High-strength and high-toughness polymer hydrogel as well as preparation method and application thereof

Abstract

The invention relates to a high-strength and high-toughness high-molecular hydrogel and a preparation method and application thereof, the high-molecular hydrogel takes an amide monomer and an acrylic monomer as main monomers, and the compatibility among the monomers is controlled by adjusting the concentration of the monomers; the high-strength and high-toughness high-molecular hydrogel with a microphase separation structure is constructed through ultraviolet-initiated polymerization. Compared with the prior art, the high-molecular hydrogel prepared by the invention has excellent mechanical properties: the highest breaking strength can reach 18.33 MPa, the elongation at break is 690%, and the toughness reaches up to 47.87 MJ.m <-3 >; meanwhile, excellent puncture resistance (the maximum puncture force is 68.9 N, and the corresponding displacement is 79.8 mm) and impact energy absorption capacity (gt; 2.94 kJ * m <-1 >).

Description

Technical Field

[0001] The present invention relates to the field of polymer hydrogels, and in particular to a high-strength and high-toughness polymer hydrogel and a preparation method and application thereof. Background Art

[0002] With the rapid development of flexible electronics, unprecedented high requirements have been placed on high-performance, multifunctional advanced materials. Although traditional metals, ceramics and plastics have high strength, their large rigidity and hydrophobicity make it difficult to meet the application requirements of flexible materials and electronic devices. Polymer compounds provide a broad platform for the construction of flexible materials and devices due to their structural diversity, ease of functionalization and processing and molding. However, how to give the material mechanical strength, toughness and fatigue life comparable to hard materials while maintaining its softness and high water content remains a major challenge in this field. Polymer hydrogel has a unique three-dimensional cross-linked network structure that can absorb and retain a large amount of water. It can significantly swell in volume while maintaining its inherent shape without dissolving, making it have important application value and potential in the fields of biomedical engineering, flexible materials and devices.

[0003] While polymer hydrogels have garnered widespread attention in fields such as tissue engineering, drug delivery, and flexible electronics due to their high water content, softness, and good biocompatibility, they still face numerous challenges. First, conventional hydrogels have low mechanical strength and are unable to withstand high stresses or long-term dynamic loads. Second, they are prone to water loss or chemical degradation in their operating environments, resulting in insufficient stability. Furthermore, the preparation process often suffers from uneven network structures and inconsistent pore size distribution, which impacts performance consistency.

[0004] Therefore, the development of gel materials with high strength, high toughness and environmental adaptability has become an important direction in materials science. Studies have found that the lack of a strong energy dissipation mechanism inside polymer hydrogels is the main reason for their low mechanical properties. In addition, hydrogels usually have a low solid phase content, which further leads to weak mechanical properties. Currently, several methods have been developed to toughen polymer hydrogels by introducing new energy dissipation mechanisms, such as introducing multiple monomer networks or multiple cross-linking systems, introducing microphase separation, microcrystals, fibrils or fabrics and other higher-order structures. However, these methods still have the following problems: 1) The steps are cumbersome and the conditions are harsh. For example, the solvent of the polymerization system has significantly different compatibility with different monomers; 2) The synthesized polymer hydrogels have significant fatigue properties.

[0005] Chinese patent CN119409992A discloses a high-strength, low-swelling ion-conductive hydrogel, a preparation method, and its application, which belongs to the field of polymer hydrogel technology, including dissolving acrylic acid, acrylamide, phytic acid, and sodium carboxymethyl cellulose in deionized water, mixing evenly, and obtaining a precursor solution; removing bubbles from the precursor solution to obtain a precursor solution with bubbles removed; adding an initiator and a cross-linking agent to the precursor solution with bubbles removed, stirring until completely dissolved, and obtaining a prepolymer solution; free radical polymerization of the prepolymer solution under preset conditions to obtain a high-strength, low-swelling ion-conductive hydrogel. The preparation process of this scheme requires dissolving and mixing multiple components such as acrylic acid, acrylamide, phytic acid, and sodium carboxymethyl cellulose, and introduces additional phytic acid and sodium carboxymethyl cellulose, which not only makes the operation process more cumbersome, increases the difficulty of process control and the cost of raw materials, but also brings unnecessary complexity to the system. Secondly, in terms of core mechanical properties, the hydrogel generated by this scheme performs mediocrely, with a maximum breaking strength of only 2.05MPa and a maximum toughness of only 10.57MJ·m -3 Therefore, this comparative solution is difficult to meet the application requirements of high-performance flexible materials due to its complex process and significantly inferior mechanical properties.

[0006] Li Yaxin et al [1] The preparation and performance study of UV-curable PAA-PAM copolymer hydrogel are disclosed. Polyacrylic acid-acrylamide (PAA-PAM) copolymer hydrogel is prepared by UV-curing method using acrylic acid (AA) and acrylamide (AM) as monomers, N,N-methylenebisacrylamide (MBA) as cross-linker, and Irgaure2959 as initiator. This scheme has essential limitations in design concept, resulting in serious defects in its final performance. The core of this scheme is to add a large amount of small molecule propylene glycol (up to 60 vol%) to the traditional PAA-PAM copolymer hydrogel through physical blending to improve its performance. Although this method improves the material's elongation at break, temperature resistance and adhesion, this strategy of relying on external plasticizers also brings insurmountable disadvantages. First, its mechanical strength is extremely low. Under optimal conditions, the tensile strength is only 53.0 kPa (0.053 MPa), which is much lower than the strength without glycerol (183.5 kPa). This indicates that the performance improvement comes at the expense of key strength indicators. Second, the performance stability of this solution is questionable. The large amount of small molecule glycerol added is very likely to leach out during long-term use or in specific environments, which may lead to the degradation of the material's mechanical properties.

[0007] In summary, it is crucial to develop a simple, efficient, and universal method for preparing high-strength hydrogels.

[0008] References are as follows:

[0009] [1] Li Yaxin, Xie Junlong, Li Chenghao, et al. Preparation and properties of UV-curable PAA-PAM copolymer hydrogel[J]. China Plastics, 2025, 39(7): 22-27. DOI: 10.19491 / j.issn.1001-9278.2025.07.005. Summary of the Invention

[0010] The purpose of the present invention is to provide a high-strength, high-toughness polymer hydrogel and its preparation method and application. The present invention selects common amide monomers and acrylic monomers, selects appropriate monomer concentrations, and prepares high-strength hydrogels in a relatively short time through a simple process, thereby achieving simplicity, ease of use and high efficiency of the entire process.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] A method for preparing a high-strength and high-toughness polymer hydrogel, comprising the following specific steps:

[0013] S1, dissolving an amide monomer and an acrylic acid monomer in a lithium chloride solution in sequence, and mixing them evenly to obtain a monomer solution;

[0014] S2, adding polyethylene glycol diacrylate and a photoinitiator to the monomer solution obtained in step S1, and mixing them uniformly to obtain a hydrogel prepolymer solution;

[0015] S3. The hydrogel prepolymer solution obtained in step S2 is subjected to a photopolymerization reaction to obtain a polymer hydrogel.

[0016] Furthermore, in step S1, the amide monomer is selected from any one of acrylamide, N-isopropylacrylamide, N-propylacrylamide, N,N-dimethylacrylamide or N-hydroxyethylacrylamide.

[0017] Furthermore, in step S1, the acrylic monomer is selected from acrylic acid or methacrylic acid.

[0018] Furthermore, in step S1, the total concentration of the amide monomer and the acrylic acid monomer in the monomer solution is 2 to 20 mol L -1 , that is, the total monomer concentration is 2 to 20 mol L -1 ;

[0019] Among them, acrylic monomers account for 20% to 95%, and amide monomers account for 5% to 80%.

[0020] Furthermore, in step S1, the mass fraction of lithium chloride in the lithium chloride solution should be 5-50%.

[0021] Furthermore, in step S1, the mixing temperature is room temperature.

[0022] Furthermore, in step S2, the average molecular weight of the polyethylene glycol diacrylate should be 50 to 2000, and the concentration of the polyethylene glycol diacrylate should be 0.1‰ to 10% of the total monomer concentration.

[0023] Furthermore, in step S2, the photoinitiator is photoinitiator 2959, and the concentration of the photoinitiator is 0.1‰ to 10% of the total monomer concentration.

[0024] Furthermore, in step S3, the photopolymerization reaction is carried out under the conditions of a 360-370 nm ultraviolet light source.

[0025] The photopolymerization reaction time is 1 to 300 minutes, and the photopolymerization reaction temperature is room temperature.

[0026] As a preferred technical solution, the photopolymerization reaction is carried out under the condition of a 365nm ultraviolet light source.

[0027] The present invention also provides a high-strength and high-toughness polymer hydrogel, which is prepared by the above-mentioned preparation method.

[0028] Furthermore, the polymer hydrogel is a porous three-dimensional polymer network structure, and the interior of the three-dimensional polymer network has orderly arranged chain segments or nano-scale "microcrystal" regions.

[0029] As a preferred technical solution, the polymer hydrogel has excellent toughness, energy dissipation and strain strengthening behavior.

[0030] In addition, the present invention also provides an application of a high-strength, high-toughness polymer hydrogel in the preparation of flexible protective materials, energy absorption and buffering devices, and intelligent wearable sensors.

[0031] The principles of the present invention are as follows:

[0032] The core innovation of the present invention is that it abandons the idea of ​​unstable physical additives and uses a more advanced intrinsic enhancement strategy. The present invention controls the compatibility of the main monomers during the polymerization process by precisely regulating the concentration and ratio, thereby guiding the polymer network to form a unique microphase separation structure in situ, thereby giving the hydrogel ultra-high mechanical properties. At the same time, the present invention gives the hydrogel excellent puncture resistance and impact resistance through a unique network structure design, which are crucial for the reliability of the material in complex application environments. Therefore, the hydrogel prepared by the present invention not only achieves the perfect unity of ultra-high breaking strength (18.33MPa), excellent toughness (47.87MJ·m-3) and high elongation at break (690%), but also has excellent puncture resistance (maximum puncture force 68.9N) and impact energy absorption capacity (>2.94kJ·m-1) that the comparative scheme does not have at all, showing great potential and advancement as the next generation of high-performance flexible materials.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The polymer hydrogel provided by the present invention uses amide monomers and acrylic monomers as main monomers, controls the compatibility between monomers by adjusting the monomer concentration, and constructs a high-strength, high-toughness polymer hydrogel with a microphase separation structure through ultraviolet light-induced polymerization.

[0035] (2) The polymer hydrogel prepared by the present invention has excellent mechanical properties: the breaking strength can reach up to 18.33 MPa, the breaking elongation is 690%, and the toughness is up to 47.87 MJ·m -3 At the same time, it exhibits excellent puncture resistance (maximum puncture force 68.9N, corresponding displacement 79.8mm) and impact energy absorption capacity (>2.94kJ·m -1 ).

[0036] (3) The polymer hydrogel provided by the present invention exhibits a significant strain enhancement effect during the cyclic stretching-unloading process, wherein its maximum stress gradually increases with the increase in the number of cycles, and its breaking strength significantly increases with the increase in the number of stretching cycles.

[0037] (4) The polymer hydrogel provided by the present invention has good puncture resistance, can withstand a maximum puncture force of 68.9N and a puncture displacement of 79.8mm, and can absorb impact energy exceeding 2.94kJ / m.

[0038] (5) The polymer hydrogel and its preparation method provided by the present invention have the advantages of simple process, strong adjustability, and excellent performance, and are suitable for flexible protective materials, energy absorption and buffering devices, smart wearable sensors and other fields.

[0039] (6) The present invention adopts a simple photopolymerization method and uses common monomers such as acrylamide and acrylic acid to synthesize high-performance hydrogels. Compared with traditional synthesis methods, this method demonstrates the advantages of universal monomer selection, simplicity and speed of the synthesis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the preparation process of the high-strength and high-toughness polymer hydrogel in the present invention.

[0041] Figure 2 This is an optical photograph of the high-strength and high-toughness polymer hydrogel prepared in Example 1.

[0042] Figure 3 These are low-magnification scanning electron micrographs of the front and cross-sections of the high-strength, high-toughness polymer hydrogel prepared in Example 1 before and after swelling with water for 24 hours, wherein a) is a front-facing scanning electron micrograph of the untreated hydrogel, b) is a cross-sectional scanning electron micrograph of the untreated hydrogel, c) is a front-facing scanning electron micrograph of the hydrogel after swelling for 24 hours and freeze-drying, and d) is a cross-sectional scanning electron micrograph of the hydrogel after swelling for 24 hours and freeze-drying.

[0043] Figure 4 These are optical photographs of the high-strength, high-toughness polymer hydrogel prepared in Example 1 lifting a 3 kg weight from different angles (0°, 60°, 90° and 120°).

[0044] Figure 5 These are the stress-strain curves of the high-strength, high-toughness polymer hydrogels prepared in Examples 1 to 7 at different total monomer concentrations.

[0045] Figure 6 These are the stress-strain curves of the high-strength, high-toughness polymer hydrogels prepared in Examples 1 and 8-11 at different monomer proportions.

[0046] Figure 7 The radar chart is a comparison of the mechanical properties of Example 1 and Comparative Examples 1-2.

[0047] Figure 8 This is an optical photograph of the high-strength, high-toughness polymer hydrogel prepared in Example 1 during the stretching process.

[0048] Figure 9 These are optical photographs of the strain recovery of the high-strength, high-toughness polymer hydrogel prepared in Example 1 before and after stretching.

[0049] Figure 10 These are the puncture strain result curves of the high-strength and high-toughness polymer hydrogels prepared in Examples 1, 4, and 5.

[0050] Figure 11 Schematic diagram of the impact resistance platform and impact resistance results of the high-strength and high-toughness polymer hydrogel prepared in Example 1.

[0051] Figure 12 Comparison of the mechanical properties of the high-strength, high-toughness polymer hydrogel prepared in Example 5 before and after tensile strain recovery.

[0052] Figure 13 This is the strain enhancement effect of the high-strength and high-toughness polymer hydrogel prepared in Example 5.

[0053] Figure 14 These are low to high magnification scanning electron microscope photographs of the high-strength, high-toughness polymer hydrogel prepared in Example 1 after tensile strain cycling, wherein a) is a low-magnification (500x) scanning electron microscope photograph of the hydrogel after stretching cycle treatment, b) is a medium-magnification (5000x) scanning electron microscope photograph of the hydrogel after stretching cycle treatment, c) is a high-magnification (20000x) scanning electron microscope photograph of a local part of the hydrogel after stretching cycle treatment, and d) is an extremely high-magnification (100000x) scanning electron microscope photograph of a local part of the hydrogel after stretching cycle treatment.

[0054] Figure 15 These are the relevant infrared spectroscopy results of the high-strength and high-toughness polymer hydrogel prepared in Example 1.

[0055] Figure 16 These are the relevant X-ray diffraction technology results of the high-strength and high-toughness polymer hydrogel prepared in Example 1.

[0056] Figure 17 These are the relevant small-angle X-ray scattering results of the high-strength and high-toughness polymer hydrogels prepared in Example 1 and Example 5 before and after stretching.

[0057] Figure 18 The relevant phase transition temperatures and thermal effects (DSC) of the high-strength, high-toughness polymer hydrogels prepared in Examples 1 and 5 before and after stretching. DETAILED DESCRIPTION

[0058] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0059] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0060] The following describes some embodiments of the present invention in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0061] Example 1

[0062] See also Figure 1 This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel, and the specific steps are as follows:

[0063] (1) Dissolve acrylamide solid (AM) and acrylic acid (AA) in a 10% by mass LiCl solution and mix them evenly at room temperature to prepare a total monomer concentration of 12 mol L -1 , a monomer solution with 15% acrylamide and 85% acrylic acid.

[0064] (2) Adding polyethylene glycol diacrylate with an average molecular weight of 600 to the monomer solution obtained in step (1) at a concentration of 0.5‰ of the total monomer concentration, and then adding photoinitiator 2959 at a concentration of 1.0‰ of the total monomer concentration to prepare a hydrogel prepolymer solution.

[0065] (3) The hydrogel prepolymer obtained in step (2) is filled into a light-transmitting mold, and a photopolymerization reaction is carried out at room temperature using a 365 nm ultraviolet light source. The reaction time is about 30 minutes to obtain a high-strength, high-toughness polymer hydrogel material.

[0066] Example 2

[0067] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. In addition to the total monomer concentration of the monomer solution in step (1) being 4 mol L -1 , the remaining steps are the same as in Example 1.

[0068] Example 3

[0069] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. In addition to the total monomer concentration of the monomer solution in step (1) being 6 mol L -1 , the remaining steps are the same as in Example 1.

[0070] Example 4

[0071] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. In addition to the total monomer concentration of the monomer solution in step (1) being 8 mol L -1 , the remaining steps are the same as in Example 1.

[0072] Example 5

[0073] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. In addition to the total monomer concentration of the monomer solution in step (1) being 10 mol L -1 , the remaining steps are the same as those in Example 1.

[0074] Example 6

[0075] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. In addition to the total monomer concentration of the monomer solution in step (1) being 11 mol L -1 , the remaining steps are the same as those in Example 1.

[0076] Example 7

[0077] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. In addition to the total monomer concentration of the monomer solution in step (1) being 13 mol L -1 , the remaining steps are the same as those in Example 1.

[0078] Example 8

[0079] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. Except that in step (1), the proportion of acrylamide in the monomer solution is 20% and the proportion of acrylic acid is 80%, the remaining steps are the same as those in Example 1.

[0080] Example 9

[0081] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. Except that in step (1), the proportion of acrylamide in the monomer solution is 25% and the proportion of acrylic acid is 75%, the remaining steps are the same as those in Example 1.

[0082] Example 10

[0083] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. Except that in step (1), the proportion of acrylamide in the monomer solution is 30% and the proportion of acrylic acid is 70%, the remaining steps are the same as those in Example 1.

[0084] Example 11

[0085] This embodiment provides a method for preparing a high-strength and high-toughness polymer hydrogel. Except that in step (1), the proportion of acrylamide in the monomer solution is 35% and the proportion of acrylic acid is 65%, the remaining steps are the same as those in Example 1.

[0086] Comparative Example 1

[0087] This comparative example provides a method for preparing a hydrogel, and the specific steps are as follows:

[0088] (1) Dissolve 250 mg of citric acid in 10 mL of deionized water, then add 0.5 mL of ethylenediamine. After thorough stirring, transfer the solution to a 20 mL polytetrafluoroethylene reactor and react in an oven at 180 °C for 6 hours. After cooling to room temperature, dialyze the product in deionized water for 24 hours using a dialysis bag. Finally, dilute the resulting carbon dot solution to 100 μg mL -1 , and stored in a 4°C refrigerator until use.

[0089] (2) Dissolve 4 g of acrylamide in 20 mL of deionized water and stir thoroughly at room temperature for 60 minutes. Then, add 8 mg of N,N-methylenebisacrylamide and 40 mg of ammonium persulfate in sequence and stir until completely dissolved. Pour the resulting solution into a Petri dish and react in an oven at 75°C for 1.5 hours to obtain a polyacrylamide / sodium alginate hydrogel.

[0090] (3) The acrylamide / sodium alginate hydrogel prepared in step (2) was stretched to 150% and then dried for 24 hours. -1 Finally, the hydrogel after soaking was immersed in the carbon dot solution prepared in step (1) for 2 hours, and then the excess carbon dots were washed away with deionized water to successfully obtain a strong hydrogel.

[0091] Comparative Example 2

[0092] This comparative example provides a method for preparing a hydrogel, and the specific steps are as follows:

[0093] (1) 0.3 g of carboxymethyl cellulose was added to 10 ml of deionized water and stirred magnetically for 4 hours to allow it to swell completely. Subsequently, 0.15 mol L -1 Add zinc chloride and continue stirring for 2 hours to form a physically cross-linked carboxymethyl cellulose gel.

[0094] (2) N-vinyl-2-pyrrolidone (NVP) and acrylic acid (AA) were mixed at a molar ratio of 1:1 to prepare an NVP-AA solution.

[0095] (3) The carboxymethyl cellulose gel prepared in step (1) was dissolved in the NVP-AA solution prepared in step (2), and 2% by mass of a photoinitiator, TPO, was added. Finally, a mixed solution having a carboxymethyl cellulose to NVP-AA mass ratio of 1000:8 and a total water content of 40% by mass was prepared as a hydrogel precursor solution.

[0096] (4) The hydrogel precursor solution prepared in step (3) was injected into the transparent mold using a wavelength of 405 nm and a power density of about 300 mW cm-2 The ultraviolet light source was irradiated for 500 seconds to complete the photopolymerization reaction and obtain the final high-toughness self-healing hydrogel.

[0097] The specific test results of the polymer hydrogels prepared in Examples 1 to 10 are as follows:

[0098] Figure 2 This is an optical photograph of the polymer hydrogel prepared in Example 1. The polymer hydrogel appears colorless and transparent in a macroscopic view.

[0099] Figure 3 Scanning electron microscope (SEM) images of the polymer hydrogel prepared in Example 1 before and after swelling are shown. Before swelling, the hydrogel exhibits a uniform and regular microscopic morphology on both its surface and cross-section. After 24 hours of swelling, the surface layer transforms into a porous structure with pore sizes of 5-10 μm.

[0100] Figure 4 The polymer hydrogel prepared in Example 1 was able to withstand and stably load a standard heavy weight with a mass of 3 kg at different loading angles (including 0°, 60°, 90° and 120°) without obvious damage, which intuitively proves that the hydrogel prepared in this example has excellent mechanical bearing properties.

[0101] The mechanical test results of the polymer hydrogels prepared in Examples 1 to 7 are as follows: Figure 5 When the total monomer concentration is at a low level (<10 mol L- 1 ), the mechanical properties of the hydrogel (such as tensile strength and Young's modulus) increase relatively slowly with the increase of concentration, while when the total monomer concentration exceeds 10 mol L- 1 After that, the mechanical properties of the hydrogel increased rapidly. When the total monomer concentration was 12 molL- 1 The comprehensive mechanical properties of the polymer hydrogel reached a peak when the monomer concentration was 100%, and then the fracture strength and toughness of the hydrogel decreased. This is mainly related to the changes in the microstructure within the gel network. Higher monomer concentrations help form a denser and more complete polymer network, in which the density of the hard phase structure that contributes to strength increases rapidly with the increase in monomer concentration, thus giving the material stronger resistance to deformation.

[0102] The mechanical test results of the polymer hydrogels prepared in Example 1 and Examples 8 to 11 are as follows: Figure 6 , the total monomer concentration is 12 mol L- 1The influence of the molar ratio of the comonomer acrylamide (AM) to acrylic acid (AA) on the mechanical properties of the hydrogels of this example was investigated. The results showed that as the proportion of acrylamide monomer gradually increased, the breaking strength of the prepared hydrogels remained at a high level and did not fluctuate greatly; however, the maximum tensile length (i.e. breaking elongation) gradually decreased with the increase of the acrylamide content. This phenomenon is mainly due to the introduction of acrylamide segments increasing the rigidity of the gel network, and relatively reducing the proportion of flexible segments (such as acrylic acid segments or the relatively loose network structure formed thereby) that impart high ductility to the material, thereby affecting the overall toughness and ultimate tensile capacity of the material. Notably, when the proportion of acrylamide monomer is 15%, the polymer hydrogel of this example exhibits the optimal combination of comprehensive mechanical properties, with a breaking strength of up to 18.33 MPa, a breaking elongation of up to 690%, and a toughness (characterized by breaking energy) of up to 47.87 MJ·m -3 .

[0103] The comparison of the mechanical test results of the polymer hydrogels prepared in Example 1 and Comparative Examples 1-2 is shown in Figure 7 , and the polymer hydrogel of this example has a significant performance advantage, with a breaking strength of up to nearly 18.33 MPa, a toughness of up to 47.87 MJ·m -3 , and a breaking elongation of up to nearly 690%, achieving the perfect unity of high strength, high toughness and high elasticity. In comparison, the mechanical performance indicators of the hydrogels prepared in Comparative Example 1 and Comparative Example 2 (dashed area) are all at a very low level, with a breaking strength of less than 5 MPa and a toughness of less than 10 MJ·m -3 . In summary, the preparation method used in the comparative examples not only has a complicated process, but also the performance of the final product is not satisfactory, which cannot meet the requirements of high-performance applications. The preparation method proposed in Example 1 of the present application successfully prepares a high-performance hydrogel with comprehensive mechanical properties far superior to the comparative examples, showing a huge technical advantage.

[0104] The optical photographs of the high-strength, high-toughness polymer hydrogel prepared in Example 1 during the stretching process are shown in Figure 8 , and the macroscopic appearance of the polymer hydrogel of this example gradually changes from colorless and transparent to opaque white during the uniaxial stretching process as the stretching ratio gradually increases. This stretching-induced color change phenomenon may be related to the intensification of the internal phase separation behavior of the hydrogel under the action of the stretching strain, and the microphase separation leads to the change of light scattering, thereby presenting the stress whitening phenomenon in the macroscopic appearance of the gel from colorless and transparent to white. When the stretching stress is removed, the white opaque appearance gradually returns to the initial colorless and transparent state Figure 9), this stress whitening phenomenon and its recovery characteristics may be related to the deorientation or reorganization (restructuring) process of the microcrystalline phase or oriented structure formed inside the hydrogel under stress after the stress is removed.

[0105] The puncture resistance test of the polymer hydrogels prepared in Example 1, Example 4 and Example 5 is as follows: Figure 10 As shown, when the total monomer concentration reaches 12 mol L -1 When the mechanical properties and flexibility of the polymer hydrogel reach a relative balance, the maximum puncture resistance of the polymer hydrogel is 68.9N, and the corresponding displacement of the puncture needle is 79.8mm. Figure 11 As shown in the impact resistance test, the polymer hydrogel prepared in Example 1 can absorb an impact energy exceeding 2.94 kJ / m. These results demonstrate that the prepared polymer hydrogel not only has excellent tensile properties but also has good puncture and impact resistance, demonstrating its potential as a structural or protective material.

[0106] Comparison of mechanical properties of the polymer hydrogel prepared in Example 5 before and after tensile strain recovery Figure 12 As shown in the figure, after 10 cycles of stretching to 400%, the maximum breaking strength of the polymer hydrogel increased significantly from the initial 2.83MPa to 6.16MPa, while the breaking elongation only changed slightly, indicating that the polymer hydrogel has a significant strain enhancement effect. Figure 13 As shown, with the gradual increase in the number of cycles, the stress value of the polymer hydrogel prepared in Example 5 under a specific strain also gradually increases, which indicates that its internal microstructure undergoes favorable adjustments under the action of mechanical stress, thereby improving its mechanical properties.

[0107] The SEM photos of the polymer hydrogel prepared in Example 1 after stretching cycle and recovery are as follows: Figure 14 As shown in the figure, after the stretching cycle and recovery, obvious wrinkle structures are formed on the surface of the hydrogel sample. The largest wrinkles are about 10 μm. Nanoscale wrinkle structures are also formed on the surface of the large wrinkles. These fine wrinkles (50 nm) are

[0108] The Fourier transform infrared spectroscopy (FTIR) results of the polymer hydrogel prepared in Example 1 are as follows: Figure 15 As shown, at about 3500cm -1 to 2800cm -1 The broad absorption peak in the wavenumber region is attributed to the OH stretching vibration, indicating that there are a large number of hydrogen bond interactions inside the hydrogel. The X-ray diffraction (XRD) results of the polymer hydrogel prepared in Example 1 are as follows: Figure 16As shown in the figure, the polymer hydrogel has an obvious broad diffraction peak at a position of about 22° in 2θ. The position and morphology of the diffraction peak are different from the typical diffraction characteristics of conventional polyacrylic acid or polyacrylamide hydrogels. The existence of this structure reflects that there is a certain degree of ordered arrangement of chain segments or nano-scale "microcrystalline" regions inside the hydrogel, rather than a completely amorphous state. These dense regions or ordered structures are one of the key factors for the hydrogel to exhibit excellent mechanical properties.

[0109] The small angle X-ray scattering results of the polymer hydrogels prepared in Example 1 and Example 5 are as follows: Figure 17 As shown, the polymer hydrogel sample has a scattering vector q value of A distinct diffraction peak appears at the position of the α-Hydrogen molecule, further demonstrating that the polymer hydrogel has formed a regular microcrystalline structure or periodic nanoscale ordered domains within it. For strain-enhanced hydrogel samples, the intensity of the corresponding diffraction peak in the SAXS spectrum also increases, indicating that stress induction can effectively promote the formation of microcrystalline structures within the hydrogel or increase the content and regularity of its ordered structure.

[0110] The DSC test results of the polymer hydrogels prepared in Example 1 and Example 5 are as follows: Figure 18 As shown. As can be seen from the figure, all hydrogel samples showed a broad endothermic peak in the temperature range of about 90°C-140°C, which is attributed to the melting or dissociation of the physical cross-linked network or microcrystalline structure inside the hydrogel, proving that an ordered microstructure is formed inside the hydrogel. For the hydrogel samples of Example 1 and Example 5 that were recovered after stretching treatment, the corresponding endothermic peak area in their DSC spectra increased significantly. This shows that the stress-induced effect during the stretching process can effectively promote the regular arrangement of polymer chain segments inside the hydrogel, thereby increasing the content of its microcrystalline structure or the regularity of its ordered structure.

[0111] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength and high-toughness polymer hydrogel, characterized in that: The specific steps are as follows: S1, dissolving an amide monomer and an acrylic acid monomer in a lithium chloride solution in sequence, and mixing them evenly to obtain a monomer solution; S2, adding polyethylene glycol diacrylate and a photoinitiator to the monomer solution obtained in step S1, and mixing them uniformly to obtain a hydrogel prepolymer solution; S3. The hydrogel prepolymer solution obtained in step S2 is subjected to a photopolymerization reaction to obtain a polymer hydrogel.

2. The method for preparing a high-strength and high-toughness polymer hydrogel according to claim 1, characterized in that: In step S1, the amide monomer is selected from any one of acrylamide, N-isopropylacrylamide, N-propylacrylamide, N,N-dimethylacrylamide or N-hydroxyethylacrylamide; In step S1, the acrylic monomer is selected from acrylic acid or methacrylic acid.

3. The method for preparing a high-strength and high-toughness polymer hydrogel according to claim 1, characterized in that: In step S1, the total concentration of the amide monomer and the acrylic acid monomer in the monomer solution is 2 to 20 mol L -1 , that is, the total monomer concentration is 2 to 20 mol L -1 ; Among them, acrylic monomers account for 20% to 95%, and amide monomers account for 5% to 80%.

4. The method for preparing a high-strength and high-toughness polymer hydrogel according to claim 1, characterized in that: In step S1, the mass fraction of lithium chloride in the lithium chloride solution should be 5-50%.

5. The method for preparing a high-strength and high-toughness polymer hydrogel according to claim 1, characterized in that: In step S2, the average molecular weight of the polyethylene glycol diacrylate should be 50 to 2000, and the concentration of the polyethylene glycol diacrylate should be 0.1‰ to 10% of the total monomer concentration.

6. The method for preparing a high-strength and high-toughness polymer hydrogel according to claim 1, characterized in that: In step S2, the photoinitiator is photoinitiator 2959, and the concentration of the photoinitiator is 0.1‰ to 10% of the total monomer concentration.

7. The method for preparing a high-strength and high-toughness polymer hydrogel according to claim 1, characterized in that: In step S3, the photopolymerization reaction is carried out under the conditions of a 360-370 nm ultraviolet light source. The photopolymerization reaction time is 1 to 300 minutes, and the photopolymerization reaction temperature is room temperature.

8. A high-strength, high-toughness polymer hydrogel, characterized in that: The polymer hydrogel is prepared by the preparation method described in any one of claims 1-7.

9. The high-strength, high-toughness polymer hydrogel according to claim 8, characterized in that: The polymer hydrogel is a porous three-dimensional polymer network structure, and the interior of the three-dimensional polymer network has orderly arranged chain segments or nano-scale "microcrystal" regions.

10. Use of the high-strength, high-toughness polymer hydrogel according to claim 8 or claim 9 in the preparation of flexible protective materials, energy absorption and buffering devices, and intelligent wearable sensor devices.

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