Highly Antifreeze Self-Conductive Hydrogel with Inorganic-Organic Double Cross-Linked Network Structure and Preparation Method Thereof

Abstract

The present invention belongs to the field of multifunctional materials, and relates to a highly antifreeze self-conductive hydrogel with an inorganic-organic double cross-linked network structure and a preparation method thereof. The method comprises: in the presence of an alcohol solvent, mixing an iron salt solution with an ammonium molybdate aqueous solution, stirring thoroughly until viscous and forming a gel, the iron-molybdenum molar ratio is 1-2:1, the volume ratio of the alcohol solvent to water in the system is 0.8-1.2:1, and the alcohol solvent is ethylene glycol and / or propylene glycol. The hybrid inorganic hydrogel provided by the present invention has self-conductive properties, excellent antifreeze and water retention, a simple green and pollution-free preparation method, green, environmentally friendly, low-carbon and degradable materials, and recyclable mineral materials. It is cheap and low-cost, and has high biocompatibility and is non-toxic to the human body.

Description

Technical Field

[0001] The present invention belongs to the field of multifunctional materials, and relates to a highly antifreeze self-conductive hydrogel with an inorganic-organic double cross-linked network structure and a preparation method thereof. Background Art

[0002] Hydrogels are soft materials composed of water and a three-dimensional polymer network, and the cross-linking points in the network are chemical cross-linking points formed by covalent bonds or physical cross-linking points formed by non-covalent bonds such as ionic bonds, hydrogen bonds, hydrophobic interactions, and coordination interactions. As a new type of multifunctional material, it has been widely studied and applied in the fields of medicine, energy catalysis, and many engineering fields. Most traditional hydrogels are organic gels mainly based on organic raw materials, although they play a prominent role in gel research (for example, in the directions of biosensing, drug delivery, energy storage, and tissue engineering) (Decoppet, J.D.; Moehl, T.; Babkair, S.S.; Alzubaydi, R.A.; Ansari, A.A.; Habib, S.S.; Zakeeruddin, S.M.; Schmidt, H.W.; M., Molecular gelation of ionic liquid–sulfolane mixtures, a solid electrolyte for high performance dye-sensitized solar cells. Journal of Materials Chemistry A 2014, 2(38), 15972-15977.). Organic gels exhibit poor ionic conductivity, which can only be solved through specialized modification. To improve ionic conductivity, ionic liquids or eutectic solvents can be gelled to form ionic gels and eutectic gels respectively. However, this process is complicated and difficult to control the addition conditions, and the ionic liquids are expensive, greatly increasing the experimental cost. Moreover, when organic gels are immersed in solutions, they usually undergo significant volume expansion, thus affecting stability and mechanical strength. To reduce unexpected swelling, researchers have achieved complex designed gel systems, including various network organohydrogels, double network hydrogels (DN), triple network hydrogels (TN), and interpenetrating network hydrogels (IPN) (Wu, Q.; Qi, S.; Zhao, T.; Yan, H.; Liu, M., Multiple network organohydrogels with high strength and anti-swelling properties in different solvents. Giant 2021, 6, 100058.). Despite these important advances, organic gels themselves usually have problems such as low thermal stability, high flammability, susceptibility to light damage, and inconvenience in manufacturing involving toxic organic solvents, and petroleum products are inevitably used in the production process. In contrast, if inorganic mineral gels can be effectively realized, these problems that plague traditional organic gels can be systematically remedied.Its strong ionic properties can better accommodate mobile ionic additives and transition metal salts to endow richer chemical functions (e.g., for catalysis or energy storage) (Addamo, M.; Bellardita, M.; Carriazo, D.; Di Paola, A.; Milioto, S.; Palmisano, L.; Rives, V., Inorganic gels as precursors of TiO2 photocatalysts prepared by low temperature microwave or thermal treatment. Applied Catalysis B: Environmental 2008, 84(3), 742 - 748.); its relatively hard and stable inorganic framework will not easily expand and burn, while providing stronger resistance to light damage and thermal degradation. At present, the research on inorganic hydrogels is in its infancy. The water in the hydrogel is easy to evaporate at room temperature, and most inorganic hydrogels have poor environmental stability and are easy to freeze at low temperatures. When the water content is lost or the hydrogel freezes, its strain sensitivity, mechanical properties, and service life will be greatly affected, resulting in the loss of some inherent properties of the inorganic hydrogel, such as conductivity, elasticity, transparency, and flexibility, which greatly limits its application in practical engineering. For example, a dual-responsive mechanical and tribological adaptive hydrogel composed of graphene oxide and water, although it has good pH responsiveness and temperature responsiveness, its temperature response range is limited to 25 °C to 75 °C, and it cannot respond at low temperatures and has poor water retention performance in air (Hu, L.; Yang, Y.; Hao, J.; Xu, L., Dual-Driven Mechanically and Tribologically Adaptive Hydrogels Solely Constituted of Graphene Oxide and Water. Nano Letters 2022, 22(14), 6004 - 6009.). Summary of the Invention

[0003] Objective of the Invention: In view of the deficiencies of the above-mentioned prior art, the objective of the present invention is to provide a highly freeze-resistant self-conductive hydrogel with an inorganic-organic double cross-linked network structure and a preparation method thereof. The highly freeze-resistant self-conductive hydrogel with an inorganic-organic double cross-linked structure is an inorganic-organic double network structure cross-linked by hydroxyl bridges between inorganic materials and high-density strong hydrogen bonds. Through the cross-linking of hydroxyl bridges between inorganic materials, the hydrogel has self-conductive properties. The solvents in the system are cross-linked by strong hydrogen bonds, thus playing a water-locking effect and reducing the freezing point of water, and can maintain lasting freeze resistance and water retention performance at -20°C.

[0004] In order to achieve the objective of the present invention, the technical solution adopted is as follows:

[0005] The present invention provides a highly freeze-resistant self-conductive hydrogel with an inorganic-organic double cross-linked network structure and a preparation method thereof, including the following steps: In the presence of an alcohol solvent, mix an iron salt solution with an ammonium molybdate aqueous solution, stir well until it becomes viscous and forms a gel. The iron-molybdenum molar ratio is 1-2:1, and the volume ratio of the alcohol solvent to water in the system is 0.8-1.2:1 (preferably 1:1). The alcohol solvent is ethylene glycol and / or glycerol.

[0006] Compared with the gels prepared with organic solvents in the past, the conductive inorganic hydrogel obtained by the above method has strong self-conductive ability, a simple preparation method, and the synthetic materials are green and environmentally friendly and non-toxic to the human body.

[0007] Further, in order to further improve the conductivity and moisture retention of the hydrogel, the following steps are also included: Pour the ammonium molybdate aqueous solution into the sodium alginate solution and stir, then pour the iron salt solution into the mixed solution of ammonium molybdate and sodium alginate, and stir well until a gel is formed. By cross-linking biomass sodium alginate with iron ions, the water is locked more firmly, and a sodium alginate-molybdenum iron hybrid inorganic gel with excellent freeze resistance and water retention is prepared.

[0008] The volume of the sodium alginate solution is equal to the volume of the alcohol solvent and water used, and the mass concentration range of the sodium alginate solution is 3% to 5%.

[0009] Furthermore, the mixing and stirring time of the sodium alginate solution and ammonium molybdate is 0.5-1 h.

[0010] Further, the iron salt is any one or more of ferric chloride, ferric chloride hydrate, ferric nitrate, and ferric nitrate hydrate.

[0011] Compared with the prior art, the present invention has the following main advantages and beneficial effects:

[0012] 1. The hydrogel prepared by the present invention by introducing an alcohol solvent has an inorganic-organic double cross-linked network structure, has high antifreeze performance and self-conductivity, especially significantly improves the conductivity at low temperatures. The hydrogel preparation method is simple, low in cost and non-toxic to the human body, and is environmentally friendly.

[0013] 2. The self-conductive hydrogel with an inorganic-organic double cross-linked network structure prepared by the present invention has excellent wide-temperature tolerance, shows good antifreeze performance and water retention property in the temperature range from -20°C to 60°C, and has broad application fields in aspects such as antifreeze and water retention. Description of the Drawings

[0014] Figure 1 It is a schematic scanning electron microscope diagram at 200 nm of the self-conductive hydrogel with an inorganic-organic double cross-linked network structure using water as the dispersion medium prepared by the above method.

[0015] Figure 2 It is a comparison chart of the water retention time at room temperature of the hydrogels of Examples 1, 2, 3, 4, 5, 6, 7, 8, and 9.

[0016] Figure 3 It is a comparison chart of the elasticity display of the self-conductive hydrogel with an inorganic-organic double cross-linked network structure prepared using ethylene glycol as the dispersion medium after being placed for one month at (-20°C) and the molybdate iron inorganic hydrogel after being placed for one month at (-20°C).

[0017] Figure 4 It is a comparison chart of the conductivity of the hydrogels of Examples 1, 2, 3, 6, and 7 after being placed at room temperature and at -20°C.

[0018] Figure 5 It is a comparison chart of the brightness of the light emitted by the small light bulb when the highly antifreeze self-conductive hydrogels "SA(5%)-Gel-glycol-1M" (left) and "SA(5%)-Gel-1M" (right) with an inorganic-organic double cross-linked network structure are used as conductors. Detailed Description of the Invention

[0019] The present invention is not limited to the following specific embodiments. Those of ordinary skill in the art can implement the present invention in other various specific embodiments according to the content disclosed in the present invention, or those that adopt the design structure and idea of the present invention and make simple changes or modifications all fall within the protection scope of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0020] The present invention is further described in detail below in conjunction with embodiments:

[0021] Example 1:

[0022] (1) Weigh 1.35 g of FeCl3·6H2O into a 50-ml beaker, add 5 ml of deionized water, and dissolve it by ultrasonic treatment. Weigh 0.883 g of (NH4)6Mo7O 24 ·4H2O into a 50-ml beaker, add 5 ml of deionized water, and dissolve it by ultrasonic treatment. The molar ratio of iron to molybdenum in the system is 1:1. Pour the ammonium molybdate solution into the iron chloride solution, and a large amount of precipitate is immediately generated. After starting to mix and stir at room temperature, the precipitate immediately dissolves. Continue stirring, and the solution gradually becomes viscous. A yellowish-green gel is formed in about 10 min. Name the obtained inorganic mineral gel Gel-1M.

[0023] (2) Take 2 g of Gel-1M prepared in step (1) and put it into a sealed bag, then place it in a refrigerator at -20 °C. Conduct the freeze resistance test every 10 min, observe the morphological changes of the gel, and record its freeze resistance performance. Through observation and recording, the inorganic mineral gel hardens, freezes, and loses its viscoelasticity in about 40 min.

[0024] (3) Take 1 g of Gel-1M prepared in step (1) and place it on a weighing paper, then expose it to the air. Observe the morphological changes of the gel every 1 h and record its mass change to reflect the water retention performance. Through observation, the inorganic mineral gel shows a slightly dry phenomenon in about 1 h, a cracking phenomenon appears after 2 h, and it completely cracks into several small pieces and automatically falls off the weighing paper in about 4 h.

[0025] (4) Weigh 30 mg of Gel-1M prepared in (1) into a 100-ml beaker, add 50 ml of deionized water, and disperse it by ultrasonic treatment for 1 h. The measured conductivity is 145 μS / cm.

[0026] (5) Weigh 30 mg of Gel-1M that has been placed in a refrigerator at -20 °C for 30 days in (2) into a 100-ml beaker, add 50 ml of deionized water, and disperse it by ultrasonic treatment for 1 h. The measured conductivity is 119 μS / cm.

[0027] Through the above observation experiments, it can be determined that the inorganic iron molybdate hydrogel prepared with water as the solvent has poor water retention, a short storage time in the air, poor freeze resistance, and cannot maintain its original performance under low-temperature conditions.

[0028] Example 2:

[0029] (1) Weigh 1.35 g of FeCl3·6H2O into a 50-ml beaker, add 5 ml of ethylene glycol, and dissolve it by ultrasonic treatment. Weigh 0.883 g of (NH4)6Mo7O 24Add 5 ml of deionized water to 1.35 g of FeCl3·6H2O in a 50 ml beaker and dissolve it by ultrasonic treatment. Add 5 ml of deionized water to 0.883 g of (NH4)6Mo7O24·4H2O in a 50 ml beaker and dissolve it by ultrasonic treatment. The volume ratio of ethylene glycol to deionized water is 1:1. The molar ratio of iron to molybdenum in the system is 1:1. Pour the ammonium molybdate solution into the iron chloride solution, and a large amount of precipitate will be produced immediately. After starting to mix and stir at room temperature, the precipitate will dissolve immediately. Continue stirring, and the solution will gradually become viscous. A yellow-green gel will be formed in about 1 h. Name the obtained hydrogel Gel-glycol-1M.

[0030] (2) Take 2 g of Gel-glycol-1M prepared in step (1) and put it into a sealed bag, then place it in a refrigerator at -20 °C. Test the freeze resistance every 10 min, observe the change in the gel morphology and record its freeze resistance. Through observation and record, Gel-glycol-1M is not frozen after 30 days, still has elastic viscosity and the conductivity increases.

[0031] (3) Take 1 g of Gel-glycol-1M prepared in step (1) and place it on a weighing paper, then expose it to the air. Observe the change in the gel morphology every 1 h and record its mass change to reflect the water retention performance. Through observation, when exposed to the air at room temperature for 96 h, the water retention of Gel-glycol-1M is intact, and there is no phenomenon of cracking and peeling. After 96 h, it begins to dry slightly.

[0032] (4) Weigh 30 mg of Gel-glycol-1M prepared in (1) into a 100 ml beaker, add 50 ml of deionized water, and disperse it by ultrasonic treatment for 1 h. The measured conductivity is 214 μS / cm.

[0033] (5) Weigh 30 mg of Gel-glycol-1M that has been placed in a refrigerator at -20 °C for 30 days in (2) into a 100 ml beaker, add 50 ml of deionized water, and disperse it by ultrasonic treatment for 1 h. The measured conductivity is 267 μS / cm.

[0034] Example 3:

[0035] (1) Weigh 1.35 g of FeCl3·6H2O into a 50 ml beaker, add 5 ml of glycerol, and dissolve it by ultrasonic treatment. Weigh 0.883 g of (NH4)6Mo7O24 24 ·4H2O into a 50 ml beaker, add 5 ml of deionized water, and dissolve it by ultrasonic treatment. The volume ratio of ethylene glycol to deionized water is 1:1. The molar ratio of iron to molybdenum in the system is 1:1. Pour the ammonium molybdate solution into the iron chloride solution, and a large amount of precipitate will be produced immediately. After starting to mix and stir at room temperature, the precipitate will dissolve immediately. Continue stirring, and the solution will gradually become viscous. A yellow-brown gel will be formed in about 5 h. Name the obtained hydrogel Gel-glycerol-1M.

[0036] (2) Take 2 g of the Gel-glycerol-1M prepared in step (1) and place it in a sealed bag. Put it into a refrigerator at -20°C and conduct the freeze resistance test every 10 minutes. Observe the morphological changes of the gel and record its freeze resistance performance. Through observation and recording, after 30 days, Gel-glycerol-1M did not freeze, still had elastic viscosity, and the conductivity increased.

[0037] (3) Take 1 g of the Gel-glycerol-1M prepared in step (1) and place it on a weighing paper. Expose it to the air and observe the morphological changes of the gel every 1 hour and record its mass change to reflect the water retention performance. Through observation, when exposed to the air at room temperature for 168 hours, the water retention of Gel-glycerol-1M was intact, and there was no phenomenon of cracking and shedding. After 168 hours, it began to dry slightly.

[0038] (4) Weigh 30 mg of the Gel-glycerol-1M prepared in (1) into a 100 ml beaker, add 50 ml of deionized water, and ultrasonically disperse for 1 hour. The measured conductivity is 192 μS / cm.

[0039] (5) Weigh 30 mg of the Gel-glycerol-1M that has been placed in a refrigerator at -20°C for 30 days in (2) into a 100 ml beaker, add 50 ml of deionized water, and ultrasonically disperse for 1 hour. The measured conductivity is 261 μS / cm.

[0040] Through the above observation experiments, it can be determined that the inorganic hydrogel prepared with ethylene glycol / glycerol as the solvent has better water retention performance than the inorganic hydrogel prepared with water as the solvent, can be stored in the air for a longer time, has good freeze resistance performance, can maintain the original elastic viscosity under low temperature conditions, and the conductivity increases after freezing for 30 days.

[0041] Example 4:

[0042] (1) Weigh 1.35 g of FeCl3·6H2O into a 50 ml beaker, add 5 ml of deionized water, and ultrasonically dissolve. Weigh 0.883 g of (NH4)6Mo7O 24 ·4H2O into a 50 ml beaker, add 5 ml of deionized water, and ultrasonically dissolve. The volume ratio of deionized water is 1:1. The molar ratio of iron to molybdenum in the system is 1:1. Weigh 5 g of sodium alginate and pour it into 95 ml of deionized water, and stir for 1 hour under a water bath at 90°C. Pour the ammonium molybdate solution into 10 ml of 5% SA solution and stir at room temperature for 1 hour, then pour it into the iron chloride solution, and immediately crosslink to form a yellow-green gel. Name the obtained self-conductive hydrogel with an inorganic-organic double cross-linked network structure as SA(5%)-Gel-1M.

[0043] (2) Take 2 g of the SA(5%)-Gel-1M prepared in step (1) and place it in a sealed bag. Put it into a refrigerator at -20 °C and conduct the freeze resistance test every 10 minutes. Observe the morphological changes of the gel and record its freeze resistance performance. Through observation and recording, after 70 minutes, SA(5%)-Gel-1M freezes and loses its flexibility and elasticity.

[0044] (3) Take 1 g of the SA(5%)-Gel-1M prepared in step (1) and place it on a weighing paper. Expose it to the air and observe the morphological changes of the gel every 1 hour and record its mass change to reflect the water retention performance. Through observation, when exposed to the air at room temperature for 24 hours, SA(5%)-Gel-1M gradually dries out, but there is no phenomenon of cracking and peeling off, and the mass of SA(5%)-Gel-1M no longer changes.

[0045] Example 5:

[0046] (1) Weigh 1.35 g of FeCl3·6H2O into a 50 ml beaker, add 5 ml of ethylene glycol, and dissolve it by ultrasonic wave. Weigh 0.883 g of (NH4)6Mo7O 24 ·4H2O into a 50 ml beaker, add 5 ml of deionized water, and dissolve it by ultrasonic wave. The volume ratio of deionized water is 1:1. The molar ratio of iron to molybdenum in the system is 1:1. Weigh 5 g of sodium alginate and pour it into 95 ml of deionized water, stir it in a water bath at 90 °C for 1 hour. Pour the ammonium molybdate solution into 10 ml of 5% SA solution and stir it at room temperature for 1 hour, then pour it into the iron chloride solution and immediately crosslink to form a yellow-green gel. Name the obtained self-conductive hydrogel with an inorganic-organic double cross-linked network structure as SA(5%)

[0047] -Gel-glycol-1M.

[0048] (2) Take 2 g of the SA(5%)-Gel-glycol-1M prepared in step (1) and place it in a sealed bag. Put it into a refrigerator at -20 °C and conduct the freeze resistance test every 10 minutes. Observe the morphological changes of the gel and record its freeze resistance performance. Through observation and recording, after 30 days, SA(5%)-Gel-glycol-1M does not freeze, still has elasticity and the conductivity increases.

[0049] (3) Take 1 g of the SA(5%)-Gel-glycol-1M prepared in step (1) and place it on a weighing paper. Expose it to the air and observe the morphological changes of the gel every 1 hour and record its mass change to reflect the water retention performance. Through observation, when exposed to the air at room temperature for more than 288 hours, the water retention property of SA(5%)-Gel-glycol-1M is intact, there is no phenomenon of cracking and peeling off, and the mass of SA(5%)-Gel-glycol-1M no longer changes.

[0050] Example 6:

[0051] Compared with Example 1, the difference in Example 6 is that the molar ratio of iron to molybdenum in step (1) is 2:1, and other operations are the same as those in Example 1. The obtained inorganic mineral gel is named Gel-2M.

[0052] (1) Take 2 g of Gel-2M prepared in step (1) and put it in a sealed bag, then place it in a refrigerator at -20 °C. Conduct the freeze resistance test every 10 minutes, observe the morphological changes of the gel and record its freeze resistance performance. Through observation and recording, Gel-2M freezes and loses its toughness after 60 minutes, but its freeze resistance time is longer than that of Gel-1M.

[0053] (2) Take 1 g of Gel-2M prepared in step (1) and place it on a weighing paper, then expose it to the air. Observe the morphological changes of the gel every 1 hour and record its mass change to reflect the water retention performance. Through observation, after being exposed to the air at room temperature for 12 hours, Gel-2M shows cracking and peeling phenomena.

[0054] (3) Weigh 30 mg of Gel-2M prepared in (1) into a 100 ml beaker, add 50 ml of deionized water, and ultrasonically disperse for 1 hour. The measured conductivity is 638 μS / cm, which is much higher than that of the iron molybdate inorganic hydrogel prepared with a molar ratio of iron to molybdenum of 1:1 in the system.

[0055] (5) Weigh 30 mg of Gel-2M that has been placed in a refrigerator at -20 °C for 30 days in (2) into a 100 ml beaker, add 50 ml of deionized water, and ultrasonically disperse for 1 hour. The measured conductivity is 523 μS / cm, which has decreased by 18% compared with that before freezing.

[0056] Example 7:

[0057] Compared with Example 2, the difference in Example 7 is that the molar ratio of iron to molybdenum in step (1) is 2:1, and other operations are the same as those in Example 2. The obtained inorganic mineral gel is named Gel-glycol-2M.

[0058] Conduct freeze resistance and water retention tests on the inorganic gel Gel-glycol-2M. The specific test methods are as follows:

[0059] (1) Take 2 g of Gel-glycol-2M and put it in a sealed bag, then place it in a refrigerator at -20 °C. Conduct the freeze resistance test every 10 minutes, observe the morphological changes of the gel and record its freeze resistance performance. Through observation and recording, Gel-glycol-2M does not freeze after 30 days, still has elastic viscosity and its conductivity is 784 μS / cm, while the conductivity of Gel-glycol-2M before freezing is 730 μS / cm, increasing by 7.4%.

[0060] (2) Take 1 g of the prepared Gel-glycol-2M and place it on a weighing paper. Expose it to the air and observe the morphological changes of the gel every 1 h and record its mass change to reflect the water retention performance. Through observation, after being exposed to the air for 240 h at room temperature, the mass of Gel-glycol-2M no longer changes, indicating that water loss is complete and there are no cracks on the hydrogel surface.

[0061] (3) Weigh 30 mg of the prepared Gel-glycol-2M into a 100 ml beaker, add 50 ml of deionized water, and disperse it ultrasonically for 1 h. The measured conductivity is 730 μS / cm.

[0062] Weigh 30 mg of Gel-glycol-2M that has been placed in a refrigerator at -20 °C for 30 days into a 100 ml beaker, add 50 ml of deionized water, and disperse it ultrasonically for 1 h. The measured conductivity is 784 μS / cm.

[0063] Example 8:

[0064] Compared with Example 4, Example 8 is different in that: in step (1), the molar ratio of iron to molybdenum is 2:1, and other operations are the same as those in the steps of Example 4. The obtained self-conductive hydrogel with an inorganic-organic double cross-linked network structure is named SA(5%)-Gel-2M.

[0065] The antifreeze property and water retention property of the hydrogel SA(5%)-Gel-2M are detected. The specific detection method is as follows:

[0066] (1) Take 2 g of SA(5%)-Gel-2M and put it in a sealed bag, then place it in a refrigerator at -20 °C. Conduct the antifreeze test every 10 min, observe the morphological changes of the gel and record its antifreeze performance. Through observation and record,

[0067] After 90 min, SA(5%)-Gel-2M freezes, loses its flexibility and elasticity, and the antifreeze time is slightly longer than that of SA(5%)-Gel-1M.

[0068] (2) Take 1 g of the SA(5%)-Gel-2M prepared in step (1) and place it on a weighing paper. Expose it to the air and observe the morphological changes of the gel every 1 h and record its mass change to reflect the water retention performance. Through observation, after being exposed to the air for 40 h at room temperature, the water retention property of SA(5%)-Gel-2M is intact, there is no phenomenon of cracking and shedding, and the mass of SA(5%)-Gel-2M no longer changes.

[0069] Example 9:

[0070] Example 9 is different from Example 5 in that: in step (1), the molar ratio of iron to molybdenum is 2:1, and other operations are the same as those in the steps of Example 4. The obtained self-conductive hydrogel with an inorganic-organic double cross-linked network structure is named SA(5%)-Gel-glycol-2M.

[0071] The antifreeze property and water retention property of the hydrogel SA(5%)-Gel-glycol-2M were detected. The specific detection method is as follows:

[0072] (1) Take 2 g of SA(5%)-Gel-glycol-2M and put it in a sealed bag, then place it in a refrigerator at -20°C. The antifreeze property was tested every 10 minutes. Observe the morphological changes of the gel and record its antifreeze performance. Through observation and record, after 30 days of placement, SA(5%)-Gel-glycol-2M did not freeze and did not lose its flexibility and elasticity.

[0073] (2) Take 1 g of the SA(5%)-Gel-glycol-2M prepared in step (1) and place it on a weighing paper, then expose it to the air. Observe the morphological changes of the gel every 1 hour and record its mass change to reflect the water retention property. Through observation, after being exposed to the air at room temperature for 360 hours, the water retention property of SA(5%)-Gel-glycol-2M was intact, and the mass of SA(5%)-Gel-2M no longer changed.

[0074] Figure 1 Figure shows the SEM image of the self-conductive hydrogel with an inorganic-organic double cross-linked structure in Example 4 at 200 nm. It can be clearly seen from the figure the nanofiber structure of the hydrogel.

[0075] Figure 2 Figure shows the comparison chart of the water retention time of the hydrogels of Examples 1, 2, 3, 4, 5, 6, 7, 8, and 9 at room temperature. It can be clearly seen from the figure that: from the comparison of Examples 1, 2, and 3, for the inorganic hydrogels prepared under the conditions of using water, ethylene glycol, and glycerol as solvents, the water retention time of the hydrogel with glycerol as the solvent is the longest, followed by the hydrogel with ethylene glycol as the solvent, and the water retention time of the inorganic gel with water as the solvent is 20 - 40 times shorter. The conductivity of the inorganic hydrogel is the highest for the inorganic hydrogel with ethylene glycol added, followed by the inorganic hydrogel with glycerol added, and the conductivity of the iron molybdate inorganic hydrogel is the lowest. Thus, it can be seen that introducing ethylene glycol and glycerol not only enhances the water retention property and antifreeze property of the inorganic gel, but also effectively improves the conductivity of the ionic gel, proving that ethylene glycol and glycerol also participate in the cross-linking reaction of the gel and form strong hydrogen bonds with water molecules, thus playing the role of water retention and antifreeze.

[0076] From the comparison of Examples 1, 2, 3, 4, and 5, it can be seen that the introduction of biomass sodium alginate can continue to cross-link with excessive iron ions to lock water more firmly. The antifreeze and water retention properties of the self-conductive hydrogel with an inorganic-organic double cross-linked network structure are much better than those of the iron molybdate inorganic hydrogel.

[0077] From the experimental results of Examples 6, 7, 8, and 9 above, it can be concluded that after the iron ion concentration in the system is increased, the antifreeze and water retention effects of the inorganic hydrogel can be improved, and at the same time, the conductivity is also greatly increased. It is because after the iron ions are in excess, hydrolysis can cause the system to generate more H + Combined with MoO4 2－ to form H2MoO4, and more hydroxyl groups in the iron hydroxy molybdate are formed to form more hydroxyl bridges to make the cross-linking more firm.

[0078] Figure 3 Comparison diagram of the elasticity of the inorganic iron molybdate hydrogel "Gel-1M", the antifreeze hydrogel "Gel-glycol-1M" prepared with ethylene glycol as the solvent, and the self-conductive hydrogel "SA(5%)Gel-glycol-1M" with an inorganic-organic double cross-linked network structure after being placed in an environment of (-20 °C) for one month ( Figure 3 In (c), the left figure is SA(5%)-Gelglycol-2M at 25 °C, and the right figure is SA(5%)-Gelglycol-2M at -20 °C). As can be seen from the figure, the introduction of ethylene glycol as the solvent can strengthen the hydrogen bond interaction in the reaction. Strong hydrogen bonds are formed between ethylene glycol and water, thus playing a water-locking effect and reducing the freezing point of water, so that its mechanical and electrochemical properties can still be maintained at sub-zero temperatures. And the introduction of biomass sodium alginate can cross-link and hybridize with the iron ions in the system to form an inorganic-organic double cross-linked network structure, making the structure of the hydrogel more three-dimensional and having better water retention and antifreeze effects.

[0079] Comparative Example 1

[0080] Compared with Example 4, the difference in Comparative Example 1 is that the mass percentage of sodium alginate is 1%, that is, 1 g of sodium alginate is weighed and poured into 99 ml of deionized water, and stirred at 90 °C in a water bath for 1 h. The ammonium molybdate solution is poured into 10 ml of 1% SA solution and stirred at room temperature for 1 h, and then poured into the iron chloride solution, and no hydrogel can be formed.

[0081] Comparative Example 2

[0082] Compared with Example 4, the difference in Comparative Example 2 is that the mass percentage of sodium alginate is 2%, that is, 2 g of sodium alginate is weighed and poured into 98 ml of deionized water, and stirred at 90 °C in a water bath for 1 h. The ammonium molybdate solution is poured into 10 ml of 1% SA solution and stirred at room temperature for 1 h, and then poured into the iron chloride solution, and no hydrogel can be formed.

[0083] Comparative Example 3:

[0084] Comparative Example 3 is different from Example 4 in that the mass percentage of sodium alginate is 3%, that is, 3 g of sodium alginate is weighed and poured into 97 ml of deionized water, and stirred for 1 h under heating in a water bath at 90 °C. The ammonium molybdate solution is poured into 10 ml of 1% SA solution and stirred at room temperature for 1 h, and then poured into the iron chloride solution to form a hydrogel with a relatively fragile structure.

[0085] From the comparison of Comparative Examples 1, 2, 3 and Example 4, it can be seen that when the mass percentage of sodium alginate is at least 3%, a self-conductive hydrogel with an inorganic-organic double cross-linked network structure can be successfully prepared.

[0086] Figure 4 It is a comparison chart of the conductivity of the hydrogels of Examples 1, 2, 3, 6, 7 and after being placed at room temperature and in an environment of -20 °C. As can be seen from the figure, the ionic conductivity of Example 1 is 145 μS / cm, and the conductivity after freezing decreases to 119 μS / cm, a decrease of 17.9%; the ionic conductivity of Example 2 is 214 μS / cm, and the conductivity after freezing increases to 267 μS / cm, an increase of 24.8%; the ionic conductivity of Example 3 is 192 μS / cm, and the conductivity after freezing increases to 261 μS / cm, an increase of 35.9%; the ionic conductivity of Example 6 is 638 μS / cm, and the conductivity after freezing decreases to 523 μS / cm, a decrease of 18.02%; the ionic conductivity of Example 7 is 730 μS / cm, and the conductivity after freezing increases to 784 μS / cm, an increase of 7.4%. It shows that by introducing ethylene glycol and glycerol as a mixed solvent, the ionic conductivity of the hydrogel is effectively improved. This is because ethylene glycol and glycerol also participate in the cross-linking reaction of the hydrogel, form strong hydrogen bond interactions with water molecules, thus playing a water-locking effect, enhancing the water retention and freeze resistance of the hydrogel, and at the same time reducing the impedance.

[0087] Figure 5 It is a comparison chart of the brightness of the small light bulb when the highly freeze-resistant self-conductive hydrogel "SA(5%)-Gel-glycol-1M" with an inorganic-organic double cross-linked network structure and "SA(5%)-Gel-1M" are used as conductors. The small light bulb with "SA(5%)-Gel-glycol-1M" as the conductor is brighter, thus proving that the hydrogel prepared by adding ethylene glycol as a solvent has better conductivity.

[0088] Comparative Example 4:

[0089] Comparative Example 4 is different from Example 1 in that: the molar ratio of iron to molybdenum in step (1) is 3:1, and other operations are the same as those in step of Example 1. At this time, the content of molybdic acid in the system is too low to generate sufficient hydroxyl groups to react with FeMo2O x (OH) y to form a stable gel by crosslinking.

[0090] Comparative Example 5:

[0091] Comparative Example 5 is different from Example 2 in that: the volume ratio of ethylene glycol to deionized water in step (1) is 2:1. Other operations are the same as those in step of Example 1. At this time, no gel can be formed.

[0092] Comparative Example 6:

[0093] Comparative Example 6 is different from Example 3 in that: the volume ratio of glycerol to deionized water in step (1) is 2:1. Other operations are the same as those in step of Example 1. At this time, no gel can be formed.

[0094] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

[0095] To sum up, the above are only the preferred embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a highly antifreeze and self-conductive hydrogel with an inorganic-organic double cross-linked network structure, characterized in that, It includes the following steps: in the presence of an alcohol solvent, mixing an iron salt solution with an aqueous ammonium molybdate solution, and stirring thoroughly until it becomes viscous and forms a gel. The molar ratio of iron to molybdenum is 1-2:1, the volume ratio of the alcohol solvent to water in the system is 0.8-1.2:1, and the alcohol solvent is ethylene glycol and / or glycerol.

2. The preparation method of the highly antifreeze self-conductive hydrogel with an inorganic-organic double cross-linked network structure according to claim 1, characterized in that, The iron salt is any one or more of ferric chloride, ferric chloride hydrate, ferric nitrate, and ferric nitrate hydrate.

3. The preparation method of the highly antifreeze self-conductive hydrogel with an inorganic-organic double cross-linked network structure according to claim 1 or 2, characterized in that, It also includes the following steps: pouring the aqueous ammonium molybdate solution into the sodium alginate solution and stirring, then pouring the iron salt solution into the mixed solution of ammonium molybdate and sodium alginate, and stirring thoroughly until a gel is formed; The volume of the sodium alginate solution is equal to the volume of the alcohol solvent and water used, and the mass concentration range of the sodium alginate solution is 3% - 5%.

4. The preparation method of the highly antifreeze and self-conductive hydrogel with an inorganic-organic double cross-linked network structure according to claim 3, characterized in that, The mixing and stirring time of the sodium alginate solution and ammonium molybdate is 0.5 - 1 h. A highly antifreeze self-conductive hydrogel with an inorganic-organic double cross-linked network structure prepared by the method according to any one of claims 1 to 4.

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