A cross-linkable cyclic olefin copolymer and a method for preparing and using the same

Abstract

The present application relates to a kind of cross-linkable cycloolefin copolymer and its preparation method and application.The preparation method is by copolymerization of norbornene and its derivatives and dicyclopentadiene, and the obtained polymer is prepared into film in the way of solution casting, finally the formation of polymer cross-linking structure is initiated by heat treatment.The polymer is prepared by the second generation Grubbs catalyst to initiate monomer ring-opening metathesis polymerization, norbornene and its derivatives in the polymer can adjust the polarization intensity of polymer under high electric field, dicyclopentadiene can provide cross-linking site, so that cross-linking structure is formed in polymer film.The dielectric film prepared in the present application has excellent thermal stability and energy storage performance, still maintains high breakdown strength, high energy storage density, high charge-discharge efficiency and good structure stability at 150 DEG C, suitable for energy storage capacitor and other electronic devices working in high temperature environment.

Description

Technical Field

[0001] This invention belongs to the field of thin-film capacitor technology, specifically relating to a crosslinkable cyclic olefin copolymer, its preparation method, and its application. Background Technology

[0002] Dielectric capacitors, as indispensable components in advanced electrical and electronic systems, are now widely used in energy, transportation, military, and aerospace. Compared with energy storage devices such as batteries and supercapacitors, dielectric capacitors have a lower energy density, but they offer significant advantages such as high power density, high withstand voltage, and safety and reliability. Currently, the dielectric materials used in commercial dielectric capacitors are mainly divided into two types: ceramic and polymer. Dielectric ceramics possess high dielectric constant, high hardness, and good thermal stability; however, their low breakdown strength, difficult processing, and poor flexibility limit their practical applications. On the other hand, dielectric polymers have attracted attention due to their high breakdown strength, good processability, and low cost. Furthermore, dielectric polymers possess unique self-healing capabilities. In metallized film capacitors, self-healing isolates the breakdown point from the rest of the metallized film electrode, thereby ensuring the stable operation of the film capacitor. Due to these advantages, polymer film capacitors have been widely used in modern electronic and electrical systems.

[0003] A key issue with polymer dielectrics is their relatively low dielectric constant. The dielectric constant of polymer materials is generally below 10, which is 1 to 3 orders of magnitude lower than that of dielectric ceramics. This low dielectric constant limits the polarization ability of polymers under high electric fields, directly affecting their energy storage density. Another key issue is their low operating temperature. Due to the rapid development of aerospace, oil and gas exploration, and new energy power generation, higher requirements are being placed on the operating conditions of polymer film capacitors: in hybrid electric vehicle inverters, capacitors are required to operate at 140–150°C; in oil and gas exploration, depending on the drilling depth, the required operating temperature is 170–300°C; and in aerospace, the required operating temperature reaches above 250°C. All of these necessitate that polymer materials possess excellent thermal stability and high-temperature dielectric energy storage performance. Currently, the most widely used polymer dielectric material is biaxially oriented polypropylene (BOPP). Film capacitors made from this material suffer from the two problems mentioned above: Firstly, due to the very low dielectric constant of BOPP (around 2.2), the energy storage density of the capacitors cannot meet the needs of most applications. Secondly, BOPP has poor thermal stability and cannot withstand high-temperature operating environments. When used at high temperatures, it requires a matching cooling system, which makes it difficult to miniaturize the equipment and increases energy consumption. The long-term operating temperature of BOPP film capacitors should not exceed 85℃, and the maximum operating temperature should not exceed 105℃; otherwise, the capacitor's capacitance will decrease rapidly, significantly reducing its lifespan.

[0004] To solve this problem, various high-T technologies have been developed. g Engineered polymers, such as polyimide (PI), polyethyleneimine (PEI), and polyethylene terephthalate (PET), are used as dielectrics for high-temperature thin-film capacitors. Although these high-T... g Polymers have good thermal stability, but they only work well under relatively low electric fields. When polymers are subjected to both high temperature and high electric field, their discharge energy density and charge-discharge efficiency are greatly reduced, making it difficult to meet the needs of practical applications.

[0005] In summary, the demand for high-temperature resistant and high-energy-storage polymer dielectric materials is increasing daily, and there is an urgent need to develop more new polymer dielectrics. Summary of the Invention

[0006] To address the shortcomings of existing polymer energy storage dielectrics, the present invention aims to design and provide a crosslinkable cyclic olefin copolymer and its preparation method. This crosslinkable cyclic olefin copolymer can be synthesized by ring-opening metathesis polymerization (ROMP) of monomers initiated by a second-generation Grubbs catalyst, followed by polymer film formation via casting. Further heat treatment of the film induces the formation of a crosslinked network structure within the polymer, thereby significantly improving its breakdown strength and thermal stability, reducing leakage current under high temperature and high electric field conditions, and increasing its charge-discharge efficiency.

[0007] The solution of the present invention is as follows:

[0008] The first aspect of this invention provides a crosslinkable cyclic olefin copolymer, the structure of which is as follows:

[0009]

[0010] In the structural formula, a, b, and c represent the number of repeating units;

[0011] R1 and R2 are selected from one of the following structures:

[0012] R1:

[0013] R2:

[0014] The second aspect of the present invention provides a method for preparing the above-mentioned crosslinkable cyclic olefin copolymer, the method comprising the following steps: (1) dissolving the two polymer monomers, norbornene and dicyclopentadiene, containing R1 and R2, completely in anhydrous dichloromethane and adding them to a Schlenk flask equipped with a magnetic stir bar under a N2 atmosphere, and dissolving the second-generation Grubbs catalyst in anhydrous dichloromethane and adding it to the Schlenk flask, and carrying out a ROMP reaction under anhydrous and oxygen-free conditions; (2) adding a terminator after a certain reaction time, continuing to stir for 1 hour to end the reaction; and washing and drying the obtained product to obtain the crosslinkable cyclic olefin copolymer.

[0015] Furthermore, in step (1), the second-generation Grubbs catalyst is 1,3-bis(2,4,6-trimethylphenyl)-2-(imidazolidinedimethyl)(dichlorobenzylmethyl)(tricyclohexylphosphine)ruthenium.

[0016] Furthermore, the ratio of the total molar amount of the polymerized monomer to the molar amount of the second-generation Grubbs catalyst is (500-4000):1.

[0017] Furthermore, in step (1), the molar amount of the dicyclopentadiene accounts for 5% to 50% of the total molar amount of the polymer monomer.

[0018] Furthermore, in step (1), the temperature of the ROMP reaction is 20-30°C, and the reaction time is 0.5-4 hours.

[0019] Furthermore, in step (2), the terminating agent is ethoxyethylene.

[0020] A third aspect of the present invention provides a method for preparing a crosslinkable cyclic olefin copolymer dielectric film, wherein the crosslinkable cyclic olefin copolymer dielectric film is made from the crosslinkable cyclic olefin copolymer as described in claim 1; the preparation method includes: fully dissolving the crosslinkable cyclic olefin copolymer in anhydrous chloroform to obtain a polymer solution; uniformly drop-coating the polymer solution onto a carrier, and after the solvent has completely evaporated at room temperature, performing a heat treatment at 150°C for 1 to 3 hours to obtain a uniform crosslinkable cyclic olefin copolymer dielectric film; wherein the concentration of the polymer solution is 1 wt% to 3 wt%.

[0021] The fourth aspect of the present invention provides a crosslinkable cyclic olefin copolymer dielectric film prepared by the method described above.

[0022] The fifth aspect of the present invention provides the application of the crosslinkable cyclic olefin copolymer as described above in the field of high-temperature resistant polymer dielectrics.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The crosslinkable cyclic olefin copolymer prepared by this invention has a rigid backbone and can be initiated to form a crosslinked network structure through heat treatment, thereby ensuring its excellent thermal stability.

[0025] By introducing a highly polar norbornene derivative into the copolymer, its dielectric constant can be effectively improved, giving it a high energy storage density. The formation of the cross-linked network can also effectively suppress the increase of its leakage conduction loss, giving it good high-temperature energy storage performance. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention, wherein:

[0027] Figure 1 This is a flowchart illustrating the preparation route of crosslinkable cyclic olefin copolymers provided in embodiments of the present invention;

[0028] Figure 2This is a breakdown field diagram of different components of poly(norbornene-dicyclopentadiene) in Example 1 of the present invention;

[0029] Figure 3 The graph shows the changes in dielectric constant and loss of different components of poly(norbornene-dicyclopentadiene) as a function of frequency in Example 1 of the present invention.

[0030] Figure 4 This is a graph showing the energy storage density and charge / discharge efficiency of different components of poly(norbornene-dicyclopentadiene) at room temperature in Example 1 of the present invention;

[0031] Figure 5 The graph shows the energy storage density and charge / discharge efficiency of different components of poly(norbornene-dicyclopentadiene) at 150°C in Example 1 of this invention.

[0032] Figure 6 The breakdown field strength diagrams of different components of poly((2-cyano-5-norbornene)-dicyclopentadiene) in Example 2 of the present invention are shown.

[0033] Figure 7 This is a graph showing the dielectric constant and loss of different components of poly((2-cyano-5-norbornene)-dicyclopentadiene) as a function of frequency in Example 2 of the present invention;

[0034] Figure 8 The graph shows the energy storage density and charge / discharge efficiency of different components of poly((2-cyano-5-norbornene)-dicyclopentadiene) at room temperature in Example 2 of this invention.

[0035] Figure 9 The graph shows the energy storage density and charge / discharge efficiency of different components of poly((2-cyano-5-norbornene)-dicyclopentadiene) at 150°C in Example 2 of this invention. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a method for preparing crosslinkable cyclic olefin copolymers, the synthetic route being as follows: Figure 1 As shown, the method includes the following steps:

[0038] (1) The two polymer monomers, norbornene and dicyclopentadiene, containing R1 and R2, were completely dissolved in anhydrous dichloromethane and then added to a Shrek bottle equipped with a magnetic stir bar under N2 atmosphere. The second-generation Grubb catalyst was dissolved in anhydrous dichloromethane and added to the Shrek bottle. The ring-opening metathesis polymerization reaction was carried out under anhydrous and oxygen-free conditions.

[0039] (2) After a certain reaction time, a terminator is added, and the reaction is stopped after stirring for 1 hour. The resulting product is washed and dried to obtain the crosslinkable cyclic olefin copolymer.

[0040] Example 1

[0041] This embodiment provides a crosslinkable cyclic olefin copolymer with the following structure:

[0042]

[0043] Its preparation method includes the following steps:

[0044] 1. A mixture of 0.005 mol norbornene (NB) and dicyclopentadiene (DCPD) was completely dissolved in 40 mL of anhydrous dichloromethane and added to a Schlenk flask equipped with a magnetic stirrer under a nitrogen atmosphere. 0.001 mmol of the second-generation Grubbs catalyst was completely dissolved in 5 mL of anhydrous dichloromethane and added to the above Schlenk flask. The ROMP reaction was carried out at room temperature.

[0045] 2. After reacting for 1 hour, add 0.3 mL of ethoxyethylene and continue stirring for another hour to stop the reaction. Wash and dry the resulting product to obtain the target product.

[0046] The preparation of it into a crosslinkable cyclic olefin copolymer dielectric film also includes the following steps:

[0047] 3. Dissolve 100 mg of copolymer in 6 mL of anhydrous chloroform to obtain a polymer solution. Dip the polymer solution evenly onto a glass plate. After the solvent has completely evaporated at room temperature, heat-treat the plate at 150 °C for 3 h to obtain a uniform crosslinkable cyclic olefin copolymer dielectric film.

[0048] like Figure 2 As shown, the addition of dicyclopentadiene enables the copolymer to form a cross-linked structure through thermal initiation, thereby significantly enhancing the breakdown strength of the film. Compared to polynorbornene, the breakdown strength of the poly(norbornene-dicyclopentadiene) copolymer is significantly improved at different temperatures, with the optimal composition of the poly(norbornene-dicyclopentadiene) copolymer showing an approximately 200 MV m increase in breakdown strength compared to polynorbornene.-1 The dielectric constant and loss of poly(norbornene-dicyclopentadiene) with different components vary with frequency as follows: Figure 3 As shown, since the addition of dicyclopentadiene did not significantly change the polarity of the copolymer, the dielectric constant and dielectric loss of the poly(norbornene-dicyclopentadiene) copolymer at room temperature did not change significantly compared to polynorbornene. The energy storage density and charge / discharge efficiency of poly(norbornene-dicyclopentadiene) with different components are shown in the figure. Figure 4 , 5 As shown, the introduction of dicyclopentadiene significantly improves the breakdown strength of the copolymer, but does not significantly change its dielectric constant. Therefore, the increase in the copolymer's energy density almost entirely depends on the increase in its breakdown strength. On the other hand, the formation of the cross-linked network helps reduce leakage current and lowers losses during the film's charge and discharge process, thereby effectively improving its energy conversion efficiency. Compared to polynorbornene, the optimally composed poly(norbornene-dicyclopentadiene) copolymer achieves a maximum discharge energy density of 9.88 J / cm³ at room temperature. -3 At 150℃, its maximum discharge energy density reaches 7.48 J / cm³. -3 .

[0049] Example 2

[0050] This embodiment provides a method for preparing a crosslinkable cyclic olefin copolymer, the structure of which is as follows:

[0051]

[0052] Its preparation method includes the following steps:

[0053] 1. A mixture of 0.005 mol of 2-cyano-5-norbornene (NBCN) and dicyclopentadiene was completely dissolved in 40 mL of anhydrous dichloromethane and added to a Schlenk flask equipped with a magnetic stirrer under a nitrogen atmosphere. 0.001 mmol of the second-generation Grubbs catalyst was completely dissolved in 5 mL of anhydrous dichloromethane and added to the Schlenk flask. The ROMP reaction was carried out at room temperature.

[0054] 2. After reacting for 4 hours, add 0.3 mL of ethoxyethylene, and continue stirring for 1 hour to stop the reaction. Wash and dry the resulting product to obtain the target product.

[0055] The preparation of it into a crosslinkable cyclic olefin copolymer dielectric film also includes the following steps:

[0056] 3. Dissolve 100 mg of copolymer in 6 mL of anhydrous chloroform to obtain a polymer solution. Dip the polymer solution evenly onto a glass plate. After the solvent has completely evaporated at room temperature, heat-treat the plate at 150 °C for 3 h to obtain a uniform crosslinkable cyclic olefin copolymer dielectric film.

[0057] like Figure 6 As shown, the breakdown strength of the poly((2-cyano-5-norbornene)-dicyclopentadiene) copolymer film was significantly improved compared to that of poly(2-cyano-5-norbornene), which can also be attributed to the formation of cross-linked networks in the film. The dielectric constant and loss of different poly(norbornene-dicyclopentadiene) components as a function of frequency are shown in the figure. Figure 7 As shown, the introduction of highly polar norbornene derivatives results in a higher dielectric constant for the copolymer, while the increased proportion of dicyclopentadiene in the copolymer leads to a slight decrease in its dielectric constant. The energy storage density and charge / discharge efficiency of poly((2-cyano-5-norbornene)-dicyclopentadiene) with different components are shown in the figure. Figure 8 , 9 As shown, optimal dielectric energy storage performance can be achieved by controlling the dielectric constant and crosslinking degree of the copolymer. Compared to poly(2-cyano-5-norbornene), the optimally composed poly((2-cyano-5-norbornene)-dicyclopentadiene) copolymer achieves a maximum discharge energy density of 11.81 J / cm² at room temperature. -3 Its maximum discharge energy density reaches 8.69 J / cm³ at 150℃. -3 .

[0058] In summary, this invention provides a crosslinkable cyclic olefin copolymer and its preparation method. This crosslinkable cyclic olefin copolymer is synthesized by initiating a ROMP reaction of monomers using a second-generation Grubbs catalyst, followed by a casting method to obtain a crosslinkable cyclic olefin copolymer dielectric film. Further heat treatment of the film induces the formation of a crosslinked network structure within the polymer itself without the addition of a crosslinking agent. This effectively suppresses polymer chain movement at high temperatures, increasing the glass transition temperature and giving the material excellent thermal stability. Furthermore, the formation of the crosslinked structure significantly suppresses the increase in leakage current, ensuring high breakdown strength and high charge-discharge efficiency. Simultaneously, the introduction of highly polar norbornene derivatives significantly improves the dielectric constant of the copolymer, thereby increasing its energy storage density. The crosslinkable cyclic olefin copolymer provided by this invention is suitable for application in the field of high-temperature resistant polymer dielectrics.

[0059] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0060] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A cross-linkable cycloolefin copolymer, characterized by, The structure of the crosslinkable cyclic olefin copolymer is as follows: ； In the structural formula, a, b, and c represent the number of repeating units; R1 and R2 are selected from one of the following structures: R1： ； R2： ； The method for preparing the crosslinkable cyclic olefin copolymer includes the following steps: (1) The two polymer monomers, norbornene and dicyclopentadiene, containing R1 and R2, are completely dissolved in anhydrous dichloromethane and then added to a Shrek flask equipped with a magnetic stirrer under a N2 atmosphere. The second-generation Grubb catalyst is dissolved in anhydrous dichloromethane and added to the Shrek flask. The ring-opening metathesis polymerization reaction is carried out under anhydrous and oxygen-free conditions. The molar amount of dicyclopentadiene accounts for 5% to 50% of the total molar amount of the polymer monomers. (2) After a certain reaction time, a terminator is added, and the reaction is stopped after stirring for 1 hour. The resulting product is washed and dried to obtain the crosslinkable cyclic olefin copolymer.

2. The method for preparing a cross-linkable cyclic olefin copolymer according to claim 1, wherein The method includes the following steps: (1) The two polymer monomers, norbornene and dicyclopentadiene, containing R1 and R2, were completely dissolved in anhydrous dichloromethane and then added to a Shrek bottle equipped with a magnetic stir bar under N2 atmosphere. The second-generation Grubb catalyst was dissolved in anhydrous dichloromethane and added to the Shrek bottle. The ring-opening metathesis polymerization reaction was carried out under anhydrous and oxygen-free conditions. (2) After a certain reaction time, a terminator is added, and the reaction is stopped after stirring for 1 hour. The resulting product is washed and dried to obtain the crosslinkable cyclic olefin copolymer.

3. The method for preparing a cross-linkable cyclic olefin copolymer according to claim 2, wherein In step (1), the second-generation Grubb catalyst is 1,3-bis(2,4,6-trimethylphenyl)-2-(imidazolidinedimethyl)(dichlorobenzylmethyl)(tricyclohexylphosphine)ruthenium.

4. The method for preparing a cross-linkable cyclic olefin copolymer according to claim 2, wherein The ratio of the total molar amount of the polymer monomer to the molar amount of the second-generation Grubb catalyst is (500~4000):

1.

5. The method for preparing a cross-linkable cyclic olefin copolymer according to claim 2, wherein In step (1), the molar amount of dicyclopentadiene accounts for 5% to 50% of the total molar amount of the polymer monomer.

6. The method for preparing a cross-linkable cyclic olefin copolymer according to claim 2, wherein In step (1), the temperature of the ring-opening metathesis polymerization reaction is 20~30℃, and the reaction time is 0.5~4 hours.

7. The method for preparing the crosslinkable cyclic olefin copolymer according to claim 2, characterized in that, In step (2), the terminating agent is ethoxyethylene.

8. A method for producing a cross-linkable cyclo-olefin copolymer dielectric film, characterized by, The crosslinkable cyclic olefin copolymer dielectric film is made of the crosslinkable cyclic olefin copolymer as described in claim 1; The preparation method includes: fully dissolving the crosslinkable cyclic olefin copolymer in anhydrous chloroform to obtain a polymer solution; uniformly drop-coating the polymer solution onto a carrier; after the solvent has completely evaporated at room temperature, performing a heat treatment at 150°C for 1 h to 3 h to obtain a uniform crosslinkable cyclic olefin copolymer dielectric film. The concentration of the polymer solution is 1 wt% to 3 wt%.

9. The crosslinkable cyclic olefin copolymer dielectric film prepared by the method for preparing the crosslinkable cyclic olefin copolymer dielectric film as described in claim 8.

10. The application of the crosslinkable cyclic olefin copolymer as described in claim 1 in the field of high-temperature resistant polymer dielectrics.

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