Stimuli-responsive self-repairing fluorescent hydrogel as well as preparation method and anti-counterfeiting application thereof

Abstract

The invention belongs to the field of luminescent materials, and relates to stimuli-responsive self-repairing fluorescent hydrogel. In particular to stimuli-responsive self-repairing fluorescent hydrogel as well as a preparation method and anti-counterfeiting application thereof. According to the method, firstly, hydrophobic anthryl fluorophore 9-anthracene methyl methacrylate is wrapped by an aggregate formed by a surfactant hexadecyl trimethyl ammonium chloride to form micelles, and then, a micelle solution and polymer monomers acrylic acid and zirconium chloride are subjected to free radical-initiated copolymerization to obtain the stimuli-responsive fluorescent hydrogel. The hydrogel has self-repairing capability and fluorescence stimulation response capability, and is expected to be applied to the fields of bionic intelligent materials and information.

Description

Technical Field

[0001] The present invention belongs to the field of luminescent materials and relates to a stimulus-responsive self-repairing fluorescent hydrogel, specifically a stimulus-responsive self-repairing fluorescent hydrogel, a preparation method thereof, and anti-counterfeiting applications. Background Art

[0002] Fluorescent soft materials exhibit a variety of properties and functions, such as color tunability, color change, and environmental sensing, and hold significant application prospects in fields such as sensing, tissue engineering, biomimetic actuation, and soft robotics. Stimuli-responsive fluorescent soft materials are particularly attractive, resulting from a synergistic system between polymer networks and stimuli-responsive fluorescent groups. Fluorescent groups, such as organic dyes, quantum dots, rare earth complexes, and aggregation-inducing molecules, can undergo color or fluorescence changes in response to pH, light, or heat. Incorporating these fluorescent groups into polymer networks not only imbues the polymeric soft material with stimuli-responsive fluorescence but also imparts mechanical flexibility. Given their excellent fluorescence properties, inclusiveness, and unique stimuli-responsiveness, these stimuli-responsive fluorescent soft materials are being developed and applied to dynamic information storage and enhanced security. Given the severe challenges facing global information security, research into these intelligent fluorescent materials holds significant practical significance in anti-counterfeiting and information encryption. However, most of these materials require lengthy and complex manufacturing processes. Furthermore, due to the limited water solubility of fluorescent groups, the resulting fluorescent materials are mostly organic systems that lack good biocompatibility and are difficult to implement in environmentally friendly design strategies. Therefore, there is a need for the development of more effective, easy-to-process, programmable, and environmentally friendly aqueous systems to stimulate fluorescent soft materials.

[0003] Anthracene groups undergo a [4+4] cycloaddition reaction under ultraviolet light (λ > 300 nm), accompanied by a decay of blue fluorescence. However, upon short-wavelength ultraviolet light (λ < 300 nm) or heating, the fluorescence is restored through dimer cleavage. In contrast to most other organic dye chromophores, anthracene derivatives exhibit no noticeable color change upon fluorescence changes. Therefore, anthracene fluorophores are attractive candidates for constructing stimuli-responsive fluorescent polymeric materials. However, as an organic molecule, anthracene is insoluble in water (due to its hydrophobicity), making its use in the preparation of flexible hydrogels difficult. Therefore, the development of effective strategies for constructing stimuli-responsive fluorescent hydrogels using anthracene fluorophores is urgently needed.

[0004] Self-healing hydrogels have attracted considerable attention due to their unique self-repairing ability, which allows them to restore their original properties after damage, thereby extending their service life and improving their stability. However, hydrogels can be damaged during use, resulting in information loss, a problem that self-healing materials can effectively avoid. The development of such hydrogels with self-healing capabilities and tunable fluorescent patterns provides insights into the development of stimuli-responsive fluorescent smart hydrogels and is expected to promote their practical applications in the fields of biomimetic smart materials and information technology. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a stimulus-responsive self-repairing fluorescent hydrogel, a preparation method thereof, and anti-counterfeiting applications.

[0006] The present invention is achieved through the following technical solutions: A method for preparing a stimulus-responsive self-repairing fluorescent hydrogel comprises the following steps: S1, take hexadecyltrimethylammonium chloride and dissolve it in distilled water, stir and react at 50-80 ° C for 3-7 hours; S2, adding anthracene-based fluorescent molecule 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Measure the micellar solution in step 2, add acrylic acid, sonicate for 5 to 10 minutes, add zirconium chloride, continue stirring and reacting at room temperature for 15 to 60 minutes, bubble the mixed solution with nitrogen for 10 to 30 minutes, and then add potassium persulfate at room temperature; S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold, seal it, and place it in a drying oven at 60-80°C for 8-12 hours to obtain a hydrogel.

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

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

[0009] Furthermore, in S3, the volume ratio of acrylic acid and micelle solution was (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 addition ratio of potassium persulfate and acrylic acid is 40 mg: (1.0-1.3) mL.

[0012] Hydrogel preparation mechanism: Step S1: Surfactant micelle formation. Cetyltrimethylammonium chloride is a cationic surfactant. When its concentration exceeds the critical micelle concentration (CMC), it spontaneously assembles into micelles in water. Its hydrophilic quaternary ammonium salt heads face the aqueous phase, while its 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 an anthracene ring (a strong fluorescent group) and a methacrylate group (a polymerizable group), but it is inherently hydrophobic. Under heating and stirring, the 9-anthracene methyl methacrylate molecules are encapsulated within the hydrophobic core of the CTAB micelles, forming a micellar solution loaded with the fluorescent monomer. This ensures that the hydrophobic 9-anthracene methyl methacrylate is evenly dispersed in the aqueous phase.

[0014] Step S3: Preparation before polymerization and cross-linking. Several important processes occur in this step: Mixing and Ultrasonication: After adding acrylic acid (AA, a hydrophilic monomer), ultrasonic treatment is used to mix it evenly with the micelle solution. Two monomers are present in the system: AA in the aqueous phase and 9-anthracene methyl methacrylate in the micelle core.

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

[0016] Pre-matching: Zr 4+ It will pre-coordinate with the carboxyl group (-COOH) of acrylic acid (AA) to form Zr 4+ -AA complex. This step is very important because it allows the initial formation of cross-linking points before polymerization.

[0017] Deoxygenation and Initiator Addition: Nitrogen is introduced to remove oxygen from the system. Oxygen is an inhibitor of free radical polymerization and consumes free radicals, resulting in the inability to proceed with the polymerization reaction or a low molecular weight.

[0018] Add potassium peroxodisulfate: Potassium peroxodisulfate is a water-soluble thermal initiator. It decomposes under heating (step S4) to produce sulfate anion radicals (SO4· - ), thereby initiating polymerization.

[0019] Step S4: Thermally initiated polymerization and gelation: Under heating conditions, potassium persulfate decomposes to produce free radicals. The free radicals attack the acrylic acid monomers, forming monomer free radicals. The monomer free radicals continue to combine with other acrylic acid monomers and with the 9-anthracene methyl methacrylate monomers in the micelles, causing the polymer chain to continue to grow. The polyacrylic acid chain stretches out in water. The 9-anthracene methyl methacrylate monomers encapsulated in the micelles polymerize with each other, forming hydrophobic crosslinking points (physical crosslinking) inside the micelles. At the same time, the anthracene fluorophore is also fixed on these crosslinking points. Zr 4+ The ions coordinate with the multiple carboxyl groups of the polyacrylic acid chains, forming metal-ligand coordination bonds (dynamic non-covalent bonds), which act as chemical crosslinks. Through the aforementioned mechanisms of hydrophobic association (physical crosslinking) and metal coordination (chemical crosslinking), the polymer chains form a three-dimensional network structure that encapsulates water molecules, thus forming a hydrogel.

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

[0021] Furthermore, the hydrogel presents a sponge-like porous three-dimensional network structure. Carbon, oxygen, and zirconium are evenly distributed in the three-dimensional network structure of the hydrogel, and the hydrogel has self-repairing ability and fluorescence stimulation response performance.

[0022] Another object of the present invention is to provide an application of the stimulus-responsive self-repairing fluorescent hydrogel in the field of intelligent information anti-counterfeiting.

[0023] (1) Beneficial technical effects of the present invention: In the method, the aggregates formed by the surfactant hexadecyltrimethylammonium chloride are first used to encapsulate the hydrophobic anthracene-based fluorescent group 9-anthracene methyl methacrylate to form micelles, thereby improving the solubility of the hydrophobic anthracene-based fluorescent group in water, providing an effective idea for improving the solubility of the anthracene fluorophore in water. Subsequently, the micelle solution is copolymerized with the polymer monomers acrylic acid and zirconium chloride through free radical initiation to obtain a stimulus-responsive fluorescent hydrogel. In this system, due to the light / heat-induced reversible monomer-to-dimer transformation of the anthracene 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 pattern provides ideas for the development of stimulus-responsive fluorescent smart hydrogels and is expected to promote their practical applications in the fields of biomimetic smart materials and information.

[0024] (2) The fluorescence of the hydrogel material originates from the anthracene rings that are successfully embedded in the hydrophobic region of the polymer network. Encapsulating them in micelles avoids the quenching problem of the anthracene rings in the aqueous phase and ensures the fluorescence intensity.

[0025] The key to the self-healing property of the hydrogel material lies in Zr 4+ -COO - Coordination bond. This coordination bond is dynamically reversible: when the gel is damaged (chain breakage), the coordination bond can be broken; when the broken surfaces come into contact, Zr 4+ The carboxyl groups can realign to form cross-links again, thus achieving autonomous self-repair (usually without external stimulation).

[0026] The stimulus responsiveness of the hydrogel material is due to the fact that the anthracene-based 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-based fluorescent molecules dimer breaks under heating conditions and the fluorescence recovers.

[0027] (3) The fluorescent hydrogel obtained by the present invention has excellent stimulus response performance, which can realize the attenuation and recovery of gel fluorescence under external stimulation (ultraviolet light illumination / heating) and can be repeated multiple times; based on the dynamic reversible Zr 4+ -Carboxyl coordination bond cross-linking network, the stimulus-responsive fluorescent hydrogel exhibits significant self-repairing ability; the stimulus-responsive self-repairing fluorescent hydrogel described in the present invention can be applied to the field of intelligent information anti-counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1-4. The tensile stress-strain curve of the stimulus-responsive self-repairing fluorescent hydrogel in Examples 1-4.

[0029] Figure 2 This is the fluorescence spectrum of the stimulus-responsive self-repairing fluorescent hydrogel in Examples 1-4.

[0030] Figure 3 This is the cyclic stress-strain curve of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3 under different strain conditions.

[0031] Figure 4 10 continuous cycles of tensile loading and unloading curves of the stimulus-responsive self-repairing fluorescent hydrogel at 250% strain in Example 3.

[0032] Figure 5 This is a digital photo of the self-repairing stimuli-responsive self-repairing fluorescent hydrogel in Example 3.

[0033] Figure 6 This is a self-repairing photo of the stimulus-responsive self-repairing 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-repairing fluorescent hydrogel in Example 3.

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

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

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

[0038] Figure 11 This is the fluorescence decay diagram of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3.

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

[0040] Figure 13 This is the application of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3 in the field of intelligent information anti-counterfeiting. DETAILED DESCRIPTION

[0041] The preparation method of a stimulus-responsive self-repairing fluorescent hydrogel provided by the present invention will be described in detail below with reference to specific examples, but the present invention is not limited thereto.

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

[0043] Example 1

[0044] A method for preparing a novel stimulus-responsive self-repairing fluorescent hydrogel comprises the following steps: S1. Accurately weigh 480 mg of hexadecyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir and react at 50-80°C for 3-7 hours. S2, adding 2.8 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Weigh 2.8 mL of the micellar 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 and react at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and then add 40 mg of potassium persulfate at room temperature; S4, the prepared pre-gel solution is transferred to a polytetrafluoroethylene mold and sealed, and placed in a 60-80°C drying box for 8-12 hours to obtain a hydrogel.

[0045] Example 2

[0046] S1, accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve in 5 mL of distilled water, and stir at 50-80°C for 3-7 hours; S2, add 5.6 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, and stir at 50-80°C for 12-24 hours to obtain a micellar solution; S3, take 2.8 mL of the micellar solution in step 2, add 1.2 mL of acrylic acid, and ultrasonic for 5-10 min, then add 23.3 mg of zirconium chloride, continue to stir at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, then add 40 mg of potassium peroxodisulfate at room temperature; S4, the prepared pre-gel solution is transferred to a polytetrafluoroethylene mold and sealed, and placed in a 60-80°C drying box for 8-12 hours to obtain a hydrogel.

[0047] Example 3

[0048] S1, accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve in 5 mL of distilled water, and stir at 50-80°C for 3-7 hours; S2, add 11.2 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, and stir at 50-80°C for 12-24 hours to obtain a micellar solution; S3, take 2.8 mL of the micellar solution in step 2, add 1.2 mL of acrylic acid, and ultrasonic for 5-10 min, then add 23.3 mg of zirconium chloride, continue to stir at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, then add 40 mg of potassium peroxodisulfate at room temperature; S4, the prepared pre-gel solution is transferred to a polytetrafluoroethylene mold and sealed, and placed in a 60-80°C drying box for 8-12 hours to obtain a hydrogel.

[0049] Example 4

[0050] S1, accurately weigh 480 mg of cetyltrimethylammonium chloride and dissolve in 5 mL of distilled water, and stir at 50-80°C for 3-7 hours; S2, adding 16.8 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Weigh 2.8 mL of the micellar 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 and react at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and then add 40 mg of potassium persulfate at room temperature; S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold, seal it, and place it in a drying oven at 60-80°C for 8-12 hours to obtain a hydrogel.

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

[0052] Example 5

[0053] S1. Accurately weigh 480 mg of hexadecyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir and react at 50-80°C for 3-7 hours. S2, adding 11.2 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Weigh 2.8 mL of the micellar 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 and react at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and then add 40 mg of potassium persulfate at room temperature; S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold, seal it, and place it in a drying oven at 60-80°C for 8-12 hours to obtain a hydrogel.

[0054] Example 6

[0055] S1. Accurately weigh 480 mg of hexadecyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir and react at 50-80°C for 3-7 hours. S2, adding 11.2 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Weigh 2.8 mL of the micellar 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 then add 40 mg of potassium persulfate at room temperature; S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold, seal it, and place it in a drying oven at 60-80°C for 8-12 hours to obtain a hydrogel.

[0056] Examples 3, 5, and 6 explore the effects of the amount of acrylic acid used. The acrylic acid content directly affects the crosslinking density and mechanical properties of the hydrogel. A higher acrylic acid content provides more carboxyl groups to coordinate with zirconium ions, forming a denser crosslinking network, which increases the gel's hardness and decreases its toughness. This can also weaken the gel's self-healing ability due to restricted molecular chain movement. Conversely, a lower acrylic acid content results in fewer crosslinking points, making the gel softer and easier to stretch, but potentially lacking mechanical strength. Experimental verification indicates that the present invention limits the amount of acrylic acid added to 1.0-1.3 mL.

[0057] Example 7

[0058] S1. Accurately weigh 480 mg of hexadecyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir and react at 50-80°C for 3-7 hours. S2, adding 11.2 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Weigh 2.8 mL of the micellar 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 at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and then add 40 mg of potassium persulfate at room temperature; S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold, seal it, and place it in a drying oven at 60-80°C for 8-12 hours to obtain a hydrogel.

[0059] Example 8

[0060] S1. Accurately weigh 480 mg of hexadecyltrimethylammonium chloride and dissolve it in 5 mL of distilled water. Stir and react at 50-80°C for 3-7 hours. S2, adding 11.2 mg of 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Weigh 2.8 mL of the micellar 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 and react at room temperature for 15-60 min, bubble the mixed solution with nitrogen for 10-30 min, and then add 40 mg of potassium persulfate at room temperature; S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold, seal it, and place it in a drying oven at 60-80°C for 8-12 hours to obtain a hydrogel.

[0061] Examples 3, 7, and 8 explored the effect of zirconium chloride dosage. The zirconium ions in zirconium chloride significantly enhance the hardness of the hydrogel by forming coordinated crosslinks with carboxyl groups in the gel network. A higher zirconium chloride content results in a greater crosslink density, making the gel harder and more brittle, and its stretchability worse. At the same time, excessive crosslink density restricts the dynamic motion of the molecular chains, severely reducing their self-healing ability. Therefore, the dosage of zirconium chloride added is limited to 11.65-46.6 mg.

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

[0063] Figure 2 The fluorescence spectra of the stimulus-responsive self-repairing fluorescent hydrogel in Examples 1-4 are shown. Anthracene can emit blue fluorescence due to its unique electron-rich π-π conjugated structure, and the prepared gel also exhibits the same properties. As the concentration of the fluorescent molecule 9-anthracene methyl methacrylate increases, the blue fluorescence of the hydrogel gradually increases. Figure 2 As shown, the fluorescence is weak when the addition amount of 9-anthracene methyl methacrylate is 2.8 mg. As the concentration increases, the hydrogel exhibits bright blue fluorescence, and the fluorescence becomes stronger with increasing concentration. Considering the fluorescence intensity and mechanical properties of the hydrogel, the performance of the hydrogel with an addition amount of 9-anthracene methyl methacrylate of 11.2 mg was then studied.

[0064] Figure 3This is the cyclic stress-strain curve of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3 under different strain conditions. The test used 5 consecutive loading-unloading cycles with no recovery time between cycles. The strain range gradually increased from 100% to 250%. The results showed that all stress-strain curves showed significant hysteresis, and the hysteresis loop area increased significantly with the increase of strain amplitude. This is mainly because during the tensile deformation process, the non-covalent cross-linking points broke, consuming a lot of energy, resulting in an increase in the hysteresis loop area. This is mainly attributed to the fact that the rupture of the non-covalent cross-linking network of the material during the tensile deformation process consumed a lot of energy, resulting in an increase in the hysteresis loop area. In short, when an external force is applied, Zr 4+ The dynamic coordination bond between the carboxyl groups of the polyacrylic acid molecular chain is reversibly broken, and this process effectively improves the mechanical properties of the material through the dissipation mechanism of intermolecular bond energy. 4+ The reversibility of the dynamic coordination bond with the carboxyl groups between polyacrylic acid molecular chains enables the material to maintain self-repair capabilities after damage. Figure 4 Figure 3 shows the 10 consecutive tensile loading and unloading curves of the stimuli-responsive self-healing fluorescent hydrogel at 250% strain after 10 cycles. The results show that after 10 consecutive loading-unloading cycles at a maximum strain of 250%, the hysteresis loops do not change much except for the first cycle, indicating that the stimuli-responsive fluorescent hydrogel has a certain degree of fatigue resistance.

[0065] Materials with self-healing capabilities have the potential to not only extend the life of materials but also improve their durability and reliability. Figure 5 This is a digital photograph of the self-healing stimuli-responsive 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 reassembled and left to self-heal at room temperature for 12 hours. It can be seen that the two hydrogels have bonded together after self-healing and can withstand large tensile deformations. Figure 6 This is a self-repairing photo of the stimulus-responsive self-repairing fluorescent hydrogel incision in Example 3 under an optical microscope. It can be observed from the optical microscope image that the incision on the hydrogel almost completely disappears after self-repair. This is mainly because Zr 4+ The reversibility of the dynamic coordination bond with the carboxyl groups between polyacrylic acid molecular chains enables the material to maintain self-repair capabilities after damage.

[0066] Figure 7 This is a scanning electron microscope image of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3. It can be seen that the hydrogel presents a sponge-like porous three-dimensional network structure. In addition, from the mapping scan, it can be observed that the carbon, oxygen, and zirconium elements are evenly distributed in the three-dimensional network structure of the hydrogel, indicating that the dynamic Zr 4+The -COOH coordination bonds form a three-dimensional cross-linked network, providing a structural basis for bond reorganization during the self-healing process.

[0067] Figure 8 These are digital photos of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3 under fluorescent light 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 This is the emission spectrum of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3. It can be seen from the figure that 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 above-mentioned blue fluorescence emission.

[0068] The hydrogels in Examples 1-4 have fluorescence stimulus response properties, which is mainly due to the [4+4] cycloaddition reaction of the anthracene-based fluorescent molecules under ultraviolet light irradiation (λ>300 nm), accompanied by the decay of blue fluorescence. The anthracene-based fluorescent molecules are regenerated by the breakage of the dimer under heating conditions, and the fluorescence is restored (e.g. Figure 10 shown). Figure 11 This is the fluorescence decay diagram of the stimulus-responsive self-repairing fluorescent hydrogel in Example 3. Under 365 nm ultraviolet light irradiation, the fluorescence intensity of the luminescent hydrogel gradually decreases and decays to 33% of the original intensity after 10 minutes of irradiation. Figure 12 As shown in the figure, when the hydrogel is heated at 70-80°C for 30 minutes, its fluorescence intensity is restored, and this process can be repeated many times.

[0069] Example 9

[0070] The hydrogel prepared in Example 3 was combined with a smart phone to construct an intelligent anti-counterfeiting system ( Figure 13 ), the specific operations are as follows: S1. Information encryption and writing S1.1. First, the encrypted information "smart" is compiled into a standard QR code digital matrix through an algorithm. This QR code is the carrier of information.

[0071] S1.2. Making a photomask: Make the QR code matrix into a photomask.

[0072] S1.3. Place the photomask tightly against the hydrogel prepared in Example 3. Irradiate with 365 nm UV light for 10 minutes. The UV light can only pass through the transparent areas of the photomask and illuminate the 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 features. Neither the human eye nor a mobile phone camera can detect any pattern or density differences. The entire gel looks like an ordinary transparent gasket, making the hidden information completely invisible. Smartphones cannot directly detect the hidden information.

[0074] S3. Information reading and verification ("development" and decryption): When verification is required, ultraviolet light is used to illuminate the hydrogel surface, and a clear and bright QR code pattern will appear.

[0075] S4. Smartphone Recognition: A 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." At this point, the encrypted information is successfully and conveniently read.

[0076] This application utilizes the dynamic information writing and encryption characteristics 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 advantages.

Claims

1. A method for preparing a stimulus-responsive self-repairing fluorescent hydrogel, characterized by: The steps include: S1, take hexadecyltrimethylammonium chloride and dissolve it in distilled water, stir and react at 50-80 ° C for 3-7 hours; S2, adding anthracene-based fluorescent molecule 9-anthracene methyl methacrylate to the surfactant solution prepared in step 1, stirring and reacting at 50-80 ° C for 12-24 hours to obtain a micellar solution; S3. Measure the micellar solution in step 2, add acrylic acid, sonicate for 5 to 10 minutes, add zirconium chloride, continue stirring and reacting at room temperature for 15 to 60 minutes, bubble the mixed solution with nitrogen for 10 to 30 minutes, and then add potassium persulfate at room temperature; S4. Transfer the prepared pregel solution into a polytetrafluoroethylene mold, seal it, and place it in a drying oven at 60-80°C for 8-12 hours to obtain a hydrogel.

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

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

4. The method for preparing the stimulus-responsive self-repairing fluorescent hydrogel according to claim 1, wherein: In S3, the volume ratio of acrylic acid and micelle solution was (1.0-1.3) mL:2.8 mL.

5. The method for preparing the stimulus-responsive self-repairing fluorescent hydrogel according to claim 1, characterized in that: In S3, the amount of zirconium chloride added is 11.65-46.6 mg.

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

7. A stimulus-responsive self-repairing fluorescent hydrogel prepared by the preparation method according to any one of claims 1 to 6.

8. The stimulus-responsive self-repairing fluorescent hydrogel according to claim 7, characterized in that: The hydrogel presents a sponge-like porous three-dimensional network structure, in which carbon, oxygen and zirconium elements are evenly distributed. The hydrogel has self-repairing ability and fluorescence stimulation response performance.

9. Application of a stimulus-responsive self-repairing fluorescent hydrogel prepared by the preparation method according to any one of claims 1 to 6 in the field of intelligent information anti-counterfeiting.

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