Mechanical training toughened dynamic covalent crosslinked highly entangled zwitterionic polyelectrolyte hydrogel, its preparation method and application

Abstract

The present application relates to a kind of mechanical training toughening dynamic interlocking high entanglement amphoteric polyelectrolyte hydrogel and its preparation method and application, high entanglement amphoteric polyelectrolyte hydrogel HEPA is soaked in cation monomer solution, make cation monomer fully diffuse to network interior, reach swelling equilibrium;Subsequently, the hydrogel HEPA of soaking is carried out cyclic force induction experiment, in the process of force induction training, network fracture and reorganization occur in the interior network of hydrogel HEPA, simultaneously trigger in-situ polymerization, after repeated network reorganization and in-situ polymerization of force induction, make network hydrogel internal structure become more densification, obtain mechanical training toughening dynamic interlocking high entanglement amphoteric polyelectrolyte hydrogel HEPA-D The preparation process of the present application is simple, production cycle is short, process condition is simple, raw material is easy to obtain, production cost is low, the obtained hydrogel not only has high tough performance, but also has significant strain hardening enhancement effect required by induced biological soft tissue, fatigue resistance effect.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a dynamic interlocking, highly entangled amphoteric polyelectrolyte hydrogel for mechanical training and toughening, as well as its preparation method and application. Background Technology

[0002] Amphoteric polyelectrolyte hydrogels have good biocompatibility and adjustable mechanical properties, and have broad application prospects in fields such as flexible electronics, tissue engineering and soft robotics. However, the performance of traditional materials is easily weakened during long-term cyclic use, making it difficult to meet the requirements of high reliability.

[0003] To improve the structural controllability and mechanical properties of hydrogels, the use of free radicals to regulate the hydrogel network structure holds promise for simultaneously enhancing the mechanical properties, fatigue resistance, and structural stability of hydrogels through the synergistic effect of physical rearrangement and chemical crosslinking. The Zhang research group [Bao B., Shi C., Zeng Q., Chen T., Xiao C, Jiang L., Liu T., LyuJ., Wang W., Zhu L., Lin Q., Photocoupling of propagating radicals during polymerization realizes universal network strengthening. Nat. Synth. 2025, 4, 1-18.] has studied the use of monomers containing o-nitrobenzyl (NB) photosensitive groups to partially replace commonly used vinyl monomers. This delayed and efficient coupling with propagating free radicals significantly improves the heterogeneity of the photopolymerization network, increasing the hydrogel strength and toughness by up to 20 times and 70 times, respectively, while maintaining rapid molding, making it suitable for various polymer systems.

[0004] While traditional double-network hydrogels can generate free radicals through external forces, their free radical generation efficiency is low, and their in-situ polymerization rate is slow, making it difficult to reinforce them in real time during deformation and easily leading to rapid crack propagation. The research group of Gong [Wang ZJ, Jiang J., Mu Q., Maeda. S., Nakajima T., Gong. JP, Azo-Crosslinked Double-NetworkHydrogels Enabling Highly Efficient Mechanoradical Generation. J. Am.Chem. Soc., 2022,144(7), 3154-3161.] found that introducing weak covalent bonds with low bond dissociation energy into the polymer network is an effective strategy to improve the efficiency of mechanochemical reactions. Among them, the use of highly efficient crosslinking agents with azo photosensitive groups, due to their low bond energy and ease of directional homolytic cleavage under force to generate free radicals, becomes an ideal mechanochemical free radical source, increasing the free radical concentration to 5 times that of the traditional system and the free radical generation energy efficiency to 10 times.

[0005] The aforementioned reports on mechanically toughened hydrogels all require the introduction of highly reactive azoalkane / o-nitrobenzyl compounds into the reactive monomers to promote free radical reactions triggered by mechanical training, thereby strengthening the rigid backbone chains. However, this approach also leads to system instability, making the system prone to network reconstruction and inactivation under light or heating conditions, thus losing its training and toughening function. No reports have yet described a method to achieve strain hardening and fatigue resistance properties similar to biological soft tissue using only a single, universal vinyl monomer unit in the hydrogel.

[0006] In the course of their research, the inventors of this application designed and constructed a dynamic interlocking highly entangled amphoteric polyelectrolyte hydrogel with mechanical training and toughening properties. This hydrogel combines high strength and toughness, strain hardening enhancement effect, and fatigue resistance, providing a feasible solution for the directional design and engineering application of high-performance hydrogels. Summary of the Invention

[0007] One of the objectives of this invention is to provide a method for preparing a dynamic interlocking, highly entangled amphoteric polyelectrolyte hydrogel with enhanced mechanical strength and toughness. This method is simple to operate, uses readily available raw materials, and has a low cost. The resulting hydrogel possesses high strength, high toughness, strain hardening, and fatigue resistance.

[0008] The technical solution of the present invention to achieve the above objectives is as follows: A method for preparing a mechanically toughening, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel includes the following steps: 1) A mixture A is prepared by dispersing the components including anionic monomers, cationic monomers, crosslinking agents, initiators and solvents. After curing and water equilibration, amphoteric polyelectrolyte hydrogel PA is obtained. The obtained PA is immersed in a mixture B containing the same components, and then cured and water equilibrated again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA. 2) Immerse the HEPA obtained in step 1) in mixture C, wherein mixture C contains cationic monomers and solvents; 3) Remove the HEPA from the mixture C and perform cyclic stretching treatment to obtain the dynamically interlocked, highly entangled polyampholyte hydrogel HEPA-D.

[0009] Furthermore, the anionic monomer is an unsaturated alkenyl monomer with a reactive anionic group, such as sodium styrene sulfonate (NaSS), and the cationic monomer is an unsaturated alkenyl monomer with a reactive cationic group, such as one or two of acryloyloxyethyltrimethylammonium chloride (DAC) and N,N,N-trimethyl-3-(2-methylallylamino)-1-propanammonium chloride (MPTC).

[0010] Further, in the mixture A, the concentration of the anionic monomer is 1 mol / L to 1.2 mol / L; optionally, the concentration of the anionic monomer is 1.1 mol / L, 1.11 mol / L, 1.12 mol / L, 1.13 mol / L, 1.14 mol / L, 1.15 mol / L, 1.16 mol / L, 1.17 mol / L, 1.18 mol / L, 1.19 mol / L, or 1.2 mol / L.

[0011] Further, in the mixture A, the concentration of the cationic monomer is 1 mol / L to 1.2 mol / L; optionally, the concentration of the cationic monomer is 1.1 mol / L, 1.11 mol / L, 1.12 mol / L, 1.13 mol / L, 1.14 mol / L, 1.15 mol / L, 1.16 mol / L, 1.17 mol / L, 1.18 mol / L, 1.19 mol / L, or 1.2 mol / L.

[0012] Further, in the mixture A, the crosslinking agent accounts for 0.01% to 0.12% of the total molar amount of the monomers; optionally, the molar amount of the crosslinking agent is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, or 0.12% of the total molar amount of the monomers.

[0013] Further, in the mixture A, the initiator accounts for 0.01% to 0.12% of the total molar amount of the monomers; optionally, the molar amount of the initiator is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, or 0.12% of the total molar amount of the monomers.

[0014] Further, in the mixture B, the concentration of the anionic monomer is 0.1 mol / L to 1.2 mol / L, more preferably 0.5 mol / L to 1.2 mol / L; optionally, the concentration of the anionic monomer is 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.11 mol / L, 1.12 mol / L, 1.13 mol / L, 1.14 mol / L, 1.15 mol / L, 1.16 mol / L, 1.17 mol / L, 1.18 mol / L, 1.19 mol / L, or 1.2 mol / L.

[0015] Further, in the mixture B, the concentration of the cationic monomer is 0.1 mol / L to 1.2 mol / L, more preferably 0.5 mol / L to 1.2 mol / L; optionally, the concentration of the cationic monomer is 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.11 mol / L, 1.12 mol / L, 1.13 mol / L, 1.14 mol / L, 1.15 mol / L, 1.16 mol / L, 1.17 mol / L, 1.18 mol / L, 1.19 mol / L, or 1.2 mol / L.

[0016] Further, in the mixture B, the crosslinking agent accounts for 0.01% to 0.12% of the total molar amount of the monomers; optionally, the molar amount of the crosslinking agent is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, or 0.12% of the total molar amount of the monomers.

[0017] Further, in the mixture B, the initiator accounts for 0.01% to 0.12% of the total molar amount of the monomers; optionally, the molar amount of the initiator is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, or 0.12% of the total molar amount of the monomers.

[0018] Furthermore, the components and concentrations of the components in mixture A and mixture B are the same.

[0019] Furthermore, the cationic monomer in the mixture C is the same as the cationic monomer in mixture A and / or mixture B.

[0020] Further, in the mixture A and / or the mixture B, the ratio of the concentration of anionic monomer to the concentration of cationic monomer is 1:(0.9-1.1); for example, the concentration of anionic monomer is 1.12 mol / L and the concentration of cationic monomer is 1.18 mol / L.

[0021] Further, in the mixture C, the concentration of the cationic monomer is 0.01 mol / L to 0.08 mol / L, more preferably 0.03 mol / L to 0.07 mol / L, and optionally, the concentration of the cationic monomer is 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, or 0.07 mol / L.

[0022] Furthermore, the strain of the cyclic stretching is 200% to 600%, for example 210%, 280%, 350%, 420%, 490%, 560%, and 595%.

[0023] Furthermore, the number of cycles of the cyclic stretching is 1-100 times, for example 1, 2, 3, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100.

[0024] Furthermore, during the cyclic force-induced training in step 3), the stretching rate is 80 mm / min to 120 mm / min, for example, 80 mm / min, 90 mm / min, 100 mm / min, or 110 mm / min.

[0025] Furthermore, in step 3), the HEPA is replenished with cationic monomers during the cyclic stretching process; for example, cyclic stretching is performed in the presence of a cationic monomer solution.

[0026] Further, in step 3), the HEPA is immersed in a cationic monomer solution for cyclic stretching, or the cationic monomer solution is continuously sprayed during the cyclic stretching of the HEPA.

[0027] Further, in step 3), the composition of the cationic monomer and / or its concentration in the solution is the same as that of solution C.

[0028] The second objective of this invention is to provide a mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, prepared by the method described above.

[0029] The third objective of this invention is to provide an application of a mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as a bio-tissue engineering alternative, flexible electronics, and soft robotics material.

[0030] This invention involves immersing a highly entangled amphoteric polyelectrolyte hydrogel (HEPA) in a cationic monomer solution until equilibrium is reached. The equilibrium hydrogel is then subjected to cyclic force-induced training. During this training process, the internal network of the HEPA hydrogel breaks down and reassembles. Simultaneously, the immersed cationic monomers generate free radicals, triggering in-situ polymerization, resulting in a mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, HEPA-D. Compared to traditional dual-network (DN) hydrogels, this invention eliminates the need for "high-concentration crosslinking agents + monomers" to reconstruct the entire backbone chain. Instead, it strengthens the rigid backbone chain through the mechanical training process, achieving a localized breakage-reassembly mechanism. This allows the hydrogel to form a denser network structure after mechanical training. The employed mechanical training strategy enables the hydrogel's performance to continuously improve with training cycles, demonstrating unique structural plasticity and controllability. Traditional dual-network (DN) hydrogels, after reconstructing the backbone chain through "high-concentration crosslinking agent + monomer", exhibit a more significant strain softening effect after the rigid chain is strengthened, resulting in weaker fatigue resistance. In contrast, the dynamically interlocked, highly entangled polyamphoteric electrolyte hydrogel HEPA-D prepared by this method, enhanced through mechanical training, exhibits a significant strain hardening enhancement effect and fatigue resistance effect required by biological soft tissues. This demonstrates the unique advantage of precisely controlling the micro-network structure and achieving controllable performance improvement through mechanical training, and has significant application potential and promotional value.

[0031] Compared with the prior art, the present invention has the following advantages and significant progress: 1) The preparation process of this invention is simple, the production cycle is short, the process conditions are simple, the raw materials are readily available, and the production cost is low; 2) The mechanically trained and toughened dynamic interlocking highly entangled amphoteric polyelectrolyte hydrogel HEPA-D prepared by this invention clarifies the integrated reinforcement path of "cationic monomer penetration - force-induced polymerization - dynamic monomer replenishment", and the resulting hydrogel has excellent strain hardening properties and fatigue resistance. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the preparation process of the dynamic interlocking and highly entangled amphoteric polyelectrolyte hydrogel with enhanced mechanical training according to an embodiment of the present invention. The hydrogel utilizes external force to induce the rearrangement of the internal network structure of the HEPA hydrogel and the synergistic effect of in-situ polymerization of the soaking monomers to achieve the reconstruction of the internal network of the hydrogel, thereby significantly enhancing the mechanical properties of the hydrogel.

[0033] Figure 2 This is a state diagram of the hydrogel obtained in the embodiments of this application under different tensile mechanical training cycles. Detailed Implementation

[0034] To make the present invention easier to understand, specific embodiments of the present invention will be further described below.

[0035] In the following embodiments, the "amphoteric monomer" includes anionic and cationic monomers, wherein the anionic monomer is sodium styrene sulfonate (NaSS), the cationic monomer is acryloyloxyethyltrimethylammonium chloride (DAC), and the solvent is water. The concentration of the anionic monomer in mixture A is 1.12 mol / L, and the concentration of the cationic monomer is 1.18 mol / L. The components and concentrations of each component in mixture B are the same as those in mixture A.

[0036] Example 1 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0037] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.03 mol / L.

[0038] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.03 mol / L DAC solution to obtain mechanically trained, toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D.

[0039] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0040] Example 2 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0041] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.04 mol / L.

[0042] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.04 mol / L DAC solution to obtain a mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, HEPA-D.

[0043] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0044] Example 3 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0045] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.05 mol / L.

[0046] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.05 mol / L DAC solution to obtain mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D.

[0047] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0048] Example 4 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0049] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.06 mol / L.

[0050] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.06 mol / L DAC solution to obtain a mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, HEPA-D.

[0051] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0052] Example 5 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0053] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.07 mol / L.

[0054] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.07 mol / L DAC solution to obtain mechanically trained, toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D.

[0055] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0056] Example 6 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0057] Step 2): Soak the hydrogel HEPA obtained in Step 1) in a mixed solution of DAC and deionized water for 2 h, with the concentration of DAC being 0.08 mol / L.

[0058] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.08 mol / L DAC solution to obtain a mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, HEPA-D.

[0059] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0060] Example 7 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0061] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.05 mol / L.

[0062] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching under a fixed strain of 420% at a stretching speed of 100 mm / min. After stretching to 420% in each cycle, remove the stress and allow it to relax naturally for 10 minutes before starting the next stretching cycle. Throughout the cyclic stretching process, spray with 0.05 mol / L DAC solution to obtain mechanically trained, toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D.

[0063] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0064] Example 8 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0065] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.05 mol / L.

[0066] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching under a fixed strain of 560% at a stretching speed of 100 mm / min. After stretching to 560% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.05 mol / L DAC solution to obtain mechanically trained, toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D.

[0067] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0068] Comparative Example 1 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0069] Step 2): Soak the hydrogel HEPA obtained in Step 1) in a mixed solution of DAC and deionized water for 2 h, with the concentration of DAC being 0.1 mol / L.

[0070] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.1 mol / L DAC solution to obtain mechanically trained, toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D.

[0071] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0072] Comparative Example 2 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0073] Step 2): Soak the hydrogel HEPA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.3 mol / L.

[0074] Step 3): Remove the HEPA gel soaked in Step 2) and perform 100 cycles of cyclic stretching at a constant strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to allow it to return to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with 0.3 mol / L DAC solution to obtain mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D.

[0075] The tensile strength of the obtained HEPA-D hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0076] Comparative Example 3 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0077] Step 2): Soak the HEPA hydrogel obtained in step 1) in a mixed solution of NaCl and deionized water for 2 h. The concentration of NaCl is 0.05 mol / L.

[0078] Step 3): Apply glycerin to the HE-PA soaked in Step 2), then perform 100 cycles of cyclic stretching at a constant strain of 490% and a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to return it to the original stretching point, and then begin the next stretching cycle. No NaCl solution is sprayed during the entire cyclic stretching process, resulting in a mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, HEPA-NaCl.

[0079] The tensile strength of the obtained HEPA-NaCl hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0080] Comparative Example 4 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A. After curing and water equilibration, obtain amphoteric polyelectrolyte hydrogel PA. Then immerse PA in a mixture B containing the same components, and cure and water equilibrate again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA.

[0081] Step 2): Soak the HEPA hydrogel obtained in step 1) in a mixed solution of NaCl and deionized water for 2 h. The concentration of NaCl is 0.05 mol / L.

[0082] Step 3): Take out the HEPA soaked in Step 2), and then perform 100 cycles of stretching under a constant strain of 490%. During the training process, spray NaCl solution with a concentration of 0.05 mol / L throughout to obtain a mechanically trained, toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel.

[0083] The tensile strength of the obtained hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0084] Comparative Example 5 Step 1): Weigh the amphoteric monomer, crosslinking agent, initiator and water to prepare a mixture A, and obtain the amphoteric polyelectrolyte hydrogel PA after curing and soaking in water to achieve equilibrium.

[0085] Step 2): Soak the hydrogel PA obtained in step 1) in a mixed solution of DAC and deionized water for 2 h. The concentration of DAC is 0.05 mol / L.

[0086] Step 3): Apply glycerin to the PA soaked in Step 2), then perform 100 cycles of cyclic stretching under a fixed strain of 490% at a stretching speed of 100 mm / min. After stretching to 490% in each cycle, remove the stress to return it to the original stretching point, and then begin the next stretching cycle. Throughout the cyclic stretching process, spray with DAC solution at a concentration of 0.05 mol / L to obtain a mechanically trained, toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, PA-D.

[0087] The tensile strength of the obtained hydrogel was tested using an electronic universal testing machine at a speed of 100 mm / min.

[0088] The mechanical properties of the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel obtained in the above embodiments and comparative examples are shown in Table 1 below: Table 1: Mechanical properties of mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogels

[0089] The blank control in the table represents HEPAs that have not undergone stretching training.

[0090] The data in Table 1 shows that: Examples 1-6 and Comparative Examples 1-2 are mechanically trained and toughened dynamically interlocked highly entangled amphoteric polyelectrolyte hydrogels HEPA-D prepared by changing the concentration of DAC during the process of soaking highly entangled amphoteric polyelectrolyte hydrogel HEPA in DAC solution; Examples 7 and 8 are mechanically trained and toughened dynamically interlocked highly entangled amphoteric polyelectrolyte hydrogels HEPA-D prepared by cyclic force induction under small strain and large strain with a fixed DAC concentration.

[0091] As can be seen from Examples 1-6, the mechanical properties of the mechanically strengthened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel HEPA-D material initially increase and then decrease with increasing DAC solution concentration. When the DAC concentration increases from 0.03 mol / L to 0.05 mol / L, the tensile strength increases from 2.5 MPa to 3.5 MPa, the elongation at break decreases from 668% to 400%, and the strain hardening index increases from 9.07 to 11.92. Further increasing the DAC concentration leads to a decrease in the mechanical properties of the HEPA-D hydrogel. When the DAC concentration increases from 0.05 mol / L to 0.3 mol / L, the tensile strength decreases from 3.5 MPa to 1.24 MPa, the elongation at break decreases from 400% to 180%, and the strain hardening index decreases from 11.92 to 3.00. An appropriate DAC concentration can form a uniform interpenetrating network, while an excessively high concentration can lead to electrostatic shielding and damage to some of the dynamically highly entangled structure.

[0092] As can be seen from Examples 7-8, when the strain of force-induced training is small, the toughening effect of the hydrogel is also light, which may be because the uniformity of the cross-linked network distribution is relatively large and the strain is small; however, the strain of force-induced training should not be too high, as it may cause micro-damage to the network, resulting in a decrease in the toughening effect.

[0093] Comparative Examples 3 and 4 show that NaCl cannot form a covalent reinforcing phase in the HEPA network. It only physically fills the gaps in the network as a small molecule and cannot form a stable interpenetrating structure with the HEPA matrix. During cyclic stretching, it can only achieve limited reinforcement through the slight orientation of the HEPA's own entangled network and cannot build a continuously reinforced mechanical framework. Comparative Example 5 shows that when HEPA is cyclically trained, the continuously replenished DAC monomers make the polyDAC network uniformly distributed in the HEPA matrix, and the highly dense interpenetrating network has a very strong energy dissipation capacity. In contrast, the energy dissipation capacity in PA is improved but is far weaker than that in the HEPA cyclic training system.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a mechanically toughening, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel, characterized in that, Includes the following steps: 1) A mixture A is prepared by dispersing the components including anionic monomers, cationic monomers, crosslinking agents, initiators and solvents. After curing and water equilibration, amphoteric polyelectrolyte hydrogel PA is obtained. The obtained PA is immersed in a mixture B containing the same components, and then cured and water equilibrated again to obtain highly entangled amphoteric polyelectrolyte hydrogel HEPA. 2) Immerse the HEPA obtained in step 1) in mixture C, wherein mixture C contains cationic monomers and solvents; 3) Remove the HEPA from the mixture C and perform cyclic stretching treatment to obtain the dynamically interlocked, highly entangled polyampholyte hydrogel HEPA-D.

2. The method for preparing the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 1, characterized in that, The anionic monomer is an unsaturated alkenyl monomer with a reactive anionic group, and the cationic monomer is an unsaturated alkenyl monomer with a reactive cationic group.

3. The method for preparing the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 1, characterized in that, The anionic monomer is sodium styrene sulfonate (NaSS), and the cationic monomer is selected from one or two of acryloyloxyethyltrimethylammonium chloride (DAC) and N,N,N-trimethyl-3-(2-methylallylamino)-1-propanium chloride (MPTC).

4. The method for preparing the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 1, characterized in that, In the mixture A: The concentration of the anionic monomer is 1 mol / L to 1.2 mol / L; The concentration of the cationic monomer is 1 mol / L to 1.2 mol / L; The crosslinking agent accounts for 0.01% to 0.12% of the total molar amount of the monomers; The initiator accounts for 0.01% to 0.12% of the total molar amount of the monomer.

5. The method for preparing the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 1, characterized in that, In the mixture B: The concentration of the anionic monomer is 0.1 mol / L to 1.2 mol / L; The concentration of the cationic monomer is 0.1 mol / L to 1.2 mol / L; The crosslinking agent accounts for 0.01% to 0.12% of the total molar amount of the monomers; The initiator accounts for 0.01% to 0.12% of the total molar amount of the monomer.

6. The method for preparing the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 1, characterized in that, In the mixture C, the concentration of the cationic monomer is 0.01 mol / L to 0.08 mol / L.

7. The method for preparing the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 1, characterized in that, The strain of the cyclic stretching is 200%~600%, and the number of cycles is 1-100.

8. The method for preparing the mechanically toughened, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 1, characterized in that, Step 3) The HEPA is replenished with cationic monomers during the cyclic stretching process.

9. A dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel for mechanical training and toughening, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The application of the mechanical training-strengthening, dynamically interlocked, highly entangled amphoteric polyelectrolyte hydrogel as described in claim 9, characterized in that, As an alternative to biological tissue engineering, and for applications in flexible electronics and soft robotics materials.

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