Preparation method and application of self-adhesive porous polymer particles for electromagnetic wave absorption

Abstract

The invention discloses a preparation method of self-adhesive porous polymer particles for electromagnetic wave absorption, which comprises the following steps: dispersing a reaction solution of the self-adhesive porous polymer particles in a continuous phase medium through a dispersing agent to form reaction micro-droplets; freezing the reaction micro-droplets, initiating polymerization, and unfreezing after polymerization to obtain self-adhesive porous polymer particles for electromagnetic wave absorption; wherein the reaction solution of the self-adhesive porous polymer particles comprises a monomer, a cross-linking agent, an initiator, a solvent, a dispersing agent, a wave-absorbing filler and self-adhesive functional group molecules, and the self-adhesive functional group molecules are selected from one or more of hydrogen bonds, hydroxyl groups and amino groups; the freezing point of the continuous-phase medium is lower than that of the solvent. The prepared self-adhesive porous polymer particles can rapidly form a large-area wave-absorbing coating on the surface of an object, the pore diameter and porosity are continuously adjustable, the self-adhesive porous polymer particles can cope with electromagnetic waves of different frequencies, repair is convenient, and the self-adhesive porous polymer particles are green and environmentally friendly, and a new thought is provided for the field of electromagnetic wave absorption.

Description

Technical Field

[0001] This invention relates to the field of manufacturing porous polymer particles, and more specifically to a method for preparing and applying self-adhesive porous polymer particles for electromagnetic wave absorption. Background Technology

[0002] Since the beginning of the 21st century, with the continuous development of various information technologies following the information revolution, miniaturized or wearable electronic communication products for civilian use have emerged, meeting people's demands for intelligent information interaction and fast-paced lifestyles, thus making life more convenient. However, these electronic products, densely packed around us, emit electromagnetic waves during use, creating a complex electromagnetic environment. This phenomenon is considered a new type of environmental pollution. Excessive electromagnetic waves can not only affect the normal operation of precision electronic equipment but may also pose a threat to human health. To address this problem, researchers have explored and developed wave-absorbing materials, attempting to provide protection by absorbing external electromagnetic waves.

[0003] Currently, commonly used microwave absorbing materials dissipate electromagnetic waves primarily through dielectric loss and magnetic loss. Common materials that achieve absorption performance through dielectric loss include carbon materials such as carbon black, graphite, graphene, and carbon nanotubes, as well as other conductive materials such as silver, MXene, polyaniline, and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid. Materials that achieve absorption performance through magnetic loss mainly include magnetic iron, cobalt, nickel, and their compounds. To obtain good absorption performance, existing microwave absorbing coatings or structural components rely on high-content absorbing materials, resulting in high material density, thickness, and mass. Furthermore, when these materials are damaged and their performance degrades after prolonged use, repair is difficult.

[0004] To address the issues of thickness and mass in traditional microwave absorbing materials, porous materials can be used. Constructing a porous structure within a material is a common method to enhance its microwave absorption performance while reducing its mass. Porous materials can prolong the energy loss process of electromagnetic waves by allowing them to be reflected repeatedly after entering the pores, thus consuming more energy. They can also enhance interfacial polarization by utilizing their large specific surface area. Furthermore, the air within the pores can reduce the mass of the absorbing material and enhance its impedance matching characteristics. Ice templates are a special template-based pore-forming method that uses solvent crystallization as a pore-forming agent. This method allows for control over the pore shape and is simple and environmentally friendly. It also offers broad selectivity for pore-forming systems, not only preparing porous materials based on aqueous reaction solutions below the freezing point but also adapting to systems based on organic solvents. Cryoporation can be achieved by lowering the temperature below the freezing point of the corresponding solvent.

[0005] However, there are also challenges in preparing large-area, thin porous material coatings and fixing them onto the surface of the equipment to be protected. Traditional porous absorbing materials, such as composite aramid paper, do not have good adhesion themselves and require adhesives for fixation. Therefore, in addition to damage caused by the interaction between the coating surface and the external environment, adhesive failure can also lead to coating peeling.

[0006] Therefore, how to provide a solution that can simultaneously address the problems of coating preparation and repair is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] This invention provides a method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption. The prepared porous polymer particles can react with solvent on the surface of an object to quickly self-adhere to form a wave-absorbing coating, thereby achieving electromagnetic wave absorption performance and protecting the object. Furthermore, the pore size and porosity of the porous polymer particles are continuously adjustable, enabling absorption of electromagnetic waves in different frequency bands, and they are easy to repair.

[0008] A method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption, the method comprising the following steps: (1) The reaction solution of self-adhesive porous polymer particles is dispersed in a continuous phase medium by a dispersant to form reaction microdroplets; (2) Freeze the reaction microdroplets and initiate polymerization. After polymerization, thaw to obtain self-adhesive porous polymer particles that are oriented towards electromagnetic wave absorption. The reaction solution for the self-adhesive porous polymer particles includes monomers, crosslinking agents, initiators, solvents, dispersants, microwave absorbing fillers, and molecules containing self-adhesive functional groups, wherein the self-adhesive functional groups are selected from one or more of hydrogen bonds, hydroxyl groups, and amino groups; and the freezing point of the continuous phase medium is lower than that of the solvent.

[0009] The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption provided by this invention is based on the following principle: In terms of pore formation, the ice-template method utilizes solvent crystallization as a pore-forming template, which then initiates polymerization, causing a polymer network to form around the crystal. After crystallization and melting, the material will have a porous structure. For porous polymer particles oriented towards electromagnetic wave absorption, the pore-forming template is the solvent crystallization contained in the microdroplets of the reaction solution. Since the crystallization temperature of the solvent is higher than that of the continuous phase medium water, it can be ensured that the solvent crystallizes within the microdroplets at the reaction temperature, while the continuous phase medium water remains in a liquid state. The prepared porous polymer particles, in addition to the porous structure of the powder bulk, also have pores due to the stacking of the powder. These interconnected hierarchical pore structures enhance the reflection of electromagnetic waves within the macroscopic material, further extending the propagation distance of electromagnetic waves. Regarding self-adhesion capability, the essence of this capability is that the surface groups of the powder particles do not interact in the dry state, but when the solvent swells the particles, the surface groups are activated and generate interaction forces, causing the particles to adhere. Therefore, interacting molecules can be copolymerized into the material during the particle synthesis stage, endowing the particles with solvent-induced self-adhesion properties. Porous polymer microwave absorbing coatings can effectively protect objects, and self-adhesive particles can easily repair damaged coatings.

[0010] The monomer is selected from one or more of acrylate molecules with long alkyl chains in their skeleton, pentaerythritol tetra-3-mercaptopropionate, 1,6-hexanedithiol, or acrylamide. The crosslinking agent is selected from one or more of 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, or methylenebisacrylamide; The initiator is a thermal initiation system selected from benzoyl peroxide, azobisisobutyronitrile, or N,N-dimethylaniline, or a photoinitiation system selected from phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; The solvent contained in the reaction solution is selected from one of cyclohexane (freezing point: 6.5 ℃), n-hexadecane (freezing point: 18 ℃), or stearic acid (freezing point: 70 ℃); The microwave absorbing filler is selected from one or more of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), graphene, or nano-iron oxide particles.

[0011] In step (1), the self-adhesive functional group molecule is selected from one or more of dopamine, acrylate ureapyrimidine ketone or N-acryloylaminourea.

[0012] In step (1), the dispersant is selected from one or more of polyvinylpyrrolidone, carboxymethyl cellulose, or sodium polystyrene sulfonate.

[0013] In step (1), since the reaction solution is dispersed in a continuous phase medium to form reaction microdroplets, the continuous phase medium is an oleophobic solvent. More preferably, the freezing point of the oleophobic solvent is lower than that of the oily solvent, and it is not miscible with the oily solvent, so that the oily solvent forms microdroplets under the action of the dispersant.

[0014] Preferably, the continuous phase medium is water.

[0015] In this invention, the freezing point of water is lower than that of the solvent in the reaction solution, and water is not miscible with the solvent in the reaction solution. Under the action of the dispersant, the reaction solution can be dispersed in the continuous phase medium to form microdroplets.

[0016] In step (2), the freezing temperature is higher than the freezing point of the continuous phase medium and lower than the freezing point of the solvent in the reaction solution. The freezing temperature refers to the temperature at which the reaction solution crystallizes while the continuous phase medium does not crystallize, thereby achieving the freezing of microdroplets formed by the reaction solution while ensuring the continuous phase is frozen. Preferably, the freezing temperature is set between 1 ℃ and 70 ℃.

[0017] In step (2), the pore size and porosity of the obtained porous polymer particles can be adjusted by adjusting the freezing temperature; and the microwave absorption performance of the self-adhesive porous polymer particles can be adjusted by changing the pore size and porosity.

[0018] In step (2), the polymerization is carried out under freezing conditions when thermal initiation is used; and under freezing light conditions when photoinitiation is used. The wavelength of the light source used is in the range of 280 nm to 450 nm, and the irradiation time is controlled between 0.5 min and 24 h.

[0019] In step (2), the thawing method after polymerization is heating and melting or room temperature melting. Preferably, room temperature melting is used, and the time is controlled between 0.5 h and 4 h.

[0020] Step (2) also includes drying after thawing, which can be carried out by various methods such as natural air drying, oven drying, and freeze drying. Preferably, freeze drying is used. More preferably, the freeze drying temperature can be -80 to -50 ℃, and the time can be controlled between 12 h and 96 h.

[0021] The present invention also provides a self-adhesive porous polymer particle obtained by the above preparation method.

[0022] The present invention also provides an application of the above-mentioned self-adhesive porous polymer particles on a coating with electromagnetic wave absorption capability.

[0023] The prepared self-adhesive porous polymer particles bond together via a solvent-triggered process, forming a coating with electromagnetic wave absorption capabilities. The solvent can be liquid paraffin or silicone oil.

[0024] This invention employs a method that, based on the preparation of microdroplets through suspension polymerization, uses an ice-templating method to form a porous structure. The resulting porous microgel possesses excellent microwave absorption properties. Furthermore, by copolymerizing interacting molecules into the material, solvent-induced particle adhesion can be achieved. The porous polymer particles obtained by this method have continuously adjustable pore size and porosity, and can absorb electromagnetic waves upon contact with a solution through the interaction of their own channels and the channels created by stacking.

[0025] Compared with the prior art, the advantages of the present invention are as follows: (1) The preparation, use, and repair of electromagnetic wave absorbing materials are simplified. Traditional electromagnetic wave absorbing materials use composite aramid paper. In this invention, the microwave absorbing coating formed by the self-adhesion of porous polymer particles can spontaneously form only when in contact with the solution, making the process simple and quick; (2) The self-adhesive porous polymer particles for electromagnetic wave absorption prepared by the present invention extend the propagation distance of electromagnetic waves inside the coating by introducing a multi-level porous structure; and introduce wave-absorbing fillers with conductivity, polarization ability and magnetism to enhance the loss of electromagnetic waves and realize electromagnetic wave absorption.

[0026] (3) In principle, the size of the oily solvent freeze crystals can be controlled by adjusting the freezing temperature of the reaction system during suspension polymerization, and the pore size and porosity of the porous polymer particles can be continuously adjusted to absorb electromagnetic waves of different frequencies. (4) After the material is damaged during long-term use, it can be repaired by allowing the porous polymer particles to react with the solution at the damaged location to self-adhere the particles to the original coating, so that the coating can be restored to its original state and have a wave absorption capacity close to the original state.

[0027] The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption provided by this invention offers a simple method for preparing large-area microwave absorbing coatings, which is convenient for repair, environmentally friendly, and provides a new approach to the field of microwave absorbing coatings. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the principle of the porous microwave absorbing microgel powder preparation method of the present invention; Figure 2 This is a schematic diagram illustrating the pore morphology control of the porous microgel powder obtained in this invention. Figure 3 This is a schematic diagram of the bonding mechanism of the porous microgel powder obtained in this invention; Figure 4 This is a schematic diagram of the electromagnetic wave absorption mechanism of the self-adhesive porous microgel material prepared in this invention. Figure 5Microscopic image of the porous structure of the self-adhesive porous microgel powder obtained in Example 1 of this invention; Figure 6 Microscopic image of the porous structure of the self-adhesive porous microgel powder obtained in Example 10 of this invention; Figure 7 This is a macroscopic view of the self-adhesive porous microgel powder bonding obtained in Example 1 of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0030] like Figures 1-3 As shown, the key to the preparation method of self-adhesive porous polymer particles for electromagnetic wave absorption provided by this invention lies in the formation of a porous structure from dry powder and the introduction of self-adhesive molecules. As the basic principle states, the formed porous structure originates from the freeze-crystallization of the solvent in the reaction solution at low temperature, and the self-adhesive molecules can be added to the reaction solution for gel synthesis. Under initiation-induced polymerization, freeze-polymerization will occur independently within each micro-droplet, and a polymer network will form around the crystals. After the reaction is complete, the porous microparticles can be obtained by melting the oil solvent at room temperature. During the process, it is necessary to ensure that the water, as the dispersed phase, does not freeze at low temperature, allowing the system to be continuously stirred to complete the suspension polymerization. Solvent-induced self-adhesion of the porous microparticles can be achieved by adding molecules containing different functional groups to the polymerization reaction solution.

[0031] like Figure 4 As shown, the self-adhesive porous microgel material provided by the present invention mainly absorbs electromagnetic waves through dielectric loss. Its porous structure further extends the propagation path of electromagnetic waves and enhances the energy loss of electromagnetic waves when passing through the material.

[0032] Example 1 (Hydroxy group) Step 1: Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of 1,6-hexanediol diacrylate and 0.04 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in n-hexadecane (freezing point: 18 °C) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, and place in a 10 ℃ low temperature water bath for stirring. Hexadecane crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: The pore structure of the obtained porous polymer particles is characterized using an electron microscope; Step 5: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0033] The microscopic image of the porous structure of the self-adhesive porous microgel powder obtained in this embodiment is shown below. Figure 5 As shown, a micron-scale porous structure exists; the macroscopic image of the resulting self-adhesive porous microgel powder bonding is shown below. Figure 7 As shown, the glass microgel powder self-adhedes to form a thin film on the glass after contacting silicone oil.

[0034] Example 2 (Hydrogen Bonds) Step 1: Dissolve 2 g pentaerythritol tetra-3-mercaptopropionate, 0.5 g acrylate ureidopyrimidinone, 0.2 g 1,6-hexanediol diacrylate and 0.04 g phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in 10 g n-hexadecane (freezing point: 18 ℃) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, and place in a 10 ℃ low temperature water bath for stirring. Hexadecane crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0035] Example 3 (Amino) Step 1: Dissolve 1.5 g acrylamide, 0.5 g N-acryloylaminourea, 0.2 g 1,6-hexanediol diacrylate and 0.04 g phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in 10 g n-hexadecane (freezing point: 18 ℃) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, and place in a 10 ℃ low temperature water bath for stirring. Hexadecane crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0036] Example 4 (using polyethylene glycol diacrylate crosslinking agent) Step 1: Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of polyethylene glycol diacrylate and 0.04 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in 10 g of n-hexadecane (freezing point: 18 °C) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, and place in a 10 ℃ low temperature water bath for stirring. Hexadecane crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0037] Example 5 (benzoyl peroxide initiation system) Step 1: Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of 1,6-hexanediol diacrylate and 0.05 g of benzoyl peroxide in 10 g of n-hexadecane (freezing point: 18 ℃) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, and place in a 10 ℃ low temperature water bath for stirring. Hexadecane crystals will appear, forming a suspension. Step 3: The above suspension was reacted at 10 °C for 24 h. After the reaction, the gel was thawed and the porous microgel and water were separated by centrifugation. The porous microgel was then freeze-dried to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0038] Example 6 (Cyclohexane as solvent) Step 1: Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of 1,6-hexanediol diacrylate and 0.04 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in 10 g of cyclohexane (freezing point: 6.5 ℃) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, place in a 2 ℃ low temperature water bath and stir. Cyclohexane crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0039] Example 7 (using stearic acid as solvent) Step 1: Melt 10 g of stearic acid (freezing point: 70 ℃) at 80 ℃. Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of 1,6-hexanediol diacrylate and 0.04 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide into the melted stearic acid and stir until completely dissolved. Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, and place in a 25 ℃ low temperature water bath for stirring. Stearic acid crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 h. After that, thaw the gel at 80 °C, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0040] Example 8 (Nano-Fe3O4 particles as microwave absorbing filler) Step 1: Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of 1,6-hexanediol diacrylate and 0.05 g of benzoyl peroxide in 10 g of n-hexadecane (freezing point: 18 ℃) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of nano-iron oxide particles to the above mixture, then pour it into 50 g of deionized water, place it in a 10 ℃ low temperature water bath and stir. Hexadecane crystals will appear to form a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0041] Example 9 (using polyvinylpyrrolidone as a dispersant) Step 1: Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of 1,6-hexanediol diacrylate and 0.05 g of benzoyl peroxide in 10 g of n-hexadecane (freezing point: 18 ℃) and stir until completely dissolved; Step 2: Add 0.5 g of polyvinylpyrrolidone and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, place in a 10 ℃ low temperature water bath and stir. Hexadecane crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles. Step 4: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0042] Example 10 (Temperature Control Hole Structure) Step 1: Dissolve 2 g of 1,6-hexanedithiol, 0.5 g of dopamine, 0.2 g of 1,6-hexanediol diacrylate and 0.05 g of benzoyl peroxide in 10 g of n-hexadecane (freezing point: 18 ℃) and stir until completely dissolved; Step 2: Add 0.5 g of hydroxymethyl cellulose and 0.5 g of graphene to the above mixture, then pour in 50 g of deionized water, place in a 0 ℃ ice-water mixture water bath and stir. Hexadecane crystals will appear, forming a suspension. Step 3: Irradiate the above suspension under ultraviolet light for 1 hour. After the irradiation, thaw the gel, separate the porous microgel and water by centrifugation, and freeze-dry the porous microgel to obtain porous polymer particles; Step 4: Characterize the pore structure of the obtained porous polymer particles using an electron microscope; Step 5: Take a unit mass of self-adhesive porous dry gel powder and immerse it in silicone oil. Observe and record the self-adhesion of the microgel and measure the microwave absorption performance of the macrogel.

[0043] The microscopic image of the porous structure of the self-adhesive porous microgel powder prepared in this embodiment is shown below. Figure 6 As shown, from Figure 6 It can be seen that the size of the porous structure decreases after the freezing temperature is reduced, and it is feasible to control the size of the pore structure by controlling the freezing temperature.

[0044] Example 11 (Wave Absorbing Powder Coating) The self-adhesive gel obtained in Example 1 was coated onto the surface of a glass slide and self-adheded under the triggering of silicone oil, forming a microwave absorbing coating on the glass surface. At the same time, the microwave absorption performance was tested.

[0045] Table 1. Wave absorption properties of the synthesized porous polymer particles obtained in Examples 1-11 after self-adhesion. In summary, this invention utilizes an ice-templating method to induce pores, adding interacting molecules to the reaction solution to prepare self-adhesive porous particles. These particles react with the solvent on the surface of the object to be protected, forming a large-area coating. To further enhance the microwave absorption performance of the coating, polar molecules or microwave-absorbing materials can be dispersed in the solvent. The self-adhesive polymer particles prepared by this invention are uniformly dispersed on the surface of the object to be protected. A sufficient amount of solution is required to form a relatively uniform microwave-absorbing coating on the object's surface. Furthermore, if the coating is damaged, its self-adhesive ability allows for repair using only the polymer particles and solution.

Claims

1. A method for preparing self-adhesive porous polymer particles oriented towards electromagnetic wave absorption, characterized in that, The preparation method includes the following steps: (1) The reaction solution of self-adhesive porous polymer particles is dispersed in a continuous phase medium through a dispersant to form reaction microdroplets; (2) Freeze the reaction microdroplets and initiate polymerization. After polymerization, thaw to obtain self-adhesive porous polymer particles that are oriented towards electromagnetic wave absorption. The reaction solution for the self-adhesive porous polymer particles includes monomers, crosslinking agents, initiators, solvents, dispersants, microwave absorbing fillers, and molecules containing self-adhesive functional groups, wherein the self-adhesive functional groups are selected from one or more of hydrogen bonds, hydroxyl groups, and amino groups; and the freezing point of the continuous phase medium is lower than that of the solvent.

2. The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption according to claim 1, characterized in that, The monomer is selected from one or more of acrylate molecules with long alkyl chains in their skeleton, pentaerythritol tetra-3-mercaptopropionate, 1,6-hexanedithiol, or acrylamide. The crosslinking agent is selected from one or more of 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, or methylenebisacrylamide; The initiator is a thermal initiation system selected from benzoyl peroxide, azobisisobutyronitrile, or N,N-dimethylaniline, or a photoinitiation system selected from phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; The solvent contained in the reaction solution is selected from one of cyclohexane, n-hexadecane, or stearic acid; The microwave absorbing filler is selected from one or more of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), graphene, or nano-iron oxide particles.

3. The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption according to claim 1, characterized in that, In step (1), the self-adhesive functional group molecule is selected from one or more of dopamine, acrylate ureapyrimidine ketone or N-acryloylaminourea.

4. The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption according to claim 1, characterized in that, In step (1), the dispersant is selected from one or more of polyvinylpyrrolidone, carboxymethyl cellulose, or sodium polystyrene sulfonate.

5. The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption according to claim 1, characterized in that, In step (1), the continuous phase medium is water.

6. The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption according to claim 1, characterized in that, In step (2), the freezing temperature is greater than the freezing point of the continuous phase medium and less than the freezing point of the solvent in the reaction solution.

7. The method for preparing self-adhesive porous polymer particles for electromagnetic wave absorption according to claim 1, characterized in that, In step (2), the polymerization is carried out under freezing conditions when thermal initiation is used, and under freezing light conditions when photoinitiation is used, with the wavelength of the light source being in the range of 280 nm to 450 nm.

8. A self-adhesive porous polymer particle obtained by the preparation method according to any one of claims 1-7.

9. The application of the self-adhesive porous polymer particles of claim 8 on a coating with electromagnetic wave absorption capability, characterized in that, The prepared self-adhesive porous polymer particles bond together through solvent-triggered bonding to form a coating with electromagnetic wave absorption capabilities.

10. The application according to claim 9, characterized in that, The solvent is selected from liquid paraffin and silicone oil.

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