A fluorine-doped ferroelectric polymer, film, preparation method and application thereof

Abstract

The present invention discloses a fluorine-containing ferroelectric polymer doped with ultra-low content two-dimensional nanofiller, a film and its preparation method and application, wherein the film comprises a fluorine-containing ferroelectric polymer doped with two-dimensional nanofiller, comprising: a fluorine-containing polymer and a two-dimensional nanofiller, and the doping amount of the two-dimensional nanofiller is 0.01-0.75wt%. The preparation method of the film comprises: preparing a ferroelectric polymer composite slurry doped with two-dimensional nanofiller; uniformly coating the slurry on a glass substrate, baking in a 50-80°C oven to volatilize the solvent; placing the glass substrate after the solvent is volatilized in a vacuum oven, heat-treating at 100-140°C for 10-24h, and removing the solvent; placing the doped ferroelectric polymer film containing the glass substrate substrate in deionized water for stripping, and placing the film taken out in a vacuum oven for high-temperature drying to remove moisture, the drying temperature being 100-140°C to obtain a film. The present invention is a film prepared by doping ultra-low content two-dimensional nanofiller with a fluorine-containing polymer and a doping amount of 0.01-0.75wt%, with excellent electrical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric material and piezoelectric material preparation, in particular to a fluorine-containing ferroelectric polymer doped with ultra-low content two-dimensional nanofiller, a film, and a preparation method and application thereof. Background Art

[0002] Ferroelectric polymers possess spontaneous polarization, and this polarization direction can be reversed under the influence of an external electric field, thus endowing them with numerous unique functional properties. Ferroelectric polymers possess ferroelectricity in addition to piezoelectricity, electrostriction, pyroelectricity, electrocaloric effect, and electrorefractive properties. Consequently, ferroelectric polymers have a wide range of applications, including: ultrasound imaging and sensors based on their excellent piezoelectricity; actuators based on their electrostriction; capacitors and memory devices based on their polarization properties; data storage devices, filters, and optical deflectors based on their electro-optical properties; and electrocaloric cooling devices based on their electrocaloric effect. Currently, the most widely used ferroelectric polymers are PVDF-based fluoropolymers, including polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)), and polyvinylidene fluoride-trifluoroethylene-chlorovinylidene fluoride terpolymer (P(VDF-TrFE-CFE)).

[0003] However, ferroelectric polymers currently face numerous challenges that need to be addressed. In dielectric capacitors based on their dielectric properties, the large remanent polarization of ferroelectric polymers leads to low charge and discharge efficiency. While relaxor ferroelectric P(VDF-TrFE-CFE) has significantly reduced remanent polarization and improved charge and discharge efficiency through a crystal domain nanoscaling strategy, its low breakdown field and premature polarization saturation limit energy density gains. In flexible sensors based on piezoelectric properties, ferroelectric polymers offer inherent advantages in wearable devices and biomedical applications due to their flexibility and biocompatibility compared to mainstream piezoelectric ceramics such as lead zirconate titanate (PZT). However, their low piezoelectric coefficient limits their practical applications, presenting a key challenge. In actuators based on their electrostrictive properties, ferroelectric polymers currently require high driving electric fields, even approaching their breakdown fields, to generate large electrostrain, severely limiting the actuator's service life. Improving electrostrain at low electric fields is a key issue facing ferroelectric polymer actuators.

[0004] To address these challenges, the present invention proposes a simple interface engineering method based on ultra-low-content two-dimensional nanofiller doping and modification to manipulate intermolecular interactions in fluoropolymers, inducing the formation of polar crystalline phases. This method increases the polar crystalline phase content of the original fluoropolymer film, thereby improving its dielectric constant, piezoelectric coefficient, electrostriction coefficient, and discharge energy density. This method provides new insights into the structural and morphological customization of fluoropolymers, holds significant promise for applications in capacitors, piezoelectricity, and electrostriction, and paves the way for their industrial deployment in next-generation wearable devices and human-machine interfaces. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a fluorine-containing ferroelectric polymer doped with ultra-low content two-dimensional nanofillers, a film, and a preparation method and application thereof to solve the problems raised in the above technical background.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, the present invention provides a fluoropolymer doped with an ultra-low content of two-dimensional nanofillers, the main components of which are as follows:

[0008] (1) Fluoropolymer, the fluorine-containing polymer is selected from one of ferroelectric polymers having ferroelectricity, such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)), polyvinylidene fluoride-trifluoroethylene-chlorovinylidene fluoride terpolymer (P(VDF-TrFE-CFE)), and polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer (P(VDF-TrFE-CTFE)).

[0009] (2) Two-dimensional nanofillers, the two-dimensional nanofillers being selected from graphene oxide (GO), transition metal carbides and nitrides (MXenes), montmorillonite nanosheets, and transition metal chalcogenides, which have at least one of amino (-NH2), carboxyl (-COOH), and hydroxyl (-OH) functional groups on their surfaces. Furthermore, the two-dimensional nanomaterial has 1-10 layers, preferably 1-3 layers.

[0010] (3) Doping amount of two-dimensional nanofiller. The doping amount of two-dimensional nanofiller is 0.01~0.75wt%. For P(VDF-TrFE) doped graphene oxide (GO), the doping amount ranges from 0.05-0.75wt%, preferably 0.1wt%. For P(VDF-TrFE) doped MXenes, the doping amount ranges from 0.05-0.75wt%, preferably 0.1-0.2wt%. For P(VDF-TrFE-CFE) doped graphene oxide (GO), the doping amount ranges from 0.01-0.05wt%, preferably 0.01wt%.

[0011] In a second aspect, the present invention provides a composite polymer film comprising the fluoropolymer doped with an ultra-low content of two-dimensional nanofillers as described in the first aspect. The present invention primarily aims to increase the polar crystalline phase content, dielectric constant, piezoelectric coefficient, and discharge energy density of the fluoropolymer film.

[0012] In a third aspect, the present invention further provides a process for preparing a composite polymer film, comprising the following steps:

[0013] S1. Place a certain amount of fluorine-containing ferroelectric polymer in a polar organic solvent, heat under magnetic stirring for 2-10 hours, preferably 4 hours, to fully dissolve it, and filter to obtain a clear and transparent ferroelectric polymer solution A. Disperse a certain amount of two-dimensional nanofiller in a certain amount of the same organic solvent and disperse it using ultrasound for 0.5-2 hours, preferably 0.5 hours, to obtain solution B. Combine solutions A and B and sequentially disperse them using ultrasound and stirring to prepare a ferroelectric polymer composite slurry doped with two-dimensional nanofiller.

[0014] S2. The slurry is evenly coated on a substrate (eg, a glass substrate) and baked in an oven at 50-80°C for a certain period of time to fully evaporate the organic solvent;

[0015] S3. After the solvent is evaporated, the substrate is placed in a vacuum oven and heat treated at 100-140 ° C, preferably 120 ° C for 10-24 hours to fully remove the organic solvent;

[0016] S4. Place the above-mentioned doped ferroelectric polymer film containing the substrate into deionized water for demolding, and place the demolded film into a vacuum oven for high-temperature drying to fully remove moisture. The drying temperature is 100°C-140°C, preferably 120°C, to obtain a ferroelectric polymer film doped with two-dimensional nanofillers, that is, a composite polymer film.

[0017] Preferably, the polar organic solvent in step S1 is selected from one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and N-methylpyrrolidone (NMP).

[0018] Preferably, the doped ferroelectric polymer film containing the base substrate obtained in step S3 is subjected to high-temperature annealing or quenching treatment in a vacuum oven as required to further regulate the crystal phase structure and crystal content in the ferroelectric polymer; wherein:

[0019] (a) Annealing: The doped ferroelectric polymer film containing the substrate is annealed in a vacuum oven at 170-200° C., preferably 180° C., for 1-5 hours, preferably 2 hours, and then cooled naturally to room temperature.

[0020] (b) Quenching: The doped ferroelectric polymer film containing the substrate is annealed in a vacuum oven at 170-200°C, preferably 180°C, for 5-30 minutes, preferably 10 minutes, and then quickly removed from the high temperature and placed in an ice water bath for quenching.

[0021] Preferably, the doped ferroelectric polymer film obtained in step S4 is subjected to high-temperature and high-pressure annealing or quenching treatment in a hot press as required to further regulate the crystal phase structure and crystal content in the ferroelectric polymer; wherein:

[0022] (a) Hot Press Annealing: The doped ferroelectric polymer film is hot pressed at 160-180°C, preferably 165°C, for 5-15 minutes, preferably 10 minutes, at a pressure of 5-10 MPa, preferably 7.5 MPa, and then cooled naturally to room temperature.

[0023] (b) Hot Pressing Quenching Treatment: The doped ferroelectric polymer film is hot pressed at 160-180°C, preferably 165°C, for 5-15 minutes, preferably 10 minutes, at a pressure of 5-10 MPa, preferably 7.5 MPa. The pressure is then maintained and the film is rapidly cooled to room temperature using condensed water circulation.

[0024] In a fourth aspect, the present invention further provides the use of the above-mentioned film and the film prepared by the above-mentioned method for preparing a composite polymer film in capacitors, piezoelectric and electrostrictive sensors.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention dopes a fluorine-containing polymer (specifically a polyvinylidene fluoride-trifluoroethylene binary copolymer (P(VDF-TrFE)) or a polyvinylidene fluoride-trifluoroethylene-chlorovinylidene fluoride terpolymer (P(VDF-TrFE-CFE)) with an ultra-low content of surface-functionalized two-dimensional nanofiller, with the doping amount being 0.01-0.75wt%. The resulting film has excellent electrical properties, such as a high dielectric constant, a high piezoelectric coefficient, and a high discharge energy density.

[0027] 2. The two-dimensional nanofiller used in the present invention is one of graphene oxide (GO), transition metal carbides and nitrides (MXenes), montmorillonite nanosheets, and transition metal chalcogenides. The surface of the two-dimensional nanofiller is rich in at least one of the following functional groups: amino (-NH2), carboxyl (-COOH), and hydroxyl (-OH), which can form hydrogen bonds with C—F bonds. Furthermore, the two-dimensional nanomaterial has 1-10 layers, preferably 1-3 layers.

[0028] 3. The doping level of the two-dimensional nanofiller in this invention is extremely low, ranging from 0.01 to 0.75 wt%. Unlike existing techniques that utilize the inherent physical properties of nanofillers to enhance composite material performance, the primary function of the nanofiller in this invention is to utilize its interaction with the ferroelectric polymer molecular chains to regulate the molecular chain conformation and crystal form of the ferroelectric polymer, thereby controlling its electrical properties.

[0029] 4. Based on the doping of two-dimensional nanofillers, the present invention uses a quenching or annealing process to further regulate the molecular chain conformation and crystal structure of the ferroelectric polymer to further improve the electrical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The dielectric spectra of the composite polymer films obtained in Example 1 and Comparative Example 1 of the present invention are shown;

[0031] Figure 2 Graphs showing the piezoelectric coefficients of the composite polymer films obtained in Example 1, Comparative Example 1, and Examples 3-6 of the present invention;

[0032] Figure 3 The dielectric spectra of the composite polymer films obtained in Example 2 and Comparative Example 1 of the present invention are shown;

[0033] Figure 4 The dielectric spectra of the composite polymer films obtained in Examples 3-6 and Comparative Examples 2-5 of the present invention are shown;

[0034] Figure 5 Graphs of discharge energy density and efficiency of the composite polymer films obtained in Example 7 and Comparative Example 6 of the present invention are shown; Graph A on the left is a graph of discharge energy density; Graph B on the right is a graph of discharge efficiency.

[0035] Figure 6 Electrostrain diagrams of the composite polymer films obtained in Example 7 and Comparative Example 6 of the present invention;

[0036] Figure 7 The electrostrain diagrams of the composite polymer films obtained in Example 1 and Comparative Example 1 of the present invention;

[0037] Figure 8 The dielectric spectra of the composite polymer films obtained in Example 7 and Comparative Example 6 of the present invention are shown;

[0038] Figure 9 Electrostrain diagrams of the composite polymer films obtained in Example 2 of the present invention and Comparative Example 1;

[0039] Figure 10 This is a test graph of the piezoelectric coefficient of the composite polymer film obtained in Example 2 of the present invention;

[0040] Figure 11The dielectric spectrum of the P(VDF-TrFE) (70 / 30)-doped hBN composite polymer film obtained in Comparative Example 7;

[0041] Figure 12 This is a piezoelectric coefficient test graph of the P(VDF-TrFE) (70 / 30) doped hBN composite polymer film obtained in Comparative Example 7. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0043] Example 1: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)(70 / 30)) doped redox graphene (GO) polymer film

[0044] The raw materials involved in the composite polymer film described in this example include PVDF-TrFE (70 / 30) (purchased from Arkema) and GO (purchased from Maclean). The surface of redox graphene (GO) is rich in carboxyl and hydroxyl groups.

[0045] The preparation steps of the composite polymer film are as follows:

[0046] 1. P(VDF-TrFE) (70 / 30) was dissolved in 5 ml of N,N-dimethylformamide (DMF) and heated with stirring for 10 hours to fully dissolve it. Filtered the mixture to obtain a clear and transparent ferroelectric polymer solution A. Two-dimensional filler GO was dispersed in 5 ml of N,N-dimethylformamide (DMF) at doping levels of 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, and 0.75 wt% for 0.5 hours to obtain solution B. Solutions A and B were combined.

[0047] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0048] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0049] 4. Place the glass sheet after the solvent is evaporated into a vacuum oven and heat-treat it at 120°C for 10 hours to continue evaporating the solvent. After natural cooling, a solidified film is obtained.

[0050] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0051] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0052] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) composite polymer film containing nanofillers prepared in this embodiment is as follows: Figure 1 As shown in Figure 2, at 1 kHz, the dielectric constant increases by 22.22% when 0.1 wt% GO is added compared to pure P(VDF-TrFE) (70 / 30). Figure 2 As shown, compared to pure P(VDF-TrFE) (70 / 30), the piezoelectric coefficient is highest when 0.1wt% GO is added, increasing by 70%. This indicates that films prepared by doping with ultra-low content (e.g., 0.1wt%) of surface-functionalized two-dimensional nanofiller GO significantly enhance piezoelectric and electrostrictive properties, and possess excellent electrical properties. Unlike existing technologies that utilize the inherent physical properties of nanofillers to enhance composite material performance, the primary function of the nanofiller in this invention is to utilize its interaction with the ferroelectric polymer molecular chains to regulate the molecular chain conformation and crystal form of the ferroelectric polymer, thereby regulating its electrical properties.

[0053] Electrostrain Figure 7 As shown in the figure, under the conditions of 150MV / m and 1Hz, the strain of the composite film doped with 0.1wt% GO is increased from 2.22% to 2.65% compared with the original P(VDF-TrFE)(70 / 30).

[0054] Example 2: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)(70 / 30)) doped two-dimensional material Mxene polymer film

[0055] The raw materials involved in the composite polymer film described in this embodiment include P(VDF-TrFE) (70 / 30) (purchased from Arkema) and MXene (purchased from Foshan Xinen Technology Co., Ltd.).

[0056] The preparation steps of the composite polymer film are as follows:

[0057] 1. P(VDF-TrFE) (70 / 30) was placed in 5 ml of N,N-dimethylformamide (DMF) and heated with stirring for 10 hours to fully dissolve it. The mixture was then filtered to obtain a clear and transparent ferroelectric polymer solution A. Two-dimensional MXene fillers were dispersed in 5 ml of N,N-dimethylformamide (DMF) at doping levels of 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, and 0.75 wt% for 0.5 hours to obtain solution B. Solutions A and B were combined.

[0058] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0059] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0060] 4. Place the glass sheet after the solvent is evaporated into a vacuum oven and heat-treat it at 120°C for 10 hours to continue evaporating the solvent. After natural cooling, a solidified film is obtained.

[0061] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0062] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0063] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) composite polymer film containing nanofillers prepared in this embodiment is as follows: Figure 3 As shown in Figure 1, at 1 kHz, compared with pure P(VDF-TrFE)(70 / 30), the dielectric constant increases the most when 0.1~0.2wt% MXene is added. The dielectric constant increases by 17.78% when 0.1wt% MXene is added, and by 18.88% when 0.2wt% MXene is added. Figure 10As shown, compared to pure P(VDF-TrFE) (70 / 30), the addition of 0.3wt% MXene achieves the highest piezoelectric coefficient, a 15% increase. This indicates that films prepared by doping with ultra-low levels (e.g., 0.1-0.2wt%) of surface-functionalized two-dimensional nanofiller MXene significantly enhance piezoelectric and electrostrictive properties (dielectric constant, piezoelectric coefficient), resulting in excellent electrical properties. Unlike existing techniques that utilize the inherent physical properties of nanofillers to enhance composite material performance, the primary function of the nanofiller in this invention is to utilize its interaction with the ferroelectric polymer molecular chains to regulate the molecular chain conformation and crystal form of the ferroelectric polymer, thereby modulating its electrical properties.

[0064] Electrostrain Figure 9 As shown in the figure, under the conditions of 100MV / m and 1Hz, the strain of the composite film doped with 0.1wt% MXene increased from 1.45% to 3.68% compared with the original P(VDF-TrFE)(70 / 30).

[0065] Example 3: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)(70 / 30)) doped redox graphene (GO) polymer film, vacuum oven quenching treatment.

[0066] The raw materials involved in this example include P(VDF-TrFE) (70 / 30) and GO. PVDF-TrFE (70 / 30) was purchased from Arkema, and GO was purchased from Macklin. The surface of redox graphene (GO) is rich in carboxyl and hydroxyl groups.

[0067] The preparation steps are as follows:

[0068] 1. Dissolve P(VDF-TrFE) (70 / 30) in 5 ml of N,N-dimethylformamide (DMF) with stirring for 10 hours. Filter to obtain a clear, transparent ferroelectric polymer solution A. Disperse the two-dimensional filler GO in 5 ml of DMF at a doping level of 0.1 wt% for 0.5 hours to obtain solution B. Combine solutions A and B.

[0069] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0070] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0071] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent, and then vacuum treated at 180°C for 10 minutes to obtain a solidified film.

[0072] 5. Place the 180℃ glass sheet with the cured film into an ice water bath (0℃ deionized water). After a period of time, the film will fall off from the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0073] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0074] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) composite polymer film containing nanofillers doped with 0.1wt% GO prepared in this example is as follows Figure 4 As shown in the graph, under 1 kHz conditions, the dielectric constant of the composite polymer film doped with 0.1 wt% GO and vacuum quenched is increased by 27.7% compared with the P(VDF-TrFE) (70 / 30) subjected to vacuum quenching.

[0075] Example 4: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)(70 / 30)) doped redox graphene (GO) polymer film, vacuum oven annealing treatment.

[0076] The raw materials involved in this example include P(VDF-TrFE) (70 / 30) and GO. PVDF-TrFE (70 / 30) was purchased from Arkema, and GO was purchased from Macklin. The surface of redox graphene (GO) is rich in carboxyl and hydroxyl groups.

[0077] The preparation steps are as follows:

[0078] 1. Dissolve P(VDF-TrFE) (70 / 30) in 5 ml of N,N-dimethylformamide (DMF) with stirring for 10 hours. Filter to obtain a clear, transparent ferroelectric polymer solution A. Disperse the two-dimensional filler GO at a doping level of 0.1 wt% in 5 ml of N,N-dimethylformamide (DMF) for 0.5 hours to obtain solution B. Combine solutions A and B.

[0079] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0080] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0081] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent. Then, the glass sheet is vacuum treated at 180°C for 2 hours and then naturally cooled to obtain a solidified film.

[0082] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0083] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0084] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) containing nanofillers doped with 0.1wt% GO polymer film prepared in this example is as follows: Figure 4 As shown in the graph, under 1 kHz conditions, the dielectric constant of the composite polymer film doped with 0.1 wt% GO and vacuum annealed is increased by 33.3% compared with the P(VDF-TrFE) (70 / 30) subjected to vacuum annealing.

[0085] Example 5: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)(70 / 30)) doped redox graphene (GO) polymer film, hot pressing annealing treatment.

[0086] The raw materials involved in this example include P(VDF-TrFE) (70 / 30) and GO. PVDF-TrFE (70 / 30) was purchased from Arkema, and GO was purchased from Macklin. The surface of redox graphene (GO) is rich in carboxyl and hydroxyl groups.

[0087] The preparation steps are as follows:

[0088] 1. Dissolve P(VDF-TrFE) (70 / 30) in 5 ml of N,N-dimethylformamide (DMF) with stirring for 10 hours. Filter to obtain a clear, transparent ferroelectric polymer solution A. Disperse the two-dimensional filler GO in 5 ml of DMF at a doping level of 0.1 wt% for 0.5 hours to obtain solution B. Combine solutions A and B.

[0089] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0090] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0091] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent, and then naturally cooled to obtain a solidified film.

[0092] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0093] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0094] 7. The composite polymer film was hot-pressed at 165° C. and 7.5 MPa for 10 minutes, and then naturally cooled to room temperature to obtain a hot-pressed composite polymer film.

[0095] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) polymer film containing nanofillers doped with 0.1wt% GO prepared in this example is as follows Figure 4 As shown in the graph, under 1 kHz conditions, the dielectric constant of the composite polymer film doped with 0.1 wt% GO and subjected to hot pressing annealing was not improved compared with the P(VDF-TrFE) (70 / 30) subjected to hot pressing annealing.

[0096] Example 6: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)(70 / 30)) doped redox graphene (GO) polymer film, hot pressing and quenching treatment.

[0097] The raw materials involved in this example include P(VDF-TrFE) (70 / 30) and GO. PVDF-TrFE (70 / 30) was purchased from Arkema, and GO was purchased from Macklin. The surface of redox graphene (GO) is rich in carboxyl and hydroxyl groups.

[0098] The preparation steps are as follows:

[0099] 1. Dissolve P(VDF-TrFE) (70 / 30) in 5 ml of N,N-dimethylformamide (DMF) with stirring for 10 hours. Filter to obtain a clear, transparent ferroelectric polymer solution A. Disperse the two-dimensional filler GO at a doping level of 0.1 wt% in 5 ml of N,N-dimethylformamide (DMF) for 0.5 hours to obtain solution B. Combine solutions A and B.

[0100] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0101] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0102] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent, and then naturally cooled to obtain a solidified film.

[0103] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0104] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0105] 7. The composite polymer film was hot-pressed at 165° C. and 7.5 MPa for 10 minutes, and then rapidly cooled to room temperature at 7.5 MPa to obtain a hot-pressed composite polymer film.

[0106] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) polymer film containing nanofillers doped with 0.1wt% GO prepared in this example is as follows Figure 4 As shown in the graph, under 1 kHz conditions, the dielectric constant of the composite polymer film doped with 0.1 wt% GO and subjected to hot pressing and quenching treatment is increased by 57.8% compared with the P(VDF-TrFE) (70 / 30) subjected to hot pressing and quenching treatment.

[0107] Example 7: P(VDF-TrFE-CFE)(62 / 31 / 7) doped redox graphene (GO) polymer film

[0108] The raw materials involved in this embodiment include P(VDF-TrFE-CFE) (62 / 31 / 7) (purchased from Arkema) and GO (purchased from Maclean).

[0109] The preparation steps are as follows:

[0110] 1. Dissolve P(VDF-TrFE-CFE) (62 / 31 / 7) in 5 ml of N,N-dimethylformamide (DMF) with stirring for 10 hours to fully dissolve it. Filter and obtain a clear, transparent ferroelectric polymer solution A. Disperse the two-dimensional filler GO in 5 ml of DMF at doping levels of 0.01 wt%, 0.02 wt%, and 0.05 wt% for 0.5 hours to obtain solution B. Combine solutions A and B.

[0111] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0112] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0113] 4. Place the glass sheet after the solvent is evaporated into a vacuum oven and heat-treat it at 120°C for 10 hours to continue evaporating the solvent. After natural cooling, a solidified film is obtained.

[0114] 5. Soak the glass slide with the cured film in deionized water. After a period of time, the film will fall off the glass slide by itself. Wrap the fallen film with aluminum foil.

[0115] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0116] Implementation effect: The discharge energy density-efficiency of the P(VDF-TrFE-CFE) (62 / 31 / 7) composite polymer film containing nanofillers prepared in this embodiment is as follows: Figure 5As shown, the highest discharge energy density is achieved when 0.01wt% GO is added. Compared with P(VDF-TrFE-CFE) (62 / 31 / 7), the maximum discharge energy density is increased by 34.55% (not at the same electric field strength, but by comparing the maximum energy density achieved by each sample). The charge and discharge efficiency at each electric field is significantly improved. For example, the charge and discharge efficiency corresponding to 200MV / m is increased by 21.73%. This shows that films prepared by doping with ultra-low content (e.g., 0.01wt%) of surface-functionalized two-dimensional nanofiller GO significantly improve discharge energy density and charge and discharge efficiency, and have excellent electrical properties. Unlike existing technologies that use the physical properties of nanofillers to improve composite material performance, the primary function of the nanofillers in this invention is to utilize their interaction with the ferroelectric polymer molecular chains to regulate the molecular chain conformation and crystal form of the ferroelectric polymer, thereby controlling its electrical properties.

[0117] Electrostrain Figure 6 As shown in the figure, under the conditions of 150MV / m and 1Hz, the strain of the composite film doped with 0.01wt% GO is increased from 6.81% to 8.94% compared with the original P(VDF-TrFE-CFE)(62 / 31 / 7)(70 / 30).

[0118] Comparative Example 1: Preparation process and properties of pure polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE (70 / 30)) film

[0119] The raw materials involved in this embodiment include PVDF-TrFE (70 / 30).

[0120] The preparation steps are as follows:

[0121] 1. Add P(VDF-TrFE) (70 / 30) to 10 ml of N,N-dimethylformamide (DMF) to prepare a solution.

[0122] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0123] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0124] 4. Place the glass sheet after the solvent is evaporated into a vacuum oven and heat-treat it at 120°C for 10 hours to continue evaporating the solvent. After natural cooling, a solidified film is obtained.

[0125] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0126] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0127] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) polymer film prepared in this comparative example is as follows: Figure 1 The piezoelectric coefficient is shown as Figure 2 shown.

[0128] Comparative Example 2: Preparation process and properties of pure polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE (70 / 30)) film vacuum quenching

[0129] The preparation steps are as follows:

[0130] 1. Add P(VDF-TrFE) (70 / 30) to 10 ml of N,N-dimethylformamide (DMF) to prepare a solution.

[0131] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0132] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0133] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent, and then vacuum treated at 180°C for 10 minutes to obtain a solidified film.

[0134] 5. Soak the 180°C glass sheet with the cured film in deionized water (0°C). After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0135] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0136] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) polymer film prepared in this comparative example is as follows: Figure 4 shown.

[0137] Comparative Example 3: Preparation process and properties of pure polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE (70 / 30)) film vacuum annealing

[0138] The preparation steps are as follows:

[0139] 1. Add P(VDF-TrFE) (70 / 30) to 10 ml of N,N-dimethylformamide (DMF) to prepare a solution.

[0140] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0141] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0142] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent. Then, the glass sheet is vacuum treated at 180°C for 10 minutes and then naturally cooled to obtain a solidified film.

[0143] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0144] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0145] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) polymer film prepared in this comparative example is as follows: Figure 4 shown.

[0146] Comparative Example 4: Preparation process and properties of pure polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE (70 / 30)) film by hot pressing and quenching

[0147] The preparation steps are as follows:

[0148] 1. Add 0.2 g of P(VDF-TrFE) (70 / 30) to 10 ml of N,N-dimethylformamide (DMF) to prepare a solution.

[0149] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0150] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0151] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent, and then naturally cooled to obtain a solidified film.

[0152] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0153] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0154] 7. The polymer film was hot-pressed at 165° C. and 7.5 MPa for 10 minutes, and then rapidly cooled to room temperature at 7.5 MPa to obtain a hot-pressed composite polymer film.

[0155] Implementation effect: The dielectric spectrum of the P(VDF-TrFE)(70 / 30) composite film prepared in this comparative example is as follows: Figure 4 shown.

[0156] Comparative Example 5: Preparation process and properties of pure polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE (70 / 30)) film by hot pressing annealing

[0157] The preparation steps are as follows:

[0158] 1. Add P(VDF-TrFE) (70 / 30) to 10 ml of N,N-dimethylformamide (DMF) to prepare a solution.

[0159] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0160] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0161] 4. After the solvent has evaporated, the glass sheet is placed in a vacuum oven and heat treated at 120°C for 10 hours to continue evaporating the solvent, and then naturally cooled to obtain a solidified film.

[0162] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0163] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0164] 7. The composite polymer film was hot-pressed at 165° C. and 7.5 MPa for 10 minutes, and then naturally cooled to room temperature to obtain a hot-pressed composite polymer film.

[0165] Implementation effect: The dielectric spectrum of the P(VDF-TrFE) (70 / 30) polymer film prepared in this comparative example is as follows: Figure 4 shown.

[0166] Comparative Example 6: Preparation process and properties of pure P(VDF-TrFE-CFE) (62 / 31 / 7) film

[0167] The raw materials involved in this comparative example include P(VDF-TrFE-CFE) (62 / 31 / 7).

[0168] The preparation steps are as follows:

[0169] 1. Weigh 0.2 g of P(VDF-TrFE-CFE)(62 / 31 / 7) powder and add 10 ml of N,N-dimethylformamide (DMF) to prepare a solution.

[0170] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0171] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0172] 4. Place the glass sheet after the solvent is evaporated into a vacuum oven and heat-treat it at 120°C for 10 hours to continue evaporating the solvent. After natural cooling, a solidified film is obtained.

[0173] 5. Soak the glass slide with the cured film in deionized water. After a period of time, the film will fall off the glass slide by itself. Wrap the fallen film with aluminum foil.

[0174] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at 120°C for 10 hours to obtain a P(VDF-TrFE-CFE) (62 / 31 / 7) film.

[0175] Implementation effect: The discharge energy density-efficiency of the P(VDF-TrFE-CFE) (62 / 31 / 7) polymer film prepared in this comparative example is as follows: Figure 5 shown.

[0176] Comparative Example 7: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)(70 / 30)) doped hexagonal boron nitride nanosheets (hBN) polymer film.

[0177] The raw materials involved in this comparative example include P(VDF-TrFE) (70 / 30) and hexagonal boron nitride nanosheets (hBN). PVDF-TrFE (70 / 30) was purchased from Arkema, and hexagonal boron nitride nanosheets (hBN) was purchased from Macklin.

[0178] The preparation steps are as follows:

[0179] 1. Dissolve P(VDF-TrFE) in 5 ml of N,N-dimethylformamide (DMF) with stirring for 10 hours. Filter to obtain a clear, transparent ferroelectric polymer solution A. Disperse the two-dimensional filler hBN at a doping level of 0.1 wt% in 5 ml of DMF for 0.5 hours to obtain solution B. Combine solutions A and B.

[0180] 2. Heat the above solution to 45°C under magnetic stirring and dissolve and disperse for 8 hours to allow the solute to be fully and evenly dissolved in the solvent.

[0181] 3. Clean the glass slide to avoid dust contamination, then place the glass slide in a 70℃ oven to preheat for half an hour, then use a rubber-tipped dropper to draw 5ml of film-making liquid onto the glass slide, and let the glass slide be baked in a 70℃ oven for 10 hours to evaporate the solvent.

[0182] 4. Place the glass sheet after the solvent is evaporated into a vacuum oven and heat-treat it at 120°C for 10 hours to continue evaporating the solvent. After natural cooling, a solidified film is obtained.

[0183] 5. Soak the glass sheet with the cured film in deionized water. After a period of time, the film will fall off the glass sheet by itself. Wrap the fallen film with aluminum foil.

[0184] 6. Place the aluminum foil wrapped with the film in a vacuum oven and dry it at a high temperature of 120°C for 10 hours to obtain a composite polymer film.

[0185] Implementation effect: The dielectric spectrum and piezoelectric coefficient of the P(VDF-TrFE)(70 / 30) doped hBN polymer film prepared in this comparative example are as follows: Figure 11 、 Figure 12 Compared to GO, a two-dimensional filler with a rich surface rich in carboxyl and hydroxyl groups, hBN, which lacks surface carboxyl, hydroxyl, and amino groups, is extremely poor at improving the dielectric properties of fluoropolymers. The piezoelectric coefficient is not improved compared to pure P(VDF-TrFE) (70 / 30).

[0186] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A composite polymer film, characterized in that Fluorine-containing ferroelectric polymers containing ultra-low-content doped two-dimensional nanofillers; The fluorine-containing ferroelectric polymer doped with ultra-low content two-dimensional nanofiller comprises: a fluorine-containing polymer and a two-dimensional nanofiller; The fluorine-containing polymer is P(VDF-TrFE); the two-dimensional nanofiller is graphene oxide (GO) having a surface rich in at least one functional group of amino (-NH2), carboxyl (-COOH), and hydroxyl (-OH); The doping amount of two-dimensional nanofillers ranges from 0.05 to 0.75 wt%; The method for preparing the composite polymer film comprises the following steps: S1. placing a fluorine-containing ferroelectric polymer in a polar organic solvent, heating it with stirring for 2-10 hours to fully dissolve it, and filtering it to obtain a clear and transparent ferroelectric polymer solution A; dispersing the two-dimensional nanofiller in the polar organic solvent and dispersing it using ultrasound for 0.5-2 hours to obtain a solution B; combining solutions A and B in proportion, and successively performing ultrasound and stirring dispersion to prepare a two-dimensional nanofiller-doped ferroelectric polymer composite slurry; S2. The slurry obtained in step S1 is evenly coated on the substrate and baked in an oven at 50-80°C for a certain period of time to fully evaporate the organic solvent; S3. After the solvent is evaporated, the substrate is placed in a vacuum oven and heat treated at 100-140 ℃ for 10-24 hours to fully remove the organic solvent to obtain a doped ferroelectric polymer film containing a substrate substrate; S4. The doped ferroelectric polymer film containing the substrate is placed in deionized water for demolding, and the film is placed in a vacuum oven for high-temperature drying to fully remove moisture, the drying temperature is 100°C-140°C, and a ferroelectric polymer film doped with two-dimensional nanofillers is obtained. The obtained doped ferroelectric polymer film is subjected to high-temperature and high-pressure quenching treatment in a hot press to further regulate the crystal phase structure and crystal content in the ferroelectric polymer; wherein the hot pressing quenching treatment method is: hot pressing the doped ferroelectric polymer film at 160-180°C for 5-15 minutes, and the hot pressing pressure is 5-10MPa; then the pressure is maintained, and the condensed water is circulated to quickly cool to room temperature, and a composite polymer film is obtained after treatment.

2. A composite polymer film according to claim 1, characterized in that: The doping amount of the two-dimensional nanofiller is 0.1 wt%.

3. The composite polymer film according to claim 1, characterized in that: In step S1, the polar organic solvent is selected from one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and N-methylpyrrolidone (NMP).

4. The composite polymer film according to claim 1, characterized in that: The doped ferroelectric polymer film containing the base substrate obtained in step S3 is subjected to high-temperature annealing or quenching treatment in a vacuum oven to further regulate the crystal phase structure and crystal content in the ferroelectric polymer; The vacuum high temperature annealing treatment method is as follows: annealing the doped ferroelectric polymer film containing the substrate in a vacuum oven at 170-200°C for 1-5 hours, and then naturally cooling to room temperature; The vacuum high-temperature quenching treatment method is as follows: annealing the doped ferroelectric polymer film containing the base substrate in a vacuum oven at 170-200° C. for 5-30 minutes, then quickly taking it out from the high temperature and placing it in an ice water bath for quenching.

5. Use of the composite polymer film according to any one of claims 1 to 4 in capacitors, piezoelectric and electrostrictive sensors.

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