A polymer electromagnetic shielding material based on high birefringence liquid crystal and a preparation method thereof

Abstract

The application discloses a polymer electromagnetic shielding material based on high-birefringence liquid crystal and a preparation method thereof. The polymer electromagnetic shielding material is prepared by adding high-birefringence liquid crystal material into a prepared electromagnetic shielding matrix material. The high-birefringence liquid crystal material and polyvinyl alcohol compound are used as the matrix, the high dielectric anisotropy of the high-birefringence liquid crystal material can effectively improve the dielectric property of the matrix. Meanwhile, the liquid crystal material has good orientation performance, so that the crystal molecules in the matrix form an ordered arrangement, and the dielectric property of the matrix is further improved. The high-birefringence liquid crystal material and polyvinyl alcohol compound are used as the matrix, so that the electromagnetic shielding property of the material can be effectively improved. The preparation method is simple, the preparation condition is mild, no three wastes are discharged in the preparation process, and the method meets the demand of modern chemical production.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding, specifically to a polymer electromagnetic shielding material based on high birefringence liquid crystal and its preparation method. Background Technology

[0002] The miniaturization of modern electronic devices and circuits has led to rapid technological advancements in electronic systems. These miniaturized devices generate unwanted electromagnetic interference, which can adversely affect the performance of electronic systems. Prolonged exposure to electromagnetic radiation has harmful effects on human health, causing nausea, headaches, eye problems, cancer, and adverse effects on infant brain development. In particular, some medical implants or devices are prone to malfunction in alternating electromagnetic fields. Therefore, electromagnetic shielding materials that effectively shield electromagnetic waves have become a hot research topic.

[0003] In the field of electromagnetic shielding materials, conductive polymers based on organic polymers have attracted widespread attention due to their low density, good flexibility, ease of processing, and low cost. Currently, electromagnetic shielding materials using organic polymers typically use polyvinyl alcohol as the matrix. However, due to its poor dielectric properties, even with the addition of magnetic materials as electromagnetic wave absorbers, satisfactory results cannot be achieved. Summary of the Invention

[0004] The purpose of this invention is to provide a polymer electromagnetic shielding material based on high birefringence liquid crystal and its preparation method. The electromagnetic shielding matrix material is prepared by adding high birefringence liquid crystal material to improve the dielectric properties of the material and obtain better electromagnetic shielding performance.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A polymer electromagnetic shielding material based on high birefringence liquid crystal is obtained by adding high birefringence liquid crystal material to the prepared electromagnetic shielding matrix material.

[0007] The structural formula of the high birefringence liquid crystal molecule is as follows:

[0008]

[0009] Where: R is a C1-C7 straight-chain saturated alkyl group; a represents the number of benzene rings, which is any integer from 1 to 4; b represents the amount of water in the triple bond, which is any integer from 1 to 3; c represents the number of benzene rings, which is any integer from 1 to 4.

[0010] The preparation method of polymer electromagnetic shielding material based on high birefringence liquid crystal includes the following steps:

[0011] First, weigh 6-9g of polyvinyl alcohol into a beaker and add 48-72mL of distilled water. Soak at room temperature for 8 hours, then place it in a three-necked flask and heat it in a constant temperature water bath to 90℃ while stirring continuously to obtain a polyvinyl alcohol solution.

[0012] The second step is to weigh 3-5g of multi-walled carbon nanotubes and grind them in an agate mortar for 10-20 minutes.

[0013] The third step involves weighing 0.5-2g of ground multi-walled carbon nanotubes, placing them in 25-45mL of distilled water, sonicating for 5-10 minutes, slowly adding them to the polyvinyl alcohol solution from the first step using a dropper, and continuing to heat for 30-50 minutes. After ultrasonic dispersion, a thin film is prepared using a solvent-based film-forming method.

[0014] The fourth step involves rubbing the film obtained in the third step in a certain direction using a friction cloth to form grooves with consistent orientation on the film surface. Then, 1-3g of high birefringence liquid crystal is dropped onto the film, and the liquid crystal molecules are arranged uniformly on the oriented film. Finally, another film obtained in the third step is laid on the upper surface to obtain a polymer electromagnetic shielding material based on high birefringence liquid crystal.

[0015] The present invention has the following advantages:

[0016] By incorporating high birefringence liquid crystal material into the prepared electromagnetic shielding matrix material, the ordered arrangement formed by the good orientation properties of liquid crystal molecules and the high dielectric anisotropy of the long π-electron conjugated system of high birefringence liquid crystal are utilized to improve the dielectric properties of the material, thereby obtaining better electromagnetic shielding performance.

[0017] In this invention, the diphenylacetylene groups in the molecular structure of the high birefringence liquid crystal material provide a long π-electron conjugation system, effectively improving the dielectric properties of the liquid crystal material. Using the composite of the high birefringence liquid crystal material and polyvinyl alcohol as the matrix, the high dielectric anisotropy of the high birefringence liquid crystal material effectively enhances the dielectric properties of the matrix. Simultaneously, the excellent orientation properties of the liquid crystal material allow for an ordered arrangement of crystal molecules in the matrix, further increasing the dielectric properties of the matrix. Based on these two reasons, using the composite of the high birefringence liquid crystal material and polyvinyl alcohol as the matrix effectively improves the electromagnetic shielding performance of the material.

[0018] The preparation method of this invention is simple and mild, and there is no waste discharge during the preparation process, which meets the needs of modern chemical production. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0020] This invention relates to a polymer electromagnetic shielding material based on high birefringence liquid crystal. The polymer electromagnetic shielding material is obtained by adding a high birefringence liquid crystal material to a prepared electromagnetic shielding matrix material. The structural formula of the high birefringence liquid crystal molecule is as follows:

[0021]

[0022] Where: R is a C1-C7 straight-chain saturated alkyl group; a represents the number of benzene rings, which is any integer from 1 to 4; b represents the amount of water in the triple bond, which is any integer from 1 to 3; c represents the number of benzene rings, which is any integer from 1 to 4.

[0023] Example 1

[0024] A method for preparing a polymer electromagnetic shielding material based on high birefringence liquid crystal includes the following steps:

[0025] First, weigh 6g of polyvinyl alcohol and pour it into a beaker, add 48mL of distilled water, soak at room temperature for 8 hours, then put it into a three-necked flask and heat it in a constant temperature water bath at 90℃ with constant stirring.

[0026] The second step is to weigh 3g of multi-walled carbon nanotubes and grind them in an agate mortar for 10 minutes.

[0027] In the third step, 0.5 g of the ground multi-walled carbon nanotubes were weighed and placed in 25 mL of distilled water. The mixture was sonicated for 5 min and then slowly added to the polyvinyl alcohol solution from the first step using a dropper. The mixture was then heated for another 45 min. After ultrasonic dispersion, a thin film was prepared using a solvent-based film-forming method.

[0028] The fourth step involves rubbing the film obtained in the third step in a specific direction using a friction cloth to create grooves with consistent orientation on the film surface. Then, 1g of high birefringence liquid crystal is dropped into the film, allowing the liquid crystal molecules to align uniformly on the oriented film. Finally, another film obtained in the third step is deposited on the upper surface to obtain a polymer electromagnetic shielding material based on high birefringence liquid crystal.

[0029] Example 2

[0030] A method for preparing a polymer electromagnetic shielding material based on high birefringence liquid crystal includes the following steps:

[0031] First, weigh 6g of polyvinyl alcohol and pour it into a beaker, add 52mL of distilled water, soak at room temperature for 8 hours, then put it into a three-necked flask and heat it in a constant temperature water bath at 90℃ with constant stirring.

[0032] The second step is to weigh 3g of multi-walled carbon nanotubes and grind them in an agate mortar for 10 minutes.

[0033] In the third step, 1g of the ground multi-walled carbon nanotubes was weighed and placed in 30mL of distilled water. The mixture was sonicated for 8 minutes and then slowly added to the polyethylene from the first step using a dropper. The mixture was then heated for another 40 minutes. After ultrasonic dispersion, a thin film was prepared using a solvent-based film-forming method.

[0034] The fourth step involves rubbing the film obtained in the third step in a specific direction using a friction cloth to create grooves with consistent orientation on the film surface. Then, 1.5g of high birefringence liquid crystal is dropped onto the film, allowing the liquid crystal molecules to align uniformly on the oriented film. Finally, another film obtained in the third step is deposited on the upper surface to obtain a polymer electromagnetic shielding material based on high birefringence liquid crystal.

[0035] Example 3

[0036] A method for preparing a polymer electromagnetic shielding material based on high birefringence liquid crystal includes the following steps:

[0037] First, weigh 7g of polyvinyl alcohol and pour it into a beaker, add 58mL of distilled water, soak at room temperature for 8 hours, then put it into a three-necked flask and heat it in a constant temperature water bath at 90℃ with constant stirring.

[0038] The second step is to weigh 4g of multi-walled carbon nanotubes and grind them in an agate mortar for 15 minutes.

[0039] In the third step, 1g of the ground multi-walled carbon nanotubes was weighed and placed in 30mL of distilled water. The mixture was sonicated for 8 minutes and then slowly added to the polyethylene from the first step using a dropper. The mixture was then heated for another 40 minutes. After ultrasonic dispersion, a thin film was prepared using a solvent-based film-forming method.

[0040] The fourth step involves rubbing the film obtained in the third step in a specific direction using a friction cloth to create grooves with consistent orientation on the film surface. Then, 2g of high birefringence liquid crystal is dropped onto the film, allowing the liquid crystal molecules to align uniformly on the oriented film. Finally, another film obtained in the third step is deposited on the upper surface to obtain a polymer electromagnetic shielding material based on high birefringence liquid crystal.

[0041] Example 4

[0042] A method for preparing a polymer electromagnetic shielding material based on high birefringence liquid crystal includes the following steps:

[0043] First, weigh 8g of polyvinyl alcohol and pour it into a beaker, add 65mL of distilled water, soak at room temperature for 8 hours, then put it into a three-necked flask and heat it in a constant temperature water bath at 90℃ with constant stirring.

[0044] The second step is to weigh 5g of multi-walled carbon nanotubes and grind them in an agate mortar for 20 minutes.

[0045] In the third step, 1.5g of the ground multi-walled carbon nanotubes were weighed and placed in 40mL of distilled water. The mixture was sonicated for 10min and then slowly added to the polyethylene from the first step using a dropper. The mixture was then heated for another 50min. After ultrasonic dispersion, a thin film was prepared using a solvent-based film-forming method.

[0046] The fourth step involves rubbing the film obtained in the third step in a specific direction using a friction cloth to create grooves with consistent orientation on the film surface. Then, 2.5g of high birefringence liquid crystal is dropped onto the film, allowing the liquid crystal molecules to align uniformly on the oriented film. Finally, another film obtained in the third step is deposited on the upper surface to obtain a polymer electromagnetic shielding material based on high birefringence liquid crystal.

[0047] Example 5

[0048] A method for preparing a polymer electromagnetic shielding material based on high birefringence liquid crystal includes the following steps:

[0049] First, weigh 9g of polyvinyl alcohol and pour it into a beaker, add 72mL of distilled water, soak at room temperature for 8 hours, then put it into a three-necked flask and heat it in a constant temperature water bath to 90℃ while stirring continuously.

[0050] The second step is to weigh 5g of multi-walled carbon nanotubes and grind them in an agate mortar for 20 minutes.

[0051] Third, weigh 2g of the ground multi-walled carbon nanotubes, add them to 45mL of distilled water, sonicate for 10min, and slowly add them to the polyethylene from the first step using a dropper, while continuing to heat for 30min. After ultrasonic dispersion, prepare a thin film using a solvent-based film-forming method.

[0052] The fourth step involves rubbing the film obtained in the third step in a specific direction using a friction cloth to create grooves with consistent orientation on the film surface. Then, 3g of high birefringence liquid crystal is dropped onto the film, allowing the liquid crystal molecules to align uniformly on the oriented film. Finally, another film obtained in the third step is deposited on the upper surface to obtain a polymer electromagnetic shielding material based on high birefringence liquid crystal.

[0053] Analysis of the electromagnetic shielding performance of polymers based on high birefringence liquid crystals obtained in Examples 1-5:

[0054] The electromagnetic interference (EMI) shielding effectiveness of polymer materials based on high birefringence liquid crystals was measured using a vector network analyzer. The test samples were the materials prepared in Examples 1-5. The test environment temperature was 19°C, the relative humidity was 75%, and the test frequency range was 8-12 GHz. The waveguide method was used for measurement, and the EMI shielding effectiveness was calculated using the formula -10lgT. The results are listed in the table below:

[0055] Example 1 10.08 Example 2 12.93 Example 3 14.49 Example 4 17.02 Example 5 18.62

[0056] Comparative Example

[0057] Comparative Example 5 showed the best electromagnetic shielding effect under the test conditions of the present invention. Therefore, a comparative example was prepared according to the method of Example 5 to examine the effect of the present invention.

[0058] The comparative preparation method is as follows:

[0059] The preparation method for the comparative example is as follows:

[0060] First, weigh 9g of polyvinyl alcohol and pour it into a beaker, add 72mL of distilled water, soak at room temperature for 8 hours, then put it into a three-necked flask and heat it in a constant temperature water bath to 90℃ while stirring continuously.

[0061] The second step is to weigh 5g of multi-walled carbon nanotubes and grind them in an agate mortar for 20 minutes.

[0062] In the third step, 2g of the ground multi-walled carbon nanotubes were weighed and placed in 45mL of distilled water. The mixture was sonicated for 10min and then slowly added to the polyethylene from the first step using a dropper. The mixture was then heated for another 30min. After ultrasonic dispersion, a thin film was prepared using a solvent-based film-forming method to obtain a comparative electromagnetic shielding material.

[0063] The electromagnetic interference (EMI) shielding effectiveness of polymer materials based on high birefringence liquid crystals was measured using a vector network analyzer. The test sample was Example 5. The test environment temperature was 19°C, the relative humidity was 75%, and the test frequency range was 8-12 GHz. The waveguide method was used for measurement, and the EMI shielding effectiveness was calculated using the formula -10lgT. The results are listed in the table below:

[0064] Example 5 18.62 Comparative Example 7.56

[0065] Comparative analysis revealed that, under the same electromagnetic interference environment, the shielding body formed by the material prepared in this invention has an electromagnetic interference attenuation capability of 18.62 dB, while the electromagnetic interference shielding effectiveness of commonly used shielding bodies is 7.56 dB. The material prepared in this invention can effectively attenuate or cancel electromagnetic interference radiation or conduction generated by external electromagnetic interference sources, thereby significantly reducing the energy and range of external interference on the shielded body.

[0066] This embodiment is only used to further illustrate the present invention and should not be construed as a limitation on the scope of protection. Non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention also fall within the scope of protection of the present invention.

Claims

1. A method for preparing polymer electromagnetic shielding materials based on high birefringence liquid crystals, characterized in that: A polymer electromagnetic shielding material is obtained by adding a high birefringence liquid crystal material to the prepared electromagnetic shielding matrix material; the structural formula of the high birefringence liquid crystal molecule is as follows: Where: R is a C1-C7 straight-chain saturated alkyl group; a represents the number of benzene rings, which is any integer from 1 to 4; b represents the amount of water in the triple bond, which is any integer from 1 to 3; c represents the number of benzene rings, which is any integer from 1 to 4. Specifically, the following steps are included: First, weigh 6-9 g of polyvinyl alcohol and put it into a beaker, add 48-72 mL of distilled water, soak at room temperature for 8 hours, then put it into a three-necked flask, and heat it in a constant temperature water bath to 90 ℃ while stirring continuously to obtain a polyvinyl alcohol solution. The second step is to weigh 3-5 g of multi-walled carbon nanotubes and grind them in an agate mortar for 10-20 minutes. The third step involves weighing 0.5-2 g of ground multi-walled carbon nanotubes, placing them in 25-45 mL of distilled water, sonicating for 5-10 min, slowly adding them to the polyvinyl alcohol solution from the first step using a dropper, and continuing to heat for 30-50 min. After ultrasonic dispersion, a thin film is prepared using a solvent-based film-forming method. The fourth step involves rubbing the film obtained in the third step in a certain direction using a friction cloth to form grooves with consistent orientation on the film surface. Then, 1-3 g of high birefringence liquid crystal is dropped onto the film, and the liquid crystal molecules are arranged uniformly on the oriented film. Finally, another film obtained in the third step is laid on the upper surface to obtain a polymer electromagnetic shielding material based on high birefringence liquid crystal.

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