CN116002657A - Polyacrylamide hydrogel wave-absorbing material and preparation method thereof - Google Patents
Polyacrylamide hydrogel wave-absorbing material and preparation method thereof Download PDFInfo
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- CN116002657A CN116002657A CN202211615636.8A CN202211615636A CN116002657A CN 116002657 A CN116002657 A CN 116002657A CN 202211615636 A CN202211615636 A CN 202211615636A CN 116002657 A CN116002657 A CN 116002657A
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- 239000000017 hydrogel Substances 0.000 title claims abstract description 114
- 239000011358 absorbing material Substances 0.000 title claims abstract description 69
- 238000002360 preparation method Methods 0.000 title claims abstract description 49
- 238000010521 absorption reaction Methods 0.000 claims abstract description 10
- 239000000178 monomer Substances 0.000 claims description 113
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims description 93
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 38
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- JKNCOURZONDCGV-UHFFFAOYSA-N 2-(dimethylamino)ethyl 2-methylprop-2-enoate Chemical compound CN(C)CCOC(=O)C(C)=C JKNCOURZONDCGV-UHFFFAOYSA-N 0.000 claims description 3
- CYUZOYPRAQASLN-UHFFFAOYSA-N 3-prop-2-enoyloxypropanoic acid Chemical compound OC(=O)CCOC(=O)C=C CYUZOYPRAQASLN-UHFFFAOYSA-N 0.000 claims description 3
- IGPAOZODNDEPJF-UHFFFAOYSA-N C(C=C)(=O)NCC1=C(C(=O)OCCC)C=C(C(=C1O)O)O Chemical compound C(C=C)(=O)NCC1=C(C(=O)OCCC)C=C(C(=C1O)O)O IGPAOZODNDEPJF-UHFFFAOYSA-N 0.000 claims description 3
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- OIWOHHBRDFKZNC-UHFFFAOYSA-N cyclohexyl 2-methylprop-2-enoate Chemical compound CC(=C)C(=O)OC1CCCCC1 OIWOHHBRDFKZNC-UHFFFAOYSA-N 0.000 claims description 3
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- FSAJWMJJORKPKS-UHFFFAOYSA-N octadecyl prop-2-enoate Chemical compound CCCCCCCCCCCCCCCCCCOC(=O)C=C FSAJWMJJORKPKS-UHFFFAOYSA-N 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- QJWFJOSRSZOLKK-UHFFFAOYSA-N prop-2-enamide Chemical class NC(=O)C=C.NC(=O)C=C QJWFJOSRSZOLKK-UHFFFAOYSA-N 0.000 claims description 3
- MUTNCGKQJGXKEM-UHFFFAOYSA-N tamibarotene Chemical compound C=1C=C2C(C)(C)CCC(C)(C)C2=CC=1NC(=O)C1=CC=C(C(O)=O)C=C1 MUTNCGKQJGXKEM-UHFFFAOYSA-N 0.000 claims description 3
- PQSQBXGSIRXRFL-UHFFFAOYSA-N 2-methylpropanamide;dihydrochloride Chemical compound Cl.Cl.CC(C)C(N)=O PQSQBXGSIRXRFL-UHFFFAOYSA-N 0.000 claims description 2
- FJWSMXKFXFFEPV-UHFFFAOYSA-N prop-2-enamide;hydrochloride Chemical compound Cl.NC(=O)C=C FJWSMXKFXFFEPV-UHFFFAOYSA-N 0.000 claims description 2
- RRHXZLALVWBDKH-UHFFFAOYSA-M trimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azanium;chloride Chemical compound [Cl-].CC(=C)C(=O)OCC[N+](C)(C)C RRHXZLALVWBDKH-UHFFFAOYSA-M 0.000 claims description 2
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- VODBVEAKEQILAQ-UHFFFAOYSA-N 2-(dimethylamino)ethyl prop-2-enoate;2-methylprop-2-enoic acid Chemical compound CC(=C)C(O)=O.CN(C)CCOC(=O)C=C VODBVEAKEQILAQ-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention relates to a polyacrylamide hydrogel wave-absorbing material and a preparation method thereof. The polyacrylamide hydrogel wave-absorbing material prepared by the invention has excellent wave-absorbing performance as a wave-absorbing agent, and when the matching thickness is 2.0-5.0 mm and the frequency is 2-18GHz, the minimum reflection loss of the hydrogel wave-absorbing agent reaches-33 to-55 dB, and the effective absorption bandwidth is 3.7-5.3 GHZ.
Description
Technical Field
The invention belongs to the technical field of electromagnetic wave absorbing materials. More specifically, the invention relates to a polyacrylamide hydrogel wave-absorbing material and a preparation method of the polyacrylamide hydrogel wave-absorbing material.
Background
In recent years, communication technology and electronic devices have been continuously developed, which bring convenience to human beings and also bring unavoidable electromagnetic wave radiation pollution. Electromagnetic radiation pollution has a great negative impact on human health, ecological environment and normal operation of electronic equipment. A large number of workers have begun to develop electromagnetic wave absorbing materials excellent in performance for solving electromagnetic wave radiation pollution. The development of green, low-cost and high-performance electromagnetic absorption materials is a focus of research for various nationalities.
The ideal wave absorbing material has the advantages of light weight, wide effective absorption frequency, thin thickness, low density and the like. The carbon material has the advantages of excellent chemical stability, low density, low loss, adjustable dielectric constant, compatibility with other materials, easy control of surface microstructure and the like, and is one of candidate materials of the microwave absorber. However, the pure carbon material has impedance mismatch due to excessively high dielectric constant and good conductivity, and finally can achieve reflection loss, but has narrower effective absorption bandwidth.
Research shows that introducing nitrogen into the carbon skeleton can change charge density around carbon, and can introduce defects which can cause defect polarization; meanwhile, carbon-nitrogen bonds can be used as dipoles to cause dipole polarization, so that the absorption bandwidth can be effectively improved. Polyacrylamide hydrogels are a class of polymers with three-dimensional network structures that are polymerized by simple free radicals. The hydrogel can be obtained by polymerizing different hydrophilic monomers and hydrophobic monomers through certain chemical or physical crosslinking, so that the polyacrylamide hydrogel has high stability. The polyacrylamide hydrogel can be used in various fields such as water treatment, agricultural water retention, electrophoretic separation of proteins and the like, but the research on the wave-absorbing characteristics of nitrogen-doped polyacrylamide hydrogel derived carbon is less.
Based on the analysis, the nitrogen-doped polyacrylamide hydrogel wave-absorbing material prepared by using the polyacrylamide hydrogel as a precursor through a freeze drying-carbonization process has important application prospect in the field of microwave absorption, and the method provides a new thought for electromagnetic pollution protection and military stealth.
Disclosure of Invention
Technical problem to be solved
The invention aims to provide a polyacrylamide hydrogel wave-absorbing material.
The invention further aims at providing a preparation method of the polyacrylamide hydrogel wave-absorbing material.
Technical proposal
The invention is realized by the following technical scheme.
The invention relates to a preparation method of a polyacrylamide hydrogel wave-absorbing material.
The preparation method comprises the following preparation steps:
A. preparation of acrylamide mixture
Acrylamide monomer, 4-acryloylmorpholine, N-vinylcaprolactam, acrylic acid monomer, acrylic ester monomer and acrylamide derivative monomer containing capsaicin functional structure according to the mole ratio of 200:0 to 10:0 to 15:0 to 50:0 to 5: mixing 0-1, adding deionized water, and performing ultrasonic dispersion to obtain an acrylamide mixed solution with the total monomer content of 5-25% by weight.
B. Synthesis of sol
Adding an initiator accounting for 0.1-1.5% of the total weight of monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 1-6 hours under the protection of nitrogen at the temperature of 58-85 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
C. preparation of hydrogels
Letting the polyacrylamide sol obtained in the step B stand and cool for 12 hours at room temperature in a closed container, so as to obtain the polyacrylamide hydrogel with the following chemical structural formula:
wherein:
R 1 h, CH of a shape of H, CH 2 OH or (CH) 2 ) 2 OH；
R 2 Is OH, CH 3 、COOH、COOCH 3 Or (b)
R 3 H, CH of a shape of H, CH 2 COOH or
R 4 Is H or CH 3 ；
R 5 Is OCH 3 、OCH 2 (CH 2 ) 16 CH 3 、O(CH 2 ) 2 N(CH 3 ) 2 、O(CH 2 ) 2 OCOCH 2 COCH 3 、OCH 2 CH(CH 3 ) 2 、O(CH 2 ) 2 COOH、
D. Preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C, placing the polyacrylamide hydrogel into a crucible, then placing the crucible into a tube furnace, heating to 600-1000 ℃ under the condition of nitrogen protection atmosphere, preserving heat for 1-2 h at the temperature, cooling to room temperature, and grinding to obtain the polyacrylamide hydrogel wave-absorbing material.
According to a preferred embodiment of the present invention, in step a, the acrylamide monomer is one or more acrylamide monomers selected from the group consisting of acrylamide, N-methylolacrylamide and N-hydroxyethyl acrylamide; the acrylic monomer is one or more acrylic monomers selected from acrylic acid, itaconic acid or 2-phenylchloroethyl acrylic acid; the acrylic ester monomer is one or more acrylic ester monomers selected from methyl methacrylate, octadecyl acrylate, dimethylaminoethyl methacrylate, acetoacetoxyethyl methacrylate, beta-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl methacrylate, cyclohexyl methacrylate or methacryloyloxyethyl trimethyl ammonium chloride; the capsaicin functional structural acrylamide derivative monomer is one or more selected from N- (2, 4-dimethyl-5-hydroxybenzyl) acrylamide, N- (2, 5-dimethyl-3-hydroxy-4-acrylamide methylbenzyl) acrylamide, N- (3, 5-dimethyl-4-hydroxybenzyl) acrylamide, N- (4, 5-dimethyl-2-hydroxy-3-acrylamide methylbenzyl) acrylamide, N- (4, 6-dimethyl-2-hydroxy-3-acrylamide methylbenzyl) acrylamide, N- (3-methyl-2, 5-dihydroxy-4, 6-diacrylamide methylbenzyl) acrylamide, N- (3, 4-dihydroxy-6-acrylamide methylbenzyl) acrylamide, N- (2, 5-dihydroxy-4-acrylamide methylbenzyl) acrylamide, N- (2, 4-dihydroxy-5-acrylamide methylbenzyl) acrylamide, N- (2, 6-trihydroxy-3, 5-diacrylamide methylbenzyl) acrylamide, N- (2, 4, 6-trihydroxy-3, 5-dicarboxyl) acrylamide, N- (2, 4-dihydroxy-3, 5-dicarboxyl) acrylamide, N- (2, 4-trihydroxy-3, 5-hydroxybenzyl) acrylamide and N- (2, 4-hydroxy-3, 5-dicarboxyl) acrylamide Acrylamide derivative monomers of N- (2, 3, 4-trihydroxy-6-propoxycarbonylbenzyl) acrylamide, N- ((4-hydroxy-3-acrylamidomethyl naphthalene) methyl) acrylamide, N- ((2-hydroxynaphthalene) methyl) acrylamide, N- (3-methoxy-4-hydroxybenzyl) acrylamide, N- (1-methoxy-4-hydroxy-2-pyridazinyl) acrylamide, N- (2-hydroxy-3-carbamoylbenzyl) acrylamide, N- (2, 3-dihydroxy-6-aminoethyl-4, 5-bisacrylamidomethylbenzyl) acrylamide hydrochloride.
According to another preferred embodiment of the present invention, in step a, ultrasonic dispersion is performed for 5 to 30 minutes using a bransenic ultrasonic cleaner under 40KHz conditions.
According to another preferred embodiment of the invention, in step B, the initiator is one or more initiators selected from azobisisobutyronitrile, ammonium persulfate, potassium persulfate or 2, 2-azobis (2-methylpropionamide) dihydrochloride.
According to another preferred embodiment of the present invention, in the step B, the polyacrylamide sol is a solution containing a large amount of water at a temperature of 30 to 85 ℃ and having fluidity.
According to another preferred embodiment of the present invention, in the step D, the freeze-drying is performed at a temperature of-45 to-55 ℃ for 46 to 52 hours.
According to another preferred embodiment of the present invention, in step D, the temperature is heated to 700 to 900 ℃ at a temperature rising rate of 2 to 5 ℃/min under the condition of a nitrogen atmosphere.
According to another preferred embodiment of the present invention, in step D, a natural agate mortar is used to grind to a particle size of 100 to 500 mesh at room temperature.
The invention relates to a polyacrylamide hydrogel wave-absorbing material prepared by the preparation method.
According to another preferred embodiment of the invention, the minimum reflection loss of the polyacrylamide hydrogel wave-absorbing material reaches-33 to-55 dB under the condition of matching the thickness of 2.0-5.0 mm and the frequency of 2-18GHz, and the effective absorption bandwidth is 3.7-5.3 GHZ.
The present invention will be described in more detail below.
The invention relates to a preparation method of a polyacrylamide hydrogel wave-absorbing material.
The preparation method comprises the following preparation steps:
A. preparation of acrylamide mixture
Acrylamide monomer, 4-acryloylmorpholine, N-vinylcaprolactam, acrylic acid monomer, acrylic ester monomer and acrylamide derivative monomer containing capsaicin functional structure according to the mole ratio of 200:0 to 10:0 to 15:0 to 50:0 to 5: mixing 0-1, adding deionized water, and performing ultrasonic dispersion to obtain an acrylamide mixed solution with the total monomer content of 5-25% by weight.
In the invention, the main function of the acrylamide monomer in preparing the polyacrylamide hydrogel wave-absorbing material is that the acrylamide monomer can polymerize to form the main chain of the polyacrylamide hydrogel. The acrylamide monomer used in the present invention is one or more acrylamide monomers selected from acrylamide, N-methylolacrylamide or N-hydroxyethyl acrylamide, which are all products currently commercially available, for example, products sold under the trade name acrylamide by Jiuchang chemical industry Co., ltd. In Jiangxi;
in the invention, the main function of the 4-acryloylmorpholine in preparing the polyacrylamide hydrogel wave-absorbing material is to provide very good flexibility and certain hardness. The 4-propenoyl morpholine used in the present invention is a product currently marketed, for example, by the company Ara Ding Shiji under the trade name 4-propenoyl morpholine.
In the invention, the main function of N-vinyl caprolactam in preparing the polyacrylamide hydrogel wave-absorbing material is to provide very good flexibility and certain hardness. The N-vinylcaprolactam used in the present invention is a product which is currently commercially available, for example, a product sold under the trade name N-vinylcaprolactam by the company Ama Ding Shiji.
In the invention, the main function of the acrylic monomer in preparing the polyacrylamide hydrogel wave-absorbing material is that the acrylic monomer is combined with more side chains. The acrylic monomer used in the present invention is one or more acrylic monomers selected from acrylic acid, itaconic acid or 2-phenylchloroethyl acrylic acid, which are all products currently commercially available, for example, products sold under the trade name acrylic acid by the company of the national chemical reagent, itaconic acid sold under the trade name itaconic acid by the company of the microphone biochemistry, inc.;
in the invention, the main function of the acrylate monomer in preparing the polyacrylamide hydrogel wave-absorbing material is that the acrylate monomer endows the hydrogel wave-absorbing material with flexibility, and meanwhile, the hydrophobic property of the acrylate monomer is increased, and physical crosslinking is provided through hydrophobic association, so that the structure of the hydrogel is reversible. The acrylate monomer used in the present invention is one or more acrylate monomers selected from the group consisting of methyl methacrylate, stearyl acrylate, dimethylaminoethyl methacrylate, acetoacetoxyethyl methacrylate, beta-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl methacrylate, cyclohexyl methacrylate, and oxyethyl methacrylate trimethyl ammonium chloride, which are all currently commercially available products such as methyl methacrylate sold under the trade name methyl methacrylate by the national chemical reagent company, and stearyl methacrylate sold under the trade name stearyl methacrylate by the Datang chemical reagent company;
in the invention, the main function of the acrylamide derivative monomer with the capsaicin functional structure in the preparation of the polyacrylamide hydrogel wave-absorbing material is to provide a chemical crosslinking function and improve the structural stability of the hydrogel. The capsaicin-containing functional structural acrylamide derivative monomer used in the invention is one or more monomers selected from N- (2, 4-dimethyl-5-hydroxybenzyl) acrylamide, N- (2, 5-dimethyl-3-hydroxy-4-acrylamidomethyl) acrylamide, N- (3, 5-dimethyl-4-hydroxybenzyl) acrylamide, N- (4, 5-dimethyl-2-hydroxy-3-acrylamidomethyl) acrylamide, N- (4, 6-dimethyl-2-hydroxy-3-acrylamidomethyl) acrylamide, N- (3-methyl-2, 5-dihydroxy-4, 6-bisacrylamide-methylbenzyl) acrylamide, N- (3, 4-dihydroxy-6-acrylamidomethyl) acrylamide, N- (2, 5-dihydroxy-4-acrylamidomethyl) acrylamide, N- (2, 4-dihydroxy-5-acrylamidomethyl) acrylamide, N- (2, 4, 6-trihydroxy-3, 5-dimethylbenzyl) acrylamide, N- (2, 4-trihydroxy-5-hydroxybenzyl) acrylamide and N- (2, 4-trihydroxybenzyl) acrylamide Acrylamide derivative monomers of N- (2, 3, 4-trihydroxy-6-methoxycarbonylbenzyl) acrylamide, N- (2, 3, 4-trihydroxy-6-propoxycarbonylbenzyl) acrylamide, N- ((4-hydroxy-3-acrylamidomethyl naphthalene) methyl) acrylamide, N- ((2-hydroxynaphthalene) methyl) acrylamide, N- (3-methoxy-4-hydroxybenzyl) acrylamide, N- (1-methoxy-4-hydroxy-2-pyridazinyl) acrylamide, N- (2-hydroxy-3-carbamoylbenzyl) acrylamide, N- (2, 3-dihydroxy-6-aminoethyl-4, 5-diacrylamidomethyl) acrylamide hydrochloride. These functional structure-containing capsaicin acrylamide derivative monomers were prepared according to the preparation method described in CN 103951578A.
In the invention, when the dosage of the acrylamide monomer, the N-vinyl caprolactam, the acrylic acid monomer, the acrylic acid ester monomer and the acrylamide derivative monomer containing the capsaicin functional structure is in the range, when preparing the acrylamide mixed solution, 4-acryloylmorpholine can be omitted under the condition of using the N-vinyl caprolactam, if the dosage of the 4-acryloylmorpholine exceeds 10, the partial agglomeration of reaction products is caused, the normal reaction is not facilitated, and meanwhile, the mechanical property of the wave absorbing material is reduced; therefore, it is preferable that the amount of 4-acryloylmorpholine is 0 to 10.
In the invention, when the dosages of the acrylamide monomer, the 4-acryloylmorpholine, the acrylic acid monomer, the acrylic ester monomer and the functional structure acrylamide derivative monomer containing capsaicin are in the range, when preparing the acrylamide mixed solution, N-vinyl caprolactam can be omitted under the condition of using the 4-acryloylmorpholine, if the dosage of the N-vinyl caprolactam exceeds 15, the reaction product is partially agglomerated, the normal reaction is not facilitated, and the mechanical property of the wave absorbing material is reduced; therefore, it is preferable to use N-vinylcaprolactam in an amount of 0 to 15.
In the invention, when the dosage of the acrylamide monomer, the 4-acryloylmorpholine, the N-vinylcaprolactam, the acrylic ester monomer and the functional structure acrylamide derivative monomer containing capsaicin are in the range, when preparing the acrylamide mixed solution, the acrylic acid monomer can be omitted under the condition of simultaneously using the 4-acryloylmorpholine and the N-vinylcaprolactam, if the dosage of the acrylic acid monomer exceeds 50, the reaction product is partially agglomerated, the normal reaction is not facilitated, and the mechanical property of the wave absorbing material is reduced; therefore, it is reasonable to use the acrylic monomer in an amount of 0 to 50.
In the invention, when the dosage of the acrylamide monomer, the 4-acryloylmorpholine, the N-vinylcaprolactam, the acrylic acid monomer and the functional structure acrylamide derivative monomer containing capsaicin is in the range, when the acrylamide mixed solution is prepared, the acrylic acid monomer can be omitted when the acrylic acid monomer is used, if the dosage of the acrylic acid monomer exceeds 5, the reaction part is agglomerated because the monomer cannot be uniformly dispersed in deionized water, the normal reaction is not facilitated, and meanwhile, the mechanical property of the wave absorbing material is reduced; thus, the acrylate monomer is preferably used in an amount of 0 to 5.
In the invention, when the dosages of the acrylamide monomer, the 4-acryloylmorpholine, the N-vinylcaprolactam, the acrylic acid monomer and the acrylic ester monomer are in the range, when preparing an acrylamide mixed solution, the acrylamide derivative monomer with a capsaicin functional structure can not be used under the condition that the 4-acryloylmorpholine and the isobornyl methacrylate monomer are used according to a certain proportion, if the dosage of the acrylamide derivative monomer with the capsaicin functional structure exceeds 1, the excessive dosage can lead the monomer to be insufficiently dissolved, the reaction part is agglomerated, the viscosity of the polymer is excessively high, and the mechanical property of the wave absorbing material is reduced; therefore, it is preferable that the amount of the functional structure-containing acrylamide derivative is 0 to 1.
In the step A, acrylamide monomer, 4-acryloylmorpholine, N-vinylcaprolactam, acrylic acid monomer, acrylic ester monomer and capsaicin functional structure-containing acrylamide derivative monomer are subjected to ultrasonic dispersion in deionized water for 5-30 min under the condition of 40KHz by using a BRANSONIC ultrasonic cleaner sold by American company under the trade name of a Branson desk ultrasonic cleaner, so as to obtain an acrylamide mixed solution with the total monomer content of 5-25% by weight.
According to the present invention, if the concentration of the acrylamide mixed solution is less than 5%, a product having a high viscosity, a large relative molecular mass and wave absorbing properties is not obtained; if the concentration of the acrylamide mixed solution is higher than 25%, the three-dimensional network structure is not generated, and the wave absorbing performance is affected; therefore, the concentration of the acrylamide mixed liquid is suitably 5 to 25%, preferably 8 to 20%, more preferably 10 to 18%.
B. Synthesis of sol
Adding an initiator accounting for 0.1-1.5% of the total weight of monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 1-6 hours under the protection of nitrogen at the temperature of 58-85 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
the initiator used in the present invention is one or more initiators selected from azobisisobutyronitrile, ammonium persulfate, potassium persulfate or 2, 2-azobis (2-methylpropionami) dihydrochloride, which are all currently commercially available products such as 2, 2-azobis (2-methylpropionami) dihydrochloride sold by the company of alaa Ding Shiji under the trade name of 2, 2-azobis (2-methylpropionami) dihydrochloride, azobisisobutyronitrile sold by the company of the metallocene chemical reagent of the Tianjin market under the trade name of azobisisobutyronitrile, potassium persulfate sold by the company of the national chemical reagent company under the trade name of potassium persulfate;
in this step, the amount of the initiator is 0.1 to 1.5% by weight based on the total weight of the monomers, but it is not preferable to use the initiator in an amount exceeding the above range because too low an amount of the initiator results in incomplete polymerization of acrylamide and too high an amount of the initiator results in low viscosity of the reaction solution, which is disadvantageous in obtaining the polyacrylamide sol.
The reaction mixture reacts for 1 to 6 hours under the protection of nitrogen and at the temperature of 58 to 85 ℃. When the reaction time is within the above range, if the reaction temperature is lower than 58 ℃, it is unfavorable to initiate polymerization of the monomer; if the reaction temperature is higher than 85 ℃, the properties of the prepared hydrogel are reduced; thus, the reaction temperature is suitably from 58 to 85 ℃, preferably from 60 to 80 ℃, more preferably from 64 to 76 ℃;
when the reaction temperature is within the range, if the reaction time is shorter than 1h, it is unfavorable to initiate the sufficient polymerization of the monomer; if the reaction time is longer than 6 hours, the performance of the prepared hydrogel material is reduced; thus, the reaction time is suitably from 1 to 6 hours, preferably from 1.8 to 5.2 hours, more preferably from 2.5 to 4.5 hours;
according to the invention, the polyacrylamide sol is a solution which contains a large amount of water at a temperature of 30-85 ℃ and has fluidity.
C. Preparation of hydrogels
C, standing and cooling the polyacrylamide sol obtained in the step B for 12 hours at room temperature in a closed container, and analyzing a product obtained in the preparation step by adopting a conventional Fourier transform infrared spectrum analysis method, wherein the infrared spectrum analysis result is shown in the attached figure 1; from FIG. 1, it can be confirmed that the product is a polyacrylamide hydrogel, which is a polyacrylamide hydrogel having the following chemical structural formula:
wherein:
R 1 h, CH of a shape of H, CH 2 OH or (CH) 2 ) 2 OH；
R 2 Is OH, CH 3 、COOH、COOCH 3 Or (b)
R 3 H, CH of a shape of H, CH 2 COOH or
R 4 Is H or CH 3 ；
R 5 Is OCH 3 、OCH 2 (CH 2 ) 16 CH 3 、O(CH 2 ) 2 N(CH 3 ) 2 、O(CH 2 ) 2 OCOCH 2 COCH 3 、OCH 2 CH(CH 3 ) 2 、O(CH 2 ) 2 COOH、
D. Preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C, placing the polyacrylamide hydrogel into a crucible, then placing the crucible into a tube furnace, heating to 600-1000 ℃ under the condition of nitrogen protection atmosphere, preserving heat for 1-2 h at the temperature, cooling to room temperature, and grinding to obtain the polyacrylamide hydrogel wave-absorbing material.
In this step, the freeze-drying is performed at a temperature of-45 to-55 ℃ for 46 to 52 hours.
The polyacrylamide hydrogel obtained by freeze-drying was analyzed under conventional analysis conditions using a device sold under the trade name S-4800 by Hitachi, inc., and the analysis results are shown in FIG. 2, and it can be confirmed from FIG. 2 that the freeze-dried polyacrylamide hydrogel has a three-dimensional network structure.
In this step, the freeze-dried polyacrylamide hydrogel is heated to 600-1000 ℃ under a nitrogen atmosphere, with the aim of maintaining structural stability and the composite material being able to be sufficiently pyrolyzed and carbon reduced, preferably at a heating rate of 2-5 ℃/min to 700-900 ℃. The tube furnace used in the present invention is a tube furnace commonly used in the art, such as a tube furnace sold under the trade name open vacuum/atmosphere tube furnace by Tianjin medium ring electric furnace Co., ltd.
In this step, a natural agate mortar is used to grind to a particle size of 100 to 500 mesh at room temperature.
The invention relates to a polyacrylamide hydrogel wave-absorbing material prepared by the preparation method.
According to the theory of the coaxial method, the Agilent E5224APNA vector network analyzer is used for detection, and the obtained polyacrylamide hydrogel wave-absorbing material has wave-absorbing performance within the wavelength range of 2-18 GHZ.
The minimum reflection loss of the polyacrylamide hydrogel wave-absorbing material reaches-33 to-55 dB under the condition of matching the thickness of 2.0-5.0 mm and the frequency of 2-18GHz, and the effective absorption bandwidth is 3.7-5.3 GHZ, and the specific situation is shown in figures 3-7.
Advantageous effects
The beneficial effects of the invention are as follows:
compared with the prior art, the preparation method of the polyacrylamide hydrogel precursor and the polyacrylamide hydrogel wave-absorbing material is simple, raw materials are easy to obtain, and the cost is low so that mass production can be realized. Compared with the existing wave-absorbing material, the polyacrylamide hydrogel wave-absorbing material prepared by the invention has excellent wave-absorbing performance as a wave-absorbing agent, and when the matching thickness is 2.0-5.0 mm and the frequency is 2-18GHz, the minimum reflection loss of the hydrogel wave-absorbing agent reaches-33 to-55 dB, and the effective absorption bandwidth is 3.7-5.3 GHZ.
Drawings
FIG. 1 is an infrared spectrum of a polyacrylamide hydrogel prepared in example 1;
FIG. 2 is a scanning electron microscope image of a polyacrylamide hydrogel of the present invention after lyophilization;
FIG. 3 is a graph showing the reflection loss of the polyacrylamide hydrogel wave-absorbing material prepared in example 1 at 2-18 GHZ;
FIG. 4 is a graph showing the reflection loss of the polyacrylamide hydrogel wave-absorbing material prepared in example 2 at 2-18 GHZ;
FIG. 5 is a graph showing the reflection loss of the polyacrylamide hydrogel wave-absorbing material prepared in example 3 at 2-18 GHZ;
FIG. 6 is a graph showing the reflection loss of the polyacrylamide hydrogel wave-absorbing material prepared in example 4 at 2-18 GHZ;
FIG. 7 is a graph showing the reflection loss of the polyacrylamide hydrogel wave-absorbing material prepared in example 5 at 2-18 GHZ;
Detailed Description
The invention will be better understood by the following examples.
Example 1: preparation of the polyacrylamide hydrogel wave-absorbing material
The implementation steps of this embodiment are as follows:
A. preparation of acrylamide mixture
Acrylamide monomer, 4-acryloylmorpholine acrylic acid monomer, isobornyl methacrylate acrylic acid ester monomer and N- (2, 4-dimethyl-5-hydroxybenzyl) acrylamide functional structure-containing capsaicin acrylamide derivative monomer are mixed according to a molar ratio of 200:5:12:12:0:0.2, adding deionized water, and performing ultrasonic dispersion for 12min under the condition of 40KHz by using a BRANSONIC ultrasonic cleaner to obtain an acrylamide mixed solution with the total monomer content of 25% by weight;
B. synthesis of sol
Adding an azodiisobutyronitrile initiator accounting for 1.5% of the total weight of the monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 4 hours under the protection of nitrogen at the temperature of 70 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
C. preparation of hydrogels
Allowing the polyacrylamide sol obtained in the step B to stand and cool for 12 hours at room temperature in a closed container, so as to obtain the polyacrylamide hydrogel with the chemical structural formula described in the specification: the infrared spectrum analysis result of the polyacrylamide hydrogel is shown in the attached figure 1;
D. preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C at the temperature of minus 45 ℃ for 50 hours, placing the polyacrylamide hydrogel in a crucible, then placing the crucible in a tube furnace, heating to 700 ℃ at the heating rate of 4 ℃/min under the condition of nitrogen protection atmosphere, preserving heat for 1.2 hours at the temperature, cooling to room temperature, and grinding to the granularity of 200-300 meshes to obtain the polyacrylamide hydrogel wave-absorbing material. The polyacrylamide hydrogel is subjected to observation by a scanning electron microscope after freeze drying, and the result is shown in fig. 2;
the polyacrylamide hydrogel wave-absorbing material prepared in the embodiment is uniformly mixed with paraffin according to the weight ratio of 1:5 to prepare a coaxial circular ring shape with the inner diameter of 3.04mm and the outer diameter of 7.00mm, then the complex dielectric constant and the magnetic permeability value in the frequency range of 2-18GHz are tested by adopting a coaxial method by using an Agilent E5224APNA vector network analyzer, the reflection loss diagram of the polyacrylamide hydrogel wave-absorbing material is calculated according to the transmission line theory, and the result is shown in the attached figure 3. As can be seen from FIG. 3, the minimum reflection loss is-44 dB under the conditions of matching thickness of 3.0mm and frequency of 2-18GHz, and the effective bandwidth is 3.8GHz.
Example 2: preparation of the polyacrylamide hydrogel wave-absorbing material
The implementation steps of this embodiment are as follows:
A. preparation of acrylamide mixture
N-methylol acrylamide monomer, N-vinyl caprolactam acrylic acid monomer, octadecyl acrylate monomer and N- (2, 5-dimethyl-3-hydroxy-4-acrylamide methylbenzyl) acrylamide with a capsaicin-containing functional structure acrylamide derivative monomer are mixed according to a molar ratio of 200:8:15:0:4:0.5, adding deionized water, and performing ultrasonic dispersion for 5min under the condition of 40KHz by using a BRANSONIC ultrasonic cleaner to obtain an acrylamide mixed solution with the total monomer content of 5% by weight;
B. synthesis of sol
Adding ammonium persulfate initiator accounting for 0.4 percent of the total weight of the monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 3 hours under the protection of nitrogen at the temperature of 78 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
C. preparation of hydrogels
Allowing the polyacrylamide sol obtained in the step B to stand and cool for 12 hours at room temperature in a closed container, so as to obtain the polyacrylamide hydrogel with the chemical structural formula described in the specification:
D. preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C at the temperature of minus 50 ℃ for 46 hours, placing the polyacrylamide hydrogel in a crucible, then placing the crucible in a tube furnace, heating to 890 ℃ at the heating rate of 2 ℃/min under the condition of nitrogen protection atmosphere, preserving the heat at the temperature for 1.5 hours, cooling to room temperature, and grinding to the granularity of 300-400 meshes to obtain the polyacrylamide hydrogel wave-absorbing material.
The polyacrylamide hydrogel wave-absorbing material prepared in this example was examined in the same manner as in example 1, and the results are shown in FIG. 4. As can be seen from FIG. 4, the minimum reflection loss is-35 dB under the conditions of matching thickness of 5.0mm and frequency of 2-18GHz, and the effective bandwidth is 5.3GHz.
Example 3: the implementation steps of this example of the polyacrylamide hydrogel wave absorbing material of the present invention are as follows:
A. preparation of acrylamide mixture
N-hydroxyethyl acrylamide monomer, acrylic acid monomer, methacrylic acid dimethylaminoethyl acrylate monomer and N- (2, 4-dihydroxyl-5-acrylamide methylbenzyl) acrylamide monomer containing capsaicin functional structure acrylamide derivative monomer are mixed according to the mole ratio of 200:0:4:24:5:0.8, adding deionized water, and performing ultrasonic dispersion for 30min under the condition of 40KHz by using a BRANSONIC ultrasonic cleaner to obtain an acrylamide mixed solution with the total monomer content of 14% by weight;
B. synthesis of sol
Adding a potassium persulfate initiator accounting for 0.1 percent of the total weight of the monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 6 hours under the protection of nitrogen at the temperature of 58 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
C. preparation of hydrogels
Allowing the polyacrylamide sol obtained in the step B to stand and cool for 12 hours at room temperature in a closed container, so as to obtain the polyacrylamide hydrogel with the chemical structural formula described in the specification:
D. preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C at the temperature of minus 55 ℃ for 48 hours, placing the polyacrylamide hydrogel in a crucible, then placing the crucible in a tube furnace, heating to 1000 ℃ at the heating rate of 3 ℃/min under the condition of nitrogen protection atmosphere, preserving heat for 1.0 hour at the temperature, cooling to room temperature, and grinding to the granularity of 200-300 meshes to obtain the polyacrylamide hydrogel wave-absorbing material.
The polyacrylamide hydrogel wave-absorbing material prepared in this example was examined in the same manner as in example 1, and the results are shown in FIG. 5. As can be seen from FIG. 5, the minimum reflection loss is-55 dB under the conditions of matching thickness of 3.5mm and frequency of 2-18GHz, and the effective bandwidth is 3.8GHz.
Example 4: the implementation steps of this example of the polyacrylamide hydrogel wave absorbing material of the present invention are as follows:
A. preparation of acrylamide mixture
N-methylol acrylamide monomer, 4-acryloylmorpholine, N-vinyl caprolactam, acrylic acid monomer, acetoacetyl ethyl methacrylate acrylate monomer and N- (2, 4, 6-trihydroxy-3, 5-diacrylamide methylbenzyl) acrylamide derivative monomer containing a capsaicin functional structure are mixed according to the mole ratio of 200:2:0:50:1:1.0, adding deionized water, and performing ultrasonic dispersion for 18min under the condition of 40KHz by using a BRANSONIC ultrasonic cleaner to obtain an acrylamide mixed solution with the total monomer content of 9% by weight;
B. synthesis of sol
Adding a 2, 2-azo-bis (2-methylpropyl-mi) dihydrochloride initiator accounting for 0.8 percent of the total weight of the monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 5 hours under the protection of nitrogen and at the temperature of 64 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
C. preparation of hydrogels
Allowing the polyacrylamide sol obtained in the step B to stand and cool for 12 hours at room temperature in a closed container, so as to obtain the polyacrylamide hydrogel with the chemical structural formula described in the specification:
D. preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C at the temperature of minus 48 ℃ for 50 hours, placing the polyacrylamide hydrogel in a crucible, then placing the crucible in a tube furnace, heating to 790 ℃ at the heating rate of 5 ℃/min under the condition of nitrogen protection atmosphere, preserving heat for 1.8 hours at the temperature, cooling to room temperature, and grinding to the granularity of 100-200 meshes to obtain the polyacrylamide hydrogel wave-absorbing material.
The polyacrylamide hydrogel wave-absorbing material prepared in this example was examined in the same manner as in example 1, and the results are shown in FIG. 6. As can be seen from FIG. 6, the minimum reflection loss is-33 dB under the conditions of matching thickness of 2.0mm and frequency of 2-18GHz, and the effective bandwidth is 3.91GHz.
Example 5: the implementation steps of this example of the polyacrylamide hydrogel wave absorbing material of the present invention are as follows:
A. preparation of acrylamide mixture
Acrylamide monomer, 4-acryloylmorpholine, N-vinyl caprolactam, itaconic acid acrylic acid monomer, methacryloxyethyl trimethyl ammonium chloride acrylate monomer and N- (2, 3, 4-trihydroxy-5-acrylamide methylbenzyl) acrylamide derivative monomer with a capsaicin-containing functional structure are mixed according to a molar ratio of 200:10:8:37:3:0, adding deionized water, and performing ultrasonic dispersion for 24min under the condition of 40KHz by using a BRANSONIC ultrasonic cleaner to obtain an acrylamide mixed solution with the total monomer content of 19% by weight;
B. synthesis of sol
Adding an azodiisobutyronitrile initiator accounting for 1.2% of the total weight of the monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 1h under the protection of nitrogen at the temperature of 85 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
C. preparation of hydrogels
Allowing the polyacrylamide sol obtained in the step B to stand and cool for 12 hours at room temperature in a closed container, so as to obtain the polyacrylamide hydrogel with the chemical structural formula described in the specification:
D. preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C at the temperature of minus 52 ℃ for 52 hours, placing the polyacrylamide hydrogel in a crucible, then placing the crucible in a tube furnace, heating to 600 ℃ at the heating rate of 3 ℃/min under the condition of nitrogen protection atmosphere, preserving heat for 2.0 hours at the temperature, cooling to room temperature, and grinding to the granularity of 400-500 meshes to obtain the polyacrylamide hydrogel wave-absorbing material.
The polyacrylamide hydrogel wave-absorbing material prepared in this example was examined in the same manner as in example 1, and the results are shown in FIG. 7. As can be seen from FIG. 7, the minimum reflection loss is-35 dB under the conditions of matching thickness of 2.0mm and frequency of 2-18GHz, and the effective bandwidth is 3.73GHz.
Claims (10)
1. The preparation method of the polyacrylamide hydrogel wave-absorbing material is characterized by comprising the following preparation steps of:
A. preparation of acrylamide mixture
Acrylamide monomer, 4-acryloylmorpholine, N-vinylcaprolactam, acrylic acid monomer, acrylic ester monomer and acrylamide derivative monomer containing capsaicin functional structure according to the mole ratio of 200:0 to 10:0 to 15:0 to 50:0 to 5: mixing 0-1, adding deionized water, and performing ultrasonic dispersion to obtain an acrylamide mixed solution with the total monomer content of 5-25% by weight;
B. synthesis of sol
Adding an initiator accounting for 0.1-1.5% of the total weight of monomers into the acrylamide mixed solution obtained in the step A, transferring the monomer mixture containing the initiator into a three-neck flask, and then reacting for 1-6 hours under the protection of nitrogen at the temperature of 58-85 ℃ to obtain colorless, uniform and transparent polyacrylamide sol;
C. preparation of hydrogels
Letting the polyacrylamide sol obtained in the step B stand and cool for 12 hours at room temperature in a closed container, so as to obtain the polyacrylamide hydrogel with the following chemical structural formula:
wherein:
R 1 h, CH of a shape of H, CH 2 OH or (CH) 2 ) 2 OH；
R 2 Is OH, CH 3 、COOH、COOCH 3 Or (b)
R 3 H, CH of a shape of H, CH 2 COOH or
R 4 Is H or CH 3 ；
R 5 Is OCH 3 、OCH 2 (CH 2 ) 16 CH 3 、O(CH 2 ) 2 N(CH 3 ) 2 、O(CH 2 ) 2 OCOCH 2 COCH 3 、OCH 2 CH(CH 3 ) 2 、O(CH 2 ) 2 COOH、
D. Preparation of polyacrylamide hydrogel wave-absorbing material
And C, freeze-drying the polyacrylamide hydrogel obtained in the step C, placing the polyacrylamide hydrogel into a crucible, then placing the crucible into a tube furnace, heating to 600-1000 ℃ under the condition of nitrogen protection atmosphere, preserving heat for 1-2 h at the temperature, cooling to room temperature, and grinding to obtain the polyacrylamide hydrogel wave-absorbing material.
2. The process according to claim 2, wherein in step a, the acrylamide monomer is one or more acrylamide monomers selected from the group consisting of acrylamide, N-methylolacrylamide and N-hydroxyethyl acrylamide; the acrylic monomer is one or more acrylic monomers selected from acrylic acid, itaconic acid or 2-phenylchloroethyl acrylic acid; the acrylic ester monomer is one or more acrylic ester monomers selected from methyl methacrylate, octadecyl acrylate, dimethylaminoethyl methacrylate, acetoacetoxyethyl methacrylate, beta-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl methacrylate, cyclohexyl methacrylate or methacryloyloxyethyl trimethyl ammonium chloride; the capsaicin functional structural acrylamide derivative monomer is one or more selected from N- (2, 4-dimethyl-5-hydroxybenzyl) acrylamide, N- (2, 5-dimethyl-3-hydroxy-4-acrylamide methylbenzyl) acrylamide, N- (3, 5-dimethyl-4-hydroxybenzyl) acrylamide, N- (4, 5-dimethyl-2-hydroxy-3-acrylamide methylbenzyl) acrylamide, N- (4, 6-dimethyl-2-hydroxy-3-acrylamide methylbenzyl) acrylamide, N- (3-methyl-2, 5-dihydroxy-4, 6-diacrylamide methylbenzyl) acrylamide, N- (3, 4-dihydroxy-6-acrylamide methylbenzyl) acrylamide, N- (2, 5-dihydroxy-4-acrylamide methylbenzyl) acrylamide, N- (2, 4-dihydroxy-5-acrylamide methylbenzyl) acrylamide, N- (2, 6-trihydroxy-3, 5-dibenzyl) acrylamide, N- (2, 4-trihydroxy-5-hydroxybenzyl) acrylamide and N- (2, 4-trihydroxybenzyl) acrylamide Acrylamide derivative monomers of N- (2, 3, 4-trihydroxy-6-methoxycarbonylbenzyl) acrylamide, N- (2, 3, 4-trihydroxy-6-propoxycarbonylbenzyl) acrylamide, N- ((4-hydroxy-3-acrylamidomethyl naphthalene) methyl) acrylamide, N- ((2-hydroxynaphthalene) methyl) acrylamide, N- (3-methoxy-4-hydroxybenzyl) acrylamide, N- (1-methoxy-4-hydroxy-2-pyridazinyl) acrylamide, N- (2-hydroxy-3-carbamoylbenzyl) acrylamide, N- (2, 3-dihydroxy-6-aminoethyl-4, 5-diacrylamidomethyl) acrylamide hydrochloride.
3. The preparation method according to claim 1, wherein in the step A, ultrasonic dispersion is performed for 5 to 30 minutes under 40KHz using a BRANSONIC ultrasonic cleaner.
4. The process according to claim 1, wherein in step B, the initiator is one or more initiators selected from azobisisobutyronitrile, ammonium persulfate, potassium persulfate or 2, 2-azobis (2-methylpropionamide) dihydrochloride.
5. The method according to claim 1, wherein in the step B, the polyacrylamide sol is a solution containing a large amount of water at a temperature of 30 to 85 ℃ and having fluidity.
6. The process according to claim 1, wherein in step D, the freeze-drying is performed at a temperature of-45 to-55℃for 46 to 52 hours.
7. The preparation method according to claim 1, wherein in the step D, the mixture is heated to 700-900 ℃ at a heating rate of 2-5 ℃/min under the condition of a nitrogen protection atmosphere.
8. The preparation method according to claim 1, wherein in the step D, a natural agate mortar is used for grinding to a particle size of 100 to 500 mesh at room temperature.
9. The polyacrylamide hydrogel wave-absorbing material prepared by the preparation method according to any one of claims 1 to 8.
10. The polyacrylamide hydrogel wave-absorbing material according to claim 1, which is characterized in that the minimum reflection loss reaches-33 to-55 dB under the condition of matching the thickness of 2.0-5.0 mm and the frequency of 2-18GHz, and the effective absorption bandwidth is 3.7-5.3 GHZ.
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