Preparation method of high-toughness physical hydrogel

Abstract

The invention discloses a preparation method of high-toughness physical hydrogel, and belongs to the technical field of hydrogel preparation. The preparation method comprises the following steps: preparing polyvinyl alcohol into a polymer solution, mixing tannic acid and iron ions to prepare a complex solution, blending the two solutions to prepare a flocculation hydrogel of a tannic acid-iron ion complex and polyvinyl alcohol, centrifugally collecting the flocculation hydrogel, pressing the flocculation hydrogel into a sheet material, and drying the sheet material to obtain the tannic acid-iron ion / polyvinyl alcohol composite material. The hydrogel is soaked in a poor solvent for dehydration for mechanical property regulation and control, and then the hydrogel and deionized water are subjected to solvent exchange to obtain the high-strength and high-toughness physical hydrogel. The novel hydrogel material with high strength and high toughness is prepared from cheap and easily available commercial raw materials through a simple blending and efficient mechanical property reinforcing and toughening strategy, and the prepared material realizes unification of strength and toughness, and has important application prospects in multiple fields such as biomimetic materials, flexible electronics and energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogels, and particularly relates to a preparation method of a high-strength and tough physical hydrogel. Background Art

[0002] Strength and toughness are two basic indicators of the mechanical properties of materials. However, there is often a serious conflict between the two, and it is difficult to achieve the unity of high strength and high toughness of materials. A hydrogel is a hydrophilic cross-linked network polymer with a high water content. Due to the lack of an energy dissipation mechanism and an inhomogeneous network structure in traditional synthetic hydrogels, their mechanical strength is low, and the tearing toughness is even worse. The poor mechanical properties greatly limit their application in a wider range of fields. In current technical research, the preparation of high-strength and tough hydrogels is very difficult. The main reason is that traditional hydrogel strengthening technologies can only improve the mechanical strength of materials, but have limited effect on improving the tearing toughness of materials. Developing efficient synthesis of hydrogel materials with both high strength and high toughness can greatly expand the application of hydrogels in more fields, especially in fields with high requirements for load-bearing, such as flexible electronics, bionic actuators, artificial joint cartilage, etc.

[0003] The preparation technology of high-strength hydrogels has made great progress in the past two decades. By designing a uniform network and introducing an efficient energy dissipation mechanism and other means, the mechanical strength of materials can be significantly improved. For example, strategies such as double network (Nature Communications, 2024, 15(1): 1344), nanocomposite (Composites Science and Technology, 2022, 217: 109119), mechanical training (Proceedings of the National Academy of Sciences, 2019, 116(21): 10244 - 10249), and sliding ring (Science, 2021, 372(6546): 1078 - 1081) are used to enhance and toughen hydrogels. However, the common technical problems are the difficulties in preparation, long time consumption, high cost, and incompatibility between strength and toughness in preparation and performance. It is very difficult to achieve low-cost large-scale efficient preparation and industrial application of high-strength hydrogels by many technical routes. Therefore, it is a huge challenge in technology to rapidly and efficiently construct high-strength and tough hydrogels using cheap and easily available commercial raw materials and simple and feasible strengthening and toughening strategies. Summary of the Invention

[0004] 1. Technical Problems to be Solved by the Invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a method for preparing a high-strength and tough physical hydrogel. The present invention utilizes commercially available raw materials that are inexpensive and easily obtainable, and through simple blending and an efficient mechanical property enhancement and toughening strategy, a hydrogel material with both high strength and high toughness is prepared, which will have important application prospects in many fields such as biomimetic materials, flexible electronics, and energy.

[0006] 2. Technical Solution

[0007] To achieve the above object, the technical solution provided by the present invention is as follows:

[0008] A method for preparing a high-strength and tough physical hydrogel of the present invention includes the following steps:

[0009] Prepare a polyvinyl alcohol solution by mixing polyvinyl alcohol and water;

[0010] Dissolve ferric chloride hexahydrate in deionized water to obtain an iron ion solution;

[0011] Add tannic acid to the iron ion solution to form a complex solution;

[0012] Slowly pour the polyvinyl alcohol solution into the complex solution and stir to form a gel, and centrifuge to obtain a polymer;

[0013] Soak the polymer in a poor solvent to dehydrate and obtain an organogel;

[0014] Transfer the organogel to an aqueous deionized water solution for solvent exchange to obtain a high-strength and tough physical hydrogel.

[0015] As a preferred embodiment of the preparation method of the present invention, wherein: the concentration of the polyvinyl alcohol solution is 2 wt% to 8 wt%.

[0016] As a preferred embodiment of the preparation method of the present invention, wherein: the molecular weight of the polyvinyl alcohol is one or more of 47,ooo, 61,ooo, 74,800, 145,ooo, and 195,ooo.

[0017] As a preferred embodiment of the preparation method of the present invention, wherein: the molar ratio of the iron ion to tannic acid is (3 - 9):1.

[0018] As a preferred embodiment of the preparation method of the present invention, wherein: the poor solvent is one or more combinations of ethanol, ethylene glycol, glycerol, and acetone.

[0019] As a preferred embodiment of the preparation method of the present invention, wherein: the centrifugation rate during the process of centrifuging to obtain the polymer is 4000 - 8000 r / min.

[0020] As a preferred embodiment of the preparation method of the present invention, the soaking time in the poor solvent is 12 to 36 hours.

[0021] As a preferred embodiment of the preparation method of the present invention, the time for solvent exchange in water is 24 to 48 hours.

[0022] 3. Beneficial effects

[0023] Adopting the technical solution provided by the present invention, compared with the existing well-known technologies, it has the following remarkable effects:

[0024] (1) All raw materials required by the present invention are industrially produced, inexpensive and easily available. Moreover, the present invention does not require any special production equipment, and large-scale preparation can be achieved. It has the advantage of scalable low-cost production while achieving high performance. The synthesis process does not involve polymer polymerization and there is no risk of monomer residue, making it more environmentally friendly.

[0025] (2) The preparation method of the high-strength and tough hydrogel of the present invention is significantly different from the traditional methods for enhancing and toughening PVA, such as cyclic freezing-thawing method, quenching, and salting out. The method of the present invention only involves blending and flocculating to form a gel and dehydrating in a poor solvent for enhancing and toughening, and finally performing solvent exchange in water to obtain the target material. The whole process is more controllable and the preparation efficiency is higher.

[0026] (3) The biphasic hydrogel prepared by the present invention has the characteristics of high elasticity, high strength, high toughness and high fatigue threshold. Its tensile strength reaches 6.5 MPa, the tensile length exceeds 800%, and the tear toughness exceeds 10,000 J / m 2 , and this high-strength and tough hydrogel combines high strength and high toughness, has excellent and stable mechanical properties, and all performance indicators reach a very high level.

[0027] (4) There is no chemical cross-linking in the preparation process of the high-strength and tough hydrogel synthesized by the present invention. Therefore, the synthesized target hydrogel is a high-strength and tough physical hydrogel, and the finally presented sample is in a swelling equilibrium state with stable mechanical properties. Description of the drawings

[0028] Figure 1 It is a demonstration diagram of lifting a heavy object at the incision after pre-incising the high-strength and tough physical hydrogel material prepared in Example 4 of the present invention.

[0029] Figure 2 It is a stress-strain curve diagram of the high-strength and tough physical hydrogel material prepared in Example 4 of the present invention.

[0030] Figure 3 It is a curve diagram of the trouser tear force - tensile displacement distance of the high-strength and tough physical hydrogel material prepared in Example 4 of the present invention under the condition of a thickness of 2 mm. Detailed implementation mode

[0031] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the specific implementation mode of the present invention in detail in conjunction with the embodiments of the specification.

[0032] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0033] Secondly, the so-called "one embodiment" or "embodiment" herein refers to specific features, structures or characteristics that can be included in at least one implementation mode of the present invention. The "in one embodiment" that appears in different places in this specification does not all refer to the same embodiment, nor is it an independent or selectively exclusive embodiment from other embodiments.

[0034] Unless otherwise stated, the raw materials used in the embodiments of the present invention are all commercially available.

[0035] Example 1

[0036] This example provides a preparation method of a high-strength and tough physical hydrogel, and the specific steps are as follows:

[0037] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 47,000 and dissolve it in 96 g of deionized water, and dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0038] (2) Weigh 3.8 g of ferric chloride hexahydrate and dissolve it in 26.2 g of deionized water. Then, weigh 3.4 g of tannic acid and add it to the iron ion solution and stir evenly to obtain a complex solution with a molar ratio of iron ions to tannic acid of 7:1.

[0039] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2), stir and flocculate to form a gel, and centrifuge to obtain a polymer.

[0040] (4) After pressing the polymer into a sheet, soak it in an ethanol solution for 24 hours for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 hours for solvent exchange to obtain the final product.

[0041] Example 2

[0042] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 145,000 and dissolve it in 96 g of deionized water, and dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0043] (2) After weighing 3.8 g of ferric chloride hexahydrate and dissolving it in 26.2 g of deionized water, weigh 3.4 g of tannic acid and add it to the ferric ion solution, and stir evenly to obtain a complex solution with a molar ratio of ferric ion to tannic acid of 7:1.

[0044] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2), stir and flocculate to form a gel, and centrifuge to obtain a polymer.

[0045] (4) After pressing the polymer into a tablet, soak it in an ethanol solution for 24 hours for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 hours for solvent exchange to obtain the final product.

[0046] Example 3

[0047] (1) Weigh 2 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 98 g of deionized water, and dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0048] (2) After weighing 3.8 g of ferric chloride hexahydrate and dissolving it in 26.2 g of deionized water, weigh 3.4 g of tannic acid and add it to the ferric ion solution, and stir evenly to obtain a complex solution with a molar ratio of ferric ion to tannic acid of 7:1.

[0049] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2), stir and flocculate to form a gel, and centrifuge to obtain a polymer.

[0050] (4) After pressing the polymer into a tablet, soak it in an ethanol solution for 24 hours for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 hours for solvent exchange to obtain the final product.

[0051] Example 4

[0052] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 96 g of deionized water, and dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0053] (2) After weighing 3.8 g of ferric chloride hexahydrate and dissolving it in 26.2 g of deionized water, weigh 3.4 g of tannic acid and add it to the ferric ion solution, and stir evenly to obtain a complex solution with a molar ratio of ferric ion to tannic acid of 7:1.

[0054] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2), stir and flocculate to form a gel, and centrifuge to obtain a polymer.

[0055] (4) After pressing the polymer into a tablet, soak it in an ethanol solution for 24 hours for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 hours for solvent exchange to obtain the final product.

[0056] Example 5

[0057] (1) Weigh 8 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 92 g of deionized water. Dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0058] (2) After weighing 3.8 g of ferric chloride hexahydrate and dissolving it in 26.2 g of deionized water, weigh 3.4 g of tannic acid and add it to the iron ion solution and stir evenly to obtain a complex solution with a molar ratio of iron ions to tannic acid of 7:1.

[0059] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2) and stir to form a gel by flocculation, and centrifuge to obtain a polymer.

[0060] (4) After pressing the polymer into a tablet, soak it in an ethanol solution for 24 h for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 h for solvent exchange to obtain the final product.

[0061] Example 6

[0062] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 96 g of deionized water. Dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0063] (2) After weighing 1.6 g of ferric chloride hexahydrate and dissolving it in 28.4 g of deionized water, weigh 3.4 g of tannic acid and add it to the iron ion solution and stir evenly to obtain a complex solution with a molar ratio of iron ions to tannic acid of 3:1.

[0064] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2) and stir to form a gel by flocculation, and centrifuge to obtain a polymer.

[0065] (4) After pressing the polymer into a tablet, soak it in an ethanol solution for 24 h for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 h for solvent exchange to obtain the final product.

[0066] Example 7

[0067] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 96 g of deionized water. Dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0068] (2) After weighing 4.86 g of ferric chloride hexahydrate and dissolving it in 25.1 g of deionized water, weigh 3.4 g of tannic acid and add it to the iron ion solution and stir evenly to obtain a complex solution with a molar ratio of iron ions to tannic acid of 9:1.

[0069] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2), stir to form a gel by flocculation, and centrifuge to obtain a polymer.

[0070] (4) After pressing the polymer into tablets, soak it in an ethanol solution for 24 hours for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 hours for solvent exchange to obtain the final product.

[0071] Example 8

[0072] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 96 g of deionized water, and dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0073] (2) Weigh 3.8 g of ferric chloride hexahydrate and dissolve it in 26.2 g of deionized water, then weigh 3.4 g of tannic acid and add it to the iron ion solution and stir evenly to obtain a complex solution with a molar ratio of iron ions to tannic acid of 7:1.

[0074] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2), stir to form a gel by flocculation, and centrifuge to obtain a polymer.

[0075] (4) After pressing the polymer into tablets, soak it in a mixed solvent of acetone and ethylene glycol (volume ratio 1:1) for 24 hours for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 hours for solvent exchange to obtain the final product.

[0076] Example 9

[0077] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 96 g of deionized water, and dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0078] (2) Weigh 3.8 g of ferric chloride hexahydrate and dissolve it in 26.2 g of deionized water, then weigh 3.4 g of tannic acid and add it to the iron ion solution and stir evenly to obtain a complex solution with a molar ratio of iron ions to tannic acid of 7:1.

[0079] (3) Slowly pour the polyvinyl alcohol solution into the complex solution in step (2), stir to form a gel by flocculation, and centrifuge to obtain a polymer.

[0080] (4) After pressing the polymer into tablets, soak it in ethylene glycol for 24 hours for dehydration to obtain an organic gel; then soak the organic gel in deionized water for 48 hours for solvent exchange to obtain the final product.

[0081] Comparative Example 1

[0082] (1) Weigh 4 g of polyvinyl alcohol with a molecular weight of 74,800 and dissolve it in 96 g of deionized water, and dissolve it in an oil bath at 95 °C for 2 h to obtain a polyvinyl alcohol solution.

[0083] (2) After weighing 3.8 g of ferric chloride hexahydrate and dissolving it in 26.2 g of deionized water, 3.4 g of tannic acid was weighed and added to the ferric ion solution and stirred evenly to obtain a complex solution with a molar ratio of ferric ions to tannic acid of 7:1.

[0084] (3) The polyvinyl alcohol solution was slowly poured into the mixed solution of step (2) and stirred and centrifuged to obtain a polymer.

[0085] (4) The polymer was pressed into tablets and directly soaked in deionized water for 48 hours for solvent exchange to obtain the final product.

[0086] In the form of trouser tearing, using an electronic universal material testing machine, the tensile properties of the materials prepared in Examples 1-9 and Comparative Example 1 were tested at a tensile rate of 100 mm / min. By analyzing the experimental results, the corresponding test data were obtained.

[0087] In order to better reflect that the preparation method of the present invention has important innovation, under the same test conditions, the tensile strength and other performance indexes of the samples prepared in Examples 1-9 and Comparative Example 1 were tested, and the test results are shown in Table 1.

[0088] Based on the current situation that the currently prepared physical hydrogels cannot balance strength and toughness, through reasonable material design, the hydrogel is given a special structure, so that when the material is subjected to external forces (such as tensile force and tearing force), it can disperse stress, increase the energy dissipation ability and prevent cracks from rapidly spreading in the material, thereby greatly improving the mechanical strength and toughness of the material.

[0089] First of all, it can be seen from Examples 1-9 that all the hydrogels have excellent mechanical properties. Compared with the comparative example, the mechanical properties of the comparative example are worse than those of the corresponding examples. This is because the interfacial binding force between the tannic acid-ferric ion complex and PVA is significantly improved after the material is soaked in ethanol. It can be seen from Examples 1-9 in Table 1 that the prepared physical hydrogels have excellent mechanical properties, and they are highly related to the molecular weight of polyvinyl alcohol, the concentration of polyvinyl alcohol, the molar ratio of ferric ions to tannic acid, and the type of poor solvent. In the examples listed in the present invention, the effects of different polyvinyl alcohol molecular weights, polyvinyl alcohol concentrations, ferric ion to tannic acid molar ratios, and poor solvent types on the mechanical properties of the materials were systematically investigated. Through optimization, the mechanical properties of Example 4 are the most excellent, and the fracture tensile strength reaches 6.51 MPa, the fracture strain reaches 840%, and the tearing toughness reaches 10434 J / m 2 , showing excellent mechanical strength.

[0090] From the performance test data in the examples, it can be seen that the mechanical strength of the physical hydrogel proposed by the present invention can be adjusted within a wide range by controlling different experimental factors, which provides more material choices with different mechanical properties for applications in multiple fields.

[0091] From the data published in Comparative Example 1, it can be seen that its tensile strength is only 1.97 MPa, the tensile strain at break is about 800%, and the tear toughness is only 2870 J / m 2 , and its performance is significantly lower than that of the examples, indicating that the method of adjusting the interface between tannic acid-iron ion complex and PVA through a poor solvent to improve the mechanical properties of the material in the present invention is highly effective.

[0092] Comparative Example 2 (Adv. Mater. 2020, 2004579) is a published literature report. A high-strength hydrogel was obtained by dissolving high-concentration PVA in DMSO solvent and then rehydrating it. The preparation of the material was achieved by controlling the intermolecular force of PVA by the solvent. However, its tensile properties and tear toughness are significantly weaker than the scheme proposed by the present invention. Therefore, it is very challenging to achieve a high-strength and tough hydrogel by a simple method. To better visually display the mechanical properties of the materials prepared by the present invention, Figure 1 For the material prepared in Example 4, after pre-cutting, a 2 Kg heavy object can be lifted at the cut without breaking, indicating its excellent tear resistance; Figure 2 and Figure 3 are the tensile stress-strain curve and the tear force-tensile displacement distance curve in the trouser tear test of the material prepared in Example 4, respectively, directly and quantitatively demonstrating the excellent mechanical strength and tear toughness of the material.

[0093] Table 1

[0094]

[0095] In summary, the present invention only uses three most commonly used and inexpensive raw materials such as tannic acid, ferric chloride hexahydrate, and polyvinyl alcohol, without any chemical polymerization process. The material preparation is completed only through three physical processes: co-mixing and flocculating to form a gel, dehydration treatment with a poor solvent, and solvent exchange and swelling in water. The whole process does not rely on any polymerization equipment and special process treatment equipment, etc., reflecting the advantages of high efficiency, low cost, low investment, and large-scale preparation, which are difficult to achieve by previous high-strength and tough hydrogel preparation technologies.

[0096] It should be noted that there are some publicly disclosed patent literatures in the prior art that have certain similarities with the present invention, but are completely different in essence.

[0097] For example, patent publication number CN115286885A discloses an environmentally friendly and efficient photothermal hydrogel, its preparation method and application. This patent prepares an aqueous photothermal material solution by mixing tannic acid and ferric chloride hexahydrate; prepares an aqueous polymer solution by mixing polyvinyl alcohol and a hydrophilic polymer compound; adds the aqueous photothermal material solution to the aqueous polymer solution and mixes them to obtain a photothermal hydrogel. Compared with the present invention, although it also uses raw materials such as tannic acid, iron ions, and polyvinyl alcohol, it only obtains a photothermal material with stable performance. The hydrogel strength performance of this comparative patent is very poor. Although the comparative patent also attempts to improve the mechanical strength of the material by incorporating agarose, its tensile strength is lower than 100KPa, and its mechanical toughness is even lower, indicating that it is difficult to achieve the goal of high strength and high toughness only through the blending of raw materials, and special strengthening treatment is required to improve the mechanical properties.

[0098] Another example is patent publication number CN118085334A, which discloses a high-tensile and anti-swelling polyvinyl alcohol-based hydrogel, its preparation method and application. This patent proposes a polyvinyl alcohol-based material, which is modified with trifluorobenzaldehyde on the side chain, and then undergoes solvent exchange with poor solvents such as ethanol and rehydration to obtain a high-tensile and anti-swelling hydrogel. Although its technical route involves the process of soaking in the poor solvent ethanol, this process is not the core step of its final performance. The core of its mechanical property improvement and anti-swelling performance lies in the trifluorobenzaldehyde block modified on the side chain of polyvinyl alcohol, which is clearly mentioned in this patent. To sum up, soaking in a poor solvent to enhance toughness has great selectivity for the initial material, and not all hydrogels can achieve significant enhancement and toughening by soaking in a poor solvent.

[0099] Aiming at the bottleneck problems in the field, the present invention uses cheap and easily available commercial raw materials, through a convenient and efficient material preparation method, proposes an innovative strategy for enhancing and toughening hydrogel materials, discovers an innovative new preparation method to prepare a new type of hydrogel material with excellent mechanical strength and tear toughness. Due to its excellent and comprehensive mechanical properties, the material prepared by this method will have important application prospects in many fields such as flexible electronics, energy, and biomimetic materials.

Claims

1. A preparation method of a high-strength and tough physical hydrogel, characterized in that, It includes the following steps: Prepare a polyvinyl alcohol solution by mixing polyvinyl alcohol and water; Dissolve ferric chloride hexahydrate in deionized water to obtain an iron ion solution; Add tannic acid to the iron ion solution to form a complex solution; Slowly pour the polyvinyl alcohol solution into the complex solution and stir to form a gel by flocculation, and then centrifuge to obtain a polymer; Soak the polymer in a poor solvent for dehydration to obtain an organic gel; Transfer the organic gel to an aqueous deionized water solution for solvent exchange to obtain a high-strength and tough physical hydrogel.

2. The preparation method of a high-strength and tough physical hydrogel according to claim 1, characterized in that: The concentration of the polyvinyl alcohol solution is 2 wt% to 8 wt%.

3. The preparation method of a high-strength and tough physical hydrogel according to claim 1 or 2, characterized in that: The molecular weight of the polyvinyl alcohol is one or more of 47000, 61000, 74800, 145000, and 195000.

4. The preparation method of a high-strength and tough physical hydrogel according to claim 1, characterized in that: The molar ratio of the iron ion to tannic acid is (3 to 9):

1.

5. The preparation method of a high-strength and tough physical hydrogel according to claim 1, characterized in that: The poor solvent is one or a combination of ethanol, ethylene glycol, glycerol, and acetone.

6. The preparation method of a high-strength and tough physical hydrogel according to claim 1, characterized in that: During the process of centrifuging to obtain the polymer, the centrifugation rate is 4000 to 8000 r / min.

7. The preparation method of a high-strength and tough physical hydrogel according to claim 1, characterized in that: The soaking time in the poor solvent is 12 to 36 hours.

8. The preparation method of a high-strength and tough physical hydrogel according to claim 1, characterized in that: The time for solvent exchange in the water is 24 to 48 hours.

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