Low-temperature-resistant self-powered sensing ionic hydrogel as well as preparation method and application thereof

Abstract

The invention provides low-temperature-resistant self-powered sensing ionic hydrogel as well as a preparation method and application thereof, and belongs to the technical field of ionic hydrogel. The method comprises the following steps: dissolving one or two polymeric monomers in deionized water to obtain a solution 1; the polymeric monomer contains double bonds and simultaneously has one ligand group of carboxyl, sulfonic acid group, hydrazide group or amide group; adding a hydrophobic cross-linking agent and a photoinitiator into the solution 1, and uniformly stirring and mixing to obtain a solution 2; adding a central metal ion salt into the solution 2, and uniformly mixing and stirring to obtain a precursor solution; and adding the obtained precursor solution into a polytetrafluoroethylene mold, and carrying out free radical polymerization reaction under an ultraviolet lamp to obtain the low-temperature-resistant self-powered sensing ionic hydrogel. The ionic hydrogel disclosed by the invention has excellent conductivity and relatively high mechanical property at low temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of ionic hydrogels, and in particular relates to a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method and application thereof. Background Art

[0002] With the rapid development of smart wearable devices, soft robots, and human health monitoring, flexible sensing technology has gradually become a research hotspot. Flexible sensors can sense changes in the external environment, obtain external stress, temperature and other information in real time, and convert them into electrical signals. Such sensors require the use of materials with softness and conductive properties. Among them, conductive gel materials have gradually become the core materials in the field of flexible sensing due to their high flexibility, good conductivity and ability to adapt to complex deformations.

[0003] Self-powered technology is an important direction that has received much attention in recent years. Especially in scenarios where no external power supply is required, the self-powered system can autonomously collect energy (such as mechanical energy, thermal energy or light energy) in the environment and convert it into electrical energy to maintain the continuous operation of the sensor. This technology has greatly expanded the application scope of flexible sensors, and is of great value in areas such as remote monitoring, sensing in extreme environments, or unattended equipment. In this context, self-powered flexible sensors combined with conductive gel materials can be autonomously powered and maintain good sensing performance under different environmental conditions, becoming the research frontier of flexible electronic devices. However, in low-temperature environments, the energy collection and sensing capabilities of self-powered sensors are usually severely limited, especially the freezing and failure of conductive gel materials at low temperatures are key bottlenecks.

[0004] To meet these challenges, researchers have developed antifreeze ionic hydrogels, hoping that they can maintain conductivity and mechanical properties in low-temperature environments. There are currently a number of patented technologies for antifreeze hydrogels. The core of these technologies is to prevent water from freezing by changing the composition or structure of the gel, thereby maintaining conductivity and other functions. However, these existing technologies still have many shortcomings in combining low-temperature sensing with self-powered performance. For example, although the conductivity of many antifreeze hydrogels in low-temperature environments has improved, it is still difficult to maintain sufficient energy collection efficiency and sensing stability under extreme conditions. The design of most antifreeze gels relies too much on the addition of antifreeze agents or ionic liquids, while ignoring how to improve their overall performance without compromising the mechanical properties of the gel. In addition, the long-term stability and environmental friendliness of these materials in practical applications also need to be further optimized.

[0005] Therefore, designing and preparing an ionic hydrogel that has good electrical conductivity, sensing performance and mechanical properties in a low-temperature environment and self-powered capability is still a major technical challenge in current research and application. Such a material not only needs to be frost-resistant at low temperatures, but also needs to maintain high flexibility, sensing response and energy collection efficiency under severe cold conditions to meet multiple requirements in practical applications. Summary of the invention

[0006] In order to make up for the deficiencies of the prior art, the present invention proposes a low-temperature resistant self-powered sensing ionic hydrogel and its preparation method and application. The ionic hydrogel has the characteristics of excellent conductivity and high mechanical properties at low temperatures.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions: The present invention first provides a method for preparing a low-temperature resistant self-powered sensing ion hydrogel, the preparation method comprising the following steps: Step 1: dissolving one or two polymerizable monomers in deionized water to obtain a solution 1; the polymerizable monomers contain a double bond and simultaneously have a ligand group selected from the group consisting of a carboxyl group, a sulfonic acid group, a hydrazide group or an amide group; Step 2: adding a hydrophobic crosslinking agent and a photoinitiator to the solution 1 obtained in step 1 and stirring and mixing them uniformly to obtain a solution 2; Step 3: adding the central metal ion salt to the solution 2 obtained in step 2 and mixing and stirring evenly to obtain a precursor solution; Step 4: Add the precursor solution obtained in step 3 into a polytetrafluoroethylene mold, and obtain a low-temperature resistant self-powered sensing ion hydrogel through free radical polymerization under ultraviolet light.

[0008] Preferably, the polymerization monomer in step 1 is selected from one or a mixture of two of acrylic acid, acrylamide, sodium p-styrene sulfonate, methacrylic hydrazide, N-hydroxymethyl acrylamide or 2-acrylamido-2-methyl-1-propane sulfonic acid.

[0009] Preferably, the mass ratio of any two polymerization monomers is 1:(0.1-9).

[0010] Preferably, the hydrophobic crosslinking agent in step 2 is p-divinylbenzene, 1,9-decadiene, 1,6-heptadiene, 2,2'-diallyl bisphenol A or diallyl terephthalate.

[0011] Preferably, the photoinitiator in step 2 is 2-hydroxy-2-methylpropiophenone.

[0012] Preferably, the molar ratio of the hydrophobic crosslinking agent to the polymerizable monomer in step 2 is 1:(20-1000); the molar ratio of the photoinitiator to the polymerizable monomer is 1:(10-5000).

[0013] Preferably, the central metal ion salt described in step three is selected from any one or two of zirconium oxychloride octahydrate, zirconium sulfate, zirconium nitrate, cupric chloride, ferric chloride, calcium sulfate, zinc sulfate or zinc chloride.

[0014] Preferably, the reaction time in step 4 is 30-90s.

[0015] The present invention also provides a low-temperature-resistant self-powered sensing ion-type hydrogel obtained by the above preparation method.

[0016] The present invention also provides application of the low-temperature resistant self-powered sensing ion type hydrogel in the field of flexible sensors.

[0017] Beneficial effects of the present invention The present invention mixes the reaction polymerization monomer, the cross-linking agent, and the central metal ion salt in a certain proportion to obtain a precursor solution, and prepares a low-temperature resistant self-powered sensing ion type hydrogel by light-initiated free radical polymerization. In the hydrogel, the polymerization monomer molecules are aggregated in the metal coordination ion region, and dense and mutually entangled polymer segments are generated after the polymerization reaction. During the stretching process, the physical entanglement part preferentially dissipates the tension, thereby improving the tensile properties of the hydrogel. In addition, the metal salt ions serve as a conductive medium to build an ion channel for the hydrogel, thereby increasing the conductive properties of the hydrogel and enhancing its self-powered performance through ionic conduction.

[0018] In the hydrogel precursor solution, after the central metal ion salt is added to the precursor solution, the polymerized monomer containing double bonds and having one of the ligand groups of carboxyl, sulfonic acid, hydrazide, and amide forms coordination with the central metal ion salt and gathers near the central metal ion salt, and forms dense and mutually entangled polymer segments after free radical polymerization. The high salt environment also weakens the hydrophobic association, making the dispersed particle size of the hydrophobic crosslinker in water smaller, and weakening the influence of the Hofmeister effect on the mechanical properties of the hydrogel. The present invention suppresses ice nucleation by adding a large amount of central metal ion salts, thereby increasing the lower limit of the use temperature of the hydrogel, broadening the applicable temperature range, and greatly increasing the conductivity of the hydrogel. At the same time, the spontaneous migration of ions in the hydrogel and the migration caused by force enable the hydrogel to spontaneously generate current without an external electric field; the strategy of hydrophobic crosslinking agent and coordination-induced entanglement weakens the hardening of the hydrogel caused by the Hofmeister effect and increases the maximum tensile strain of the hydrogel; a large number of coordination bonds provide a way for the hydrogel to dissipate energy during stretching, thereby increasing the maximum tensile stress of the hydrogel; the entanglement domain formed around the metal salt enables the hydrogel to have good large-strain cyclability. The polymerized monomer, hydrophobic crosslinker, and central metal ion salt can form a three-dimensional network through coordination-induced entanglement and hydrophobic homogeneous crosslinking, so that the low-temperature-resistant self-powered sensing ion conductive hydrogel has a wide applicable temperature range, extreme low temperature tolerance, cyclic load stability, and conductivity, and can maintain good conductivity, sensitivity, mechanical properties (such as maximum tensile stress, elongation at break, compressibility, fatigue resistance), and light transmittance at low temperatures (-70~0°C). The preparation method is simple in process and mild in conditions.

[0019] The low-temperature resistant self-powered sensing ion hydrogel prepared by the present invention will help promote the application of self-powered flexible sensors in extreme environments, especially in the fields of remote monitoring, environmental sensing, and medical health, and will open up a wider application space for future intelligent sensing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The stress-strain curve of the low-temperature resistant self-powered sensing ionic hydrogel prepared in Example 1; Figure 2 50 times 1000% strain cycle load curve of the low-temperature resistant self-powered sensing ionomeric hydrogel prepared in Example 1; Figure 3 This is a real picture of the low-temperature resistant self-powered sensing ionic hydrogel prepared in Example 1 after being left at -20°C for 48 hours; Figure 4 The differential scanning calorimetry analysis curve of the low-temperature resistant self-powered sensing ionomeric hydrogel prepared in Example 1; Figure 5The current variation curves of the low-temperature resistant self-powered sensing ionic hydrogel prepared in Example 1 under different strains; Figure 6 This is a graph showing the relative current change of the low-temperature-resistant self-powered sensing ionic hydrogel prepared in Example 1 during a continuous loading-unloading cycle of 2500s. DETAILED DESCRIPTION

[0021] The present invention first provides a method for preparing a low-temperature resistant self-powered sensing ion hydrogel, the preparation method comprising the following steps: Step 1: dissolving one or two polymerizable monomers in deionized water to obtain a solution 1; the polymerizable monomers contain a double bond and simultaneously have a ligand group selected from the group consisting of a carboxyl group, a sulfonic acid group, a hydrazide group or an amide group; The polymerizable monomer is preferably one of acrylic acid, acrylamide, sodium p-styrene sulfonate, methacrylic hydrazide, N-hydroxymethyl acrylamide or 2-acrylamido-2-methyl-1-propane sulfonic acid, or a mixture of two of them. When the two are mixed, the mass ratio of any two polymerizable monomers is preferably 1:0.1-9, and the mass ratio of the polymerizable monomer to deionized water is preferably 1:2-10. The mixing temperature is preferably 25°C, and the mixing time is preferably 1-5h.

[0022] Step 2: adding a hydrophobic crosslinking agent and a photoinitiator to the solution 1 obtained in step 1 and stirring and mixing them uniformly to obtain a solution 2; The hydrophobic crosslinking agent is preferably p-divinylbenzene, 1,9-decadiene, 1,6-heptadiene, 2,2'-diallylbisphenol A or diallyl terephthalate; the photoinitiator is preferably 2-hydroxy-2-methylpropiophenone; the molar ratio of the hydrophobic crosslinking agent to the polymerizable monomer is preferably 1:20-1000; the molar ratio of the photoinitiator to the polymerizable monomer is preferably 1:10-5000; The mixing temperature is preferably 25° C., and the mixing time is preferably 12-24 hours.

[0023] Step 3: adding the central metal ion salt to the solution 2 obtained in step 2 and mixing and stirring evenly to obtain a precursor solution; The central metal ion salt is preferably any one of zirconium oxychloride octahydrate, zirconium sulfate, zirconium nitrate, cupric chloride, ferric chloride, calcium sulfate, zinc sulfate, and zinc chloride, or a combination of two thereof; the mass ratio of the central metal ion salt to water is preferably 1:0.5-10; the mixing temperature is preferably 25°C, and the mixing time is preferably 1-5h.

[0024] Step 4: Add the precursor solution obtained in step 3 to a polytetrafluoroethylene mold, preferably at room temperature, 260-365nm, 5-30W ultraviolet lamp, through free radical polymerization reaction, the reaction time is preferably 30-90s, to obtain a low-temperature resistant self-powered sensing ion hydrogel, the model of the polytetrafluoroethylene mold is preferably GB / T1040-1992 dumbbell sample type 3.

[0025] The present invention also provides a low-temperature-resistant self-powered sensing ion-type hydrogel obtained by the above preparation method.

[0026] The present invention also provides application of the low-temperature resistant self-powered sensing ion type hydrogel in the field of flexible sensors.

[0027] The present invention will be further described below in conjunction with the embodiments. The following embodiments are descriptive rather than restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0028] The various experimental operations involved in the specific embodiments are all routine techniques in the art. For parts not specially annotated in this document, ordinary technicians in the art can implement them by referring to various commonly used reference books, scientific and technological literature or related instructions, manuals, etc. before the filing date of this invention.

[0029] The sources of some components in the embodiments and comparative examples are as follows: Acrylic acid: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 79-10-7; Acrylamide: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 79-06-1; Sodium p-styrene sulfonate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 123333-94-8; Methacrylic hydrazide: purchased from Shanghai Angui Biotechnology Co., Ltd., CAS No.: 2388-01-4 N-Hydroxymethyl acrylamide: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 924-42-5; 2-Acrylamido-2-methyl-1-propanesulfonic acid: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 15214-89-8; 2-Hydroxy-2-methylpropiophenone: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 7473-98-5; p-Divinylbenzene: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 105-06-6; 1,9-Decadiene: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 1647-16-1; 1,6-Heptadiene: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 3070-53-9; 2,2'-Diallylbisphenol A: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 1745-89-7; Diallyl terephthalate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 1026-92-2; Zirconium oxychloride octahydrate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 13520-92-8; Zirconium sulfate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 14644-61-2; Zirconium nitrate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 13986-27-1; Cupric chloride: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 10125-13-0; Ferric chloride: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 7705-08-0; Calcium sulfate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 7778-18-9; Zinc sulfate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 7746-20-0; Zinc chloride: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS number: 7646-85-7; Example 1

[0030] This embodiment provides a low-temperature resistant self-powered sensing ion hydrogel and a preparation method thereof, the preparation method is as follows: (1) 3.7132 g (0.01794 mol) of 2-acrylamido-2-methyl-1-propanesulfonic acid and 1.2916 g (0.01794 mol) of acrylic acid were dissolved in 4 ml of deionized water to obtain Solution 1.

[0031] (2) Add 0.01 ml of photoinitiator 2-hydroxy-2-methylpropiophenone and 0.0116 ml of hydrophobic crosslinker p-divinylbenzene to solution 1 and stir magnetically at room temperature for 12 h to obtain solution 2.

[0032] (3) Add 7 g of zirconium oxychloride octahydrate into solution 2 and stir magnetically at room temperature for 1 h to obtain a precursor solution.

[0033] (4) 0.65 ml of the precursor solution was added into a GB / T1040-1992 dumbbell-shaped specimen type 3 polytetrafluoroethylene mold, and the low-temperature resistant self-powered sensing gel was obtained by free radical polymerization for 30 s at room temperature under a 10 W ultraviolet lamp at 365 nm. Example 2

[0034] This embodiment provides a low-temperature resistant self-powered sensing ion hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the 2-acrylamido-2-methyl-1-propane sulfonic acid and acrylic acid in step (1) are replaced by acrylic acid and acrylamide of the same substance amount, and the rest is the same as embodiment 1. Example 3

[0035] This embodiment provides a low-temperature resistant self-powered sensing ion hydrogel and a preparation method thereof. The difference between the embodiment 1 and the embodiment 1 is that the 2-acrylamido-2-methyl-1-propane sulfonic acid and acrylic acid in step (1) are replaced by acrylamide and 2-acrylamido-2-methyl-1-propane sulfonic acid of the same amount, and the rest is the same as the embodiment 1. Example 4

[0036] This embodiment provides a low-temperature resistant self-powered sensing ion hydrogel and a preparation method thereof. The difference between the embodiment 1 and the embodiment 1 is that the 2-acrylamido-2-methyl-1-propane sulfonic acid and acrylic acid in step (1) are replaced with 2-acrylamido-2-methyl-1-propane sulfonic acid and methacryloyl hydrazide of the same substance amount, and the rest is the same as the embodiment 1. Example 5

[0037] This embodiment provides a low-temperature resistant self-powered sensing ion hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the 2-acrylamido-2-methyl-1-propane sulfonic acid and acrylic acid in step (1) are replaced by sodium p-styrene sulfonate and acrylic acid of the same substance amount, and the rest is the same as embodiment 1. Example 6

[0038] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the 2-acrylamido-2-methyl-1-propane sulfonic acid and acrylic acid in step (1) are replaced by N-hydroxymethyl acrylamide and acrylic acid of the same substance amount, and the rest is the same as embodiment 1. Example 7

[0039] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the hydrophobic crosslinking agent p-divinylbenzene in step (2) is replaced by 1,9-decadiene of the same substance amount, and the rest is the same as embodiment 1. Example 8

[0040] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the hydrophobic crosslinking agent p-divinylbenzene in step (2) is replaced by 1,6-heptadiene of the same substance amount, and the rest is the same as embodiment 1. Example 9

[0041] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the hydrophobic crosslinking agent p-divinylbenzene in step (2) is replaced by 2,2'-diallylbisphenol A of the same substance amount, and the rest is the same as embodiment 1. Example 10

[0042] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the hydrophobic crosslinking agent p-divinylbenzene in step (2) is replaced by diallyl terephthalate of the same amount, and the rest is the same as embodiment 1. Embodiment 11

[0043] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the zirconium oxychloride octahydrate in step (3) is replaced by a saturated solution of zirconium sulfate, and the rest is the same as embodiment 1. Example 12

[0044] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the zirconium oxychloride octahydrate in step (3) is replaced by a saturated solution of zirconium nitrate, and the rest is the same as embodiment 1. Example 13

[0045] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the zirconium oxychloride octahydrate in step (3) is replaced by a saturated solution of cupric chloride, and the rest is the same as embodiment 1. Embodiment 14

[0046] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the zirconium oxychloride octahydrate in step (3) is replaced by a saturated solution of ferric chloride, and the rest is the same as embodiment 1. Embodiment 15

[0047] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the zirconium oxychloride octahydrate in step (3) is replaced by a saturated solution of calcium sulfate, and the rest is the same as embodiment 1. Example 16

[0048] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the zirconium oxychloride octahydrate in step (3) is replaced by a saturated solution of zinc sulfate, and the rest is the same as embodiment 1. Embodiment 17

[0049] This embodiment provides a low-temperature resistant self-powered sensing ionic hydrogel and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the zirconium oxychloride octahydrate in step (3) is replaced by a saturated solution of zinc chloride, and the rest is the same as embodiment 1.

[0050] The low-temperature-resistant self-powered sensing ionic hydrogel provided in the above embodiment was tested, and the specific testing method is as follows.

[0051] (1) Tensile properties: The experiment was conducted using a single-column universal material machine (Bluehill® Universal 5944, USA). The tensile rate of the uniaxial tensile test was 100 mm / min at room temperature. In the uniaxial tensile test, the gel sample was stretched until it broke. The tensile rate of the cyclic loading-unloading test was 200 mm / min. The test used a dumbbell-shaped specimen with a total length of 50 mm, an end width of 8.5 mm, a narrow part length of 25 mm, a narrow part width of 4 mm, and a thickness of 1 mm. Each test was repeated at least three times.

[0052] (2) Sensing performance: The performance of the hydrogel sensor was tested using a single-column universal material analyzer (Bluehill® Universal 5944, USA) and a CHI660e electrochemical workstation. During the test, the electrochemical workstation recorded the current changes of the hydrogel during stretching and relaxation in real time.

[0053] (3) Antifreeze performance: The antifreeze performance of the hydrogel samples (5-10 mg) was analyzed using a differential scanning calorimeter (TA DSC 2500, USA). Before the test, the test system was cooled from 25 °C to -70 °C under a flowing nitrogen atmosphere (50 mL / min). After being kept at -70 °C for 5 min, the sample was heated to 25 °C at a heating rate of 10 °C / min.

[0054] Figure 1 The stress-strain curve of the low-temperature resistant self-powered sensing ionic hydrogel prepared in Example 1; Figure 1 This indicates that by adjusting the cross-linking time of the low-temperature resistant self-powered sensing ion hydrogel, the mechanical properties of the hydrogel can be regulated. Increasing the illumination time will lead to higher maximum tensile stress (1.62MPa-3.29MPa) and lower stretchability (1852%-2959%). Figure 2 50 times 1000% strain cycle load curve of the low-temperature resistant self-powered sensing ionomeric hydrogel prepared in Example 1; Figure 2 This indicates that in the first 20 cycles, the metal coordination bonds acted as sacrificial bonds to dissipate stress, and in the remaining 30 cycles, energy dissipation was mainly completed by the entanglement structure of the hydrogel itself without breaking chemical bonds. Therefore, it exhibited good cyclability and verified the formation of entanglement domains.

[0055] Figure 3 This is a real picture of the low-temperature resistant self-powered sensing ionic hydrogel prepared in Example 1 after being left at -20°C for 48 hours; wherein, Figure 3 (a) is a real picture of the low-temperature resistant self-powered sensing ionic hydrogel after being placed at -20°C for 48 hours. Figure 3 (b) A bending picture of the low-temperature resistant self-powered sensing ionic hydrogel after being placed at -20°C for 48 hours. Figure 3 (c) The entanglement image of the low-temperature resistant self-powered sensing ionic hydrogel after being placed at -20°C for 48 hours. Figure 3 (a), (b), and (c) show pictures of the hydrogel after being left at -20°C. The hydrogel can still maintain its flexibility and can be bent and knotted.

[0056] Figure 4 The differential scanning calorimetry analysis curve of the low-temperature resistant self-powered sensing ionomeric hydrogel prepared in Example 1; Figure 4 This indicates that no melting endothermic peak occurs when the temperature of the hydrogel rises from -70°C to 25°C, proving that the hydrogel is not frozen.

[0057] Figure 5 The current variation curves of the low-temperature resistant self-powered sensing ionic hydrogel prepared in Example 1 under different strains; Figure 5 This shows that hydrogels have different signal outputs for different strains, proving that hydrogels can be used as strain sensors.

[0058] Figure 6 The relative current change of the low-temperature resistant self-powered sensing ionic hydrogel prepared in Example 1 within 2500s of continuous loading-unloading cycle. Figure 6 This indicates that the low-temperature-resistant self-powered sensing ionic hydrogel has stability for long-term use.

[0059] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a low-temperature resistant self-powered sensing ionomeric hydrogel, characterized in that: The steps include: Step 1: dissolving one or two polymerizable monomers in deionized water to obtain a solution 1; the polymerizable monomers contain a double bond and simultaneously have a ligand group selected from the group consisting of a carboxyl group, a sulfonic acid group, a hydrazide group or an amide group; Step 2: adding a hydrophobic crosslinking agent and a photoinitiator to the solution 1 obtained in step 1 and stirring and mixing them uniformly to obtain a solution 2; Step 3: adding the central metal ion salt to the solution 2 obtained in step 2 and mixing and stirring evenly to obtain a precursor solution; Step 4: Add the precursor solution obtained in step 3 into a polytetrafluoroethylene mold, and obtain a low-temperature resistant self-powered sensing ion hydrogel through free radical polymerization under ultraviolet light.

2. The method for preparing a low-temperature resistant self-powered sensing ion hydrogel according to claim 1, characterized in that: The polymerization monomer in step 1 is selected from one or a mixture of two of acrylic acid, acrylamide, sodium p-styrene sulfonate, methacrylic hydrazide, N-hydroxymethyl acrylamide or 2-acrylamido-2-methyl-1-propane sulfonic acid.

3. The method for preparing a low-temperature resistant self-powered sensing ion hydrogel according to claim 1, characterized in that: The mass ratio of any two polymerization monomers is 1:(0.1-9).

4. The method for preparing a low-temperature resistant self-powered sensing ion hydrogel according to claim 1, characterized in that: The hydrophobic crosslinking agent in step 2 is p-divinylbenzene, 1,9-decadiene, 1,6-heptadiene, 2,2'-diallyl bisphenol A or diallyl terephthalate.

5. The method for preparing a low-temperature resistant self-powered sensing ion hydrogel according to claim 1, characterized in that: The photoinitiator described in step 2 is 2-hydroxy-2-methylpropiophenone.

6. The method for preparing a low-temperature resistant self-powered sensing ion hydrogel according to claim 1, characterized in that: The molar ratio of the hydrophobic crosslinking agent to the polymerizable monomer in step 2 is 1:(20-1000); the molar ratio of the photoinitiator to the polymerizable monomer is 1:(10-5000).

7. The method for preparing a low-temperature resistant self-powered sensing ionomeric hydrogel according to claim 1, characterized in that: The central metal ion salt described in step 3 is selected from any one or two of zirconium oxychloride octahydrate, zirconium sulfate, zirconium nitrate, cupric chloride, ferric chloride, calcium sulfate, zinc sulfate or zinc chloride.

8. The method for preparing a low-temperature resistant self-powered sensing ionomeric hydrogel according to claim 1, characterized in that: The reaction time of step 4 is 30-90s.

9. The low-temperature resistant self-powered sensing ion hydrogel obtained by the preparation method according to claim 1.

10. Application of the low-temperature resistant self-powered sensing ion hydrogel according to claim 9 in the field of flexible sensors.

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