A method for preparing a polyvinyl alcohol-based electromagnetic shielding conductive hydrogel

Abstract

The application discloses a preparation method of polyvinyl alcohol-based electromagnetic shielding conductive hydrogel, which comprises the following steps: (1) preparing a high-concentration dimethyl sulfoxide aqueous solution; adding polyvinyl alcohol into the dimethyl sulfoxide aqueous solution, and heating and stirring to completely dissolve the polyvinyl alcohol, so as to obtain a mixed solution; (2) placing the mixed solution after standing in a mold, and freezing at low temperature to obtain a PVA gel; (3) preparing an electrolyte salt solution, wherein the electrolyte salt solution contains low-concentration dimethyl sulfoxide; and placing the PVA gel in the electrolyte salt solution, so as to obtain the polyvinyl alcohol-based electromagnetic shielding conductive hydrogel after ion exchange. The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared by the method has high transparency, strength and ionic conductivity, the light transmittance is up to 75.2%, the compression resistance at a strain of 80% is up to 2.97 MPa, the ionic conductivity is up to 10.34 mS / cm, and the effective electromagnetic shielding performance (>30 dB) can be maintained for more than 60 hours at a low temperature of-60 DEG C.

Description

Technical Field

[0001] This invention relates to a method for preparing a polyvinyl alcohol-based electromagnetic shielding conductive hydrogel. Background Technology

[0002] With the advent of the 5G information age, various portable communication devices are increasingly used in daily life. Electronic components and complex circuits controlled by wireless networks inevitably generate significant amounts of electromagnetic radiation and interference, seriously affecting the normal operation of sensitive electronic equipment systems and human health. Considering the rapid development of deformable and wearable electronic devices, there is an urgent need for highly efficient electromagnetic interference shielding materials with high transparency, good mechanical properties, and low-temperature stability.

[0003] Hydrogels possess excellent conductivity, flexibility, compressibility, and biocompatibility, giving them unique advantages and potential in the development of deformable and wearable electromagnetic shielding materials. They have gradually become an important research target for both academia and industry. For example, the team of Associate Professor Liu Xiaofang and Professor Yu Ronghai at Beijing University of Aeronautics and Astronautics prepared an MXene organic hydrogel with MXene as the conductive network and water / glycerol binary solvent as the ion transport channel. This hydrogel exhibits excellent electromagnetic shielding performance; when the MXene content is 1.1 wt%, the highest electromagnetic shielding efficiency is 33.6 dB (Yu,YH;Yi,P.;Xu,WB;Sun,X.;Deng,G.;Liu,XF;Shui,JL;Yu,RH). Environmentally tough and stretchable MXene organohydrogel with exceptionally enhanced electromagnetic interference shielding performances, Nano-Micro Lett. 14(2022)77). Southeast University researchers, including He et al., prepared aero / organo / hydrogels with gravity-induced asymmetric gradient structures, achieving a total electromagnetic shielding efficiency of 86.9 dB (He, M.; Lv, XL; Li, ZH; Li, HY; Qian, W.; Zhu, SY; Zhou, YM; Wang, YJ; Bu, XH, Research on efficient electromagnetic shielding performance and modulation mechanism of aero / organo / hydrogels with gravity-induced asymmetric gradient structure, Small 20(2024)2403210). While these hydrogel materials demonstrate significant effectiveness in electromagnetic shielding, with the development of flexible electronics, communication technology, and polar exploration technology, hydrogel materials, as core protective materials for high-end equipment, need to be applied in multifunctional scenarios that balance environmental adaptability (low temperature) and intelligent interaction (transparent visualization). For the aforementioned hydrogel materials, they are highly susceptible to low-temperature brittleness, making it difficult to maintain transparency for screen display functionality, and also difficult to maintain electromagnetic shielding performance in environments below -5°C. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for preparing polyvinyl alcohol-based electromagnetic shielding conductive hydrogel. The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared by this method has high transparency, strength and ionic conductivity, and still has good electromagnetic shielding performance at extremely low temperatures (-60℃).

[0005] Technical solution: The preparation method of the polyvinyl alcohol-based electromagnetic shielding conductive hydrogel of the present invention includes the following steps:

[0006] (1) Prepare a high concentration of dimethyl sulfoxide (DMSO) aqueous solution; add polyvinyl alcohol (PVA) to the dimethyl sulfoxide aqueous solution, heat and stir to completely dissolve PVA to obtain a mixed solution; let the obtained mixed solution stand for a period of time to remove air bubbles in the solution;

[0007] (2) Place the settled mixture in a mold and freeze it at low temperature to obtain PVA gel;

[0008] (3) Prepare an electrolyte salt solution containing DMSO, wherein the electrolyte salt solution contains a low concentration of dimethyl sulfoxide; place the PVA gel in the electrolyte salt solution and obtain a polyvinyl alcohol-based electromagnetic shielding conductive hydrogel after ion exchange.

[0009] In step (1), the volume fraction of dimethyl sulfoxide in the aqueous solution is 55-60%.

[0010] In step (1), the mass-to-volume ratio of polyvinyl alcohol to dimethyl sulfoxide is 1.5 g: 9-12 mL.

[0011] In step (1), the heating temperature is 90-95℃, the heating and stirring time is 50-60 min, and the standing time is 10-15 min.

[0012] In step (2), the freezing temperature is -20 to -25°C and the freezing time is 10 to 12 hours.

[0013] In step (3), the electrolyte salt in the electrolyte salt solution is one of NaCl, KCl or MgCl2; the mass concentration of the electrolyte salt is 3.15 to 3.2 mg / mL.

[0014] In step (3), the volume fraction of dimethyl sulfoxide in the electrolyte salt solution is 30-35%.

[0015] In step (3), the ion exchange time is 12 to 14 hours.

[0016] The formation of hydrogen bonds in the electromagnetic shielding conductive hydrogel prepared by this invention (based on the interaction between hydrogen atoms in the polyvinyl alcohol molecular chain and oxygen atoms in the dimethyl sulfoxide molecule to form hydrogen bonds) can help regulate the interaction between PVA molecules, reduce light scattering, and thus increase the transparency of the hydrogel. The formation of hydrogen bonds also contributes to the good mechanical properties of the hydrogel. PVA-based hydrogels themselves have a certain ion conductivity. By adding an electrolyte salt solution, cations and anions in the solution can move freely in the hydrogel, thereby forming conductive paths in the hydrogel and significantly enhancing its ion conductivity, which helps to achieve electromagnetic shielding function. At the same time, this method not only improves the conductivity of the hydrogel, but also maintains its good mechanical properties (the preparation method of this invention can achieve a dual improvement in the conductivity and mechanical properties of the hydrogel. On the one hand, by introducing an electrolyte salt solution, cations and anions can move freely in the hydrogel, forming conductive paths, thereby significantly enhancing its ion conductivity; this improvement in conductivity provides the possibility for the application of hydrogels in the field of electromagnetic shielding; on the other hand, this invention promotes the hydroxyl groups in the polyvinyl alcohol molecular chain...) Hydrogen bonds are formed between DMSO and oxygen atoms in dimethyl sulfoxide (DMSO) molecules, effectively regulating the interactions between PVA molecules. This hydrogen bonding not only reduces light scattering and improves the transparency of the hydrogel, but also enhances the internal network structure, giving it good mechanical properties. Thus, while enhancing conductivity, the hydrogel maintains its structural stability and toughness, making it less prone to cracking or deformation. Adding DMSO during the formation of PVA-based hydrogels effectively improves their antifreeze properties. This is because DMSO forms hydrogen bonds with water molecules (these hydrogen bonds are formed between dimethyl sulfoxide (DMSO) and water molecules, and their formation is crucial for improving the antifreeze properties of the hydrogel; DMSO molecules can tightly bind with water molecules through hydrogen bonds, thereby reducing the degree of freedom of water molecules in the hydrogel and reducing ice crystal formation. This effect allows the hydrogel to maintain good flexibility and elasticity at low temperatures, avoiding structural damage and performance degradation caused by freezing). This hydrogen bonding effect lowers the freezing point and evaporation point of water, allowing the PVA-based hydrogel to maintain its good electromagnetic shielding properties at low temperatures.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared by the method of the present invention has high transparency, strength and ionic conductivity, with a light transmittance of up to 75.2% and a compressive strength of up to 2.97 MPa at 80% strain; the ionic conductivity can reach 10.34 mS / cm; and it can still maintain effective electromagnetic shielding performance (>30 dB) at a low temperature of -60℃ for more than 60 hours. Attached Figure Description

[0018] Figure 1A digital photograph of the conductive hydrogel S prepared in Example 1;

[0019] Figure 2 The FTIR curve of the conductive hydrogel S prepared in Example 1 is shown.

[0020] Figure 3 The transmittance of the conductive hydrogel S prepared in Example 1 in the visible light wavelength range;

[0021] Figure 4 The image shows the compressive stress-strain curve of the conductive hydrogel S prepared in Example 1.

[0022] Figure 5 The electromagnetic shielding effectiveness diagrams of the conductive hydrogel S prepared in Example 1 and its S-LD30 after freezing for 30 h and S-LD60 after freezing for 60 h are shown. Detailed Implementation

[0023] Example 1

[0024] The present invention discloses a method for preparing a polyvinyl alcohol-based electromagnetic shielding conductive hydrogel, comprising the following steps:

[0025] (1) Mix 12 mL of DMSO with 8 mL of deionized water at 700 r / min for 10 min to obtain an aqueous solution of DMSO;

[0026] (2) Add 1.5g PVA to the DMSO aqueous solution in step (1), heat and stir at 90℃ for 50min, and then let stand for 10min to obtain a mixed solution in which PVA is completely dissolved and there are no excess bubbles.

[0027] (3) Place the mixed solution from step (2) into a custom-shaped polytetrafluoroethylene mold, and then place the polytetrafluoroethylene mold containing the mixed solution in the freezer compartment of a refrigerator and freeze for 10 hours to gel; obtain the gel product.

[0028] (4) Mix 2.8g NaCl and 50mL deionized water and stir for 10min to obtain solution A; then mix 30mL DMSO and 8mL deionized water and stir for 10min to obtain solution B; then mix solution A and solution B and stir for 10min to prepare an electrolyte salt solution.

[0029] (5) The gel product from step (3) is placed in the electrolyte salt solution from step (4) for 12 hours. After reaching ion exchange equilibrium, polyvinyl alcohol-based electromagnetic shielding conductive hydrogel is obtained, denoted as S.

[0030] Figure 1 A digital photograph of the conductive hydrogel S prepared in Example 1, from... Figure 1It can be seen that product S obtained by gel treatment and ion exchange has a complete hydrogel structure, indicating that PVA is completely dissolved. The appearance of the product can be customized and controlled by a custom mold. It can be observed that the blue glove can be seen through product S, indicating that product S has a certain degree of transparency. In addition, product S hardly deforms when squeezed by hand, indicating that product S exhibits good mechanical compression resistance.

[0031] Figure 2 The image shows the FTIR curve of the conductive hydrogel S prepared in Example 1. Figure 2 It can be seen that a wavenumber of 3264 cm⁻¹ can be observed within the infrared wavenumber range. -1 3306cm -1 The absorption peaks at the two locations are the -OH stretching vibration peaks between hydrogen atoms in the polyvinyl alcohol molecular chain and oxygen atoms in the dimethyl sulfoxide molecule, and the -OH stretching vibration peaks formed between dimethyl sulfoxide and water molecules, which proves that there are two types of hydrogen bonds in the prepared material.

[0032] Figure 3 This is a transmittance diagram of product S obtained in Example 1 within the visible light wavelength range. Figure 3 It can be seen that in the visible light wavelength range, from 400nm to 780nm, the transmittance of product S increases with increasing wavelength, and the maximum transmittance of 75.2% is obtained at 780nm, proving that the prepared material is an optically transparent hydrogel material.

[0033] Figure 4 The image shows the compressive stress-strain curve of product S obtained in Example 1. Figure 4 It can be seen that the product S obtained in Example 1 has a compressive strength of up to 2.97 MPa at a compressive strain of 80%, indicating that the formation of hydrogen bonds and subsequent ion exchange in the polyvinyl alcohol-based electromagnetic shielding conductive hydrogel of the present invention enables it to maintain good mechanical properties and is more suitable for harsh environments.

[0034] After being frozen at -60°C for 60 hours, its light transmittance at 780 nm was 73.5%, and its compressive strength at 80% strain was 2.84 MPa.

[0035] The product S obtained in Example 1 was frozen at (-60℃) for 30 h and 60 h respectively and was denoted as S-LD30 and S-LD60 respectively.

[0036] Figure 5 The electromagnetic shielding effectiveness diagrams of product S and its S-LD30 after 30 hours of freezing and S-LD60 after 60 hours of freezing are shown. Figure 5It can be seen that within the frequency range of 8.2 GHz to 12.4 GHz, the samples exhibited good electromagnetic shielding performance both before and after freezing at -60℃. When the hydrogel thickness was 2 mm, the average electromagnetic shielding efficiencies of S, S-LD30, and S-LD60 were 41.21 dB, 38.19 dB, and 34.28 dB, respectively, and their conductivity values ​​were 10.34 mS / cm, 8.62 mS / cm, and 6.89 mS / cm, respectively. Therefore, the conductive hydrogel prepared in this invention can withstand temperatures of -60℃ for more than 60 hours and still maintain effective electromagnetic shielding performance (>30 dB). The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared in this invention achieves high transmittance, excellent compression resistance, strong freeze resistance, high conductivity, and effective electromagnetic shielding performance under low-temperature conditions.

[0037] Example 2

[0038] The present invention discloses a method for preparing a polyvinyl alcohol-based electromagnetic shielding conductive hydrogel, comprising the following steps:

[0039] (1) Mix 9.8 mL of DMSO with 8 mL of deionized water at 700 r / min for 10 min to obtain an aqueous solution of DMSO;

[0040] (2) Add 1.5g PVA to the DMSO aqueous solution in step (1), heat and stir at 95℃ for 60min, and then let stand for 15min to obtain a mixed solution in which PVA is completely dissolved and there are no excess bubbles.

[0041] (3) Place the mixed solution from step (2) into a custom polytetrafluoroethylene mold, and then place the polytetrafluoroethylene mold containing the mixed solution in the freezer compartment of a refrigerator and freeze for 12 hours to gel; obtain the gel product.

[0042] (4) Mix 2.8g KCl and 50mL deionized water and stir for 10min to obtain solution A; then mix 30mL DMSO and 8mL deionized water and stir for 10min to obtain solution B; then mix solution A and solution B and stir for 10min to prepare an electrolyte salt solution.

[0043] (5) The gel product from step (3) is placed in the electrolyte salt solution from step (4) for 14 hours. After reaching ion exchange equilibrium, a polyvinyl alcohol-based electromagnetic shielding conductive hydrogel is obtained, denoted as S1.

[0044] The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared in Example 2 has a light transmittance of 68.4% at 780 nm, a compressive strength of up to 2.86 MPa at 80% strain, an ionic conductivity of 6.53 mS / cm, and an average electromagnetic shielding effectiveness of 32.53 dB at -60°C for 60 h.

[0045] Comparative Example 1

[0046] Same as Example 1, except that the NaCl content is 2.0g.

[0047] The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared by Comparative Example 1 has a light transmittance of 74.7% at 780 nm, a compressive strength of up to 2.89 MPa at 80% strain, an ionic conductivity of 5.90 mS / cm, and an average electromagnetic shielding effectiveness of 29.35 dB at -60℃ for 60 h.

[0048] Comparative Example 2

[0049] Same as Example 1, except that the ion exchange time is 6 hours.

[0050] The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared by Comparative Example 2 has a light transmittance of 66.8% at 780 nm, a compressive strength of up to 2.91 MPa at 80% strain, an ionic conductivity of 6.17 mS / cm, and an average electromagnetic shielding effectiveness of 30.19 dB at -60℃ for 60 h.

[0051] Comparative Example 3

[0052] Same as Example 1, except that DMSO is not added in step (4).

[0053] The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel prepared by Comparative Example 3 has a light transmittance of 52.7% at 780 nm, a compressive strength of up to 2.35 MPa at 80% strain, an ionic conductivity of 5.54 mS / cm, and an average electromagnetic shielding effectiveness of 28.74 dB at -60℃ for 60 h.

Claims

1. A method for preparing a polyvinyl alcohol-based electromagnetic shielding conductive hydrogel, characterized in that, Includes the following steps: (1) Mix 12 mL of DMSO with 8 mL of deionized water at 700 r / min for 10 min to obtain an aqueous solution of DMSO; (2) Add 1.5g PVA to the DMSO aqueous solution in step (1), heat and stir at 90℃ for 50min, and then let stand for 10min to obtain a mixed solution in which PVA is completely dissolved and there are no excess bubbles. (3) Place the mixed solution from step (2) into a polytetrafluoroethylene mold, and then place the polytetrafluoroethylene mold containing the mixed solution in the freezer compartment of a refrigerator and freeze for 10 hours to gel; obtain the gel product; (4) Mix 2.8g NaCl and 50mL deionized water and stir for 10min to obtain solution A; then mix 30mL DMSO and 8mL deionized water and stir for 10min to obtain solution B; then mix solution A and solution B and stir for 10min to prepare an electrolyte salt solution. (5) The gel product from step (3) was placed in the electrolyte salt solution from step (4) for 12 hours. After reaching ion exchange equilibrium, polyvinyl alcohol-based electromagnetic shielding conductive hydrogel was obtained. The polyvinyl alcohol-based electromagnetic shielding conductive hydrogel obtained by the above method has a light transmittance of 75.2% and a compressive strength of 2.97 MPa at 80% strain. When the hydrogel thickness is 2 mm, the electromagnetic shielding effectiveness is 41.21 dB at room temperature and 34.28 dB at -60℃ for 60 h.

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