Cross-linked polymer dielectric thin film with adjustable dielectric constant as well as preparation method and application of cross-linked polymer dielectric thin film
By preparing ultraviolet crosslinked norbornenomide coumarin monomer, the problems of heat resistance and dielectric constant of polymer dielectric at high temperatures are solved, and high energy storage density and stable capacitance performance are achieved.
Patent Information
- Application Number
- CN202510695450.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-28
- Publication Date
- 2025-09-02
AI Technical Summary
It is difficult to achieve the heat resistance and dielectric constant improvement of existing polymer dielectrics at high temperatures, resulting in insufficient energy storage density and cannot meet the high energy density requirements for miniaturization of electronic equipment.
The reaction of 5-norbornene-2,3-dicarboxylic anhydride and 7-amino-4-trifluoromethylcoumarin to form norbornene-enimide coumarin monomer. After ring-opening metathesis polymerization by Grubbs catalyst, ultraviolet light cross-links to form compound II, controlling the ultraviolet light exposure time to regulate the cross-linking degree to increase the dielectric constant.
The coordinated improvement of heat resistance and dielectric constant was achieved, the glass transition temperature was increased to 273℃, the dielectric constant was increased from 3.85 to 4.64, and the energy storage density at 150℃ reached 7.4J/cm3, maintaining a 90% charge and discharge efficiency, and continuously charge and discharge 50,000 times without breakdown at a 200MV/m electric field.
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of dielectric materials and energy storage materials, and in particular to a cross-linked polymer dielectric film with adjustable dielectric constant, a preparation method thereof, and applications thereof. Background Art
[0002] Polymer dielectric film is an important component of electrostatic capacitors and is widely used in modern electronic and power systems, such as new energy vehicles, oil exploration, and aerospace equipment. This is mainly due to its advantages such as excellent processing characteristics and high breakdown strength. At present, the most commonly used commercial polymer dielectric on the market is biaxially oriented polypropylene (BOPP), which has excellent charge and discharge cycle stability. However, due to the poor heat resistance of BOPP (glass transition temperature is about 105°C), its energy storage performance deteriorates rapidly when the operating temperature exceeds this threshold. In addition, BOPP exhibits a low dielectric constant of about 2.2, which means that the discharge energy density under equal electric field is low. Under a high electric field of 600MV / m, the discharge energy density of BOPP is only 4J / cm 3 Due to the above two limitations, the current energy storage capacity of BOPP at high temperature can no longer meet the urgent demand for high energy density in the trend of increasing miniaturization of electronic and electrical equipment (at 150°C, the energy storage density of 90% charge and discharge efficiency must exceed 7J / cm 3 ). Therefore, there is an urgent need to develop new polymer dielectrics with high heat resistance and high dielectric constant.
[0003] Among the methods for improving the heat resistance of polymer dielectrics, crosslinking is considered a promising approach and has attracted widespread attention. Compared to linear polymers, crosslinked polymers contain a large number of interchain covalent bonds. The presence of these interchain covalent bonds effectively restricts the movement of polymer chain segments, thereby improving the polymer's heat resistance. However, these covalent bonds also restrict the polarization movement of internal dipoles in the polymer under electric field, resulting in a significant decrease in the dielectric constant of crosslinked polymer dielectrics compared to uncrosslinked polymer dielectrics. This decrease in dielectric constant means a decrease in energy storage density under the same electric field, which limits further improvements in the energy storage density of polymer dielectrics. Furthermore, to achieve the target energy storage density under operating conditions, a higher electric field must be applied to the crosslinked polymer dielectrics. Increasing the operating electric field not only increases the risk of breakdown of the polymer dielectric under operating conditions but also inevitably reduces its cycle life. Therefore, achieving a synergistic improvement in the heat resistance and dielectric constant of crosslinked polymer dielectrics is crucial. Summary of the Invention
[0004] Aiming at the shortcomings of existing polymer dielectrics in high-temperature capacitance performance, the present invention proposes a novel photoreactive polymer dielectric and a method for preparing the same, so as to achieve a synergistic improvement in heat resistance and dielectric constant of the cross-linked polymer dielectric.
[0005] To achieve the above objectives, the present invention provides a method for preparing a cross-linked polymer dielectric film with a controllable dielectric constant, comprising the following steps:
[0006] S1. 5-Norbornene-2,3-dicarboxylic anhydride and 7-amino-4-trifluoromethylcoumarin were subjected to imidization reaction to obtain norbornene imide coumarin monomer. The synthesis route is as follows:
[0007]
[0008] S2. The norbornene imide coumarin monomer was subjected to a ring-opening metathesis polymerization reaction using a Grubbs catalyst under anhydrous and oxygen-free conditions. After terminating the reaction, the polymer product was diluted, settled, washed, and dried to obtain Compound I. The synthesis route is as follows:
[0009]
[0010] S3. Compound I is dissolved in a solvent to obtain a film-forming solution, and the film-forming solution is coated and then heat-cured to obtain a transparent flexible film;
[0011] S4. The transparent flexible film is exposed to ultraviolet light for cross-linking treatment, the exposure time is 2.5-7.5min, to obtain a cross-linked polymer dielectric film comprising a material component comprising compound I and compound II;
[0012] The above-mentioned compound I and compound II are shown in the following structures (1) and (2), respectively:
[0013]
[0014] Here, n represents the number of repeating structural units, and preferably n is an integer greater than 200.
[0015] According to existing literature reports, coumarin groups undergo a 2+2 cycloaddition reaction under ultraviolet light, forming an intermolecular crosslinked structure. Therefore, the coumarin groups in Compound I of the present invention undergo a similar crosslinking reaction under ultraviolet light to produce Compound II. This crosslinking reaction has been extensively studied and confirmed to be highly efficient and clean. Therefore, the present invention achieves the conversion of Compound I to Compound II through ultraviolet light exposure, forming a crosslinked polymer dielectric film.
[0016] The present invention achieves precise control of the dielectric constant of the film by regulating the degree of crosslinking by controlling the UV light exposure time (2.5-7.5 minutes). As the exposure time increases, the degree of crosslinking increases, and the dielectric constant also increases. For example, when the UV light exposure time increases from 0 minutes to 7.5 minutes, the dielectric constant increases from 3.85 to 4.64, indicating that the dielectric constant can be regulated through controlled crosslinking.
[0017] It should be noted that the present invention does not particularly limit the specific process and parameters for synthesizing norbornene imide coumarin monomers using 5-norbornene-2,3-dicarboxylic anhydride and 7-amino-4-trifluoromethyl coumarin as starting materials, and can be reasonably selected according to the relevant imidization reaction process known in the art. For example, 5-norbornene-2,3-dicarboxylic anhydride and 7-amino-4-trifluoromethyl coumarin are dissolved in acetic acid, and then reacted with 4-dimethylaminopyridine as a catalyst, and after the reaction, purification and separation are performed to obtain the target product.
[0018] It should be noted that the present invention does not specifically limit the specific process and parameters for the ROMP reaction of the norbornene imide coumarin monomer to synthesize compound I, and can be reasonably selected according to the ROMP reaction known in the art. For example, under anhydrous and anaerobic conditions, the norbornene imide coumarin monomer is subjected to a ROMP reaction with a Grubbs catalyst, and after the reaction is terminated, post-treatment such as dilution, sedimentation, washing, and drying is performed to obtain the target product. The solvent for the ROMP reaction can be ultra-dry dichloromethane, the concentration of the norbornene imide coumarin monomer is 0.05-0.1 mol / L; the Grubbs catalyst is a third-generation Grubbs catalyst, namely dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)bis(3-bromopyridinium)ruthenium(II); the molar ratio of 5-norbornene-2-(trifluoromethyl)cinnamate monomer to the third-generation Grubbs catalyst is 200-500:1; the ROMP reaction temperature is 20-40°C, and the reaction time is 1-2 hours; the ROMP reaction terminator is vinyl ethyl ether. As a further preferred technical solution of the present invention, the process of heat curing after coating the film-forming solution is: pre-evaporating the solvent at 45-60°C, and then completely drying under vacuum at 80-110°C, for example, 80°C, 100°C, 105°C, 110°C, etc.
[0019] As a further preferred technical solution of the present invention, compound I is dissolved in a solvent at a mass concentration of 3-5% to prepare a membrane-forming solution; the solvent can be N,N-dimethylformamide.
[0020] As a further preferred technical solution of the present invention, when UV cross-linking is performed, the wavelength of the UV light is 365 nm.
[0021] The material composition of the cross-linked polymer dielectric film with adjustable dielectric constant of the present invention is composed of compound I and compound II, and controllable cross-linking is performed by exposure so that the molar content of compound II is 5-70% of the total of compound I and compound II, for example, 5%, 8%, 12%, 20%, 45%, 56%, 66%, 70%, 75%, etc.
[0022] According to another aspect of the present invention, the present invention also provides a cross-linked polymer dielectric film, which is prepared by the above method.
[0023] According to another aspect of the present invention, the present invention also provides an application of a cross-linked polymer dielectric film in an electrostatic energy storage insulating material.
[0024] Compared with the prior art, the advantages or beneficial effects of the present invention include at least:
[0025] 1) The polymer dielectric film provided by the present invention is composed of a compound I having a structure (1) and a compound II having an intermolecular crosslinked structure (2) generated by ultraviolet crosslinking of the compound I. The ultraviolet crosslinking process is clean and efficient, and the structural unit is single, omitting the crosslinking process of the doped molecules. The preparation is simple, the cost is low, and the film is suitable for large-scale production.
[0026] 2) The cross-linked polymer dielectric film provided by the present invention can achieve a synergistic improvement in heat resistance and dielectric constant. After irradiation with 365nm ultraviolet light for 7.5 minutes, the glass transition temperature and dielectric constant of the resulting cross-linked polymer dielectric film increased to 273°C and 4.64, respectively.
[0027] 3) The cross-linked polymer dielectric film provided by the present invention has a thermal conductivity of 7.4 J / cm at a temperature of 150°C. 3 The energy storage density is high and the charge and discharge efficiency is greater than 90%, which exceeds the existing high-temperature polymer dielectric materials.
[0028] 4) The cross-linked polymer dielectric film provided by the present invention can be continuously charged and discharged for 50,000 times under the conditions of 200 MV / m and 150°C, and maintains stable energy storage performance. The energy storage density of the first and last charge and discharge tests is 0.736 J / cm 3 and 0.716 J / cm 3 , fluctuation is less than 3%. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0030] Figure 1This is the H NMR spectrum of the norbornene imide coumarin monomer obtained in Example 1 of the present invention;
[0031] Figure 2 is the H NMR spectrum of Compound 1 obtained in Example 1 of the present invention;
[0032] Figure 3 Differential scanning calorimetry curves of a series of cross-linked polymer dielectric films provided in Example 1 of the present invention;
[0033] Figure 4 Broadband dielectric spectra of a series of cross-linked polymer dielectric films provided in Example 1 of the present invention;
[0034] Figure 5 Energy storage density diagram of a series of cross-linked polymer dielectric films provided in Example 1 of the present invention;
[0035] Figure 6 This is a charge-discharge cycle diagram of a series of cross-linked polymer dielectric films provided in Example 1 of the present invention.
[0036] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION
[0037] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.
[0038] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.
[0039] Example 1
[0040] This embodiment provides a method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant, which specifically includes:
[0041] Step 1: In a round-bottom flask, add 5-norbornene-2,3-dicarboxylic anhydride (3.35g, 20mmol) and 7-amino-4-trifluoromethylcoumarin (4.57g, 20mmol). Then, add 4-dimethylaminopyridine (0.4g, 3.3mmol) and acetic acid (150ml). Stir the mixture at 110°C for 24h. After the reaction mixture is cooled, pour into excess deionized water and filter. The resulting white solid is recrystallized from 100mL of anhydrous ethanol and dried in an oven at 60°C to obtain the norbornene imide coumarin monomer with a yield of 90%.
[0042] Step 2: After adding norbornene imide coumarin monomer (500 mg, 1.24 mmol) to a 100 mL reaction tube, 10 mL of ultra-dry dichloromethane was added for dissolution, liquid nitrogen was frozen, and the atmosphere was replaced with nitrogen three times. After thawing, the third-generation Grubbs catalyst (2.7 mg, 0.003 mmol) was added under a nitrogen atmosphere. The ROMP reaction was carried out at 30°C for 2 h. Subsequently, 0.5 mL of vinyl ethyl ether was added as a terminator. The reaction liquid was precipitated into 200 mL of ethanol and centrifuged to obtain Compound I, which was washed three times with ethanol. The yield was 91%.
[0043] Step 3: 60 mg of compound I was dissolved in 4 mL of N,N-dimethylformamide (solution concentration was 5 wt%), and 0.3 g of the solution was evenly drop-coated on a flat glass plate through a 0.22 μm filter. The film was first dried on a 60°C hot plate for 2 h to remove most of the N,N-dimethylformamide solution. The film was then placed in a vacuum oven, heated to 110°C, and vacuum dried for 30 min to obtain a transparent flexible film. The film was then placed directly under a 365 nm UV lamp for UV exposure with exposure times of 0 min, 2.5 min, 5 min, and 7.5 min to obtain a series of cross-linked polymer dielectric films.
[0044] To verify the degree of crosslinking under different UV exposure times, swelling experiments were conducted on a series of crosslinked polymer dielectric films prepared in Example 1. The results showed that as the UV exposure time increased, the film's swelling gradually decreased, indicating a gradual increase in the degree of crosslinking. The specific data are shown in the table below:
[0045] UV exposure time (min) Swelling degree (%) Crosslinking degree (%) 0 100 0 2.5 85 15 5.0 60 40 7.5 50 50
[0046] As can be seen from the table, with the increase of UV exposure time, the degree of cross-linking significantly increases, indicating that the degree of cross-linking can be regulated by controlling the exposure time.
[0047] In order to illustrate the technical effect of the technical solution of the present invention, the product prepared in Example 1 was characterized, specifically:
[0048] 1. Structural Characterization
[0049] The 1H NMR nuclear magnetic resonance spectroscopy of the norbornene imide coumarin monomer and compound I prepared in Example 1 was characterized using a Bruker 400-Left NMR spectrometer. The results were: Figure 1 and Figure 2 As shown. Among them, Figure 1 This is the H NMR spectrum of norbornene imide coumarin monomer. Figure 2 is the nuclear magnetic hydrogen spectrum of compound I. Figure 1 and Figure 2It can be seen that Example 1 successfully synthesized the norbornene imide coumarin monomer and compound I with the structure shown.
[0050] 2. Heat resistance characterization
[0051] The series of cross-linked polymer dielectric films prepared in Example 1 were subjected to differential scanning calorimetry analysis (nitrogen flow, heating rate of 20°C / min, temperature range of 30-300°C). The results were as follows: Figure 3 shown.
[0052] according to Figure 3 As can be seen, the heat resistance (glass transition temperature) of the cross-linked polymer dielectric film increases with the extension of UV cross-linking time. Among them, the film with a light exposure time of 7.5 minutes achieved the highest glass transition temperature of 273°C, which is 18°C higher than the film without light exposure.
[0053] 3. Dielectric performance test
[0054] The cross-linked polymer dielectric films prepared in Example 1 were subjected to broadband dielectric spectrum analysis (test frequency 1 to 10 6 Hz), the result is Figure 4 shown.
[0055] according to Figure 4 It can be seen that with the extension of the UV cross-linking time, the dielectric constant of the obtained cross-linked polymer dielectric film continues to increase. At the same time, the obtained cross-linked polymer dielectric film has a low dielectric loss (<0.002) at 10 Hz.
[0056] 4.Electric energy storage performance test
[0057] First, electrodes were plated on the series of cross-linked polymer dielectric films obtained above. Specifically, a magnetron sputtering coating machine was used, the coating machine current was set to 135A, and the electroplating time was 5 minutes. Circular gold electrodes (thickness of about 100 nm, diameter of 1 to 12 mm) were plated on the upper and lower surfaces of the crystallized cross-linked polymer dielectric film.
[0058] Then, the cross-linked polymer dielectric film with electrodes was placed in a ferroelectric instrument equipped with an environmental chamber for polarization energy storage performance testing. The environmental chamber was set at 150°C, and the electric field strength applied to the test sample was accumulated at 50MV / m. The electric field strength and electric displacement curve were derived in each accumulation process until the sample was electrically broken down. The energy storage density and charge-discharge efficiency were calculated by integrating the electric field strength and electric displacement curves. The results are: Figure 5 shown.
[0059] according to Figure 5 It can be seen that at 150°C, the cross-linked polymer dielectric film with an illumination time of 5 minutes achieved the highest energy storage density of 7.4 J / cm 3 (Charge and discharge efficiency>90%), with high energy storage density and charge and discharge efficiency.
[0060] 5. Continuous charge and discharge cycle test:
[0061] The test is based on the cross-linked polymer dielectric film with the above-mentioned electrode (illumination time is 5 minutes). The cross-linked polymer dielectric film with the electrode is placed in a capacitance tester equipped with an environmental chamber for charge and discharge cycle testing. The temperature of the environmental chamber is set at 150°C. An electric field with a frequency of 1Hz and an intensity of 200MV / m is applied to the test sample for 50,000 consecutive cycles. The oscilloscope outputs the storage and discharge density, and calculates the charge and discharge efficiency each time.
[0062] according to Figure 6 It can be seen that the cross-linked polymer dielectric film with an illumination time of 5 minutes still has excellent energy storage performance after 50,000 continuous charge and discharge cycles without breakdown.
[0063] In summary, the present invention uses a ring-opening metathesis polymerization reaction initiated by Grubbs' catalyst to obtain a series of polymer dielectric films with different light-crosslinking times. When the light-crosslinking time is extended from 0 minutes to 7.5 minutes, the dielectric constant of the polymer dielectric can be increased from 3.85 to 4.64, and the glass transition temperature is increased from 255°C to 273°C. At a temperature of 150°C, the obtained cross-linked polymer dielectric film can achieve an energy storage density of 7.4 J / cm3 while maintaining a charge-discharge efficiency of 90%. 3 .
[0064] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.
Claims
1. A method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant, characterized in that: The following steps are involved: S1. performing an imidization reaction of 5-norbornene-2,3-dicarboxylic anhydride and 7-amino-4-trifluoromethyl coumarin to obtain a norbornene imide coumarin monomer; S2. The norbornene imide coumarin monomer was subjected to a ring-opening metathesis polymerization reaction using a Grubbs catalyst under anhydrous and oxygen-free conditions. After terminating the reaction, the polymer product was diluted, settled, washed, and dried to obtain compound I; S3. Compound I is dissolved in a solvent to obtain a film-forming solution, and the film-forming solution is coated and then heat-cured to obtain a transparent flexible film; S4. The transparent flexible film is exposed to ultraviolet light for cross-linking treatment, the exposure time is 2.5-7.5min, to obtain a cross-linked polymer dielectric film comprising a material component comprising compound I and compound II; The above-mentioned compound I and compound II are shown in the following structures (1) and (2), respectively: Where n represents the number of repeating structural units.
2. The method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant according to claim 1, characterized in that: In the structures (1) and (2), n is an integer of 200 or greater.
3. The method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant according to claim 1, characterized in that: In step S2: The solvent for the ring-opening metathesis polymerization reaction is dichloromethane; and / or, Grubbs catalyst is 3-phenyl-1H-inden-1-ylidene[bis(isobutylphosphine ligand)]ruthenium(II) dichloride; and / or, The molar ratio of norbornene imide coumarin monomer to Grubbs catalyst is (200-500):1; and / or, The concentration of norbornene imide coumarin monomer is 0.05 to 0.1 mol / L; and / or, The temperature of the ring-opening metathesis polymerization reaction is 20 to 40° C.; and / or, The terminator for the ring-opening metathesis polymerization reaction is vinyl ethyl ether.
4. The method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant according to claim 1, characterized in that: In step S3 , the process of heat curing after coating the film-forming liquid is as follows: partially volatilizing the solvent at 45-60° C. in advance, and then completely drying the film under vacuum at 80-110° C.
5. The method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant according to claim 1, characterized in that: In step S3: Compound I is dissolved in a solvent at a mass concentration of 3-5%; and / or the solvent is N,N-dimethylformamide.
6. The method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant according to claim 1, wherein: In step S4: the wavelength of the ultraviolet light is 365 nm.
7. The method for preparing a cross-linked polymer dielectric film with adjustable dielectric constant according to any one of claims 1 to 6, characterized in that: In step S4: controllable cross-linking is performed by exposure, and the molar content of compound II in the obtained cross-linked polymer dielectric film with adjustable dielectric constant is 5-70% of the total of compound I and compound II.
8. A cross-linked polymer dielectric film, characterized in that: The method according to any one of claims 1 to 7 is used for preparation.
9. Use of the cross-linked polymer dielectric film according to claim 8 in electrostatic energy storage insulating materials.