A hydrogel modified with inorganic nanoparticles

Abstract

The present invention relates to an inorganic nanoparticle-modified hydrogel, belonging to the technical field of polymer gels. In the preparation method of the hydrogel of the present invention, a compound shown in Formula 1 is used to modify nanoparticles. Since the modified nanoparticles contain unhydrolyzed silicon-nitrogen bonds, they can form a redox initiation system with an oxidant to initiate the polymerization and crosslinking of polymerization monomers at room temperature to form a hydrogel. A unique elastic "spider web" structure is formed between the nanoparticles and the polymer network. The nanoparticles linked by covalent bonds and the elastic polymer network endow the hydrogel with excellent mechanical strength and toughness. Due to the presence of reversible covalent bonds Si-O-Si in the hydrogel, the hydrogel prepared by the present invention also has the advantages of self-healing and anti-fatigue. And some uncrosslinked Si-OH can endow the hydrogel with excellent adhesiveness through hydrogen bond association.

Description

Technical Field

[0001] The present invention relates to an inorganic nanoparticle-modified hydrogel, belonging to the technical field of polymer gels. Background Art

[0002] Hydrogels are three-dimensional solid networks made by crosslinking hydrophilic polymer chains, containing a large amount of water inside. They are elastic "jelly-like" solids between liquids and solids, capable of absorbing a large amount of water but insoluble in water. According to the different crosslinking bonds of hydrogels, hydrogels can be classified into physical hydrogels and chemical hydrogels. Physical hydrogels are gels obtained by physical crosslinking, and physical bonds are reversible and non-permanent. Chemical hydrogels refer to gels crosslinked by chemical bonds. The crosslinking points of chemical hydrogels are covalent bonds, and their strength and stability are higher than those of physical hydrogels.

[0003] Chemically crosslinked polyacrylamide hydrogels are one of the most widely studied hydrogels at present. Acrylamide monomers are the most commonly used chemical crosslinking monomers. Ordinary polyacrylamide hydrogels use persulfates as free radical initiators. Persulfate initiators need to generate free radicals through thermal cracking under heating conditions and cannot be prepared at room temperature. Moreover, polyacrylamide hydrogels have poor fatigue resistance due to the lack of an effective energy dissipation mechanism and are easily broken under stress, thus limiting their applications. Traditional polymer hydrogels also have defects in temperature tolerance. They will inevitably freeze at temperatures below zero and lose water severely at high temperatures, resulting in the loss of their functions, thus limiting the stability and durability of hydrogels. Currently, common methods to improve the antifreeze property of hydrogels include replacing the water in the hydrogel with solvents such as glycerol and adding a large amount of salt ions to the hydrogel system, and the preparation process is complex.

[0004] In recent years, it has been found that nanoparticles can enhance the mechanical properties of hydrogels. It resists the generation and propagation of cracks through covalent bonds, hydrogen bonds, and hydrophobic and electrostatic interactions to achieve mechanical enhancement of the hydrogel. However, limited by problems such as poor dispersion of nanoparticles at the microscale and weak interactions between nanoparticles and polymer chains, the effect of using nanoparticles to enhance hydrogels is not significant. Researchers have used methods such as ultrasonic nanoparticles, surface-modified nanoparticles, and adding dispersants to uniformly disperse nanoparticles. Although the strength of the hydrogel is increased to a high level, the improvement in toughness is not obvious, and the effect is not ideal. For example, Yang J et al. (Yang J, Zhao J. Preparation and mechanical properties of silica nanoparticles reinforced composite hydrogels[J]. Materials Letters, 2014, 120(APR.1): 36-38.) obtained a nanocomposite hydrogel composed of silica nanoparticles / polyacrylic acid by modifying silica with γ-methacryloxypropyltrimethoxysilane (A-174), with a tensile strength of up to 300 kPa and an elongation at break of 900%. In addition, most nanocomposite hydrogels are composed of irreversible covalent bonds and are prone to fatigue fracture under multiple mechanical load cycles. Therefore, the mechanical properties and durability of nanocomposite hydrogels during long-term use are still not satisfactory. Most of the technical solutions for enhancing the mechanical properties of acrylamide-based hydrogels disclosed in the prior art use a single nanomaterial for reinforcement. For example, Chinese Patent Document CN111468084B discloses an adsorption material of a high-strength carbon nanotube cross-linked hydrogel and its preparation method, Chinese Patent Document CN112430338A discloses a high-strength graphene chemically cross-linked polyacrylamide hydrogel and its preparation method, and Chinese Patent Document CN108164903B discloses a polyaspartic acid semi-interpenetrating nanocomposite hydrogel and its preparation process. Regarding the method of enhancing hydrogels with silica, most of them are surface-treated. For example, Chinese Patent Document CN111499815A discloses a SiO2-GO cross-linked polypropylene-based high-strength hydrogel and its preparation method, and Chinese Patent Document CN111875915A discloses a high-strength SiO2-polyacrylic acid-polyvinyl alcohol interpenetrating network hydrogel and its preparation method. However, when using a single nanoparticle and simple surface treatment of the nanoparticle to reinforce the mechanical properties of the hydrogel, the nanoparticles or the surface-treated nanoparticles are prone to agglomeration, and the preparation process is complex, difficult to implement on a large scale, and cannot significantly improve the mechanical properties of the hydrogel. Summary of the Invention

[0005] The object of the present invention is to provide a hydrogel modified with inorganic nanoparticles, which can solve the problem that the mechanical properties of hydrogels cannot be significantly improved when using nanoparticles to reinforce hydrogels at present.

[0006] To achieve the above object, the technical solution adopted by the hydrogel modified with inorganic nanoparticles of the present invention is as follows:

[0007] A hydrogel modified with inorganic nanoparticles is prepared by a method comprising the following steps:

[0008] (1) Mix a compound shown in Formula 1 and inorganic nanoparticles with hydroxyl groups on the surface in water. The compound shown in Formula 1 undergoes hydrolysis, and the silanol groups in the hydrolysis product and the hydroxyl groups on the surface of the inorganic nanoparticles undergo a condensation reaction.

[0009]

[0010] In Formula 1, R1, R2, R3, R 10 , R 11 and R 12 are each independently selected from C1-C5 alkyl groups; R4 and R5 are each independently selected from C3-C6 alkylene groups; R6, R7, R8 and R9 are each independently selected from methyl, ethyl or propyl groups;

[0011] (2) Mix the system obtained in step (1), an oxidant and a polymerization monomer. The unhydrolyzed silicon-nitrogen bonds in the system obtained in step (1) and the oxidant form a redox initiation system to initiate the polymerization of the polymerization monomer to generate a hydrogel; the oxidant is a persulfate or a water-soluble iron salt.

[0012] The inorganic nanoparticle-modified hydrogel of the present invention modifies inorganic nanoparticles with the compound shown in Formula 1, and then performs a sol-gel reaction on the modified nanoparticles, an oxidant, and a polymerization monomer in water. Since the modified nanoparticles contain unhydrolyzed silicon-nitrogen bonds, they can form a redox initiation system with the oxidant, initiating the polymerization and crosslinking of the polymerization monomer at room temperature to form a hydrogel. And the compound shown in Formula 1 can be chemically bonded to the monomer while initiating the polymerization of the monomer, and thus chemically bonded to the polymer network formed by polymerization. A unique elastic "spider web" structure is formed between the nanoparticles and the polymer network, and the nanoparticles and the elastic polymer network linked by covalent bonds endow the hydrogel with excellent mechanical strength and toughness. Due to the presence of reversible covalent bonds Si-O-Si in the hydrogel, the hydrogel prepared by the present invention also has advantages such as self-healing and anti-fatigue. And some uncrosslinked Si-OH can endow the hydrogel with excellent adhesiveness through hydrogen bond association. The inorganic nanoparticle-modified hydrogel of the present invention is prepared by a "one-pot method", which can simplify the preparation steps and is conducive to large-scale implementation. The inorganic nanoparticle-modified hydrogel of the present invention has excellent mechanical strength and toughness, and also has advantages such as self-healing and anti-fatigue, and at the same time has excellent adhesiveness to most substrates.

[0013] Preferably, the inorganic nanoparticles are selected from one or any combination of nano-silica, nano-montmorillonite, and nano-graphene.

[0014] Preferably, in Formula 1, R1, R2, R3, R 10 、R 11 and R 12 are all methyl or ethyl; R4 and R5 are both propylene; R6, R7, R8, and R9 are all methyl. The principle of the preparation method of the hydrogel of the present invention is as Figure 1 shown.

[0015] Preferably, the compound shown in Formula 1 is prepared by an addition reaction of the amino group in the compound shown in Formula 3 and the silicon-hydrogen group in the compound shown in Formula 4;

[0016]

[0017] In Formula 3, R 13 、R 14 and R 15 each independently selected from C1-C5 alkyl; R 16 is C3-C6 alkylene;

[0018] In Formula 4, R 17 、R 18 、R 19 and R 20 each independently selected from methyl, ethyl, or propyl.

[0019] Preferably, in step (1), the mass ratio of the compound shown in formula 1, inorganic nanoparticles and water is (0.5 - 10):(0.5 - 5):100. If the amount of inorganic nanoparticles is too small, the enhancement effect is not obvious; if the amount is too large, agglomeration will occur, resulting in a decrease in the enhancement effect.

[0020] Preferably, in step (1), the mixing time is 5 - 15 min. For example, in step (1), the mixing time is 7 min.

[0021] Preferably, in step (1), the mixing method includes the following steps: under stirring conditions, the compound shown in formula 1 is dropped into the aqueous dispersion of inorganic nanoparticles, then stirring is continued for 5 - 10 min, and then ultrasonic treatment is carried out for 2 - 5 min. For example, in step (1), the mixing method includes the following steps: under stirring conditions, the compound shown in formula 1 is dropped into the aqueous dispersion of inorganic nanoparticles, then stirring is continued for 5 min, and then ultrasonic treatment is carried out for 2 min.

[0022] Preferably, the rotation speed of the stirring is 800 - 1000 r / min; the power of the ultrasonic treatment is 600 - 800 W. For example, the rotation speed of the stirring is 800 r / min; the power of the ultrasonic treatment is 600 W.

[0023] Preferably, after mixing, standing is carried out to obtain the water gel modified with inorganic nanoparticles.

[0024] Preferably, the polymerization monomer is selected from one or any combination of acrylamide, acrylic acid, N - isopropylacrylamide, and N,N - dimethylacrylamide. When the polymerization monomer is acrylamide and the nanoparticles are nano - silica, by adjusting the formula, the tensile strength of the prepared water gel can reach 0.4 MPa, and the elongation at break exceeds 3200%. This elongation at break is much higher than that of the nanoparticle - reinforced water gel systems reported in the current literature.

[0025] Preferably, the mass ratio of water and the polymerization monomer is 100:(25 - 35). For example, the mass ratio of water and the polymerization monomer is 100:25. If the amount of the polymerization monomer is too small, the strength of the water gel will decrease.

[0026] Preferably, the persulfate is selected from one or any combination of ammonium persulfate, potassium persulfate, and sodium persulfate. For example, the persulfate is ammonium persulfate.

[0027] Preferably, the mass ratio of water and the oxidant is 100:(0.075 - 0.1). For example, the mass ratio of water and the oxidant is 100:0.075. If the amount of the oxidant is too small, the initiation rate will be slow; if the amount is too large, the toughness of the water gel will decrease.

[0028] Use of the inorganic nanoparticle-modified hydrogel as described above as a self-healing material.

[0029] When the inorganic nanoparticle-modified hydrogel of the present invention is used as a self-healing material, due to the presence of reversible covalent bonds Si-O-Si in the hydrogel, it has excellent mechanical strength and toughness while also having good self-repair performance. Brief Description of the Drawings

[0030] Figure 1 Schematic diagram of the principle of the preparation method of the hydrogel of the present invention;

[0031] Figure 2 SEM image of the inorganic nanoparticle-modified hydrogel of Example 1 in Experimental Example 1;

[0032] Figure 3 Schematic diagram of the biaxial tension test of the inorganic nanoparticle-modified hydrogel of Example 1 in Experimental Example 2;

[0033] Figure 4 Schematic diagram of the ductility test of the inorganic nanoparticle-modified hydrogel of Example 1 in Experimental Example 2; wherein, Figure 4 a is a photo of the hydrogel before inflation, Figure 4 b is a photo of the hydrogel after inflation;

[0034] Figure 5 Schematic diagram of the tensile stress-strain curves of the hydrogels of the comparative example and Examples 1-5 in Experimental Example 2;

[0035] Figure 6 Schematic diagram of the change curve of the tensile stress of the hydrogels of the comparative example and Examples 8-13 in Experimental Example 2 with the multiple λ of the increase in the hydrogel length;

[0036] Figure 7 Schematic diagram of the results of the notch cyclic tensile test in Experimental Example 3; wherein, Figure 7 a is a comparison photo of the inorganic nanoparticle-modified hydrogel of Example 4 before and after 5000 cyclic tensile tests with a strain of 500%, Figure 7 b is a schematic diagram of the change in the length growth of cracks during 5000 cyclic tensile tests with a strain of 500% for the hydrogels of Example 4 and the comparative example;

[0037] Figure 8 Schematic diagram of the test results of the self-healing performance of the inorganic nanoparticle-modified hydrogel of Example 1 in Experimental Example 4 and the tensile performance of the hydrogel after self-healing;

[0038] Figure 9Schematic diagram of the step strain rate scanning test results of the inorganic nanoparticle-modified hydrogel in Example 1 of Experimental Example 4; Figure 9 In it, the stepped line is the strain curve;

[0039] Figure 10 Schematic diagram of the results of the tensile test of the inorganic nanoparticle-modified hydrogel in Example 1 of Experimental Example 5 at -20°C; among them, Figure 10 a is the appearance diagram of the hydrogel before the tensile test after being placed at -20°C for 6 hours, Figure 10 b is the appearance diagram of the hydrogel after the tensile test after being placed at -20°C for 6 hours;

[0040] Figure 11 Schematic diagram of the test results of the bonding behavior of the inorganic nanoparticle-modified hydrogel in Example 1 of Experimental Example 6 to different substrates (glass, aluminum, polytetrafluoroethylene, rubber, plastic, and copper). Specific implementation manners

[0041] The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

[0042] The organosilicon compounds used in the preparation of the hydrogels of Examples 1-13 and Comparative Examples of the present invention are as shown in Formula 5;

[0043]

[0044] The preparation method of the organosilicon compound is as follows: Put 1,1,3,3-tetramethyldisiloxane and 3-aminopropyltrimethoxysilane with a molar ratio of 1:2 into a round-bottom flask, and then add Karstedt platinum catalyst (the mass of the platinum catalyst is 3‰ of the mass of 1,1,3,3-tetramethyldisiloxane and 3-aminopropyltrimethoxysilane), and then stir at room temperature for 3 hours. When it is observed that no bubbles are generated, it means that the reaction of 1,1,3,3-tetramethyldisiloxane and 3-aminopropyltrimethoxysilane is complete, and the organosilicon compound is obtained. The synthesis route for preparing the organosilicon compound is as follows:

[0045]

[0046] Example 1

[0047] The inorganic nanoparticle-modified hydrogel of this example is prepared by a method comprising the following steps:

[0048] 0.1 g of nano-silica was added to 20 mL of deionized water and stirred evenly to obtain an aqueous dispersion of nano-silica. Then, 1 g of organosilicon compound was dropped into the aqueous dispersion of nano-silica under stirring conditions. After the dropping was completed, stirring was continued at a speed of 800 r / min for 5 min, and then ultrasonic treatment (ultrasonic power was 600 W) was carried out for 2 min to obtain a mixture. Then, 5 g of acrylamide and 0.015 g of ammonium persulfate were added to the mixture and stirred evenly to obtain a prepolymer solution. Then, the prepolymer solution was poured into a mold and left standing at room temperature to obtain a hydrogel modified with inorganic nanoparticles, labeled as SNPs(0.5).

[0049] Example 2

[0050] The difference between the hydrogel modified with inorganic nanoparticles in this example and the hydrogel modified with inorganic nanoparticles in Example 1 is only that the mass of nano-silica used in the preparation of the hydrogel modified with inorganic nanoparticles in this example is 0.2 g, and the hydrogel modified with inorganic nanoparticles in this example is labeled as SNPs(1).

[0051] Example 3

[0052] The difference between the hydrogel modified with inorganic nanoparticles in this example and the hydrogel modified with inorganic nanoparticles in Example 1 is only that the mass of nano-silica used in the preparation of the hydrogel modified with inorganic nanoparticles in this example is 0.3 g, and the hydrogel modified with inorganic nanoparticles in this example is labeled as SNPs(1.5).

[0053] Example 4

[0054] The difference between the hydrogel modified with inorganic nanoparticles in this example and the hydrogel modified with inorganic nanoparticles in Example 1 is only that the mass of nano-silica used in the preparation of the hydrogel modified with inorganic nanoparticles in this example is 0.4 g, and the hydrogel modified with inorganic nanoparticles in this example is labeled as SNPs(2).

[0055] Example 5

[0056] The difference between the hydrogel modified with inorganic nanoparticles in this example and the hydrogel modified with inorganic nanoparticles in Example 1 is only that the mass of nano-silica used in the preparation of the hydrogel modified with inorganic nanoparticles in this example is 0.5 g, and the hydrogel modified with inorganic nanoparticles prepared in this example is labeled as SNPs(2.5).

[0057] Example 6

[0058] The hydrogel modified with inorganic nanoparticles in this example was prepared by a method comprising the following steps:

[0059] 1 g of nano-silica was added to 20 mL of deionized water and stirred evenly to obtain an aqueous dispersion of nano-silica. Then, 2 g of organosilicon compound was dropped into the aqueous dispersion of nano-silica under stirring conditions. After the dropping was completed, stirring was continued at a speed of 900 r / min for 8 min, and then ultrasonic treatment (ultrasonic power: 700 W) was carried out for 3 min to obtain a mixture. Then, 6 g of acrylamide and 0.018 g of ammonium persulfate were added to the mixture and stirred evenly to obtain a prepolymer solution. Then, the prepolymer solution was poured into a mold and allowed to stand at room temperature to obtain a hydrogel modified with inorganic nanoparticles.

[0060] Example 7

[0061] The hydrogel modified with inorganic nanoparticles in this example was prepared by a method including the following steps:

[0062] 0.1 g of nano-silica was added to 20 mL of deionized water and stirred evenly to obtain an aqueous dispersion of nano-silica. Then, 0.1 g of organosilicon compound was dropped into the aqueous dispersion of nano-silica under stirring conditions. After the dropping was completed, stirring was continued at a speed of 1000 r / min for 10 min, and then ultrasonic treatment (ultrasonic power: 800 W) was carried out for 5 min to obtain a mixture. Then, 7 g of acrylamide and 0.02 g of ammonium persulfate were added to the mixture and stirred evenly to obtain a prepolymer solution. Then, the prepolymer solution was poured into a mold and allowed to stand at room temperature to obtain a hydrogel modified with inorganic nanoparticles.

[0063] Example 8

[0064] The hydrogel modified with inorganic nanoparticles in this example was prepared by a method including the following steps:

[0065] 0.1 g of nano-montmorillonite was added to 20 mL of deionized water and stirred evenly to obtain an aqueous dispersion of nano-montmorillonite. Then, 1 g of organosilicon compound was dropped into the aqueous dispersion of nano-montmorillonite under stirring conditions. After the dropping was completed, stirring was continued at a speed of 800 r / min for 5 min, and then ultrasonic treatment (ultrasonic power: 600 W) was carried out for 2 min to obtain a mixture. Then, 5 g of acrylamide and 0.015 g of ammonium persulfate were added to the mixture and stirred evenly to obtain a prepolymer solution. Then, the prepolymer solution was poured into a mold and allowed to stand at room temperature to obtain a hydrogel modified with inorganic nanoparticles, labeled as MMT(0.5).

[0066] Example 9

[0067] The difference between the inorganic nanoparticle-modified hydrogel of this example and the inorganic nanoparticle-modified hydrogel of Example 8 is only that the mass of the nano-montmorillonite used in the preparation of the inorganic nanoparticle-modified hydrogel of this example is 0.2 g, and the inorganic nanoparticle-modified hydrogel prepared in this example is labeled as MMT(1).

[0068] Example 10

[0069] The difference between the inorganic nanoparticle-modified hydrogel of this example and the inorganic nanoparticle-modified hydrogel of Example 8 is only that the mass of the nano-montmorillonite used in the preparation of the inorganic nanoparticle-modified hydrogel of this example is 0.3 g, and the inorganic nanoparticle-modified hydrogel prepared in this example is labeled as MMT(1.5).

[0070] Example 11

[0071] The difference between the inorganic nanoparticle-modified hydrogel of this example and the inorganic nanoparticle-modified hydrogel of Example 8 is only that the mass of the nano-montmorillonite used in the preparation of the inorganic nanoparticle-modified hydrogel of this example is 0.4 g, and the inorganic nanoparticle-modified hydrogel prepared in this example is labeled as MMT(2).

[0072] Example 12

[0073] The difference between the inorganic nanoparticle-modified hydrogel of this example and the inorganic nanoparticle-modified hydrogel of Example 8 is only that the mass of the nano-montmorillonite used in the preparation of the inorganic nanoparticle-modified hydrogel of this example is 0.5 g, and the inorganic nanoparticle-modified hydrogel prepared in this example is labeled as MMT(2.5).

[0074] Example 13

[0075] The difference between the inorganic nanoparticle-modified hydrogel of this example and the inorganic nanoparticle-modified hydrogel of Example 8 is only that the mass of the nano-montmorillonite used in the preparation of the inorganic nanoparticle-modified hydrogel of this example is 0.6 g, and the inorganic nanoparticle-modified hydrogel prepared in this example is labeled as MMT(3).

[0076] Comparative Example

[0077] The difference between the hydrogel of this comparative example and the inorganic nanoparticle-modified hydrogel of Example 1 is only that the mass of the nano-silica used in the preparation of the hydrogel of this comparative example is 0 g, and the hydrogel of this comparative example is labeled as SNPs(0) or MMT(0).

[0078] Experimental Example 1

[0079] The morphology of the inorganic nanoparticle-modified hydrogel of Example 1 was characterized by scanning electron microscopy (SEM), and the results are as Figure 2 shown. The results show that the dry gel has a three-dimensional network structure, and the honeycomb-like pore distribution on the surface is relatively regular. The silica is evenly distributed in the network. Moreover, it can be seen that there is a "spider web"-like elastic network - polysiloxane in the pores of the polyacrylamide network, and the polysiloxane and polyacrylamide are tightly connected together, verifying the gradient porous structure of the hydrogel. The morphologies of the inorganic nanoparticle-modified hydrogels of Examples 2-7 are similar to those of the inorganic nanoparticle-modified hydrogel of Example 1.

[0080] Experimental Example 2

[0081] To evaluate the ductility of the inorganic nanoparticle-modified hydrogel of Example 1, the biaxial tension of the inorganic nanoparticle-modified hydrogel of Example 1 was tested. The size of the hydrogel film with a thickness of 2 mm was changed from 2.0×2.0 cm 2 to 3.0×3.0 cm 2 , then from 3.0×3.0 cm 2 to 5.0×5.0 cm 2 , and finally further stretched to 7.0×7.0 cm 2 , as Figure 3 shown. No breakage occurred during the stretching process of the hydrogel film, indicating that the area deformation rate (the area deformation rate is equal to the percentage of the deformed area to the area before deformation) of the inorganic nanoparticle-modified hydrogel of Example 1 is greater than 1200%.

[0082] Meanwhile, to further evaluate the ductility of the inorganic nanoparticle-modified hydrogel of Example 1, the periphery of the inorganic nanoparticle-modified hydrogel film (with a thickness of 2 mm) of Example 1 was sealed, and then nitrogen gas was introduced. The hydrogel film swelled into a spherical shape under the nitrogen pressure. As Figure 4 shown, the hydrogel film with an area of 1 cm 2 can swell into a spherical shape with a volume of 615 cm 3 , indicating that the inorganic nanoparticle-modified hydrogel film of Example 1 has good ductility.

[0083] When the biaxial tension and ductility of the inorganic nanoparticle-modified hydrogels of Examples 2-7 were tested according to the above method, the test results were similar to those of the inorganic nanoparticle-modified hydrogel of Example 1, indicating that the inorganic nanoparticle-modified hydrogels prepared in Examples 2-7 all have excellent ductility.

[0084] Finally, to evaluate the effect of the amount of nano-silica on the mechanical properties of the hydrogel, the tensile stress-strain curves of the hydrogels of the comparative examples and the inorganic nanoparticle-modified hydrogels of Examples 1-5 were tested respectively according to the method specified in ISO 37:2011 "Rubber, vulcanized or thermoplastic - Determination of tensile stress-strain properties", and the results are as Figure 5 shown. The results show that with the increase of the amount of nano-silica, the tensile strength and elongation at break of the hydrogel first increase and then decrease. The maximum strain of the hydrogel is 3100%, and the strength is 400 kPa. The test results of the tensile stress-strain curves of the inorganic nanoparticle-modified hydrogels of Examples 6-7 are close to those of the inorganic nanoparticle-modified hydrogels of Examples 1-5.

[0085] To evaluate the effect of the amount of nano-montmorillonite on the mechanical properties of the hydrogel, since the length of the hydrogel will increase under the tensile action, the change curves of the tensile stress of the hydrogels of the comparative examples and the inorganic nanoparticle-modified hydrogels of Examples 8-13 with the multiple λ of the hydrogel length increase were tested respectively according to the method specified in ISO 37:2011 "Rubber, vulcanized or thermoplastic - Determination of tensile stress-strain properties", and the results are as Figure 6 shown. The results show that with the increase of the amount of nano-montmorillonite, the tensile strength of the hydrogel and the multiple λ of the hydrogel length increase also show a trend of first increasing and then decreasing.

[0086] Experimental Example 3

[0087] To evaluate the fatigue resistance of the inorganic nanoparticle-modified hydrogel of Example 4, the propagation behavior of prefabricated cracks in the hydrogels of Example 4 and the comparative example was tested by the method of notched cyclic tension in 5000 cycles with a strain of 500%. The experimental method is as follows: A notch was cut in the middle of the hydrogel (the extension direction of the notch is perpendicular to the tensile direction), and the length of the notch was recorded as L0, and then cyclic tension was carried out under the condition of a strain of 500%, and the length L of the notch of the hydrogel after tension was observed and recorded. The part of the notch length greater than L0 is the crack, and the crack length is L - L0. The experimental results are as Figure 7 shown, Figure 7 a is a comparison photo of the inorganic nanoparticle-modified hydrogel of Example 4 before tension and after 5000 cycles of cyclic tension with a strain of 500% (the black part in the figure is the notch), and it can be seen that the crack hardly grows. Figure 7Figure b shows the schematic diagram of the change in the crack length growth of the hydrogels of Example 4 and the comparative example during 5000 cycles of cyclic stretching with a strain of 500%. It can be seen that the crack length of the hydrogel of Example 4 hardly changed, while the hydrogel of the comparative example fractured after about 200 cycles of cyclic stretching. This indicates that the hydrogel of Example 4 has excellent fatigue resistance.

[0088] When the above method was used to test the fatigue resistance of the inorganic nanoparticle-modified hydrogels of Examples 1-3 and Examples 5-7, the test results were close to those of the inorganic nanoparticle-modified hydrogel of Example 4, indicating that the inorganic nanoparticle-modified hydrogels prepared in Examples 1-3 and Examples 5-7 all have good fatigue resistance.

[0089] Experimental Example 4

[0090] To evaluate the self-healing performance of the inorganic nanoparticle-modified hydrogel of Example 1, the self-healing performance of the inorganic nanoparticle-modified hydrogel of Example 1 and the tensile performance of the hydrogel after self-healing were tested by a cutting-healing-stretching experiment. The experimental method is as follows: The inorganic nanoparticle-modified hydrogel (cylindrical) of Example 1 was cut into three sections, and then the cut sections of the hydrogel were brought into contact at the cutting site and squeezed forcefully to make the cutting site of the hydrogel fully fit. Then, the squeezing force was released, and the self-healing situation of the hydrogel was observed. Then, the tensile performance of the self-healed hydrogel was tested. The experimental results are as Figure 8 shown. The results show that the fractured hydrogel self-healed into a whole after being placed for 10 minutes. The length of the self-healed hydrogel was 7 cm and it could be stretched to 17 cm, indicating that the hydrogel has very excellent self-repairability.

[0091] When the above method was used to test the self-healing performance of the inorganic nanoparticle-modified hydrogels of Examples 2-7, the test results were consistent with those of the inorganic nanoparticle-modified hydrogel of Example 1.

[0092] Then, the self-recovery ability of the inorganic nanoparticle-modified hydrogel of Example 1 was tested by a step strain sweep test using a HAAKE MARS III rotational rheometer. The results are as Figure 9 shown. The results show that the hydrogel exhibits a fast and reversible repair process under alternating conditions of large strain (700%) and small strain (0.1%), indicating its ability to reconstruct the network after deformation.

[0093] Experimental Example 5

[0094] To evaluate the tensile performance of the inorganic nanoparticle-modified hydrogel of Example 1 at low temperature, the inorganic nanoparticle-modified hydrogel of Example 1 was placed at -20 °C for 6 h and then subjected to a tensile test. The results are asFigure 10 As shown. The results show that the length of the hydrogel can be stretched from 2 cm to 36 cm after being placed at -20 °C for 6 h, and the elongation rate is greater than 1800%. This indicates that the hydrogel modified with inorganic nanoparticles in Example 1 has good low-temperature resistance.

[0095] When the above method was used to test the tensile properties of the hydrogels modified with inorganic nanoparticles in Examples 2-7 at low temperature, the test results were similar to those of the hydrogels modified with inorganic nanoparticles in Example 1 at low temperature.

[0096] Experimental Example 6

[0097] To evaluate the bonding performance of the hydrogel modified with inorganic nanoparticles in Example 1, the bonding behavior of the hydrogel modified with inorganic nanoparticles in Example 1 to different substrates (glass, aluminum, polytetrafluoroethylene, rubber, plastic, and copper) was tested by the lap shear test. The method of the lap shear test was carried out according to the regulations in the standard GBT 33334-2016 "Test Method for Tensile Shear Strength of Adhesives in Single Lap Joints". During the operation, a hydrogel film with a size of 8 mm in length, 8 mm in width, and 2 mm in height was used to bond the upper and lower substrates to form a single lap joint. After the bonding was completed, a weight of 1 kg was placed at the joint position for 15 min to apply pressure to the hydrogel to ensure that the hydrogel and the substrate were bonded tightly. Then, a universal tensile machine was used to apply opposite forces to the upper and lower substrates along the extension direction of the substrate at a tensile speed of 100 mm / min to break the joint. During the stretching process, due to a certain bonding force between the hydrogel and the substrate and the large strain of the hydrogel, during the stretching process, when the hydrogel undergoes a large deformation, the substrate and the hydrogel are debonded and the joint is broken. During the experiment, the tensile shear force F and the deformation of the hydrogel were recorded, and the tensile shear strength Q was calculated. Q = F / S, where S is the bonding area, and the results are as Figure 11 shown. The results show that the hydrogel modified with inorganic nanoparticles in Example 1 shows good adhesion on the surfaces of different substrates.

[0098] When the above method was used to test the bonding performance of the hydrogels modified with inorganic nanoparticles in Examples 2-7, the test results were similar to those of the hydrogels modified with inorganic nanoparticles in Example 1.

Claims

1. An inorganic nanoparticle-modified hydrogel, characterized in that, Prepared by a method comprising the following steps: (1) Mix the compound shown in Formula 1 and inorganic nanoparticles with hydroxyl groups on the surface in water. The compound shown in Formula 1 undergoes hydrolysis, and the silanol groups in the hydrolysis product condense with the hydroxyl groups on the surface of the inorganic nanoparticles; In Formula 1, R1, R2, R3, R 10 , R 11 and R 12 are each independently selected from C1-C5 alkyl; R4 and R5 are each independently selected from C3-C6 alkylene; R6, R7, R8 and R9 are each independently selected from methyl, ethyl or propyl; (2) Mix the system obtained in step (1), an oxidant, and a polymerization monomer. The unhydrolyzed silicon-nitrogen bonds in the system obtained in step (1) and the oxidant form a redox initiation system to initiate the polymerization of the polymerization monomer to generate a hydrogel; the oxidant is a persulfate or a water-soluble iron salt; In step (1), the mass ratio of the compound shown in Formula 1, the inorganic nanoparticles, and water is (0.5-10):(0.5-5):100; the polymerization monomer is selected from one or any combination of acrylamide, acrylic acid, N-isopropylacrylamide, and N,N-dimethylacrylamide; the mass ratio of water to the polymerization monomer is 100:(25-35).

2. The inorganic nanoparticle-modified hydrogel according to claim 1, characterized in that, The inorganic nanoparticles are selected from one or any combination of nano-silica, nano-montmorillonite, and nano-graphene.

3. The inorganic nanoparticle-modified hydrogel according to claim 1, characterized in that, In Formula 1, R1, R2, R3, R 10 , R 11 and R 12 are each methyl or ethyl; R4 and R5 are each propylene; R6, R7, R8 and R9 are each methyl.

4. The inorganic nanoparticle-modified hydrogel according to any one of claims 1-3, characterized in that, In step (1), the mixing method comprises the following steps: Under stirring conditions, drop the compound shown in Formula 1 into the aqueous dispersion of the inorganic nanoparticles, then continue stirring for 5-10 min, and then perform ultrasonic treatment for 2-5 min; the stirring speed is 800-1000 r / min; the ultrasonic power is 600-800 W.

5. The inorganic nanoparticle-modified hydrogel according to any one of claims 1-3, characterized in that, After mixing, let it stand to obtain the hydrogel modified with the inorganic nanoparticles.

6. The inorganic nanoparticle-modified hydrogel according to any one of claims 1-3, characterized in that, The persulfate is selected from one or any combination of ammonium persulfate, potassium persulfate, and sodium persulfate.

7. The inorganic nanoparticle-modified hydrogel according to claim 6, characterized in that, The mass ratio of water to the oxidant is 100:(0.075-0.1).

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