A method for preparing a full-organic small-molecule composite polymer thin film and a product thereof

Abstract

The present application belongs to the technical field of polymer dielectric energy storage material, and discloses a preparation method of a full-organic small-molecule composite polymer film and a product. The preparation method comprises the following steps: mixing a mixed solution of PVDF and PMMA with a PE EU solution to form a pre-preparation solution; casting the pre-preparation solution on a substrate and heating and drying, and then heat treating in a vacuum environment to obtain the required composite polymer film. The present application also discloses the product prepared by the above preparation method. Through the present application, the problems of low discharge energy density and charge-discharge efficiency of ferroelectric-based polymer films are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer dielectric energy storage materials, and more specifically, relates to a method for preparing an all-organic small molecule composite polymer film and the product thereof. Background Technology

[0002] Dielectric capacitors are widely used in modern electronic equipment and power systems due to their ultra-high power density. Polymer dielectric materials, with their advantages of good processability and high breakdown strength, have received even greater attention. Currently, biaxially oriented polypropylene (BOPP) is the most widely used material in polymer film capacitors. However, its relatively low dielectric constant (around 2.2) and low breakdown field strength (<700 MV / m) are gradually failing to meet the high operating voltage and high power density requirements of advanced electromagnetic energy equipment, necessitating the search for new polymer dielectric materials to replace it.

[0003] To improve the energy storage density of capacitors, researchers have turned their attention to ferroelectric polymers, which possess the highest dielectric constant among polymers. Through various modification methods, such as relaxor-like phases, organic-inorganic composites, and multilayer structures, ultra-high discharge energy densities of 30.0–50.0 J / cm³ have been achieved in ferroelectric-based polymers. However, these methods are prone to high losses, including both the inherent ferroelectric losses of ferroelectric materials and the conductivity losses common in dielectric materials. This results in a charge-discharge efficiency of only 70% for ferroelectric-based polymer materials under high electric fields, far lower than that of the benchmark material BOPP, making it unsuitable for continuous charge-discharge applications as capacitor materials. Therefore, there is an urgent need for a ferroelectric-based polymer material that can synergistically improve both discharge energy density and charge-discharge efficiency. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a method for preparing an all-organic small molecule composite polymer film and a product, which solves the problems of low discharge energy density and charge-discharge efficiency of ferroelectric polymer films.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for preparing an all-organic small-molecule composite polymer film is provided, the method comprising the following steps:

[0006] A pre-prepared solution is formed by mixing a mixed solution of PVDF and PMMA with a PEEU solution.

[0007] The pre-prepared solution is cast onto a substrate, heated and dried, and then heat-treated in a vacuum environment to obtain the desired composite polymer film.

[0008] More preferably, the concentration of the solute in the mixed solution of PVDF and PMMA is 30 mg / mL to 60 mg / mL.

[0009] More preferably, the mass fraction of PEEU in the pre-prepared solution is 5% to 30%.

[0010] More preferably, the heating and drying process employs a stepped heating method, with a drying temperature range of 50℃ to 125℃.

[0011] More preferably, the heat treatment temperature is 120℃~150℃, and the holding time is greater than or equal to 2 hours.

[0012] More preferably, the mixed solution of PVDF and PMMA is obtained by mixing PVDF and PMMA powders with a polar organic solvent.

[0013] More preferably, the mass ratio of the PVDF and PMMA powder mixture is 1:1.

[0014] More preferably, the PEEU solution is obtained by dissolving PEEU powder in a polar organic solvent.

[0015] More preferably, the polar organic solvent is any one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0016] According to another aspect of the present invention, a composite polymer film prepared by the above preparation method is provided.

[0017] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0018] 1. This invention utilizes the dielectric properties and intermolecular interactions of each component to design a PVDF / PMMA / PEEU blended composite polymer system. First, by blending the amorphous linear dielectric PMMA with PVDF, the discharge properties are changed from a ferroelectric phase to a paraelectric phase, reducing inherent ferroelectric losses. At this point, the crystal form of PVDF remains unchanged. After compounding with PEEU, the interaction between polar functional groups, specifically the interaction between the CF bonds in PVDF and the ether bonds in PEEU, induces a γ-phase transformation in PVDF. This further reduces the conductivity loss of PVDF, improves insulation and breakdown field strength, and ultimately increases discharge energy density and charge / discharge efficiency.

[0019] 2. In this invention, the concentration of solute in the mixed solution of PVDF and PMMA is 30 mg / mL to 60 mg / mL to ensure that the thickness of the film prepared by casting is between 7 and 10 μm; the mass fraction of PEEU in the pre-prepared solution is 5% to 30% to prevent excessive addition of small molecules from causing the film to break.

[0020] 3. In this invention, a stepped heating drying process is adopted, with a drying temperature range of 50℃ to 125℃, followed by heat treatment at a temperature of 125℃ to 150℃. The drying temperature range is selected to dry the solvent at a suitable rate and prevent excessive porosity defects. The heat treatment temperature is selected to be higher than the drying temperature but lower than the melting temperature of the core polymer PVDF to prevent PVDF from melting and causing a decrease in film performance.

[0021] 4. The all-organic composite film prepared by this invention has uniform thickness, high breakdown field strength, and high discharge energy density, and can be used to make dielectric energy storage devices to meet the requirements of advanced electromagnetic energy equipment for high discharge energy density and rapid charging and discharging.

[0022] 5. The PVDF / PMMA / PEEU all-organic composite film prepared by this invention maintains a high dielectric constant while still having a large breakdown field strength and a high discharge energy density. Attached Figure Description

[0023] Figure 1 This is a schematic flowchart of the preparation method of the all-organic small molecule composite polymer film constructed according to a preferred embodiment of the present invention.

[0024] Figure 2 This is a graph showing the relationship between the breakdown field strength and the PEEU content of the all-organic small molecule composite polymer films in the preferred embodiments 1-5 and comparative example 3 of the present invention.

[0025] Figure 3 The all-organic small molecule composite polymer according to preferred embodiment 2 of the present invention is reacted with the products of comparative examples 1-3 in... A comparison of the dielectric constant and dielectric loss as a function of frequency.

[0026] Figure 4 This is a comparison diagram of the breakdown field strength Weibull distribution of the products of preferred embodiment 2 and comparative examples 1-3 according to the present invention.

[0027] Figure 5 The graphs show the discharge energy density and charge / discharge efficiency of the products of preferred embodiment 2 and comparative examples 1-3 as a function of electric field; wherein, (a) corresponds to the discharge energy density as a function of electric field, and (b) corresponds to the charge / discharge efficiency as a function of electric field.

[0028] Figure 6 This is a comparison chart of the discharge energy density of the products of preferred embodiment 2 and comparative examples 1-3 of the present invention when the charge-discharge efficiency is 90%.

[0029] Figure 7 The X-ray diffraction of the products according to the preferred embodiment 2 and comparative examples 1-3 of the present invention is shown.

[0030] Figure 8 These are the infrared spectra of the products of preferred embodiment 2 and comparative examples 1-3 of the present invention at different wavenumbers; wherein, (a) corresponds to a wavenumber range of 770 cm⁻¹. -1 ~820 cm -1 (b) corresponds to a wavenumber interval of 1040 cm. -1 ~980 cm -1 .

[0031] Figure 9 This is a graph showing the relationship between the relative molecular mass and molecular concentration of PEEU used in this invention.

[0032] Figure 10 These are the TGA and DSC curves of the small molecule PEEU of the present invention, wherein (a) is the TGA curve and (b) is the DSC curve. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] like Figure 1 As shown, a method for preparing an all-organic small-molecule composite polymer film includes the following steps:

[0035] S1. PVDF and PMMA are mixed in equal mass ratio and dissolved in a polar solvent to construct a PVDF / PMMA blend system. The amorphous linear dielectric PMMA is used to make the dielectric properties of PVDF exhibit linear dielectric properties, thereby reducing the ferroelectric loss in PVDF.

[0036] Furthermore, the mass ratio of PVDF to PMMA is 1:1.

[0037] Furthermore, the polar organic solvent is any one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0038] Furthermore, the polymer solution was prepared with a concentration of 40 mg / mL, and the stirring time was 8 h to 12 h, while the stirring temperature was 15 °C to 70 °C.

[0039] S2, dissolve PEEU powder in a polar organic solvent and stir thoroughly to obtain a homogeneous organic small molecule solution.

[0040] Furthermore, the concentration of solute in the prepared PEEU organic small molecule solution is 30-60 mg / mL, the stirring time is 2-4 h, and the stirring temperature is 15 °C ~ 70 °C.

[0041] Furthermore, such as Figure 9 As shown, the small-molecule PEEUs used in this invention have a relative molecular mass between 631 and 1585. Due to this relatively low molecular weight, although the small-molecule PEEUs used in this invention have the same monomer composition as the large-molecule PEEUs, they are not the same substance. The PEEUs used in this invention do not possess good thermal stability, as clearly demonstrated by their thermal analysis results. (The following text is incomplete and requires further context.) Figure 10 (a) in the figure is the TGA curve of small molecule PEEU. When the temperature reaches 250 °C, small molecule PEEU has begun to decompose, and its mass is only 98% of the initial mass. Figure 10 (b) is the DSC curve of small molecule PEEU, which shows that small molecule PEEU does not exhibit any glass transition behavior in the range of -40 ℃ to 200 ℃.

[0042] Furthermore, the polar organic solvent is any one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0043] S3. PEEU solution is added to the PVDF / PMMA mixed solution and stirred for composite. PEEU with good insulation properties is added to the PVDF / PMMA system to construct a PVDF / PMMA / PEEU blend composite system. The interaction between the polar functional groups in PEEU and CF in PVDF induces a phase transformation of PVDF, further reducing the conductivity loss of PVDF / PMMA under high field. This results in PVDF / PMMA / PEEU having both a large breakdown field strength and high charge / discharge efficiency.

[0044] Furthermore, the mass fraction of PEEU in the two solutions after mixing in steps S1 and S2 is 5% to 30%.

[0045] Furthermore, the mixing and compounding time is 2 h to 4 h, and the mixing temperature is 15 °C to 70 °C.

[0046] S4. The composite polymer solution is cast onto a glass substrate, the solvent is dried by heating, and then further heat-treated in a vacuum environment to obtain a PVDF / PMMA / PEEU film. The film thickness is in micrometers.

[0047] Furthermore, the heating and drying of the solvent and the heat treatment under vacuum are carried out in different heating furnaces. Specifically, the heating and evaporation of the solvent is carried out in the first heating furnace at 50 °C to 70 °C for 4 to 8 hours. At this temperature and time, the evaporation rate of the polar solvent is suitable to ensure that the solvent is dried. Then, it is heated to 85-105 °C and held, then heated to less than 125 °C and held, and then cooled to room temperature with the furnace. The solvent is finally removed in the form of gradient heating to ensure the performance of the film. The heating and annealing under vacuum is carried out in the second heating furnace at 125 °C to 150 °C. The temperature should be kept above the melting temperature of PVDF for more than 2 hours, and then cooled to room temperature with the furnace.

[0048] The present invention will be further described below with reference to specific embodiments.

[0049] Example 1

[0050] (1) Add 0.15 g of PVDF particles and 0.15 g of PMMA particles to 10 mL of NMP solution to prepare a PVDF / PMMA blend solution with a concentration of 30 mg / mL, and stir at 500 rpm / min for 12 h at 40 °C;

[0051] (2) Add 0.02 g of PEEU powder to 0.5 mL of NMP solution to prepare a solution with a concentration of 40 mg / mL. Stir at 500 rpm / min for 2 h;

[0052] (3) Add the PEEU solution to the PVDF / PMMA blend solution, wherein the mass fraction of PEEU in the mixed solution is 5%, and stir at 500 rpm / min for 8 h at 40 °C;

[0053] (4) After thorough mixing, the PVDF / PMMA / PEEU solution is cast onto the glass surface and kept at 50 °C for 4 h. Then it is heated to 85 °C and kept at 1 h. Then it is heated to 125 °C and kept at 1 h. Then it is cooled to room temperature in the furnace. Then it is heated and annealed in a vacuum environment, heated to 120 °C and kept at 2 h. Then it is cooled to room temperature in the furnace.

[0054] Example 2

[0055] (1) Add 0.2 g of PVDF particles and 0.2 g of PMMA particles to 10 mL of NMP solution to prepare a PVDF / PMMA blend solution with a concentration of 40 mg / mL, and stir at 500 rpm / min for 12 h at 40 °C;

[0056] (2) Add 0.04 g of PEEU powder to 1 mL of NMP solution to prepare a solution with a concentration of 40 mg / mL, and stir at 500 rpm / min for 2 h at 40°C;

[0057] (3) Add the PEEU solution to the PVDF / PMMA blend solution, wherein the mass fraction of PEEU in the mixed solution is 10%, and stir at 500 rpm / min for 8 h at 40 °C;

[0058] (4) After thorough mixing, the PVDF / PMMA / PEEU solution is cast onto the glass surface and kept at 60 °C for 6 h. Then it is heated to 95 °C and kept at 1 h. Then it is heated to 125 °C and kept at 1 h. Then it is cooled to room temperature in the furnace. Then it is heated and annealed in a vacuum environment, heated to 135 °C and kept at 3 h. Then it is cooled to room temperature in the furnace.

[0059] Example 3

[0060] (1) Add 0.225 g of PVDF particles and 0.225 g of PMMA particles to 10 mL of NMP solution to prepare a PVDF / PMMA blend solution with a concentration of 45 mg / mL, and stir at 500 rpm / min for 12 h at 40 °C;

[0061] (2) Add 0.0675 g of PEEU powder to 1.5 mL of NMP solution to prepare a solution with a concentration of 40 mg / mL. Stir at 500 rpm / min for 2 h;

[0062] (3) Add the PEEU solution to the PVDF / PMMA blend solution, wherein the mass fraction of PEEU in the mixed solution is 15%, and stir at 500 rpm / min for 8 h at 40 °C;

[0063] (4) After thorough mixing, the PVDF / PMMA / PEEU solution is cast onto the glass surface and kept at 70 °C for 8 h. Then it is heated to 105 °C and kept at 1 h, then heated to 125 °C and kept at 1 h. After that, it is cooled to room temperature in the furnace. Then it is heated and annealed in a vacuum environment, heated to 140 °C and kept at 3.5 h. After that, it is cooled to room temperature in the furnace.

[0064] Example 4

[0065] (1) Add 0.2 g of PVDF particles and 0.2 g of PMMA particles to 10 mL of NMP solution to prepare a PVDF / PMMA blend solution with a concentration of 40 mg / mL, and stir at 500 rpm / min for 12 h at 40 °C;

[0066] (2) Add 0.08 g of PEEU powder to 2 mL of NMP solution to prepare a solution with a concentration of 40 mg / mL, and stir at 500 rpm / min for 2 h at 40°C;

[0067] (3) Add the PEEU solution to the PVDF / PMMA blend solution, wherein the mass fraction of PEEU in the mixed solution is 20%, and stir at 500 rpm / min at 40 °C for 8 h.

[0068] (4) After thorough mixing, the PVDF / PMMA / PEEU solution is cast onto the glass surface and kept at 50 °C for 8 h. Then it is heated to 105 °C and kept at 1 h, then heated to 125 °C and kept at 1 h. After that, it is cooled to room temperature in the furnace. Then it is heated and annealed in a vacuum environment, heated to 140 °C and kept at 4 h. After that, it is cooled to room temperature in the furnace.

[0069] Example 5

[0070] (1) Prepare a PVDF / PMMA blend solution with a concentration of 60 mg / mL by adding 0.3 g of PVDF particles and 0.3 g of PMMA particles to 10 mL of NMP solution. Stir at 500 rpm / min for 12 h;

[0071] (2) Add 0.18 g of PEEU powder to 3 mL of NMP solution to prepare a solution with a concentration of 40 mg / mL, and stir at 500 rpm / min for 2 h at 40°C;

[0072] (3) Add the PEEU solution to the PVDF / PMMA blend solution, wherein the mass fraction of PEEU in the mixed solution is 30%, and stir at 500 rpm / min at 40 °C for 8 h.

[0073] (4) After thorough mixing, the PVDF / PMMA / PEEU solution is cast onto the glass surface and kept at 50 °C for 8 h. Then it is heated to 105 °C and kept at 1 h, then heated to 125 °C and kept at 1 h. After that, it is cooled to room temperature in the furnace. Then it is heated and annealed in a vacuum environment, heated to 150 °C and kept at 2.5 h. After that, it is cooled to room temperature in the furnace.

[0074] Comparative Example 1: 0.4 g of PVDF particles were added to 10 mL of NMP solution to prepare a solution with a concentration of 40 mg / mL. The solution was stirred at 500 rpm / min for 12 h at 40 °C until thoroughly mixed. The solution was then cast onto a glass surface. The furnace was kept at the lower temperature for 8 hours, then heated to 105 °C and kept at that temperature for 1 hour, then heated to 125 °C and kept at that temperature for 1 hour, and then cooled to room temperature in the furnace. Subsequently, it was heated and annealed in a vacuum environment, heated to 125 °C and kept at that temperature for 2 hours, and then cooled to room temperature in the furnace.

[0075] Comparative Example 2: 0.4 g of PMMA particles were added to 10 mL of NMP solution to prepare a solution with a concentration of 40 mg / mL. The solution was stirred at 500 rpm / min for 12 h at 40 °C until thoroughly mixed. The solution was then cast onto a glass surface. The furnace was kept at the lower temperature for 8 hours, then heated to 105 °C and kept at that temperature for 1 hour, then heated to 125 °C and kept at that temperature for 1 hour, and then cooled to room temperature in the furnace. Subsequently, it was heated and annealed in a vacuum environment, heated to 125 °C and kept at that temperature for 2 hours, and then cooled to room temperature in the furnace.

[0076] Comparative Example 3: 0.2 g of PVDF particles and 0.2 g of PMMA particles were added to 10 mL of NMP solution to prepare a PVDF / PMMA blend solution with a concentration of 40 mg / mL. The mixture was stirred at 500 rpm / min for 12 h at 40 °C. After thorough mixing, the PVDF / PMMA solution was cast onto a glass surface and kept at 50 °C for 8 h, then heated to... Hold at this temperature for 1 hour, then heat to 125 °C and hold for 1 hour, followed by furnace cooling to room temperature; then anneal in a vacuum environment, heating to 125 °C and holding for 2 hours, followed by furnace cooling to room temperature.

[0077] Table 1. Comparison of breakdown field strength and discharge energy density at 90% charge / discharge efficiency for the products of Examples 1-5 and Comparative Examples 1-3

[0078]

[0079] Figure 2 In the breakdown field strength results of Examples 1-5 and Comparative Example 3, it is shown that the thin film has the best energy storage performance when the mass ratio of PEEU added is 10%. As shown in Table 1, the breakdown field strength of the product of Example 2 is as high as 975 MV / m.

[0080] Figure 3In the dielectric constant results of the products of Example 2 and Comparative Examples 1-3, it was found that after adding a linear dielectric with a low dielectric constant and an organic small molecule, Example 2 maintained a dielectric constant of 6.71 (at 1 kHz) while reducing the dielectric loss to 1.5%, effectively reducing the inherent ferroelectric loss of the ferroelectric polymer.

[0081] Figure 4 In the Weibull distribution results of the breakdown field strength of the products of Example 2 and Comparative Examples 1-3, it is shown that the dielectric breakdown of Example 2 will occur under a higher electric field. Compared with Comparative Example 3, the insulation and breakdown field strength of Example 2 are significantly improved after the addition of PEEU small molecules.

[0082] Figure 5 The dielectric energy storage performance results of the products in Example 2 and Comparative Examples 1-3 show that the discharge energy density and charge / discharge efficiency of Example 2 are much higher than those of Comparative Examples 1-3. Under an electric field of 950 MV / m, the discharge energy density is 27.2 J / cm². 3 The charge-discharge efficiency remains at 71%, which is higher than that of currently known ferroelectric polymers, indicating that the addition of PEEU effectively suppresses the conductivity loss of PVDF under high electric field.

[0083] Figure 6 The discharge energy density results of the products in Example 2 and Comparative Examples 1-3 at 90% charge-discharge efficiency show that Example 2 achieves a discharge energy density of 11.5 J / cm² at 90% charge-discharge efficiency. 3 Compared with the discharge energy density of Comparative Examples 1-3, there is an order of magnitude improvement.

[0084] Figure 7 and Figure 8 Based on structural characterization, the introduction of the amorphous polymer PMMA and the organic small molecule PEEU explains the structural changes of PVDF in the composite system. Figure 7 In the X-ray diffraction results of Example 2 and Comparative Examples 1-3, it was found that the structure of Comparative Example 1 was that of PVDF. γ The phase structure is as follows: Comparative Example 2 is an amorphous polymer, and Comparative Example 3 has the structure of PVDF. γ Phase structure. Compared to Comparative Example 1, the peak intensity of Comparative Example 3 decreased, but the structure remained unchanged. This indicates that the addition of PMMA disrupted the ordered structure in Comparative Example 1, resulting in a decrease in crystallinity, but did not alter the original crystal structure of PVDF. However, after the addition of PEEU, the PVDF in Example 2 transformed into a paraelectric phase structure. α The structure explains why the addition of PEEU reduces ferroelectric losses in PEEU.

[0085] Figure 8In the infrared spectral results of Examples 2 and Comparative Examples 1-3, it is found that... Figure 8 In (a) of the above, Example 2 shows obvious... α Phase absorption peaks were observed in Comparative Example 1, while those in Comparative Example 1 showed a significant difference. γ Phase absorption peaks, and Figure 6 The X-ray diffraction results in the samples corroborate each other; Figure 8 In (b) of Example 2, the COC absorption peak shows a significant shift compared to the absorption peak in PEEU. This indicates that the benzene ring in PEEU rotates after the addition of PEEU, which is a possible reason for the structural transformation of PVDF.

[0086] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an all-organic small-molecule composite polymer film, characterized in that, The preparation method includes the following steps: A pre-prepared solution is formed by mixing a mixed solution of PVDF and PMMA with a PEEU solution, wherein the PEEU in the PEEU solution is a small molecule with a relative molecular mass of 631 to 1585. The pre-prepared solution is cast onto a substrate, heated and dried, and then heat-treated in a vacuum environment to obtain the desired composite polymer film. The heating and drying process involves first heating to 50 °C ~ 70 °C and holding for 4 h ~ 8 h, then heating to 85-105 °C and holding, then heating to less than 125 °C and holding, followed by furnace cooling to room temperature. The heat treatment process involves heating to 125 °C ~ 150 °C in a vacuum environment, holding for more than or equal to 2 h, and then furnace cooling to room temperature.

2. The method for preparing an all-organic small-molecule composite polymer film as described in claim 1, characterized in that, The concentration of solute in the mixed solution of PVDF and PMMA is 30 mg / mL to 60 mg / mL.

3. The method for preparing an all-organic small-molecule composite polymer film as described in claim 1, characterized in that, The PVDF and PMMA mixed solution is obtained by mixing PVDF and PMMA powders with a polar organic solvent.

4. The method for preparing an all-organic small-molecule composite polymer film as described in claim 3, characterized in that, The mass ratio of the PVDF and PMMA powders is 1:

1.

5. The method for preparing an all-organic small-molecule composite polymer film as described in claim 4, characterized in that, The PEEU solution is obtained by dissolving PEEU powder in a polar organic solvent.

6. The method for preparing an all-organic small-molecule composite polymer film as described in claim 5, characterized in that, The polar organic solvent is any one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

7. A composite polymer film prepared by any one of claims 1-6.

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