Anti-freezing sodium polyacrylate-based ionic conductive hydrogel and preparation method thereof

Abstract

The preparation method comprises the following steps: S1, adding acrylic acid into deionized water, and adding sodium hydroxide under an ice-water bath condition, so as to obtain a sodium acrylate solution; s2, adding strong electrolyte into deionized water, and performing ultrasonic dispersion to obtain strong electrolyte dispersion liquid (1); s3, mixing an anti-freezing agent (2) with a sodium acrylate solution and the strong electrolyte dispersion liquid (1), and performing ultrasonic dispersion to form a uniform mixed liquid (3); s4, adding a chemical cross-linking agent (4) into the mixed solution (3), stirring and dissolving, adding an initiator (5) and an accelerant (6), and uniformly stirring to obtain a hydrogel pre-polymerization solution (7); and S5, injecting the pre-polymerization liquid (7) into a mold, and carrying out free radical polymerization to prepare the conductive hydrogel. By introducing the strong electrolyte, the hydrogel is endowed with excellent conductivity, the conductivity reaches 2.3 S / m at the temperature of-27 DEG C, meanwhile, good flexibility is kept, and the application range of the hydrogel in a low-temperature environment is widened.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive hydrogels, and in particular relates to an antifreeze sodium polyacrylate-based ion conductive hydrogel and a preparation method thereof. Background Art

[0002] Conductive hydrogel is a type of functional material that combines high water content and conductive properties. It is usually composed of a hydrophilic polymer network and a conductive filler. It has the advantages of high flexibility, biocompatibility and stimulus responsiveness, and has potential application prospects in flexible sensors, electronic skin and supercapacitors.

[0003] Although conductive hydrogels have many advantages, they still face the following challenges in practical applications: most conductive hydrogels have a single functionality and their conductivity and mechanical properties are poor; in low-temperature environments, the water inside traditional hydrogels will freeze, resulting in loss of conductivity; in dry environments, hydrogels are prone to dehydration and hardening, losing flexibility; during long-term cyclic use, the hydrogel network structure is very likely to cause fatigue effects and mechanical damage, resulting in a decrease in its mechanical properties and even loss of conductivity.

[0004] In order to solve the above problems, researchers have tried many methods, such as improving mechanical strength through double network structures or nanocomposite technology, but often at the expense of flexibility; introducing ionic liquids or conductive polymers, but there are problems of high cost or poor biocompatibility. By adding high concentrations of salt to the hydrogel to inhibit the formation of water ice crystals, the material's antifreeze resistance can be improved, but high concentrations of salt are often corrosive to most devices; adding a single ethylene glycol organic antifreeze agent usually only improves antifreeze resistance, while adding a single propylene glycol organic antifreeze agent usually improves antifreeze resistance and moisture retention, but often reduces the conductivity of the material.

[0005] Therefore, how to develop a new conductive hydrogel with excellent comprehensive performance through material selection and process innovation, taking into account excellent conductivity, frost resistance, mechanical properties, moisture retention and anti-fatigue properties, has become a hot issue in the design and preparation research of conductive hydrogel materials. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the existing hydrogel materials have poor electrical conductivity, antifreeze property, mechanical property, moisture retention and anti-fatigue property. The present invention provides an antifreeze type sodium polyacrylate-based ion conductive hydrogel and a preparation method thereof.

[0007] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions: The first aspect of the present invention provides a method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel, comprising the following steps: S1: adding acrylic acid to deionized water, and adding sodium hydroxide in an ice water bath to obtain a sodium acrylate solution; S2: adding a strong electrolyte into deionized water and performing ultrasonic dispersion to obtain a strong electrolyte dispersion; S3: mixing the antifreeze agent with the sodium acrylate solution and the strong electrolyte dispersion, and performing ultrasonic dispersion to form a uniform mixed solution; S4: adding a chemical crosslinking agent to the mixed solution, stirring to dissolve, adding an initiator and a promoter, and stirring evenly to obtain a hydrogel prepolymer solution; S5: injecting the prepolymer solution into the mold for free radical polymerization to obtain the conductive hydrogel.

[0008] In some embodiments of the present invention, in S1, the pH value of the sodium acrylate solution is 7, the temperature of the ice water bath is 2-7°C, the mass fraction of the sodium acrylate solution is 39%-43%, and the mass ratio of acrylic acid, deionized water, and sodium hydroxide is 1.8:2.67-3.23:1.

[0009] In some embodiments of the present invention, in S2, the mass fraction of the strong electrolyte dispersion is 58-62%.

[0010] In some embodiments of the present invention, in S2, the strong electrolyte is zinc trifluoromethanesulfonate and lithium bis(trifluoromethanesulfonyl imide), and the mass ratio thereof is 1:1.

[0011] In some embodiments of the present invention, in S3, the antifreeze agent is glycerol and ethylene glycol, and the mass ratio thereof is 1:1.2-1.6.

[0012] In some embodiments of the present invention, in S3, the mass ratio of the antifreeze agent, the strong electrolyte dispersion, and the sodium acrylate solution is 1:0.227-1.014:3.7.

[0013] In some embodiments of the present invention, in S4, the chemical cross-linking agent is ethylene glycol dimethacrylate, and the mass ratio of the chemical cross-linking agent to the sodium acrylate solution is 0.001-0.003:1.

[0014] In some embodiments of the present invention, in S4, the initiator is potassium persulfate, the accelerator is ferrous sulfate, and the mass ratio of the initiator, the accelerator, and the sodium acrylate solution is 0.006-0.01:0.02-0.05:1.

[0015] The beneficial effects of the present invention are: (1) The hydrogel provided by the present invention uses environmentally friendly cross-linking agent ethylene glycol dimethacrylate, and adopts a free radical polymerization process to prepare a sodium polyacrylate-based hydrogel material with a chemical cross-linked network, thereby eliminating the defects of low physical cross-linking efficiency and unstable network structure, and realizing efficient and controllable curing of the hydrogel. The obtained hydrogel material has excellent mechanical properties and fatigue resistance, with a tensile strength of 290 kPa and an elongation at break of 900%. After 10 cycles of stretching at 500% strain, the tensile strength can still reach 165 kPa.

[0016] (2) The hydrogel provided by the present invention introduces strong electrolytes zinc trifluoromethanesulfonate and lithium bis(trifluoromethanesulfonyl imide) into the hydrogel system, and Na + , Li + 、Zn 2+ The plasma cooperative migration and the high dissociation ability of the sulfonic acid group construct an efficient ion transport network, achieving a significant improvement in the conductive properties. The conductivity of the hydrogel reaches 3.1S / m at room temperature.

[0017] (3) The hydrogel provided by the present invention adopts a polyvalent synergistic antifreeze system of propylene glycol and ethylene glycol, which solves the problem that adding a single ethylene glycol organic antifreeze agent can usually only improve antifreeze properties, and adding a single propylene glycol organic antifreeze agent can usually improve antifreeze properties and moisture retention, but often reduces the conductivity of the material. This polyol synergistic effect achieves the simultaneous optimization of antifreeze properties, low-temperature conductivity and moisture retention. The conductivity of the sodium polyacrylate-based conductive hydrogel is as high as 2.3 S / m at a low temperature of -27°C, while maintaining good flexibility, which broadens its application range in low-temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 A flow chart of a method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel provided in an embodiment of the present invention; Figure 2 Infrared spectra of the hydrogels in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 in the method for preparing the antifreeze sodium polyacrylate-based ion-conductive hydrogel provided in the embodiments of the present invention; Figure 3 X-ray diffraction (XRD) patterns of the hydrogels in Examples 1, 2, 3, 4 and 5 of the method for preparing the antifreeze sodium polyacrylate-based ion-conductive hydrogel provided in the embodiments of the present invention; Figure 4 A scanning electron microscope (SEM) image of the hydrogel in Example 1 of the method for preparing the antifreeze sodium polyacrylate-based ion-conductive hydrogel provided in an embodiment of the present invention; Figure 5 The cyclic loading-unloading curve and the corresponding energy dissipation diagram at 500% strain in Example 1 of the method for preparing the antifreeze sodium polyacrylate-based ion-conductive hydrogel provided in an embodiment of the present invention; Figure 6 Differential scanning calorimetry (DSC) graphs of the hydrogels of Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 in the method for preparing the antifreeze sodium polyacrylate-based ion conductive hydrogel provided by the embodiments of the present invention; Figure 7 Moisture retention graph of the hydrogels of Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 in the preparation method of the antifreeze sodium polyacrylate-based ion conductive hydrogel provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention will be described in detail below in conjunction with the embodiments of the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] like Figure 1 As shown, the present invention provides a method for preparing an antifreeze sodium polyacrylate-based ion conductive hydrogel, comprising the following steps: S1: adding acrylic acid to deionized water, and adding sodium hydroxide in an ice water bath to obtain a sodium acrylate solution; S2: adding a strong electrolyte into deionized water and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1; S3: mixing the antifreeze agent 2 with the sodium acrylate solution and the strong electrolyte dispersion 1, and performing ultrasonic dispersion to form a uniform mixed solution 3; S4 adds chemical crosslinking agent 4 to the mixed solution 3, stirs to dissolve, then adds initiator 5 and accelerator 6, stirs to obtain hydrogel prepolymer solution 7; S5: injecting the prepolymer solution 7 into the mold for free radical polymerization to obtain the conductive hydrogel.

[0023] Further, in S1, the pH value of the sodium acrylate solution is 7, the temperature of the ice water bath is 2-7°C, the mass fraction of the sodium acrylate solution is 39%-43%, preferably 41%, and the mass ratio of acrylic acid, deionized water, and sodium hydroxide is 1.8:2.67-3.23:1.

[0024] Further, in S2, the mass fraction of the strong electrolyte dispersion is 58-62%, preferably 60%. Furthermore, in S2, the strong electrolyte is zinc trifluoromethanesulfonate and lithium bis(trifluoromethanesulfonyl imide), and the mass ratio thereof is 1:1.

[0025] Furthermore, in S3, the antifreeze agent is propylene glycol and ethylene glycol, and the mass ratio thereof is 1:1.2-1.6, preferably 1:1.4.

[0026] Furthermore, in S3, the mass ratio of the antifreeze agent, the strong electrolyte dispersion, and the sodium acrylate solution is 1:0.227-1.014:3.7, preferably 1:0.731:3.7.

[0027] Further, in S4, the chemical crosslinking agent is ethylene glycol dimethacrylate, and the mass ratio of the chemical crosslinking agent to the sodium acrylate solution is 0.001-0.003:1, preferably 0.002:1. Further, in S4, the initiator is potassium persulfate, the accelerator is ferrous sulfate, and the mass ratio of the initiator, the accelerator, and the sodium acrylate solution is 0.006-0.01:0.02-0.05:1, preferably 0.008:0.04:1.

[0028] In the above S4, 1. In the free radical polymerization reaction, the initiator and the promoter are added to control and accelerate the progress of the free radical reaction. 2. The initiator potassium persulfate and the promoter ferrous sulfate generate sulfate radicals through redox reaction. These free radicals react with the sodium acrylate monomer to generate monomer free radicals, which then trigger the chain growth reaction to form sodium polyacrylate hydrogel. 3. The potassium persulfate / ferrous sulfate system can initiate polymerization at room temperature or lower temperatures, reduce energy consumption and prevent high temperature from destroying the hydrogel structure; the controllable free radical release rate allows the monomers to gradually polymerize to form a uniform and stable three-dimensional network, thereby improving the mechanical strength of the hydrogel; the iron ions and potassium ions generated by the reaction can also be used as ion conductive carriers to improve the conductivity of the hydrogel.

[0029] Example 1 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 23.47 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 41%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 6 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 60%; (3) mixing an antifreeze agent 2 composed of 3.84 g of propylene glycol and 5.38 g of ethylene glycol, 34.06 g of a sodium acrylate solution and 6.72 g of a strong electrolyte dispersion 1, and performing ultrasonic dispersion to form a uniform mixed solution 3; (4) Add 0.068 g of chemical crosslinking agent 4 to the mixed solution 3, stir to dissolve, then add 0.272 g of initiator 5 potassium persulfate and 1.36 g of accelerator 6 ferrous sulfate, stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0030] Example 2 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 25.82 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 39%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 6.52 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 58%; (3) mixing an antifreeze agent 2 consisting of 4.19 g of propylene glycol and 5.03 g of ethylene glycol, 34.06 g of a sodium acrylate solution and 6.72 g of a strong electrolyte dispersion 1, and performing ultrasonic dispersion to form a uniform mixed solution 3; (4) Add 0.034 g of chemical crosslinking agent 4 to the mixed solution 3, stir to dissolve, then add 0.204 g of initiator 5 potassium persulfate and 0.68 g of accelerator 6 ferrous sulfate, stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0031] Example 3 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 24.61 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 40%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 5.52 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 62%; (3) mixing an antifreeze agent 2 composed of 4.41 g of propylene glycol and 5.74 g of ethylene glycol, 37.55 g of a sodium acrylate solution and 2.30 g of a strong electrolyte dispersion 1, and performing ultrasonic dispersion to form a uniform mixed solution 3; (4) Add 0.038 g of chemical crosslinking agent 4 to the mixed solution 3, stir to dissolve, then add 0.263 g of initiator 5 potassium persulfate and 0.75 g of accelerator 6 ferrous sulfate, stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0032] Example 4 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 22.38 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 42%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 5.75 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 61%; (3) mixing an antifreeze agent 2 composed of 3.86 g of propylene glycol and 5.80 g of ethylene glycol, 35.78 g of a sodium acrylate solution and 4.56 g of a strong electrolyte dispersion 1, and performing ultrasonic dispersion to form a uniform mixed solution 3; (4) Add 0.036 g of chemical crosslinking agent 4 to the mixed solution 3, stir to dissolve, then add 0.32 g of initiator 5 potassium persulfate and 1.07 g of accelerator 6 ferrous sulfate, stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0033] Example 5 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 21.33 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 43%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 6.25 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 59%; (3) mixing an antifreeze agent 2 composed of 3.36 g of propylene glycol and 5.39 g of ethylene glycol, 32.38 g of a sodium acrylate solution and 8.87 g of a strong electrolyte dispersion 1, and performing ultrasonic dispersion to form a uniform mixed solution 3; (4) Add 0.097 g of chemical crosslinking agent 4 to the mixed solution 3, stir to dissolve, then add 0.32 g of initiator 5 potassium persulfate and 1.62 g of accelerator 6 ferrous sulfate, stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0034] Comparative Example 1 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 25.82 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 39%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 6.52 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 58%; (3) 9.22 g of glycerol antifreeze agent 2, 34.06 g of sodium acrylate solution and 6.72 g of strong electrolyte dispersion 1 were mixed and ultrasonically dispersed to form a uniform mixed solution 3; (4) Add 0.187 g of initiator 5 potassium persulfate and 0.61 g of promoter 6 ferrous sulfate to the mixed solution 3, and stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0035] Comparative Example 2 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 25.82 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 39%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 6.52 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 58%; (3) 9.22 g of ethylene glycol antifreeze agent 2, 34.06 g of sodium acrylate solution and 6.72 g of strong electrolyte dispersion 1 are mixed and ultrasonically dispersed to form a uniform mixed solution 3; (4) Add 0.170 g of initiator 5 potassium persulfate and 0.51 g of promoter 6 ferrous sulfate to the mixed solution 3, and stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0036] Comparative Example 3 A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel comprises the following steps: (1) Add 14.41 g of acrylic acid to 25.82 g of deionized water, add 8.0 g of sodium hydroxide in an ice-water bath, and stir evenly until the pH value of the solution is 7 to obtain a sodium acrylate solution with a mass fraction of 39%; (2) adding 4.5 g of zinc trifluoromethanesulfonate and 4.5 g of lithium bis(trifluoromethanesulfonyl imide) to 6.52 g of deionized water, and performing ultrasonic dispersion to obtain a strong electrolyte dispersion 1 with a mass fraction of 58%; (3) mixing an antifreeze agent 2 consisting of 4.19 g of propylene glycol and 5.03 g of ethylene glycol, 34.06 g of a sodium acrylate solution and 6.72 g of a strong electrolyte dispersion 1, and performing ultrasonic dispersion to form a uniform mixed solution 3; (4) Add 0.163 g of initiator 5 potassium persulfate and 0.48 g of promoter 6 ferrous sulfate to the mixed solution 3, and stir evenly to obtain a hydrogel prepolymer solution 7; (5) Injecting the prepolymer solution 7 into a mold for free radical polymerization to obtain the antifreeze sodium polyacrylate-based ion conductive hydrogel.

[0037] Detection The antifreeze sodium polyacrylate-based ion conductive hydrogels prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were tested by Fourier transform infrared spectroscopy. The test results are shown in Figure 2 The antifreeze sodium polyacrylate-based ion-conductive hydrogels prepared in Example 1, Example 2, Example 3, Example 4, Example 5 and Comparative Example 1 were subjected to X-ray diffraction tests. The test results are shown in Figure 3 The antifreeze sodium polyacrylate-based ion-conductive hydrogel prepared in Example 1 was tested by scanning electron microscopy. The test results are shown in Figure 4 .in Figure 2 This is an infrared spectrum, indicating that the antifreeze-type sodium polyacrylate-based ion-conductive hydrogel was successfully prepared. Figure 3 3 is an XRD diagram. In the diagram, Example 5 shows a characteristic peak at 32.36°, while Example 1, Example 2, Example 3, Example 4 and Comparative Example 1 have no obvious characteristic peaks, indicating that the strong electrolyte dispersion has good dispersibility in the prepared hydrogel, without large-area accumulation and agglomeration. Figure 4This is a SEM image, which shows that the hydrogel network has a high degree of cross-linking and good density.

[0038] Experimental Example 1 1 Mechanical properties test The hydrogels prepared in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were subjected to tensile property tests, and the test results are shown in Table 1. The prepared hydrogel materials were tested using a universal tensile machine (CMT6104). The hydrogel materials were all dumbbell-shaped with a length of 30 mm, a width of 4 mm, and a thickness of 2 mm. The stretching rate was 20 mm / min, and the test temperature was room temperature (25°C). At the same time, the hydrogel prepared in Example 1 was subjected to a cyclic loading-unloading test under 500% strain, and the energy dissipation corresponding to the test results is shown in Table 1. Figure 5 The calculation formula of stress-strain curve is as follows: where 𝜀 is the tensile strain, L is the maximum stretching length of the hydrogel, L 0 is the initial length of the hydrogel.

[0039] in, σ is the tensile stress, F is the applied load, A 0 is the cross-sectional area of ​​the sample.

[0040] Table 1 Test results of tensile properties of prepared hydrogels According to Table 1, the tensile strength of Example 1 is 290 kPa, and the elongation at break is 900%, showing excellent mechanical properties. With the increase of the content of the strong electrolyte dispersion 2, the tensile strength and elongation at break of the hydrogel first increase and then decrease. In contrast, the mechanical properties of Comparative Example 1 are poor (tensile strength is 152 kPa, elongation at break is 531%), while Comparative Examples 2 and 3 have higher elongations at break (886% and 865%), but their tensile strengths are only 186 kPa and 172 kPa, respectively. Figure 5 It can be seen that after 10 cycles of loading and unloading at 500% strain, the dissipated energy of Example 1 increased from the initial 23.6 MJ / m 3 Reduced to 15.8MJ / m 3 , and the tensile strength of the hydrogel can still be maintained above 165kPa, indicating that the hydrogel has good stability and fatigue resistance.

[0041] Experimental Example 2 2 Antifreeze performance test The hydrogels (6-10 mg) prepared in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were placed in a differential scanning calorimeter (DSC822e, Switzerland) and cooled from 20°C to -70°C at a rate of 2°C / min under nitrogen protection. The test results are shown in Figure 6 .

[0042] according to Figure 6 It can be seen that comparative example 1 has a sharp crystallization peak at -15°C, and example 5 has a crystallization peak at -37°C, while the hydrogels prepared in example 1, example 2, example 3, example 4, comparative example 2 and comparative example 3 have no obvious crystallization peaks between -70°C and 20°C, indicating that the hydrogel prepared by the present invention has good antifreeze properties.

[0043] Experimental Example 3 3. Conductivity test The hydrogels prepared in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were tested for room temperature conductivity using an electrochemical workstation (CHI600E / 700E). The hydrogel materials were all in the shape of 30mm×10mm×2mm strips. At the same time, the prepared hydrogel materials were placed in a refrigerator at -27°C, and after being frozen for 24 hours, they were taken out and tested for low temperature conductivity. The test results are shown in Figure 7 The calculation formula of conductivity is as follows: in, σ is the conductivity, R is the resistor, L is the distance between the two electrodes, S is the cross-sectional area of ​​the hydrogel.

[0044] Table 2 Test results of the conductivity of the prepared hydrogels According to Table 2, the conductivity of Example 1 is 3.10S / m, and even after freezing at -27°C, the conductivity remains at 2.30S / m. As the content of the strong electrolyte dispersion increases, the conductivity at room temperature gradually increases, but the decrease in conductivity at low temperature gradually increases. The conductivity of Comparative Example 1 is 2.12S / m, and the conductivity is 1.48S / m after freezing at -27°C. The conductivity of Comparative Examples 2 and 3 is lower (2.02S / m and 2.30S / m), but their low-temperature conductivity is still stable at 1.62S / m and 1.70S / m, indicating that the hydrogel prepared by the present invention has good conductive properties.

[0045] Experimental Example 4 4 Moisturizing performance test The hydrogel prepared in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 was tested for moisture retention by weighing method. The hydrogel material was placed in a constant temperature drying oven, the temperature was set to 25°C, and the hydrogel material was taken out at regular intervals and weighed and recorded. The calculation formula for moisture retention is as follows: in, W C is the moisturizing rate, W 0 is the initial weight, W t is the weight of the hydrogel at a certain moment after drying.

[0046] according to Figure 7 It can be seen that the moisturizing property of comparative example 1 is the lowest, with a moisturizing rate of 74%, and the moisturizing property of comparative example 2 is the best, with a moisturizing rate of 82%. As the glycerol content decreases, the moisturizing property of the hydrogel shows a downward trend. The moisturizing rate of Example 1 is 77%, indicating that the glycerol content has a certain influence on the moisturizing property of the hydrogel.

[0047] Through the above-mentioned embodiments and comparative examples, the following conclusions are drawn: (1) The hydrogel provided by the present invention uses environmentally friendly cross-linking agent ethylene glycol dimethacrylate, and adopts a free radical polymerization process to prepare a sodium polyacrylate-based hydrogel material with a chemical cross-linked network, thereby eliminating the defects of low physical cross-linking efficiency and unstable network structure, and realizing efficient and controllable curing of the hydrogel. The obtained hydrogel material has excellent mechanical properties and fatigue resistance, with a tensile strength of 290 kPa and an elongation at break of 900%. After 10 cycles of stretching at 500% strain, the tensile strength can still reach 165 kPa.

[0048] (2) The hydrogel provided by the present invention introduces strong electrolytes zinc trifluoromethanesulfonate and lithium bis(trifluoromethanesulfonyl imide) into the hydrogel system, and Na + , Li + 、Zn 2+ The plasma cooperative migration and the high dissociation ability of the sulfonic acid group construct an efficient ion transport network, achieving a significant improvement in the conductive properties. The conductivity of the hydrogel reaches 3.1S / m at room temperature.

[0049] (3) The hydrogel provided by the present invention adopts a polyvalent synergistic antifreeze system of propylene glycol and ethylene glycol, which solves the problem that adding a single ethylene glycol organic antifreeze agent can usually only improve antifreeze properties, and adding a single propylene glycol organic antifreeze agent can usually improve antifreeze properties and moisture retention, but often reduces the conductivity of the material. This polyol synergistic effect achieves the simultaneous optimization of antifreeze properties, low-temperature conductivity and moisture retention. The conductivity of the sodium polyacrylate-based conductive hydrogel is as high as 2.3 S / m at a low temperature of -27°C, while maintaining good flexibility, which broadens its application range in low-temperature environments.

[0050] The above embodiments and descriptions are only for illustrating the principles and optimal embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The present invention may also have various changes and improvements, which all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing an antifreeze sodium polyacrylate-based ion-conductive hydrogel, characterized in that: The following steps are involved: S1: adding acrylic acid to deionized water, and adding sodium hydroxide in an ice water bath to obtain a sodium acrylate solution; S2: adding a strong electrolyte into deionized water and performing ultrasonic dispersion to obtain a strong electrolyte dispersion (1); S3: mixing the antifreeze agent (2) with the sodium acrylate solution and the strong electrolyte dispersion (1), and ultrasonically dispersing the mixture to form a uniform mixed solution (3); S4: adding a chemical crosslinking agent (4) to the mixed solution (3), stirring to dissolve, adding an initiator (5) and a promoter (6), and stirring to obtain a hydrogel prepolymer solution (7); S5: injecting the prepolymer solution (7) into the mold for free radical polymerization to obtain the conductive hydrogel.

2. The antifreeze sodium polyacrylate-based ion-conductive hydrogel and its preparation method according to claim 1, characterized in that: In S1, the pH value of the sodium acrylate solution is 7, the temperature of the ice water bath is 2-7°C, the mass fraction of the sodium acrylate solution is 39%-43%, and the mass ratio of acrylic acid, deionized water, and sodium hydroxide is 1.8:2.67-3.23:

1.

3. The antifreeze sodium polyacrylate-based ion-conductive hydrogel and its preparation method according to claim 1, characterized in that: In S2, the mass fraction of the strong electrolyte dispersion (1) is 58%-62%.

4. The antifreeze sodium polyacrylate-based ion-conductive hydrogel and its preparation method according to claim 1, characterized in that: In S2, the strong electrolyte is zinc trifluoromethanesulfonate and lithium bis(trifluoromethanesulfonyl imide), and the mass ratio thereof is 1:

1.

5. The antifreeze sodium polyacrylate-based ion-conductive hydrogel and its preparation method according to claim 1, characterized in that: The antifreeze agent described in S3 is glycerol and ethylene glycol, and the mass ratio thereof is 1:1.2-1.

6.

6. The antifreeze sodium polyacrylate-based ion-conductive hydrogel and its preparation method according to claim 1, characterized in that: In S3, the mass ratio of the antifreeze agent (2), the strong electrolyte dispersion (1), and the sodium acrylate solution is 1:0.227-1.014:3.

7.

7. The antifreeze sodium polyacrylate-based ion-conductive hydrogel and the preparation method thereof according to claim 1, characterized in that: In S4, the chemical crosslinking agent (4) is ethylene glycol dimethacrylate, and the mass ratio of the chemical crosslinking agent (4) to the sodium acrylate solution is 0.001-0.003:

1.

8. The antifreeze sodium polyacrylate-based ion-conductive hydrogel and the preparation method thereof according to claim 1, characterized in that: In S4, the initiator (5) is potassium persulfate, the accelerator (6) is ferrous sulfate, and the mass ratio of the initiator (5), the accelerator (6) and the sodium acrylate solution is 0.006-0.01:0.02-0.05:

1.

9. An antifreeze sodium polyacrylate-based ion-conductive hydrogel, characterized in that: The antifreeze sodium polyacrylate-based ion conductive hydrogel is prepared by the preparation method of any one of claims 1 to 8.

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