Preparation method of MXene organic hydrogel fiber with electromagnetic shielding function

Abstract

The present invention relates to the field of polymer materials. The present invention discloses a preparation method of an MXene organic hydrogel fiber with electromagnetic shielding function. In the present invention, a novel wave absorber, Mxene nanosheets, and hydroxypropyl cellulose are added to polyvinyl alcohol to improve the wave absorption ability. Conductive loss can be generated through the ion transport in the solvent channels of the fiber and the electron transport along the polymer network to attenuate the EM energy. At the same time, water molecules with inherent polarity can generate polarization loss through the rotation of dipoles under an alternating electromagnetic field. And through the solvent replacement method, high-concentration positive and negative ions and glycerol are introduced into the fiber, making the pores of the gel smaller and tighter, resulting in more incident EM waves being scattered and reflected. The introduced glycerol can also effectively alleviate the problems that the hydrogel is prone to drying and freezing at low temperatures, improving the water retention and low-temperature performance of the hydrogel.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly to a preparation method of MXene organic hydrogel fibers with electromagnetic shielding function. Background Art

[0002] Hydrogel is a 3D polymer network that can swell in water. This polymer network is in a solid state, and the aqueous phase of the hydrogel enables rapid diffusion of carriers, indicating that the hydrogel has liquid-like transport characteristics. Due to these good properties, many hydrogels have biocompatibility and softness. If a conductive hydrogel is made into one-dimensional fibers with orderly arranged polymer chains, the mechanical properties and conductivity of the conductive hydrogel fibers will be greatly enhanced compared to traditional conductive hydrogel films and bulk materials. However, due to the poor spinnability of current conductive hydrogels or their precursor solutions, conductive hydrogels are rarely made into long fibers by spinning. Therefore, conductive hydrogel fibers with good mechanical properties and excellent conductivity are highly needed for the development of stretchable electronic products.

[0003] So far, various types of shielding materials have been developed, such as metal films / meshes, carbonaceous foams. However, current EMI shielding materials face the challenges of simultaneously having flexibility, stretchability, biocompatibility, and high responsiveness to external stimuli, which limits their application in deformable and wearable electronic devices. Conductive hydrogels have the potential to provide EM radiation protection for deformable and wearable electronic devices due to their excellent conductivity, flexibility, ductility, and remarkable biological properties. Compared with other EMI shielding materials, the water in the hydrogel network can generate strong polarization loss to attenuate gigahertz electromagnetic waves, and the ions in it can also conduct current. In addition, the large deformability and self-healing ability of the hydrogel are very important for the recycling of shielding materials and preventing EM protection failure caused by mechanical damage. However, with pure water as the dispersion medium, hydrogel shielding materials will inevitably suffer from water evaporation and freezing below zero degrees, shortening their service life. For this reason, organic hydrogels can be prepared by introducing organic reagents such as ethylene glycol, glycerol, or sorbitol into the hydrogel. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a preparation method of MXene organic hydrogel fibers with electromagnetic shielding function. The present invention uses the wet spinning method to prepare hydrogel fibers, and long fibers can be easily obtained; MXene, as a new type of two-dimensional material, has high conductivity, high specific surface area, and rich polar functional groups, and is a very promising wave absorber. Adding MXene to the hydrogel can greatly improve the electromagnetic shielding performance of the hydrogel.

[0005] The specific technical solution of the present invention is as follows: A preparation method of an MXene organic hydrogel fiber with electromagnetic shielding function, comprising the following steps:

[0006] Step 1): Add 0.4 - 0.6 g of LiF to 10 mL of hydrochloric acid, stir and mix evenly, and then add 0.4 - 0.6 g of Ti 3 AlC 2 powder to the solution, and carry out an etching reaction by stirring the mixed solution at 30 - 40 °C for 20 - 30 hours.

[0007] Step 2): After the etching reaction is completed, wash the product with deionized water, and perform ultrasonic treatment on the etched product under an argon gas stream to form a dispersion.

[0008] Step 3): Centrifuge the dispersion and collect the supernatant, and obtain Mxene nanosheets after drying the supernatant.

[0009] Step 4): Take hydroxypropyl cellulose, add it to water and heat to disperse; add polyvinyl alcohol, raise the temperature and stir until the polyvinyl alcohol is completely dissolved, add Mxene nanosheets, and cool to room temperature to obtain a spinning solution.

[0010] Step 5): Defoam the spinning solution and inject it into a coagulation bath to form fibers, and let it stand for crosslinking to obtain hydrogel fibers.

[0011] Step 6): Clean the surface of the hydrogel fiber, remove the excess moisture, freeze it thoroughly, take it out and thaw it, and repeat the freeze-thaw cycle many times.

[0012] Step 7): Transfer the hydrogel fiber obtained in step 6) to a preservation solution for solvent exchange to obtain an MXene organic hydrogel fiber.

[0013] Through a simple one-step solvent replacement, the present invention introduces a large number of positive and negative ions and organic solvents into the hydrogel fiber, causing the water in the hydrogel fiber to precipitate and improving the mechanical properties of the fiber; however, too long a solvent exchange time will increase the crosslinking degree of the hydrogel fiber, resulting in a decrease in the electromagnetic shielding performance instead.

[0014] Step 8): Add a polystyrene-block-polyisoprene copolymer to toluene at an addition amount of 10 - 20 wt%, stir evenly to obtain a polystyrene-block-polyisoprene copolymer / toluene solution.

[0015] Step 9): Remove the moisture on the surface of the MXene organic hydrogel fiber, immerse it in the polystyrene-block-polyisoprene copolymer / toluene solution, and take it out to obtain a core-shell fiber with a polystyrene-block-polyisoprene copolymer coating attached to the surface; after all the solvents in the obtained core-shell fiber are volatilized, an MXene organic hydrogel fiber with a coating and electromagnetic shielding function is obtained.

[0016] In the present invention, by adding Mxene nanosheets into polyvinyl alcohol, since the Mxene nanosheets increase the electron transport and hopping paths, thereby enhancing electron conduction, the Mxene nanosheets attached in the hydrogel network can effectively enhance the overall conductivity, and thus achieve electromagnetic shielding.

[0017] Finally, in the present invention, a highly elastic insulating coating is coated on the surface of the hydrogel fiber by dip coating. This coating can not only prevent the hydrogel fiber from dehydrating, so as to maintain the electromagnetic shielding performance of the hydrogel fiber more durably, but also enhance the stretchability of the hydrogel fiber.

[0018] Preferably, in step 1), the particle size of the Ti 3 AlC 2 powder particles is 300 - 500 mesh, and the concentration of hydrochloric acid is 8 - 10M.

[0019] Preferably, in step 4), the addition amount of hydroxypropyl cellulose is 10 - 20 wt% of the mass of polyvinyl alcohol

[0020] Preferably, in step 4), the addition amount of polyvinyl alcohol is 15 - 25 wt% of the total mass of the system.

[0021] Preferably, in step 4), the addition amount of Mxene nanosheets is 0.1 - 1.5 wt% of the mass of polyvinyl alcohol.

[0022] Preferably, in step 4), the water bath temperature for dispersing hydroxypropyl cellulose is 50 - 70 °C, the water bath temperature for dissolving polyvinyl alcohol is 70 - 90 °C, and the stirring time is 1 - 3 h.

[0023] Preferably, in step 5), the defoaming treatment is vacuum defoaming or static defoaming.

[0024] If it is static defoaming, the static time should not be too long, otherwise hydroxypropyl cellulose and Mxene nanosheets will settle in the polyvinyl alcohol solution, resulting in uneven dispersion and affecting the fiber properties; and the lower the concentration of polyvinyl alcohol in the solution, the faster the sedimentation rate. Preferably, in step 7), the solvent exchange time is 1 - 3 h.

[0025] Preferably, in step 7), the preservation solution is a glycerol - aqueous solution containing 3 - 5M sodium sulfate, and the ratio of water to glycerol is 1:4 - 4:1.

[0026] Preferably, in step 8), the polystyrene content in the polystyrene - block - polyisoprene copolymer is 12 - 16 wt%.

[0027] Compared with the prior art, the present invention has the following technical effects: The hydrogel fibers prepared by the method of the present invention improve the wave absorption ability by adding Mxene nanosheets and hydroxypropyl cellulose to polyvinyl alcohol. Conductive loss can be generated through ion transport in the solvent channels of the fibers and electron transport along the polymer network to attenuate EM energy; meanwhile, water molecules with inherent polarity can generate polarization loss through the rotation of dipoles under an alternating electromagnetic field. Among them, MXene, as a novel two-dimensional material, has high electrical conductivity, high specific surface area and abundant polar functional groups, and is a very promising wave absorber; the addition of hydroxypropyl cellulose will form more pores in the hydrogel, enabling the EM wave to be scattered and reflected multiple times inside the fiber, further enhancing the shielding effect; and high-concentration positive and negative ions and glycerol are introduced into the fiber by the solvent replacement method, making the pores of the gel smaller and tighter, resulting in more incident EM waves being scattered and reflected; the introduced glycerol can also effectively alleviate the problems of easy drying of the hydrogel and easy freezing at low temperatures, improving the water retention and low-temperature performance of the hydrogel. Detailed implementation mode

[0028] The present invention will be further described below in conjunction with embodiments.

[0029] Example 1

[0030] Step 1: Add 0.5 g of LiF to 10 mL of 9 M hydrochloric acid and stir to mix evenly, then add 0.5 g of Ti 3 AlC 2 powder to the solution, and stir the mixed solution at 35 °C for 24 hours for the etching reaction;

[0031] Step 2: After the etching reaction is completed, wash the product with deionized water, and perform ultrasonic treatment on the etched product under an argon gas flow to form a dispersion;

[0032] Step 3: Centrifuge the dispersion and collect the supernatant, and obtain Mxene nanosheets after drying the supernatant;

[0033] Step 4: Take 0.45 g of hydroxypropyl cellulose with Mw = 100000 and add it to water, stir to make it preliminarily dispersed under the condition of heating in a water bath at 50 °C; then take 3 g of polyvinyl alcohol with Mw = 89000 - 98000 and saponification degree > 99% and add it to water, raise the water temperature to 70 °C and continue stirring for 3 h. After the polyvinyl alcohol is completely dissolved, add 0.03 g of Mxene nanosheets to the solution, and cool to room temperature to obtain a spinning solution;

[0034] Step 5: After subjecting the solution obtained in Step 4 to vacuum defoaming treatment, add it to a syringe, connect the syringe to a spinning needle head, and simultaneously inject a saturated sodium sulfate solution containing 3 M sodium hydroxide to form fibers, and let it stand for 30 min to fully crosslink to obtain hydrogel fibers;

[0035] Step 6: After cleaning the residual coagulation bath on the surface of the hydrogel fiber with deionized water, remove the excess water outside the fiber, transfer the hydrogel fiber to a refrigerator for freezing. After completely freezing for 12 h, take it out of the refrigerator and thaw it at room temperature for 3 h. Repeat the freeze-thaw cycle three times;

[0036] Step 7: Transfer the hydrogel fiber after repeating the freeze-thaw cycle three times to a glycerol-water (1:1) solution containing 5 M sodium sulfate for solvent exchange for 2 h to obtain MXene organic hydrogel fiber;

[0037] Step 8: Add 1.5 g of polystyrene-block-polyisoprene copolymer (polystyrene content is 12 - 16 wt%) to 8.5 g of toluene, and stir for 30 minutes to mix evenly.

[0038] Step 9: Place the MXene organic hydrogel fiber after solvent exchange on absorbent paper to remove the water on its surface, and then immerse the hydrogel fiber in the polystyrene-block-polyisoprene copolymer / toluene solution to attach a thin layer of polystyrene-block-polyisoprene copolymer coating on its surface.

[0039] Step 10: Hang the hydrogel fiber adhered with the polystyrene-block-polyisoprene copolymer coating in the air for 30 minutes until all the solvent toluene has evaporated, and finally obtain the MXene organic hydrogel fiber with a coating.

[0040] Perform various tests on the obtained hydrogel fiber. It is measured that the hydrogel fiber with a diameter of 1.0 mm has a maximum tensile strength of 2.09 MPa and a fracture strain of 410% at a tensile rate of 40 mm / min; the conductivity is 1.09 S / m; after weaving the fiber into a rectangle of 22.86×10.16×1.0 mm 3 the total shielding efficiency is measured to be 35 dB in the frequency range of 8.2 - 12.4 GHz; it is frozen at -20 °C for 3 h, does not freeze, and still remains soft; when stored at room temperature, the mass loss rate is 17% after 7 d.

[0041] Comparative Example 1

[0042] Step 1: Add 0.5 g of LiF to 10 mL of 9 M hydrochloric acid and stir to mix evenly, and then add 0.5 g of Ti 3 AlC 2 powder to the solution, and stir the mixed solution at 35 °C for 24 hours for the etching reaction;

[0043] Step 2: After the etching reaction is completed, wash the product with deionized water and perform ultrasonic treatment on the etched product under an argon gas stream to form a dispersion;

[0044] Step 3: Centrifuge the dispersion liquid and collect the supernatant. After drying the supernatant, Mxene nanosheets are obtained.

[0045] Step 4: Take 0.45 g of hydroxypropyl cellulose with Mw = 100000 and add it to water. Stir it under a water bath heating condition at 50 °C to make it preliminarily dispersed. Then take 3 g of polyvinyl alcohol with Mw = 89000 - 98000 and a saponification degree > 99% and add it to water. Raise the water temperature to 70 °C and continue stirring for 3 h. After the polyvinyl alcohol is completely dissolved, add 0.015 g of Mxene nanosheets to the solution, and cool it to room temperature to obtain a spinning solution.

[0046] Step 5: After subjecting the solution obtained in Step 4 to vacuum defoaming treatment, add it to a syringe. Connect the syringe to a spinning needle head, and simultaneously inject a saturated sodium sulfate solution containing 3 M sodium hydroxide to form fibers. Let it stand for 30 min to fully crosslink and obtain hydrogel fibers.

[0047] Step 6: After cleaning the residual coagulation bath on the surface of the hydrogel fibers with deionized water, remove the excess moisture outside the fibers. Transfer the hydrogel fibers to a refrigerator for freezing. After thoroughly freezing for 12 h, take them out of the refrigerator and thaw them at room temperature for 3 h. Repeat the freeze-thaw cycle three times.

[0048] Step 7: Transfer the hydrogel fibers after repeating the freeze-thaw cycle three times to a glycerol-water (1:1) solution containing 5 M sodium sulfate for solvent exchange for 2 h to obtain MXene organic hydrogel fibers.

[0049] Step 8: Take 1.5 g of polystyrene-block-polyisoprene copolymer (polystyrene content is 12 - 16 wt%) and add it to 8.5 g of toluene. Stir for 30 minutes to make it evenly mixed.

[0050] Step 9: Place the MXene organic hydrogel fibers after solvent exchange on absorbent paper to remove the moisture on their surfaces, and then immerse the hydrogel fibers in the polystyrene-block-polyisoprene copolymer / toluene solution to attach a thin layer of polystyrene-block-polyisoprene copolymer coating on their surfaces.

[0051] Step 10: Hang the hydrogel fibers adhered with the polystyrene-block-polyisoprene copolymer coating in the air for 30 minutes until all the solvent toluene has volatilized, and finally obtain the coated MXene organic hydrogel fibers.

[0052] Perform various tests on the obtained hydrogel fibers. It is measured that the hydrogel fibers with a diameter of 1.0 mm have a maximum tensile strength of 2.03 MPa and a fracture strain of 400% at a tensile rate of 40 mm / min; the conductivity is 0.89 S / m; the fibers are woven into a 22.86×10.16×1.0 mm 3After forming a rectangle, the total shielding efficiency was measured to be 25 dB in the frequency range of 8.2 - 12.4 GHz; it was frozen at -20 °C for 3 h, did not freeze, and remained soft; when stored at room temperature, the mass loss rate was 18% after 7 d.

[0053] Comparative Example 2

[0054] Step 1: Add 0.5 g of LiF to 10 mL of 9 M hydrochloric acid, stir and mix evenly, and then add 0.5 g of Ti 3 AlC 2 powder to the solution, and stir the mixed solution at 35 °C for 24 hours for an etching reaction;

[0055] Step 2: After the etching reaction is completed, wash the product with deionized water, and perform ultrasonic treatment on the etched product under an argon gas stream to form a dispersion;

[0056] Step 3: Centrifuge the dispersion and collect the supernatant, and obtain Mxene nanosheets after drying the supernatant;

[0057] Step 4: Take 0.45 g of hydroxypropyl cellulose with Mw = 100000 and add it to water, stir to make it preliminarily dispersed under the condition of heating in a water bath at 50 °C; then take 3 g of polyvinyl alcohol with Mw = 89000 - 98000 and a degree of alcoholysis > 99% and add it to water, raise the water temperature to 70 °C and continue to stir for 3 h. After the polyvinyl alcohol is completely dissolved, add 0.06 g of Mxene nanosheets to the solution, and cool to room temperature to obtain a spinning solution;

[0058] Step 5: After subjecting the solution obtained in Step 4 to vacuum defoaming treatment, add it to a syringe, connect the syringe to a spinning needle head, and simultaneously inject a saturated sodium sulfate solution containing 3 M sodium hydroxide to form fibers, and let it stand for 30 min to fully crosslink to obtain hydrogel fibers;

[0059] Step 6: After washing the surface of the hydrogel fibers with deionized water to remove the residual coagulation bath, remove the excess water outside the fibers, transfer the hydrogel fibers to a refrigerator for freezing, take them out of the refrigerator after completely freezing for 12 h, and thaw at room temperature for 3 h, repeating the freeze-thaw cycle three times;

[0060] Step 7: Transfer the hydrogel fibers after repeating the freeze-thaw cycle three times to a glycerol-water (1:1) solution containing 5 M sodium sulfate for solvent exchange for 2 h to obtain MXene organic hydrogel fibers;

[0061] Step 8: Take 1.5 g of polystyrene-block-polyisoprene copolymer (polystyrene content is 12 - 16 wt%) and add it to 8.5 g of toluene, and stir for 30 minutes to mix evenly.

[0062] Step 9: Place the MXene organic hydrogel fiber after solvent exchange on absorbent paper to remove the moisture on its surface, and then immerse the hydrogel fiber in a polystyrene-block-polyisoprene copolymer / toluene solution to attach a thin layer of polystyrene-block-polyisoprene copolymer coating on its surface.

[0063] Step 10: Hang the hydrogel fiber adhered with the polystyrene-block-polyisoprene copolymer coating in the air for 30 minutes until all the solvent toluene has evaporated, and finally obtain the MXene organic hydrogel fiber with the coating.

[0064] Perform various tests on the obtained hydrogel fiber. It is measured that the hydrogel fiber with a diameter of 1.0 mm has a maximum tensile strength of 2.12 MPa and a fracture strain of 415% at a tensile rate of 40 mm / min; the conductivity is 0.92 S / m; after weaving the fiber into a rectangle of 22.86×10.16×1.0 mm 3 the total shielding efficiency is measured to be 27 dB in the frequency range of 8.2 - 12.4 GHz; it is frozen at -20 °C for 3 h, does not freeze, and remains soft; when stored at room temperature, the mass loss rate is 17% after 7 d.

[0065] Comparative Example 3

[0066] Step 1: Add 0.5 g of LiF to 10 mL of 9 M hydrochloric acid, stir and mix evenly, and then add 0.5 g of Ti 3 AlC 2 powder to the solution, and stir the mixed solution at 35 °C for 24 hours for the etching reaction;

[0067] Step 2: After the etching reaction is completed, wash the product with deionized water, and perform ultrasonic treatment on the etched product under an argon gas flow to form a dispersion;

[0068] Step 3: Centrifuge the dispersion and collect the supernatant, and dry the supernatant to obtain Mxene nanosheets;

[0069] Step 4: Take 0.45 g of hydroxypropyl cellulose with Mw = 100000 and add it to water, stir to make it preliminarily dispersed under the condition of heating in a water bath at 50 °C; then take 3 g of polyvinyl alcohol with Mw = 89000 - 98000 and a saponification degree > 99% and add it to water, raise the water temperature to 70 °C and continue to stir for 3 h. After the polyvinyl alcohol is completely dissolved, add 0.03 g of Mxene nanosheets to the solution, and cool to room temperature to obtain a spinning solution;

[0070] Step 5: After subjecting the solution obtained in Step 4 to vacuum defoaming treatment, add it to a syringe. Connect the syringe to a spinning needle head and simultaneously inject a saturated sodium sulfate solution containing 3M sodium hydroxide to form fibers. Let it stand for 30 min to fully crosslink and obtain hydrogel fibers;

[0071] Step 6: After washing the residual coagulation bath on the surface of the hydrogel fibers with deionized water, remove the excess moisture outside the fibers. Transfer the hydrogel fibers to a refrigerator for freezing. After completely freezing for 12 h, take them out of the refrigerator and thaw at room temperature for 3 h. Repeat the freeze-thaw cycle three times;

[0072] Step 7: Transfer the hydrogel fibers after repeating the freeze-thaw cycle three times to an aqueous solution containing 5M sodium sulfate for solvent exchange for 2 h to obtain MXene organic hydrogel fibers;

[0073] Step 8: Take 1.5 g of polystyrene-block-polyisoprene copolymer (polystyrene content is 12 - 16 wt%) and add it to 8.5 g of toluene. Stir for 30 minutes to mix evenly.

[0074] Step 9: Place the MXene organic hydrogel fibers after solvent exchange on absorbent paper to remove the moisture on their surfaces. Then immerse the hydrogel fibers in the polystyrene-block-polyisoprene copolymer / toluene solution to attach a thin layer of polystyrene-block-polyisoprene copolymer coating on their surfaces.

[0075] Step 10: Hang the hydrogel fibers adhered with the polystyrene-block-polyisoprene copolymer coating in the air for 30 minutes until all the solvent toluene has volatilized, and finally obtain the coated MXene organic hydrogel fibers.

[0076] Perform various tests on the obtained hydrogel fibers. It is measured that the maximum tensile strength of the hydrogel fibers with a diameter of 1.0 mm is 1.82 MPa at a tensile rate of 40 mm / min, and the fracture strain is 370%; the conductivity is 1.37 S / m; after weaving the fibers into a rectangle of 22.86×10.16×1.0 mm 3 the total shielding efficiency is measured to be 38 dB in the frequency range of 8.2 - 12.4 GHz; freeze at -20 °C for 3 h and ice; store at room temperature, and the mass loss rate after 7 d is 34%.

[0077] Comparative Example 4

[0078] Step 1: Add 0.5 g of LiF to 10 mL of 9M hydrochloric acid and stir to mix evenly. Then add 0.5 g of Ti 3 AlC 2 powder to the solution, and stir the mixed solution at 35 °C for 24 hours for etching reaction;

[0079] Step 2: After the etching reaction is completed, wash the product with deionized water and perform ultrasonic treatment on the etched product under an argon gas flow to form a dispersion;

[0080] Step 3: Centrifuge the dispersion and collect the supernatant. After drying the supernatant, Mxene nanosheets are obtained;

[0081] Step 4: Take 0.45 g of hydroxypropyl cellulose with Mw = 100000 and add it to water. Stir it under a water bath heating condition at 50 °C to make it preliminarily dispersed; then take 3 g of polyvinyl alcohol with Mw = 89000 - 98000 and a saponification degree > 99% and add it to water. Raise the water temperature to 70 °C and continue stirring for 3 h. After the polyvinyl alcohol is completely dissolved, add 0.03 g of Mxene nanosheets to the solution and cool it to room temperature to obtain a spinning solution;

[0082] Step 5: After subjecting the solution obtained in Step 4 to vacuum defoaming treatment, add it to a syringe. Connect the syringe to a spinning needle head and simultaneously inject a saturated sodium sulfate solution containing 3 M sodium hydroxide to form fibers. Let it stand for 30 min to fully crosslink and obtain hydrogel fibers;

[0083] Step 6: After washing the residual coagulation bath on the surface of the hydrogel fibers with deionized water, remove the excess moisture outside the fibers. Transfer the hydrogel fibers to a refrigerator for freezing. After thoroughly freezing for 12 h, take them out of the refrigerator and thaw at room temperature for 3 h. Repeat the freeze-thaw cycle three times;

[0084] Step 7: Transfer the hydrogel fibers after repeating the freeze-thaw cycle three times to a glycerol-water (4:1) solution containing 5 M sodium sulfate for solvent exchange for 2 h to obtain MXene organic hydrogel fibers;

[0085] Step 8: Take 1.5 g of polystyrene-block-polyisoprene copolymer (polystyrene content is 12 - 16 wt%) and add it to 8.5 g of toluene. Stir for 30 minutes to make it evenly mixed.

[0086] Step 9: Place the MXene organic hydrogel fibers after solvent exchange on absorbent paper to remove the moisture on their surface, and then immerse the hydrogel fibers in the polystyrene-block-polyisoprene copolymer / toluene solution to attach a thin layer of polystyrene-block-polyisoprene copolymer coating on its surface.

[0087] Step 10: Hang the hydrogel fibers adhered with the polystyrene-block-polyisoprene copolymer coating in the air for 30 minutes until all the solvent toluene has volatilized, and finally obtain the coated MXene organic hydrogel fibers.

[0088] The obtained hydrogel fibers were subjected to various tests. The hydrogel fibers with a diameter of 1.0 mm had a maximum tensile strength of 2.23 MPa and a failure strain of 450% at a tensile rate of 40 mm / min; the conductivity was 0.41 S / m; after the fibers were woven into a rectangle of 22.86×10.16×1.0 mm 3 the total shielding efficiency was measured to be 17 dB in the frequency range of 8.2 - 12.4 GHz; after being frozen at -20 °C for 3 h, it did not freeze and remained soft; when stored at room temperature, the mass loss rate was 13% after 7 d.

[0089] Comparative Example 5

[0090] Step 1: Add 0.5 g of LiF to 10 mL of 9 M hydrochloric acid and stir to mix evenly, then add 0.5 g of Ti 3 AlC 2 powder to the solution, and stir the mixed solution at 35 °C for 24 hours for an etching reaction;

[0091] Step 2: After the etching reaction is completed, wash the product with deionized water and perform ultrasonic treatment on the etched product under an argon gas stream to form a dispersion;

[0092] Step 3: Centrifuge the dispersion and collect the supernatant, and obtain Mxene nanosheets after drying the supernatant;

[0093] Step 4: Take 3 g of polyvinyl alcohol with Mw = 89000 - 98000 and an alcoholysis rate > 99% and add it to water, raise the water temperature to 70 °C and continue to stir for 3 h. After the polyvinyl alcohol is completely dissolved, add 0.03 g of Mxene nanosheets to the solution and cool to room temperature to obtain a spinning solution;

[0094] Step 5: After subjecting the solution obtained in Step 4 to vacuum defoaming treatment, add it to a syringe, connect the syringe to a spinning needle, and simultaneously inject a saturated sodium sulfate solution containing 3 M sodium hydroxide to form fibers. Let it stand for 30 min to fully crosslink to obtain hydrogel fibers;

[0095] Step 6: Wash the residual coagulation bath on the surface of the hydrogel fibers with deionized water, remove the excess water outside the fibers, transfer the hydrogel fibers to a refrigerator for freezing, take them out of the refrigerator after thorough freezing for 12 h, and thaw at room temperature for 3 h. Repeat the freeze-thaw cycle three times;

[0096] Step 7: Transfer the hydrogel fibers after repeating the freeze-thaw cycle three times to a glycerol-water (1:1) solution containing 5 M sodium sulfate for solvent exchange for 2 h to obtain MXene organic hydrogel fibers;

[0097] Step 8: Take 1.5 g of polystyrene-block-polyisoprene copolymer (polystyrene content is 12 - 16 wt%) and add it to 8.5 g of toluene, and stir for 30 minutes to make it evenly mixed.

[0098] Step 9: Place the MXene organic hydrogel fiber after solvent exchange on absorbent paper to remove the moisture on its surface, and then immerse the hydrogel fiber into the polystyrene-block-polyisoprene copolymer / toluene solution to attach a thin layer of polystyrene-block-polyisoprene copolymer coating on its surface.

[0099] Step 10: Hang the hydrogel fiber adhered with the polystyrene-block-polyisoprene copolymer coating in the air for 30 minutes, wait for all the solvent toluene to volatilize, and finally obtain the MXene organic hydrogel fiber with a coating.

[0100] Perform various tests on the obtained hydrogel fiber. It is measured that the maximum tensile strength of the hydrogel fiber with a diameter of 1.0 mm is 2.15 MPa at a tensile rate of 40 mm / min, and the fracture strain is 420%; the conductivity is 0.77 S / m; after weaving the fiber into a rectangle with dimensions of 22.86×10.16×1.0 mm 3 the total shielding efficiency is measured to be 21 dB in the frequency range of 8.2 - 12.4 GHz; it is frozen at -20 °C for 3 h, does not freeze, and still remains soft; when stored at room temperature, the mass loss rate after 7 d is 16%.

[0101] Comparative Example 6

[0102] Step 1: Add 0.5 g of LiF to 10 mL of 9M hydrochloric acid and stir to mix evenly, and then add 0.5 g of Ti 3 AlC 2 powder to the solution, and stir the mixed solution at 35 °C for 24 hours for the etching reaction;

[0103] Step 2: After the etching reaction ends, wash the product with deionized water, and perform ultrasonic treatment on the etched product under an argon gas flow to form a dispersion;

[0104] Step 3: Centrifuge the dispersion and collect the supernatant, and dry the supernatant to obtain Mxene nanosheets;

[0105] Step 4: Take 0.45 g of hydroxypropyl cellulose with Mw = 100000 and add it to water, and stir to make it preliminarily dispersed under the condition of heating in a 50 °C water bath; then take 3 g of polyvinyl alcohol with Mw = 89000 - 98000 and saponification degree > 99% and add it to water, raise the water temperature to 70 °C and continue to stir for 3 h. After the polyvinyl alcohol is completely dissolved, add 0.03 g of Mxene nanosheets to the solution, and cool to room temperature to obtain a spinning solution;

[0106] Step Five: After subjecting the solution obtained in Step Four to vacuum defoaming treatment, add it to a syringe. Connect the syringe to a spinning needle head and simultaneously inject a saturated sodium sulfate solution containing 3M sodium hydroxide to form fibers. Let it stand for 30 min to fully crosslink and obtain hydrogel fibers;

[0107] Step Six: After cleaning the residual coagulation bath on the surface of the hydrogel fibers with deionized water, remove the excess moisture outside the fibers. Transfer the hydrogel fibers to a refrigerator for freezing. After thoroughly freezing for 12 h, take them out of the refrigerator and thaw at room temperature for 3 h. Repeat the freeze-thaw cycle three times;

[0108] Step Seven: Transfer the hydrogel fibers after repeating the freeze-thaw cycle three times to a glycerol-water (1:1) solution containing 5M sodium sulfate for solvent exchange for 2 h to obtain MXene organic hydrogel fibers;

[0109] Perform various tests on the obtained hydrogel fibers. It is measured that the maximum tensile strength of the hydrogel fibers with a diameter of 1.0 mm is 1.98 MPa and the breaking strain is 380% at a tensile rate of 40 mm / min; the conductivity is 1.10 S / m; the fibers are woven into a rectangle of 22.86×10.16×1.0 mm 3 and the total shielding efficiency is measured to be 35 dB in the frequency range of 8.2–12.4 GHz; freeze at -20 °C for 3 h, no ice formation, still remain soft; store at room temperature, and the mass loss rate is 53% after 7 d.

[0110] Performance Test

[0111] The test data of the organic hydrogel fibers obtained in Example 1 and Comparative Examples 1-6 are as follows:

[0112]

[0113] It can be found from Example 1 and Comparative Examples 1 and 2 that due to the change in the addition ratio of Mxene nanosheets, both lead to a decrease in the electrical conductivity and shielding efficiency of the hydrogel fibers. This is because the increase in MXene content improves the electron transport and hopping paths and enhances the electron conduction; however, the ion channel size also decreases accordingly, resulting in a decrease in ion conduction. Therefore, there is an optimal range for the addition amount of MXene. At the same time, with the increase in the addition ratio of Mxene nanosheets, the mechanical properties are slightly improved because Mxene provides more crosslinking sites and increases the crosslinking density.

[0114] It can be found from Example 1 and Comparative Examples 3 and 4 that adding glycerol to the preservation solution will slightly reduce the electrical conductivity and shielding efficiency of the fibers, but it provides freeze resistance and improves the mechanical properties and environmental tolerance. This is because polar water molecules can generate polarization loss. As water molecules are replaced by glycerol molecules, both conduction loss and polarization loss are weakened, resulting in a decrease in shielding efficiency. At the same time, the addition of glycerol reduces the vapor pressure of water, reduces the volatilization of water, and lowers the freezing point of the mixed solution, improving the environmental tolerance of the fibers. Glycerol molecules can also crosslink with polyvinyl alcohol to make the structure denser and enhance the mechanical strength.

[0115] Compared with Example 1, the mechanical properties of Comparative Example 5 are improved, but the electrical conductivity and shielding efficiency decrease. This is because the addition of hydroxypropyl cellulose will form more holes in the hydrogel, causing the EM wave to scatter and reflect multiple times inside the fiber, reducing the resistance of ion transfer and increasing ion conduction. However, the holes are defects in the fiber structure, which will lead to uneven distribution of the mechanical properties of the fiber and cause stress concentration, reducing the fiber strength.

[0116] Compared with Example 1, Comparative Example 6 has a poorer effect in water retention, and at the same time, the mechanical properties decrease slightly. The reason is that in the scheme of Comparative Example 2, the polystyrene-block-polyisoprene copolymer coating is not added, resulting in water molecules being easily volatilized into the air through the cortex. The polystyrene-block-polyisoprene copolymer coating is denser than the cortex, and water molecules are difficult to pass through. At the same time, this coating has good elasticity and can also improve the mechanical properties of the hydrogel fiber to a certain extent.

[0117] The raw materials and equipment used in the present invention are all common raw materials and equipment in the art without special instructions; the methods used in the present invention are all conventional methods in the art without special instructions.

[0118] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. Preparation method of MXene organic hydrogel fiber with electromagnetic shielding function, characterized in that it includes the following steps: Step 1): Add 0.4 - 0.6 g of LiF to 10 mL of hydrochloric acid, stir and mix evenly, and then add 0.4 - 0.6 g of Ti 3 AlC 2 powder to the solution, and carry out an etching reaction by stirring the mixed solution at 30 - 40 °C for 20 - 30 hours; Step 2): After the etching reaction ends, wash the product with deionized water, and perform ultrasonic treatment on the etched product under an argon gas stream to form a dispersion; Step 3): Centrifuge the dispersion and collect the supernatant. After drying the supernatant, obtain Mxene nanosheets; Step 4): Add hydroxypropyl cellulose to water and heat to disperse; Add polyvinyl alcohol, raise the temperature and stir until the polyvinyl alcohol is completely dissolved, add Mxene nanosheets, and cool to room temperature to obtain a spinning solution; Step 5): Defoam the spinning solution and inject it into a coagulation bath to form fibers, and let it stand for crosslinking to obtain hydrogel fibers; Step 6): Clean the surface of the hydrogel fiber, remove excess moisture, freeze it thoroughly, take it out and thaw it, and repeat the freeze-thaw cycle multiple times; Step 7): Transfer the hydrogel fiber obtained in Step 6) to a preservation solution for solvent exchange for 1 - 3 h to obtain MXene organic hydrogel fiber; the preservation solution is a glycerol - aqueous solution containing 3 - 5 M sodium sulfate, where the ratio of water to glycerol is 1:4 - 4:1; Step 8): Add polystyrene - block - polyisoprene copolymer to toluene at an addition amount of 10 - 20 wt%, and stir evenly to obtain a polystyrene - block - polyisoprene copolymer / toluene solution; Step 9): Remove the moisture on the surface of the MXene organic hydrogel fiber, immerse it in the polystyrene - block - polyisoprene copolymer / toluene solution, and take it out to obtain a core - shell fiber with a polystyrene - block - polyisoprene copolymer coating attached to the surface; After all the excess solvent has evaporated, obtain a coated MXene organic hydrogel fiber with electromagnetic shielding function.

2. The preparation method according to claim 1, characterized in that: In step 1), the Ti 3 AlC 2 powder particle size is 300 - 500 mesh, and the hydrochloric acid concentration is 8 - 10 M.

3. The preparation method according to claim 1, characterized in that: In Step 4), the addition amount of the hydroxypropyl cellulose is 10 - 20 wt% of the mass of the polyvinyl alcohol.

4. The preparation method according to claim 3, characterized in that: In Step 4), the addition amount of the polyvinyl alcohol is 15 - 25 wt% of the total mass of the system.

5. The preparation method according to claim 4, characterized in that: In Step 4), the addition amount of the Mxene nanosheets is 0.1 - 1.5 wt% of the mass of the polyvinyl alcohol.

6. The preparation method according to claim 1, characterized in that: In Step 4), the water bath temperature for dispersing the hydroxypropyl cellulose is 50 - 70 °C, the water bath temperature for dissolving the polyvinyl alcohol is 70 - 90 °C, and the stirring time is 1 - 3 h.

7. The preparation method according to claim 1, characterized in that: In Step 8), the polystyrene content in the polystyrene - block - polyisoprene copolymer is 12 - 16 wt%.

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