Stimuli-responsive self-healing fluorescent hydrogel, preparation method thereof and anti-counterfeiting application thereof

Abstract

The application belongs to the field of luminescent materials, and relates to a stimulus-responsive self-repairing fluorescent hydrogel. Specifically, the application relates to a stimulus-responsive self-repairing fluorescent hydrogel, a preparation method thereof and anti-fake application. In the method, first, an aggregate formed by a surfactant hexadecyl trimethyl ammonium chloride is used to wrap a hydrophobic anthracene-based fluorescent group 9-anthracene methyl methacrylate to form a micelle, and then, the micelle solution is copolymerized with a polymer monomer acrylic acid and zirconium chloride through free radical initiation to obtain a stimulus-responsive fluorescent hydrogel. The hydrogel has self-repairing capability and fluorescent stimulus-responsive capability, and is expected to be applied in the fields of biomimetic smart materials and information.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials and relates to a stimulus-responsive self-healing fluorescent hydrogel. Specifically, it describes a stimulus-responsive self-healing fluorescent hydrogel, its preparation method, and its anti-counterfeiting applications. Background Technology

[0002] Fluorescent soft materials exhibit a variety of properties and functions (such as tunable color, deformation-induced color change, and environmental sensing), showing significant application prospects in fields such as sensing and detection, bioengineering, biomimetic actuation, and soft robotics. Among these, stimulus-responsive fluorescent soft materials are particularly attractive, arising from a synergistic system between a polymer network structure and stimulus-responsive fluorescent groups. Fluorescent groups include organic dye molecules, quantum dots, rare-earth complexes, and aggregation-inducing molecules, which can change color or fluorescence in response to pH, light, or heat stimulation. Introducing these fluorescent groups into the polymer network structure not only endows the polymeric soft materials with stimulus-responsive fluorescence properties but also imparts mechanical flexibility. Given the excellent fluorescence properties, inclusiveness, and unique stimulus responsiveness of stimulus-responsive fluorescent soft materials, researchers are developing and applying them to dynamic information storage to improve security levels. Against the backdrop of severe global information security challenges, research on these intelligent fluorescent materials has significant practical implications in the fields of anti-counterfeiting and information encryption. However, most of these materials involve lengthy and complex manufacturing processes. Furthermore, due to the limitations of the water solubility of fluorescent groups, the resulting fluorescent materials are mostly organic systems, lacking good biocompatibility and failing to meet environmentally friendly design strategies. Therefore, there is a need for the development of more effective, easily handled, programmable, and environmentally friendly aqueous systems to stimulate fluorescent soft materials.

[0003] Anthracene fluorophores undergo a [4+4] cycloaddition reaction under ultraviolet light irradiation (λ>300 nm), accompanied by a decline in blue fluorescence. However, fluorescence is restored upon irradiation with short-wave ultraviolet light (λ<300 nm) or under heating conditions through dimer cleavage. Compared to most other organic dye chromophores, anthracene derivatives do not exhibit significant apparent color changes when fluorescence changes. Therefore, anthracene fluorophores are highly attractive candidates for constructing stimulus-responsive fluorescent polymer materials. However, as an organic molecule, anthracene is insoluble in water (due to its hydrophobicity), making it difficult to use in the preparation of flexible hydrogel materials. Therefore, there is an urgent need to develop an effective strategy for constructing stimulus-responsive fluorescent hydrogels using anthracene fluorophores.

[0004] Self-healing hydrogels have attracted much attention due to their unique self-repairing capabilities, which allow them to restore their original properties after damage, thereby extending their lifespan and improving stability. However, hydrogels may be damaged during use, leading to information loss, a problem that self-healing materials can effectively avoid. Developing such a self-healing hydrogel with tunable fluorescent patterns provides insights into the development of stimulus-responsive fluorescent smart hydrogels and holds promise for their practical applications in biomimetic smart materials and information technology. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a stimulus-responsive self-healing fluorescent hydrogel, its preparation method, and its anti-counterfeiting application.

[0006] This invention is achieved through the following technical solution: A method for preparing a stimulus-responsive self-healing fluorescent hydrogel includes the following steps: S1. Dissolve hexadecyltrimethylammonium chloride in distilled water and stir at 50-80°C for 3-7 hours. S2. Add anthracene fluorescent molecule 9-anthracene methyl methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Take the micelle solution from step 2, add acrylic acid, sonicate for 5-10 min, add zirconium chloride, continue stirring and reacting at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0007] Furthermore, in S1, the concentration of hexadecyltrimethylammonium chloride is 96 mg / mL.

[0008] Furthermore, in S2, the amount of methyl 9-anthracene methacrylate added is 2.8-16.8 mg, and the mass ratio of methyl 9-anthracene methacrylate to hexadecyltrimethylammonium chloride is (0.7-4.2) mg:120 mg.

[0009] Furthermore, in S3, the volume ratio of acrylic acid to micelle solution is (1.0-1.3) mL: 2.8 mL.

[0010] Furthermore, in S3, the amount of zirconium chloride added is 11.65-46.6 mg.

[0011] Furthermore, in S3, the ratio of potassium persulfate to acrylic acid is 40 mg: (1.0-1.3) mL.

[0012] Hydrogel preparation mechanism: Step S1: Formation of surfactant micelles. Hexadecyltrimethylammonium chloride is a cationic surfactant. When its concentration is above the critical micelle concentration (CMC), it spontaneously assembles into micelles in water. Its hydrophilic quaternary ammonium salt head faces the aqueous phase, while the hydrophobic long alkyl chain tails aggregate together to form a hydrophobic core.

[0013] Step S2: The fluorescent monomer is encapsulated in micelles. The 9-anthracene methyl methacrylate molecule contains anthracene rings (strong fluorescent groups) and methacrylate groups (polymerizable groups), but it is itself hydrophobic. Under heating and stirring, the 9-anthracene methyl methacrylate molecule is encapsulated within the hydrophobic core of the CTAB micelles, forming a micelle solution loaded with the fluorescent monomer. This ensures that the hydrophobic 9-anthracene methyl methacrylate can be uniformly dispersed in the aqueous phase.

[0014] Step S3: Preparation before polymerization and crosslinking. This step involves several important processes: Mixing and sonication: After adding acrylic acid (AA, a hydrophilic monomer), the mixture was sonicated to ensure homogeneous mixing with the micelle solution. Two monomers were present in the system: AA in the aqueous phase and methyl 9-anthracene methacrylate in the micelle core.

[0015] Add crosslinking agent: Add zirconium chloride (ZrCl4). ZrCl4 dissociates in water to release Zr 4+ Ions. Zr 4+ It is a high-valence metal ion with strong coordination ability.

[0016] Prefitting position: Zr 4+ It will undergo pre-coordination with the carboxyl group (-COOH) of acrylic acid (AA) to form Zr 4+ -AA complex. This step is very important because it allows cross-linking points to form initially before polymerization.

[0017] Oxygen removal and initiator addition: Nitrogen gas is introduced to remove oxygen from the system. Oxygen is an inhibitor of free radical polymerization, consuming free radicals and causing the polymerization reaction to fail or result in an excessively low molecular weight.

[0018] Add potassium persulfate: Potassium persulfate is a water-soluble thermal initiator. Upon heating (step S4), it decomposes to produce sulfate anion radicals (SO4•-). - This leads to aggregation.

[0019] Step S4: Thermally Initiated Polymerization and Gelation: Under heating conditions, potassium persulfate decomposes to generate free radicals. These free radicals attack acrylic monomers, forming monomer radicals. These monomer radicals continue to combine with other acrylic monomers, as well as with 9-anthracene methyl methacrylate monomers within the micelles, causing the polymer chains to grow continuously. The polyacrylic acid chains extend in water. The 9-anthracene methyl methacrylate monomers encapsulated within the micelles polymerize with each other, forming hydrophobic crosslinking points (physical crosslinking) within the micelles. Simultaneously, anthracene fluorophores are also immobilized at these crosslinking points. Zr 4+ Ions coordinate with multiple carboxyl groups in the polyacrylic acid chain to form metal-ligand coordination bonds (dynamic non-covalent bonds), which play a role in chemical cross-linking. Through the two mechanisms of hydrophobic association (physical cross-linking) and metal coordination (chemical cross-linking) mentioned above, the polymer chain forms a three-dimensional network structure that encapsulates water molecules, thereby forming a hydrogel.

[0020] The present invention also provides a stimulus-responsive self-healing fluorescent hydrogel prepared using the above preparation method.

[0021] Furthermore, the hydrogel exhibits a sponge-like porous three-dimensional network structure. The uniform distribution of carbon, oxygen, and zirconium elements within this three-dimensional network structure endows the hydrogel with self-healing capabilities and fluorescence-responsive properties.

[0022] Another objective of this invention is to provide the application of the stimulus-responsive self-healing fluorescent hydrogel in the field of intelligent information anti-counterfeiting.

[0023] (1) Beneficial technical effects of the present invention: In the method described, the hydrophobic anthraquinone fluorescent group 9-anthracene methyl methacrylate is first encapsulated by aggregates formed by the surfactant hexadecyltrimethylammonium chloride to form micelles, thereby improving the solubility of the hydrophobic anthraquinone fluorescent group in water and providing an effective approach to improving the solubility of anthraquinone fluorescent groups in water. Subsequently, the micelle solution is copolymerized with the polymer monomers acrylic acid and zirconium chloride via free radical initiation to obtain a stimulus-responsive fluorescent hydrogel. In this system, due to the photo / thermal induced reversible monomer-dimer transformation of the anthraquinone unit in 9-anthracene methyl methacrylate, the hydrogel exhibits tunable and reversible fluorescence. Therefore, various fluorescent patterns can be encoded on the surface of the hydrogel with the help of a photomask to complete the information encryption process, and the hidden information can be decoded by ultraviolet light irradiation. In addition, the introduction of zirconium ions can form dynamic metal-ligand coordination bonds with the carboxyl groups on acrylic acid, giving the hydrogel excellent self-healing ability. The design of this hydrogel with self-healing ability and tunable fluorescent patterns provides a way to develop stimulus-responsive fluorescent smart hydrogels and is expected to promote their practical application in the fields of biomimetic smart materials and information.

[0024] (2) The fluorescence of the hydrogel material originates from the anthracene rings successfully embedded in the hydrophobic regions of the polymer network. Encapsulating it in micelles avoids the quenching problem of the anthracene rings in the aqueous phase, thus ensuring the fluorescence intensity.

[0025] The key to the self-healing property of the hydrogel material lies in Zr. 4+ -COO - Coordination bonds. These coordination bonds are dynamically reversible: when the gel is damaged (chain breakage), the coordination bonds can break; when the broken surfaces come into contact, Zr... 4+ The carboxyl group can be re-coordinated and cross-linked again, thereby achieving autonomous self-repair (usually without external stimulation).

[0026] The stimuli responsiveness of the hydrogel material originates from the fact that anthracene fluorescent molecules undergo a [4+4] cycloaddition reaction under ultraviolet light irradiation (λ>300 nm), accompanied by the decay of blue fluorescence, while the anthracene fluorescent molecules break down into dimers under heating conditions, and the fluorescence is restored.

[0027] (3) The fluorescent hydrogel obtained by this invention has excellent stimulus response performance, and can achieve attenuation and recovery of gel fluorescence under external stimulation (ultraviolet light irradiation / heating), and can be repeated multiple times; based on dynamic reversible Zr 4+ -Carboxyl coordination bond crosslinking network, stimulus-responsive fluorescent hydrogel exhibits significant self-healing ability; the stimulus-responsive self-healing fluorescent hydrogel of the present invention can be applied in the field of intelligent information anti-counterfeiting. Attached Figure Description

[0028] Figure 1 The tensile stress-strain curves are those of the stimulus-responsive self-healing fluorescent hydrogels in Examples 1-4.

[0029] Figure 2 The fluorescence spectra of the stimulus-responsive self-healing fluorescent hydrogels in Examples 1-4 are shown.

[0030] Figure 3 The image shows the cyclic stress-strain curves of the stimulus-responsive self-healing fluorescent hydrogel in Example 3 under different strain conditions.

[0031] Figure 4 The figures show the stimulus-responsive self-healing fluorescent hydrogel in Example 3 under 10 consecutive cycles of tensile loading and unloading at 250% strain.

[0032] Figure 5 This is a digital photograph of the self-healing fluorescent hydrogel that responds to stimuli in Example 3.

[0033] Figure 6 This is a photograph of the self-healing fluorescent hydrogel incision in Example 3 under an optical microscope.

[0034] Figure 7 This is a scanning electron microscope image of the stimulus-responsive self-healing fluorescent hydrogel in Example 3.

[0035] Figure 8 These are digital photographs of the hydrogel in Example 3 under fluorescent and ultraviolet light.

[0036] Figure 9 The emission spectrum of the stimulus-responsive self-healing fluorescent hydrogel in Example 3 is shown.

[0037] Figure 10 Schematic diagram of fluorescence decay / recovery of anthracene-based fluorescent hydrogel.

[0038] Figure 11 The image shows the fluorescence decay of the stimulus-responsive self-healing fluorescent hydrogel in Example 3.

[0039] Figure 12 This is a luminescence decay / recovery cycle diagram of the stimulus-responsive self-healing fluorescent hydrogel in Example 3.

[0040] Figure 13 This illustrates the application of the stimulus-responsive self-healing fluorescent hydrogel in Example 3 in the field of intelligent information anti-counterfeiting. Detailed Implementation

[0041] The preparation method of a stimulus-responsive self-healing fluorescent hydrogel provided by the present invention will be described in detail below with reference to specific embodiments, but this does not limit the present invention.

[0042] The hexadecyltrimethylammonium chloride, methyl 9-anthracene methacrylate, zirconium chloride, acrylic acid, and potassium persulfate involved in this invention are all commercially available.

[0043] Example 1

[0044] A novel method for preparing a stimulus-responsive self-healing fluorescent hydrogel includes the following steps: S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 2.8 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.2 mL of acrylic acid, sonicate for 5-10 min, add 23.3 mg of zirconium chloride, continue stirring the reaction at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0045] Example 2

[0046] S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 5.6 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.2 mL of acrylic acid, sonicate for 5-10 min, add 23.3 mg of zirconium chloride, continue stirring the reaction at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0047] Example 3

[0048] S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 11.2 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.2 mL of acrylic acid, sonicate for 5-10 min, add 23.3 mg of zirconium chloride, continue stirring the reaction at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0049] Example 4

[0050] S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 16.8 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.2 mL of acrylic acid, sonicate for 5-10 min, add 23.3 mg of zirconium chloride, continue stirring the reaction at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0051] Examples 1-4 investigate the effect of the amount of methyl 9-anthracene methacrylate.

[0052] Example 5

[0053] S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 11.2 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.0 mL of acrylic acid, sonicate for 5-10 min, add 23.3 mg of zirconium chloride, continue stirring the reaction at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0054] Example 6

[0055] S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 11.2 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.3 mL of acrylic acid, sonicate for 5-10 min, add 23.3 mg of zirconium chloride, continue stirring at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0056] Examples 3, 5, and 6 investigate the effect of the amount of acrylic acid. The content of acrylic acid directly affects the crosslinking density and mechanical properties of the hydrogel; a higher content provides more carboxyl groups to coordinate with zirconium ions, forming a denser crosslinking network, which increases the gel's hardness, decreases its toughness, and may weaken its self-healing ability due to restricted molecular chain movement; conversely, a lower content of acrylic acid leads to fewer crosslinking points, making the gel softer and easier to stretch, but its mechanical strength may be insufficient. Through experimental verification, this invention limits the amount of acrylic acid added to 1.0-1.3 mL.

[0057] Example 7

[0058] S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 11.2 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.2 mL of acrylic acid, sonicate for 5-10 min, add 11.65 mg of zirconium chloride, continue stirring the reaction at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0059] Example 8

[0060] S1. Accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir the reaction at 50-80°C for 3-7 hours. S2. Add 11.2 mg of methyl 9-anthracene methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Weigh 2.8 mL of the micelle solution from step 2, add 1.1 mL of acrylic acid, sonicate for 5-10 min, add 46.6 mg of zirconium chloride, continue stirring at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and add 40 mg of potassium persulfate at room temperature. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

[0061] Examples 3, 7, and 8 investigated the effect of zirconium chloride dosage. Zirconium ions in zirconium chloride significantly enhance the hardness of the hydrogel by forming coordination crosslinks with carboxyl groups in the gel network. The higher the content, the greater the crosslinking density, the harder and more brittle the gel, and the worse its stretchability. At the same time, excessively high crosslinking density restricts the dynamic movement of molecular chains, resulting in a severe decrease in its self-healing ability. Therefore, the dosage of zirconium chloride was limited to 11.65-46.6 mg.

[0062] Figure 1 The tensile stress-strain curves of the stimulus-responsive self-healing fluorescent hydrogels in Examples 1-4 are shown. It can be seen that under the same strain conditions, Example 1 can withstand significantly higher stress than the other examples. With increasing amounts of methyl 9-anthracene methacrylate, the strength of the hydrogel actually decreases. This is because the C=C double bonds in its molecule participate in the cross-linking reaction as active sites during polymerization, introducing additional cross-linking points and leading to a significant increase in the cross-linking density of the hydrogel network. The increased cross-linking density increases the rigidity and decreases the ductility of the hydrogel network, making it more prone to breakage.

[0063] Figure 2 The images show the fluorescence spectra of the stimulus-responsive self-healing fluorescent hydrogels in Examples 1-4. Anthracene, due to its unique electron-rich π-π conjugated structure, emits blue fluorescence, and the prepared gels exhibit the same properties. As the concentration of the fluorescent molecule 9-anthracene methyl methacrylate increases, the blue fluorescence of the hydrogel gradually intensifies. Figure 2 As shown, the fluorescence of the hydrogel was weak when the concentration of 9-anthracene methyl methacrylate was 2.8 mg. With increasing concentration, the hydrogel exhibited bright blue fluorescence, and the fluorescence became stronger at higher concentrations. Considering both the fluorescence intensity and mechanical properties of the hydrogel, the performance was then studied with a concentration of 11.2 mg of 9-anthracene methyl methacrylate.

[0064] Figure 3The images show the cyclic stress-strain curves of the stimulus-responsive self-healing fluorescent hydrogel in Example 3 under different strain conditions. The test involved five consecutive loading-unloading cycles with no recovery time between cycles, and the strain range gradually increased from 100% to 250%. The results showed that all stress-strain curves exhibited significant hysteresis, and the hysteresis loop area increased significantly with increasing strain amplitude. This is mainly because during tensile deformation, the non-covalent crosslinking points break, consuming a large amount of energy, leading to an increase in the hysteresis loop area. In short, when an external force is applied, Zr... 4+ The reversible breaking of the dynamic coordination bonds between carboxyl groups in the polyacrylic acid molecular chain effectively improves the mechanical properties of the material through the dissipation of intermolecular bond energy. Furthermore, Zr... 4+ The reversible dynamic coordination bonds between the carboxyl groups and polyacrylic acid molecular chains enable the material to maintain its self-healing ability after damage. Figure 4 The figures show the stress-responsive self-healing fluorescent hydrogel from Example 3 under 10 consecutive cycles of tensile loading and unloading at 250% strain. The results indicate that after 10 consecutive loading-unloading cycles at a large strain of 250%, the hysteresis loop shows little change except in the first cycle, suggesting that the stress-responsive fluorescent hydrogel possesses certain fatigue resistance.

[0065] Materials with self-healing capabilities can not only extend the lifespan of materials, but also improve their durability and reliability. Figure 5 This is a digital photograph of the self-healing fluorescent hydrogel in Example 3. To make the cut areas easier to distinguish, the two hydrogels were stained with Rhodamine B and methylene blue, respectively. The two newly cut hydrogels were then reassembled and left to self-heal at room temperature for 12 hours. It can be seen that the two self-healed hydrogels have bonded together and can withstand large tensile deformation. Figure 6 This is a photograph of the self-healing incision in the stimulus-responsive self-healing fluorescent hydrogel of Example 3 under an optical microscope. The optical microscope image shows that the incision on the hydrogel almost completely disappeared after self-healing. This is mainly due to the Zr... 4+ The reversible dynamic coordination bonds between the carboxyl groups and polyacrylic acid molecular chains enable the material to maintain its self-healing ability after damage.

[0066] Figure 7 This is a scanning electron microscope (SEM) image of the stimulus-responsive self-healing fluorescent hydrogel from Example 3. It can be seen that the hydrogel exhibits a sponge-like porous three-dimensional network structure. Furthermore, the mapping scan shows a uniform distribution of carbon, oxygen, and zirconium elements within the three-dimensional network structure of the hydrogel, indicating dynamic Zr... 4+-COOH coordination bonds form a three-dimensional cross-linked network, providing a structural basis for bonding and recombination during the self-healing process.

[0067] Figure 8 These are digital photographs of the stimulus-responsive self-healing fluorescent hydrogel from Example 3 under fluorescent and ultraviolet light. Figure 8 It can be seen that the hydrogel has high transparency under fluorescent light and exhibits bright and uniform blue fluorescence under ultraviolet light. Figure 9 The figure shows the emission spectrum of the stimulus-responsive self-healing fluorescent hydrogel in Example 3. As can be seen from the figure, the emission spectrum of the hydrogel is in the range of 400-700 nm, and the optimal emission wavelength is around 429 nm, which is consistent with the blue fluorescence emission mentioned above.

[0068] The hydrogels in Examples 1-4 exhibit fluorescence-responsive properties, primarily because anthracene fluorescent molecules undergo a [4+4] cycloaddition reaction under ultraviolet light irradiation (λ>300 nm), accompanied by a decline in blue fluorescence. However, the anthracene fluorescent molecules are regenerated under heating conditions through dimerization, resulting in fluorescence recovery (e.g., ...). Figure 10 (As shown). Figure 11 This is a fluorescence decay diagram of the stimulus-responsive self-healing fluorescent hydrogel in Example 3. Under 365 nm ultraviolet light irradiation, the fluorescence intensity of the luminescent hydrogel gradually decreases, decaying to 33% of its original intensity after 10 minutes of irradiation. Figure 12 As shown, when the hydrogel is heated at 70-80°C for 30 minutes, its fluorescence intensity is restored, and this process can be repeated multiple times.

[0069] Example 9

[0070] The hydrogel prepared in Example 3 was used in conjunction with a smartphone to construct an intelligent anti-counterfeiting system. Figure 13 The specific steps are as follows: S1, Information Encryption and Writing S1.1 First, the encrypted information "smart" is compiled into a standard QR code digital matrix using an algorithm. This QR code is the carrier of the information.

[0071] S1.2, Create a photomask template: Create a photomask template from this QR code matrix.

[0072] S1.3. Place this photomask firmly onto the hydrogel prepared in Example 3. Irradiate with 365 nm ultraviolet light for 10 minutes. The ultraviolet light can only penetrate the transparent area of ​​the photomask to illuminate a specific area of ​​the hydrogel (i.e., the target area).

[0073] S2, Information Hiding The hydrogel in Example 3 is highly transparent and colorless. Under sunlight, the constructed QR code has no visual characteristics; neither the human eye nor a mobile phone camera can detect any pattern or density difference. The entire gel looks like an ordinary transparent pad, perfectly concealing the information. Smartphones cannot directly recognize the hidden information.

[0074] S3. Information Reading and Verification ("Development" and Decryption"): When verification is required, irradiate the surface of the hydrogel with ultraviolet light, and a clear and bright QR code pattern will appear.

[0075] S4. Smartphone Recognition: The smartphone camera can easily capture this high-contrast fluorescent QR code image. The QR code scanning app on the phone will recognize it as a standard QR code and quickly extract the encoded information – “smart”. Thus, the encrypted information has been successfully and conveniently read.

[0076] This application utilizes the dynamic information writing and encryption properties of stimulus-responsive fluorescent hydrogels, combined with mobile terminal recognition technology, to construct an intelligent anti-counterfeiting system that integrates high security, convenient verification, and low cost.

Claims

1. A method for preparing a stimulus-responsive self-healing fluorescent hydrogel, characterized in that: Includes the following steps: S1. Dissolve hexadecyltrimethylammonium chloride in distilled water and stir at 50-80°C for 3-7 hours. S2. Add anthracene fluorescent molecule 9-anthracene methyl methacrylate to the surfactant solution obtained in step 1, and stir the reaction at 50~80°C for 12~24 hours to obtain a micelle solution. S3. Take the micelle solution from step 2, add acrylic acid, sonicate for 5-10 min, add zirconium chloride, and continue stirring at room temperature for 15-60 min. Bubble the mixed solution with nitrogen for 10-30 min, and then add potassium persulfate at room temperature. The volume ratio of acrylic acid to micelle solution is (1.0-1.3) mL: 2.8 mL; the amount of zirconium chloride added is 11.65-46.6 mg. S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold and seal it. Place it in a drying oven at 60~80°C for 8~12 hours to obtain hydrogel.

2. The method for preparing the stimulus-responsive self-healing fluorescent hydrogel according to claim 1, characterized in that: In S1, the concentration of hexadecyltrimethylammonium chloride is 96 mg / mL.

3. The method for preparing the stimulus-responsive self-healing fluorescent hydrogel according to claim 1, characterized in that: In S2, the amount of methyl 9-anthracene methacrylate added is 2.8-16.8 mg, and the mass ratio of methyl 9-anthracene methacrylate to hexadecyltrimethylammonium chloride is (0.7-4.2) mg:120 mg.

4. The method for preparing the stimulus-responsive self-healing fluorescent hydrogel according to claim 1, characterized in that: In S3, the ratio of potassium persulfate to acrylic acid is 40 mg: (1.0-1.3) mL.

5. A stimulus-responsive self-healing fluorescent hydrogel prepared by the preparation method according to any one of claims 1-4.

6. The stimulus-responsive self-healing fluorescent hydrogel according to claim 5, characterized in that: The hydrogel has a sponge-like porous three-dimensional network structure with uniform distribution of carbon, oxygen, and zirconium elements in the three-dimensional network structure. The hydrogel has self-healing ability and fluorescence stimulus response performance.

7. The application of a stimulus-responsive self-healing fluorescent hydrogel prepared by the preparation method according to any one of claims 1-4 in the field of intelligent information anti-counterfeiting.

Images