Mechanically interlocked catemer-like hydrogel and method of making same

Abstract

The application discloses a kind of mechanically interlocked catenoid structure hydrogel and preparation method thereof, belong to hydrogel sensing technical field.The preparation steps of the mechanically interlocked catenoid structure hydrogel are as follows: first, prepare carbon nano network solution using hydroquinone;Then the carbon nano network solution, acrylamide, water, crosslinking agent and photo initiator are mixed, and are treated under ultraviolet light irradiation, to obtain the hydrogel.A kind of mechanically interlocked catenoid structure hydrogel is constructed by introducing three-dimensional carbon nano network, blending with acrylamide monomer and in-situ radical polymerization.Carbon nano network provides continuous porous skeleton, polyacrylamide segment is embedded in carbon nano network pore during polymerization, and forms stable catenoid structure by physical winding, space nesting and mechanical interlocking.The prepared hydrogel has excellent mechanical properties, adhesion and strain response capacity, and provides reliable and economical material basis for flexible strain sensing function.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel sensing technology, and more specifically relates to a mechanically interlocked nephrite-like hydrogel and its preparation method. Background Technology

[0002] Hydrogels are a class of materials composed of hydrophilic polymer networks capable of absorbing and retaining large amounts of water. Hydrogels are structurally and functionally very similar to natural biological tissues, thus holding broad application prospects in biomedicine, wearable electronics, tissue engineering, and other fields. In these fields, superior mechanical properties are essential. Traditional single-network hydrogels typically exhibit softness or brittleness, lacking effective energy dissipation mechanisms and prone to stress concentration under load, resulting in generally poor mechanical properties and toughness. Furthermore, there is often a trade-off between the toughness and stiffness of hydrogels, as well as between the fatigue threshold and stiffness. Generally, increasing mechanical strength leads to material hardening, making it difficult for hydrogels to simultaneously possess high toughness and high strength. This disadvantage in mechanical properties severely restricts the development and widespread application of traditional hydrogels in practical applications.

[0003] For example, commonly used polyacrylamide hydrogel (PAM hydrogel) is a synthetic polymer hydrogel composed of polyacrylamide polymer chains forming a three-dimensional network structure through cross-linking agents. Due to its excellent hydrophilicity and tunable physicochemical properties, the basic structure of PAM hydrogel is constructed from acrylamide monomers through free radical polymerization, forming a stable network structure through physical or chemical cross-linking. This structure gives it high water content, good softness, and strong plasticity. However, traditional polyacrylamide hydrogels have certain mechanical property deficiencies, such as poor toughness, easy breakage, and difficulty in withstanding external forces. This limits its application in some high-strength environments.

[0004] Therefore, developing a polyacrylamide hydrogel with excellent mechanical properties is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a mechanically interlocked nephrite-like hydrogel and its preparation method, so as to solve the problems existing in the prior art and realize the preparation of polyacrylamide hydrogels with high mechanical strength.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention is to provide a method for preparing a mechanically interlocked, cable-like hydrogel, comprising the following steps:

[0008] Hydroquinone was dissolved in water and subjected to a hydrothermal reaction to obtain a carbon nanonetwork solution.

[0009] The carbon nanotube network solution, acrylamide, water, crosslinking agent, and photoinitiator are mixed to obtain a mixture; the mixture is then treated under ultraviolet light irradiation to obtain the mechanically interlocked chord-like hydrogel.

[0010] Preferably, the hydrothermal reaction is carried out at a temperature of 170–190°C for 1.5–2.5 hours.

[0011] Preferably, the concentration of the carbon nanonetwork solution is 0.5–2 wt%.

[0012] Preferably, the crosslinking agent includes N,N-methylenebisacrylamide, polyethylene glycol diacrylate, or tetra-arm acrylate polyethylene glycol; the photoinitiator includes 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, 2,2-dimethoxy-1,2-diphenylethane-1-one, phenyl-2,4,6-trimethylbenzoyl lithium phosphinate, or polyethylene glycol diacrylate.

[0013] Preferably, in the process of preparing the mechanically interlocked nephrite-like hydrogel, the mass ratio of the carbon nanotube network solution, water, acrylamide, photoinitiator and crosslinking agent is 2.5:5:5:0.03:0.003.

[0014] Preferably, the mixing time is 0.5 to 2 hours.

[0015] Preferably, the treatment time under ultraviolet light irradiation is 5 to 10 minutes, and the wavelength of the ultraviolet light is 350 to 380 nm.

[0016] In this invention, hydroquinone plays the following role:

[0017] (1) Specific molecular symmetry and rigid framework: The p-position hydroxyl structure of hydroquinone can form a relatively regular and stable π-π stacking. It provides an ideal structural template in the formation of conjugated carbon skeletons (such as carbon dots, graphene-based materials) or self-assembly.

[0018] (2) Easily oxidized to form p-benzoquinone: Hydroquinone is easily oxidized to form a conjugated quinone structure, which is conducive to carbonization and nucleation.

[0019] (3) Formation of special hydrogen bonds or π-π interactions: Hydroquinone has a planar rigid structure, and its two hydroxyl groups can participate in hydrogen bonding or π-π interactions simultaneously, forming a stable self-assembly. In contrast, catechol and resorcinol have different steric hindrances and electronic effects, making it difficult for them to form the same stable structure.

[0020] (4) Unique effect on product properties: The carbon skeleton provided by hydroquinone can form a more uniform graphitized layer with fewer defects after high-temperature carbonization. In hydrogels, it can significantly improve their mechanical properties, electrical conductivity and stability.

[0021] In this invention, acrylamide has excellent polymerization activity, hydrophilicity and hydrogen bonding ability, and is a monomer for forming hydrogels.

[0022] Therefore, this invention achieves the preparation of high-performance hydrogels by combining hydroquinone and acrylamide.

[0023] Furthermore, during the preparation of the mechanically interlocked nephrite-like hydrogel described in this invention, various parameters still affect the hydrogel's performance, specifically as follows: Higher hydroquinone concentrations increase crosslinking density, generally improving the hydrogel's mechanical strength but decreasing water absorption and swelling. Lower concentrations result in a sparse network, making the hydrogel soft but mechanically weak, prone to swelling and even dissolving. Increasing the amount of crosslinking agent increases the network crosslinking density, making the hydrogel stronger, but excessive amounts can increase brittleness. Insufficient crosslinking agent may lead to an unstable network. During polymerization, excessively low reaction temperatures result in low initiation efficiency and incomplete polymerization, leading to a loose network; excessively high reaction temperatures lead to premature chain termination, structural defects, and even degradation; excessively short reaction times result in insufficient polymerization or crosslinking, poor hydrogel mechanical properties, and easy breakage; excessively long reaction times lead to over-crosslinking, reducing swelling and making the material hard and brittle.

[0024] The second technical solution of the present invention provides a mechanically interlocked nephrite-like hydrogel prepared by the above preparation method.

[0025] The third technical solution of the present invention provides the application of the above-mentioned mechanically interlocked cable-like hydrogel in the preparation of bonding materials or flexible sensors.

[0026] This invention introduces a carbon nanotube network, blends it with acrylamide monomer, and constructs a high-performance composite hydrogel with interpenetrating structure and mechanical interlocking effect through in-situ free radical polymerization. Specifically, acrylamide is dissolved in a carbon nanotube network solution, and a photoinitiator is used to decompose it under ultraviolet light to generate free radicals, thereby catalyzing a crosslinking agent to crosslink the acrylamide and form a cable-like structure hydrogel with the carbon nanotube network. The carbon nanotube network, as a rigid framework, provides a continuous three-dimensional porous support structure. During polymerization, polyacrylamide segments can penetrate into the pores and gaps of the carbon network. Through physical entanglement, spatial nesting, and topological confinement, stable interpenetration and mechanical interlocking between the carbon framework and polymer chains are achieved. This structural design brings multiple enhancement effects. On the one hand, the introduction of the carbon nanotube network effectively improves the dispersibility and interfacial compatibility of carbon materials in the hydrogel system, avoiding the aggregation problem of traditional carbon materials in highly polar aqueous phases. On the other hand, the interpenetration and interlocking mechanism significantly improves the mechanical properties of the hydrogel, such as tensile strength, fracture toughness, and recovery performance. Furthermore, the mechanically interlocked structure can effectively resist the damage and slippage of the network structure under external forces, thus endowing the composite hydrogel with stronger deformation resistance and structural stability. The resulting mechanically interlocked cable-like structure not only fully utilizes the mechanical and electrical advantages of carbon nanomaterials but also overcomes the fragility and brittleness of polymer hydrogels, exhibiting excellent comprehensive performance. This provides a reliable structural design strategy for the development of novel multifunctional smart hydrogel materials and can be widely applied in fields such as biomedicine, flexible electronics, and sensors.

[0027] The present invention discloses the following technical effects:

[0028] 1. By introducing a carbon nanotube network, this invention not only provides the mechanical properties of the hydrogel, but also serves as part of a conductive network, thereby improving the sensing performance of the hydrogel.

[0029] 2. Compared with traditional thermally initiated hydrogels, the hydrogel prepared by this invention has a controllable molding process. It employs photoinitiation, initiating polymerization under specific wavelength irradiation. The light irradiation can be precisely applied to the desired area, and the location and shape of the polymerization initiation are controllable. This avoids localized insufficient or excessive cross-linking caused by uneven heating, significantly improving the uniformity and molding quality of the hydrogel. Furthermore, it allows for rapid molding in a shorter time, effectively preventing molding defects caused by uneven heating.

[0030] 3. The photoinitiator used in this invention is safe and environmentally friendly, which significantly reduces the release of harmful substances during the preparation of the material and reduces its harm to the human body or the environment.

[0031] 4. The hydrogel with a nematic hydrogel structure of the present invention exhibits better mechanical properties, such as higher adhesion properties, providing a stable material basis for complex conductive sensing applications. Attached Figure Description

[0032] Figure 1 TEM image of the carbon nanonetwork prepared in Example 1;

[0033] Figure 2 SEM images of the carbon nanonetwork prepared in Example 1 at different magnifications;

[0034] Figure 3 SEM images of the hydrogel prepared in Example 1 at different magnifications;

[0035] Figure 4 SEM image of the hydrogel prepared in Comparative Example 1;

[0036] Figure 5 The stress-strain curves of the hydrogels prepared in Example 1, Comparative Example 1, and Comparative Example 5 are shown.

[0037] Figure 6 The stress-strain curves of the hydrogels prepared in Examples 2-4 and Comparative Examples 2-4 are shown.

[0038] Figure 7 A photograph of the hydrogel prepared in Example 3;

[0039] Figure 8 The adhesion strength curves of the hydrogels prepared in Example 1, Comparative Example 1, and Comparative Example 5 on the wood substrate are shown.

[0040] Figure 9 The curve showing the relative resistance change of the hydrogel strain sensor in Example 1 during finger bending.

[0041] Figure 10 The curve showing the relative resistance change of the hydrogel strain sensor in Example 1 during elbow flexion.

[0042] Figure 11 The curve shows the relative resistance change of the hydrogel strain sensor in Example 1 during wrist flexion. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0049] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products, and the source of these commercially available products does not affect the technical effect of this invention.

[0050] Unless otherwise specified, the room temperature involved in this invention is 25±5℃.

[0051] Example 1

[0052] S1. Add 1g of hydroquinone to 100mL of deionized water, place it in a pressure-resistant reaction flask, heat to 180℃ and react for 2h. Let the reaction container cool naturally to room temperature to obtain a carbon nanonetwork solution with a concentration of 1wt%.

[0053] S2. Add 5g of acrylamide to 2.5g of carbon nanonetwork solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form a hydrogel with a nephroloid structure.

[0054] Example 2

[0055] S1. Add 1.5g hydroquinone to 100mL of deionized water, place it in a pressure-resistant reaction flask and heat to 180℃ for 2h. Let the reaction container cool naturally to room temperature to obtain a carbon nanonetwork solution with a concentration of 1.5wt%.

[0056] S2. Add 5g of acrylamide to 2.5g of carbon nanonetwork solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form a hydrogel with a nephroloid structure.

[0057] Example 3

[0058] S1. Add 2g of hydroquinone to 100mL of deionized water, place it in a pressure-resistant reaction flask, heat to 180℃ and react for 2h. Let the reaction container cool naturally to room temperature to obtain a carbon nanonetwork solution with a concentration of 2wt%.

[0059] S2. Add 5g of acrylamide to 2.5g of carbon nanonetwork solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form a hydrogel with a nephroloid structure.

[0060] Example 4

[0061] S1. Add 0.5g hydroquinone to 100mL of deionized water, place it in a pressure-resistant reaction flask, heat to 180℃ and react for 2h. Let the reaction container cool naturally to room temperature to obtain a carbon nanonetwork solution with a concentration of 0.5wt%.

[0062] S2. Add 5g of acrylamide to 2.5g of carbon nanonetwork solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form a hydrogel with a nephroloid structure.

[0063] Comparative Example 1

[0064] S1. Add 1g of hydroquinone to 100mL of deionized water and stir at room temperature for 2h to obtain a hydroquinone solution with a concentration of 1wt%.

[0065] S2. Add 5g of acrylamide to 2.5g of hydroquinone solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form hydroquinone polyacrylamide hydrogel.

[0066] Comparative Example 2

[0067] S1. Add 1.5g of hydroquinone to 100mL of deionized water and stir at room temperature for 2h to obtain a hydroquinone solution with a concentration of 1.5wt%.

[0068] S2. Add 5g of acrylamide to 2.5g of hydroquinone solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form hydroquinone polyacrylamide hydrogel.

[0069] Comparative Example 3

[0070] S1. Add 2g of hydroquinone to 100mL of deionized water and stir at room temperature for 2h to obtain a hydroquinone solution with a concentration of 2wt%.

[0071] S2. Add 5g of acrylamide to 2.5g of hydroquinone solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form hydroquinone polyacrylamide hydrogel.

[0072] Comparative Example 4

[0073] S1. Add 1g of hydroquinone to 200mL of deionized water and stir at room temperature for 2h to obtain a hydroquinone solution with a concentration of 0.5wt%.

[0074] S2. Add 5g of acrylamide to 2.5g of hydroquinone solution and 5g of deionized water. After stirring and mixing evenly, add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and then immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form hydroquinone polyacrylamide hydrogel.

[0075] Comparative Example 5

[0076] Preparation of pure polyacrylamide hydrogel:

[0077] Add 5g of acrylamide to 7.5g of deionized water and stir until homogeneous. Then add 0.003g of crosslinking agent N,N-methylenebisacrylamide and 0.03g of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. Stir thoroughly for 2 hours and immediately transfer to a mold. Then irradiate under 365nm ultraviolet light for 6 minutes to form a pure polyacrylamide hydrogel.

[0078] The mechanical properties and toughness of the hydrogels prepared in Examples 1-4 and Comparative Examples 1-5 were calculated using the following methods:

[0079] The dumbbell-shaped specimens (75 mm × 12.5 mm × 2 mm) prepared in Examples 1–4 and Comparative Examples 1–5 were tested for tensile properties at room temperature. Uniaxial tensile measurements were performed using an electronic universal testing machine (Shenzhen Suntech Power Technology Co., Ltd., China) at an elongation speed of 80 mm / min.

[0080] Toughness is calculated based on the area under the stress-strain curve using the formula shown below:

[0081] ΔU=∫σdε;

[0082] In the formula, σ and ε are the stress (MPa) and strain (%) of the hydrogel, respectively.

[0083] The fracture strength, toughness, and maximum tensile strain of the hydrogels prepared in Examples 1-4 and Comparative Examples 1-5 are shown in Table 1.

[0084] Table 1. Fracture strength, toughness, and maximum tensile strain of the hydrogels prepared in Examples 1-4 and Comparative Examples 1-5.

[0085] Specimen Fracture strength (MPa) <![CDATA[Toughness (MJ / m -3 )]]> Tensile strain (%) Example 1 1 9.41 2053.16 Example 2 0.57 2.45 1000.456 Example 3 0.8 4.27 1183.89 Example 4 0.89 4.34 1239.54 Comparative Example 1 0.54 1.54 776.82 Comparative Example 2 0.45 1.44 771.92 Comparative Example 3 0.39 1.42 864.423 Comparative Example 4 0.33 1.32 982.54 Comparative Example 5 0.13 0.36 893.659

[0086] As can be seen from the data in Table 1, the hydrogel with a nephrite-like structure prepared in Example 1 exhibits the best mechanical properties, with a fracture strength, toughness, and maximum tensile strain reaching 1 MPa, 9.41 MJ / m, and 1 MPa, respectively. -3 The results show that using carbon nanotube networks as a nano-reinforcement approach effectively enhances the overall mechanical properties of the hydrogel. Further comparative analysis of the performance data from Examples 1-4 and Comparative Examples 1-5 reveals that the mechanical properties of the hydrogels exhibit a certain trend with changes in carbon nanotube network concentration and hydroquinone solution, indicating that the carbon nanotube network concentration significantly affects the reinforcement degree of the hydrogel network structure. This trend verifies the structural regulation and reinforcement role of the formed nematic hydrocarbon structure in the hydrogel network. Specifically, the abundant functional groups on the surface (such as hydroxyl and carboxyl groups) can form multiple hydrogen bonds or physical crosslinks with polyacrylamide segments, thereby constructing a stable interpenetrating network structure at the molecular level. This structure not only improves the energy dissipation capacity and fracture resistance of the hydrogel but also effectively alleviates stress concentration, contributing to stress transfer and structural integrity maintenance under large deformation conditions. This invention prepares a hydrogel with a mechanically interlocked cable-like structure, which not only significantly improves the fracture strength and toughness of the hydrogel, but also maintains excellent flexibility and stretchability, endowing the material with good comprehensive mechanical properties, and providing a solid material foundation for its application in flexible sensing, soft electronic devices and smart biomaterials.

[0087] Figure 1 This is a TEM image of the carbon nanonetwork prepared in Example 1. The image shows a distinct network structure, with smaller particles forming a nearly continuous porous band-like region. This indicates that the constructed carbon nanonetwork has formed a relatively continuous three-dimensional dispersed network structure. The distribution is relatively uniform, and the network contains a certain amount of porosity, indicating that it possesses porous and interconnected characteristics, which helps to improve the mechanical and electrical properties of the hydrogel.

[0088] Figure 2The images show SEM images of the carbon nanonetwork prepared in Example 1 at different magnifications. The images show obvious layered stacking and porous structure. Its multilayer structure provides abundant channels and reaction interfaces. The presence of pores can enhance the diffusion performance of molecules or ions. At the same time, the orderly arrangement of layers improves the mechanical properties and structural stability of the hydrogel.

[0089] Figure 3 The images show SEM images of the hydrogel prepared in Example 1 at different magnifications. A clearly regularly distributed pore structure can be observed, with pores extending along specific directions, forming a morphology similar to natural biological structures (such as leaf veins or honeycombs), demonstrating an anisotropic microstructure. This verifies that a mechanically interlocked, cable-like structure is formed between the carbon nanotube network and polyacrylamide. This structure helps improve the permeability, flexibility, and ion conductivity of the composite hydrogel, and also absorbs energy through pore deformation under stress, thereby enhancing its mechanical strength.

[0090] Figure 4 The image shows a SEM image of the hydrogel prepared in Comparative Example 1. The SEM image reveals a porous microstructure with irregularly shaped circular or elliptical pores that are relatively uniformly distributed and interconnected, forming a three-dimensional network structure. The pore walls are thin and smooth, indicating that the hydrogel possesses a good internal channel structure. This porous morphology endows the material with a high specific surface area and porosity.

[0091] Figure 5 The stress-strain curves of the hydrogels prepared in Example 1, Comparative Example 1, and Comparative Example 5 are shown in the figure. It can be seen from the figure that the hydrogel exhibits the strongest mechanical properties when the concentration of the carbon nanonetwork is 1 wt%. The fracture strength of Example 1 is 1 MPa, while the mechanical properties of Comparative Example 1 and Comparative Example 5 are 0.54 MPa and 0.13 MPa, respectively. Compared with Example 1, the mechanical properties of Comparative Example 1 and Comparative Example 5 are reduced. This is because the carbon nanonetwork forms an interpenetrating network with acrylamide, creating more physical cross-linking points. The chain entanglement and supramolecular interactions construct a hydrogel matrix with microphase-separated structural domains, resulting in excellent mechanical properties. However, since no interpenetrating network is formed between the hydroquinone solution and the acrylamide hydrogel, the cross-linking density is reduced, leading to decreased mechanical properties. Comparative Example 5 is a polyacrylamide hydrogel with a mechanical property of only 0.13 MPa. Because the polyacrylamide molecular chain has a linear structure, its molecular forces are weak. This structure makes the connections between molecular chains not tight enough, making them prone to relative sliding under external forces, resulting in poor mechanical properties.

[0092] Figure 6The stress-strain curves of the hydrogels prepared in Examples 2-4 and Comparative Examples 2-4 are shown. This figure compares the effects of different carbon nanotube network concentrations and structural designs on the mechanical properties of the hydrogels. As can be seen from the figure, the mechanical properties of the hydrogels prepared with different carbon nanotube network concentrations of 1.5 wt% (Example 2), 2 wt% (Example 3), and 0.5 wt% (Example 4) are 0.57 MPa, 0.8 MPa, and 0.89 MPa, respectively. When the carbon nanotube network concentration is 1.5 wt% and 2 wt%, the darker solution color limits the light penetration depth during photocuring, thus reducing the free radical polymerization reaction inside the hydrogel and resulting in insufficient crosslinking density, leading to a decrease in crosslinking density and consequently, reduced mechanical properties. Compared to Examples 2-4, the mechanical properties of Comparative Examples 2-4 are 0.45 MPa, 0.39 MPa, and 0.33 MPa, respectively, significantly lower than the corresponding examples. The main reason is the lack of synergistic effect between the carbon nanonetwork and the polyacrylamide chains in the comparative sample. An effective interpenetrating network structure failed to form between the hydroquinone solution and the acrylamide hydrogel, resulting in a significant reduction in both crosslinking density and energy dissipation capacity. This leads to a decrease in mechanical properties.

[0093] Figure 7 This is a photograph of the hydrogel prepared in Example 3.

[0094] Figure 8 The adhesion strength curves of the hydrogels prepared in Example 1, Comparative Example 1, and Comparative Example 5 on the wood substrate are shown. The test method is as follows: the hydrogels obtained in Example 1, Comparative Example 1, and Comparative Example 5 are cut into cubic blocks with a size of 20×20×1mm and adhered to the surface of a wood substrate with a size of 80×20×1mm. After applying manual pressure for a few minutes, an overlap shear test is performed using a universal testing machine.

[0095] Test results show that the carbon nanotube network polyacrylamide hydrogel used in Example 1 exhibits excellent adhesion performance on wood-based substrates, with a shear adhesion strength as high as 7.93 MPa, significantly better than Comparative Example 1 (2.32 MPa) and Comparative Example 5 (0.49 MPa), demonstrating its significant advantage in adhesion performance. This superior adhesion performance is mainly attributed to the multiple synergistic mechanisms inherent in the hydrogel material itself: First, the carbon nanotube network introduced into the hydrogel contains a large number of hydroxyl functional groups, which can form stable hydrogen bonds with the abundant hydroxyl groups on the wood surface, enhancing the chemical bonding force between the interfaces; second, the aromatic ring structure can undergo π-π stacking interactions with aromatic components such as lignin in the wood, further enhancing the interfacial interaction force. In addition, the hydrogel has good fluidity and permeability, enabling it to penetrate into the cell cavities, micropores, and channels of wood, achieving a wider physical contact area and mechanical interlocking effect. During the photo / thermal curing process, a uniform and dense three-dimensional cross-linked network structure is formed inside the hydrogel, significantly enhancing its internal cohesive strength and preventing peeling and breakage. This results in a dual enhancement in both interfacial adhesion and overall structural strength. The synergistic effect of these multiple interactions endows the hydrogel with extremely strong adhesion to the surfaces of natural porous materials such as wood, providing solid technical support for its practical applications in woodworking adhesives, bio-based bonding materials, and structural repair.

[0096] Figure 9 The curve shows the relative resistance change of the hydrogel strain sensor in Example 1 during finger bending.

[0097] Figure 10 The curve shows the relative resistance change of the hydrogel strain sensor in Example 1 during elbow flexion.

[0098] Figure 11 The curve shows the relative resistance change of the hydrogel strain sensor in Example 1 during wrist flexion.

[0099] The electrochemical sensing performance of the hydrogel was evaluated using an electrochemical workstation (model). At a constant potential, the change in current over time was measured to analyze the stability and response time of the current, and to evaluate the sensitivity and selectivity of the sensor. The testing method involved cutting the hydrogel sample into 20 (length) × 20 (width) × 1 mm (thickness) cubes and attaching them to the fingers, elbows, and wrists. Electrochemical impedance spectroscopy (EIS) was used for testing, with the voltage set at 0.1 V and the frequency range from 0.1 to 105 Hz. The resistance changes were observed and recorded.

[0100] from Figure 9The results show the relative resistance change of the carbon nanotube network polyacrylamide hydrogel strain sensor during finger joint bending. During the experiment, the sensor's resistance response was monitored by periodically bending the finger within a range of 30° to 90°. Figure 7 It can be clearly observed that as the joint bending angle changes, the resistance signal output by the sensor exhibits a highly consistent and repeatable response waveform. This clear, regular, and repeatable electrical signal output indicates that the sensor possesses good stability and reliability in actual dynamic strain detection, and can accurately respond to mechanical deformations of varying amplitudes. Even when in close contact with the finger skin, it maintains a stable signal output, demonstrating excellent flexibility, good interfacial adhesion, and superior human adaptability. These results further validate the sensor's application potential in wearable electronic devices, motion recognition, and human-computer interaction.

[0101] from Figure 10 As can be seen, the connection signal between the carbon nanotube network polyacrylamide hydrogel strain sensor and the elbow exhibits highly consistent and repeatable electrical signal characteristics. The stability and repeatability of these signals indicate that the sensor can accurately capture strain changes generated during elbow movement and convert them into reliable electrical signal outputs in practical applications. This clear and repeatable signal performance not only demonstrates the high sensitivity of the carbon nanotube network acrylamide hydrogel strain sensor in sensing elbow movement but also reflects its stability under complex physiological movement environments. This stability is crucial for wearable health monitoring devices because it ensures that the sensor maintains consistent performance over extended use, thus providing users with accurate and reliable health monitoring data. Furthermore, the sensor's high sensitivity and stability mean that it can generate significant electrical signal outputs even with minimal strain changes, enabling it to detect subtle changes in the elbow at different bending angles and movement speeds. This capability is of great significance for developing intelligent devices capable of real-time monitoring of human movement.

[0102] from Figure 11The curve shows the relative resistance change of the carbon nanotube network polyacrylamide hydrogel strain sensor during wrist flexion. It is clearly observed that with the periodic flexion and extension of the wrist, the sensor output resistance signal exhibits a well-regular and repeatable response. This clear, stable, and repeatable electrical signal response fully demonstrates the excellent adaptability and sensing reliability of this hydrogel strain sensor in practical dynamic biomechanical deformation detection. Furthermore, the signal fluctuation amplitude shows a good correlation with the wrist movement amplitude, indicating that the sensor possesses high mechanical response sensitivity and low signal drift, enabling accurate capture and differentiation of microbial movement. This lays a solid foundation for its application in wearable health monitoring, human-computer interaction, and other fields.

[0103] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0104] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a mechanically interlocked, cable-like hydrogel, characterized in that, Includes the following steps: Hydroquinone was dissolved in water and subjected to a hydrothermal reaction to obtain a carbon nanonetwork solution. The carbon nanotube network solution, acrylamide, water, crosslinking agent, and photoinitiator are mixed to obtain a mixture; the mixture is then treated under ultraviolet light irradiation to obtain the mechanically interlocked chord-like hydrogel. The hydrothermal reaction is carried out at a temperature of 170~190℃ for a time of 1.5~2.5h. The concentration of the carbon nanonetwork solution is 0.5~2wt%; The crosslinking agent is N,N-methylenebisacrylamide; the photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone; In the process of preparing the mechanically interlocked nephrite-like hydrogel, the mass ratio of the carbon nanotube network solution, water, acrylamide, photoinitiator and crosslinking agent is 2.5:5:5:0.03:0.003; The treatment time under ultraviolet light irradiation is 5-10 minutes, and the wavelength of the ultraviolet light is 350-380 nm.

2. The preparation method according to claim 1, characterized in that, The mixing time is 0.5 to 2 hours.

3. The mechanically interlocked nephrite-like hydrogel prepared by the preparation method according to claim 1 or 2.

4. The application of the mechanically interlocked nephrite-like hydrogel of claim 3 in the preparation of bonding materials or flexible sensors.

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