A MOF-74 derivative polymer composite gel and a preparation method thereof

Abstract

The application discloses a MOF-74 derivative polymer composite gel and a preparation method thereof, and belongs to the technical field of preparation of heat-conducting and microwave-absorbing composite materials and electronic packaging. A MOF-74 precursor is synthesized by a hydrothermal method, and then is calcined to obtain a carbon material loaded with magnetic nanoparticles, which is added into a solution of an organic gel precursor with water and glycerol as a matrix to be in-situ polymerized under magnetic field induction to obtain a final product. Water and glycerol in a polyacrylamide (PAM) matrix provide dipole polarization, MOF-74 derivatives enhance the interface polarization and conductive loss of the system, and simultaneously serve as ordered heat-conducting fillers to enhance the vertical heat-conducting capacity, so that the two functions of electromagnetic wave absorption and heat conduction are combined. The application has novel ideas, simple methods, and the product has the dual functions of efficient electromagnetic wave absorption and heat conduction, excellent performance, and remarkable economic and social benefits.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of heat-conducting and microwave-absorbing composite materials and electronic packaging, and particularly relates to a MOF-74 derivative polymer composite gel and a preparation method thereof. BACKGROUND

[0002] High-power, high-density and high-integration electronic devices inevitably generate serious electromagnetic interference and heat accumulation. Simultaneously adding a wave-absorbing layer and a heat-conducting layer between a high-power electronic device and a heat sink is a promising method to improve electromagnetic absorption and heat dissipation performance. However, the presence of the wave-absorbing layer will reduce the heat transfer, and if the heat generated by electromagnetic loss cannot be diffused in time, the absorption performance will be reduced. Developing a dual-functional material with high electromagnetic wave absorption efficiency and good heat conduction to achieve excellent packaging of the device is an effective strategy to solve this problem.

[0003] Group VIII element metals are common absorbing fillers, and their absorption of electromagnetic waves mainly comes from natural ferromagnetic resonance, eddy current loss and exchange resonance. Metal-organic frameworks (MOFs) as a new type of inorganic-organic hybrid material with a periodic network structure have been proved to be an ideal precursor for synthesizing highly dispersed metal / metal oxide composites due to their highly ordered structure, porosity and adjustable topological structure. However, pure MOFs derivatives as electromagnetic wave absorbers may have a large number of air gaps at the contact interface of electronic devices, leading to heat accumulation and reducing the wave-absorbing performance. It is of great significance to obtain a high electromagnetic wave absorption rate without reducing or even improving the thermal conductivity.

[0004] Polymer gels and their composites have attracted extensive attention due to their light weight, easy processing, good elasticity and good chemical stability. However, due to the irregular entanglement of molecular chains and the scattering effect of phonons by chain vibration, the thermal conductivity of polymer gels is relatively poor, generally less than 0.3 W·m -1 ·K -1 . In order to improve the thermal conductivity of polymer gels, various attempts have been made to create additional heat conduction pathways by adding high-thermal-conductivity components such as metals, electrically insulating ceramics and carbon materials. By combining MOFs derivatives with polymer gels, the composite material has good elasticity and is expected to fill the air gaps at the contact interface of electronic devices to reduce the contact thermal resistance. SUMMARY

[0005] The purpose of the present application is to provide a high-efficiency electromagnetic wave-absorbing and heat-conducting dual-functional MOF-74 derivative polymer composite gel and a preparation method thereof, aiming to solve the problems of electromagnetic interference and heat accumulation during the operation of electronic devices.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] Co-MOF-74 is synthesized by a hydrothermal method, and then a MOF-74 derivative is obtained by calcination. The obtained MOF-74 derivative is added to an organic gel precursor solution, and the organic gel is prepared with water and glycerol as the matrix and tetramethyl ethylenediamine as the catalyst. Primary free radicals are generated after the decomposition of the initiator potassium persulfate, and then the monomer radicals are generated by the addition of acrylamide monomers, so as to initiate the polymerization of other monomers into chains and chemically crosslink with the crosslinking agent N, N-methylene bisacrylamide, and finally the composite gel is obtained. The method comprises the following steps:

[0008] (1) 10-30 parts of N, N-dimethylformamide, 10-30 parts of ethanol and 10-30 parts of deionized water are weighed according to the mass fraction, mixed uniformly, 1-5 parts of 2, 5-dihydroxyterephthalic acid and 5-10 parts of cobalt nitrate hexahydrate are added, ultrasonic treatment for 10 min, mixed uniformly, 120-150℃ reaction for 12-24 h, cooling to room temperature, centrifugation, washing with N, N-dimethylformamide and methanol respectively, vacuum activation at 120℃ for 3-5 h, and Co-MOF-74 is obtained;

[0009] (2) Co-MOF-74 is heated to 500-900℃ at a heating rate of 2℃ / min under N2 atmosphere, and calcined for 3-5 h to obtain a MOF-74 derivative;

[0010] (3) The water and the organic solvent are mixed, and a mixed solution of acrylamide, N, N-methylene bisacrylamide and potassium persulfate is added, and shaken for 10-30 min to mix uniformly; the MOF-74 derivative and tetramethyl ethylenediamine are added and mixed uniformly, and in-situ polymerization is carried out under the action of a magnetic field to obtain the MOF-74 derivative polymer composite gel PAM-x, wherein x represents the mass ratio of MOF-74 derivative to acrylamide.

[0011] Further, in step (3), the organic solvent is glycerol; the mass ratio of the organic solvent to the mixed solution is 40-80:100; the mass ratio of N, N-methylene bisacrylamide to acrylamide is 0.2-1:100; the mass ratio of potassium persulfate to acrylamide is 0.2-1:100; the mass ratio of MOF-74 derivative to acrylamide is 0.1-20:100; and the mass ratio of tetramethyl ethylenediamine to MOF-74 derivative is 4-15:100.

[0012] The prepared MOF-74 derivative / PAM organic gel selects an organic gel containing water and glycerol as a binary solvent as a matrix to improve the loss of dipole polarization and conduction loss. The Co-MOF-74 calcined derivative is added to the gel, and is arranged in a magnetic field to form a combination of magnetic coupling and conduction network, so that the obtained material exhibits better electromagnetic response and multiple attenuation mechanisms. The magnetic nanoparticles in the MOF derivative help the filler in the polymer matrix to be arranged under the influence of the magnetic field, so that a more ordered heat conduction path is created, the heat conduction in the direction perpendicular to the plane is improved, and heat accumulation is reduced. The present study proposes a new method for developing multifunctional materials with microwave absorption and heat conduction.

[0013] The present application has the following beneficial effects:

[0014] (1) The MOF-74 is synthesized by using a high-efficiency and convenient hydrothermal method, and then a one-pot method is used to synthesize the final composite gel after simple calcination, so that the preparation method is simple.

[0015] (2) The MOF derivative and the organic gel are combined, the obtained material has multiple microwave attenuation mechanisms and an ordered heat conduction path, and can effectively avoid electromagnetic interference and heat accumulation.

[0016] (3) The MOF derivative / polyacrylamide is applied to the fields of heat conduction and microwave absorption, which breaks through the limitation of traditional powder MOF derivative wave-absorbing materials, the obtained material has a smooth surface, good elasticity and flexibility, and reduces the contact thermal resistance in the application process. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the (a) real part, (b) imaginary part, (c) loss tangent tanδ and (d) conduction loss and polarization loss diagram of the complex permittivity of the PAM-x organic gel of the present application. ε

[0018] Figure 2 is the (a) real part, (b) imaginary part, (c) loss tangent tanδ and (d) Co diagram of the complex permeability of the PAM-x organic gel of the present application. μ

[0019] Figure 3 is the microwave absorption property (a) three-dimensional diagram, (b) two-dimensional contour diagram, (c) impedance matching coefficient |Z / Z0| at the minimum reflection loss and (d) attenuation constant a of the PAM-x organic gel of the present application. in

[0020] Figure 4 is the (a) thermal conductivity, (b) surface temperature in the heating and cooling processes, (c) infrared thermal imaging diagram in the heating and cooling processes of the PAM-x organic gel of the present application.​​​ Detailed Implementation

[0021] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0022] Example 1

[0023] Add 1 g acrylamide, 2 mg N,N-methylenebisacrylamide, 2 mg potassium persulfate, 0.5 mL deionized water, and 1 mL glycerol to a centrifuge tube, and shake for 10 min to mix thoroughly. Add 0.5 μL tetramethylethylenediamine, transfer the mixture to a mold, and polymerize in situ to obtain PAM.

[0024] Example 2

[0025] Measure 20 mL of N,N-dimethylformamide, 20 mL of ethanol, and 20 mL of deionized water into a beaker. Weigh 0.202 g of 2,5-dihydroxyterephthalic acid and 0.882 g of cobalt nitrate hexahydrate and add them to the solution. Sonicate for 10 min, then stir until homogeneous. Transfer the solution to a 100 mL hydrothermal reactor and heat to 120 °C in an oven for 24 h. After the product cools to room temperature, collect the precipitate using a centrifuge and wash three times with DMF and methanol, respectively. Activate the obtained solid in a vacuum oven at 120 °C for 5 h to obtain Co-MOF-74. Place the obtained Co-MOF-74 into a crucible and calcine at 500 °C for 3 h under a N2 atmosphere at a heating rate of 2 °C / min to obtain Co-CoO-C. Add 1 g acrylamide, 2 mg N,N-methylenebisacrylamide, 2 mg potassium persulfate, 0.5 mL deionized water, and 1 mL glycerol to a centrifuge tube, and shake for 10 min to mix thoroughly. Add 25 mg Co-CoO-C and 1 μL tetramethylethylenediamine, transfer the mixture to a mold, and perform in-situ polymerization under a magnetic field to obtain PAM-2.5.

[0026] Example 3

[0027] Take 20 mL N,N-dimethylformamide, 20 mL ethanol and 20 mL deionized water into a beaker, take 0.202 g 2,5-dihydroxyterephthalic acid, 0.882 g cobalt nitrate hexahydrate into the solution, ultrasonic for 10 min, then stir uniformly; the solution is transferred to a 100 mL hydrothermal kettle, heated to 120°C in an oven for 24 h. After the product is cooled to room temperature, the precipitate is collected by centrifuge, washed with DMF and methanol for 3 times respectively. The obtained solid is activated in a vacuum oven at 120°C for 5 h to obtain Co-MOF-74, and the obtained Co-MOF-74 is loaded into a crucible, heated to 500°C at a heating rate of 2°C / min under N2 atmosphere for 3 h to obtain Co-CoO-C. Add 1 g acrylamide, 2 mg N,N-methylenebisacrylamide, 2 mg potassium persulfate, 0.5 mL deionized water and 1 mL glycerol into a centrifuge tube, shake for 10 min to mix uniformly. Add 50 mg of Co-CoO-C, 1.5 μL of tetramethyl ethylenediamine, and transfer the mixed solution into a mold to perform in-situ polymerization under the action of a magnetic field to obtain PAM-5.

[0028] Example 4

[0029] Take 20 mL N,N-dimethylformamide, 20 mL ethanol and 20 mL deionized water into a beaker, take 0.202 g 2,5-dihydroxyterephthalic acid, 0.882 g cobalt nitrate hexahydrate into the solution, ultrasonic for 10 min, then stir uniformly; the solution is transferred to a 100 mL hydrothermal kettle, heated to 120°C in an oven for 24 h. After the product is cooled to room temperature, the precipitate is collected by centrifuge, washed with DMF and methanol for 3 times respectively. The obtained solid is activated in a vacuum oven at 120°C for 5 h to obtain Co-MOF-74, and the obtained Co-MOF-74 is loaded into a crucible, heated to 500°C at a heating rate of 2°C / min under N2 atmosphere for 3 h to obtain Co-CoO-C. Add 1 g acrylamide, 2 mg N,N-methylenebisacrylamide, 2 mg potassium persulfate, 0.5 mL deionized water and 1 mL glycerol into a centrifuge tube, shake for 10 min to mix uniformly. Add 75 mg of Co-CoO-C, 2 μL of tetramethyl ethylenediamine, and transfer the mixed solution into a mold to perform in-situ polymerization under the action of a magnetic field to obtain PAM-7.5.

[0030] Example 5

[0031] Into a beaker, 20 mL of N,N-dimethylformamide, 20 mL of ethanol and 20 mL of deionized water were measured, 0.202 g of 2,5-dihydroxyterephthalic acid, 0.882 g of cobalt nitrate hexahydrate were weighed into the solution, ultrasonic for 10 min, then stirred uniformly; the solution was transferred into a 100 mL hydrothermal kettle, heated to 120℃ in an oven for 24 h. After the product was cooled to room temperature, the precipitate was collected by centrifuge and washed with DMF and methanol for 3 times respectively. The obtained solid was activated in a vacuum oven at 120℃ for 5 h to obtain Co-MOF-74, and the obtained Co-MOF-74 was loaded into a crucible and heated to 500℃ at a heating rate of 2℃ / min under N2 atmosphere for 3 h to obtain Co-CoO-C. Into a centrifuge tube, 1 g of acrylamide, 2 mg of N,N-methylenebisacrylamide, 2 mg of potassium persulfate, 0.5 mL of deionized water and 1 mL of glycerol were added, and shaken for 10 min to mix uniformly. 100 mg of Co-CoO-C and 5 μL of tetramethyl ethylenediamine were added, and the mixed solution was transferred into a mold to perform in-situ polymerization under the action of a magnetic field to obtain PAM-10.

[0032] Figure 1 The dielectric ability of PAM-x organic gel was demonstrated, and the polarization loss of PAM-2.5 and PAM-5 was the strongest, and the polarization loss ability of the composite material decreased with the further increase of the filler load.

[0033] Figure 2 The magnetic guide ability of PAM-x organic gel was demonstrated, and PAM-5 had the strongest magnetic loss than other samples.

[0034] Figure 3 It was demonstrated that PAM-5 had a minimum reflection loss of -51.6 dB at a thickness of 2.3 mm and a frequency of 13.2 GHz, and the maximum effective absorption bandwidth was 5.73 GHz, indicating that PAM-5 had excellent microwave absorption performance. The synthesized PAM-x organic gel had good impedance matching and microwave attenuation ability at a proper frequency, which was an important condition for excellent microwave absorption performance.

[0035]

[0036] As can be seen from Table 1, the PAM-x organic gel obtained by the present application has excellent microwave absorption performance.

[0037] Figure 4 The thermal conductivity of PAM-x organic gel in the plane direction and perpendicular to the plane direction was demonstrated, and the thermal conductivity perpendicular to the plane direction gradually increased with the increase of the amount of filler, and the time required for PAM-x to reach steady state during the heating and cooling processes was shorter than that of pure PAM, indicating that PAM-x had excellent thermal management performance.

[0038] The above description is only the preferred embodiment of the present application, and any equivalent change and modification made according to the scope of the present application should be included in the scope of the present application.

Claims

1. A method for preparing a MOF-74 derivative macromolecular composite gel, characterized in that: The method comprises the following steps: (1) 10-30 parts of N, N-dimethylformamide, ethanol and deionized water are weighed by mass fraction, mixed uniformly, 1-5 parts of 2, 5-dihydroxyterephthalic acid and 5-10 parts of cobalt nitrate hexahydrate are added, ultrasonic is performed for 10 min, mixed uniformly, reaction is performed at 120-150℃ for 12-24 h, cooled to room temperature, centrifuged, washed with N, N-dimethylformamide and methanol respectively, vacuum activated at 120℃ for 3-5 h, and Co-MOF-74 is obtained; (2) the Co-MOF-74 is heated to 500-900℃ at a heating rate of 2℃ / min under N2 atmosphere, calcined for 3-5 h, and MOF-74 derivative is obtained; (3) water and an organic solvent are mixed, a mixed solution of acrylamide, N, N-methylene bisacrylamide and potassium persulfate is added, shaken for 10-30 min, mixed uniformly, MOF-74 derivative and tetramethyl ethylenediamine are added, mixed uniformly, in-situ polymerization is performed under the action of a magnetic field, and the MOF-74 derivative polymer composite gel is obtained.

2. The method of claim 1, wherein: The organic solvent in step (3) is glycerol.

3. The method of claim 1, wherein: The mass ratio of the organic solvent to the mixed solution in step (3) is 40-80:

100.

4. The method of claim 1, wherein: The mass ratio of N, N-methylene bisacrylamide to acrylamide in step (3) is 0.2-1:

100.

5. The method of claim 1, wherein: The mass ratio of potassium persulfate to acrylamide in step (3) is 0.2-1:

100.

6. The method of claim 1, wherein: The mass ratio of MOF-74 derivative to acrylamide in step (3) is 0.1-20:

100.

7. The method of claim 1, wherein: The mass ratio of tetramethyl ethylenediamine to MOF-74 derivative in step (3) is 4-15:

100.

8. A MOF-74 derivative polymer composite gel prepared by the method in any one of claims 1-7.

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