin films, coatings, fibers, micelles or microspheres.

[0055] This invention also provides the application of mestichromic materials in anti-counterfeiting of tobacco packaging. For example, its application in anti-counterfeiting printing, decorative printing and dyeing, and signage on tobacco packaging.

[0056] Methocerosor color-changing materials used for anti-counterfeiting in tobacco packaging include the color response of the material to external forces, which is used to identify the opened state of the tobacco packaging based on the color change. The aforementioned color change refers to an irreversible, visible color change.

[0057] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available. Unless otherwise specified, the equipment used in the experiments is well known to those skilled in the art.

[0058] The mechanochromic material disclosed in this invention is prepared by a derivatization reaction of biomass polysaccharides with acylation or etherification reagents containing mechanochromic molecules. The following example uses the polysaccharide derivative and the dicarboxylated spiropyran derivative shown in formula (I), and their reaction formulas are as follows:

[0059]

[0060] Example 1

[0061] A method for preparing a mechanochromic material, designated CA 198 -SP5, including the following steps: Take 2.45g of cellulose acetate (CA) 198 0.94 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 60 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 2.85 g of dark red powder, namely CA, was obtained. 198 -SP5, yield 84.07%.

[0062] CA 198 -SP5 is a cellulose acetate ester modified with spiropyran, with a spiropyran substitution degree of 0.10.

[0063] Example 2

[0064] A method for preparing a mechanochromic material, designated CA 198 -SP10 includes the following steps: Take 2.45g of cellulose acetate (CA) 198 0.47 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 60 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 2.47 g of a dark red powder, namely CA, was obtained. 198 -SP10, yield 84.59%.

[0065] CA 198 -SP10 is a cellulose acetate ester modified with spiropyran, and the degree of spiropyran substitution is 0.068.

[0066] Example 3

[0067] A method for preparing a mechanochromic material, designated CA 198 -SP20 includes the following steps: Take 2.45g of cellulose acetate (CA) 1980.23 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 60 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 2.29 g of a dark red powder, namely CA, was obtained. 198 -SP20, yield 85.45%.

[0068] CA 198 -SP20 is a cellulose acetate ester modified with spiropyran, with a spiropyran substitution degree of 0.049.

[0069] Example 4

[0070] A method for preparing a mechanochromic material, designated CA 198 -SP40 includes the following steps: Take 2.45g of cellulose acetate (CA) 198 0.12 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 60 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 2.13 g of dark red powder, namely CA, was obtained. 198 -SP40, yield 82.88%.

[0071] CA 198 -SP40 is a cellulose acetate ester modified with spiropyran, with a spiropyran substitution degree of 0.043.

[0072] Example 5

[0073] A method for preparing a mechanochromic material, designated CA 198 -SP80 includes the following steps: Take 2.45g of cellulose acetate (CA) 198 0.059 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 60 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 2.09 g of a dark red powder, namely CA, was obtained. 198 -SP80, yield rate 83.33%.

[0074] CA 198-SP80 is a cellulose acetate ester modified with spiropyran, with a spiropyran substitution degree of 0.036.

[0075] Example 6

[0076] A method for preparing a mechanochromic material, designated CA 255 -SP5, including the following steps: Take 2.70g of cellulose acetate (CA) 255 0.94 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 80 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 3.15 g of a dark red powder, namely CA, was obtained. 255 -SP5, yield 86.54%.

[0077] CA 255 -SP5 is a cellulose acetate ester modified with spiropyran, with a spiropyran substitution degree of 0.079.

[0078] Figure 1 CA prepared in Example 6 255 The infrared spectrum of -SP5. No characteristic absorption peaks belonging to the spiropyran group were observed, indicating that the content of spiropyran groups in the CA-SP product is very low.

[0079] Example 7

[0080] A method for preparing a mechanochromic material, designated CA 255 -SP10 includes the following steps: Take 2.70g of cellulose acetate (CA) 255 0.47 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 80 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 2.71 g of dark red powder, namely CA, was obtained. 255 -SP10, yield 85.49%.

[0081] CA 255 -SP10 is a cellulose acetate ester modified with spiropyran, with a spiropyran substitution degree of 0.028.

[0082] Example 8

[0083] A method for preparing a mechanochromic material, designated CA 255-SP20 includes the following steps: Take 2.70g of cellulose acetate (CA) 255 0.23 g of a dicarboxylated spiropyran derivative (COOH-SP-COOH), 2.06 g of DCC, and 1.21 g of DMAP were dissolved in 80 mL of DMF. The mixture was refluxed in an oil bath at 155 °C for 3 h. After the reaction was complete, the concentrated reaction solution was added to deionized water, and after precipitation, washing, and freeze-drying, 2.52 g of dark red powder, namely CA, was obtained. 255 -SP20, yield 86.01%.

[0084] CA 255 -SP20 is a cellulose acetate ester modified with spiropyran, with a spiropyran substitution degree of 0.017.

[0085] Example 9

[0086] A method for preparing a mechanochromic material, designated Cell-SP, includes the following steps: 1.60 g of microcrystalline cellulose (MCC, DP=220) is dissolved in 60 g of ionic liquid AmimCl at 80 °C with stirring. Then, 2.06 g of DCC, 1.21 g of DMAP, and 0.94 g of dicarboxyspiropyran derivative (COOH-SP-COOH) are added. The mixed solution is refluxed in an oil bath at 60 °C for 24 h. After the reaction is complete, the concentrated reaction solution is added to deionized water, and after precipitation, washing, and freeze-drying, 2.14 g of pink powder, i.e., Cell-SP, is obtained, with a yield of 84.25%.

[0087] Cell-SP is a cellulose-spiropyran modified ester with a spiropyran substitution degree of 0.054.

[0088] Example 10

[0089] A method for preparing a cellulose-spiropyran film includes the following steps: After the reaction of the mixed solution in Example 6 is completed, the viscous solution is scraped into a film of a certain thickness (e.g., 1000 μm) on a smooth table or glass plate using a film scraper. After solidification in the air, the film is immersed in ethanol to displace the unreacted spiropyran and catalyst. The four sides are then fixed, and the film is dried using supercritical carbon dioxide to obtain a responsive aerogel film with mechanochromic properties.

[0090] Figure 2 The image shows the UV-Vis absorption spectrum of the cellulose acetate membrane containing spiropyran prepared in Example 10 before stretching. As can be seen from the image, before stretching, CA... 255 The absorption peak of the SP5 film is located at 344 nm.

[0091] Figure 3The image shows the UV-Vis absorption spectrum of the stretched region of the cellulose acetate membrane containing spiropyran prepared in Example 10. As can be seen from the image, after stretching, CA... 255 A new absorption peak appears at 612 nm in the UV-Vis absorption spectrum of the SP5 film.

[0092] Figure 4 The color change of the cellulose acetate film containing spiropyran derivative prepared in Example 10 before and after stretching. Before stretching, CA 255 -SP5 membrane is a colorless and transparent film; after stretching, the membrane visibly turns pale purple, and the color change is irreversible. This indicates that mechanical stimulation can cause the spiropyran in the cellulose acetate membrane containing spiropyran to undergo a ring-opening reaction, thus exhibiting mechanochromic properties.

[0093] The color-changing mechanism is as follows:

[0094]

[0095] Example 11

[0096] Application of cellulose-spiropyran film in tobacco anti-counterfeiting

[0097] A pull tab is installed at the opening of the tobacco packaging box, forming a force-induced color-changing layer. When unactivated, it is transparent, invisible, and deeply integrated with the packaging. Upon application of external force, a molecular ring-opening structure transformation occurs, resulting in a visible color change that is irreversible. This design facilitates consumers in opening the cigarette box and prevents tobacco products from being illegally opened, tampered with, or damaged during distribution, thereby protecting consumers' legal rights.

[0098] Figure 5 This is a schematic diagram illustrating the anti-counterfeiting design of spiropyran-containing cellulose acetate prepared in Example 10. It can be seen that the CA prepared in Example 10 of this invention... 255 -The SP5 film serves as a tear strip for cigarette packaging, allowing consumers to instantly confirm whether the product has been opened for the first time by observing the color change during the tearing process. The transparent, force-sensitive color-changing layer does not disrupt the overall packaging design when unactivated. However, when subjected to external forces such as tearing or squeezing, it undergoes a molecular ring-opening structure transformation, triggering an irreversible color change and forming a purple mark extending along the tear direction. This visually reveals the opened state of the packaging, balancing anti-counterfeiting requirements with brand visual aesthetics.

[0099] Those skilled in the art will anticipate that when the matrix material, mechanochromic molecules, etc., in the above embodiments are replaced with other substances listed in the invention, it is also possible to obtain cellulose mechanochromic materials and cellulose films with mechanochromic properties.

[0100] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A mechanochromic material, characterized in that, The invention comprises a matrix material and a mechanochromic molecule bonded to the matrix material, wherein the matrix material is selected from at least one of starch, chitosan, dextran, chitin, lignin, cellulose, microcrystalline cellulose, cellulose ester, and cellulose ether, and the mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole, and diarylacrylonitrile, and the degree of substitution of the mechanochromic molecule is 0.001-1.

2. A method for preparing the mechanochromic material according to claim 1, characterized in that, Includes the following steps: (1) Dissolve and disperse the matrix material in a solvent to obtain a homogeneous solution of the matrix material; (2) Add a catalyst and an acylation reagent with mechanochromic molecules or an etherification reagent with mechanochromic molecules to a homogeneous solution and carry out the reaction; (3) Pour the solution after the reaction into the precipitant to precipitate the solid product, wash and dry it to obtain the metronidizer material.

3. The preparation method according to claim 2, characterized in that, The solvent in step (1) is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, chloroform, pyridine, N-methylpyrrolidone and ionic liquid.

4. The preparation method according to claim 2, characterized in that, The mass percentage concentration of the matrix material in the homogeneous solution in step (1) is 0.5-20%.

5. The preparation method according to claim 2, characterized in that, The catalyst in step (2) is selected from at least one of 4-dimethylaminopyridine, dicyclohexylcarbodiimide, N,N'-carbonyldiimidazole, triethylamine, imidazole, pyridine, benzotriazole, sodium hydroxide and aluminum oxide; The acylation reagent having a mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole and diarylacrylonitrile with a carboxylic acid, acid anhydride or acyl halide group. The etherifying agent having a mechanochromic molecule is selected from at least one of anthracene, pyrene, spiropyran, spiroxazine, phenothiazine, benzoxazine, diarylethylene, triphenylethylene, tetraphenylethylene, hexaaryldiimidazole, and diarylacrylonitrile, which have epoxy groups or haloalkyl groups.

6. The preparation method according to claim 2, characterized in that, The mass ratio of the catalyst to the acylation reagent or the etherification reagent with mechanochromic molecules in step (2) is 1:1 to 1:

200.

7. The preparation method according to claim 2, characterized in that, The mass ratio of the matrix material to the acylation reagent or the etherification reagent with mechanochromic molecules is 1:0.001-1:

2.

8. The preparation method according to claim 2, characterized in that, The acylation reaction in step (2) has a reaction temperature of 40-200℃ and a reaction time of 1-72h, and the etherification reaction has a reaction temperature of 30-200℃ and a reaction time of 1-72h.

9. The preparation method according to claim 2, characterized in that, The precipitant in step (3) is at least one of water and alcohol.

10. The application of the mechanochromic material as described in claim 1 in anti-counterfeiting of tobacco packaging.

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