Process for the preparation of metal complex hydrogels and organogels containing acylhydrazone hydrophobic monomers

Abstract

The application discloses a preparation method of a metal complex hydrogel containing an acylhydrazone hydrophobic monomer, and the method comprises the following steps: uniformly mixing (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl) acrylamide, acrylic acid, polyethylene glycol diacrylate and an initiator in an organic solvent, and performing free radical polymerization on a prepolymer solution to form an organic gel; the organic gel is replaced by a solvent to form a hydrogel; and then the hydrogel is immersed in a metal ion solution to obtain the metal complex hydrogel. The application further discloses a preparation method of an organic gel, and the method comprises the following steps: uniformly mixing an acylhydrazone structure monomer, acrylic acid, polyethylene glycol diacrylate and an initiator in an organic solvent to obtain a prepolymer solution, and performing free radical polymerization on the prepolymer solution to form the organic gel. The synthesis of the organic gel of the application does not need a surfactant to wrap the acylhydrazone structure, the synthesis method is simple, and the prepared hydrogel has excellent mechanical properties and fluorescence properties.

Description

TECHNICAL FIELD

[0001] The present application relates to a metal complex hydrogel, in particular to a preparation method of a metal complex hydrogel containing an acylhydrazone hydrophobic monomer and a preparation method of an organic gel. BACKGROUND

[0002] Hydrogels have a three-dimensional network structure formed by covalent bonds and / or physical interactions. Due to its high hydrophilicity, good water retention capacity and unparalleled biocompatibility, hydrogels have attracted widespread attention in the fields of biomedical, sensing and identification, and electronic devices. However, traditional hydrogels have poor mechanical properties, lack of functionality, and slow response to stimuli, which limits the practical application of hydrogels.

[0003] In order to solve the problem of poor mechanical properties of hydrogels, the gelation strategy is often changed to improve the mechanical properties of hydrogels, such as double network hydrogels, nanocomposites, polymer microsphere composites, and Tetra-PEG hydrogels. These strategies use covalent and / or non-covalent bonds to increase the crosslinking density and strength of the hydrogel, thereby improving the mechanical strength of the hydrogel. Among them, non-covalent bonds as a reversible physical crosslinking can give the hydrogel an energy dissipation mechanism to enhance its ductility and fatigue resistance. At the same time, due to the dynamicity and configurability of non-covalent bonds, the hydrogel can be given corresponding functions according to the needs, such as stimulus responsiveness, shape memory and anti-swelling.

[0004] In order to give the hydrogel functionality, metal ligands are generally introduced to complex with metal ions, and the state of the hydrogel is changed by the complexation of the ion pair ligand, so that the hydrogel undergoes visual fluorescence color or intensity changes in different environments.

[0005] Due to the incompatibility of hydrophobic monomers with water molecules, it is difficult to directly introduce hydrophobic monomers into the hydrogel system. The commonly used and effective methods include solvent exchange method, micellar copolymerization method and construction of amphiphilic molecules. The solvent exchange method for preparing hydrophobic associated hydrogel usually dissolves the hydrophobic monomer and the hydrophilic monomer in a good solvent at the same time to form an organic gel in situ, and then immerses the organic gel in pure water which is a poor solvent for the hydrophobic monomer to perform solvent exchange, thereby obtaining a hydrophobic associated hydrogel.

[0006] The acylhydrazone structure has good coordination ability and excellent biocompatibility. The introduction of the acylhydrazone structure into the hydrogel system can complex with metal ions to produce fluorescence response, but the gelation process of this type of hydrogel has limitations on the type of surfactant. Different acylhydrazone structures need to select the corresponding surfactant, otherwise it cannot be wrapped to form micelles, which limits the application of hydrogels containing acylhydrazone hydrophobic structures. SUMMARY

[0007] In order to overcome the above-mentioned defects and shortcomings of the prior art, the present application aims to provide a preparation method of metal complex hydrogel containing acylhydrazone hydrophobic monomers, which does not need to wrap the acylhydrazone structure with a surfactant in the whole process of synthesizing the organic gel, and the synthesis method is simple.

[0008] Another object of the present application is to provide a preparation method of organic gel, which does not need to wrap the acylhydrazone structure with a surfactant in the whole process, and the synthesis method is simple.

[0009] The object of the present application is achieved by the following technical solutions.

[0010] The preparation method of metal complex hydrogel containing acylhydrazone hydrophobic monomers comprises the following steps:

[0011] The organic gel is soaked in deionized water for 2-4 days to perform solvent exchange, and then the hydrogel is obtained; and then the hydrogel is soaked in a metal ion solution for 6-12 h to obtain the metal complex hydrogel containing acylhydrazone hydrophobic monomers.

[0012] The organic gel is prepared by the following steps:

[0013] (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl) acrylamide, acrylic acid, polyethylene glycol diacrylate and an initiator are uniformly mixed in an organic solvent to obtain a prepolymer solution, and the prepolymer solution is subjected to free radical polymerization to form the organic gel.

[0014] Preferably, the specific preparation process of the organic gel comprises:

[0015] 1) 4-Aminobenzhydrazide and 4-phenylbenzaldehyde are added to a first organic solvent, a catalyst glacial acetic acid is added dropwise, and stirring reaction is carried out at 65-85 DEG C under nitrogen protection for 3-12 h; after the reaction is completed, the crude product is obtained by filtration, washed and dried to obtain (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzhydrazide;

[0016] 2) (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzhydrazide and triethylamine are dissolved in a second organic solvent, and after uniform stirring, acryloyl chloride is added dropwise, and reaction is carried out at 50-70 DEG C under nitrogen atmosphere for 12-24 h; after the reaction is completed, precipitation is carried out, the solvent is removed by filtration, and the crude product is recrystallized and dried to obtain (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl) acrylamide;

[0017] 3) mixing (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide, acrylic acid, polyethylene glycol diacrylate in a third organic solvent, adding initiator after filling with nitrogen, polymerizing at 65-75°C for 4-8h to obtain an organic gel.

[0018] Preferably, the metal ion solution is Zn 2+ , Cd 2+ , Al 3+ , Pb 2+ or Mn 2+ solution, the concentration is 0.0125-0.2M; 1-3ml of metal ion solution is added per gram of hydrogel.

[0019] Preferably, in step 1), the molar ratio of 4-aminobenzhydrazide and 4-phenylbenzaldehyde is 1:(0.8-1.2), and the amount of glacial acetic acid added per millimole of 4-aminobenzhydrazide is 0.1-0.2ml.

[0020] Preferably, in step 2), the molar ratio of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzhydrazide and acryloyl chloride is 1:2-1:4, and the molar ratio of acryloyl chloride to triethylamine is 1:1.2-1:1.6.

[0021] Preferably, in step 2), in step 3), the molar concentration of acrylic acid in the third solvent is 3-6mM, the molar ratio of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide and acrylic acid is 1:20-1:104, the molar concentration of polyethylene glycol diacrylate is 0.5-2% of the molar concentration of acrylic acid, and the amount of initiator is 1-3% of the mass of acrylic acid.

[0022] Preferably, the initiator is azobisisobutyronitrile, potassium persulfate or ammonium persulfate.

[0023] Preferably, the polyethylene glycol diacrylate is one or more of polyethylene glycol diacrylate with a relative molecular mass of 400, 600 or 1000.

[0024] Preferably, in step 1), the first organic solvent is one or more of methanol, ethanol, acetonitrile; in step 2), the second organic solvent is N-methylpyrrolidone; in step 3), the third organic solvent is one or both of N,N-dimethylformamide and dimethyl sulfoxide.

[0025] Preferably, in step 1), the washing is washing with methanol; in step 2), the precipitation is precipitation in water, and the recrystallization is recrystallization in n-hexane after the crude product is dissolved in pyridine; in step 4), each gram of the organic gel is soaked in 100-200 ml of deionized water.

[0026] Preferably, in step 5), the metal ion solution is a Zn 2+ , Cd 2+ , Al 3+ , Pb 2+ or Mn 2+ solution, which is prepared by dissolving zinc acetate dihydrate, cadmium chloride, aluminum nitrate nonahydrate, lead acetate anhydrous or manganese nitrate tetrahydrate in deionized water, respectively, and has a concentration of 0.0125-0.2 M, and the amount of the metal solution added to each gram of the hydrogel is 1-3 ml.

[0027] A preparation method of an organic gel, comprising the following steps:

[0028] Mixing an acylhydrazone structural monomer, acrylic acid, polyethylene glycol diacrylate and an initiator uniformly in an organic solvent to obtain a pre-polymerization liquid, and subjecting the pre-polymerization liquid to free radical polymerization to form an organic gel.

[0029] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0030] (1) The preparation method of the metal complex hydrogel containing acylhydrazone hydrophobic monomers of the present application does not need a surfactant to wrap the acylhydrazone structure in the whole process of synthesizing the organic gel, and the synthesis method is simple.

[0031] (2) The preparation method of the metal complex hydrogel containing acylhydrazone hydrophobic monomers of the present application introduces the acylhydrazone hydrophobic monomers into the hydrogel system with acrylic acid as the hydrophilic monomer by a solvent exchange method, and the hydrophobic association between the acylhydrazone ligands and the metal complexation between the Zn 2+ ions and the ligands can both improve the mechanical strength of the hydrogel. In addition, the introduction of the acylhydrazone hydrophobic monomers also endows the hydrogel with fluorescence properties and ionic responsiveness, and there is an obvious change in fluorescence properties before and after the metal complexation.

[0032] (3) The preparation method of the metal complex hydrogel containing acylhydrazone hydrophobic monomers of the present application can adjust the proportion of the acylhydrazone hydrophobic monomers and the concentration of the metal ions to meet different mechanical property requirements.

[0033] (4) The preparation method of the metal complex hydrogel containing acylhydrazone hydrophobic monomers of the present application has a simple gelation method and mild preparation conditions, and can be applied to the introduction of most acylhydrazone hydrophobic monomers into the hydrogel system without limitation in the type and concentration.

[0034] (5) The metal complex hydrogel containing acylhydrazone hydrophobic monomers prepared by the present application has a tensile stress of 410-865 kPa and a maximum tensile strain of 324-559%.

[0035] (6) The organic gel prepared by the present application has obvious fluorescence change and visual characteristics before and after complexing with metal ions, and has good recognition ability.

[0036] (7) The metal complex hydrogel containing acylhydrazone hydrophobic monomers of the present application has adjustable fluorescence intensity, can save and encrypt various information, and can be applied in the fields of intelligent optical devices, ion detection, sensors and the like. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The metal ion response principle diagram of the hydrogel prepared by the present application.

[0038] Figure 2 The d6-DMSO solvent spectrum of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzohydrazide obtained in Example 1 of the present application. 1 H NMR spectrum.

[0039] Figure 3 The d6-DMSO solvent spectrum of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide obtained in Example 1 of the present application. 1 H NMR spectrum.

[0040] Figure 4 The tensile stress strain diagram of the original hydrogel obtained in Example 1, Example 2 and Example 3 of the present application.

[0041] Figure 5 The tensile stress strain diagram of the metal complex hydrogel obtained in Example 1, Example 6 and Example 7 of the present application.

[0042] Figure 6 The fluorescence emission spectrum of the hydrogel obtained in Example 1, Example 4, Example 5, Example 6 and Example 7 of the present application before and after complexing with metal ions.

[0043] Figure 7 The effect diagram of the original hydrogel obtained in Example 1 of the present application using Zn 2+ performs multiple fluorescence printing. DETAILED DESCRIPTION

[0044] The present application will be further described in detail below in combination with examples, but the embodiments of the present application are not limited thereto.

[0045] In the following examples, the properties of the hydrogels were tested using the following methods, unless otherwise specified:

[0046] (1) Tensile property test: The rectangular hydrogel samples were tested on a KJ-1065A-T tensile strength tester at room temperature. The actual measured length of the sample was 10 mm, the thickness was 1 mm, the width was 4 mm, and the tensile rate was 100 mm / min.

[0047] (2) Fluorescence property test: The fluorescence test of the hydrogel was performed on a Hitachi F-4500 fluorescence spectrophotometer. The size of the tested hydrogel sample was 15 mm x 7.5 mm x 1 mm, which was fixed between two glass sheets for testing. The excitation wavelength was 377 nm, and the excitation and emission slits were 10 nm.

[0048] (3) Fluorescent printing property test of the hydrogel: A mold engraved with the word "SCUT" was immersed in a 0.3 mol / L Zn2+ solution for 5 s, and the mold was placed above the hydrogel for 5 s. The mold was removed, and the surface of the hydrogel was observed under UV light at 365 nm to determine whether the word "SCUT" with strong yellow fluorescence was present. This determined whether the prepared hydrogel could be used for fluorescent printing.

[0049] Example 1

[0050] (1) Preparation of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4- aminobenzohydrazide: 10 mmol of 4-aminobenzohydrazide and 10 mmol of 4-phenylbenzaldehyde were added to methanol, 1 ml of glacial acetic acid was added dropwise as a catalyst, and the reaction was stirred at 65°C under nitrogen for 6 h. After the reaction was completed, the crude product was filtered, washed in methanol, filtered, and dried. The (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzohydrazide had a d6-DMSO solvent 1 H NMR spectrum as Figure 2 shown.

[0051] (2) Preparation of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1- carbonyl)phenyl)acrylamide: 2 mmol of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4- aminobenzohydrazide and 4.8 mmol of triethylamine were dissolved in N-methylpyrrolidone, and 4 mmol of acryloyl chloride was added dropwise after stirring. The reaction was carried out at 65°C under nitrogen for 12 h. After the reaction was completed, the crude product was precipitated in water, filtered, dissolved in pyridine, recrystallized in n-hexane, and dried. The (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide had a d6-DMSO solvent 1 H NMR spectrum asFigure 3

[0052] (3) Preparation of organic gel: 10 mg (5 wt%) (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide, 200 mg acrylic acid, 60 mg polyethylene glycol diacrylate (relative molecular mass 400) were mixed uniformly in 1 ml dimethyl sulfoxide, 3 mg azobisisobutyronitrile was added after filling with nitrogen, and polymerization was carried out at 65°C for 6 h to obtain an organic gel.

[0053] (4) Preparation of hydrogel: the organic gel was immersed in 100 ml deionized water at room temperature for 2 days for solvent exchange, and the water was changed every 12 h to obtain a hydrogel.

[0054] (5) Preparation of metal complex hydrogel: the hydrogel was immersed in 1 ml of 0.05M Zn 2+ solution at room temperature for 6 h to obtain a metal complex hydrogel.

[0055] Figure 1 The metal ion response principle of the hydrogel prepared in the application is shown in the dotted part of the figure, which is the dynamic metal coordination bond formed by the acylhydrazone structure and Zn 2+ , which improves the mechanical properties of the hydrogel. When the hydrogel is stressed, it can act as an energy dissipation mechanism in the hydrogel, thereby improving its ductility.

[0056] From Figure 4 , it can be seen that the tensile stress of the hydrogel is 185.8 kPa, and the tensile strain is 129%. In combination with the stress-strain curves of the hydrogels in Example 2 and Example 3, Figure 4 , the hydrophobic association between the hydrophobic monomers significantly enhances the mechanical properties of the hydrogel, because the hydrophobic association points existing in the hydrogel system not only increase the crosslinking density, but also can act as an energy dissipation mechanism in the hydrogel when stressed, thereby improving its ductility. Therefore, the mechanical properties can be adjusted by changing the proportion of acylhydrazone-containing hydrophobic monomers to meet the needs of different application scenarios.

[0057] The hydrogel is immersed in solutions with different concentrations of metal ions to obtain metal complex hydrogels with different mechanical properties, as shown in Figure 5 , when the concentration of metal ions is 0.05M, the tensile stress is 242.6 kPa, and the tensile strain is 203%, and as the concentration of metal ions increases, the tensile stress and tensile strain of the metal complex hydrogel gradually increase, and when the concentration of metal ions is 0.2M, the tensile stress is 865 kPa, and the tensile strain is 559%. Therefore, the mechanical properties can also be adjusted by changing the concentration of metal ions to meet the needs of different application scenarios.

[0058] From​Figure 6 It can be seen that the hydrogel exhibits obvious fluorescence changes after metal ion complexation, with the fluorescence intensity increasing with the addition of Zn. 2+ With increasing concentration, the fluorescence intensity of the metal-complexed hydrogel gradually increases. When Zn... 2+ When the concentration increased from 0.0125 M to 0.2 M, the fluorescence intensity of the hydrogel increased by 448%. This indicates that the hydrogel exhibits good fluorescence intensity for Zn. 2+ It exhibits good selective response and its fluorescence intensity is well tunable, making it a potential candidate for applications in ion detection sensors.

[0059] Depend on Figure 7 It is known that, based on the fluorescence modulation properties of the hydrogel, this hydrogel can be used for erasable fluorescent writing and information encryption and storage. (The text then abruptly shifts to a seemingly unrelated topic: "Dip Zn...") 2+ Using a cotton swab soaked in the solution as a pen, the letter "H" can be drawn quickly and clearly on the hydrogel within 1 second. Then, the fluorescent information can be erased within 30 seconds using an EDTA solution, and the letter "N" can be written again using the same method. This demonstrates that the fluorescent writing function of the hydrogel has good contrast and reversibility.

[0060] Example 2

[0061] (1) Preparation of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine: 10 mmol of 4-aminobenzoylhydrazine and 10 mmol of 4-phenylbenzaldehyde were added to methanol, and 1 ml of glacial acetic acid was added dropwise as a catalyst. The reaction was carried out under nitrogen protection at 65 °C with stirring for 6 h. After the reaction was completed, the crude product was obtained by filtration, washed in methanol, filtered, and dried. (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine was prepared using d6-DMSO as solvent. 1 H NMR spectrum as shown Figure 2 As shown.

[0062] (2) Preparation of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide: 2 mmol of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine and 4.8 mmol of triethylamine were dissolved in N-methylpyrrolidone, stirred until homogeneous, and then 4 mmol of acryloyl chloride was added dropwise. The reaction was carried out at 65 °C for 12 h under a nitrogen atmosphere. After the reaction was completed, the product was precipitated in water, filtered to obtain the crude product, dissolved in pyridine, recrystallized in n-hexane, and dried. (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide was prepared using d6-DMSO as solvent. 1 H NMR spectrum as shown Figure 3 As shown.

[0063] (3) Preparation of organic gel: 20 mg (10 wt%) (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide, 200 mg acrylic acid, and 60 mg polyethylene glycol diacrylate (relative molecular mass 400) were mixed evenly in 1 ml of dimethyl sulfoxide, and after purging with nitrogen, 3 mg of azobisisobutyronitrile was added. Polymerization was carried out at 65 °C for 6 h to obtain organic gel.

[0064] (4) Preparation of hydrogel: The organic gel was soaked in 100ml of deionized water at room temperature for 2 days for solvent exchange, and the water was changed every 12 hours to obtain the hydrogel.

[0065] (5) Preparation of metal complex hydrogel: The hydrogel was immersed in 1 ml of 0.0125 M Zn at room temperature. 2+ After 6 hours in the solution, a metal complex hydrogel was obtained.

[0066] Depend on Figure 4 It can be seen that the tensile stress of the hydrogel in Example 2 is 290.8 kPa, and the tensile strain is 215%; combined with Figure 4 As shown in the stress-strain curves of the hydrogels in Examples 1 and 3, the hydrophobic association between the hydrophobic monomers significantly enhances the mechanical properties of the hydrogel. This is because the hydrophobic association points in the hydrogel system not only increase the crosslinking density but also act as an energy dissipation mechanism under stress, thereby improving its ductility. Therefore, the mechanical properties can be adjusted by changing the proportion of acylhydrazone-containing hydrophobic monomers to meet the needs of different application scenarios. Furthermore, the hydrogel can be used for erasable fluorescent writing and information encryption and storage. (The last sentence appears to be incomplete and possibly refers to a different application.) 2+ Using a cotton swab soaked in the solution as a pen, the letter "H" can be drawn quickly and clearly on the hydrogel within 1 second. Then, the fluorescent information can be erased within 30 seconds using an EDTA solution, and the letter "N" can be written again using the same method. This demonstrates that the fluorescent writing function of the hydrogel has good contrast and reversibility.

[0067] Example 3

[0068] (1) Preparation of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine: 10 mmol of 4-aminobenzoylhydrazine and 10 mmol of 4-phenylbenzaldehyde were added to methanol, and 1 ml of glacial acetic acid was added dropwise as a catalyst. The reaction was carried out under nitrogen protection at 65 °C with stirring for 6 h. After the reaction was completed, the crude product was obtained by filtration, washed in methanol, filtered, and dried. (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine was prepared using d6-DMSO as solvent. 1 H NMR spectrum as shown Figure 2As shown.

[0069] (2) Preparation of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide: 2 mmol of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine and 4.8 mmol of triethylamine were dissolved in N-methylpyrrolidone, stirred until homogeneous, and then 4 mmol of acryloyl chloride was added dropwise. The reaction was carried out at 65 °C for 12 h under a nitrogen atmosphere. After the reaction was completed, the product was precipitated in water, filtered to obtain the crude product, dissolved in pyridine, recrystallized in n-hexane, and dried. (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide was prepared using d6-DMSO as solvent. 1 H NMR spectrum as shown Figure 3 As shown.

[0070] (3) Preparation of organic gel: 30 mg (15 wt%) (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide, 200 mg acrylic acid, and 60 mg polyethylene glycol diacrylate (relative molecular mass 400) were mixed evenly in 1 ml of dimethyl sulfoxide. After purging with nitrogen, 3 mg of azobisisobutyronitrile was added, and polymerization was carried out at 65 °C for 6 h to obtain organic gel.

[0071] (4) Preparation of hydrogel: The organic gel was soaked in 100ml of deionized water at room temperature for 2 days for solvent exchange, and the water was changed every 12 hours to obtain the hydrogel.

[0072] (5) Preparation of metal complex hydrogel: The hydrogel was immersed in 1 ml of 0.0125 M Zn at room temperature. 2+ After 6 hours in the solution, a metal complex hydrogel was obtained.

[0073] Depend on Figure 4 It can be seen that the tensile stress of the hydrogel in Example 3 is 410.2 kPa, and the tensile strain is 324%; combined with Figure 4 As shown in the stress-strain curves of the hydrogels in Examples 1 and 2, the hydrophobic association between the hydrophobic monomers significantly enhances the mechanical properties of the hydrogel. This is because the hydrophobic association points in the hydrogel system not only increase the crosslinking density but also act as an energy dissipation mechanism under stress, thereby improving its ductility. Therefore, the mechanical properties can be adjusted by changing the proportion of acylhydrazone-containing hydrophobic monomers to meet the needs of different application scenarios. Furthermore, the hydrogel can be used for erasable fluorescent writing and information encryption and storage. (The last sentence appears to be incomplete and possibly refers to a different application.) 2+The solution of the cotton swab as a pen can quickly and clearly draw the letter "H" on the hydrogel within 1 s. Then, the fluorescent information can be erased within 30 s by using the EDTA solution, and the letter "N" can be written again by using the same method. Thus, the hydrogel has good contrast and reversibility in the fluorescent writing function.

[0074] Example 4

[0075] (1) Preparation of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4- aminobenzohydrazide: 10 mmol of 4-aminobenzohydrazide and 10 mmol of 4-phenylbenzaldehyde were added to methanol, 1 ml of glacial acetic acid was added dropwise as a catalyst, and the reaction was stirred at 65°C under nitrogen protection for 6 h; after the reaction was completed, the crude product was filtered, washed with methanol, filtered, and dried. The (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzohydrazide was dissolved in d6-DMSO as a solvent. 1 The H NMR spectrum is shown in Figure 2 .

[0076] (2) Preparation of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1- carbonyl)phenyl)acrylamide: 2 mmol of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4- aminobenzohydrazide and 4.8 mmol of triethylamine were dissolved in N- methylpyrrolidone, and 4 mmol of acryloyl chloride was added dropwise after stirring uniformly, and the reaction was carried out at 65°C under nitrogen atmosphere for 12 h; after the reaction was completed, precipitation was carried out in water, the crude product was filtered, dissolved in pyridine, recrystallized in n-hexane, and dried. The (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide was dissolved in d6-DMSO as a solvent. 1 The H NMR spectrum is shown in Figure 3 .

[0077] (3) Preparation of an organic gel: 10 mg (5 wt%) of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide, 200 mg of acrylic acid, and 60 mg of polyethylene glycol diacrylate (relative molecular mass of 400) were uniformly mixed in 1 ml of dimethyl sulfoxide, 3 mg of azobisisobutyronitrile was added after nitrogen was filled, and the polymerization was carried out at 65°C for 6 h to obtain an organic gel.

[0078] (4) Preparation of a hydrogel: the organic gel was immersed in 100 ml of deionized water at room temperature for 2 days for solvent exchange, and the water was changed every 12 h to obtain a hydrogel.

[0079] (5) Preparation of metal complex hydrogel: The hydrogel was immersed in 1 ml of 0.0125 M Zn at room temperature. 2+ After 6 hours in the solution, a metal complex hydrogel was obtained.

[0080] Depend on Figure 4 It can be seen that the tensile stress of the hydrogel in Example 4 is 185.8 kPa, and the tensile strain is 129%. Figure 6 It can be seen that the hydrogel exhibits obvious fluorescence changes after metal ion complexation, with the fluorescence intensity increasing with the addition of Zn. 2+ With increasing concentration, the fluorescence intensity of the metal-complexed hydrogel gradually increases. This indicates that the hydrogel exhibits high fluorescence intensity for Zn. 2+ It exhibits good selective response and its fluorescence intensity is well tunable, showing potential application prospects in ion detection sensors. Furthermore, the hydrogel can be used for erasable fluorescent writing and information encryption and storage. (The last sentence appears to be incomplete and unrelated to the preceding text. It likely refers to a process involving Zn-coated materials.) 2+ Using a cotton swab soaked in the solution as a pen, the letter "H" can be drawn quickly and clearly on the hydrogel within 1 second. Then, the fluorescent information can be erased within 30 seconds using an EDTA solution, and the letter "N" can be written again using the same method. This demonstrates that the fluorescent writing function of the hydrogel has good contrast and reversibility.

[0081] Example 5

[0082] (1) Preparation of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine: 10 mmol of 4-aminobenzoylhydrazine and 10 mmol of 4-phenylbenzaldehyde were added to methanol, and 1 ml of glacial acetic acid was added dropwise as a catalyst. The reaction was carried out under nitrogen protection at 65 °C with stirring for 6 h. After the reaction was completed, the crude product was obtained by filtration, washed in methanol, filtered, and dried. (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine was prepared using d6-DMSO as solvent. 1 H NMR spectrum as shown Figure 2 As shown.

[0083] (2) Preparation of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide: 2 mmol of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine and 4.8 mmol of triethylamine were dissolved in N-methylpyrrolidone, stirred until homogeneous, and then 4 mmol of acryloyl chloride was added dropwise. The reaction was carried out at 65 °C for 12 h under a nitrogen atmosphere. After the reaction was completed, the product was precipitated in water, filtered to obtain the crude product, dissolved in pyridine, recrystallized in n-hexane, and dried. (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide was prepared using d6-DMSO as solvent. 1 H NMR spectrum as shownFigure 3 as shown.

[0084] (3) Preparation of organic gel: 10 mg (5 wt%) of (E)-N-(4-(2-([1,1'-biphenyl]-4- ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide, 200 mg of acrylic acid, 60 mg of polyethylene glycol diacrylate (relative molecular mass of 400) were mixed uniformly in 1 ml of dimethyl sulfoxide, 3 mg of azobisisobutyronitrile was added after filling with nitrogen, and polymerization was carried out at 65 °C for 6 h to obtain an organic gel.

[0085] (4) Preparation of hydrogel: the organic gel was immersed in 100 ml of deionized water at room temperature for solvent exchange for 2 days, and the water was changed every 12 h to obtain a hydrogel.

[0086] (5) Preparation of metal complexed hydrogel: the hydrogel was immersed in 1 ml of 0.025 M Zn 2+ solution at room temperature for 6 h to obtain a metal complexed hydrogel.

[0087] It can be known from Figure 4 that the tensile stress of the hydrogel of Example 5 is 185.8 kPa, and the tensile strain is 129%. It can be known from Figure 6 that the hydrogel presents a significant fluorescence change after metal ion complexation, and the fluorescence intensity of the metal complexed hydrogel gradually increases with the increase of the concentration of Zn 2+ . It shows that the hydrogel has good selectivity to Zn 2+ , and the fluorescence intensity has good tunability, which has potential application prospect in ion detection sensors. In addition, the hydrogel can be used for erasable fluorescent writing and information encryption and storage. The cotton swab dipped in the Zn 2+ solution is used as a pen, and the letter "H" can be quickly and clearly drawn on the hydrogel within 1 s. Then, the fluorescent information can be erased within 30 s by using EDTA solution, and the letter "N" can be written again by using the same method. It can be known that the fluorescent writing function of the hydrogel has good contrast and reversibility.

[0088] Example 6

[0089] (1) Preparation of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzohydrazide: 10 mmol of 4-aminobenzohydrazide and 10 mmol of 4-phenylbenzaldehyde were added to methanol, 1 ml of glacial acetic acid was added dropwise as a catalyst, and the reaction was stirred at 65 °C under nitrogen protection for 6 h; after the reaction was completed, the crude product was filtered, washed in methanol, filtered and dried. The H NMR spectrum of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzohydrazide with d6-DMSO as the solvent is as shown in 1 . Figure 2As shown.

[0090] (2) Preparation of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide: 2 mmol of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine and 4.8 mmol of triethylamine were dissolved in N-methylpyrrolidone, stirred until homogeneous, and then 4 mmol of acryloyl chloride was added dropwise. The reaction was carried out at 65 °C for 12 h under a nitrogen atmosphere. After the reaction was completed, the product was precipitated in water, filtered to obtain the crude product, dissolved in pyridine, recrystallized in n-hexane, and dried. (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide was prepared using d6-DMSO as solvent. 1 H NMR spectrum as shown Figure 3 As shown.

[0091] (3) Preparation of organic gel: 10 mg (5 wt%) (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide, 200 mg acrylic acid, and 60 mg polyethylene glycol diacrylate (relative molecular mass 400) were mixed evenly in 1 ml of dimethyl sulfoxide. After purging with nitrogen, 3 mg of azobisisobutyronitrile was added, and polymerization was carried out at 65 °C for 6 h to obtain organic gel.

[0092] (4) Preparation of hydrogel: The organic gel was soaked in 100ml of deionized water at room temperature for 2 days for solvent exchange, and the water was changed every 12 hours to obtain the hydrogel.

[0093] (5) Preparation of metal complex hydrogel: The hydrogel was immersed in 1 ml of 0.1 M Zn at room temperature. 2+ After 6 hours in the solution, a metal complex hydrogel was obtained.

[0094] Depend on Figure 4 and Figure 5 It can be seen that the tensile stress of the hydrogel in Example 6 is 185.8 kPa, and the tensile strain is 129%; the tensile stress of the metal complex hydrogel is 437.3 kPa, and the tensile strain is 517%. Figure 6 It can be seen that the hydrogel exhibits obvious fluorescence changes after metal ion complexation, with the fluorescence intensity increasing with the addition of Zn. 2+ With increasing concentration, the fluorescence intensity of the metal-complexed hydrogel gradually increases. This indicates that the hydrogel exhibits high fluorescence intensity for Zn. 2+ It exhibits good selective response and its fluorescence intensity is well tunable, showing potential application prospects in ion detection sensors. Furthermore, the hydrogel can be used for erasable fluorescent writing and information encryption and storage. (The last sentence appears to be incomplete and unrelated to the preceding text. It likely refers to a process involving Zn-coated materials.) 2+The cotton swab solution was used as a pen to draw the letter "H" on the hydrogel in 1 s. Then, the fluorescent information was erased in 30 s using EDTA solution, and the letter "N" was written again using the same method. Thus, the fluorescent writing function of the hydrogel had good contrast and reversibility.

[0095] Example 7

[0096] (1) Preparation of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4- aminobenzohydrazide: 10 mmol of 4-aminobenzohydrazide and 10 mmol of 4-phenylbenzaldehyde were added to methanol, 1 ml of glacial acetic acid was added dropwise as a catalyst, and the reaction was stirred at 65°C under nitrogen protection for 6 h. After the reaction was completed, the crude product was filtered, washed with methanol, filtered, and dried. The (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4-aminobenzohydrazide was dissolved in d6-DMSO as a solvent. 1 The H NMR spectrum is shown in Figure 2 .

[0097] (2) Preparation of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1- carbonyl)phenyl)acrylamide: 2 mmol of (E)-N'-([1,1'-biphenyl]-4-ylmethylidene)-4- aminobenzohydrazide and 4.8 mmol of triethylamine were dissolved in N- methylpyrrolidone, 4 mmol of acryloyl chloride was added dropwise after stirring, and the reaction was carried out at 65°C under nitrogen atmosphere for 12 h. After the reaction was completed, it was precipitated in water, filtered to obtain the crude product, dissolved in pyridine, recrystallized in n-hexane, and dried. The (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide was dissolved in d6-DMSO as a solvent. 1 The H NMR spectrum is shown in Figure 3 .

[0098] (3) Preparation of organic gel: 10 mg (5 wt%) of (E)-N-(4-(2-([1,1'-biphenyl]-4- ylmethylidene)hydrazine-1-carbonyl)phenyl)acrylamide, 200 mg of acrylic acid, and 60 mg of polyethylene glycol diacrylate (relative molecular mass 400) were mixed uniformly in 1 ml of dimethyl sulfoxide, 3 mg of azobisisobutyronitrile was added after nitrogen was filled, and polymerization was carried out at 65°C for 6 h to obtain an organic gel.

[0099] (4) Preparation of hydrogel: The organic gel was immersed in 100 ml of deionized water at room temperature for 2 days for solvent exchange, and the water was changed every 12 h to obtain a hydrogel.

[0100] (5) Preparation of metal complex hydrogel: The hydrogel was immersed in 1 ml of 0.2M Zn2+ 6h in solution, metal complex hydrogel was obtained.

[0101] From Figure 4 and Figure 5 It can be seen that the tensile stress of the hydrogel of Example 7 is 185.8 kPa, and the tensile strain is 129%; the tensile stress of the metal complex hydrogel is 865 kPa, and the tensile strain is 559%. It can be seen from Figure 6 that the hydrogel shows obvious fluorescence change after complexing with metal ions, and the fluorescence intensity of the metal complex hydrogel gradually increases with the increase of the concentration of Zn 2+ . It shows that the hydrogel has good selective responsiveness to Zn 2+ , and the fluorescence intensity has good tunability, which has potential application prospect in ion detection sensors. In addition, the hydrogel can be used for erasable fluorescent writing and information encryption and storage. The cotton swab dipped in Zn 2+ solution is used as a pen, and the letter "H" can be quickly and clearly drawn on the hydrogel within 1s. Then, the fluorescent information can be erased within 30s by using EDTA solution, and the letter "N" can be written again by using the same method. It can be seen that the fluorescent writing function of the hydrogel has good contrast and reversibility.

[0102] The present application introduces acylhydrazone hydrophobic monomers into the hydrogel system by solvent exchange method to improve the mechanical properties, and endows the hydrogel with fluorescence properties through the complexation of metal ions and acylhydrazone hydrophobic monomers, and at the same time realizes the functions of fluorescent writing and information encryption and storage, etc., so that it has great application value in the fields of ion detection, flexible sensor, optical device, etc.

[0103] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, and all shall be included in the protection scope of the present application.

Claims

1. A method for preparing a metal complex hydrogel containing an acylhydrazone hydrophobic monomer, characterized in that, Includes the following steps: The organic gel was soaked in deionized water for 2-4 days to exchange solvents and obtain a hydrogel; then the hydrogel was soaked in a metal ion solution for 6-12 hours to obtain a metal complex hydrogel containing an acylhydrazone hydrophobic monomer. The metal ion solution is Zn. 2+ Cd 2+ Al 3+ Pb 2+ or Mn 2+ Solution; the organic gel is prepared by the following steps: (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide, acrylic acid, polyethylene glycol diacrylate and initiator are mixed evenly in an organic solvent to obtain a prepolymer solution. The prepolymer solution undergoes free radical polymerization to form an organic gel. The relative molecular mass of the polyethylene glycol diacrylate is 400.

2. The method for preparing the metal complex hydrogel containing an acylhydrazone hydrophobic monomer according to claim 1, characterized in that, The specific preparation process of the organic gel includes: 1) Add 4-aminobenzoyl hydrazide and 4-phenylbenzaldehyde to the first organic solvent, add glacial acetic acid as a catalyst dropwise, and stir the reaction at 65~85℃ for 3~12h under nitrogen protection; after the reaction is completed, filter to obtain crude product, wash and dry to obtain (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoyl hydrazide; 2) Dissolve (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine and triethylamine in a second organic solvent, stir until homogeneous, and then add acryloyl chloride dropwise. React at 50-70℃ for 12-24 h under a nitrogen atmosphere. After the reaction is complete, precipitate is formed, the solvent is removed by filtration, the crude product is recrystallized and dried to obtain (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide; 3) Mix (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide, acrylic acid, and polyethylene glycol diacrylate in a third organic solvent until homogeneous. After purging with nitrogen, add an initiator and polymerize at 65-75°C for 4-8 hours to obtain an organic gel.

3. The method for preparing the metal complex hydrogel containing an acylhydrazone hydrophobic monomer according to claim 2, characterized in that, The concentration of the metal ion solution is 0.0125~0.2 M; 1~3 ml of metal ion solution is added per gram of hydrogel.

4. The method for preparing the metal complex hydrogel containing an acylhydrazone hydrophobic monomer according to claim 2, characterized in that, In step 1), the molar ratio of 4-aminobenzoyl hydrazine to 4-phenylbenzaldehyde is 1:(0.8~1.2), and the amount of glacial acetic acid added per millimole of 4-aminobenzoyl hydrazine is 0.1~0.2 ml.

5. The method for preparing the metal complex hydrogel containing an acylhydrazone hydrophobic monomer according to claim 2, characterized in that, In step 2), the molar ratio of (E)-N'-([1,1'-biphenyl]-4-ylmethylene)-4-aminobenzoylhydrazine and acryloyl chloride is 1:2 to 1:4, and the molar ratio of acryloyl chloride to triethylamine is 1:1.2 to 1:1.

6.

6. The method for preparing the metal complex hydrogel containing an acylhydrazone hydrophobic monomer according to claim 2, characterized in that, In step 3), the molar concentration of acrylic acid in the third solvent is 3~6 mM, the molar ratio of (E)-N-(4-(2-([1,1'-biphenyl]-4-ylmethylene)hydrazine-1-carbonyl)phenyl)acrylamide to acrylic acid is 1:20~1:104, the molar concentration of polyethylene glycol diacrylate is 0.5~2% of the molar concentration of acrylic acid, and the amount of initiator is 1~3% of the mass of acrylic acid.

7. The method for preparing the metal complex hydrogel containing an acylhydrazone hydrophobic monomer according to claim 1 or 2, characterized in that, The initiator is azobisisobutyronitrile, potassium persulfate, or ammonium persulfate.

8. The method for preparing the metal complex hydrogel containing an acylhydrazone hydrophobic monomer according to claim 2, characterized in that, In step 1), the first organic solvent is one or more of methanol, ethanol, and acetonitrile; in step 2), the second organic solvent is N-methylpyrrolidone; in step 3), the third organic solvent is one or two of N,N-dimethylformamide and dimethyl sulfoxide.

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