Preparation method of a highly stretchable, strong and tough, quickly recoverable and fatigue-resistant polyionic liquid hydrogel

Abstract

A preparation method of a highly stretchable, strong and tough, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel. The present invention relates to the field of the preparation of polyionic liquid hydrogels. The present invention aims to solve the technical problems of poor mechanical properties, lack of fatigue resistance, lack of antibacterial properties, and lack of biocompatibility of hydrogel-based wearable sensors. Method: First, prepare N-methyluracil-N-vinylimidazole chloride; second, prepare a polyionic liquid hydrogel. The polyionic liquid hydrogel prepared by the present invention has comprehensive properties such as good mechanical properties, recoverability, antibacterial properties, and biocompatibility, and also has high sensitivity and rapid responsiveness. The polyionic liquid hydrogel prepared by the present invention is applied to the field of wearable sensors.

Description

Technical Field

[0001] The present invention relates to the field of preparation of polyionic liquid hydrogels. Background Art

[0002] In recent years, wearable devices have developed rapidly in the fields of electronic skin, soft robots, and human-machine interfaces, etc., and have attracted extensive attention from researchers. However, the surface of the human skin is soft and can deform at any time. Traditional skin electrodes are usually rigid and cannot be bent arbitrarily, making it difficult to fix them on the surface of human tissues, which greatly limits the effective contact and fitting between electronic devices and the human body. Wearable electronic devices based on elastic polymer materials have attracted much attention due to their simple structure and convenient signal reading. However, these devices have defects such as complex manufacturing processes, extremely high prices, and poor dynamic performance in wearable applications. Therefore, the development of a flexible sensor with excellent comprehensive performance, low cost, and simple process will be of great significance for the further development of wearable electronic devices.

[0003] Hydrogel is a soft material composed of a three-dimensional cross-linked polymer network and a large amount of water. Due to its excellent properties such as flexibility, water retention, tissue similarity, and biocompatibility, hydrogels have been widely used in popular fields such as wearable electronic devices, flexible energy storage materials, electronic skin, and tissue repair. However, hydrogels as carrier materials for flexible wearable devices still have the following problems: ① Due to the presence of a large amount of water, hydrogels have the disadvantage of poor mechanical properties, including poor stretchability, fatigue resistance, and recovery; ② Hydrogels lack antibacterial activity performance; ③ The conductive and energy storage performance of hydrogels decreases due to the increase in the internal network density. Therefore, the preparation of hydrogel materials with excellent comprehensive performance still poses a challenge. Summary of the Invention

[0004] The present invention aims to solve the technical problems of poor mechanical properties, fatigue intolerance, lack of antibacterial and biocompatibility of hydrogel-based wearable sensors, and provides a preparation method for a highly stretchable, tough, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel.

[0005] A preparation method for a highly stretchable, tough, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel is specifically carried out according to the following steps:

[0006] I. Synthesis of a functional, multi-functional group ionic liquid monomer:

[0007] Add N-vinylimidazole and 6-chloromethyluracil into anhydrous methanol, displace with nitrogen until the system is clear and transparent, then heat under reflux. The obtained white solid is washed with anhydrous ethanol to obtain N-methyluracil-N-vinylimidazole chloride;

[0008] The synthesis process of N-methyluracil-N-vinylimidazole chloride is as follows:

[0009]

[0010] II. Preparation of a highly stretchable, strong, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel:

[0011] Mix sodium dodecyl sulfate, cellulose nanofibers, and water, stir until clear, then add lauryl methacrylate, stir to form a stable emulsion, add acrylamide and the N-methyluracil-N-vinylimidazole chloride prepared in Step 1, stir until clear, add an initiator, stir evenly, pour into a mold, and cure and copolymerize to obtain a hydrogel;

[0012] Soak the hydrogel in a CaCl2 solution to obtain the highly stretchable, strong, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel, thus completing the preparation.

[0013] Polyionic liquids are polymerization products of small molecule ionic liquids. Each repeating unit contains ionic liquid monomers, and a polymer network structure is formed through the connection of each polymer chain. Polyionic liquids have both the conductivity and antibacterial properties of ionic liquid monomers, and at the same time possess the physical and chemical stability unique to polymers. Compared with ionic liquid monomers, they have better biocompatibility. Currently, polyionic liquid polymer surface materials have gradually attracted the attention of researchers. Polyionic liquid dressings have excellent structural adjustability and broad-spectrum antibacterial properties compared to other polymer dressings. Similarly, the solvent resistance stability and low toxicity of polyionic liquid dressings ensure their reusability as dressings, thereby reducing the cost of dressing use.

[0014] The present invention aims to utilize the structural designability of ionic liquids to synthesize functional, multi-functional ionic liquid monomers, and starting from the perspective of network structure design, copolymerize with traditional monomers to develop a polyionic liquid hydrogel wearable sensor with good mechanical properties, recoverability, antibacterial properties, and other comprehensive properties, as well as high sensitivity and rapid responsiveness.

[0015] Advantages of the present invention:

[0016] First, the hydrogen bond interaction between MUI as a supramolecular crosslinking agent and each monomer forms the first crosslinking, the hydrophobic interaction of lauryl methacrylate in the SDS micelle forms the second physical crosslinking, the electrostatic interaction between MUI and the COO - in CNF forms the third crosslinking, and the coordination interaction between Ca 2+ and the COO - in CNF forms the fourth crosslinking. The resulting quadruple physically crosslinked polyionic liquid hydrogel exhibits the advantages of flexibility, strength, and fatigue resistance. When the hydrogel is stretched, the hydrogel can dissipate energy through the synergy of supramolecular action and hydrophobic action. On the other hand, Ca 2+The disruption of the coordination interaction with CNF can also dissipate part of the energy. The obtained hydrogel has excellent mechanical properties, with a fracture stress of 754 kPa, a fracture strain of 1956%, and a compressive stress of 1905 kPa at 90% compressive strain.

[0017] Second, MUI has ionic conductivity. When the prepared polyionic liquid hydrogel is not immersed in the CaCl2 solution, the ionic conductivity can reach 32 mS / cm, and it can be further increased to 104 mS / cm after soaking in the CaCl2 solution. The good ionic conductivity provides favorable conditions for its application in wearable devices. Moreover, the imidazole ring in MUI carries a positive charge and can be quickly adsorbed to the bacteria (the cell wall or cell membrane is usually negatively charged), and the hydrophobic uracil group quickly embeds into the bacterial cell membrane and reassembles with phospholipid molecules, resulting in the rupture of the bacterial membrane and the leakage of cytoplasmic fluid, achieving the purpose of high-efficiency and long-lasting antibacterial. The polyionic liquid hydrogel of the present invention has antibacterial properties against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus.

[0018] Third, the introduction of CNFs increases the elastic modulus of the hydrogel, which effectively ensures the rapid recovery of the hydrogel during the stretching / compression process. The obtained hydrogel exhibits rapid recovery and excellent fatigue resistance after 200 cycles of 30%, 100%, and 500% tensile strain and 100 cycles of 20% and 50% compressive deformation. Based on the strong guarantee of the above mechanical properties, the hydrogel is further assembled into a wearable sensor. As a stress-strain type sensor, in the strain range of 1-1300%, the sensitivity (GF) of the hydrogel is as high as 11.84; as a compressive strain type sensor, under a stress of 0-50 kPa, the GF of the hydrogel is as high as 0.321 kPa. -1 The excellent sensitivity can efficiently monitor human movement.

[0019] The method of the present invention is used to prepare a highly stretchable, tough, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel; this polyionic liquid hydrogel is applied to the field of wearable sensors. Description of the Drawings

[0020] Figure 1 For the NMR spectrum of N-methyluracil-N-vinylimidazole chloride obtained in Step 1 of Example 1, where a is the 1 1H NMR spectrum, and b is the 13 13C NMR spectrum;

[0021] Figure 2 For the FTIR spectrum of N-methyluracil-N-vinylimidazole chloride obtained in Step 1 of Example 1;

[0022] Figure 3 For the tensile stress-strain test chart of the hydrogel prepared in Example 1;

[0023] Figure 4 Compressive stress-strain test diagram of the hydrogel prepared in Example 1;

[0024] Figure 5 Hydrogels P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ SEM diagrams of hydrogels P(Am-LMA-MUI) / CNF-Ca 2+ ;

[0025] Figure 6 Hydrogels P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Tensile fatigue resistance test diagrams of hydrogels P(Am-LMA-MUI) / CNF-Ca 2+ and P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca

[0026] Figure 7 Hydrogels P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Compressive fatigue resistance test diagrams of hydrogels P(Am-LMA-MUI) / CNF-Ca 2+ and P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca

[0027] Figure 8 Hydrogels P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Tensile recovery test diagrams of hydrogels P(Am-LMA-MUI) / CNF-Ca 2+ and P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca

[0028] Figure 9 Hydrogels P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Compressive recovery test diagrams of hydrogels P(Am-LMA-MUI) / CNF-Ca 2+ and P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca

[0029] Figure 10 Hydrogels P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Antibacterial activity test diagram;

[0030] Figure 11 Hydrogels P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+Cell viability test chart, where a is the control sample, b is P(Am-LMA), and c is P(Am-LMA-MUI) / CNF-Ca 2+ , and d is the relative viability chart;

[0031] Figure 12 The hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Sensitivity test chart, where a is P(Am-LMA-MUI) / CNF-Ca 2+ Tensile sensitivity, b is P(Am-LMA-MUI) / CNF-Ca 2+ Compression sensitivity, and c is the tensile sensitivity of P(Am-LMA-MUI). Detailed implementation method

[0032] Detailed implementation method 1: A preparation method of a highly stretchable, strong-toughness, fast-recovery, and fatigue-resistant polyionic liquid hydrogel is as follows:

[0033] I. Synthesis of functional, multi-functional ionic liquid monomers:

[0034] Add N-vinylimidazole and 6-chloromethyluracil to anhydrous methanol, displace with nitrogen until the system is clear and transparent, then heat to reflux. Wash the obtained white solid with anhydrous ethanol to obtain N-methyluracil-N-vinylimidazole chloride;

[0035] II. Preparation of a highly stretchable, strong-toughness, fast-recovery, and fatigue-resistant polyionic liquid hydrogel:

[0036] Mix sodium dodecyl sulfate, cellulose nanofibers, and water, stir until clear, then add lauryl methacrylate, stir to form a stable emulsion, add acrylamide and the N-methyluracil-N-vinylimidazole chloride prepared in step I, stir until clear, add an initiator, stir evenly, pour into a mold, and cure and copolymerize to obtain a hydrogel;

[0037] Soak the hydrogel in a CaCl2 solution to obtain the highly stretchable, strong-toughness, fast-recovery, and fatigue-resistant polyionic liquid hydrogel, and the preparation is completed.

[0038] Detailed implementation method 2: The difference between this implementation method and detailed implementation method 1 is that the molar ratio of N-vinylimidazole to 6-chloromethyluracil in step I is 1:(1 - 1.5). Others are the same as detailed implementation method 1.

[0039] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that in Step 2, the dosage of sodium dodecyl sulfate is 0.6 - 2.0 g, and the dosage of acrylamide is 2.84 - 4.26 g. Others are the same as Specific Embodiment 1 or 2.

[0040] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that in Step 2, the dosage of cellulose nanofibers is 0.5% - 3% of the mass of acrylamide. Others are the same as one of Specific Embodiments 1 to 3.

[0041] Specific Embodiment 5: The difference between this embodiment and one of Specific Embodiments 1 to 4 is that in Step 2, the dosage of lauryl methacrylate is 0.25% - 3% of the molar amount of acrylamide. Others are the same as one of Specific Embodiments 1 to 4.

[0042] Specific Embodiment 6: The difference between this embodiment and one of Specific Embodiments 1 to 5 is that after adding lauryl methacrylate in Step 2, stir for 1 - 10 h to form a stable emulsion. Others are the same as one of Specific Embodiments 1 to 5.

[0043] Specific Embodiment 7: The difference between this embodiment and one of Specific Embodiments 1 to 6 is that in Step 2, the dosage of N-methyluracil-N-vinylimidazole chloride is 10% - 30% of the mass of acrylamide. Others are the same as one of Specific Embodiments 1 to 6.

[0044] Specific Embodiment 8: The difference between this embodiment and one of Specific Embodiments 1 to 7 is that in Step 2, the initiator is potassium persulfate and tetramethylethylenediamine, the dosage of potassium persulfate is 0.1% - 1% of the mass of acrylamide, and the dosage of tetramethylethylenediamine is 0.1% - 1% of the mass of acrylamide. Others are the same as one of Specific Embodiments 1 to 7.

[0045] Specific Embodiment 9: The difference between this embodiment and one of Specific Embodiments 1 to 8 is that in Step 2, the curing temperature is 25 - 70 °C and the curing time is 3 - 24 h. Others are the same as one of Specific Embodiments 1 to 8.

[0046] Specific Embodiment 10: The difference between this embodiment and one of Specific Embodiments 1 to 9 is that in Step 2, the concentration of the CaCl₂ solution is 0.25 mol / L - 10 mol / L and soak for 1 - 10 h. Others are the same as one of Specific Embodiments 1 to 9.

[0047] The content of the present invention is not limited to the content of the above embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0048] Example 1:

[0049] This embodiment provides a method for preparing a polyionic liquid hydrogel with high tensile strength, high toughness, rapid recovery, and fatigue resistance, which is specifically carried out in the following steps:

[0050] 1. Synthesis of functional, multifunctional ionic liquid monomers:

[0051] 9.4 g of N-vinylimidazole and 20 g of 6-chloromethyluracil were added to 200 mL of anhydrous methanol, and the atmosphere was replaced with nitrogen until the system became clear and transparent. The mixture was then heated under reflux to obtain a white solid, which was washed with anhydrous ethanol to obtain N-methyluracil-N-vinylimidazole chloride (MUI).

[0052] MUI (yellow powder, yield: 85%): FTIR (v / cm -1 ):3119(-NH-),3098(Ar-H),3004(C=C),2843(CH),1761,1685(C=O),1640(C=C),1558(-NH-),1466,1373(CH). 1 H NMR(DMSO-d6,TMS)δ:11.33(s,1H,-C-NH-C=O),11.19(s,1H,-C=O-NH-C=O),9.63(s,1H,-N-CH-N),8.28(s,1H,-N-CH-CH),7.96(s,1H,-CH-C H-N), 7.39~7.34(q,1H,-N-CH=CH2), 6.01~5.97(d,1H,-CH=CH2), 5.51(s,1H,-CH=CH2), 5.46~5.44(d,1H,-C=CH-C=O), 5.26(s,2H,N-CH2-C). 13 C NMR (DMSO-d6, TMS) δ: 163.72 (=CC=O-NH), 151.18 (-NH-C=O-NH), 148.51 (-NH-C=CH), 136.81 (Ar-C), 128.9 5(CH2=CH-Ar), 123.53(Ar-C), 119.26(Ar-C), 108.96(CH2=CH-), 100.12(-C=CH-C=O), 48.27(Ar-CH2-C).

[0053] 2. Preparation of a high-strength, high-toughness, fast-recovery, and fatigue-resistant polyionic liquid hydrogel:

[0054] Mix 1.0 g of sodium dodecyl sulfate, 0.1 g of cellulose nanofibers and 20 mL of water, stir until clear, then add 300 μL of lauryl methacrylate, stir for 3 h to form a stable emulsion, add 3 g of acrylamide and 0.7 g of N-methyluracil-N-vinylimidazole chloride prepared in step one, stir until clear, then add 0.05 g of potassium persulfate and 40 mg of tetramethylethylenediamine, stir evenly at a stirring rate of 100 rpm, pour into a mold, cure at a temperature of 50 °C for 12 h, and cure and copolymerize to obtain a hydrogel;

[0055] Immerse the hydrogel in a CaCl2 solution with a concentration of 5 mol / L for 5 h to obtain the high-tensile, strong-toughness, fast-recovery, fatigue-resistant polyionic liquid hydrogel P(Am-LMA-MUI) / CNF-Ca 2+ , and the preparation is completed.

[0056] The properties of the hydrogel prepared in the present invention are compared with those of existing materials as follows:

[0057]

[0058] Figure 1 For the NMR spectrum of N-methyluracil-N-vinylimidazole chloride obtained in step one of Example 1, where a is 1 the 1H NMR spectrum, and b is 13 the 13C NMR spectrum;

[0059] Figure 2 For the FTIR spectrum of N-methyluracil-N-vinylimidazole chloride obtained in step one of Example 1.

[0060] Test the tensile properties and compression properties of the hydrogel prepared in Example 1 by a universal tensile machine. Tensile property test: All samples are cut into dumbbell shapes with a length of 30 mm, a test length of 12 mm, a width of 4 mm, and a thickness of 3 mm. All tensile tests are carried out at a constant tensile speed of 100 mm / min at room temperature. Compression experiment: The size of all samples to be tested is a cylinder with a diameter of 20 mm and a height of 15 mm. The compression speed is constant at 10 mm / min. Each of the above experiments is tested at least 5 times for each sample. For easy comparison, P(Am-LMA), P(Am-LMA-MUI), P(Am-LMA-MUI) / CNF, and P(Am-LMA-MUI) / CNF-Ca are prepared 2+ .

[0061] Figure 3 For the tensile stress-strain test chart of the hydrogel prepared in Example 1; Figure 4Compressive stress-strain test diagram of the hydrogel prepared in Example 1. It can be seen from the figure that with the addition of MUI and CNF, the mechanical properties of the hydrogel are enhanced, and P(Am-LMA-MUI) / CNF-Ca is prepared by soaking 2+ The mechanical properties of the hydrogel are higher than those of the unsoaked P(Am-LMA-MUI) / CNF. It shows that Ca 2+ is further involved in the network crosslinking, thus improving the mechanical properties.

[0062] Figure 5 SEM images of the hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ and the hydrogel P(Am-LMA-MUI), where a is P(Am-LMA-MUI) and b is P(Am-LMA-MUI) / CNF-Ca 2+ ; The internal morphology of the hydrogel was analyzed by scanning electron microscopy (SEM). Compared with the P(Am-LMA-MUI) hydrogel, P(Am-LMA-MUI) / CNF-Ca 2+ has obvious fibril structures between the voids, indicating that CNF participates in the construction of the hydrogel network, thus enhancing the mechanical properties.

[0063] The fatigue resistance of the prepared hydrogel was tested by a universal tensile machine. Tensile fatigue test: All samples were cut into dumbbell shapes with a length of 30 mm, a test length of 12 mm, a width of 4 mm, and a thickness of 3 mm. All tensile tests were carried out at room temperature at a constant tensile speed of 100 mm / min, and the fatigue resistance under 30%, 100%, and 500% strain conditions was tested. Compressive fatigue test: All samples to be tested were cylindrical with a diameter of 20 mm and a height of 15 mm. The compression speed was constant at 10 mm / min, and the fatigue resistance under 10% and 50% compressive strain conditions was tested. For easy comparison, P(Am-LMA) and P(Am-LMA-MUI) / CNF-Ca 2+ were prepared for comparison.

[0064] Figure 6 Tensile fatigue test diagrams of the hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ and the hydrogel P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca 2+ and b is P(Am-LMA); Due to the addition of MUI and CNF, P(Am-LMA-MUI) / CNF-Ca 2+It is possible to complete 200 cycle tests at 30%, 100%, and 500%. However, P(Am-LMA) can only complete 200 cycle tests at 30%. This indicates that P(Am-LMA-MUI) / CNF-Ca 2+ has good tensile fatigue resistance.

[0065] For P(Am-LMA-MUI) / CNF-Ca 2+ and P(Am-LMA), their compressive fatigue resistances were tested.

[0066] Figure 7 The hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ and the compressive fatigue test graph of the hydrogel P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca 2+ , b is P(Am-LMA); P(Am-LMA-MUI) / CNF-Ca 2+ The hydrogel can complete 100 cycle tests under 10% and 50% compressive deformations, while P(Am-LMA) can only complete 100 cycle tests under 10% compressive deformation.

[0067] The prepared hydrogel was tested for recovery by a universal tensile machine. Tensile recovery: The hydrogel was pre-stressed with a single load-unload tensile cycle. Then, it was placed for 0 min, 10 min, and 20 min respectively. The recovered hydrogel was subjected to a second stress load-unload cycle. Compressive recovery test: At 90% compressive strain, 10 consecutive load-unload cycles were performed. For easy comparison, P(Am-LMA) and P(Am-LMA-MUI) / CNF-Ca 2+ were prepared for comparison.

[0068] Figure 8 The hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ and the tensile recovery test graph of the hydrogel P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca 2+ , b is P(Am-LMA); It can be clearly seen that P(Am-LMA-MUI) / CNF-Ca 2+ can restore the tensile cycle area to 86% of the initial state after 20 min, while P(Am-LMA) needs 60 min to restore to 80% of the initial state. This indicates that P(Am-LMA-MUI) / CNF-Ca 2+ has rapid tensile recovery.

[0069] Compressive recovery test. Figure 9Hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ and the compression recovery test diagrams of hydrogel P(Am-LMA), where a is P(Am-LMA-MUI) / CNF-Ca 2+ , b is P(Am-LMA); it can be seen that after 10 consecutive loading-unloading cycles, the cyclic compression curves of P(Am-LMA-MUI) / CNF-Ca 2+ significantly overlap, indicating its excellent elasticity and rapid self-recovery. While the cyclic compression curve of P(Am-LMA) is significantly loose and the compressive stress drops significantly.

[0070] The antibacterial activities of the prepared hydrogels against Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC15224) and Bacillus subtilis (ATCC 15224) were tested by the inhibition zone method. The prepared agar medium, petri dishes and Oxford cups were sterilized in a pressure cooker at a pressure of 110 kPa and 110 °C for 30 min. After cooling to 45 °C, the agar medium was poured into the petri dishes, and 0.50 mL of the bacterial suspension (10 -6 ~10 -7 CFU·mL -1 ) was added to the petri dishes and evenly spread with a spreading rod. P(Am-LMA) and P(Am-LMA-MUI) / CNF-Ca with a diameter of 10 mm 2+ were placed on the agar medium, and the petri dishes were placed in an incubator at 37 °C for 24 hours. The size of the inhibition zone was observed. For easy comparison, P(Am-LMA) and P(Am-LMA-MUI) / CNF-Ca 2+ were prepared for comparison.

[0071] Figure 10 Hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Antibacterial activity test diagram; it can be clearly seen that P(Am-LMA-MUI) / CNF-Ca 2+ has antibacterial activities against Staphylococcus aureus, Escherichia coli and Bacillus subtilis, while P(Am-LMA) does not have antibacterial activity due to the absence of the MUI component.

[0072] The cytotoxicity of the prepared hydrogels to mouse fibroblasts was tested by the CCK-8 method to analyze their biocompatibility. The L929 mouse fibroblasts were revived and prepared into a suspension. Take 200 μL of the cell suspension (5×10 5(cells / mL), pipette it into a 96-well plate and incubate for 24 h. Take 30 mg of sterile hydrogel (the hydrogel is first freeze-dried and sterilized under ultraviolet light for 3 h, and then impregnated in α-MEM cell culture medium for 24 h until completely swollen) and place it in the above-mentioned well plate. Place the whole system in a 37 °C and 5% CO2 cell incubator and culture for 24 h, and observe the cell growth situation under a 20-fold microscope at any time. Use the sample without hydrogel as the control group. All experiments are in 5 replicates. For easy comparison, P(Am-LMA) and P(Am-LMA-MUI) / CNF-Ca are prepared 2+ for comparison.

[0073] Figure 11 The hydrogel P(Am-LMA-MUI) / CNF-Ca prepared in Example 1 2+ Cell viability test diagram, where a is the control sample, b is P(Am-LMA), c is P(Am-LMA-MUI) / CNF-Ca 2+ , d is the relative activity diagram; it can be seen from the figure that the L929 cell morphologies of the samples to be tested and the control sample are both spindle-shaped. In addition, within the entire microscope field of view, the number of L929 cells in the two samples does not decrease much compared to the control sample. Moreover, the cell viabilities of P(Am-LMA) and P(Am-LMA-MUI) / CNF-Ca 2+ are 95% and 91% respectively. The results show that the introduction of MUI has a certain impact on cell growth, but P(Am-LMA-MUI) / CNF-Ca 2+ hydrogel still has good cell compatibility overall. The excellent biocompatibility of P(Am-LMA-MUI) / CNF-Ca 2+ hydrogel provides a guarantee for long-term skin monitoring.

[0074] The universal tensile machine and bench multimeter are used to test the sensing performance of the hydrogel. First, fix the hydrogel on the universal tensile machine, and at the same time connect both ends of the hydrogel to the bench multimeter, and record the change curve of the resistance of the hydrogel with strain through the bench multimeter. The slope of the obtained resistance-strain curve is defined as the gauge factor (GF). The change in resistance is obtained by the following formula (1):

[0075] ΔR / R0 = (R - R0) / R0 (1)

[0076] where R0 and R are the resistance of the hydrogel without applying strain and the resistance of the hydrogel after applying strain, respectively. For easy comparison, P(Am-LMA), P(Am-LMA-MUI) and P(Am-LMA-MUI) / CNF-Ca are prepared 2+ for comparison.

[0077] Figure 12The hydrogel P(Am-LMA-MUI) / CNF-Ca prepared for Example 1 2+ Sensitivity test chart, where a is the tensile sensitivity of P(Am-LMA-MUI) / CNF-Ca 2+ and b is the compressive sensitivity of P(Am-LMA-MUI) / CNF-Ca 2+ and c is the tensile sensitivity of P(Am-LMA-MUI);

[0078] It can be seen that due to the introduction of MUI, P(Am-LMA-MUI) / CNF-Ca 2+ and P(Am-LMA-MUI) endow the hydrogel with ionic conductivity. P(Am-LMA) does not have ionic conductivity and thus does not have sensing performance. And P(Am-LMA-MUI) / CNF-Ca 2+ prepared by a two-step method has significantly improved ionic conductivity, and its sensitivity as stress-strain is significantly higher than that of P(Am-LMA-MUI) (i.e., GF = 11.84, GF = 7.27). And P(Am-LMA-MUI) / CNF-Ca 2+ introduces CNF, and its mechanical properties are enhanced and it can be used as a compressive strain sensor, which P(Am-LMA-MUI) does not have.

Claims

1. A preparation method of a high-tensile, strong-toughness, fast-recovery, fatigue-resistant polyionic liquid hydrogel, characterized in that The method is specifically carried out according to the following steps: I. Synthesis of functional and multi-functional ionic liquid monomers: N-vinylimidazole and 6-chloromethyluracil are added to anhydrous methanol. The system is purged with nitrogen until it is clear and transparent, and then heated under reflux. The obtained white solid is washed with anhydrous ethanol to obtain N-methyluracil-N-vinylimidazole chloride; II. Preparation of a highly stretchable, tough, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel: Sodium dodecyl sulfate, cellulose nanofibers, and water are mixed and stirred until clear. Then, lauryl methacrylate is added and stirred to form a stable emulsion. Acrylamide and the N-methyluracil-N-vinylimidazole chloride prepared in step I are added and stirred until clear. Then, an initiator is added and stirred evenly. The mixture is poured into a mold and cured by copolymerization to obtain a hydrogel; The hydrogel is soaked in a CaCl2 solution to obtain the highly stretchable, tough, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel, and the preparation is completed; In step II, the dosage of cellulose nanofibers is 0.5% - 3% of the mass of acrylamide; In step II, the dosage of N-methyluracil-N-vinylimidazole chloride is 10% - 30% of the mass of acrylamide; In step II, the initiator is potassium persulfate and tetramethylethylenediamine. The dosage of potassium persulfate is 0.1% - 1% of the mass of acrylamide, and the dosage of tetramethylethylenediamine is 0.1% - 1% of the mass of acrylamide.

2. The preparation method of a highly stretchable, strong-toughness, rapid-recovery, fatigue-resistant polyionic liquid hydrogel according to claim 1, characterized in that In step I, the molar ratio of N-vinylimidazole to 6-chloromethyluracil is 1:(1 - 1.5).

3. The preparation method of a highly stretchable, strong and tough, rapidly recoverable, and fatigue-resistant polyionic liquid hydrogel according to claim 1, characterized in that In step II, the dosage of sodium dodecyl sulfate is 0.6 - 2.0 g, and the dosage of acrylamide is 2.84 - 4.26 g.

4. The preparation method of a highly stretchable, strong toughness, rapid recovery, and fatigue-resistant polyionic liquid hydrogel according to claim 1, wherein In step II, the dosage of lauryl methacrylate is 0.25% - 3% of the molar amount of acrylamide.

5. The preparation method of a highly stretchable, strong-toughness, rapid-recovery, fatigue-resistant polyionic liquid hydrogel according to claim 1, characterized in that In step II, after adding lauryl methacrylate, it is stirred for 1 - 10 h to form a stable emulsion.

6. The preparation method of a highly stretchable, strong and tough, quickly recoverable, fatigue-resistant polyionic liquid hydrogel according to claim 1, characterized in that In step II, the curing temperature is 25 - 70 °C, and the curing time is 3 - 24 h.

7. The preparation method of a highly stretchable, strong and tough, fast-recovering, fatigue-resistant polyionic liquid hydrogel according to claim 1, characterized in that In step II, the concentration of the CaCl2 solution is 0.25 mol / L - 10 mol / L, and the soaking time is 1 - 10 h.

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