A transparent stretchable hydrogel-based terahertz shielding material and a preparation method thereof

Abstract

The present application belongs to the field of electromagnetic shielding materials, and specifically provides a transparent and stretchable hydrogel-based terahertz shielding material and a preparation method thereof, to solve the problems of low visible light transmittance and low mechanical ductility of existing terahertz shielding materials. In the present application, the terahertz shielding material is a hydrogel composed of a three-dimensional polymer network and a polar solution, the polar solution is a mixture of pure water and a polar organic solvent, the polar organic solvent is one of ethanol, ethylene glycol, glycerol and sorbitol, and the volume ratio of pure water to polar organic solvent is 1:1. The hydrogel-based terahertz shielding material provided by the present application has excellent terahertz wave shielding performance, and the shielding efficiency can reach more than 40 dB in the 0.5-4.5 THz wave band, and has excellent visible light transparency and mechanical stretching performance. Meanwhile, the present application provides a preparation method of the hydrogel-based terahertz shielding material, which adopts a chemical polymerization method, and has the advantages of simple preparation process and low preparation cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electromagnetic shielding materials, and specifically provides a transparent and stretchable hydrogel-based terahertz shielding material and a preparation method thereof, which has wide application value in the fields of terahertz imaging, infrared security inspection, radar safety, biological monitoring, etc. BACKGROUND

[0002] Terahertz waves generally refer to electromagnetic waves with an oscillation frequency in the range of 0.1 THz to 10 THz and a wavelength range of 3 um to 3 mm. Due to its unique spectral characteristics, it has important application value in the fields of biomedicine and communication. Terahertz detection technology, as an important part of terahertz research, has important applications in safety inspection, non-destructive imaging, and high-capacity data communication, etc. In recent years, it has received widespread attention from researchers at home and abroad.

[0003] The rapid development of terahertz technology has also brought the need for the development of electromagnetic shielding materials for terahertz waves. Terahertz shielding materials are a class of materials with low transmittance in the terahertz frequency band, commonly used in anti-electromagnetic interference equipment. Terahertz shielding materials mainly include ferrite wave-absorbing materials, nano wave-absorbing materials, polycrystalline iron glass fiber wave-absorbing composite materials, and composite absorbers, etc. However, no matter what material or structure the terahertz shielding material is, it is currently difficult to achieve transparency and high ductility. Specifically, most of the terahertz shielding materials on the market are doped with metals or carbon materials, resulting in opaque terahertz shielding materials, which severely limits the application of terahertz shielding materials in scenarios including optical windows. In addition, although the current terahertz shielding materials have a certain flexibility, the ductility is low, which is difficult to meet the electromagnetic shielding needs of the increasingly developed flexible optoelectronic devices. Therefore, the development of transparent and stretchable terahertz shielding materials is of great significance to the research of terahertz technology. SUMMARY

[0004] In view of the defects and improvement needs in the background art, the purpose of the present application is to provide a transparent and stretchable hydrogel-based terahertz shielding material and a preparation method thereof, to solve the problems of low visible light transmittance and low mechanical ductility of the existing terahertz shielding materials.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] A transparent and stretchable hydrogel-based terahertz shielding material, characterized in that the terahertz shielding material is a hydrogel composed of a three-dimensional polymer network and a polar solution, the polar solution is a mixture of pure water and a polar organic solvent, and the polar organic solvent is one of ethanol, ethylene glycol, glycerol, and sorbitol.

[0007] Further, the volume ratio of pure water to the polar organic solvent in the polar solution is 1:1.

[0008] Further, the preparation method of the transparent stretchable hydrogel-based terahertz shielding material comprises the following steps:

[0009] S1: a mixture of pure water and a polar organic solvent is used as a solvent, and a gel monomer is added to the solvent to prepare a hydrogel prepolymer monomer solution with a concentration of 0.5-3 mol / L; then 0.5-100 mmol / L of an initiator and 1-100 mmol / L of a crosslinking agent are added to the hydrogel prepolymer monomer solution, and after mixing and dissolving, a gel precursor solution is obtained;

[0010] S2: 2% of agarose is added to the gel precursor solution according to the mass fraction, and after stirring at 70-90℃ for 0.5-1h, a hot solution is obtained; the hot solution is polymerized in a cold storage environment at 0-10℃ for 0.5-1h to obtain a physically crosslinked hydrogel;

[0011] S3: the physically crosslinked hydrogel is polymerized and crosslinked in an anaerobic environment to obtain a transparent stretchable hydrogel-based terahertz shielding material.

[0012] Further, the polymerization and crosslinking are carried out under light irradiation or heating conditions; the light irradiation conditions are specifically: polymerization under ultraviolet light for 30-120 minutes, and the polymerization parameters are: a wavelength of 365 nm and a power density of 4 mW cm-2; the heating conditions are specifically: heating in a vacuum oven at 60℃ for 30-120 minutes.

[0013] Further, the gel monomer is one or both of the following: acrylamide, acrylic acid, sodium acrylate, methacrylic acid, vinyl sulfonic acid, sodium styrene sulfonate, 4-vinyl-propyl sulfonate sodium, 2-acrylamido-2-methyl propyl sulfonate sodium, 3-acrylamide propyl-trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, ethylene imine, ethylene amine, and vinyl pyridine.

[0014] The crosslinking agent includes but is not limited to one of N,N'-methylene bisacrylamide, propylene diamine, and acrylic acid, and the initiator includes but is not limited to one of a redox initiator, an organic peroxide, an inorganic peroxide, and an azo initiator.

[0015] Further, the gel precursor solution further contains NaCl with a concentration of 0.5-1 mol / L.

[0016] Based on the above technical solutions, the present application has the following advantages:

[0017] The present application provides a kind of transparent stretchable hydrogel-based terahertz shielding material, specifically, the hydrogel of three-dimensional polymer network and polar solution, its high terahertz shielding performance is due to the strong absorption of polar solution to terahertz electromagnetic wave, its high mechanical ductility is due to the high stretchability of polymer segment, its high transparency is due to the high transparency of polar solution and polymer itself, and the refractive index matching between polar solution and polymer.Based on this, the hydrogel-based terahertz shielding material provided by the present application has excellent terahertz wave shielding performance, and the shielding efficiency can reach more than 40dB in the 0.5-4.5THz band, and has excellent visible light transparency and mechanical tensile properties.

[0018] Meanwhile, the present application provides a preparation method of the transparent stretchable hydrogel-based terahertz shielding material, which adopts chemical polymerization method, and has simple preparation process and low preparation cost. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the hydrogel-based terahertz shielding material in the present application.

[0020] Figure 2 It is a shielding efficiency curve diagram of the hydrogel-based terahertz shielding material in Example 1 in the 0.5-4.5THz band.

[0021] Figure 3 It is a transmittance curve diagram of the hydrogel-based terahertz shielding material in Example 1 in the visible light band.

[0022] Figure 4 It is a stress-strain curve diagram of the hydrogel-based terahertz shielding material in Example 1. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and beneficial effects of the present application clearer and more apparent, the present application will be further described in detail below with reference to the drawings and examples.

[0024] Example 1

[0025] This embodiment provides a kind of transparent stretchable hydrogel-based terahertz shielding material, its structure is as shown in Figure 1 Specifically, the hydrogel of three-dimensional polymer network (hydrophilic chemical crosslinking network) and polar solution, the polar solution is the mixed solution of pure water and polar organic solvent, and the polar organic solvent is ethylene glycol (EG);The hydrogel-based terahertz shielding material is prepared by free radical polymerization under light irradiation, and the specific steps are as follows:

[0026] S1: pure water and EG are mixed as solvent according to the volume ratio of 1:1, acrylamide is used as gel monomer, and a hydrogel prepolymer monomer solution with a concentration of 2 mol / L is prepared; then N,N'-methylene bisacrylamide, 2-hydroxy-2-methylpropiophenone and NaCl are added to the hydrogel prepolymer monomer solution to obtain a gel precursor solution; wherein, N,N'-methylene bisacrylamide is used as a crosslinking agent, 2-hydroxy-2-methylpropiophenone is used as an initiator, and NaCl is used to enhance ionic conductivity, the concentration of N,N'-methylene bisacrylamide is 1 mmol / L, the concentration of 2-hydroxy-2-methylpropiophenone is 2 mmol / L, and the concentration of NaCl is 1 mol / L;

[0027] S2: 2% of agarose is added to the 20 mL gel precursor solution according to the mass fraction to obtain a mixed suspension; the mixed suspension is heated and stirred on a constant temperature heating magnetic stirrer (DF-101S) at 95℃ for 30 minutes to obtain a clear and transparent hot solution; the hot solution is poured into a 4 cm×4 cm mold with a glass substrate and a thickness of 0.5 mm, and after cold storage at 0-10℃ for 30 minutes, the agarose is completely gelled to obtain a physically crosslinked hydrogel;

[0028] S3: the physically crosslinked hydrogel is placed under ultraviolet light for polymerization for 30-120 minutes, and the polymerization parameters are: wavelength 365 nm, power density 4 mW cm -2 ; thus, a transparent stretchable hydrogel-based terahertz shielding material is obtained.

[0029] The hydrogel-based terahertz shielding material prepared in this embodiment is tested, and the shielding efficiency curve thereof in the frequency band of 0.5-4.5 THz is as shown in Figure 2 , the transmittance curve thereof in the visible light frequency band is as shown in Figure 3 , and the stress-strain curve thereof is as shown in Figure 4 ; as can be seen from Figure 2 , the electromagnetic shielding efficiency (EMISE) of the hydrogel-based terahertz shielding material in the frequency band of 0.5-4.5 THz is all above 39 dB, which can effectively offset the interference electromagnetic waves; as can be seen from Figure 3 , the hydrogel-based terahertz shielding material reaches more than 80% in the visible light frequency band of 400 nm-800 nm; as can be seen from Figure 4 , the stretchability of the hydrogel-based terahertz shielding material can reach more than 550%, and the breaking strength is 0.12 MPa, and the flexibility and toughness thereof are sufficient to meet the needs of stretching applications.

[0030] Example 2

[0031] The embodiment provides a transparent stretchable hydrogel-based terahertz shielding material, in particular, a hydrogel formed by a three-dimensional polymer network and a polar solution, the polar solution is a mixed solution of pure water and a polar organic solvent, and the polar organic solvent is glycerol; the hydrogel-based terahertz shielding material is prepared by a free radical polymerization method under heating conditions, and the specific steps are as follows:

[0032] S1: pure water and glycerol are mixed according to a volume ratio of 1:1 as a solvent, acrylamide is used as a hydrogel monomer, and a hydrogel prepolymer monomer solution with a concentration of 2 mol / L is configured; then N,N'-methylenebisacrylamide, 2-hydroxy-2-methylpropiophenone and NaCl are added to the hydrogel prepolymer monomer solution, and a gel precursor solution is obtained; wherein, N,N'-methylenebisacrylamide is used as a crosslinking agent, 2-hydroxy-2-methylpropiophenone is used as an initiator, and NaCl is used for enhancing ionic conductivity, the volume fraction ratio of N,N'-methylenebisacrylamide is 1%, the volume fraction ratio of 2-hydroxy-2-methylpropiophenone is 2%, and the concentration of NaCl is 1 mol / L;

[0033] S2: 2% of agarose is added to the 20 mL gel precursor solution according to a mass fraction to obtain a mixed suspension; the mixed suspension is placed on a constant-temperature heating magnetic stirrer (DF-101S) at 95 DEG C for heating and stirring for 30 minutes to obtain a clear and transparent hot solution; the hot solution is poured into a 4cm*4cm mold with a glass substrate and a thickness of 0.5mm, and after cold storage at 0-10 DEG C for 30 minutes, the agarose is completely gelled to obtain a physically crosslinked hydrogel;

[0034] S3: the physically crosslinked hydrogel is placed in a vacuum oven at 60 DEG C for heating for 30 min to perform thermal initiation of free radical polymerization, so that the transparent stretchable hydrogel-based terahertz shielding material is obtained.

[0035] The hydrogel-based terahertz shielding material prepared in the embodiment is tested, and the hydrogel-based terahertz shielding material also has excellent terahertz wave shielding performance, excellent visible light transparency and mechanical stretching performance.

[0036] The above merely provides a specific implementation of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features unless specifically described, and all features or steps in all methods or processes disclosed can be combined in any manner except for mutually exclusive features and / or steps.

Claims

1. Application of a transparent and stretchable hydrogel as a terahertz shielding material, characterized in that: The terahertz shielding material is a hydrogel composed of a three-dimensional polymer network and a polar solution, wherein the polar solution is a mixture of pure water and a polar organic solvent, wherein the polar organic solvent is one of ethanol, ethylene glycol, glycerol, and sorbitol, and the volume ratio of pure water to the polar organic solvent is 1:1; the three-dimensional polymer network includes: a gel monomer and a crosslinker, wherein the gel monomer is one of acrylamide, acrylic acid, sodium acrylate, methacrylic acid, ethylene sulfonic acid, sodium styrene sulfonate, 4-vinyl-sodium propanesulfonate, 2-acrylamido-2-methylpropanesulfonate, 3-acrylamidopropyl-trimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, and vinylpyridine, and the crosslinker is N,N'-methylenebisacrylamide.

2. Use of the transparent stretchable hydrogel according to claim 1 as a terahertz shielding material, characterized in that: The terahertz shielding material is prepared by the following steps: S1: using a mixture of pure water and a polar organic solvent as a solvent, adding a gel monomer to the solvent to prepare a hydrogel prepolymer monomer solution with a concentration of 0.5 to 3 mol / L; then adding 0.5 to 100 mmol / L of an initiator and 1 to 100 mmol / L of a cross-linking agent to the hydrogel prepolymer monomer solution, mixing and dissolving to obtain a gel precursor solution; S2: adding 2% agarose by mass to the gel precursor solution and stirring at 70°C to 90°C for 0.5 to 1 hour to obtain a hot solution; polymerizing the hot solution in a refrigerated environment at 0 to 10°C for 0.5 to 1 hour to obtain a physically cross-linked hydrogel; S3: The physically cross-linked hydrogel is polymerized and cross-linked in an oxygen-free environment to obtain a transparent and stretchable hydrogel-based terahertz shielding material.

3. Use of the transparent stretchable hydrogel according to claim 2 as a terahertz shielding material, characterized in that: The polymerization cross-linking is carried out under light irradiation or heating conditions; the specific light irradiation conditions are: polymerization under ultraviolet light for 30 to 120 minutes, and the polymerization parameters are: wavelength of 365nm, power density of 4mW cm -2 ; The specific heating conditions are: heating in a vacuum oven at 60°C for 30 to 120 minutes.

4. Use of the transparent stretchable hydrogel according to claim 2 as a terahertz shielding material, characterized in that: The initiator is one of a redox initiator, an organic peroxide, an inorganic peroxide and an azo initiator.

5. Use of the transparent stretchable hydrogel according to claim 2 as a terahertz shielding material, characterized in that: The gel precursor solution is further added with NaCl having a concentration of 0.5 to 1 mol / L.

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