A fast-responsive and low-hysteresis conductive hydrogel and its preparation method and application

Abstract

The present invention discloses a fast-responsive and low-hysteresis conductive hydrogel, its preparation method and application. The method includes: dissolving an inorganic salt in deoxygenated deionized water, and then successively adding sodium hydroxide, carrageenan, acrylic acid, a crosslinking agent, and an initiator to obtain a reaction solution; introducing the reaction solution into a mold and sealing it, and then initiating polymerization to obtain a conductive hydrogel with fast response and low hysteresis. The conductive hydrogel provided by the present invention has the characteristics of high strength, fast response, low hysteresis, and high conductivity. During its preparation process, carrageenan can be dispersed and dissolved at room temperature without heating. The percentage of hysteresis of the double-network conductive hydrogel provided by the present invention is within 5%, which is less than 1 / 4 of that of traditional conductive hydrogels; the residual strain after stretching is less than 5%, which is less than 1 / 10 of that of traditional double-network conductive hydrogels; this performance provides an ideal material for wearable hydrogel strain sensors and can improve important characteristics such as the sensitivity, durability, and stability of the sensors.

Description

Technical Field

[0001] The present invention belongs to the field of flexible intelligent wearable conductive hydrogel materials, and particularly relates to a conductive hydrogel with fast recovery and low hysteresis, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, most of the materials for wearable products are prepared based on inorganic rigid conductor materials. Due to the mismatch between their modulus and human skin, they are too rigid to be bent, which greatly limits the comfort and integration of wearable devices. Hydrogel is a three-dimensional network structure material with extremely high water content. Its modulus is close to that of human skin, and it has good biocompatibility. At the same time, research shows that the signal conduction delay of conductive hydrogels based on ionic conductors is relatively low and can be consistent with traditional physical conductors. Therefore, conductive hydrogel is an ideal flexible wearable material (see iScience. 2021, 24(11), 103174).

[0003] Although there are many studies on wearable devices based on conductive hydrogels currently, conductive gels can conduct signals through the resistance change caused by deformation and have high sensitivity. However, there are still several problems as follows: After multiple repeated stretches, the hydrogel material has residual strain and hysteresis phenomenon, and the recovery of the gel requires a certain amount of time, which greatly limits the ability of the conductive gel to work stably for a long time. It is reported in the existing literature that after a hydrogel sensor is stretched to 600% strain and recovered, the residual strain reaches ~100%, and the hysteresis percentage reaches ~40% (ACS Appl. Mater. Interface 2016, 8, 29749 - 29758).

[0004] In addition, the low mechanical strength of ordinary hydrogels is also one of the conditions restricting their use as sensor materials. Carrageenan is a kind of natural polysaccharide material. When compounded with hydrogels, a double-network hydrogel can be prepared to improve the strength of the hydrogel. It is reported in the existing literature that for a double-network hydrogel based on carrageenan - polyacrylamide, the dissolution of carrageenan is carried out at 70°C, and the tensile strength of the prepared hydrogel can be increased to 100 kPa, which is 5 times that of a single-network polyacrylamide hydrogel without adding carrageenan. However, after this double-network hydrogel is stretched to 400% strain and recovered, the residual strain reaches more than 50%, and the gel recovery is slow, at least requiring 2 h (J. Mater. Chem. B, 2014, 2, 7631 - 7638); at the same time, traditional carrageenan-based double-network gels generally require high-temperature dissolution of carrageenan, and the preparation process often takes more than 6 h, with cumbersome steps and high energy consumption, which is not conducive to the promotion of actual production applications.

[0005] On the other hand, while the hydrogel maintains high mechanical strength and fast recovery performance, its conductivity often has a certain loss, making it difficult to ensure the sensitive sensing characteristics of the hydrogel sensor. Therefore, a method for conveniently preparing a conductive hydrogel with fast recovery and low hysteresis is of great significance for the flexible wearable field. Summary of the Invention

[0006] In order to overcome the above-mentioned deficiencies existing in the prior art, the purpose of the present invention is to provide a conductive hydrogel with fast recovery and low hysteresis, its preparation method and application, specifically a double-network conductive hydrogel with fast recovery and low hysteresis, its preparation method and application.

[0007] In the conductive hydrogel with fast recovery and low hysteresis disclosed in the present invention, natural polysaccharide carrageenan realizes the functions of enhancing strength and toughness; by controlling the addition order of inorganic salts, sodium hydroxide, carrageenan and acrylic acid, the dispersion and dissolution of carrageenan at room temperature are realized, avoiding the high-energy-consuming method of dissolving by heating; inorganic salts lithium chloride or potassium chloride act as free ions to realize charge conduction, endowing the gel with the characteristic of high conductivity.

[0008] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0009] A preparation method of a conductive hydrogel with fast recovery and low hysteresis provided by the present invention includes the following steps:

[0010] (1) Add an inorganic salt to water, stir and mix evenly to obtain solution 1;

[0011] (2) Add sodium hydroxide to the solution 1 in step (1), stir and mix evenly to obtain solution 2;

[0012] (3) Add carrageenan to the solution 2 in step (2), stir and mix evenly to obtain solution 3;

[0013] (4) Add acrylic acid to the solution 3 in step (3) to obtain solution 4, and then add a chemical cross-linking agent N,N′-methylenebisacrylamide, stir and mix evenly to obtain solution 5;

[0014] (5) Add an initiator to the solution 5 in step (4), stir and mix evenly, remove bubbles by ultrasonic treatment to obtain the final reaction solution, inject the reaction solution into a mold and seal it;

[0015] (6) Ultrasonic the mold containing the final reaction solution again, and then carry out a polymerization reaction to obtain the conductive hydrogel with fast recovery and low hysteresis.

[0016] Further, the type of the inorganic salt in step (1) is any one of lithium chloride and potassium chloride, and the molar amount of the added inorganic salt to the total volume of the added water and acrylic acid is 1 mol / L to 2.5 mol / L.

[0017] Further, the molar amount of the added sodium hydroxide to the total volume of the added water and acrylic acid is 1 mol / L to 4 mol / L.

[0018] Further, the stirring and mixing in step (3) until uniform is carried out under normal temperature environment.

[0019] Further, in step (3), the carrageenan is Kappa type carrageenan, the mass of the added carrageenan to the total volume of the added water and acrylic acid is 5 g / L to 30 g / L, and the stirring and mixing time is 5 min to 20 min.

[0020] Further, in step (3), the stirring and mixing time is 10 min.

[0021] Further, the molar ratio of the dosage of acrylic acid in step (4) to the dosage of sodium hydroxide in step (2) is 1:1; the molar amount of the added chemical crosslinking agent N,N'-methylenebisacrylamide in step (4) is 0.01% to 0.15% of the molar amount of the added acrylic acid.

[0022] Further, the initiator in step (5) is a photoinitiator or a redox initiator. The photoinitiator is α-ketoglutaric acid, and the molar amount of the added photoinitiator is 0.1% to 1% of the molar amount of the acrylic acid added in step (4); the redox initiator is a redox initiation system composed of potassium persulfate and N,N,N',N'-tetramethylethylenediamine. The molar amount of the added potassium persulfate is 0.1% to 0.5% of the molar amount of the acrylic acid added in step (4), and the molar amount of the added N,N,N',N'-tetramethylethylenediamine is 0.1% to 1% of the molar amount of the acrylic acid added in step (4).

[0023] Further, when the polymerization reaction in step (6) uses a photoinitiator, the ultraviolet wavelength used to initiate the reaction is 200 nm to 400 nm, and the ultraviolet lamp power is 60 W to 180 W; when the polymerization reaction in step (6) uses a redox initiator, the polymerization temperature is 15°C to 30°C.

[0024] Further, when the polymerization reaction in step (6) uses a redox initiator, the polymerization temperature is 20°C.

[0025] Further, the polymerization reaction time in step (6) is 0.5 to 4 h.

[0026] The present invention provides a conductive hydrogel with fast recovery and low hysteresis prepared by the above preparation method.

[0027] Furthermore, the hysteresis percentage of the conductive hydrogel with fast recovery and low hysteresis is within 5%, which is less than 1 / 4 of that of traditional conductive hydrogels; the residual strain after stretching is less than 5%, which is less than 1 / 10 of that of traditional double-network conductive hydrogels.

[0028] The present invention also provides an application of the conductive hydrogel with fast recovery and low hysteresis in wearable hydrogel strain sensors.

[0029] A conductive hydrogel with fast recovery and low hysteresis provided by the present invention forms a double-network polyelectrolyte gel by introducing natural macromolecule carrageenan into the gel system, achieving the effect of strengthening and toughening, and having excellent mechanical and electrical properties. It is an ideal conductive hydrogel material for flexible wearable devices.

[0030] The preparation method provided by the present invention creatively uses lithium chloride or potassium chloride and sodium hydroxide as co-solvents for carrageenan, achieving rapid and uniform dispersion of carrageenan at room temperature, avoiding the disadvantages of traditional long-time heating and dissolution, while avoiding the destructive effect of high-temperature dissolution on the carrageenan molecular chain, and greatly reducing energy consumption and equipment complexity, which is suitable for industrial scale-up production.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) The preparation method of the double-network conductive hydrogel with fast recovery and low hysteresis provided by the present invention uses the carrageenan component as the second network to enhance the polyacrylate gel network, obtaining a double-network conductive hydrogel material with strong and tough characteristics; at the same time, the mechanical strength, recovery performance, and conductivity of the hydrogel can be conveniently adjusted by adjusting the components.

[0033] (2) The double-network conductive hydrogel provided by the present invention has the characteristics of fast recovery and low hysteresis. The traditional conductive hydrogel has serious hysteresis. The hysteresis percentage of the double-network conductive hydrogel provided by the present invention is within 5%, which is less than 1 / 4 of that of traditional conductive hydrogels; the residual strain after stretching is less than 5%, which is less than 1 / 10 of that of traditional double-network conductive hydrogels; the performance of fast recovery and low hysteresis provides an ideal material for wearable hydrogel strain sensors, and can improve important characteristics such as the sensitivity, durability, and stability of the sensors.

[0034] (3) The present invention simplifies the preparation method of traditional carrageenan-based double-network gels, abandons the complex and energy-consuming operation of heating and long-time stirring for dissolution, and realizes the rapid dispersion of carrageenan at room temperature by adding lithium chloride or potassium chloride and sodium hydroxide, avoiding the destructive effect of high-temperature dissolution on the carrageenan molecular chain, and having a relatively high energy efficiency ratio. On the other hand, the hydrogels prepared by the method of the present invention have greatly improved in terms of recovery performance, hysteresis performance, mechanical strength, etc. compared with the hydrogels obtained by the heating dissolution method.

[0035] (4) The preparation process flow sequence of the present invention is determined, and it is necessary to add and dissolve and disperse in the order of sodium hydroxide - carrageenan - acrylic acid in sequence. Changing the feeding order will lead to the failure of carrageenan dispersion or the reduction of the performance of the hydrogel. For details, see Comparative Example 1. The conductivity of the carrageenan-based double-network conductive hydrogel prepared according to the method of the present invention can reach up to more than 50 mS / cm at most, which is more than 200% higher than that of the double-network hydrogel prepared by the traditional heating method, and is applicable to the field of high-sensitivity hydrogel strain sensors. Description of the Drawings

[0036] Figure 1 Tensile stress-strain diagram of the fast-recovery and low-hysteresis conductive hydrogel (added with LiCl) prepared in Example 1.

[0037] Figure 2 Tensile-recovery stress-strain diagram (tensile strain 300%) of the fast-recovery and low-hysteresis conductive hydrogel (added with LiCl) prepared in Example 1.

[0038] Figure 3 Tensile stress-strain diagram of the fast-recovery and low-hysteresis conductive hydrogel (added with KCl) prepared in Example 2.

[0039] Figure 4 Tensile-recovery stress-strain diagram (tensile strain 300%) of the fast-recovery and low-hysteresis conductive hydrogel (added with KCl) prepared in Example 2.

[0040] Figure 5 Tensile stress-strain diagram of the hydrogel prepared by changing the feeding order in Comparative Example 1.

[0041] Figure 6 Tensile-recovery stress-strain diagram (tensile strain 300%) of the hydrogel prepared by changing the feeding order in Comparative Example 1. Detailed Description of the Invention

[0042] The following further illustrates the specific implementation of the present invention in conjunction with embodiments, but the implementation and protection of the present invention are not limited thereto. It should be noted that for the processes not specifically described in detail below, those skilled in the art can implement or understand them according to the prior art. The actual products or instruments used without indicating the manufacturer are regarded as conventional products that can be obtained through commercial purchase.

[0043] The present invention will be further described in detail below in conjunction with embodiments. For the hydrogels obtained in the embodiments, the mechanical properties are measured, the hysteresis percentage and residual strain are calculated, etc. using the test methods disclosed in the literature ACS Appl. Mater. Interfaces, 2016, 8, 12384. These examples are only used to illustrate the present invention and not to limit the scope of the present invention.

[0044] Example 1

[0045] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution; the above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0046] The tensile strength of the conductive hydrogel prepared in Example 1 was 230 kPa, the elongation at break was 900%, and the conductivity was 50 mS / cm; the conductive hydrogel obtained in Example 1 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 3.8%, and the residual strain was 3.1%; this process could be repeated 20 times without change in the results.

[0047] Figure 1 Figure for the tensile stress-strain of the fast-recovery and low-hysteresis conductive hydrogel prepared in Example 1. From Figure 1 It can be seen that the tensile strength of the conductive hydrogel prepared in Example 1 was 230 kPa, and the elongation at break was 900%. This indicates that the hydrogel has high strength and large elongation, has strong and tough mechanical properties, can withstand large external forces and deformations without being damaged, and is suitable as a wearable strain sensor.

[0048] Figure 2 Tensile - recovery graph (tensile strain 300%) of the fast - recovering and low - hysteresis conductive hydrogel (added with LiCl) prepared in Example 1. Figure 2 It can be seen that the hysteresis percentage of the conductive hydrogel prepared in Example 1 is 3.8%, and the residual strain is 3.1%. This indicates that the hydrogel still has a very small hysteresis percentage and residual strain after large - strain stretching. The hydrogel can quickly recover to its original state after being stretched, and the energy loss during the deformation - recovery process is very small, featuring low hysteresis. This represents that the degree of damage to the hydrogel network during the deformation process is small, and the hydrogel network can be quickly reconstructed. When this hydrogel is used in wearable strain sensors, it can withstand multiple repeated stretching - recovery deformation processes without causing hysteresis and distortion of the sensing signal, and it is an ideal flexible sensor.

[0049] Example 2

[0050] At room temperature, 1.491 g of potassium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross - linker N,N′ - methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photo - initiator α - ketoglutaric acid was added, and stirred and mixed evenly to obtain a mixed solution. The above - mentioned mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate the polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0051] The tensile strength of the conductive hydrogel prepared in Example 2 is 335 kPa, the elongation at break is 1050%, and the conductivity is 54 mS / cm. The conductive hydrogel obtained in Example 2 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel is 3.5%, and the residual strain is 2.9%. This process can be repeated 20 times, and the results remain unchanged.

[0052] Figure 3 Tensile stress - strain graph of the fast - recovering and low - hysteresis conductive hydrogel (added with KCl) prepared in Example 2. Figure 3 It can be seen that the tensile strength of the conductive hydrogel prepared in Example 2 is 335 kPa, and the elongation at break is 1050%. This indicates that the hydrogel has high strength and large elongation, has strong and tough mechanical properties, can withstand large external forces and deformations without being damaged, and is suitable as a wearable strain sensor.

[0053] Figure 4 Tensile - recovery graph (tensile strain 300%) of the fast - response and low - hysteresis conductive hydrogel (added with KCl) prepared in Example 2. Figure 4 It can be seen that the hysteresis percentage of the conductive hydrogel prepared in Example 2 is 3.5%, and the residual strain is 2.9%. This indicates that the hydrogel still has a very small hysteresis percentage and residual strain after being stretched at a large strain. The hydrogel can quickly recover to its original state after being stretched, and the energy loss during the deformation - recovery process is very small, featuring low hysteresis. This represents that the degree of damage to the hydrogel network during the deformation process is small, and the hydrogel network can be quickly reconstructed; when this hydrogel is used in wearable strain sensors, it can withstand multiple repeated stretching - recovery deformation processes without causing hysteresis and distortion of the sensing signal, and it is an ideal flexible sensor.

[0054] Example 3

[0055] At room temperature, 0.4239 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross - linker N,N′ - methylene bisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photo - initiator α - ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution; the above - mentioned mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate the polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0056] The tensile strength of the conductive hydrogel prepared in Example 3 is 150 kPa, the elongation at break is 800%, and the conductivity is 45 mS / cm; the conductive hydrogel obtained in Example 3 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel is 1.7%, and the residual strain is 1.2%; this process can be repeated 20 times, and the results remain unchanged.

[0057] Example 4

[0058] At room temperature, 1.0597 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0059] The tensile strength of the conductive hydrogel prepared in Example 4 was 200 kPa, the elongation at break was 900%, and the conductivity was 58 mS / cm. The conductive hydrogel prepared in Example 4 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.9%, and the residual strain was 2.8%. This process could be repeated 20 times, and the results remained unchanged.

[0060] Example 5

[0061] At room temperature, 0.7455 g of potassium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0062] The tensile strength of the conductive hydrogel prepared in Example 5 was 265 kPa, the elongation at break was 750%, and the conductivity was 46 mS / cm. The conductive hydrogel prepared in Example 5 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.9%, and the residual strain was 2.3%. This process could be repeated 20 times, and the results remained unchanged.

[0063] Example 6

[0064] At room temperature, 1.8637 g of potassium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 5 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0065] The tensile strength of the conductive hydrogel prepared in Example 6 was 400 kPa, the elongation at break was 750%, and the conductivity was 65 mS / cm. The conductive hydrogel obtained in Example 6 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 3.1%, and the residual strain was 3.4%. This process could be repeated 20 times with unchanged results.

[0066] Example 7

[0067] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.94 mL of deoxygenated deionized water, then 1.2 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 5 min. Then, 2.06 mL of acrylic acid was added to the solution. After stirring evenly, 4.61 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 21.92 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0068] The tensile strength of the conductive hydrogel prepared in Example 7 is 185 kPa, the elongation at break is 700%, and the conductivity is 48 mS / cm; the conductive hydrogel obtained in Example 7 is stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel is 2.5%, and the residual strain is 1.9%; this process can be repeated 20 times without change in the results.

[0069] Example 8

[0070] At room temperature, 0.8478 g of lithium chloride is dissolved in 8.62 mL of deoxygenated deionized water, and then 0.8 g of sodium hydroxide is added. After stirring and mixing evenly, 0.15 g of carrageenan is added at a rate of 0.15 g / min, and stirred for 20 min. Then 1.38 mL of acrylic acid is added to the solution. After stirring evenly, 3.07 mg of the chemical crosslinking agent N,N′-methylenebisacrylamide is added, and stirring is continued until the solution becomes clear and transparent again. Finally, 14.61 mg of the photoinitiator α-ketoglutaric acid is added and stirred and mixed evenly to obtain a mixed solution; the above mixed solution is ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution is injected into a mold and sealed. The mold containing the reaction solution is ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time is 1 h to obtain the final conductive hydrogel.

[0071] The tensile strength of the conductive hydrogel prepared in Example 8 is 150 kPa, the elongation at break is 600%, and the conductivity is 50 mS / cm; the conductive hydrogel obtained in Example 8 is stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel is 1.5%, and the residual strain is 1.9%; this process can be repeated 20 times without change in the results.

[0072] Example 9

[0073] At room temperature, 0.8478 g of lithium chloride was dissolved in 9.31 mL of deoxygenated deionized water, and then 0.4 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 20 min. Then, 0.69 mL of acrylic acid was added to the solution. After stirring evenly, 1.53 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 7.3 mg of the photoinitiator α-ketoglutaric acid was added, and the mixture was stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0074] The tensile strength of the conductive hydrogel prepared in Example 9 was 160 kPa, the elongation at break was 500%, and the conductivity was 52 mS / cm. The conductive hydrogel obtained in Example 9 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.5%, and the residual strain was 1.5%. This process could be repeated 20 times, and the results remained unchanged.

[0075] Example 10

[0076] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.1 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 20 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and the mixture was stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0077] The tensile strength of the conductive hydrogel prepared in Example 10 was 190 kPa, the elongation at break was 800%, and the conductivity was 55 mS / cm. The conductive hydrogel obtained in Example 10 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.1%, and the residual strain was 2.3%. This process could be repeated 20 times, and the results remained unchanged.

[0078] Example 11

[0079] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.3 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, which was then injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0080] The tensile strength of the conductive hydrogel prepared in Example 11 was 365 kPa, the elongation at break was 800%, and the conductivity was 57 mS / cm. The conductive hydrogel obtained in Example 11 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 3%, and the residual strain was 2.8%. This process could be repeated 20 times without change in the results.

[0081] Example 12

[0082] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.075 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, which was then injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0083] The tensile strength of the conductive hydrogel prepared in Example 12 was 165 kPa, the elongation at break was 800%, and the conductivity was 58 mS / cm. The conductive hydrogel obtained in Example 12 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.8%, and the residual strain was 1.3%. This process could be repeated 20 times without change in the results.

[0084] Example 13

[0085] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.05 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinking agent N,N′-methylenebisacrylamide was added, and the stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 60 W and a wavelength of 365 nm for irradiation to initiate the polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0086] The tensile strength of the conductive hydrogel prepared in Example 13 was 150 kPa, the elongation at break was 900%, and the conductivity was 54 mS / cm. The conductive hydrogel obtained in Example 13 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.6%, and the residual strain was 1.7%. This process could be repeated 20 times without change in the results.

[0087] Example 14

[0088] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 9.24 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 60 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0089] The tensile strength of the conductive hydrogel prepared in Example 14 was 255 kPa, the elongation at break was 700%, and the conductivity was 48 mS / cm. The conductive hydrogel obtained in Example 14 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.5%, and the residual strain was 2.4%. This process could be repeated 20 times, and the results remained unchanged.

[0090] Example 15

[0091] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 3.09 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0092] The tensile strength of the conductive hydrogel prepared in Example 15 was 180 kPa, the elongation at break was 1050%, and the conductivity was 56 mS / cm. The conductive hydrogel obtained in Example 15 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.9%, and the residual strain was 1.3%. This process could be repeated 20 times, and the results remained unchanged.

[0093] Example 16

[0094] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 0.62 mg of the chemical crosslinking agent N,N′-methylenebisacrylamide was added, and the mixture was continuously stirred until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and the mixture was stirred and mixed evenly to obtain a mixed solution. To further disperse and remove air bubbles, the above mixed solution was ultrasonicated for 5 min to remove air bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed, and the mold containing the reaction solution was ultrasonicated again. Subsequently, it was placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0095] The tensile strength of the conductive hydrogel prepared in Example 16 was 160 kPa, the elongation at break was 1000%, and the conductivity was 55 mS / cm. The conductive hydrogel prepared in Example 16 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.5%, and the residual strain was 1.8%. This process could be repeated 20 times, and the results remained unchanged.

[0096] Example 17

[0097] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinking agent N,N′-methylenebisacrylamide was added, and the mixture was continuously stirred until the solution became clear and transparent again. Finally, 58.44 mg of the photoinitiator α-ketoglutaric acid was added, and the mixture was stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove air bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed, and the mold containing the reaction solution was ultrasonicated again. Subsequently, it was placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0098] The tensile strength of the conductive hydrogel prepared in Example 17 was 205 kPa, the elongation at break was 930%, and the conductivity was 60 mS / cm; the conductive hydrogel obtained in Example 17 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.4%, and the residual strain was 1.8%; this process could be repeated 20 times, and the results remained unchanged.

[0099] Example 18

[0100] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and the stirring continued until the solution became clear and transparent again. Finally, 14.61 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution; the above mixed solution was ultrasonicated for 5 min to remove air bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 180 W and a wavelength of 365 nm for irradiation to initiate the polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0101] The tensile strength of the conductive hydrogel prepared in Example 18 was 220 kPa, the elongation at break was 1050%, and the conductivity was 46 mS / cm; the conductive hydrogel obtained in Example 18 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.6%, and the residual strain was 2.1%; this process could be repeated 20 times, and the results remained unchanged.

[0102] Example 19

[0103] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 5.84 mg of the photoinitiator α-ketoglutaric acid was added, and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0104] The tensile strength of the conductive hydrogel prepared in Example 19 was 240 kPa, the elongation at break was 800%, and the conductivity was 59 mS / cm. The conductive hydrogel obtained in Example 19 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.8%, and the residual strain was 2.3%. This process could be repeated 20 times, and the results remained unchanged.

[0105] Example 20

[0106] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 54 mg of potassium persulfate and 38 μL of N,N,N′,N′-tetramethylethylenediamine were added, and stirred and mixed evenly to obtain a mixed solution. To further disperse and remove bubbles, the above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and finally placed in an incubator at 20 °C for reaction for 1 h to obtain the final conductive hydrogel.

[0107] The tensile strength of the conductive hydrogel prepared in Example 20 was 250 kPa, the elongation at break was 780%, and the conductivity was 56 mS / cm. The conductive hydrogel obtained in Example 20 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.9%, and the residual strain was 2.1%. This process could be repeated 20 times, and the results remained unchanged.

[0108] Example 21

[0109] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water. Then, 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 27 mg of potassium persulfate and 38 μL of N,N,N′,N′-tetramethylethylenediamine were added, and stirring and mixing were carried out evenly to obtain a mixed solution. To further disperse and remove bubbles, the above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and finally placed in an incubator at 20 °C for reaction for 1 h to obtain the final conductive hydrogel.

[0110] The tensile strength of the conductive hydrogel prepared in Example 21 was 200 kPa, the elongation at break was 850%, and the conductivity was 53 mS / cm. The conductive hydrogel obtained in Example 21 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.4%, and the residual strain was 2.8%. This process could be repeated 20 times, and the results remained unchanged.

[0111] Example 22

[0112] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water. Then, 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 1.08 mg of potassium persulfate and 38 μL of N,N,N′,N′-tetramethylethylenediamine were added, and stirring and mixing were carried out evenly to obtain a mixed solution. To further disperse and remove bubbles, the above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and finally placed in an incubator at 20 °C for reaction for 1 h to obtain the final conductive hydrogel.

[0113] The tensile strength of the conductive hydrogel prepared in Example 22 was 190 kPa, the elongation at break was 800%, and the conductivity was 55 mS / cm; the conductive hydrogel obtained in Example 22 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.1%, and the residual strain was 1.6%; this process could be repeated 20 times with no change in the results.

[0114] Example 23

[0115] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again; finally, 54 mg of potassium persulfate and 6 μL of N,N,N′,N′-tetramethylethylenediamine were added, and the mixture was stirred and mixed evenly to obtain a mixed solution; in order to further disperse and remove air bubbles, the above mixed solution was ultrasonicated for 5 min to remove air bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and finally placed in an incubator at 15 °C for reaction for 3 h to obtain the final conductive hydrogel.

[0116] The tensile strength of the conductive hydrogel prepared in Example 23 was 200 kPa, the elongation at break was 980%, and the conductivity was 56 mS / cm; the conductive hydrogel obtained in Example 23 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.4%, and the residual strain was 1.8%; this process could be repeated 20 times with no change in the results.

[0117] Example 24

[0118] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 54 mg of potassium persulfate and 60 μL of N,N,N′,N′-tetramethylethylenediamine were added, and the mixture was stirred and mixed evenly to obtain a mixed solution. To further disperse and remove air bubbles, the above mixed solution was ultrasonically treated for 5 min to remove air bubbles to obtain a final reaction solution. Then, the final reaction solution was injected into a mold and sealed, and the mold containing the reaction solution was ultrasonically treated again. Finally, it was placed in an incubator at 30 °C for reaction for 1 h to obtain the final conductive hydrogel.

[0119] The tensile strength of the conductive hydrogel prepared in Example 24 was 270 kPa, the elongation at break was 1000%, and the conductivity was 57 mS / cm. The conductive hydrogel obtained in Example 24 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.4%, and the residual strain was 1.8%. This process could be repeated 20 times, and the results remained unchanged.

[0120] Example 25

[0121] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and the mixture was stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and the mixture was stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonically treated for 5 min to remove air bubbles to obtain a final reaction solution. Then, the final reaction solution was injected into a mold and sealed, and the mold containing the reaction solution was ultrasonically treated again. Subsequently, it was placed under an ultraviolet lamp with a power of 180 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h to obtain the final conductive hydrogel.

[0122] The tensile strength of the conductive hydrogel prepared in Example 25 was 260 kPa, the elongation at break was 800%, and the conductivity was 58 mS / cm. The conductive hydrogel obtained in Example 25 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.5%, and the residual strain was 1.9%. This process could be repeated 20 times, and the results remained unchanged.

[0123] Example 26

[0124] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water. Then, 1.6 g of sodium hydroxide was added, and after stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min. After stirring for 10 min, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and after stirring and mixing evenly, a mixed solution was obtained. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 200 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h, and the final conductive hydrogel was obtained.

[0125] The tensile strength of the conductive hydrogel prepared in Example 26 was 200 kPa, the elongation at break was 950%, and the conductivity was 53 mS / cm. The conductive hydrogel obtained in Example 26 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.5%, and the residual strain was 2.3%. This process could be repeated 20 times, and the results remained unchanged.

[0126] Example 27

[0127] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water. Then, 1.6 g of sodium hydroxide was added, and after stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min. After stirring for 10 min, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and after stirring and mixing evenly, a mixed solution was obtained. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 400 nm for irradiation to initiate a polymerization reaction. The irradiation time was 0.5 h, and the final conductive hydrogel was obtained.

[0128] The tensile strength of the conductive hydrogel prepared in Example 27 was 240 kPa, the elongation at break was 700%, and the conductivity was 51 mS / cm; the conductive hydrogel obtained in Example 27 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.5%, and the residual strain was 2.1%; this process could be repeated 20 times without change in the results.

[0129] Example 28

[0130] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical crosslinking agent N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution; the above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution. Then, the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate the polymerization reaction. The irradiation time was 0.5 h to obtain the final conductive hydrogel.

[0131] The tensile strength of the conductive hydrogel prepared in Example 28 was 180 kPa, the elongation at break was 700%, and the conductivity was 57 mS / cm; the conductive hydrogel obtained in Example 28 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.1%, and the residual strain was 2.3%; this process could be repeated 20 times without change in the results.

[0132] Example 29

[0133] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, which was then injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 2 h to obtain the final conductive hydrogel.

[0134] The tensile strength of the conductive hydrogel prepared in Example 29 was 225 kPa, the elongation at break was 950%, and the conductivity was 49 mS / cm. The conductive hydrogel obtained in Example 29 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.5%, and the residual strain was 1.9%. This process could be repeated 20 times with unchanged results.

[0135] Example 30

[0136] At room temperature, 0.847 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of the chemical cross-linking agent N,N′-methylenebisacrylamide was added. Stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, which was then injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 3 h to obtain the final conductive hydrogel.

[0137] The tensile strength of the conductive hydrogel prepared in Example 30 was 240 kPa, the elongation at break was 900%, and the conductivity was 52 mS / cm. The conductive hydrogel obtained in Example 30 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 2.5%, and the residual strain was 1.9%. This process could be repeated 20 times with unchanged results.

[0138] Example 31

[0139] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirred for 10 min. Then, 2.75 mL of acrylic acid was added to the solution. After stirring evenly, 6.15 mg of chemical crosslinker N,N′-methylenebisacrylamide was added, and stirring was continued until the solution became clear and transparent again. Finally, 29.22 mg of photoinitiator α-ketoglutaric acid was added and stirred and mixed evenly to obtain a mixed solution. The above mixed solution was ultrasonicated for 5 min to remove bubbles to obtain the final reaction solution, and then the final reaction solution was injected into a mold and sealed. The mold containing the reaction solution was ultrasonicated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 4 h to obtain the final conductive hydrogel.

[0140] The tensile strength of the conductive hydrogel prepared in Example 31 was 210 kPa, the elongation at break was 930%, and the conductivity was 60 mS / cm. The conductive hydrogel obtained in Example 31 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the conductive hydrogel was 1.4%, and the residual strain was 2.8%. This process could be repeated 20 times with unchanged results.

[0141] Comparative Example 1 (changing the feeding order compared to Example 1)

[0142] The feeding order of Example 1 was inorganic salt (lithium chloride) → sodium hydroxide → carrageenan → acrylic acid → crosslinker → initiator

[0143] The feeding order of Comparative Example 1 was inorganic salt (lithium chloride) → sodium hydroxide → acrylic acid → crosslinker → carrageenan → initiator

[0144] At room temperature, 0.8478 g of lithium chloride was dissolved in 7.25 mL of deoxygenated deionized water, and then 1.6 g of sodium hydroxide was added. After stirring and mixing evenly, 2.75 mL of acrylic acid and 6.15 mg of the chemical crosslinker N,N′-methylenebisacrylamide were continuously added to the solution. Stirring was continued until the solution became clear and transparent. 0.15 g of carrageenan was added at a rate of 0.15 g / min, and stirring was carried out for 10 min. Finally, 29.22 mg of the photoinitiator α-ketoglutaric acid was added, and at this time, the reaction solution would undergo a phase change and become turbid. The reaction liquid was ultrasonically treated for 5 min to remove bubbles, and then the bubble-free reaction liquid was injected into a mold and sealed. The mold containing the bubble-free reaction liquid was ultrasonically treated again, and then placed under an ultraviolet lamp with a power of 120 W and a wavelength of 365 nm for irradiation to initiate a polymerization reaction. The irradiation time was 1 h, and the final hydrogel was obtained.

[0145] The tensile strength of the hydrogel prepared in Comparative Example 1 was 75 kPa, the elongation at break was 470%, and the conductivity was 30 mS / cm. The hydrogel prepared in Comparative Example 1 was stretched to 300% at a rate of 100 mm / min and immediately recovered. The hysteresis percentage of the hydrogel was 26%, and the residual strain was 15.6%.

[0146] Figure 5 It is the tensile stress-strain diagram of the hydrogel prepared by changing the feeding order in Comparative Example 1. From Figure 5 It can be seen that the tensile strength of the hydrogel prepared in Comparative Example 1 was 75 kPa, and the elongation at break was 470%. This shows that after changing the feeding order, the strength and elongation at break of the prepared hydrogel are significantly lower than those of the hydrogel prepared by the feeding order provided in the present invention. The mechanical properties of the hydrogel become worse, the tensile force and deformation that can be tolerated are smaller, and its use range is greatly limited when used as a strain sensor.

[0147] Figure 6 It is the tensile-recovery diagram (tensile strain 300%) of the hydrogel prepared by changing the feeding order in Comparative Example 1. From Figure 6 It can be seen that the hysteresis percentage of the hydrogel prepared in Comparative Example 1 was 26%, and the residual strain was 15.6%. This shows that after changing the feeding order, the hysteresis percentage and residual strain of the prepared hydrogel are significantly increased compared with the hydrogel prepared by the feeding order provided in the present invention. This represents that the hydrogel cannot quickly recover to its original state after being stretched, and there is a large energy loss during the deformation-recovery process, indicating that the hydrogel network is damaged during the stretching process and cannot be quickly rebuilt during the deformation-recovery process of the hydrogel. When the hydrogel prepared in Comparative Example 1 is used for a wearable strain sensor to withstand multiple repeated stretching-recovery, due to its ineffective recovery of deformation, it will cause hysteresis and distortion of the sensing signal, seriously affecting the accuracy of sensing.

[0148] It can be seen from Comparative Example 1 that after changing the feeding order, the solution of carrageenan after dispersion at room temperature undergoes phase separation, the system is uneven, the hydrogel prepared has poor mechanical strength, low elongation at break, a significant increase in the hysteresis percentage and residual strain, and the gel recovery performance is significantly deteriorated.

Claims

1. A method for preparing a fast-recovery, low-hysteresis conductive hydrogel, characterized in that: The steps include: (1) adding an inorganic salt to water and stirring to mix uniformly to obtain a solution 1; the inorganic salt is either lithium chloride or potassium chloride, and the ratio of the amount of the inorganic salt added to the total volume of the added water and acrylic acid is 1 mol / L to 2.5 mol / L; (2) adding sodium hydroxide to the solution 1 in step (1), stirring and mixing, and obtaining a solution 2; wherein the ratio of the amount of the added sodium hydroxide to the total volume of the added water and acrylic acid is 1 mol / L to 4 mol / L; (3) adding carrageenan to the solution 2 in step (2), stirring and mixing uniformly to obtain solution 3; (4) adding acrylic acid to the solution 3 in step (3) to obtain solution 4, and then adding a chemical crosslinking agent N,N'-methylenebisacrylamide, stirring and mixing to obtain solution 5; (5) adding an initiator to the solution 5 in step (4), stirring and mixing uniformly, removing bubbles by ultrasound to obtain a final reaction solution, injecting the reaction solution into a mold and sealing; the initiator is a photoinitiator or a redox initiator, wherein the photoinitiator is α-ketoglutaric acid, and the amount of the photoinitiator added is 0.1% to 1% of the amount of the acrylic acid added in step (4); the redox initiator is a redox initiation system composed of potassium persulfate and N,N,N',N'-tetramethylethylenediamine, the amount of the potassium persulfate added is 0.1% to 0.5% of the amount of the acrylic acid added in step (4), and the amount of the N,N,N',N'-tetramethylethylenediamine added is 0.1% to 1% of the amount of the acrylic acid added in step (4); (6) The mold containing the final reaction solution is ultrasonicated again, and then a polymerization reaction is carried out to obtain the conductive hydrogel with fast recovery and low hysteresis.

2. The method for preparing a fast-recovery, low-hysteresis conductive hydrogel according to claim 1, wherein: In step (3), the stirring and mixing is carried out at room temperature, the carrageenan is Kappa carrageenan, and the ratio of the mass of the added carrageenan to the total volume of the added water and acrylic acid is 5g / L to 30g / L; the stirring and mixing time is 5min to 20min.

3. The method for preparing a fast-recovery, low-hysteresis conductive hydrogel according to claim 1, wherein: The amount of the chemical cross-linking agent N,N'-methylenebisacrylamide added in step (4) is 0.01% to 0.15% of the amount of the acrylic acid added.

4. The method for preparing a fast-recovery, low-hysteresis conductive hydrogel according to claim 1, wherein: When a photoinitiator is used in the polymerization reaction in step (6), the ultraviolet wavelength used to initiate the reaction is 200nm to 400nm, and the power of the ultraviolet lamp is 60W to 180W; when an oxidation-reduction initiator is used in the polymerization reaction in step (6), the polymerization temperature is 15°C to 30°C.

5. The method for preparing a fast-recovery, low-hysteresis conductive hydrogel according to claim 1, characterized in that: The polymerization reaction time in step (6) is 0.5 to 4 hours.

6. A fast-recovery, low-hysteresis conductive hydrogel prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the fast-recovery, low-hysteresis conductive hydrogel according to claim 6 in a wearable hydrogel strain sensor.

Images