A high-strength physically cross-linked hydrogel and its preparation method

Abstract

The present invention discloses a high-strength physically cross-linked hydrogel and a method for preparing the same. The method provides a hydrogel by transferring a hydrogel precursor solution to a spraying device for spraying, wherein the temperature of the hydrogel precursor solution is maintained within a first preset temperature, and the temperature of the spraying device is maintained within a second preset temperature. The preparation method utilizes readily available and inexpensive raw materials, has a simple preparation process and required equipment, and exhibits low energy consumption. It has wide applicability, significant economic potential, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and specifically relates to hydrogels, and in particular, to a high-strength physically cross-linked hydrogel and a preparation method thereof. Background Art

[0002] Hydrogel is a special type of soft and wet material, which is composed of a three-dimensional network of hydrophilic polymers and water filled in the network. Due to its high water absorption, stimulus responsiveness, permeability to small molecules and biocompatibility, it is widely used in water-retaining materials, biomedicine, medicine, chemical industry, agriculture and other fields. It also has good application prospects in drug controlled release, tissue engineering and other fields.

[0003] There are many preparation processes for hydrogel coatings, which can be roughly divided into spray-molding, brush-molding, dip-molding, and cast-molding.

[0004] In comparison, the advantages of spray forming are obvious, such as fast forming speed, high production efficiency, uniform distribution of materials on the substrate surface, and good surface finish of the resulting coating, which are particularly advantageous for hydrogels. However, since the synthesis and preparation of hydrogels often start from monomers, the forming process often requires chemical reactions such as polymerization and cross-linking reactions. The process conditions for spraying are often contrary to the conditions required for these reactions. Therefore, reports on the application of spray forming technology to hydrogels are very rare. Summary of the Invention

[0005] In order to overcome the above problems, the present invention provides a high-strength physically cross-linked hydrogel and a preparation method thereof.

[0006] In a first aspect, the present invention provides a method for preparing a high-strength physically cross-linked hydrogel. The method comprises transferring a hydrogel precursor solution into a spraying device for spraying to obtain a hydrogel; wherein

[0007] The temperature of the hydrogel precursor solution is maintained within a first preset temperature;

[0008] The temperature of the spraying device is maintained within a second preset temperature.

[0009] In a second aspect, the present invention provides a high-strength physically cross-linked hydrogel, which is obtained according to the preparation method of the first aspect.

[0010] The high-strength physically cross-linked hydrogel and its preparation method provided by the present invention have the following beneficial effects:

[0011] (1) The preparation method of the present invention has readily available and inexpensive raw materials, simple preparation process and required equipment, low energy consumption, wide applicability and huge economic benefit potential, and is suitable for large-scale industrial production;

[0012] (2) The raw materials of the hydrogel of the present invention have a wide range of choices, and the hydrogel plane size, thickness size and mechanical properties have excellent controllability;

[0013] (3) The hydrogel of the present invention has excellent mechanical properties and has broad application prospects in the fields of industry and biomedicine. DETAILED DESCRIPTION

[0014] The preferred embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0015] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, the elements defined by the phrase "comprises..." do not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the elements.

[0016] It is worth noting that the raw materials mentioned in the present invention are known and can be obtained commercially.

[0017] Spraying is a common surface treatment method. Spray forming involves using a spray device (including spray guns, spray pots, etc.) to disperse a pre-prepared material (mostly a polymer solution) into a uniform, fine mist of droplets. The droplets then fall onto the surface of the substrate, condensing into a film or coating that covers the surface, thereby modifying the surface properties. In some specialized applications, the spray coating can be peeled off to create a separate material.

[0018] However, the preparation of hydrogels often requires chemical reactions such as polymerization and cross-linking. The spray-coating process often violates the conditions required for these chemical reactions, making it difficult to effectively control the hydrogel.

[0019] To address the above-mentioned problems, the present invention provides a high-strength physically cross-linked hydrogel and a method for preparing the same. This method involves loading an uncooled hydrogel precursor solution into a spraying device and spraying it onto a substrate surface to form a layer of liquid hydrogel precursor film. Subsequently, simply by cooling the solution, physical cross-linking is achieved to form a hydrogel with a stable structure and excellent mechanical properties. This method is simple to operate, highly efficient, environmentally friendly, and safe. The resulting hydrogel is uniformly distributed and has a high surface gloss.

[0020] Specifically, in the first aspect, the present invention provides a method for preparing a high-strength physically cross-linked hydrogel. The preparation method is to transfer a hydrogel precursor solution into a spraying device for spraying to obtain a hydrogel; wherein

[0021] The temperature of the hydrogel precursor solution is maintained within a first preset temperature;

[0022] The temperature of the spraying device is maintained within a second preset temperature.

[0023] In the present invention, the hydrogel precursor solution may be heated and maintained at a first preset temperature before or during the transfer.

[0024] Research has found that if the temperature of the hydrogel precursor solution is too low, crosslinking will occur within the hydrogel precursor solution, which is not conducive to the transfer of the hydrogel precursor solution. In addition, due to its increased viscosity, it is not conducive to spraying. Therefore, the hydrogel precursor solution should be kept within an appropriate temperature range.

[0025] The first preset temperature is 50-110°C, preferably 65-100°C, more preferably 70-95°C, such as 80°C, 90°C or 95°C.

[0026] In the present invention, the spraying device may be placed in an oven at a second preset temperature, so that the spraying device is maintained at the second preset temperature level before or during the transfer.

[0027] Research has found that if the temperature of the spray device is low, the hydrogel precursor solution will produce a certain degree of cross-linking in the spray device, and the viscosity of the system will increase, causing the spray device to be blocked or unable to form a uniform hydrogel coating. Therefore, the spray device should be kept in an appropriate temperature range.

[0028] The second preset temperature is 30-90°C, preferably 40-80°C, more preferably 50-70°C, such as 60°C, 65°C or 70°C.

[0029] In a preferred embodiment of the present invention, after spraying is completed, a cooling treatment is further included, preferably natural (such as 10-30°C) or low-temperature (such as below 0°C) cooling (5-30h, such as 10-24h) until a formed hydrogel is obtained.

[0030] In the present invention, a hydrogel precursor solution maintained at a first preset temperature is rapidly transferred to a spray gun pot maintained at a second preset temperature. Spraying with the spray gun forms a layer of liquid hydrogel precursor film. During the cooling process, the molecular motion rate in the system gradually slows, and numerous stable, continuous hydrogen bonds (possibly even synergistic hydrogen bonds) form between the components of the hydrogel precursor film, resulting in a high-strength, physically cross-linked hydrogel with excellent mechanical properties. The thickness of the hydrogel can be controlled by controlling the spraying time or the number of spraying cycles.

[0031] The hydrogel precursor solution can be sprayed onto a substrate, which helps shape the hydrogel. The present invention does not particularly limit the material of the substrate, which can be metal, glass, ceramic, or polymer. The hydrogel is easily peelable after formation.

[0032] In a preferred embodiment of the present invention, the step of preparing the hydrogel precursor solution may include the following steps:

[0033] Step 1: Mix a first organic molecule and water to obtain a first solution.

[0034] Preferably, the first organic molecule is a water-soluble organic polymer. The water-soluble organic polymer is selected from at least one of a water-soluble natural polymer, a chemically modified natural polymer, and a synthetic polymer, preferably a water-soluble synthetic polymer, and more preferably at least one of polyvinyl pyrrolidone, polyethylene oxide, polyethylene glycol, polyacrylamide, polyacrylic acid, polymethacrylic acid, polyvinyl alcohol, polymaleic acid, and waterborne polyurethane.

[0035] More preferably, the mass concentration of the first organic molecule in the first solution is 0.1 to 30%, preferably 3 to 25%, and more preferably 12 to 22%.

[0036] The mass concentration of the first organic molecule significantly influences both the hydrogel's formation and the resulting hydrogel's mechanical properties. These two parameters directly influence the formation of a three-dimensional polymer network and the average molecular weight of the resulting network. Research has found that when the mass concentration of the first organic molecule falls within the aforementioned range, a three-dimensional polymer network is well-established.

[0037] In the present invention, the mixing process in step 1 includes heating and stirring to dissolve. The dissolving temperature is staged and includes at least two stages, such as two or three stages.

[0038] Preferably, when the dissolution temperature is divided into two sections, the dissolution temperature of the first section is less than or equal to the dissolution temperature of the second section.

[0039] For example, the first stage dissolution temperature is 80 to 100°C, preferably 85 to 95°C, and the second stage dissolution temperature is 100 to 120°C, preferably 105 to 110°C.

[0040] Preferably, when the dissolution temperature is divided into three sections, the dissolution temperature of the first section is less than or equal to the dissolution temperature of the second section, and greater than or equal to the dissolution temperature of the third section.

[0041] For example, the first stage dissolution temperature is 80-100°C, preferably 85-95°C, the second stage dissolution temperature is 100-120°C, preferably 105-110°C, and the third stage dissolution temperature is 50-80°C, preferably 65-75°C.

[0042] In the present invention, the first dissolution temperature is set to be less than or equal to the second dissolution temperature to prevent localized heat accumulation in the material system due to excessively rapid temperature rise. This is because, in the initial stages of the dissolution process, the mixture composed of the solid solute and the liquid solvent is in a very uneven state, resulting in poor heat conduction and insufficient heat transfer. Once a considerable degree of dissolution has been achieved, the material is relatively uniform. Raising the temperature at this point can accelerate the complete dissolution of the first organic molecule and form a uniform true solution. The third dissolution temperature is appropriately lowered because a uniform solution has already been formed, eliminating the need for an excessively high temperature. This is also for the safety and convenience of subsequent operations.

[0043] And / or, the stirring speed in step 1 is also staged, including at least two stages. Preferably, the stirring speed in the first stage is greater than or equal to the stirring speed in the second stage.

[0044] For example, the stirring speed in the first stage is 250 to 600 rpm, preferably 300 to 400 rpm; the stirring speed in the second stage is 100 to 400 rpm, preferably 150 to 250 rpm.

[0045] In the present invention, a higher stirring rate is first used to achieve sufficient stirring, which is beneficial to the dissolution of the first organic molecule and also beneficial to the uniform heat distribution within the material system; the stirring rate is then reduced because a large number of bubbles will be generated at a high stirring rate, which is not conducive to the subsequent spraying.

[0046] And / or, the heating power in step 1 is also staged, including at least two stages, for example, two stages or three stages. Preferably, the heating power of the first stage is greater than or equal to the heating power of the second stage. If it includes three stages, the heating power of the third stage is less than or equal to the heating power of the second stage.

[0047] For example, the heating power of the first section is 400-700W, preferably 450-600W; the heating power of the second section is 200-400W, preferably 250-350W; the heating power of the third section is 150-400W, preferably 100-350W.

[0048] In the present invention, heating with a higher power first can quickly increase the temperature, accelerate the dissolution rate, and improve work efficiency; then only a lower heating power is needed to quickly increase to the set temperature and maintain this temperature, which is beneficial to energy saving and environmental protection.

[0049] In a preferred embodiment of the present invention, the first solution is first heated to the first dissolution temperature at the first heating power and the first stirring speed; then, the first solution is heated to the second dissolution temperature at the second heating power and the second stirring speed, and maintained for a period of time (e.g., 0.5 to 3 hours); finally, heating is stopped for a period of time (e.g., 0.1 to 0.5 hours), and then the third dissolution temperature is reached and maintained at the third heating power and the second stirring speed, and stirring is continued until the bubbles are eliminated.

[0050] Research has found that when the first solution reaches the first dissolution temperature, the material has absorbed sufficient heat from the outside and has dissolved to a considerable extent, allowing the temperature to be maintained with a lower heating power. Furthermore, since the first organic molecule has dissolved to a considerable extent, reducing the stirring rate can prevent the generation of large bubbles that could affect subsequent spraying. Furthermore, a lower stirring rate can maintain a uniform temperature within the material system. Finally, after a uniform solution is formed, the temperature is lowered to maintain the solution within the third dissolution temperature, enabling safe transfer of the material into the spray tank and aligning with the spraying process.

[0051] Step 2: Mixing water and a second organic molecule to obtain a second solution.

[0052] The second organic molecule is a small organic molecule having a strong affinity for water; preferably, it can be at least one of the following 1) to 5):

[0053] 1) Polyhydroxy compounds, including small molecule compounds with two or more hydroxyl groups (such as polyols, polyphenols and polyhydroxy-substituted alicyclic compounds of various structural forms);

[0054] 2) Polyamino compounds, including small molecule compounds with two or more amino groups (such as various structural forms of polyamines, aromatic amines and polyamino-substituted alicyclic compounds, etc.);

[0055] 3) diamide small molecule compounds;

[0056] 4) Water-soluble organic small molecule compounds containing carboxyl groups;

[0057] 5) Water-soluble organic small molecule compounds containing thiol groups.

[0058] More preferably, the second organic molecule is selected from at least one of polyols, polyphenols and polyamines.

[0059] Specifically, the polyol is at least one selected from ethylene glycol, glycerol, butanediol, hexanediol, pentaerythritol, sorbitol and glucose, for example, ethylene glycol or glycerol;

[0060] The polyamine is at least one selected from ethylenediamine, hexamethylenediamine, p-phenylenediamine, hexamethylenetetramine and triethylenediamine;

[0061] The polyphenols are at least one selected from tannic acid, gallic acid, dopamine, protocatechuic acid, (+)-catechin, caffeic acid, p-hydroxybenzoic acid, resveratrol and quercetin, more preferably at least one selected from tannic acid, gallic acid and dopamine, such as tannic acid.

[0062] Polyphenols are a type of cross-linking agent with a large number of phenolic hydroxyl groups, which can form strong hydrogen bonds with the first organic polymer, greatly improving the strength of the hydrogel.

[0063] Preferably, the mass concentration of the second organic molecule in the second solution is 20 to 90%, preferably 40 to 85%, and more preferably 50 to 80%.

[0064] Research has found that when the mass fraction of the second organic molecule is within the above range, it can form a good synergistic hydrogen bond with the first organic molecule to construct a three-dimensional network structure and reduce the difficulty of cross-linking.

[0065] More preferably, the second organic molecule is selected from polyols, or polyols and polyphenols, for example, the second organic molecule is glycerol or glycerol and tannic acid.

[0066] Among them, research has found that when the second organic molecule contains a small amount of tannic acid, the mechanical strength of the prepared hydrogel will be significantly increased.

[0067] In the present invention, when the second organic molecule is glycerol and tannic acid, the mass ratio of glycerol to tannic acid is (20-70):1, preferably (30-60):1.

[0068] Step 3: Mix the first solution and the second solution to obtain a hydrogel precursor solution, and control the hydrogel precursor solution to be within a first preset temperature.

[0069] Preferably, the second solution is added dropwise to the first solution and stirred within a first preset temperature to obtain a hydrogel precursor solution.

[0070] The dripping rate of the second solution is 0.5 mL / min to 5 mL / min, preferably 1 mL / min to 3 mL / min.

[0071] The method of adding dropwise while stirring can ensure that the two solutions are fully miscible.

[0072] The second organic molecule serving as a cross-linking agent can form a cooperative hydrogen bond with the first organic molecule to serve as a cross-linking point.

[0073] In this step, on the one hand, the first organic molecule itself can undergo one or more of intramolecular or intermolecular Schiff base reactions, ionic bond crosslinking, hydrogen bonding or chain entanglement to achieve crosslinking; on the other hand, synergistic hydrogen bonds are formed between the first organic molecule and the second organic molecule to construct a three-dimensional network structure, reducing the difficulty of crosslinking. Its essence is physical crosslinking, and there is no need to add chemical crosslinking agents, initiators or use other physical initiation techniques, thus avoiding the residue of initiators and complicated operating procedures.

[0074] In the present invention, the hydrogel precursor solution at a first preset temperature is quickly transferred to a hot spray gun pot that has been preheated to a second preset temperature, and sprayed on the substrate to obtain a hydrogel coating attached to the substrate.

[0075] In a preferred embodiment of the present invention, the prepared hydrogel is further subjected to at least one freezing and thawing process, i.e., a "freeze-thaw" process. In the freezing environment, the first organic molecules crystallize at low temperatures. The crystalline domains serve as physical crosslinking points, increasing the crosslinking density within the hydrogel and thereby toughening the hydrogel.

[0076] Freezing is placing the hydrogel in an environment below 0°C (preferably -30 to -1°C, more preferably -25 to -5°C) for a period of time (preferably 10 to 30 hours, more preferably 15 to 24 hours), such as placing it in a constant temperature refrigerator.

[0077] Thawing is to place the frozen hydrogel at room temperature (20-30° C.) or above for a period of time (preferably 0.5-10 h, more preferably 4-8 h).

[0078] In this step, subjecting the prepared hydrogel to at least one "freeze-thaw" treatment can improve the mechanical strength of the hydrogel.

[0079] The hydrogel provided by the present invention contains a first organic molecule and a second organic molecule serving as a cross-linking agent. The hydrogel mainly relies on the formation of hydrogen bond cross-linking between the two to achieve the construction of a three-dimensional polymer network, thereby obtaining a hydrogel with high tensile strength and elastic modulus. At the same time, the raw materials have little effect on the water content of the hydrogel.

[0080] In a second aspect, the present invention provides a high-strength physically cross-linked hydrogel, which is obtained according to the preparation method of the first aspect.

[0081] In a preferred embodiment according to the present invention, the hydrogel has a tensile strength of 0.2 to 3.0 MPa, an elongation at break of 150 to 500%, and an elastic modulus of 0.15 to 0.9 MPa.

[0082] The present invention is further described below by way of specific examples. However, these examples are merely exemplary and do not constitute any limitation to the scope of the present invention. The raw materials in the present invention can all be obtained commercially.

[0083] Example

[0084] Example 1

[0085] Place 11.1g of polyvinyl alcohol (PVA) and 54.5g of water in a 250mL three-necked flask, mix, and heat with a thermostatted infrared heater and a precisely timed electric stirrer. Initially, stir to 90°C at 500W of heating power and 350 rpm. Then, continue heating to 105°C at 300W of heating power and 200 rpm. Heat at 105°C for 1 hour until the PVA dissolves. Finally, remove the flask from the heat, allow it to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm until all bubbles disappear. This yields the first solution.

[0086] Place 74.5 g of glycerol in a 100 mL beaker, add 20 g of water and stir to dissolve, and place on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0087] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0088] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0089] Example 2

[0090] Place 13.0g of polyvinyl alcohol (PVA) and 53.5g of water in a 250mL three-necked flask, mix, and heat with a thermostatic infrared heater and a precisely timed electric stirrer. Initially, stir to 90°C at 500W of heating power and 350 rpm. Then, continue heating to 105°C at 300W of heating power and 200 rpm. Heat at 105°C for 1 hour until the PVA dissolves. Finally, remove the flask from the heat, allow it to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm until all bubbles disappear. This yields the first solution.

[0091] Place 73.5 g of glycerol in a 100 mL beaker, add 20 g of water and stir to dissolve, and place on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0092] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0093] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0094] Example 3

[0095] Place 13.1g of polyvinyl alcohol and 49.0g of water in a 250mL three-necked flask, mix, and heat with a constant-temperature infrared heater and a precisely timed electric stirrer. Stir to 90°C at 550W of heating power and 350 rpm of stirring. Then, continue heating to 105°C at 350W of heating power and 200 rpm of stirring. Heat at 105°C for 1 hour. Finally, stop heating, allow to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm of stirring until all bubbles disappear, to obtain the first solution.

[0096] 59.4 g of glycerol was placed in a 100 mL beaker, 40.3 g of water was added and stirred to dissolve, and the mixture was placed on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0097] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0098] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0099] Example 4

[0100] Place 13.0g of polyvinyl alcohol and 67.0g of water in a 250mL three-necked flask, mix, and heat with a constant-temperature infrared heater and a precisely timed electric stirrer. Stir to 90°C at 500W of heating power and 350 rpm. Then, heat to 105°C at 300W of heating power and 200 rpm. Heat at 105°C for 1 hour. Finally, stop heating, allow to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm until all bubbles disappear. This yields the first solution.

[0101] 60.0 g of glycerol and 1.0 g of tannic acid were placed in a 100 mL beaker, 20.0 g of water was added and stirred to dissolve, and the mixture was placed on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0102] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0103] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0104] Example 5

[0105] Place 13.0g of polyvinyl alcohol and 67.0g of water in a 250mL three-necked flask, mix, and heat with a constant-temperature infrared heater and a precisely timed electric stirrer. Stir to 90°C at 500W of heating power and 350 rpm. Then, heat to 105°C at 300W of heating power and 200 rpm. Heat at 105°C for 1 hour. Finally, stop heating, allow to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm until all bubbles disappear. This yields the first solution.

[0106] 60.0 g of glycerol and 2.0 g of tannic acid were placed in a 100 mL beaker, 20.0 g of water was added and stirred to dissolve, and the mixture was placed on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0107] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0108] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0109] Example 6

[0110] Place 13.1g of polyvinyl alcohol and 49.0g of water in a 250mL three-necked flask, mix, and heat with a constant-temperature infrared heater and a precisely timed electric stirrer. Stir to 90°C at 550W of heating power and 350 rpm of stirring. Then, continue heating to 105°C at 350W of heating power and 200 rpm of stirring. Heat at 105°C for 1 hour. Finally, stop heating, allow to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm of stirring until all bubbles disappear, to obtain the first solution.

[0111] 59.4 g of glycerol was placed in a 100 mL beaker, 40.3 g of water was added and stirred to dissolve, and the mixture was placed on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0112] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0113] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0114] The obtained high-strength physical hydrogel was "frozen" at -25°C for 24 hours and then "thawed" at room temperature for 8 hours to obtain a hydrogel that had undergone "freeze-thaw" treatment.

[0115] Example 7

[0116] Place 13.0g of polyvinyl alcohol and 67.0g of water in a 250mL three-necked flask, mix, and heat with a constant-temperature infrared heater and a precisely timed electric stirrer. Stir to 90°C at 500W of heating power and 350 rpm. Then, heat to 105°C at 300W of heating power and 200 rpm. Heat at 105°C for 1 hour. Finally, stop heating, allow to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm until all bubbles disappear. This yields the first solution.

[0117] 60.0 g of glycerol and 1.0 g of tannic acid were placed in a 100 mL beaker, 20.0 g of water was added and stirred to dissolve, and the mixture was placed on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0118] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0119] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0120] The obtained high-strength physical hydrogel was "frozen" at -25°C for 24 hours and then "thawed" at room temperature for 8 hours to obtain a hydrogel that had undergone "freeze-thaw" treatment.

[0121] Example 8

[0122] Place 13.0g of polyvinyl alcohol and 67.0g of water in a 250mL three-necked flask, mix, and heat with a constant-temperature infrared heater and a precisely timed electric stirrer. Stir to 90°C at 500W of heating power and 350 rpm. Then, heat to 105°C at 300W of heating power and 200 rpm. Heat at 105°C for 1 hour. Finally, stop heating, allow to cool naturally for 15 minutes, then heat to and maintain 75°C at 300W of heating power and 200 rpm until all bubbles disappear. This yields the first solution.

[0123] 60.0 g of glycerol and 2.0 g of tannic acid were placed in a 100 mL beaker, 20.0 g of water was added and stirred to dissolve, and the mixture was placed on an ultrasonic cleaner for 30 minutes to fully dissolve to obtain a second solution.

[0124] The second solution was added dropwise to the first solution, and stirred at 95°C for 120 min to obtain a hydrogel precursor solution;

[0125] Clean the spray gun and spray pot beforehand and dry them in a 60°C oven. Remove the spray gun and spray pot, transfer the hydrogel precursor solution into the spray pot, connect the spray gun and spray pot, and begin spraying. Leave the sprayed substrate horizontally at room temperature for 24 hours to obtain a high-strength physically cross-linked hydrogel.

[0126] The obtained high-strength physical hydrogel was "frozen" at -25°C for 24 hours and then "thawed" at room temperature for 8 hours to obtain a hydrogel that had undergone "freeze-thaw" treatment.

[0127] Comparative Example

[0128] Comparative Example 1

[0129] The preparation process of Example 1 was repeated, except that the second solution was not prepared and the first solution was directly transferred to the spray gun pot. It was finally found that the spraying could not form the sample, and no spray-formed sample was obtained.

[0130] Comparative Example 2

[0131] The preparation process of Example 3 was repeated, except that the hydrogel precursor solution was quickly transferred to a mold consisting of a glass plate and a silicone frame (both 2 mm thick). The mold was then frozen at -25°C for 24 hours and then thawed at 25°C for 8 hours to obtain a cast sample.

[0132] Experimental example

[0133] The mechanical properties of the high-strength physically cross-linked hydrogels prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were measured, including tensile strength, elongation at break, and elastic modulus. The results are shown in Table 1.

[0134] Table 1. Mechanical properties of high-strength physically cross-linked hydrogels

[0135] Tensile strength / MPa Elongation at break / % Elastic modulus / MPa Example 1 0.32 220 0.17 Example 2 0.33 230 0.19 Example 3 0.68 340 0.37 Example 4 0.89 360 0.54 Example 5 1.37 390 0.77 Example 6 0.84 270 0.72 Example 7 1.15 360 0.55 Example 8 1.35 400 0.67 Comparative Example 1 - - - Comparative Example 2 0.38 570 0.057

[0136] The present invention has been described in detail above with reference to preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are merely illustrative explanations of the present invention and do not constitute any limitation on the scope of protection of the present invention. Various improvements, equivalent substitutions, or modifications may be made to the technical content of the present invention and its embodiments without departing from the spirit and scope of protection of the present invention, and all of these fall within the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing a high-strength physically cross-linked hydrogel, characterized in that: The hydrogel is obtained by transferring the hydrogel precursor solution to a spraying device for spraying, and then cooling the solution after the spraying is completed; wherein The temperature of the hydrogel precursor solution is maintained within a first preset temperature; The temperature of the spraying device is maintained within a second preset temperature; The first preset temperature is 50~110℃; The second preset temperature is 30~90℃; The preparation of the hydrogel precursor solution comprises the following steps: Step 1: Mixing a first organic molecule and water to obtain a first solution. The first organic molecule is polyvinyl alcohol, and the mass concentration of the first organic molecule in the first solution is 0.1-30%; Step 2: mixing water and a second organic molecule to obtain a second solution; The second organic molecule is glycerol, and the mass concentration of the second organic molecule in the second solution is 20-90%; Step 3: Mix the first solution and the second solution to obtain a hydrogel precursor solution, and control the hydrogel precursor solution to be within a first preset temperature.

2. The preparation method according to claim 1, characterized in that The first preset temperature is 65-100°C; and / or The second preset temperature is 40~80℃.

3. The preparation method according to claim 1, characterized in that The mass concentration of the first organic molecule in the first solution is 3-25%.

4. The preparation method according to claim 1, characterized in that In step 1, the mixing process includes heating and stirring to dissolve; in The dissolution temperature is a staged process consisting of at least two stages; and / or The stirring speed is staged and includes at least two stages.

5. The preparation method according to claim 4, characterized in that When the dissolution temperature is divided into two sections, the dissolution temperature of the first section is less than or equal to the dissolution temperature of the second section; When the dissolution temperature is divided into three sections, the dissolution temperature of the first section is less than or equal to the dissolution temperature of the second section, and greater than or equal to the dissolution temperature of the third section; The stirring speed of the first stage is greater than or equal to the stirring speed of the second stage.

6. The preparation method according to claim 1, characterized in that In step 2, the mass concentration of the second organic molecule in the second solution is 40-85%.

7. The preparation method according to claim 1, characterized in that The method further comprises subjecting the prepared hydrogel to at least one freezing and thawing process.

8. A high-strength physically cross-linked hydrogel, wherein: The hydrogel is obtained according to any one of claims 1 to 7.