Hydrogel preparation method based on freezing-soaking synergistic effect and hydrogel

Abstract

The invention belongs to the technical field of hydrogel materials, and relates to a hydrogel preparation method based on a freezing-soaking synergistic effect and hydrogel. The method comprises the following steps: stirring and mixing a sodium alginate aqueous solution and soluble sodium salt to obtain an alginate precursor mixed solution; dropwise adding a cross-linking agent solution into the alginate precursor mixed solution, and uniformly stirring to obtain a pre-gel solution; pouring the pre-gel solution into a mold for curing treatment to generate cured single-network alginate hydrogel; carrying out freezing treatment on the cured single-network alginate hydrogel in a low-temperature environment, so as to generate frozen single-network alginate hydrogel; and putting the frozen single-network alginate hydrogel to room temperature, and soaking the frozen single-network alginate hydrogel in ultrapure water to generate the target single-network alginate hydrogel based on the freezing-soaking synergistic effect. Based on the method, the strength and toughness of the single-network alginate hydrogel are enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogel materials, and in particular relates to a hydrogel preparation method based on freezing-immersion synergy and the hydrogel. Background Art

[0002] Natural load-bearing materials often show a combination of contradictory mechanical properties, for example, wood is light and strong, nacre is hard and elastic, and muscles and tendons are soft and tough. The special properties of these materials have led to their widespread use in various structural applications. Among many fields, hydrogels, as an excellent structural material, have been widely used in wearable electronics, artificial scaffolds, soft robots, underwater communications and other fields. These applications have put forward higher requirements on the mechanical properties of hydrogels.

[0003] However, traditional hydrogels generally have the problems of low strength and easy permanent fracture, which limits their application in practical engineering. For example, alginate single network hydrogel breaks when stretched to 1.2 times its original length, and its tensile properties are poor, far from meeting the requirements of high load, impact resistance and large deformation. This phenomenon greatly limits the use of hydrogels in applications with high strength and durability requirements.

[0004] In summary, hydrogels in the prior art generally have the problems of low strength and easy permanent fracture, which limits their performance in practical applications such as high load, impact resistance and large deformation. Summary of the invention

[0005] The embodiments of the present invention provide a method for preparing a hydrogel based on freeze-immersion synergy and a hydrogel, which at least solve the problem of low strength and easy permanent fracture of the hydrogel in the related art.

[0006] According to a first aspect of an embodiment of the present invention, a method for preparing a hydrogel based on freezing-immersion synergy is provided, comprising: The sodium alginate aqueous solution and the soluble sodium salt are stirred and mixed to obtain an alginate precursor mixed solution; Adding a crosslinking agent solution dropwise to the alginate precursor mixed solution and stirring evenly to obtain a pre-gel solution; pouring the pre-gel solution into a mold for curing to generate a cured single-network alginate hydrogel; Freezing the solidified single-network alginate hydrogel in a low-temperature environment to generate a frozen single-network alginate hydrogel; The frozen single-network alginate hydrogel is placed at room temperature and then immersed in ultrapure water to generate a target single-network alginate hydrogel based on the synergistic effect of freezing and immersion.

[0007] According to an embodiment of the present invention, it also includes: At room temperature, slowly adding sodium alginate into ultrapure water and stirring evenly to form a uniform and transparent sodium alginate aqueous solution; Among them, the mass fraction of sodium alginate is 1 wt. % to 4 wt. %, and the stirring time after the sodium alginate and the ultrapure water are mixed is 8 hours to 24 hours.

[0008] According to an embodiment of the present invention, the stirring time of the sodium alginate aqueous solution and the soluble sodium salt is 5 minutes to 30 minutes; Wherein, the soluble sodium salt is sodium pyrophosphate, sodium citrate, sodium oxalate, sodium carbonate or sodium sulfate, and the mass ratio of the soluble sodium salt to the cross-linking agent in the cross-linking agent solution is 0 wt. % to 40 wt. %.

[0009] According to an embodiment of the present invention, the stirring time when the crosslinking agent solution is added dropwise to the alginate precursor mixed solution and stirred evenly is 5 minutes to 30 minutes; The crosslinking agent in the crosslinking agent solution is anhydrous calcium sulfate or dihydrated calcium sulfate, and the mass ratio of the crosslinking agent to the sodium alginate is 10. wt. % to 95% wt. %.

[0010] According to an embodiment of the present invention, after adding the crosslinking agent solution dropwise to the alginate precursor mixed solution and stirring evenly to obtain a pre-gel solution, the method further comprises: The pre-gel solution is subjected to a mixing and degassing treatment by a mixing and degassing machine to eliminate bubbles generated during the stirring process; The mixing time of the mixed degassing treatment is 30 seconds to 60 seconds, the degassing time of the mixed degassing treatment is 30 seconds to 60 seconds, and the number of times of the mixed degassing treatment is 1 to 3 cycles.

[0011] According to an embodiment of the present invention, the step of pouring the pre-gel solution into a mold for curing to generate a cured single-network alginate hydrogel comprises: Pour the pre-gel solution into the mold, and let it stand and solidify at room temperature to eliminate bubbles generated during the solution transfer process; The mold is encapsulated by using a glass plate coated with a nano super-hydrophobic self-cleaning coating; The encapsulated mold is left to stand and solidify at room temperature to obtain the solidified single-network alginate hydrogel.

[0012] According to an embodiment of the present invention, when the pre-gel solution is poured into the mold and allowed to stand at room temperature to eliminate bubbles generated during the solution transfer process, the standing time is 0.5 hours to 1 hour; when the encapsulated mold is allowed to stand and solidify at room temperature, the standing and solidification time is 12 hours to 48 hours.

[0013] According to an embodiment of the present invention, the solidified single-network alginate hydrogel is subjected to freezing treatment in a low-temperature environment to generate a frozen single-network alginate hydrogel, comprising: The solidified single-network alginate hydrogel is placed in the low-temperature environment for freezing treatment for 12 hours to 72 hours to obtain the frozen single-network alginate hydrogel, wherein the temperature of the low-temperature environment is -10°C to -25°C.

[0014] According to an embodiment of the present invention, the soaking time of the soaking treatment is 12 hours to 72 hours.

[0015] According to a second aspect of an embodiment of the present invention, a single-network alginate hydrogel is provided. The single-network alginate hydrogel is prepared according to the method for preparing a hydrogel based on freeze-immersion synergy described in the first aspect.

[0016] According to the hydrogel preparation method based on the freezing-immersion synergistic effect provided by the embodiment of the present invention, the strength and toughness of the single-network alginate hydrogel can be effectively enhanced. First, the solidified single-network alginate hydrogel is frozen and then placed at room temperature and directly immersed in ultrapure water. The freezing process not only provides an ion channel with a microstructure for subsequent immersion toughening, but also prepares polymer chains for the strong hydrophobic aggregation and crystallization caused by subsequent immersion through polymer concentration and close stacking. At the same time, the ultrapure water immersion process allows the excess slightly soluble cross-linking agent in the curing process to continue to dissolve, forming a hypertonic salt solution, thereby further increasing the ionic cross-linking density of the hydrogel and achieving the effect of salting out toughening. The synergistic effect of freezing and immersion introduces an energy dissipation mechanism, significantly enhances the mechanical properties of alginate hydrogels, solves the problem of weak and fragile mechanical properties faced by traditional alginate hydrogels in practical applications, and provides an innovative method for strengthening and toughening alginate hydrogels, thereby providing a new solution for its practical application in engineering fields such as high load, impact resistance and large deformation.

[0017] The details of one or more embodiments of the invention are set forth in the following drawings and description so that other features, objects, and advantages of the invention are more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other embodiments can be obtained based on these drawings without creative work.

[0019] Figure 1 A flow chart of a method for preparing a hydrogel based on freezing-immersion synergy provided in an embodiment of the present invention.

[0020] Figure 2 The present invention provides a flowchart of a pre-gel solution curing method according to an embodiment of the present invention.

[0021] Figure 3 A flow chart of another method for preparing a hydrogel based on freezing-immersion synergy provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Embodiments of the present embodiment will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present embodiment are shown in the accompanying drawings, it should be understood that the present embodiment can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein, which are instead provided for a more thorough and complete understanding of the present embodiment. It should be understood that the drawings and embodiments of the present embodiment are only for exemplary purposes and are not intended to limit the scope of protection of the present embodiment.

[0023] Hydrogels are widely used in many fields, such as wearable electronic devices, artificial tissue scaffolds, soft robots, and underwater communications, due to their excellent hydration properties and biocompatibility. With the continuous development of related technologies, higher requirements are put forward for the mechanical properties of hydrogels, especially in applications under extreme conditions such as high load, impact resistance, and large deformation. The practical application of traditional hydrogels is limited by their low strength and easy permanent fracture.

[0024] At present, a variety of methods have been used to enhance the mechanical properties of hydrogels, such as improving their stretchability and fracture resistance by designing double network hydrogels and composite hydrogels. However, most of these methods have certain limitations, such as complex manufacturing processes, high costs, or difficulty in improving both strength and toughness. Therefore, how to improve the strength and toughness of hydrogels at the same time through simple and efficient methods has become a technical problem that needs to be solved urgently in this field.

[0025] Figure 1 The flowchart of a method for preparing a hydrogel based on freezing-immersion synergy provided by an embodiment of the present invention is as follows. Figure 1 As shown, the method includes the following steps.

[0026] Step S101, stirring and mixing the sodium alginate aqueous solution and the soluble sodium salt to obtain an alginate precursor mixed solution.

[0027] Step S102, adding a crosslinking agent solution dropwise to the alginate precursor mixed solution and stirring evenly to obtain a pre-gel solution.

[0028] Step S103, pouring the pre-gel solution into a mold for curing to generate a cured single-network alginate hydrogel.

[0029] Step S104, freezing the solidified single-network alginate hydrogel in a low-temperature environment to generate a frozen single-network alginate hydrogel.

[0030] Step S105, after the frozen single-network alginate hydrogel is cooled to room temperature, it is immersed in ultrapure water to generate a target single-network alginate hydrogel based on the freezing-immersion synergistic effect.

[0031] First, the sodium alginate aqueous solution and the soluble sodium salt are stirred and mixed to obtain an alginate precursor mixed solution.

[0032] In this embodiment, before stirring and mixing the sodium alginate aqueous solution and the soluble sodium salt, the sodium alginate aqueous solution needs to be prepared first.

[0033] Specifically, when preparing the sodium alginate aqueous solution, sodium alginate can be slowly added to ultrapure water at room temperature and stirred evenly to form a uniform and transparent sodium alginate aqueous solution. That is, sodium alginate is slowly added to ultrapure water and stirred sufficiently until a uniform and transparent sodium alginate aqueous solution is formed.

[0034] Sodium alginate is a natural polysaccharide that can usually be dissolved in water to form a transparent solution. In order to avoid the influence of impurities and pH value on the stability of the sodium alginate aqueous solution, ultrapure water is selected instead of ordinary water source in this embodiment. In the process of preparing the sodium alginate aqueous solution, the purpose of slowly adding sodium alginate is to avoid the formation of undissolved sodium alginate particles, accelerate the dissolution of sodium alginate, ensure the uniformity of the aqueous solution, and facilitate the subsequent curing reaction.

[0035] In practical applications, the mass fraction of sodium alginate can be 1 wt. % to 4 wt. % to ensure that the solution has good fluidity and uniformity. In the preparation process of the sodium alginate aqueous solution, the stirring time should be long enough to ensure that the sodium alginate is completely dissolved in the ultrapure water to form a uniform and transparent sodium alginate aqueous solution. Optionally, the stirring time after the sodium alginate and the ultrapure water are mixed can be 8 hours to 24 hours.

[0036] On the basis of preparing the sodium alginate aqueous solution, soluble sodium salt is further added for mixing and stirring to obtain an alginate precursor mixed solution.

[0037] Specifically, the stirring time for mixing and stirring after adding the soluble sodium salt to the sodium alginate aqueous solution can be 5 minutes to 30 minutes. The addition of the soluble sodium salt ensures that a hydrogel network with high crosslinking density and uniformity is formed in the subsequent crosslinking reaction, thereby enhancing the mechanical strength and toughness of the hydrogel. In practical applications, the soluble sodium salt can be sodium pyrophosphate, sodium citrate, sodium oxalate, sodium carbonate or sodium sulfate. Among them, the mass ratio of the soluble sodium salt to the crosslinking agent in the crosslinking agent solution is 0. wt. % to 40 wt. %.

[0038] Then, the crosslinking agent solution is added dropwise to the alginate precursor mixed solution and stirred evenly to obtain a pre-gel solution.

[0039] In this embodiment, before preparing the pre-gel solution, a cross-linking agent solution needs to be prepared. Specifically, the cross-linking agent can be dissolved in an appropriate amount of solvent to prepare a cross-linking agent solution. In practical applications, the mass ratio of the cross-linking agent to the sodium alginate can be 10:1. wt. % to 95% wt. Wherein, the cross-linking agent can be anhydrous calcium sulfate or dihydrated calcium sulfate.

[0040] After obtaining the cross-linking agent solution, the cross-linking agent solution can be added dropwise into the alginate precursor mixed solution and stirred evenly to obtain a pre-gel solution.

[0041] In practical applications, calcium ions in the crosslinker can react with the carboxyl groups on the sodium alginate molecules to form stable ionic bonds, thereby generating a crosslinked network structure of alginate hydrogel. By adding the crosslinker solution dropwise, the crosslinking reaction process can be ensured to proceed evenly, thereby improving the homogenization of the hydrogel.

[0042] After adding the crosslinking agent to the mixed solution of the alginate precursor, the crosslinking agent and the sodium alginate can be fully reacted by stirring to form a hydrogel with a crosslinked structure. In this process, the stirring time and speed need to be set to ensure the uniformity of the crosslinking reaction. Optionally, the stirring time can be 5 minutes to 30 minutes to ensure the full reaction of the crosslinking agent and the sodium alginate.

[0043] There may be a large number of bubbles in the pre-gel solution that has not been mixed and degassed, and the bubbles will cause uneven distribution inside the hydrogel, affecting the mechanical properties, especially in high-load and high-strength applications, the presence of bubbles may cause cracks and fractures in the hydrogel. Therefore, after obtaining the pre-gel solution, it is necessary to first perform a mixing and degassing treatment on the pre-gel solution. By mixing and degassing to eliminate the bubbles generated during the stirring process, the overall structure and performance of the hydrogel can be improved.

[0044] In this embodiment, a mixing and degassing machine can be used to perform a mixing and degassing treatment on the pre-gel solution. In practical applications, when using a mixing and degassing machine, the processing parameters (mixing time, degassing time) during the mixing and degassing treatment can be set. Optionally, the mixing time can be set to 30 seconds to 60 seconds, and the degassing time can be set to 30 seconds to 60 seconds. Further optionally, the pre-gel solution can be subjected to one or more mixing and degassing treatments according to the actual treatment situation. Specifically, the pre-gel solution can be subjected to 1 to 3 mixing and degassing cycles using a mixing and degassing machine.

[0045] After the pregel solution is mixed and degassed, the pregel solution can be poured into a mold for curing to generate a cured single-network alginate hydrogel.

[0046] Figure 2 Flow chart of a pre-gel solution curing method provided by an embodiment of the present invention. Figure 2 As shown, the method includes the following steps.

[0047] Step S201, pouring the pre-gel solution into a mold and leaving it to stand at room temperature to eliminate bubbles generated during the stirring process.

[0048] In this embodiment, the mixed and degassed pre-gel solution is poured into a pre-prepared mold and allowed to stand at room temperature to release the bubbles inside the pre-gel solution and solidify. Solidification is the process of hydrogel formation, when the pre-gel solution begins to change from liquid to solid. During the standing process, the bubbles in the pre-gel solution will rise to the liquid surface, and removing the bubbles will help improve the uniformity and mechanical properties of the hydrogel. In practical applications, the standing time is 0.5 to 1 hour to ensure that the bubbles are completely eliminated.

[0049] Optionally, the mold can be a container of any shape, and the specific shape can be selected according to the desired hydrogel morphology.

[0050] Step S202, encapsulating the mold using a glass plate coated with a nano super-hydrophobic self-cleaning coating.

[0051] In this embodiment, the encapsulation process can prevent water loss during the curing process, maintain the stability of the hydrogel, and ensure that its internal structure is not disturbed during the entire curing process. The use of the nano super hydrophobic coating helps prevent the hydrogel from adhering to the mold surface, enhances the self-cleaning function, and reduces pollution.

[0052] Step S203 , leaving the encapsulated mold to stand at room temperature to obtain a solidified single-network alginate hydrogel.

[0053] In this embodiment, the encapsulated mold can be left to stand for 12 to 48 hours until the hydrogel is completely solidified to form a solidified single-network alginate hydrogel.

[0054] Subsequently, the solidified single-network alginate hydrogel can be frozen in a low-temperature environment to generate a frozen single-network alginate hydrogel.

[0055] In this embodiment, the solidified single-network alginate hydrogel is placed in a low-temperature environment for freezing treatment, and the freezing temperature can be set between -10°C and -25°C, and the freezing time is 12 hours to 72 hours. This process can form microstructured ion channels inside the gel, and the close stacking between polymer chains helps to enhance the mechanical properties of the gel.

[0056] The freezing process not only promotes the microstructural optimization of alginate hydrogels, but also promotes the further accumulation and contraction of polymer chains through the low temperature environment, thereby improving the mechanical stability of the hydrogels. After freezing, a structure with microscopic channels is formed inside the hydrogel, which provides a good foundation for the subsequent immersion enhancement process.

[0057] Finally, the frozen single-network alginate hydrogel was cooled to room temperature and then immersed in ultrapure water to generate the target single-network alginate hydrogel based on the freezing-immersion synergistic effect.

[0058] In this embodiment, the frozen alginate hydrogel is taken out from the low temperature environment, restored to room temperature, and immersed in ultrapure water for 12 to 72 hours. During the immersion process, the excess slightly soluble cross-linking agent continues to dissolve and form a hypertonic salt solution.

[0059] The purpose of the immersion treatment is to further increase the crosslinking density of the hydrogel through the effects of solvent exchange and ion dissolution. Ultrapure water can dissolve the incompletely reacted crosslinking agent in the alginate hydrogel during the immersion process, increase the ion crosslinking density, and enhance the mechanical strength and toughness of the hydrogel. After water molecules enter the hydrogel network structure, they can improve its stability and uniformity at the microscopic scale.

[0060] In order to facilitate understanding of the hydrogel preparation method based on freezing-immersion synergy provided in the embodiment of the present invention, the hydrogel preparation method based on freezing-immersion synergy provided in the embodiment of the present invention is further described below in conjunction with specific examples.

[0061] Figure 3 A flow chart of another method for preparing a hydrogel based on freezing-immersion synergy provided in an embodiment of the present invention. Figure 3 As shown, in this embodiment, sodium pyrophosphate is used as a soluble sodium salt and anhydrous calcium sulfate is used as a cross-linking agent to prepare a target single-network alginate hydrogel.

[0062] Step S301, preparing a sodium alginate aqueous solution.

[0063] In this example, 1.5 g of sodium alginate (chemical purity ≥ 98%) was added to 100 mL of ultrapure water and stirred at room temperature for about 12 hours to ensure that the sodium alginate was completely dissolved to form a uniform, transparent sodium alginate aqueous solution. The mass fraction of sodium alginate was 1.5 wt. %, at this concentration, sodium alginate can better form a stable hydrogel network.

[0064] Step S302, preparing an alginate precursor mixed solution.

[0065] In this embodiment, 0.15 g of sodium pyrophosphate was added to the sodium alginate aqueous solution and stirred for 5 minutes to ensure that the sodium pyrophosphate was completely dissolved and uniformly mixed with the sodium alginate aqueous solution to form an alginate precursor mixed solution. The addition of sodium pyrophosphate can improve the uniformity of the ionic crosslinking reaction and is expected to simultaneously increase the ionic crosslinking density of the hydrogel.

[0066] Step S303, preparing a cross-linking agent solution.

[0067] In this example, 0.75 g of anhydrous calcium sulfate was dissolved in 20 mL of ultrapure water to obtain a cross-linking agent solution.

[0068] Step S304, preparing a pre-gel solution.

[0069] In this embodiment, the crosslinking agent solution obtained in the above steps is added dropwise to the mixed solution of alginate precursor, and stirred for 15 minutes to ensure that the crosslinking agent and the sodium alginate aqueous solution react fully, and finally obtain a pre-gel solution. The mass ratio of the added amount of the crosslinking agent to the sodium alginate is 1:2 (i.e., the mass ratio of sodium alginate to anhydrous calcium sulfate is 2:1), and this ratio helps to form a moderately crosslinked gel structure.

[0070] Step S305, performing a mixing and degassing process on the pre-gel solution.

[0071] In this embodiment, in order to remove bubbles in the pre-gel solution, a mixing and degassing machine was used to perform a mixing and degassing process.

[0072] First, the pre-gel solution was transferred to a mixing and degassing machine for 30 seconds of rapid mixing, followed by 1 minute of degassing. This process was repeated twice to ensure that no bubbles remained in the solution.

[0073] Step S306, preparing a solidified single-network alginate hydrogel.

[0074] In this embodiment, the pre-gel solution was poured into a national standard type 2 dumbbell-shaped mold and allowed to stand at room temperature for 0.5 hours to further eliminate bubbles. The mold was then encapsulated using a glass plate coated with a nano super-hydrophobic self-cleaning coating and allowed to stand at room temperature for 24 hours until the pre-gel solution was completely cured to form a solidified single-network alginate hydrogel.

[0075] Step S307, preparing a frozen single-network alginate hydrogel.

[0076] In this embodiment, the solidified single-network alginate hydrogel is taken out from the dumbbell-shaped mold and placed in a low-temperature environment for freezing treatment. The freezing temperature is set to -15°C and the freezing time is 48 hours. During this process, the water inside the alginate hydrogel crystallizes to form microstructured ion channels, and the close stacking between the polymer chains increases the mechanical stability of the hydrogel.

[0077] Step S308, immersing the frozen single-network alginate hydrogel in ultrapure water.

[0078] In this embodiment, the frozen single-network alginate hydrogel is taken out from the low-temperature environment and immediately immersed in ultrapure water for 24 hours. During this process, the excess slightly soluble cross-linking agent will continue to dissolve to form a hypertonic salt solution, and the cross-linking density of the alginate hydrogel will be further increased, thereby enhancing the mechanical properties and toughness of the hydrogel.

[0079] Step S309, obtaining the target single-network alginate hydrogel.

[0080] In this embodiment, after the frozen single-network alginate hydrogel is soaked in ultrapure water, the crosslinking density in the alginate hydrogel is greatly increased, and the mechanical strength and toughness of the hydrogel are significantly enhanced. The target single-network alginate hydrogel finally obtained can be applied to engineering fields such as high load, impact resistance, and large deformation.

[0081] Through the above implementation steps, the method of the embodiment of the present invention effectively improves the mechanical properties of alginate hydrogel. The microstructured ion channels introduced by the freezing treatment and the ionic cross-linking in the subsequent immersion treatment significantly enhance the strength and toughness of the hydrogel, solving the problem of insufficient mechanical properties and easy breakage of traditional alginate hydrogel. The degassing treatment removes bubbles in the solution, effectively improving the uniformity and stability of the hydrogel, so that the hydrogel can show better performance in high-load and high-intensity applications.

[0082] The single-network alginate hydrogel prepared by this method has excellent mechanical properties and is particularly suitable for engineering applications that have high requirements on the strength, toughness and durability of hydrogels, such as wearable electronic devices, artificial scaffolds, soft robots, hydraulic support devices and underwater communication systems.

[0083] In order to compare the effects of different treatment methods on the maximum tensile strength of single-network alginate hydrogels, and to verify the significant toughening effect of the freezing-immersion synergistic treatment on the mechanical properties of the hydrogels. The embodiment of the present invention verifies its improvement on the performance of the hydrogel by setting up a control group and multiple test groups. Among them, the control group uses the solidified single-network alginate hydrogel as the control group, while the experimental group uses different treatment methods (freezing treatment, immersion treatment and freezing-immersion synergistic treatment) to study its improvement on the performance of the hydrogel.

[0084] Example 1: Control group (untreated solidified single network alginate hydrogel) The hydrogel used in the control group was a solidified single-network alginate hydrogel, and the specific preparation process was as follows: 1. Preparation of pre-gel solution: (1) 3 g of sodium alginate was slowly added into 89.16 g of ultrapure water and mechanically stirred at room temperature until it was completely dissolved to form a uniform, transparent sodium alginate aqueous solution.

[0085] (2) Add 0.46 g of sodium pyrophosphate to the sodium alginate aqueous solution and stir for 10 minutes until the sodium pyrophosphate is completely dissolved to form a uniform alginate precursor mixed solution (sodium alginate-sodium pyrophosphate mixed aqueous solution).

[0086] (3) Continue to add 7.44 g of calcium sulfate dihydrate solution (2.44 g of calcium sulfate dihydrate dissolved in 5 g of ultrapure water) dropwise and stir for 10 minutes to obtain a pre-gel solution.

[0087] 2. Mixing and degassing treatment of the pre-gel solution: Use a mixing and degassing machine to mix and degas the pre-gel solution. The mixing time is 30 seconds, the degassing time is 30 seconds, and the mixing and degassing cycle is 1 time.

[0088] 3. Curing treatment: (1) Pour the degassed pre-gel solution into an acrylic mold and let it stand at room temperature for 1 hour to remove bubbles.

[0089] (2) The mold is encapsulated using a glass plate coated with a nano-superhydrophobic self-cleaning coating and allowed to stand for curing at room temperature for 24 hours to obtain a cured single-network alginate hydrogel, which is then demolded and set aside.

[0090] The solidified single-network alginate hydrogel sample was directly used for uniaxial tensile test in an environment of 23±2°C and 30±3% humidity. The test results showed that the maximum tensile strength of the untreated solidified single-network alginate hydrogel was only 16.28±2.44 kPa. Example 2: Experimental Group 1 (Freezing Treatment Only) The solidified single-network alginate hydrogel used in Experimental Group 1 was prepared in exactly the same manner as in Example 1, except that the solidified hydrogel was frozen. The specific steps are as follows: Freezing treatment: The solidified single-network alginate hydrogel was placed in a constant temperature refrigerator at -20°C and frozen for 48 hours.

[0091] Test: After the freezing treatment, the hydrogel samples were subjected to uniaxial tensile test. The test results showed that the maximum tensile strength after freezing treatment was 35.73±2.70 kPa, which was significantly increased compared with the control group.

[0092] Example 3: Experimental Group 2 (immersion treatment only) The solidified single-network alginate hydrogel used in Experimental Group 2 was prepared in exactly the same manner as in Example 1, but the treatment method was to perform only immersion treatment. The specific steps are as follows: Immersion treatment: The solidified single-network alginate hydrogel sample was immersed in ultrapure water for 48 hours.

[0093] Test: The hydrogel samples after immersion treatment were subjected to uniaxial tensile test. The test results showed that the maximum tensile strength was 56.47±2.24 kPa, which was further improved compared with the control group.

[0094] Example 4: Experimental Group 3 (Freezing-immersion Co-treatment) The solidified single-network alginate hydrogel used in Experimental Group 3 was prepared in exactly the same manner as in Example 1, and was first subjected to a freezing treatment and then to an immersion treatment. The specific steps are as follows: Freezing treatment: The solidified single-network alginate hydrogel was placed in a constant temperature refrigerator at -20°C and frozen for 48 hours to obtain a frozen single-network alginate hydrogel.

[0095] Soaking treatment: The frozen single-network alginate hydrogel was taken out, placed at room temperature, and soaked in ultrapure water for 48 hours.

[0096] Test: The hydrogel samples after freeze-immersion synergistic treatment were subjected to uniaxial tensile test. The results showed that their maximum tensile strength was 186.11±8.97 kPa, which was significantly improved compared with the control group, experimental group 1 and experimental group 2.

[0097] The uniaxial tensile test data is shown in Table 1 below, which clearly shows the effects of different treatment methods on the maximum tensile strength of the hydrogel: Table 1 Uniaxial tensile test data As shown in Table 1, both freezing and soaking treatments can improve the tensile strength of hydrogels to a certain extent, but freezing-soaking synergistic treatment (experimental group 3) shows the most significant effect, with the maximum tensile strength increasing by an order of magnitude to 186.11 ± 8.97 kPa. This shows that freezing-soaking synergistic effect has an extremely excellent toughening effect.

[0098] The results of this comparative experiment show that the freezing-immersion synergistic treatment can significantly improve the tensile strength of alginate hydrogels. Compared with the freezing treatment or immersion treatment alone, the synergistic effect of freezing and immersion can better optimize the structure of the hydrogel and enhance its mechanical properties.

[0099] The above examples are only preferred embodiments of the present invention. Of course, those skilled in the art may make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should be considered to be within the scope of protection of the present invention.

[0100] It should be noted that the term "including" and its variations used in the embodiments of the present invention are open inclusions, that is, "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present invention are illustrative rather than restrictive. Those skilled in the art should understand that unless the context clearly indicates otherwise, it should be understood as "one or more".

[0101] The various steps described in the method implementation methods provided in the embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method implementation methods may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0102] The term "embodiment" in this specification refers to specific features, structures or characteristics described in conjunction with the embodiment that can be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. The various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments refer to each other. In particular, for the device, equipment, and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiment.

[0103] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a hydrogel based on freezing-immersion synergy, characterized in that: include: The sodium alginate aqueous solution and the soluble sodium salt are stirred and mixed to obtain an alginate precursor mixed solution; Adding a crosslinking agent solution dropwise to the alginate precursor mixed solution and stirring evenly to obtain a pre-gel solution; pouring the pre-gel solution into a mold for curing to generate a cured single-network alginate hydrogel; Freezing the solidified single-network alginate hydrogel in a low-temperature environment to generate a frozen single-network alginate hydrogel; The frozen single-network alginate hydrogel is placed at room temperature and then immersed in ultrapure water to generate a target single-network alginate hydrogel based on the synergistic effect of freezing and immersion.

2. The method according to claim 1, characterized in that Also includes: At room temperature, slowly adding sodium alginate into ultrapure water and stirring evenly to form a uniform and transparent sodium alginate aqueous solution; Among them, the mass fraction of sodium alginate is 1 wt. % to 4 wt. %, and the stirring time after the sodium alginate and the ultrapure water are mixed is 8 hours to 24 hours.

3. The method according to claim 1, characterized in that The stirring time of the sodium alginate aqueous solution and the soluble sodium salt is 5 to 30 minutes; Wherein, the soluble sodium salt is sodium pyrophosphate, sodium citrate, sodium oxalate, sodium carbonate or sodium sulfate, and the mass ratio of the soluble sodium salt to the cross-linking agent in the cross-linking agent solution is 0 wt. % to 40 wt. %.

4. The method according to claim 1, characterized in that: The stirring time when the crosslinking agent solution is added dropwise to the alginate precursor mixed solution and stirred evenly is 5 minutes to 30 minutes; The crosslinking agent in the crosslinking agent solution is anhydrous calcium sulfate or dihydrated calcium sulfate, and the mass ratio of the crosslinking agent to the sodium alginate is 10. wt. % to 95% wt. %.

5. The method according to claim 1, characterized in that After adding the crosslinking agent solution dropwise to the alginate precursor mixed solution and stirring evenly to obtain a pre-gel solution, the method further comprises: The pre-gel solution is subjected to a mixing and degassing treatment by a mixing and degassing machine to eliminate bubbles generated during the stirring process; The mixing time of the mixed degassing treatment is 30 seconds to 60 seconds, the degassing time of the mixed degassing treatment is 30 seconds to 60 seconds, and the number of times of the mixed degassing treatment is 1 to 3 cycles.

6. The method according to claim 1, characterized in that The pre-gel solution is poured into a mold for curing to generate a solidified single-network alginate hydrogel, comprising: Pour the pre-gel solution into the mold and let it stand at room temperature to eliminate bubbles generated during the solution transfer process; The mold is encapsulated by using a glass plate coated with a nano super-hydrophobic self-cleaning coating; The encapsulated mold is left to stand and solidify at room temperature to obtain the solidified single-network alginate hydrogel.

7. The method according to claim 6, characterized in that The pre-gel solution is poured into the mold and allowed to stand at room temperature to eliminate bubbles generated during the solution transfer process, and the standing time is 0.5 hours to 1 hour; when the encapsulated mold is allowed to stand and solidify at room temperature, the standing and solidification time is 12 hours to 48 hours.

8. The method according to claim 1, characterized in that The step of freezing the solidified single-network alginate hydrogel in a low-temperature environment to generate a frozen single-network alginate hydrogel comprises: The solidified single-network alginate hydrogel is placed in the low-temperature environment for freezing treatment for 12 hours to 72 hours to obtain the frozen single-network alginate hydrogel, wherein the temperature of the low-temperature environment is -10°C to -25°C.

9. The method according to claim 1, characterized in that: The soaking time of the soaking treatment is 12 hours to 72 hours.

10. A single-network alginate hydrogel, wherein the single-network alginate hydrogel is prepared according to the method for preparing a hydrogel based on freeze-immersion synergy according to any one of claims 1 to 9.

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