A high-strength, high-toughness polymer hydrogel, its preparation method and application

Abstract

This invention relates to a high-strength, high-toughness polymer hydrogel, its preparation method, and its applications. The polymer hydrogel primarily uses amide and acrylic monomers. The compatibility between monomers is controlled by adjusting their concentrations. Ultraviolet light-initiated polymerization is used to construct a high-strength, high-toughness polymer hydrogel with a microphase-separated structure. Compared with existing technologies, the polymer hydrogel prepared by this invention exhibits superior mechanical properties: a maximum tensile strength of 18.33 MPa, an elongation at break of 690%, and a toughness as high as 47.87 MJ·m. ‑3 It also exhibits excellent puncture resistance (maximum puncture force 68.9 N, corresponding displacement 79.8 mm) and impact energy absorption capacity (>2.94 kJ·m). ‑1 ).

Description

Technical Field

[0001] This invention relates to the field of polymer hydrogels, and in particular to a high-strength, high-toughness polymer hydrogel, its preparation method, and its applications. Background Technology

[0002] With the rapid development of flexible electronics, unprecedented demands are being placed on high-performance, multifunctional advanced materials. While traditional metals, ceramics, and plastics offer high strength, their significant rigidity and hydrophobicity make them unsuitable for the applications of flexible materials and electronic devices. Polymer compounds, due to their structural diversity, ease of functionalization, and processing, provide a broad platform for constructing flexible materials and devices. However, maintaining the material's softness and high water content while endowing it with mechanical strength, toughness, and fatigue life comparable to rigid materials remains a major challenge in this field. Polymer hydrogels possess a unique three-dimensional cross-linked network structure, capable of absorbing and retaining large amounts of water. They swell significantly in volume while maintaining their inherent shape without dissolving, making them significant in application value and potential in biomedical engineering, flexible materials, and devices.

[0003] Despite the widespread interest in tissue engineering, drug delivery, and flexible electronics due to their high water content, flexibility, and good biocompatibility, polymer hydrogels still face numerous challenges. First, traditional hydrogels have low mechanical strength, making them unable to withstand high stress or long-term dynamic loads. Second, they are prone to water loss or chemical degradation in the application environment, leading to insufficient stability. Furthermore, the preparation process often involves issues such as uneven network structure and inconsistent pore size distribution, affecting performance consistency.

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

[0005] Chinese patent CN119409992A discloses a high-strength, tough, low-swelling ion-conducting hydrogel, its preparation method, and its application, belonging to the field of polymer hydrogel technology. The method includes dissolving acrylic acid, acrylamide, phytic acid, and sodium carboxymethyl cellulose in deionized water and mixing them evenly to obtain a precursor solution; removing air bubbles from the precursor solution to obtain a de-bubbled precursor solution; adding an initiator and a crosslinking agent to the de-bubbled precursor solution and stirring until completely dissolved to obtain a prepolymer; and then performing free radical polymerization of the prepolymer under preset conditions to obtain the high-strength, tough, low-swelling ion-conducting hydrogel. This method requires dissolving and mixing multiple components such as acrylic acid, acrylamide, phytic acid, and sodium carboxymethyl cellulose, introducing additional phytic acid and sodium carboxymethyl cellulose. This not only makes the operation more cumbersome, increases the difficulty of process control and raw material costs, but also introduces unnecessary complexity into the system. Furthermore, in terms of core mechanical properties, the hydrogel produced by this method exhibits mediocre performance, with a maximum tensile strength of only 2.05 MPa and a maximum toughness of only 10.57 MJ·m. -3 Therefore, this comparative approach, due to its complex process and significantly inferior mechanical properties, is unable to meet the application requirements of high-performance flexible materials.

[0006] Li Yaxin et al. [1] The preparation and performance study of UV-curable PAA-PAM copolymer hydrogels were disclosed. Using acrylic acid (AA) and acrylamide (AM) as monomers, N,N-methylenebisacrylamide (MBA) as a crosslinking agent, and Irgaure 2959 as an initiator, polyacrylic acid-acrylamide (PAA-PAM) copolymer hydrogels were prepared via UV curing. This approach has inherent limitations in its design concept, leading to serious defects in its final performance. The core of this approach lies in adding a large amount of low-molecule glycerol (up to 60 vol%) to the traditional PAA-PAM copolymer hydrogel through physical blending to improve its properties. Although this method improves the material's elongation at break, temperature resistance, and adhesion, this strategy relying on added plasticizers also brings insurmountable drawbacks. First, its mechanical strength is extremely low. Under optimal conditions, the tensile strength is only 53.0 kPa (0.053 MPa), which is far lower than its strength without the addition of glycerol (183.5 kPa). This indicates that the performance improvement comes at the cost of sacrificing key strength indicators. Second, the performance stability of this solution is questionable. The large amount of small-molecule glycerol added is prone to leaching during long-term use or in specific environments, which may lead to a decline in the mechanical properties of the material.

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

[0008] The references are as follows:

[0009] [1] Li Yaxin, Xie Junlong, Li Chenghao, et al. Preparation and performance study of UV-cured 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 this invention is to provide a high-strength, high-toughness polymer hydrogel, its preparation method, and its application. This invention selects common amide monomers and acrylic monomers, chooses appropriate monomer concentrations, and prepares a high-strength hydrogel in a short time through a simple process, achieving simplicity, ease of use, and high efficiency throughout the process.

[0011] The objective of this invention can be achieved through the following technical solutions:

[0012] A method for preparing a high-strength, high-toughness polymer hydrogel, the specific steps of which are as follows:

[0013] S1. Dissolve amide monomers and acrylic monomers sequentially in lithium chloride solution, mix thoroughly to obtain monomer solution;

[0014] S2. Add polyethylene glycol diacrylate and photoinitiator to the monomer solution obtained in step S1, mix well to obtain hydrogel prepolymer solution;

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

[0016] Further, 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, etc.

[0018] Further, in step S1, the total concentration of amide monomers and acrylic monomers in the monomer solution is 2–20 mol / L. -1 That is, the total monomer concentration is 2-20 mol / L. -1 ;

[0019] Of these, 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% to 50%.

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

[0022] Further, 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] Further, 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 performed using an ultraviolet light source of 360–370 nm.

[0025] The photopolymerization reaction takes 1 to 300 minutes and is carried out at room temperature.

[0026] As a preferred technical solution, the photopolymerization reaction is performed using a 365nm ultraviolet light source.

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

[0028] Furthermore, the polymer hydrogel has a porous three-dimensional polymer network structure, and the interior of the three-dimensional polymer network has ordered chain segments or nanoscale "microcrystal" regions.

[0029] As a preferred technical solution, the polymer hydrogel exhibits 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 buffer devices, and smart wearable sensors.

[0031] The principle of this invention is as follows:

[0032] The core innovation of this invention lies in abandoning the approach of unstable physical additives and instead employing a more advanced intrinsic enhancement strategy. This invention precisely controls the concentration and ratio of the main monomers to manage their compatibility during polymerization, thereby guiding the polymer network to form a unique microphase separation structure in situ, thus endowing the hydrogel with ultra-high mechanical properties. Simultaneously, through a unique network structure design, this invention endows the hydrogel with excellent puncture and impact resistance, properties crucial for the reliability of materials in complex application environments. Therefore, the hydrogel prepared by this invention not only achieves a perfect balance of ultra-high tensile strength (18.33 MPa), excellent toughness (47.87 MJ·m⁻³), and high elongation at break (690%), but also possesses superior puncture resistance (maximum puncture force 68.9 N) and impact energy absorption capacity (>2.94 kJ·m⁻¹), which are completely lacking in comparative solutions, demonstrating its enormous potential and advanced nature as a next-generation high-performance flexible material.

[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 the main monomers. The compatibility between monomers is controlled by adjusting the monomer concentration. High strength and high toughness polymer hydrogel with microphase separation structure is constructed by ultraviolet light-induced polymerization.

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

[0036] (3) The polymer hydrogel provided by the present invention exhibits a significant strain enhancement effect during the cyclic stretching-unloading process. Its maximum stress gradually increases with the number of cycles, and its fracture strength increases significantly with 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 of more than 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 buffer devices, smart wearable sensors and other fields.

[0039] (6) This invention uses a simple photopolymerization method and common monomers such as acrylamide and acrylic acid to synthesize high-performance hydrogels. Compared with traditional synthesis methods, this method demonstrates advantages such as the universality of monomer selection and the simplicity and speed of the synthesis process. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the preparation process of the high-strength, high-toughness polymer hydrogel in this invention.

[0041] Figure 2 An optical photograph of the high-strength, high-toughness polymer hydrogel prepared in Example 1.

[0042] Figure 3 The images shown are low-magnification scanning electron microscope (SEM) images 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. Among them, a) is a front SEM image of the untreated hydrogel, b) is a cross-sectional SEM image of the untreated hydrogel, c) is a front SEM image of the hydrogel after swelling for 24 hours and freeze-drying, and d) is a cross-sectional SEM image of the hydrogel after swelling for 24 hours and freeze-drying.

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

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

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

[0046] Figure 7 Radar graphs showing the mechanical properties of Example 1 and Comparative Examples 1-2.

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

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

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

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

[0051] Figure 12 This is a 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 refers to the strain-enhancing effect of the high-strength, high-toughness polymer hydrogel prepared in Example 5.

[0053] Figure 14 The images shown are low- to high-magnification scanning electron microscope (SEM) images of the high-strength, high-toughness polymer hydrogel prepared in Example 1 after tensile strain cycling. Specifically, a) is a low-magnification (500x) SEM image of the hydrogel after tensile cycling; b) is a medium-magnification (5000x) SEM image of the hydrogel after tensile cycling; c) is a local high-magnification (20000x) SEM image of the hydrogel after tensile cycling; and d) is a local extremely high-magnification (100000x) SEM image of the hydrogel after tensile cycling.

[0054] Figure 15 The infrared spectra of the high-strength, high-toughness polymer hydrogel prepared in Example 1 are shown.

[0055] Figure 16 The results of X-ray diffraction are shown for the high-strength, high-toughness polymer hydrogel prepared in Example 1.

[0056] Figure 17 The results of small-angle X-ray scattering (SAXS) of the high-strength, high-toughness polymer hydrogels prepared in Examples 1 and 5 before and after stretching are shown.

[0057] Figure 18 The results of related phase transition temperature and thermal effect (DSC) of the high-strength, high-toughness polymer hydrogels prepared in Examples 1 and 5 before and after stretching. Detailed Implementation

[0058] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

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

[0060] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features described herein can be combined with each other.

[0061] Example 1

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

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

[0064] (2) Add polyethylene glycol diacrylate with an average molecular weight of 600 at a total monomer concentration of 0.5‰ to the monomer solution obtained in step (1), and then add photoinitiator 2959 at a total monomer concentration of 1.0‰ 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 365nm ultraviolet light source. The reaction time is about 30 minutes, and a high-strength, high-toughness polymer hydrogel material is obtained.

[0066] Example 2

[0067] This embodiment provides a method for preparing a high-strength, high-toughness polymer hydrogel, except that the total monomer concentration of the monomer solution in step (1) is 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, high-toughness polymer hydrogel, except that the total monomer concentration of the monomer solution in step (1) is 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, high-toughness polymer hydrogel, except that the total monomer concentration of the monomer solution in step (1) is 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, high-toughness polymer hydrogel, except that the total monomer concentration of the monomer solution in step (1) is 10 mol / L. -1 The remaining steps are the same as in Example 1.

[0074] Example 6

[0075] This embodiment provides a method for preparing a high-strength, high-toughness polymer hydrogel, except that the total monomer concentration of the monomer solution in step (1) is 11 mol / L. -1 The remaining steps are the same as in Example 1.

[0076] Example 7

[0077] This embodiment provides a method for preparing a high-strength, high-toughness polymer hydrogel, except that the total monomer concentration of the monomer solution in step (1) is 13 mol / L. -1 The remaining steps are the same as in Example 1.

[0078] Example 8

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

[0080] Example 9

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

[0082] Example 10

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

[0084] Example 11

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

[0086] Comparative Example 1

[0087] This comparative example provides a method for preparing a hydrogel, the specific steps of which 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 through a dialysis bag into deionized water for 24 hours. Finally, dilute the resulting carbon dot solution to 100 μg / mL. -1 Store in a 4°C refrigerator for later use.

[0089] (2) Dissolve 4g of acrylamide in 20mL of deionized water and stir thoroughly for 60 minutes at room temperature. Then, add 8mg of N,N-methylenebisacrylamide and 40mg 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℃ for 1.5 hours to obtain 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. Subsequently, the dried hydrogel was immersed in 1 mol L... -1 The hydrogel was immersed in a solution of zirconium oxychloride octahydrate for 2 hours. Finally, the soaked hydrogel 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 and tough hydrogel.

[0091] Comparative Example 2

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

[0093] (1) Add 0.3g of carboxymethyl cellulose to 10ml of deionized water and stir magnetically for 4 hours until it swells completely. Then, add 0.15mol L to the solution. -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) are mixed in a 1:1 molar ratio to prepare an NVP-AA solution.

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

[0096] (4) Inject the hydrogel precursor solution finally prepared in step (3) into a light-transmitting mold, using a wavelength of 405 nm and a power density of approximately 300 mW / cm².-2 Irradiation with ultraviolet light for 500 seconds completes the photopolymerization reaction, resulting in a high-toughness self-healing hydrogel.

[0097] The specific test results of the polymer hydrogels prepared in Examples 1-10 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 on a macroscopic scale.

[0099] Figure 3 The images show scanning electron microscope (SEM) images of the polymer hydrogel prepared in Example 1 before and after swelling. It can be seen that the surface and cross-section of the hydrogel before swelling exhibit a uniform and regular microstructure; however, 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 carry a standard weight of 3 kg at different loading angles (including 0°, 60°, 90° and 120°) without significant damage, which directly demonstrates that the hydrogel prepared in this example has excellent mechanical load-bearing properties.

[0101] The mechanical test results of the polymer hydrogels prepared in Examples 1-7 are as follows: Figure 5 When the total monomer concentration is at a low level (<10 mol L-), 1 When the total monomer concentration is above 10 mol L-, the mechanical properties of the hydrogel (such as tensile strength and Young's modulus) show a relatively gradual increase with increasing concentration, while when the total monomer concentration exceeds 10 mol L- 1 Subsequently, the mechanical properties of the hydrogel rapidly increased when the total monomer concentration was 12 mol L- 1 At this point, the overall mechanical properties of the polymer hydrogel reach their peak, after which both the fracture strength and toughness of the hydrogel decrease. This is mainly related to the changes in the microstructure inside the gel network. Higher monomer concentrations help to form a denser and more complete polymer network, in which the density of the hard phase structure that contributes to strength increases rapidly with increasing monomer concentration, thus giving the material stronger resistance to deformation.

[0102] The mechanical test results of the polymer hydrogels prepared in Examples 1 and 8-11 are as follows: Figure 6 The total monomer concentration is 12 mol L- 1The effect of the molar ratio of comonomer acrylamide (AM) to acrylic acid (AA) on the mechanical properties of the hydrogel in this embodiment was investigated. The study showed that as the proportion of acrylamide monomer gradually increased, the tensile strength of the prepared hydrogel remained at a high level without significant fluctuations; however, its maximum tensile length (i.e., elongation at break) gradually decreased with increasing acrylamide content. This phenomenon is mainly due to the fact that the introduction of acrylamide segments increases the rigidity of the gel network, while relatively reducing the proportion of flexible segments (such as acrylic acid segments or the looser network structure they form) that impart high ductility to the material, thus affecting the overall toughness and ultimate tensile strength of the material. Notably, when the proportion of acrylamide monomer is 15%, the polymer hydrogel in this embodiment exhibits the optimal combination of comprehensive mechanical properties, with a tensile strength as high as 18.33 MPa, an elongation at break of 690%, and a toughness (characterized by fracture energy) as high as 47.87 MJ·m. -3 .

[0103] Comparison of the mechanical test results of the polymer hydrogels prepared in Example 1 with those of Comparative Examples 1-2 is as follows: Figure 7 As shown, the polymer hydrogel in this embodiment exhibits significant performance advantages, with a tensile strength of nearly 18.33 MPa and a toughness of 47.87 MJ·m. -3 The elongation at break was also close to 690%, achieving a perfect balance of high strength, high toughness, and high elasticity. In contrast, the hydrogels prepared in Comparative Example 1 and Comparative Example 2 (dashed area) exhibited extremely low mechanical properties, with fracture strengths below 5 MPa and toughness below 10 MJ·m. -3 In summary, the preparation method used in the comparative example is not only cumbersome, but also yields a product with unsatisfactory performance, failing to meet the requirements of high-performance applications. In contrast, the preparation method proposed in Example 1 of this invention successfully produces a high-performance hydrogel with comprehensive mechanical properties far exceeding those of the comparative example, demonstrating significant technological advantages.

[0104] Optical photographs of the high-strength, high-toughness polymer hydrogel prepared in Example 1 during the stretching process are shown below. Figure 8 As shown, during uniaxial stretching of the polymer hydrogel in this embodiment, as the stretching ratio gradually increases, the macroscopic appearance of the hydrogel gradually changes from an initial colorless and transparent state to an opaque white state. This stretch-induced color change phenomenon may be related to the intensified phase separation behavior within the hydrogel under tensile strain. Microscopic phase separation leads to changes in light scattering, thus macroscopically manifesting as stress-induced whitening, where the gel's appearance changes from colorless and transparent to white. When the tensile stress is removed, the white opaque appearance gradually returns to the initial colorless and transparent state. Figure 9This stress-induced whitening phenomenon and its recovery characteristics may be related to the deorientation or reorganization (reorganization) process of the microcrystalline phase or orientation structure formed inside the hydrogel under stress after the stress is removed.

[0105] The puncture resistance tests of the polymer hydrogels prepared in Examples 1, 4, and 5 are as follows: Figure 10 As shown, when the total monomer concentration reaches 12 mol L... -1 At this point, the mechanical properties and flexibility of the polymer hydrogel reach a relative balance, and the maximum puncture resistance of the polymer hydrogel is 68.9 N, with a corresponding needle displacement of 79.8 mm. For example... Figure 11 As shown, the impact resistance test indicates that the polymer hydrogel prepared in Example 1 can absorb impact energy exceeding 2.94 kJ / m. These results demonstrate that the prepared polymer hydrogel not only possesses excellent tensile properties but also exhibits good puncture and impact resistance, showcasing 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, after 10 cycles of stretching to 400%, the maximum tensile strength of the polymer hydrogel significantly increased from the initial 2.83 MPa to 6.16 MPa, while the elongation at break only changed slightly, indicating that the polymer hydrogel has a significant strain-enhancing effect. Load-unloading cycle tests are shown below. Figure 13 As shown, with the gradual increase of the number of cycles, the stress value of the polymer hydrogel prepared in Example 5 under a specific strain also gradually increases, indicating that its internal microstructure undergoes a favorable adjustment under mechanical stress, thereby improving its mechanical properties.

[0107] SEM images of the polymer hydrogel prepared in Example 1 after stretching cycles and recovery are shown below. Figure 14 As shown, the surface of the hydrogel sample after stretching and recovery formed obvious wrinkled structures, with larger wrinkles being about 10 μm. Nanoscale wrinkled structures (50 nm) were also formed on the surface of the larger wrinkles.

[0108] The Fourier transform infrared (FTIR) spectra of the polymer hydrogel prepared in Example 1 are as follows: Figure 15 As shown, at approximately 3500cm -1 Up to 2800cm -1 The broad absorption peak in the wavenumber region is attributed to the OH stretching vibration, indicating the presence of numerous hydrogen bond interactions within the hydrogel. The X-ray diffraction (XRD) results of the polymer hydrogel prepared in Example 1 are as follows: Figure 16As shown, the polymer hydrogel exhibits a distinct broad diffraction peak at a position of approximately 22° 2θ. The position and shape of this diffraction peak differ from the typical diffraction characteristics of conventional polyacrylic acid or polyacrylamide hydrogels. The presence of this structure indicates the existence of a certain degree of ordered chain segment arrangement or nanoscale "microcrystalline" regions within the hydrogel, rather than a completely amorphous morphology. These dense regions or ordered structures are one of the key factors contributing to the excellent mechanical properties of hydrogels.

[0109] The small-angle X-ray scattering results of the polymer hydrogels prepared in Examples 1 and 5 are as follows: Figure 17 As shown, the polymer hydrogel sample has a scattering vector q value The presence of distinct diffraction peaks at certain positions further confirms that the polymer hydrogel has formed a microcrystalline structure or periodic nanoscale ordered domains with a certain degree of regularity within it. For strain-enhanced hydrogel samples, the intensity of the corresponding diffraction peaks in their SAXS spectra 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 Examples 1 and 5 are as follows: Figure 18 As shown in the figure, all hydrogel samples exhibit a broad endothermic peak within the temperature range of approximately 90℃-140℃. This is attributed to the melting or dissociation of the internal physical cross-linking network or microcrystalline structure of the hydrogel, demonstrating the formation of an ordered microstructure within the hydrogel. For the hydrogel samples of Examples 1 and 5 that recovered after stretching, the corresponding endothermic peak area in their DSC spectra increased significantly. This indicates that the stress-induced effect during stretching effectively promotes the orderly arrangement of polymer chain segments within 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 provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength, high-toughness polymer hydrogel, characterized in that, The specific steps are as follows: S1. Dissolve amide monomers and acrylic monomers sequentially in lithium chloride solution, mix thoroughly to obtain monomer solution; S2. Add polyethylene glycol diacrylate and photoinitiator to the monomer solution obtained in step S1, mix well to obtain hydrogel prepolymer solution; S3. The hydrogel prepolymer obtained in step S2 is subjected to photopolymerization to obtain a polymer hydrogel. 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; In step S1, the total concentration of amide monomers and acrylic monomers in the monomer solution is 11-13 mol / L. -1 That is, the total monomer concentration is 11 ~ 13 mol L. -1 ; Of these, acrylic monomers account for 65% to 85%, and amide monomers account for 15% to 35%. In step S2, the average molecular weight of the polyethylene glycol diacrylate is 600 to 2000, and the concentration of the polyethylene glycol diacrylate is 0.1‰ to 10% of the total monomer concentration.

2. The method for preparing a high-strength, 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 is 5 to 50%.

3. The method for preparing a high-strength, 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.

4. The method for preparing a high-strength, high-toughness polymer hydrogel according to claim 1, characterized in that, In step S3, the photopolymerization reaction is performed using an ultraviolet light source at a wavelength of 360-370 nm. The photopolymerization reaction takes 1 to 300 minutes and is carried out at room temperature.

5. A high-strength, high-toughness polymer hydrogel, characterized in that, The polymeric hydrogel is prepared by any of the preparation methods described in claims 1-4.

6. The high-strength, high-toughness polymer hydrogel according to claim 5, characterized in that, The polymer hydrogel has a porous three-dimensional polymer network structure, and the interior of the three-dimensional polymer network has ordered chain segments or nanoscale "microcrystal" regions.

7. The application of a high-strength, high-toughness polymer hydrogel as described in claim 5 or claim 6 in the preparation of flexible protective materials, energy absorption buffer devices, and smart wearable sensor devices.

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