Rapid preparation method and application of renewable polyion liquid hydrogel with high mechanical property and low temperature resistance

Abstract

The invention discloses a rapid preparation method and application of high-mechanical-property, low-temperature-resistant and renewable polyion liquid hydrogel, and relates to the field of preparation and application of polyion liquid hydrogel. The invention aims to solve the technical problems of complex preparation process, poor mechanical property, low temperature resistance and non-regeneration of hydrogel. The method comprises the following steps: synthesizing an ionic liquid monomer with a zwitter-ion unit structure; synthesizing an ionic liquid monomer with an amphiphilic long-chain structure; and copolymerizing to prepare the renewable polyion liquid hydrogel with high mechanical property and low temperature resistance. The introduction of the functionalized ionic liquid monomer not only realizes the improvement of mechanical properties, but also effectively improves the conductivity and low temperature resistance of the gel. The polyion liquid hydrogel prepared by the method is applied to the field of low-temperature-resistant renewable hydrogel strain sensors.

Description

Technical Field

[0001] The invention relates to the preparation of polyionic liquid hydrogel and the application field thereof. Background Art

[0002] In recent years, wearable devices have developed rapidly in the fields of electronic skin, soft robots, and human-machine interfaces, and have attracted much attention. However, due to the softness and deformability of human skin, it is difficult for traditional rigid skin electrodes to fit completely on the surface of human tissue, which greatly limits the effective monitoring of electronic devices and the human body. Wearable electronic devices based on elastic polymer materials have attracted much attention due to their simple structure and easy signal reading. However, these devices have defects such as complex manufacturing process, extremely high price, and poor dynamic performance in wearable applications. Therefore, the development of a flexible sensor with excellent comprehensive performance, low cost, and simple process is of great significance to the further development of wearable electronic devices.

[0003] Conductive 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, it has been widely used in popular fields such as wearable electronic devices, flexible energy storage materials, electronic skin and tissue repair. However, as a matrix material for flexible wearable devices, conductive hydrogel still has the following problems: ① The preparation process is complicated; ② It is difficult to achieve a balance between toughness and durability; ③ Due to the presence of a large amount of water in the three-dimensional network structure, the tolerance to the environment is poor (i.e., it hardens as the water evaporates and freezes at temperatures below zero), and the dry and hard hydrogel is difficult to achieve self-regeneration; ④ Due to the increase in the density of the internal cross-linked network, the conductive performance decreases. Therefore, it is still challenging to prepare a conductive hydrogel material with excellent comprehensive performance. Summary of the invention

[0004] The present invention aims to solve the technical problems of complex hydrogel preparation process, poor mechanical properties, low temperature resistance and non-renewability, and provide a rapid preparation method and application of polyionic liquid hydrogel with high mechanical properties, low temperature resistance and renewability.

[0005] The present invention aims to utilize the structural designability of ionic liquids to synthesize two ionic liquid monomers with amphiphilic long-chain structures and zwitterionic unit structures, and realize the rapid preparation of hydrogels by in-situ polymerization with traditional monomers at room temperature. Among them, the amphiphilic long-chain structure ionic liquid monomer induces cellulose nanofibers to be oriented, and forms a microscopic anisotropic structure after polymerization. In addition, there are significant non-covalent bond interactions in the constructed network, which gives the polyionic liquid hydrogel excellent mechanical properties. Due to the introduction of zwitterionic units (i.e., imidazole cations and sulfonate anions) and lithium chloride with high hydration capacity into the polymer, the hydrogel has high strain response behavior, excellent antifreeze and good self-regeneration ability. Based on these excellent properties, the polyionic liquid hydrogel can be used as a flexible strain sensor, showing high sensitivity and rapid response in monitoring human body movement and subtle physiological signals.

[0006] 2,2,6,6-Tetramethyl-1-oxypiperidinyl oxidized cellulose nanofibers (CNFs) are natural biopolymer cellulose nanofibers isolated from wood. Due to their fiber entanglement and large aspect ratio, they can be used as an effective reinforcing material for preparing strong hydrogels. CNFs have high dispersion stability due to their surface negative charge and multiple hydroxyl structures, and can effectively interact with hydrophilic polymers to increase the crosslinking density of hydrogels. In addition, excellent hydrogel sensors should have multifunctionality (such as high conductivity, excellent low temperature resistance, and rapid self-regeneration ability), which can not only improve sensitivity but also extend the operating temperature range and service life. Polyionic liquid hydrogel is a polymer formed by the polymerization of ionic liquid monomers and other monomers, which has high ionic conductivity and a wide electrochemical window. The present invention adjusts its physical properties by changing the structure of ionic liquid monomers. Ionic liquids with amphoteric structures are conducive to the lowering of the freezing point of water after polymerization; ionic liquids containing long alkyl groups are similar to cationic quaternary ammonium salt surfactants, which can self-assemble in water to induce the stacking morphology of nanomaterials. The introduction of functionalized ionic liquid monomers not only improves the mechanical properties, but also effectively improves the conductivity and low-temperature resistance of the gel.

[0007] A rapid preparation method of a polyionic liquid hydrogel with high mechanical properties, low temperature resistance and reproducibility is specifically carried out in the following steps:

[0008] 1. Synthesis of ionic liquid monomer (1-propyl-3-vinyl imidazole sulfonate) with zwitterionic unit structure:

[0009] N-vinylimidazole, 1,3-propanesultone and dichloromethane were added into a three-necked flask, and heated under reflux for 10 to 72 hours under nitrogen atmosphere to obtain a white powder, and the white powder was washed and dried to obtain 1-propyl-3-vinylimidazole sulfonate (ZILs);

[0010] The synthesis of 1-propyl-3-vinyl imidazole sulfonate is as follows:

[0011]

[0012] 2. Synthesis of ionic liquid monomer (N-hexadecyl-N-vinyl imidazolium bromide) with amphiphilic long chain structure:

[0013] Add N-vinylimidazole, hexadecane bromide and acetonitrile into a three-necked flask, heat and reflux for 24 to 96 hours under a nitrogen atmosphere to obtain a white solid, wash the white solid, and dry it to obtain N-hexadecyl-N-vinylimidazole bromide (C16Br);

[0014] The synthesis of N-hexadecyl-N-vinyl imidazolium bromide is as follows:

[0015]

[0016] 3. Add lithium chloride to the 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofiber solution, stir until dissolved, then cool to room temperature, add acrylamide (Am), 1-propyl-3-vinylimidazole sulfonate obtained in step one and N-hexadecyl-N-vinylimidazole bromide obtained in step two and stir, then add ammonium persulfate (APS), N,N′-methylenebisacrylamide (MBA) and N,N,N',N'-tetramethylethylenediamine (TMEDA), stir to form a uniform mixed solution; immediately transfer the mixed solution to a mold, copolymerize at room temperature to obtain the high mechanical properties, low temperature resistance and renewable polyionic liquid hydrogel, namely P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel, and complete the preparation.

[0017] Beneficial effects of the present invention:

[0018] First, the introduction of chemical crosslinking agent (MBA) effectively improved the crosslinking points of the network, and copolymerization with Am, ZILs and C16Br further increased the crosslinking density. At the same time, CNFs, as a reinforcing nanomaterial, also participated in the construction of the crosslinked network. Therefore, the formed strong and tough crosslinked network successfully endowed the prepared hydrogel with excellent mechanical properties (i.e., high strength, high tensile strength, tear resistance, puncture resistance and mechanical durability).

[0019] Second, from a microscopic perspective, the self-assembly of C16Br in the solution causes CNFs to be arranged in a direction in the precursor solution, and other monomers rely on non-covalent forces to attach to the surface of CNFs for in-situ polymerization. The arrangement of these fiber polymers inside the hydrogel forms a microscopic anisotropic structure similar to human muscle tissue, which significantly improves the mechanical properties of the polyionic liquid hydrogel.

[0020] Third, the interaction between the charge dipole and dipole-dipole of the introduced zwitterionic units (i.e., imidazolium cations and sulfonate anions), as well as the synergistic effect with the highly hydrating LiCl, make the hydrogel have good low-temperature resistance, water retention and self-regeneration ability. At the same time, the conductivity and strain response behavior of the hydrogel can also be improved. The hydrogel is assembled into a strain sensor. In the strain range of 1 to 1400%, the sensitivity (GF) of the hydrogel at -20°C and 25°C is as high as 12.3 and 16.6, respectively, and it can effectively monitor human body movement.

[0021] Fourth, by adjusting the content of initiator and cross-linker, the rapid preparation of polyionic liquid hydrogel can be achieved at room temperature. This method is simple, efficient and highly controllable, providing a new idea for the rapid preparation of low-temperature resistant and regenerable hydrogel sensors.

[0022] The polyionic liquid hydrogel prepared by the invention is used in the field of low-temperature-resistant and regenerable hydrogel strain sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The NMR spectrum of 1-propyl-3-vinyl imidazole sulfonate prepared in Example;

[0024] Figure 2 The NMR spectrum of N-hexadecyl-N-vinyl imidazolium bromide prepared in Example;

[0025] Figure 3 The mechanical properties test diagram of the polyionic liquid hydrogel prepared in the embodiment; Figure a is the tensile properties, and Figure b is the compressive properties;

[0026] Figure 4 The SEM images of the internal morphology of various polyionic liquid hydrogels, wherein Figure a is a P(Am-ZILs)-LiCl hydrogel, Figure b is a P(Am-ZILs) / CNFs-LiCl hydrogel, Figure c is a polyionic liquid hydrogel prepared in Example, and Figure d is a partial enlarged view of Figure c;

[0027] Figure 5 The tear resistance and puncture resistance performance diagrams of the polyionic liquid hydrogel prepared in the example; Figure a is a puncture resistance performance diagram, and Figure b is a tear resistance performance diagram;

[0028] Figure 6 The tensile mechanical durability test diagram of polyionic liquid hydrogel prepared for the example;

[0029] Figure 7 This is a test chart of low temperature resistance of various polyionic liquid hydrogels;

[0030] Figure 8 The weight ratio change diagram of the polyionic liquid hydrogel prepared in the dehydration example at different times when placed in an environment of 25° C. and 54% relative humidity;

[0031] Fig. 9 The sensitivity coefficient test graph of the polyionic liquid hydrogel prepared for the example at -20°C and 25°C. DETAILED DESCRIPTION

[0032] Specific implementation method 1: This implementation method is a rapid preparation method of a polyionic liquid hydrogel with high mechanical properties, low temperature resistance and reproducibility, which is specifically carried out in the following steps:

[0033] 1. Add N-vinylimidazole, 1,3-propanesultone and dichloromethane into a three-necked flask, heat and reflux for 10 to 72 hours under a nitrogen atmosphere to obtain a white powder, wash the white powder, and dry it to obtain 1-propyl-3-vinylimidazole sulfonate;

[0034] 2. Add N-vinylimidazole, hexadecane bromide and acetonitrile into a three-necked flask, heat and reflux for 24 to 96 hours under a nitrogen atmosphere to obtain a white solid, wash the white solid, and dry it to obtain N-hexadecyl-N-vinylimidazole bromide;

[0035] 3. Add lithium chloride to the 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofiber solution, stir until dissolved, then cool to room temperature, add acrylamide, 1-propyl-3-vinylimidazole sulfonate obtained in step one and N-hexadecyl-N-vinylimidazole bromide obtained in step two and stir, then add ammonium persulfate, N,N′-methylenebisacrylamide and N,N,N',N'-tetramethylethylenediamine, stir to form a uniform mixed solution; immediately transfer the mixed solution to a mold, copolymerize at room temperature to obtain the high mechanical properties, low temperature resistance and renewable polyionic liquid hydrogel, namely P(Am-ZILs-C16Br) / CNFs-LiCl, to complete the preparation.

[0036] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the molar ratio of N-vinylimidazole to 1,3-propane sultone in step 1 is (0.5-1):(1-1.5). Others are the same as specific embodiment 1.

[0037] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: in step 1, nitrogen is used to replace the system with a nitrogen atmosphere. The rest is the same as specific implementation method 1 or 2.

[0038] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that dichloromethane is used for washing in step 1. The rest is the same as specific embodiments 1 to 3.

[0039] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the molar ratio of N-vinylimidazole to hexadecane bromide in step 2 is (0.5-1):(1-1.5). Others are the same as specific embodiments 1 to 4.

[0040] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that: in step 2, nitrogen is used to replace the system with a nitrogen atmosphere. The rest is the same as specific embodiments 1 to 5.

[0041] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that ethyl acetate is used for washing in step 2. The rest is the same as specific embodiments 1 to 6.

[0042] Specific embodiment eight: This embodiment is different from specific embodiments one to seven in that: the mass of 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofibers in the 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofiber solution in step three is 0.5% to 5% of the mass of acrylamide; the amount of lithium chloride is 5 to 35% of the mass of acrylamide; the amount of 1-propyl-3-vinyl imidazole sulfonate is 5% to 30% of the mass of acrylamide; the amount of N-hexadecyl-N-vinyl imidazole bromide is 10% to 40% of the mass of acrylamide; the amount of ammonium persulfate is 1‰ to 5% of the mass of acrylamide; the amount of N,N′-methylenebisacrylamide is 2‰ to 7% of the mass of acrylamide; the amount of N,N,N',N'-tetramethylethylenediamine is 5μL to 40μL. Others are the same as specific embodiments one to seven.

[0043] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that the copolymerization time in step 3 is controlled to be 2 min to 10 min. The rest is the same as specific embodiments 1 to 8.

[0044] Specific implementation method ten: This implementation method is an application of a polyionic liquid hydrogel with high mechanical properties, low temperature resistance and renewability. The polyionic liquid hydrogel with high mechanical properties, low temperature resistance and renewability is applied as a matrix material to a flexible strain sensor.

[0045] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0046] Example:

[0047] This embodiment provides a method for rapidly preparing a polyionic liquid hydrogel with high mechanical properties, low temperature resistance and reproducibility, which is specifically carried out in the following steps:

[0048] 1. Add N-vinylimidazole, 1,3-propane sultone and dichloromethane into a three-necked flask, wherein the molar ratio of N-vinylimidazole to 1,3-propane sultone is (0.5-1):(1-1.5), heat and reflux for 10-72 hours under nitrogen atmosphere to obtain a white powder, wash the white powder three times with dichloromethane, and dry it in a vacuum oven at 50° C. for 12 hours to obtain 1-propyl-3-vinylimidazole sulfonate (ZILs); ZILs (white powder, yield 87%): 1 H NMR (D 2 O)δ:8.99(s,1H,-N-CH-N),7.70(s,1H,-N-CH-CH),7.53(s,1H,-CH-CH-N),7.07~7.03(q,1H,-N-CH=CH 2 ),5.72~5.70(d,1H,-CH=CH 2 ),5.34(s,1H,-CH=CH 2 ),4.33(t,2H,Ar-CH 2 -),2.86(t,2H,-CH 2 -SO 3 - ),2.24(q,2H,-CH 2 -CH 2 -CH 2 ). 13 C NMR (D 2 O)δ:134.70(Ar-C),128.18(CH 2 =CH-Ar),122.80(Ar-C),119.62(Ar-C),109.40(CH 2 =CH-),48.09(-CH 2 -SO 3 - ),47.17(Ar-CH 2 -),24.95(Ar-CH 2 -CH 2 -).;

[0049] 2. Add N-vinylimidazole, hexadecane bromide and acetonitrile into a three-necked flask, wherein the molar ratio of N-vinylimidazole to hexadecane bromide is (0.5-1):(1-1.5), and heat under reflux for 24-96 hours under nitrogen atmosphere to obtain a white solid. Wash the white solid three times with ethyl acetate, and dry it in a vacuum oven at 50°C for 12 hours to obtain N-hexadecyl-N-vinylimidazole bromide (C16Br), C16Br (white powder, yield 87%): 1 H NMR (CDCl 3 )δ:10.87(s,1H,-N-CH-N),8.004(s,1H,-N-CH-CH),7.645(s,1H,-CH-CH-N),7.538~7.498(q,1H,-N-CH=CH 2 ),6.035(d,1H,-CH=CH 2 ),5.404(d,1H,-CH=CH 2 ),4.41(t,2H,Ar-CH 2 -),1.969(t,2H,-Ar-CH 2 -CH 2 ),1.243(q,26H,-C 13 H 26 -CH 3 ),0.877(t,3H,-C 13 H 26 -CH 3 ). 13 CNMR (CDCl 3 )δ:135.90~135.79(Ar-C),128.29(CH 2 =CH-Ar),122.74(Ar-C),119.51(Ar-C),109.78(CH 2 =CH-), 50.46(Ar-CH 2 -),31.922~14.146(Ar-C 2 H 4 -C 13 H 27 ).;

[0050] 3. Add lithium chloride (LiCl) and water to the 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofiber solution (CNFs), stir until dissolved, then cool to room temperature, add acrylamide (Am), 1-propyl-3-vinylimidazole sulfonate (ZILs) obtained in step one and N-hexadecyl-N-vinylimidazole bromide (C16Br) obtained in step two, and stir rapidly until completely dissolved, then add ammonium persulfate (APS), N,N′-methylenebisacrylamide (MBA) and N,N,N',N'-tetramethylethylenediamine (TMEDA), and stir vigorously to form a uniform mixed solution; immediately transfer the mixed solution to a mold, copolymerize at room temperature for 2min to 10min, and obtain the high mechanical properties, low temperature resistance and renewable polyionic liquid hydrogel, namely P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel, to complete the preparation.

[0051] The amount of acrylamide used in step 3 is 2.84g to 10.65g; the mass of 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofibers in the 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofiber solution is 0.5% to 5% of the mass of acrylamide; the amount of lithium chloride used is 5 to 35% of the mass of acrylamide; the amount of water used is 5mL to 40mL; the amount of 1-propyl-3-vinyl imidazole sulfonate is 5% to 30% of the mass of acrylamide; the amount of N-hexadecyl-N-vinyl imidazole bromide is 10% to 40% of the mass of acrylamide; the amount of ammonium persulfate is 1‰ to 5% of the mass of acrylamide; the amount of N,N′-methylenebisacrylamide is 2‰ to 7% of the mass of acrylamide; the amount of N,N,N',N'-tetramethylethylenediamine is 5μL to 40μL.

[0052] The hydrogel prepared in the embodiment was tested for its tensile and compressive properties by a universal material testing machine. Tensile performance test: All samples were cut into dumbbell shapes with 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. Compression test: The size of all samples to be tested was cylindrical with a diameter of 20 mm and a height of 15 mm. The compression speed was constant at 10 mm / min, and the compression stress was evaluated by a compression deformation of 90%. Each sample in the above experiment was tested at least 5 times. P(Am)-LiCl hydrogel, P(Am-ZILs)-LiCl hydrogel, P(Am-ZILs) / CNFs-LiCl hydrogel and P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel were prepared at the same time for comparison. Figure 3 It is shown that with the addition of CNFs and C16Br, the tensile stress of polyionic liquid hydrogel ( Figure 3 a) and compressive stress ( Figure 3 b) gradually increased. Especially after the introduction of C16Br, the tensile stress and compressive stress of the hydrogel reached 2199 kPa and 3257 kPa respectively.

[0053] In order to verify the relationship between microstructure and macroscopic mechanical properties, the internal morphology of the hydrogel was analyzed by scanning electron microscopy (SEM). Figure 4 It can be seen that compared with P(Am-ZILs)-LiCl hydrogel, there is an obvious fiber structure in the gaps of P(Am-ZILs) / CNFs-LiCl hydrogel, indicating that CNFs participate in the construction of the hydrogel network. However, after C16Br participates in the polymerization, due to its amphiphilicity, it can self-assemble in the prepolymer solution, and other monomers rely on non-covalent forces to attach to the surface of CNFs for in-situ polymerization. The arrangement of these fiber polymers inside the hydrogel forms a microscopic anisotropic structure similar to human muscle tissue, which further improves the tensile strength of the hydrogel.

[0054] The hydrogel prepared in the example was tested for tear resistance and puncture resistance by a universal material testing machine. The puncture strength test was performed using a steel needle with a tip of 0.5 mm to puncture the sample (40×40 mm 2 ). The fracture energy of the hydrogel during tearing was tested by single-edge notch tensile test. Two rectangular samples of the same size (20 mm long and 10 mm wide) were used, one of which had a prefabricated notch (3 mm) in the middle of one side for measuring the fracture energy. The distance between the two clamps was fixed at 15 mm, and the tensile speed was maintained at 20 mm / min. Each sample in the above experiment was tested at least 5 times.

[0055] Obtained through testing Figure 5 The hydrogel exhibited excellent puncture resistance and a toughness of 4.18 MJ / m 3 In addition, the polyionic liquid hydrogel exhibited excellent crack insensitivity during stretching, with a maximum fracture strain of 1061% and a fracture energy of 3.13 kJ / m 2 , higher than human cartilage (~1.0kJ / m 2 ) and human skin (1.7~2.6kJ / m 2 ). The tearing / puncture resistance of the polyion hydrogel prepared by the present invention is better than that of most reported hydrogels.

[0056] The hydrogel prepared in the example was tested for tensile mechanical durability by a universal material testing machine. The specific test process is as follows: All samples were cut into dumbbell shapes with a test length of 12 mm, a width of 4 mm, and a thickness of 3 mm. All tensile tests were performed at room temperature at a constant tensile speed of 100 mm / min to test the tensile mechanical durability under 500% strain conditions. Figure 6 The results showed that the polyionic liquid hydrogel could complete 200 cycle tests at 500%, indicating that the gel had excellent tensile mechanical durability.

[0057] The low temperature resistance of the polyionic liquid hydrogel sample prepared in the example was measured by differential scanning calorimetry (DSC). The specific test process is as follows: 30 mg of the hydrogel sample was weighed and placed in a dry pot at N 2 The temperature was lowered at a rate of -5°C / min under atmosphere, and the heat absorption and release in the temperature range of -60 to 40°C were investigated. P(Am) / CNFs hydrogel, P(Am-ZILs) / CNFs hydrogel, P(Am-ZILs-C16Br) / CNFs hydrogel and P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel were prepared for comparison.

[0058] Figure 7 It can be seen that during the cooling process in the range of 40 to -60°C, the exothermic peaks of the hydrogels of different components gradually decreased, indicating that the two ionic liquid monomers and LiCl introduced in the present invention can effectively reduce the freezing point of the hydrogel. In addition, the freezing point of the P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel is -46.9°C, showing excellent low temperature resistance.

[0059] The dehydrated polyionic liquid hydrogel was placed in an environment of 25°C and 54% relative humidity, and its regeneration performance was evaluated by recording the mass at different times. The specific test process is as follows: the hydrogel was placed in a 60°C vacuum drying oven for 4 hours, and then placed in a constant temperature and humidity mold incubator to observe whether the structure of the dehydrated gel can be regenerated, and the mass of the hydrogel was recorded at regular intervals during the period. At the same time, P(Am-ZILs-C16Br) / CNFs hydrogel and P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel were prepared for comparison.

[0060] Figure 8 It shows that under the environment of 25°C and 54% relative humidity, the mass of P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel dried with the introduction of LiCl also increases with time, indicating that the introduction of LiCl regenerates the P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel.

[0061] The strain sensing performance of the hydrogel was tested by combining a universal material testing machine and a desktop multimeter. First, the hydrogel was fixed on the universal material testing machine, and at the same time, both ends of the hydrogel were connected to the desktop multimeter, and the resistance of the hydrogel was recorded by the desktop multimeter. The slope of the obtained resistance-strain curve was defined as the sensitivity factor (GF). The change in resistance was obtained by the following formula (1):

[0062]

[0063] Where R 0 and R are the resistance of the hydrogel when no strain is applied and the resistance of the hydrogel after strain is applied, respectively.

[0064] Fig. 9 It can be seen that the P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel has excellent ionic conductivity due to the introduction of ZILs, C16Br and LiCl, and exhibits excellent sensitivity as a strain sensor under low temperature and room temperature conditions (i.e., GF=16.6 (25°C), GF=12.3 (-20°C)).

[0065] The performance of the P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel prepared by the present invention is compared with the existing reported hydrogel sensors, as shown in Table 1:

[0066] Table 1

[0067]

[0068]

[0069] It can be seen from Table 1 that the P(Am-ZILs-C16Br) / CNFs-LiCl hydrogel prepared in the present invention has excellent performance, which has exceeded the existing reported hydrogel sensors.

Claims

1. A rapid preparation method of a polyionic liquid hydrogel with high mechanical properties, low temperature resistance and reproducibility, characterized in that The method is specifically carried out in the following steps:

1. Add N-vinylimidazole, 1,3-propanesultone and dichloromethane into a three-necked flask, heat and reflux for 10 to 72 hours under a nitrogen atmosphere to obtain a white powder, wash the white powder, and dry it to obtain 1-propyl-3-vinylimidazole sulfonate; 2. Add N-vinylimidazole, hexadecane bromide and acetonitrile into a three-necked flask, heat and reflux for 24 to 96 hours under a nitrogen atmosphere to obtain a white solid, wash the white solid, and dry it to obtain N-hexadecyl-N-vinylimidazole bromide; 3. Add lithium chloride to the 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofiber solution, stir until dissolved, then cool to room temperature, add acrylamide, 1-propyl-3-vinylimidazole sulfonate obtained in step one and N-hexadecyl-N-vinylimidazole bromide obtained in step two and stir, then add ammonium persulfate, N,N′-methylenebisacrylamide and N,N,N',N'-tetramethylethylenediamine, stir to form a uniform mixed solution; immediately transfer the mixed solution to a mold, copolymerize at room temperature to obtain the high mechanical properties, low temperature resistance and renewable polyionic liquid hydrogel, namely P(Am-ZILs-C16Br) / CNFs-LiCl, to complete the preparation.

2. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that In step 1, the molar ratio of N-vinylimidazole to 1,3-propanesultone is (0.5-1):(1-1.5).

3. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that Step 1: Use nitrogen to replace the system with a nitrogen atmosphere.

4. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that Step 1 is washed with dichloromethane.

5. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that In step 2, the molar ratio of N-vinylimidazole to hexadecane bromide is (0.5-1):(1-1.5).

6. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that Step 2: Use nitrogen to replace the system with a nitrogen atmosphere.

7. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that Step 2: washing with ethyl acetate.

8. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that In the 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofiber solution of step 3, the mass of 2,2,6,6-tetramethyl-1-oxypiperidinyl oxidized cellulose nanofibers is 0.5% to 5% of the mass of acrylamide; the amount of lithium chloride is 5 to 35% of the mass of acrylamide; the amount of 1-propyl-3-vinyl imidazole sulfonate is 5 to 30% of the mass of acrylamide; the amount of N-hexadecyl-N-vinyl imidazole bromide is 10 to 40% of the mass of acrylamide; the amount of ammonium persulfate is 1‰ to 5% of the mass of acrylamide; the amount of N,N′-methylenebisacrylamide is 2‰ to 7% of the mass of acrylamide; and the amount of N,N,N',N'-tetramethylethylenediamine is 5 μL to 40 μL.

9. The method for rapidly preparing a polyionic liquid hydrogel having high mechanical properties, low temperature resistance and reproducibility according to claim 1, characterized in that In step three, the copolymerization time is controlled to be 2 min to 10 min.

10. The use of a polyionic liquid hydrogel with high mechanical properties, low temperature resistance and reproducibility prepared as claimed in claim 1, characterized in that The polyionic liquid hydrogel with high mechanical properties, low temperature resistance and regenerative properties is applied as a matrix material to a flexible strain sensor.

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