CN110283346B - Polymer film, preparation method thereof and capacitor - Google Patents

Polymer film, preparation method thereof and capacitor Download PDF

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CN110283346B
CN110283346B CN201910592399.XA CN201910592399A CN110283346B CN 110283346 B CN110283346 B CN 110283346B CN 201910592399 A CN201910592399 A CN 201910592399A CN 110283346 B CN110283346 B CN 110283346B
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polyvinylidene fluoride
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孙晓丽
王梦宇
闫寿科
李慧慧
任忠杰
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Beijing University of Chemical Technology
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    • C08J2427/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
    • C08J2427/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
    • C08J2427/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
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Abstract

The invention discloses a polymer film and a preparation method thereof, wherein the preparation method comprises the following steps: (1) attaching an oriented polyvinylidene fluoride film on a substrate to obtain an initial film; (2) applying the vinylidene fluoride-trifluoroethylene copolymer solution to an initial membrane to obtain a pretreated membrane; (3) and annealing the pre-treated film at 100-180 ℃ to obtain the polymer film. The polymer film of the present invention has excellent ferroelectric and piezoelectric properties.

Description

Polymer film, preparation method thereof and capacitor
Technical Field
The invention relates to a polymer film, a preparation method thereof and a capacitor.
Background
Ferroelectric materials can be classified into polymeric ferroelectric materials and inorganic ferroelectric materials. The research on inorganic ferroelectric materials has been early and mature, but it is not easy to bend because it is not environmentally friendly and most of them are not flexible well. The polymer ferroelectric material has the advantages of good flexibility, good processability, simple device structure, low cost, 3D stacking function and the like. The polymer material itself has excellent physical properties such as good mechanical strength and flexibility. These unique characteristics make it applicable to many high-tech fields such as memories, transistors, nano-generators, transducers, artificial retinas, etc.
Among the polymer ferroelectric materials, polyvinylidene fluoride (PVDF) and copolymers thereof have strong ferroelectricity due to the C-F bond with strong polarity. Among all ferroelectric polymers, PVDF and its copolymers are widely studied. In the PVDF monomer unit, the Van der Waals radius due to the F atom is
Figure BDA0002116472410000011
Radius of only H atoms
Figure BDA0002116472410000012
Slightly larger, F forms a strongly polar covalent bond with the C atom, resulting in a high dipole moment of 6.4 × 10-30The PVDF has α and gamma phases, wherein the β crystal form is TTTT all-trans conformation, and the β phase has high ferroelectricity, in order to improve the performance of the PVDF and adapt to the increasing technical requirements, different PVDF copolymers have been developed, polyvinylidene fluoride-trifluoroethylene (P (VDF-TrFE)) increases the unit cell size of the ferroelectric phase by introducing TrFE on the VDF main chain, has larger steric hindrance, and enables the all-trans conformation TTTT to be more easily formed, and the ferroelectric phase β phase with ferroelectricity, which is similar to the PVDF, is obtained.
CN101419886A discloses a method for manufacturing an organic polymer copolymer ferroelectric cathode emitter, which comprises depositing an electrode layer on a substrate, coating an organic copolymer P (VDF-TrFE) ferroelectric layer on the electrode layer, annealing, and depositing an electrode layer. The ferroelectric properties of the emitter are poor. CN108948390A discloses a preparation method of a PVDF-based polymer film, which comprises the steps of carrying out hydrophilic modification on a substrate, then casting a PVDF-based polymer solution on the hydrophilic modification substrate to form a liquid film, and carrying out curing treatment on the liquid film by controlling the casting temperature and the casting time, thereby obtaining the orderly-arranged PVDF-based polymer film. The polymer film obtained by the method has poor ferroelectric property. CN104409626A discloses a preparation method of a PVDF-based high-voltage coefficient film, which comprises the steps of injecting different PVDF-based organic ferroelectric polymer solutions into a liquid tank through Langmuir-Blodgett equipment to form a continuous film, then transferring the continuous film to a substrate in an alternating horizontal mode, and then annealing the grown alternating film to obtain the PVDF-based high-voltage coefficient film. The method has the advantages of complex process, high cost, and poor piezoelectric property and ferroelectric property.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a method for preparing a polymer thin film, which can obtain a flexible polymer thin film having excellent piezoelectric properties and ferroelectric properties.
It is another object of the present invention to provide a polymer thin film which is excellent in piezoelectric properties and ferroelectric properties.
It is still another object of the present invention to provide a capacitor comprising the above polymer film.
The invention provides a preparation method of a polymer film, which comprises the following steps:
(1) attaching the oriented polyvinylidene fluoride film to a substrate to obtain an initial film;
(2) applying the vinylidene fluoride-trifluoroethylene copolymer solution to an initial membrane to obtain a pretreated membrane;
(3) and annealing the pre-treated film at 100-180 ℃ to obtain the polymer film.
According to the production method of the present invention, preferably, in the step (1), the oriented polyvinylidene fluoride film is obtained by any one method selected from the group consisting of a melt-stretching method, a friction-orientation method and a blade-coating method.
According to the preparation method of the present invention, preferably, in the step (1), the thickness of the polyvinylidene fluoride film is 10 to 100 nm.
According to the preparation method of the present invention, preferably, in the step (1), the solvent of the polyvinylidene fluoride solution is one or more selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, acetonitrile and dimethylsulfoxide; the concentration of the polyvinylidene fluoride is 1-100 mg/ml.
According to the preparation method of the present invention, preferably, in the step (2), the vinylidene fluoride-trifluoroethylene copolymer solution is applied to the initial film by a spin coating method; the rotation speed is 1000-5000 rpm.
According to the preparation method of the present invention, preferably, in the step (2), the thickness of the polymer thin film is 10 to 100 nm.
According to the preparation method of the present invention, preferably, in the step (2), the solvent of the vinylidene fluoride-trifluoroethylene copolymer solution is one or more selected from N, N-dimethylformamide, N-dimethylacetamide and butanone; the concentration of the vinylidene fluoride-trifluoroethylene copolymer is 10-20 mg/ml.
According to the production method of the present invention, preferably, in the step (3), the annealing treatment includes the steps of: heating the pretreated film to 100-180 ℃ at a speed of 50-300 ℃/min, keeping the temperature for 50-100 min, and then cooling to 15-35 ℃ at a speed of 1-20 ℃/min.
The invention also provides a polymer film prepared by the preparation method.
The invention also provides a capacitor, which comprises two metal layers which are oppositely arranged and the polymer film arranged between the two metal layers.
The invention also provides the application of the double-layer ferroelectric polymer film, which can be applied to the fields of memories, sensors, nano generators, field effect transistors and the like.
The polymer film of the invention has excellent piezoelectric performance and ferroelectric performance. In addition, the polymer film of the present invention can be used for flexible organic devices. The residual polarization value Pr of the polymer film can reach 23.1 mu C/cm2Far greater than the existing polymer ferroelectric film (7-9 mu C/cm)2)。
Drawings
FIG. 1 is a schematic diagram of a motor-driven mechanical roller for producing a polyvinylidene fluoride film by a melt-stretching process.
FIG. 2a is a height map of the polymer film of example 1 for an Atomic Force Microscope (AFM) topography test.
FIG. 2b is a phase diagram of an Atomic Force Microscope (AFM) morphology test of the polymer film of example 1.
FIG. 3a is an electron micrograph of the polymer film of example 1 without annealing.
FIG. 3b is an electron micrograph of the polymer film of example 1 after annealing.
FIG. 4 is a plot of the polarized infrared spectra of the polymer film and oriented polyvinylidene fluoride film of example 1.
FIG. 5 is a grazing incidence infrared spectrum of the polymer film of example 1.
FIG. 6a is a PFM phase diagram of the polymer film of example 1.
FIG. 6b is a plot of amplitude versus bias for the polymer film of example 1.
FIG. 6c is a phase versus bias plot of the polymer film of example 1.
Fig. 7 is a hysteresis loop diagram of capacitors A, B and C.
Fig. 8 is a graph of leakage current density for capacitor a.
Detailed Description
The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.
In the present invention, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene and P (VDF-TrFE) have the same meaning and may be used interchangeably.
The preparation method of the polymer film comprises the following steps: (1) preparing an initial film; (2) preparing a pretreatment membrane; (3) annealing; optionally, a membrane bleaching step is also included. As described in detail below.
< preparation of initial Membrane step >
The preparation steps of the initial film of the invention are: preparing an oriented polyvinylidene fluoride film, and attaching the oriented polyvinylidene fluoride film to a substrate to obtain an initial film. The substrate is not particularly limited, and includes, but is not limited to, glass, crystalline silicon wafer, and metal sheet; but also glass or silicon wafers coated with a metal layer, etc. In the present invention, the oriented polyvinylidene fluoride film can be obtained by the following method: melt drawing, friction orientation or knife coating. Preferably, the oriented polyvinylidene fluoride film is obtained by a melt-stretching method or a rubbing orientation method. More preferably, the oriented polyvinylidene fluoride film is obtained by melt-stretching. The polyvinylidene fluoride film obtained by the method has good orientation. As shown in fig. 1, a polyvinylidene fluoride solution is poured on a smooth glass plate substrate with a heating plate at the bottom, and after leveling, the solvent is heated and evaporated to obtain a polymer supercooling melt film; and then, sticking and stretching the polymer supercooling melt film on the glass plate substrate by using a mechanical roller driven by a motor to obtain the high-orientation polyvinylidene fluoride film. The thickness and orientation degree of the polyvinylidene fluoride film are controlled by controlling the concentration of the polyvinylidene fluoride solution, the preheating temperature of the glass plate and the stretching speed of the mechanical roller.
The polyvinylidene fluoride solution of the present invention is formed by dissolving polyvinylidene fluoride in a solvent. The solvent is selected from one or more of N, N-dimethylformamide, N-dimethylacetamide, acetonitrile and dimethyl sulfoxide. Preferably, the solvent is selected from one or more of N, N-dimethylformamide, N-dimethylacetamide and dimethylsulfoxide. More preferably, the solvent is one or two mixed solution of N, N-dimethylformamide and N, N-dimethylacetamide. The solvent is adopted to dissolve polyvinylidene fluoride, which is beneficial to controlling crystal form and orientation degree.
The concentration of the polyvinylidene fluoride solution is 1-100 mg/ml, preferably 50-100 mg/ml, and more preferably 80-100 mg/ml. The polyvinylidene fluoride solution with the concentration range is favorable for obtaining the continuous and high-orientation polyvinylidene fluoride membrane.
In order to promote the dissolution of polyvinylidene fluoride, heating and stirring are carried out in the dissolving process, the heating temperature can be 50-150 ℃, the preferable temperature is 100-150 ℃, the more preferable temperature is 120-140 ℃, the stirring time is 1-24 hours, the preferable time is 3-10 hours, the stirring speed is 400-700 rpm, the preferable speed is 500-600 rpm, according to one embodiment of the invention, polyvinylidene fluoride (PVDF) is dispersed in N, N-dimethylformamide, and the stirring speed is 500-600 rpm at 120-140 ℃ for 3-10 hours, so that the polyvinylidene fluoride solution with the concentration of 80-100 mg/m L is obtained.
The thickness of the polyvinylidene fluoride film can be 10-100 nm, preferably 20-80 nm, and more preferably 40-60 nm. The width and length of the polyvinylidene fluoride film are not particularly limited. The width may be 5 to 30cm, preferably 10 to 20 cm. The length may be 5 to 30cm, preferably 10 to 30 cm.
< preparation of pretreatment film >
The preparation steps of the pretreatment membrane of the invention are as follows: and applying the vinylidene fluoride-trifluoroethylene copolymer solution to the initial membrane to obtain a pretreated membrane. Specifically, a vinylidene fluoride-trifluoroethylene copolymer solution is applied to an initial film in a moving state (for example, a rotating state), to obtain a pretreated film. The method for applying the vinylidene fluoride-trifluoroethylene copolymer solution to the initial film in the invention comprises but is not limited to a spin coating method and a dropping film method, and the spin coating method is preferably adopted. Spin coating can uniformly apply a vinylidene fluoride-trifluoroethylene copolymer solution to an oriented polyvinylidene fluoride film substrate. The total thickness of the polyvinylidene fluoride film and the vinylidene fluoride-trifluoroethylene copolymer film can be 100-200 nm, preferably 100-180 nm, and more preferably 100-150 nm.
And dropwise adding the vinylidene fluoride-trifluoroethylene copolymer solution onto the initial film at the rotating speed of 1000-5000 rpm, preferably 1500-4500 rpm, more preferably 2000-4000 rpm, wherein the using amount of the vinylidene fluoride-trifluoroethylene copolymer solution is 50-200 mu L, preferably 50-150 mu L, more preferably 80-150 mu L, the spin-coating time can be 0.5-3 min, preferably 0.5-2 min, more preferably 1-2 min, the spin-coating and the drying can be carried out simultaneously, the drying temperature can be 25-50 ℃, preferably 25-40 ℃, more preferably 25-35 ℃, and the drying time can be 0.5-3 min, preferably 0.5-2 min, more preferably 1-2 min.
The polyvinylidene fluoride-trifluoroethylene copolymer solution has the concentration of 10-20 mg/m L, preferably 10-17 mg/m L and more preferably 12-17 mg/m L.
In order to promote the dissolution of the vinylidene fluoride-trifluoroethylene copolymer, heating and stirring are adopted, the dissolving temperature can be 40-60 ℃, preferably 50-60 ℃, the stirring time is 1-24 hours, preferably 3-10 hours, the stirring speed is 400-700 rpm, preferably 500-600 rpm, according to one embodiment of the invention, the vinylidene fluoride-trifluoroethylene copolymer is dispersed in butanone, and the vinylidene fluoride-trifluoroethylene copolymer is stirred at the stirring speed of 500-600 rpm for 3-10 hours at the temperature of 50-60 ℃, so that a vinylidene fluoride-trifluoroethylene copolymer solution with the concentration of 12-17 mg/m L is obtained.
According to one embodiment of the invention, L vinylidene fluoride-trifluoroethylene copolymer solution with the concentration of 12-17 mg/m and the concentration of 80-150 mu L is dripped on an initial membrane, the rotating speed is 2000-4000 rpm, the spin coating time is 1-2 min, and the initial membrane is dried and formed at the temperature of 25-35 ℃ during rotation to obtain a pretreatment membrane, wherein the bottom layer of the pretreatment membrane is an oriented polyvinylidene fluoride membrane, and the top layer of the pretreatment membrane is a vinylidene fluoride-trifluoroethylene copolymer membrane.
< annealing step >
The preparation steps of the pretreatment membrane of the invention are as follows: and annealing the pre-treated film to obtain the polymer film. Specifically, the pre-treated film is annealed to form an annealed pre-treated film, and further processed to obtain a polymer thin film. And heating the pretreatment film to 100-180 ℃ for annealing treatment. Preferably, the temperature of the pretreatment film is raised to 120-160 ℃ for annealing treatment. More preferably, the annealing treatment is carried out by heating the pretreatment film to 135-145 ℃. The heating rate can be 50-300 ℃/min, preferably 100-250 ℃/min, and more preferably 150-200 ℃/min. The heat preservation time can be 50-100 min, preferably 60-90 min, and more preferably 60-80 min. The cooling rate after heat preservation can be 1-20 ℃/min, preferably 5-15 ℃/min, and more preferably 5-10 ℃/min. The temperature is reduced to 15-35 ℃, preferably 15-30 ℃, and more preferably 21-25 ℃. The thickness of the polymer film obtained through the annealing step is 100-150 nm. The structure and orientation of the polymer film crystal can be further controlled by controlling the heating rate, annealing temperature, annealing time and cooling rate, so that the polymer film with better ferroelectric property is obtained.
According to one embodiment of the invention, the temperature of the pretreatment film is raised to 135-145 ℃ at a speed of 150-200 ℃/min, the temperature is maintained for 60-80 min, then the temperature is lowered to 21-25 ℃ at a speed of 1-10 ℃/min to form the annealed pretreatment film, and the annealed pretreatment film is further processed to obtain the polymer film.
In certain embodiments, a drying step is also included prior to annealing. Drying the pretreatment membrane for 8-24 h, preferably 10-20 h, more preferably 8-12 h at 40-60 ℃, preferably 45-55 ℃, more preferably 50-55 ℃. The drying step is effective to remove residual solvent. Drying methods include, but are not limited to, hot air drying, microwave drying, ultraviolet drying, infrared drying, vacuum drying and or freeze drying; preferably hot air drying, microwave drying or infrared drying; more preferably vacuum drying. According to one embodiment of the invention, the pre-treated membrane is dried under vacuum at 45-55 ℃ for 8-12 h.
< step of Membrane bleaching >
And placing the annealed pretreatment film and the substrate in a dilute hydrofluoric acid solution for etching, then stripping the pretreatment film from the substrate, and placing the stripped film in clean water for cleaning to obtain the polymer film. The standing time of the pretreatment film in the dilute hydrofluoric acid solution can be 10-100 min, preferably 10-60 min, and more preferably 10-25 min.
< Polymer film >
The present invention also provides a polymer film, which is prepared by the above method, and is not described herein again. The polymer film has flexibility and good processing performance, and can be used for flexible organic devices. The polymer film is excellent in piezoelectric properties and ferroelectric properties. The test result shows that the residual polarization value Pr of the material can reach 23.1 mu C/cm2Far greater than the existing film of 7-9 μ C/cm2。
< capacitor >
The capacitor of the present invention includes two metal layers disposed opposite each other and a polymer film disposed between the two metal layers. The polymer film is prepared by the method. The metal layer may be a gold layer, a silver layer and an aluminum layer, preferably a gold layer and an aluminum layer, more preferably an aluminum layer. The thickness of the metal layer may be 20 to 120nm, preferably 40 to 100nm, and more preferably 60 to 80 nm.
The capacitor is prepared by the following steps:
and evaporating a layer of aluminum layer with the thickness of 60-80 nm on the glass substrate by using a vacuum evaporation method, then attaching the polymer film to the aluminum layer, and then evaporating a layer of aluminum layer with the metal thickness of 60-80 nm on the surface of the polymer film by using the vacuum evaporation method to obtain the capacitor.
< test methods >
Atomic Force Microscope (AFM) morphology testing: and (3) testing the morphology of the polymer film by adopting an Atomic Force Microscope (AFM), wherein the testing mode is a Tapping mode, and the scanning size of the height map is 5um x 5 um.
Transmission Electron Microscope (TEM) testing: the polymer films were tested using a transmission electron microscope at Jem-2100d with an acceleration voltage of 200 kV. And (3) attaching the polymer film on a copper net for testing to obtain a diffraction pattern.
Testing by a Fourier infrared spectrometer: the polymer film was tested using FTIR-650 Fourier transform Infrared Spectroscopy using two modes: the method comprises the steps of polarized infrared and glancing incidence infrared, wherein the substrates used for testing are an infrared silicon wafer substrate and a gold-plated silicon wafer substrate respectively, and the test wave band is 400-4000 cm-1Resolution of the instrument is 4cm-1。
Testing of piezoelectric performance: PFM measurements were performed using a Bruker SPM system equipped with an NSV controller lock-in amplifier, using an N-type silicon substrate coated with an Au layer as the bottom electrode and a Pt/Ir coated tip with a mechanical constant of 2.8N/m as the top electrode.
Testing of ferroelectric properties: a ferroelectric tester is adopted to characterize the ferroelectric property of the polymer film, the test waveform is bipolar wave, and the maximum test voltage is 17V.
The starting materials used in the examples are described below:
polyvinylidene fluoride: from Alfa Aesar, uk.
Vinylidene fluoride-trifluoroethylene copolymer: commercially available from ARKEMA, france, in a 7:3 molar ratio of vinylidene fluoride to trifluoroethylene in the vinylidene fluoride-trifluoroethylene copolymer.
The total thickness of the polyvinylidene fluoride membrane and the vinylidene fluoride-trifluoroethylene copolymer film is 120 nm.
Example 1
(1) The method comprises the steps of preparing a high-orientation polyvinylidene fluoride film by using the device shown in FIG. 1, dispersing polyvinylidene fluoride in N, N-dimethylformamide, stirring at the stirring speed of 600rpm for 4 hours at 120 ℃ to obtain a polyvinylidene fluoride solution with the concentration of 90mg/m L, pouring the polyvinylidene fluoride solution on a smooth glass plate substrate with a heating plate at the bottom, leveling, volatilizing the solvent under the heating of the heating plate, sticking and stretching a polymer supercooling melt film on the glass plate substrate by using a mechanical roller driven by a motor after the solvent is completely volatilized to obtain the high-orientation polyvinylidene fluoride film, and attaching the orientation polyvinylidene fluoride film on the glass substrate by using the mechanical roller driven by the motor to obtain an initial film, wherein the thickness of the initial film is 50nm, the width of the initial film is 10cm, and the length of the initial film is 10 cm..
(2) Vinylidene fluoride-trifluoroethylene copolymer (P (VDF-TrFE)) was dispersed in methyl ethyl ketone, and stirred at 60 ℃ for 5 hours at a stirring speed of 600rpm to obtain a copolymer solution having a concentration of 15mg/m L, 100. mu. L of the copolymer solution was dropped on an initial film rotating at a high speed (rotation speed of 2500rpm), spin-coated for 1min, and molded at 30 ℃ to obtain a pretreated film.
(3) And (3) drying the pretreatment film at 55 ℃ in vacuum for 12h, then heating to 140 ℃ at the heating rate of 200 ℃/min, preserving the heat for 70min, and then cooling to 25 ℃ at the cooling rate of 5 ℃/min to obtain the annealed pretreatment film.
And placing the annealed pretreatment film in a dilute hydrofluoric acid solution for etching, and stripping the pretreatment film from the glass substrate to obtain the polymer film.
FIG. 2a is a height plot of an Atomic Force Microscope (AFM) topography test of the polymer film of example 1; FIG. 2b is an Atomic Force Microscope (AFM) morphology test phase diagram of the polymer film of example 1. As can be seen, the polymer film contains many platelets arranged in the same direction, and the direction of the platelets is perpendicular to the direction of the rotation axis of the oriented film preparation process.
FIG. 3a is an electron micrograph of the polymer film of example 1 without annealing; FIG. 3b is an electron micrograph of the polymer film of example 1 after annealing. As can be seen from the diffraction points (200), (110), and (001), the upper copolymer film of the polymer film changed from a non-oriented structure to an oriented structure after the annealing treatment.
FIG. 4 is a plot of the polarized infrared spectra of the polymer film and oriented polyvinylidene fluoride film of example 1. FIG. 5 is a grazing incidence infrared spectrum of the polymer film of example 1. The characteristic infrared bands of PVDF are reported in table 1. There are three main vibration modes: the first mode is a vibrational mode parallel to the b-axis of the lattice, which is designated the a1 peak; the other two modes are vibration modes parallel to the c-axis and a-axis of the lattice, designated as B1 peak and B2 peak, respectively.
TABLE 1
Figure BDA0002116472410000121
As can be seen from FIG. 4, the molecular chain of the vinylidene fluoride-trifluoroethylene copolymer was parallel to the stretching direction. Electroactive CF2The preferential orientation of the dipoles (b-axis) and a-axis is perpendicular to the transverse zigzag chains and the stretching direction, and there are more crystals with their a-axis perpendicular to the molecular chains and at the same time parallel to the film plane. As can be seen from fig. 5, there are more crystals with molecular dipoles (parallel to the b-axis) perpendicular to the film plane.
Example 2
(1) The method comprises the steps of preparing a high-orientation polyvinylidene fluoride film by using the device shown in the figure 1, dispersing polyvinylidene fluoride in N, N-dimethylformamide, stirring at the stirring speed of 600rpm for 4 hours at the temperature of 120 ℃ to obtain a polyvinylidene fluoride solution with the concentration of 90mg/m L, pouring the polyvinylidene fluoride solution on a smooth glass plate substrate with a heating plate at the bottom, leveling, volatilizing the solvent under the heating of the heating plate, sticking and stretching a polymer supercooling melt film on the glass plate substrate by using a mechanical roller driven by a motor after the solvent is completely volatilized to obtain the high-orientation polyvinylidene fluoride film, and attaching the orientation polyvinylidene fluoride film on the glass substrate by using the mechanical roller driven by the motor to obtain an initial film, wherein the thickness of the high-orientation polyvinylidene fluoride film is 50nm, the width of the high-orientation polyvinylidene fluoride film is 10cm, and the length of the high-orientation.
(2) Vinylidene fluoride-trifluoroethylene copolymer (P (VDF-TrFE)) was dispersed in a butanone solvent, and stirred at 60 ℃ for 5 hours at a stirring speed of 600rpm to obtain a copolymer solution having a concentration of 15mg/m L, 100. mu. L of the copolymer solution was dropped on an initial film rotating at a high speed (rotation speed of 2500rpm), spin-coated for 1min, and molded at 30 ℃ to obtain a pretreated film.
(3) And (3) drying the pretreatment film at 55 ℃ in vacuum for 12h, then heating to 135 ℃ at the heating rate of 200 ℃/min, preserving the heat for 70min, and then cooling to 25 ℃ at the cooling rate of 5 ℃/min to obtain the annealed pretreatment film.
And placing the annealed pretreatment film in a dilute hydrofluoric acid solution for etching, and stripping the pretreatment film from the glass substrate to obtain the polymer film.
Example 3
(1) The method comprises the steps of preparing a high-orientation polyvinylidene fluoride film by using the device shown in the figure 1, dispersing polyvinylidene fluoride in N, N-dimethylformamide, stirring at the stirring speed of 600rpm for 4 hours at the temperature of 120 ℃ to obtain a polyvinylidene fluoride solution with the concentration of 90mg/m L, pouring the polyvinylidene fluoride solution on a smooth glass plate substrate with a heating plate at the bottom, leveling, volatilizing the solvent under the heating of the heating plate, sticking and stretching a polymer supercooling melt film on the glass plate substrate by using a mechanical roller driven by a motor after the solvent is completely volatilized to obtain the high-orientation polyvinylidene fluoride film, and attaching the orientation polyvinylidene fluoride film on the glass substrate by using the mechanical roller driven by the motor to obtain an initial film, wherein the thickness of the high-orientation polyvinylidene fluoride film is 50nm, the width of the high-orientation polyvinylidene fluoride film is 10cm, and the length of the high-orientation.
(2) Dispersing vinylidene fluoride-trifluoroethylene copolymer in butanone, stirring at 60 ℃ for 5h at a stirring speed of 600rpm to obtain a copolymer solution with the concentration of 15mg/m L, dropwise adding the 100 mu L copolymer solution on an initial film rotating at a high speed (the rotating speed is 2500rpm), carrying out spin coating for 1min, and forming at 30 ℃ to obtain a pretreated film.
(3) And (3) carrying out vacuum drying treatment on the pretreated membrane at 55 ℃ for 12h, then heating to 145 ℃ at a heating rate of 200 ℃/min, carrying out heat preservation for 70min, and then cooling to 25 ℃ at a cooling rate of 5 ℃/min to obtain the annealed pretreated membrane.
And placing the annealed pretreatment film in a dilute hydrofluoric acid solution for etching, and stripping the pretreatment film from the glass substrate to obtain the polymer film.
Experimental example 1 sample for piezoelectric Performance test
(1) Evaporating a gold layer (as a bottom electrode in a piezoelectric test) on the upper surface of the silicon wafer by using an ion sputtering instrument to form a pretreated silicon wafer;
(2) the polymer film of example 1 was attached to the surface of a pretreated silicon wafer, and the piezoelectric properties were measured.
FIG. 6a is a PFM phase diagram of the polymer film of example 1, FIG. 6b is a plot of amplitude versus bias for the polymer film of example 1, and FIG. 6c is a plot of phase versus bias for the polymer film of example 1. As can be seen from fig. 6a, the polarization reversal ferroelectric domain undergoes a direction change under the action of the external longitudinal electric field, thereby exhibiting a significant ferroelectric domain reversal phenomenon. Therefore, the polymer film of the present invention has good piezoelectric properties. From fig. 6b it can be seen that the loop exhibits a butterfly-shaped hysteresis characteristic, demonstrating the presence of longitudinal ferroelectricity in the sample. Similar information can be obtained from fig. 6c, where the phase loop plot shows that with an approximately square window, phase jumps occurred for the sample. These all show that the polymer film of the present invention has excellent piezoelectric properties.
Experimental example 2 capacitor
An aluminum layer having a thickness of 80nm was deposited on one surface of a glass substrate by a vacuum deposition method on glass. The polymer film of example 1 was bonded to an aluminum layer, and then an aluminum layer having a metal thickness of 80nm was deposited on the surface of the polymer film by vacuum deposition to obtain a capacitor a. The aluminum layers are electrodes in the capacitor, and the polymer film between the two aluminum layers serves as an insulating film.
Capacitors B and C were obtained by replacing the polymer film in example 1 with the polymer film of example 2 or 3.
Fig. 7 is a hysteresis loop diagram of capacitors A, B and C. As can be seen from FIG. 7, the polymer film of example 1 had a remanent polarization of 18.8. mu.C/cm when the applied voltage field strength was 142MV/m2(ii) a The residual polarization value of the polymer film of the example 2 can reach 13.4 mu C/cm2(ii) a The residual polarization value of the polymer film of the example 3 can reach 23.1 mu C/cm2. The remanent polarization value reported by the literature is 7-9 mu C/cm2Compared with the prior art, the polymer film has larger residual polarization value and excellent spontaneous polarization property and ferroelectric property. The ferroelectric properties of the polymer film of example 3 are better.
FIG. 8 is a leakage current density graph of the capacitor A. As can be seen from FIG. 8, the leakage current of the polymer film of example 1 is small, and when the applied voltage is 15V, the leakage current is 4.0 × 10-6A/cm2。
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.

Claims (6)

1. A method of making a polymer film, comprising the steps of:
(1) attaching an oriented polyvinylidene fluoride film on a substrate to obtain an initial film;
(2) applying the vinylidene fluoride-trifluoroethylene copolymer solution to an initial membrane to obtain a pretreated membrane;
(3) drying the pretreatment film at 40-60 ℃ for 8-24 h, heating the dried pretreatment film to 135-145 ℃ at a speed of 150-200 ℃/min, preserving heat for 60-80 min, then cooling to 21-25 ℃ at a speed of 1-10 ℃/min to form an annealed pretreatment film, placing the annealed pretreatment film and the substrate in a dilute hydrofluoric acid solution for etching, then stripping the pretreatment film from the substrate, and placing the stripped film in clean water for cleaning to obtain the polymer film.
2. The production method according to claim 1, wherein in the step (1), the oriented polyvinylidene fluoride film is obtained by any one method selected from a melt-stretching method, a rubbing orientation method and a blade coating method.
3. The method according to claim 2, wherein in the step (1), the thickness of the polyvinylidene fluoride film is 10 to 100 nm.
4. The production method according to claim 1, wherein in the step (2), the vinylidene fluoride-trifluoroethylene copolymer solution is applied to the initial film by a spin coating method; the rotation speed is 1000-5000 rpm.
5. The method according to claim 4, wherein in the step (3), the thickness of the polymer film is 100 to 150 nm.
6. The method according to claim 5, wherein in the step (2), the solvent of the vinylidene fluoride-trifluoroethylene copolymer solution is one or more selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide and butanone; the concentration of the vinylidene fluoride-trifluoroethylene copolymer is 10-20 mg/ml.
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