Piezoelectric materials, piezoelectric films, and piezoelectric elements

Abstract

This copolymer has a structural unit represented by (1) (R represents at least one group selected from a hydrogen atom, a methyl group, an ethyl group, a methoxy methyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a (trimethyl)methyl group, a pentyl group, an isopentyl group, a t-pentyl group, a neopentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, an adamantyl group, a phenyl group optionally having a substituent, o-, m-, or p-acetamide phenyl group, o-, m-, or p-benzamide group, o-, m-, or p-benz(methyl)amide group, o-, m-, or p-benz(N,N-dimethyl)amide group, a benzyl group optionally having a substituent, and a phenoxy methyl group) and a structural unit represented by (2).

Description

Technical Field

[0001] The present invention is, pressure relates to electrical materials, piezoelectric films, and piezoelectric elements. This application claims priority based on Japanese Patent Application No. 2021-141397 filed in Japan on August 31, 2021, and incorporates its content herein.

Background Art

[0002] Conventionally, as a piezoelectric material for forming a piezoelectric body of a piezoelectric element, PZT (PbZrO3-PbTiO3 solid solution), which is a ceramic material, has been widely used. However, PZT has the disadvantage of being brittle because it is a lead-containing ceramic. Therefore, as a piezoelectric material, a material with a low environmental load and high flexibility is required.

[0003] As a piezoelectric material that meets such requirements, it is conceivable to use a polymer piezoelectric material. Examples of polymer piezoelectric materials include ferroelectric polymers such as polyvinylidene fluoride (PVDF) and vinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)). However, these ferroelectric polymers have insufficient heat resistance. Therefore, a piezoelectric body made of a conventional ferroelectric polymer loses its piezoelectric properties at high temperatures, and physical properties such as elastic modulus also deteriorate. Therefore, a piezoelectric element having a piezoelectric body made of a conventional ferroelectric polymer has a narrow usable temperature range.

[0004] In addition, as a piezoelectric material, there is an amorphous polymer piezoelectric material that acquires piezoelectricity by polarizing while cooling at a temperature near the glass transition temperature. The piezoelectric properties of an amorphous polymer disappear when the temperature approaches the glass transition temperature. Therefore, there is a need for an amorphous polymer piezoelectric material having a high glass transition temperature and good heat resistance.

[0005] Examples of amorphous polymer piezoelectric materials with a high glass transition temperature include vinylidene cyanide-vinyl acetate copolymers (see, for example, Patent Document 1). However, vinylidene cyanide-vinyl acetate copolymers require the use of vinylidene cyanide, which is difficult to handle, as a raw material monomer.

[0006] In addition, it is conceivable to use acrylonitrile, which is easy to handle, as a raw material monomer for the polymer piezoelectric material without using vinylidene cyanide. However, polymers using acrylonitrile as a raw material monomer have a low glass transition temperature. In addition, polymers using acrylonitrile as a raw material monomer also have low piezoelectric properties (see, for example, Non-Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Non-Patent Documents

[0008]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Conventionally, there has been a demand for a polymer piezoelectric material from which a piezoelectric film having high heat resistance and piezoelectric properties can be obtained. The present invention has been made in view of the above circumstances, and aims to provide a copolymer that can be used as a piezoelectric material to obtain a piezoelectric film with high heat resistance and piezoelectric properties.

[0010] Furthermore, the present invention aims to provide a piezoelectric material that contains the copolymer of the present invention and yields a piezoelectric film with high heat resistance and piezoelectric properties. Furthermore, the present invention aims to provide a piezoelectric film containing the piezoelectric material of the present invention that has high heat resistance and piezoelectric properties, and a piezoelectric element having the piezoelectric film of the present invention that has high heat resistance and piezoelectric properties. [Means for solving the problem]

[0011] To solve the above problems, the following means are provided. A copolymer according to one aspect of the present invention is a copolymer having a structural unit represented by the following general formula (1) and a structural unit represented by the following formula (2).

[0012] [ka] (In general formula (1), R is a hydrogen atom, a methyl group, an ethyl group, a methoxymethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a (trimethyl)methyl group, a pentyl group, an isopentyl group, a t-pentyl group, a neopentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, an adamantyl group, a phenyl group, an o-acetamidophenyl group, or an m-acetamidophenyl group, which may have 1 to 5 substituents selected from a methyl group, an ethyl group, a methoxy group, an ethoxy group, a fluoro group, a trifluoromethyl group, or a cyano group at any position.) , a benzyl group, or a phenoxymethyl group, which may have 1 to 5 substituents selected from a methyl group, an ethyl group, a methoxy group, an ethoxy group, a fluoro group, a trifluoromethyl group, or a cyano group at any position. [Effects of the Invention]

[0013] The copolymer of the present invention has a structural unit represented by general formula (1) and a structural unit represented by formula (2). For this reason, the copolymer of the present invention can be used as a piezoelectric material to obtain piezoelectric films with high heat resistance and piezoelectric properties. Furthermore, since the piezoelectric material of the present invention contains the copolymer of the present invention, a piezoelectric film with high heat resistance and piezoelectric properties can be obtained. Furthermore, the piezoelectric film of the present invention includes the copolymer of the present invention. For this reason, the piezoelectric film of the present invention and the piezoelectric element of the present invention having the piezoelectric film of the present invention have excellent heat resistance and piezoelectric properties. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a chart of 1H-NMR measurements of the polymer in Example 3. [Figure 2] Figure 2 is a magnified view of a portion of Figure 1. [Figure 3] Figure 3 is a magnified view of a portion of Figure 1. [Figure 4] Figure 4 is a chart of 1H-NMR measurements of the polymer in Example 10. [Figure 5] Figure 5 is a magnified view of a portion of Figure 4. [Figure 6] Figure 6 is a chart of 1H-NMR measurements of the polymer in Example 15. [Figure 7] Figure 7 is a magnified view of a portion of Figure 6. [Figure 8] Figure 8 is a magnified view of a portion of Figure 6. [Figure 9] Figure 9 is a chart of 1H-NMR measurements of the polymer in Example 20. [Figure 10] Figure 10 is a magnified view of a portion of Figure 9. [Figure 11] Figure 11 is a magnified view of a portion of Figure 9. [Figure 12] Figure 12 is a chart of 1H-NMR measurements of the polymer in Example 25. [Figure 13] Figure 13 is a magnified view of a portion of Figure 12. [Figure 14] Figure 14 is a magnified view of a portion of Figure 12. [Modes for carrying out the invention]

[0015] To solve the above problems, the inventors focused on the heat resistance of polymers using acrylonitrile as a raw material monomer and conducted extensive research. As a result, we found that a copolymer having a specific structural unit with a secondary amide skeleton (RC(=O)-NH-) and a structural unit derived from acrylonitrile is sufficient.

[0016] Compounds in which a vinyl group is bonded to the nitrogen atom of a secondary amide skeleton have a high affinity for acrylonitrile. Therefore, compounds in which a vinyl group is bonded to the nitrogen atom of a secondary amide skeleton can form copolymers with acrylonitrile. Furthermore, copolymerizing compounds in which a vinyl group is bonded to the nitrogen atom of a secondary amide skeleton with acrylonitrile forms copolymers with a higher glass transition temperature (Tg) and better heat resistance compared to polyacrylonitrile.

[0017] More specifically, the hydrogen atoms of the amide skeleton in a compound in which a vinyl group is bonded to the nitrogen atom of the secondary amide skeleton exhibit hydrogen bond donor properties. On the other hand, the nitrile groups, which are polar groups contained in acrylonitrile, exhibit hydrogen bond acceptor properties. Therefore, in copolymers having structural units containing a secondary amide skeleton and structural units derived from acrylonitrile, the ordered structure that can be formed by the nitrile groups contained in the structural units derived from acrylonitrile is considered to be disrupted by the structural units containing the secondary amide skeleton that exhibit hydrogen bond donor properties. As a result, the multiple nitrile groups derived from acrylonitrile in the copolymer are less likely to be oriented in a way that cancels out each other's polarity. For this reason, it is presumed that copolymers having structural units containing a secondary amide skeleton and structural units derived from acrylonitrile will become piezoelectric materials that yield piezoelectric films with good heat resistance and piezoelectric properties.

[0018] Furthermore, the inventors produced a copolymer having a specific structural unit containing a secondary amide skeleton and a structural unit derived from acrylonitrile, and confirmed that it has good heat resistance and that a piezoelectric film using it as a piezoelectric material has good piezoelectric properties, which led to the invention of the present invention.

[0019] The present invention includes the following embodiments.

[0020] [1] A copolymer having structural units represented by the following general formula (1) and structural units represented by the following formula (2).

[0021] [ka] (In general formula (1), R is a hydrogen atom, a methyl group, an ethyl group, a methoxymethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a (trimethyl)methyl group, a pentyl group, an isopentyl group, a t-pentyl group, a neopentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, an adamantyl group, a phenyl group, an o-acetamidophenyl group, or an m-acetamidophenyl group, which may have 1 to 5 substituents selected from a methyl group, an ethyl group, a methoxy group, an ethoxy group, a fluoro group, a trifluoromethyl group, or a cyano group at any position.) , a benzyl group, or a phenoxymethyl group, which may have 1 to 5 substituents selected from a methyl group, an ethyl group, a methoxy group, an ethoxy group, a fluoro group, a trifluoromethyl group, or a cyano group at any position.

[0022] [2] The copolymer according to [1], wherein R is one of a hydrogen atom, a methyl group, a butyl group, a phenyl group, and a cyanophenyl group in the general formula (1). [3] The copolymer according to [1] or [2], wherein the content of the structural unit represented by formula (2) is 20 to 80 mol%.

[0023] [4] A piezoelectric material comprising a copolymer as described in any of [1] to [3]. [5] A piezoelectric film comprising the copolymer described in any of [1] to [3]. A piezoelectric element having the piezoelectric film described in [6] [5] and an electrode disposed on the surface of the piezoelectric film.

[0024] The copolymer, piezoelectric material, piezoelectric film, and piezoelectric element of the present invention will be described in detail below. [Copolymer] The copolymer of this embodiment has a structural unit represented by general formula (1) and a structural unit represented by formula (2).

[0025] In the structural unit represented by formula (1) of the copolymer of this embodiment, R is a hydrogen atom, methyl group, ethyl group, methoxymethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, isobutyl group, (trimethyl)methyl group, pentyl group (-CH2-CH2-CH2-CH2-CH3), isopentyl group (-CH2-CH2-CH(CH3)2), t-pentyl group (-C(CH3)2-C2H5), neopentyl group (-CH2-C(CH3)3), cyclopentyl group, hexyl group, cyclohexyl group, adamantyl The group is one of the following: a phenyl group which may have substituents, an o-acetamidophenyl group, an m-acetamidophenyl group, a p-acetamidophenyl group, an o-benzamide group, an m-benzamide group, a p-benzamide group, an o-benz(methyl)amide group, an m-benz(methyl)amide group, a p-benz(methyl)amide group, an o-benz(N,N-dimethyl)amide group, an m-benz(N,N-dimethyl)amide group, a p-benz(N,N-dimethyl)amide group, a benzyl group which may have substituents, or a phenoxymethyl group. Phenyl groups that may have substituents include substituted phenyl groups and unsubstituted phenyl groups, i.e., phenyl groups. Optional benzyl groups include substituted benzyl groups and unsubstituted benzyl groups, i.e., benzyl groups.

[0026] In the structural unit represented by formula (1), if R is a substituted phenyl group or a substituted benzyl group, the position of the substituent can be any position. The number of substituents is 1 to 5. The substituents are selected from methyl, ethyl, methoxy, ethoxy, fluoro, trifluoromethyl, and cyano groups. If the substituted phenyl group or substituted benzyl group has multiple substituents, the types of substituents may all be different, or some may be of the same type.

[0027] The copolymer of this embodiment can be easily manufactured because R in the structural unit represented by formula (1) is as described above. Furthermore, because R in the structural unit represented by formula (1) is as described above, the copolymer of this embodiment can be used as a material for piezoelectric films with good heat resistance and piezoelectric properties. R in the structural unit represented by formula (1) is preferably one of the following: a hydrogen atom, a methyl group, a butyl group, a phenyl group, and a cyanophenyl group. The position of the cyano group in the cyanophenyl group may be any position. The cyanophenyl group is more preferably a 3-cyanophenyl group. Since R in the structural unit represented by formula (1) can be used as a material for piezoelectric films with better heat resistance and piezoelectric properties, it is more preferably a methyl group or a phenyl group. In particular, since it has good hydrophobicity and thus excellent polarization stability, and also provides excellent heat resistance due to the π-stack effect, it is even more preferable for R in the structural unit represented by formula (1) to be a phenyl group.

[0028] In the copolymer of this embodiment, there are no particular restrictions on the arrangement order of the repeating units, the structural units represented by formula (1) and the structural units represented by formula (2). Furthermore, in the copolymer of this embodiment, the number of structural units represented by formula (1) and the number of structural units represented by formula (2) may be the same or different. Therefore, the copolymer of this embodiment may have alternating arrangement portions in which the structural units represented by formula (1) and the structural units represented by formula (2) are arranged alternately, random arrangement portions in which the structural units represented by formula (1) and the structural units represented by formula (2) are arranged without order, and block arrangement portions having portions in which the structural units represented by formula (1) are arranged continuously and portions in which the structural units represented by formula (2) are arranged continuously, distributed in any proportion. In the copolymer of this embodiment, it is preferable to include alternating arrangement portions because the nitrile groups contained in the structural units represented by formula (2) are less likely to be oriented in a way that cancels out each other's polarity, making it usable as a piezoelectric material with good heat resistance and piezoelectric properties.

[0029] The copolymer of this embodiment preferably contains 20 to 80 mol% of the structural unit represented by formula (1), more preferably 20 to 70 mol%, and even more preferably 30 to 70 mol%. When the content of the structural unit represented by formula (1) is 20 mol% or more, the copolymer becomes even more heat resistant. Furthermore, when the content of the structural unit represented by formula (1) is 80 mol% or less, it is possible to prevent the piezoelectric film containing the copolymer from becoming hard and brittle due to an excessive content of the structural unit represented by formula (1). In addition, when the content of the structural unit represented by formula (1) is 80 mol% or less, it is possible to suppress the decrease in the insulation resistance of the copolymer due to moisture absorption by the structural unit represented by formula (1).

[0030] The copolymer of this embodiment preferably contains 20 to 80 mol% of the structural unit represented by formula (2), more preferably 30 to 80 mol%, and even more preferably 30 to 70 mol%. When the content of the structural unit represented by formula (2) is 20 mol% or more, the copolymer has high insulation resistance and can form a flexible piezoelectric film. Furthermore, when the content of the structural unit represented by formula (2) is 80 mol% or less, it becomes easier to ensure the content of the structural unit represented by formula (1). As a result, the nitrile groups contained in the structural unit represented by formula (2) are less likely to be oriented in a way that cancels out each other's polarity, resulting in a copolymer that can form a piezoelectric film with better heat resistance and piezoelectric properties.

[0031] The copolymer of this embodiment may optionally contain one or more structural units other than the structural unit represented by formula (1) and the structural unit represented by formula (2). Examples of other structural units include structural units derived from known monomers or oligomers having polymerizable unsaturated bonds. In the copolymer of this embodiment, the total content of structural units represented by formula (1) and structural units represented by formula (2) is preferably 50% by mass or more, more preferably 80% by mass or more, and may be 90% by mass or more, or may consist only of structural units represented by formula (1) and structural units represented by formula (2).

[0032] The weight-average molecular weight (Mw) of the copolymer in this embodiment is preferably 10,000 to 1,000,000. If the weight-average molecular weight (Mw) of the copolymer is 10,000 or more, the film-forming properties are good, and a piezoelectric film containing the copolymer of this embodiment can be easily manufactured. If the weight-average molecular weight (Mw) of the copolymer is 1,000,000 or less, it can be easily dissolved in a solvent, and a piezoelectric film can be easily manufactured using a coating solution dissolved in a solvent.

[0033] "Method for producing copolymers" The copolymer of this embodiment can be produced, for example, by radical copolymerization using a known method with a starting monomer containing a compound from which the structural unit represented by formula (1) is derived, acrylonitrile, and a polymerization initiator such as azobisbutyronitrile. The polymerization conditions, such as reaction temperature and reaction time, when producing the copolymer of this embodiment can be appropriately determined according to the composition of the raw material monomers.

[0034] The compounds from which the structural unit shown in formula (1) originates are compounds in which the structural unit shown in formula (1) and the secondary amide skeleton and the atoms bonded to the carbon atoms of the secondary amide skeleton are the same, and a vinyl group is bonded to the nitrogen atom of the secondary amide skeleton. Specifically, the compounds from which the structural unit shown in formula (1) originates include N-vinyl-formamide, N-vinyl-acetamide, N-vinyl-propanamide, N-vinyl-2-methoxyacetamide, N-vinyl-butanamide, N-vinyl-2-methylpropanamide, N-vinyl-cyclopropanecarboxyamide, N-vinyl-pentanamide, N-vinyl-3-methylbutanamide, N-vinyl-2,2-dimethylpropanamide, N-vinyl-hexaneamide, N-vinyl-4-methylpentanamide, and N-vinyl-3,3-dimethylbutanamide. Examples include N-vinyl-2,2-dimethylbutanamide, N-vinyl-cyclopentanecarboxyamide, N-vinyl-heptanamide, N-vinyl-cyclohexanecarboxyamide, N-vinyl-phenylamide, N-vinyl-4-methylbenzamide, N-vinyl-2-phenylacetamide, N-vinyl-2-phenoxyacetamide, N-vinyl-2-cyanophenylamide, N-vinyl-3-cyanophenylamide, and N-vinyl-4-cyanophenylamide, which are appropriately determined depending on the structure of the copolymer of this embodiment, which is the target product.

[0035] "Piezoelectric materials" The piezoelectric material of this embodiment includes the copolymer of this embodiment. The copolymer of this embodiment included in the piezoelectric material of this embodiment may be one type or two or more types. Furthermore, the piezoelectric material of this embodiment may, if necessary, include one or two or more known polymers other than the copolymer of this embodiment together with the copolymer of this embodiment.

[0036] "Piezoelectric film" The piezoelectric film of this embodiment includes the copolymer of this embodiment. The piezoelectric film of this embodiment can be manufactured, for example, by the method shown below. The piezoelectric material of this embodiment, including the copolymer of this embodiment, is dissolved in a solvent to prepare a coating solution. As the solvent, known solvents such as N,N-dimethylformamide can be used. Next, the coating solution is applied to a peelable substrate to a predetermined thickness to form a coating film. As the substrate, known materials such as resin films can be used. The method of applying the coating solution can be a known method depending on the coating thickness, viscosity of the coating solution, etc. After that, the coating film is dried to remove the solvent in the coating film and obtain a piezoelectric material sheet. The piezoelectric material sheet may be stretched as needed.

[0037] Subsequently, the piezoelectric material sheet is peeled from the substrate, and electrodes made of a known conductive material such as aluminum are placed on one side and the other side of the piezoelectric material sheet. Then, a voltage is applied to the piezoelectric material sheet via the electrodes on both sides at a temperature near the glass transition temperature of the piezoelectric material forming the sheet. After that, the piezoelectric material sheet is cooled while the voltage is still applied. This acquires piezoelectric properties. Through the above steps, a sheet-like piezoelectric film is obtained. The electrodes used to achieve piezoelectricity may be used as components to form the piezoelectric element, or they may be removed.

[0038] "Piezoelectric element" The piezoelectric element of this embodiment comprises a piezoelectric film and electrodes disposed on the surface of the piezoelectric film. Specifically, it includes a sheet-like piezoelectric film and electrodes disposed on one surface and the other surface of the piezoelectric film, respectively. As the electrode material, known conductive materials such as aluminum can be used. The piezoelectric element of this embodiment can be manufactured, for example, by providing electrodes on one surface and the other surface of a piezoelectric film, respectively, using a known method such as vapor deposition.

[0039] The copolymer of this embodiment has structural units represented by general formula (1) and structural units represented by formula (2). Therefore, the copolymer of this embodiment can be used as a piezoelectric material to obtain piezoelectric films with high heat resistance and piezoelectric properties. Furthermore, since the piezoelectric material of this embodiment includes the copolymer of this embodiment, a piezoelectric film with high heat resistance and piezoelectric properties can be obtained. Furthermore, the piezoelectric film of this embodiment includes the copolymer of this embodiment. For this reason, the piezoelectric film of this embodiment and the piezoelectric element of this embodiment having the piezoelectric film of this embodiment have excellent heat resistance and piezoelectric properties.

[0040] Although embodiments of the present invention have been described in detail above, the configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications to the configurations are possible without departing from the spirit of the present invention. [Examples]

[0041] "Example 1" In a 100 ml Schlenk tube, 0.4 g (5.0 mmol) of N-vinyl acetamide represented by the following general formula (11) and 1.3 ml (20 mmol) of acrylonitrile were mixed, and 14.9 mg (0.09 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 1.1 g of the polymer of Example 1. The yield was 74%.

[0042] [ka] (In general formula (11), R is a methyl group.)

[0043] For the polymer of Example 1, an NMR (nuclear magnetic resonance) spectrometer (product name JNM-ECA500, manufactured by JEOL Ltd.) was used, and dimethyl sulfoxide d6 (DMSO-d6) was used as the solvent. 1 The molecular structure was identified by performing 1H-NMR measurements. As a result, it was confirmed that the polymer of Example 1 is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a methyl group) and a structural unit represented by formula (2). Also, Example 1 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 1 was 83 mol%.

[0044] Example 2 0.3 g (4.0 mmol) of N-vinyl acetamide and 0.5 ml (8.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 7.6 mg (0.04 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.4 g of the polymer of Example 2. The yield was 52%.

[0045] Regarding the polymer of Example 2, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 2, like the polymer of Example 1, is a copolymer having a structural unit represented by general formula (1) (where R is a methyl group) and a structural unit represented by formula (2). Also, Example 2 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 2 was 74 mol%.

[0046] "Example 3" In a 100 ml Schlenk tube, 0.7 g (8.0 mmol) of N-vinyl-acetamide and 0.8 ml (12.0 mmol) of acrylonitrile were mixed, 13.2 mg (0.08 mmol) of azobisisobutyronitrile was added, and the mixture was reacted at 60 °C for 2 hours. The reaction product was poured into 200 ml of methanol for reprecipitation, and after filtration and drying, 0.7 g of the polymer of Example 3 was obtained. The yield was 53%.

[0047] For the polymer of Example 3, in the same manner as the polymer of Example 1, 1 1H-NMR measurement was carried out. Fig. 1 is the 1 1H-NMR measurement chart of the polymer of Example 3. Figs. 2 and 3 are enlarged views of a part of Fig. 1. And for the polymer of Example 3, 1 using the results of 1H-NMR measurement, the molecular structure was specified. As a result, it was confirmed that the polymer of Example 3 is a copolymer having a structural unit represented by the general formula (1) (R in the general formula (1) is a methyl group) and a structural unit represented by the formula (2), similar to the polymer of Example 1. Also, for Example 3 1 the composition ratio was calculated from the integral values of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by the formula (2) contained in the polymer of Example 3 was 60 mol%.

[0048] "Example 4" In a 100 ml Schlenk tube, 0.6 g (8.0 mmol) of N-vinyl-acetamide and 0.5 ml (8.0 mmol) of acrylonitrile were mixed, 11.1 mg (0.07 mmol) of azobisisobutyronitrile was added, and the mixture was reacted at 60 °C for 2 hours. The reaction product was poured into 200 ml of methanol for reprecipitation, and after filtration and drying, 0.8 g of the polymer of Example 4 was obtained. The yield was 72%.

[0049] For the polymer of Example 4, in the same manner as the polymer of Example 1, 1The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 4, like the polymer of Example 1, is a copolymer having a structural unit represented by general formula (1) (where R is a methyl group) and a structural unit represented by formula (2). Also, Example 4 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 4 was 44 mol%.

[0050] Example 5 In a 100 ml Schlenk tube, 1.0 g (12.0 mmol) of N-vinyl acetamide and 0.5 ml (8.0 mmol) of acrylonitrile were mixed, and 14.5 mg (0.09 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.9 g of the polymer of Example 5. The yield was 62%.

[0051] Regarding the polymer of Example 5, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 5, like the polymer of Example 1, is a copolymer having a structural unit represented by general formula (1) (where R is a methyl group) and a structural unit represented by formula (2). Also, Example 5 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 5 was 29 mol%.

[0052] "Example 6" 0.9 g (10.0 mmol) of N-vinyl acetamide and 0.3 ml (5.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 11.2 mg (0.07 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.5 g of the polymer of Example 6. The yield was 45%.

[0053] Regarding the polymer of Example 6, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 6, like the polymer of Example 1, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a methyl group) and a structural unit represented by formula (2). Also, Example 6 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 6 was 18 mol%.

[0054] Example 7 0.6 g (4.0 mmol) of N-vinylphenylamide and 1.0 ml (16.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 14.3 mg (0.09 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.9 g of the polymer of Example 7. The yield was 63%.

[0055] Regarding the polymer of Example 7, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 7 is a copolymer having a structural unit represented by general formula (1) (where R is a phenyl group) and a structural unit represented by formula (2). Also, Example 7 1The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 7 was 85 mol%.

[0056] "Example 8" 0.6 g (4.0 mmol) of N-vinylphenylamide and 0.5 ml (8.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 10.1 mg (0.06 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.6 g of the polymer of Example 8. The yield was 59%.

[0057] Regarding the polymer of Example 8, the same procedure was followed as for the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 8, like the polymer of Example 7, is a copolymer having a structural unit represented by general formula (1) (where R is a phenyl group) and a structural unit represented by formula (2). Also, Example 8 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 8 was 77 mol%.

[0058] "Example 9" In a 100 ml Schlenk tube, 1.2 g (8.0 mmol) of N-vinylphenylamide and 0.8 ml (12.0 mmol) of acrylonitrile were mixed, and 18.1 mg (0.11 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 1.3 g of the polymer of Example 9. The yield was 72%.

[0059] Regarding the polymer of Example 9, the same procedure was followed as with the polymer of Example 1. 1The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 9, like the polymer of Example 7, is a copolymer having a structural unit represented by general formula (1) (where R is a phenyl group) and a structural unit represented by formula (2). Also, Example 9 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 9 was 63 mol%.

[0060] "Example 10" In a 100 ml Schlenk tube, 1.2 g (8.0 mmol) of N-vinylphenylamide and 0.5 ml (8.0 mmol) of acrylonitrile were mixed, and 15.9 mg (1.10 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 1.0 g of the polymer of Example 10. The yield was 63%.

[0061] Regarding the polymer of Example 10, the same procedure was followed as with the polymer of Example 1. 1 1H-NMR measurements were performed. Figure 4 shows the polymer of Example 10. 1 This is an H-NMR measurement chart. Figure 5 is an enlarged view of a part of Figure 1. And, regarding the polymer of Example 10, 1 The molecular structure was identified using the results of 1H-NMR measurements. As a result, it was confirmed that the polymer of Example 10, like the polymer of Example 7, is a copolymer having a structural unit represented by general formula (1) (where R is a phenyl group) and a structural unit represented by formula (2). Also, Example 10 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 10 was 50 mol%.

[0062] "Example 11" In a 100 ml Schlenk tube, 1.8 g (12.0 mmol) of N-vinylphenylamide and 0.5 ml (8.0 mmol) of acrylonitrile were mixed, and 21.8 mg (0.13 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 1.4 g of the polymer of Example 11. The yield was 64%.

[0063] Regarding the polymer of Example 11, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 11, like the polymer of Example 7, is a copolymer having a structural unit represented by general formula (1) (where R is a phenyl group) and a structural unit represented by formula (2). Also, Example 11 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 11 was 26 mol%.

[0064] Example 12 In a 100 ml Schlenk tube, 1.8 g (12.0 mmol) of N-vinylphenylamide and 0.4 ml (6.0 mmol) of acrylonitrile were mixed, and 20.7 mg (0.13 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 1.2 g of the polymer of Example 12. The yield was 58%.

[0065] Regarding the polymer of Example 12, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 12, like the polymer of Example 7, is a copolymer having a structural unit represented by general formula (1) (where R is a phenyl group) and a structural unit represented by formula (2). Also, Example 12 1The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 12 was 16 mol%.

[0066] "Example 13" In a 100 ml Schlenk tube, 0.1 g (2.0 mmol) of N-vinyl-formamide and 0.7 ml (10.0 mmol) of acrylonitrile were mixed, and 5.4 mg (0.03 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.5 g of the polymer of Example 13. The yield was 68%.

[0067] Regarding the polymer of Example 13, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 13 is a copolymer having a structural unit represented by general formula (1) (where R is a hydrogen atom) and a structural unit represented by formula (2). Also, Example 13 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 13 was 83 mol%.

[0068] "Example 14" 0.4 g (5.0 mmol) of N-vinyl-formamide and 0.7 ml (10.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 7.1 mg (0.04 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.7 g of the polymer of Example 14. The yield was 74%.

[0069] Regarding the polymer of Example 14, the same procedure was followed as with the polymer of Example 1. 1The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 14, like the polymer of Example 13, is a copolymer having a structural unit represented by general formula (1) (where R is a hydrogen atom) and a structural unit represented by formula (2). Also, Example 14 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 14 was 69 mol%.

[0070] Example 15 0.7 g (10.0 mmol) of N-vinyl-formamide and 0.7 ml (10.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 9.9 mg (0.06 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 1.0 g of the polymer of Example 15. The yield was 79%.

[0071] Regarding the polymer of Example 15, the same procedure was followed as with the polymer of Example 1. 1 1H-NMR measurements were performed. Figure 6 shows the polymer of Example 15. 1 This is an H-NMR measurement chart. Figures 7 and 8 are enlarged views of a portion of Figure 6. And, regarding the polymer of Example 15, 1 The molecular structure was identified using the results of 1H-NMR measurements. As a result, it was confirmed that the polymer of Example 15, like the polymer of Example 13, is a copolymer having a structural unit represented by general formula (1) (where R is a hydrogen atom) and a structural unit represented by formula (2). Also, Example 15 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 15 was 56 mol%.

[0072] "Example 16" 0.7 g (10.0 mmol) of N-vinyl-formamide and 0.4 ml (6.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 8.2 mg (0.05 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.7 g of the polymer of Example 16. The yield was 65%.

[0073] Regarding the polymer of Example 16, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 16, like the polymer of Example 13, is a copolymer having a structural unit represented by general formula (1) (where R is a hydrogen atom) and a structural unit represented by formula (2). Also, Example 16 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 16 was 43 mol%.

[0074] "Example 17" 0.7 g (10.0 mmol) of N-vinyl-formamide and 0.4 ml (6.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 8.2 mg (0.05 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.7 g of the polymer of Example 17. The yield was 65%.

[0075] Regarding the polymer of Example 17, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 17, like the polymer of Example 13, is a copolymer having a structural unit represented by general formula (1) (where R is a hydrogen atom) and a structural unit represented by formula (2). Also, Example 17 1The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 17 was 20 mol%.

[0076] Example 18 0.3 g (2.0 mmol) of N-vinyl-2,2-dimethylpropanamide and 0.4 ml (6.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 4.6 mg (0.03 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.3 g of the polymer of Example 18. The yield was 59%.

[0077] Regarding the polymer of Example 18, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 18 is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a (trimethyl)methyl group) and a structural unit represented by formula (2). Also, Example 18 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 18 was 80 mol%.

[0078] "Example 19" 0.4 g (3.0 mmol) of N-vinyl-2,2-dimethylpropanamide and 0.4 ml (6.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 4.6 mg (0.03 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.3 g of the polymer of Example 19. The yield was 59%.

[0079] Regarding the polymer of Example 19, the same procedure was followed as for the polymer of Example 1. 1The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 19, like the polymer of Example 18, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a (trimethyl)methyl group) and a structural unit represented by formula (2). Also, Example 19 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 19 was 63 mol%.

[0080] "Example 20" 0.8 g (6.0 mmol) of N-vinyl-2,2-dimethylpropanamide and 0.4 ml (6.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 8.7 mg (0.05 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.7 g of the polymer of Example 20. The yield was 63%.

[0081] Regarding the polymer of Example 20, the same procedure was followed as with the polymer of Example 1. 1 1H-NMR measurements were performed. Figure 9 shows the polymer of Example 20. 1 This is an H-NMR measurement chart. Figures 10 and 11 are enlarged views of a portion of Figure 9. And, regarding the polymer of Example 20, 1 The molecular structure was identified using the results of 1H-NMR measurements. As a result, it was confirmed that the polymer of Example 20, like the polymer of Example 18, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a (trimethyl)methyl group) and a structural unit represented by formula (2). Also, Example 20 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 20 was 46 mol%.

[0082] "Example 21" 0.8 g (6.0 mmol) of N-vinyl-2,2-dimethylpropanamide and 0.2 ml (3.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 7.4 mg (0.04 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.7 g of the polymer of Example 21. The yield was 72%.

[0083] Regarding the polymer of Example 21, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 21, like the polymer of Example 18, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a (trimethyl)methyl group) and a structural unit represented by formula (2). Also, Example 21 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 21 was 33 mol%.

[0084] Example 22 0.8 g (6.0 mmol) of N-vinyl-2,2-dimethylpropanamide and 0.1 ml (2.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 7.0 mg (0.04 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.6 g of the polymer of Example 22. The yield was 69%.

[0085] Regarding the polymer of Example 22, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 22, like the polymer of Example 18, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a (trimethyl)methyl group) and a structural unit represented by formula (2). Also, Example 22 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 22 was 19 mol%.

[0086] "Example 23" 0.7 g (4.0 mmol) of N-vinyl-3-cyanophenylamide and 0.8 ml (12.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 10.6 mg (0.06 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.8 g of the polymer of Example 23. The yield was 60%.

[0087] Regarding the polymer of Example 23, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 23 is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a 3-cyanophenyl group) and a structural unit represented by formula (2). Also, Example 23 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 23 was 82 mol%.

[0088] Example 24 0.7 g (4.0 mmol) of N-vinyl-3-cyanophenylamide and 0.5 ml (8.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 10.6 mg (0.06 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.8 g of the polymer of Example 24. The yield was 60%.

[0089] Regarding the polymer of Example 24, the same procedure was followed as with the polymer of Example 1.1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 24, like the polymer of Example 23, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a 3-cyanophenyl group) and a structural unit represented by formula (2). Also, Example 24 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 24 was 66 mol%.

[0090] Example 25 0.7 g (4.0 mmol) of N-vinyl-3-cyanophenylamide and 0.3 ml (4.0 mmol) of acrylonitrile were mixed in a 100 ml Schlenk tube, and 7.3 mg (0.04 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.5 g of the polymer of Example 25. The yield was 49%.

[0091] Regarding the polymer of Example 25, the same procedure was followed as with the polymer of Example 1. 1 1H-NMR measurements were performed. Figure 12 shows the polymer of Example 25. 1 This is an H-NMR measurement chart. Figures 13 and 14 are enlarged views of a portion of Figure 12. And, regarding the polymer of Example 25, 1 The molecular structure was identified using the results of 1H-NMR measurements. As a result, it was confirmed that the polymer of Example 25, like the polymer of Example 23, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a 3-cyanophenyl group) and a structural unit represented by formula (2). Also, Example 25 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 25 was 50 mol%.

[0092] Example 26 In a 100 ml Schlenk tube, 1.4 g (8.0 mmol) of N-vinyl-3-cyanophenylamide and 0.3 ml (4.0 mmol) of acrylonitrile were mixed, and 12.7 mg (0.08 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 0.7 g of the polymer of Example 26. The yield was 42%.

[0093] Regarding the polymer of Example 26, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 26, like the polymer of Example 23, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a 3-cyanophenyl group) and a structural unit represented by formula (2). Also, Example 26 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 26 was 31 mol%.

[0094] Example 27 In a 100 ml Schlenk tube, 2.1 g (12.0 mmol) of N-vinyl-3-cyanophenylamide and 0.3 ml (4.0 mmol) of acrylonitrile were mixed, and 18.2 mg (0.11 mmol) of azobisisobutyronitrile was added. The mixture was reacted at 60°C for 2 hours. The reaction product was added to 200 ml of methanol for reprecipitation, filtered, and dried to obtain 1.0 g of the polymer of Example 27. The yield was 43%.

[0095] Regarding the polymer of Example 27, the same procedure was followed as with the polymer of Example 1. 1 The molecular structure was identified by 1H-NMR measurement. As a result, it was confirmed that the polymer of Example 27, like the polymer of Example 23, is a copolymer having a structural unit represented by general formula (1) (where R in general formula (1) is a 3-cyanophenyl group) and a structural unit represented by formula (2). Also, Example 27 1 The composition ratio was calculated from the integrated values ​​of each signal in the 1H-NMR spectrum. As a result, the content of the structural unit represented by formula (2) in the polymer of Example 27 was 19 mol%.

[0096] "Comparative Example 1" Polyacrylonitrile (trade name 181315, manufactured by Sigma-Aldrich) was used as the polymer in Comparative Example 1. "Comparative Example 2" Poly(acrylonitrile-CO-methyl acrylate) (trade name 517941, manufactured by Sigma-Aldrich) was used as the polymer in Comparative Example 2.

[0097] Table 1 shows the R in the structural unit represented by general formula (1) and the content of the structural unit represented by formula (2) for each of the polymers obtained in Examples 1 to 27 in this manner. Furthermore, Table 1 shows the compound names of the polymers in Comparative Example 1 and Comparative Example 2, and the content of the structural unit represented by formula (2) in the polymers, respectively.

[0098] [Table 1]

[0099] The glass transition temperature (Tg) of the polymers in Examples 1 to 27, Comparative Example 1, and Comparative Example 2 was measured using the method described below. The results are shown in Table 1. (Method for measuring glass transition temperature (Tg)) Using a high-sensitivity differential scanning calorimeter (product name, DSC6200, manufactured by Seiko Instruments Inc.), the following heating and cooling operations were performed under a nitrogen atmosphere: heating from 30°C to 200°C at a heating rate of 20°C / min, cooling from 200°C to 30°C at a cooling rate of 40°C / min, and heating from 30°C to 200°C at a heating rate of 20°C / min. The inflection point during the second heating cycle was determined and defined as the glass transition temperature (Tg).

[0100] Furthermore, using the polymers of Examples 1 to 27, Comparative Example 1, and Comparative Example 2 as piezoelectric materials, piezoelectric films were manufactured by the method described below, and the piezoelectric constant d 33 The following measurements were taken. The results are shown in Table 1.

[0101] (Manufacturing of piezoelectric films) A piezoelectric material was dissolved in N,N-dimethylformamide, a solvent, to prepare a 20% by mass polymer solution (coating solution). The obtained polymer solution was applied to a PET film (trade name, Lumirror (registered trademark), manufactured by Toray Industries, Inc.) as a substrate, so that the thickness after drying was 50 μm, forming a coating film. Subsequently, the coating film formed on the PET film was dried on a hot plate at 120°C for 6 hours to remove the solvent from the coating film, thereby obtaining a piezoelectric material sheet.

[0102] The obtained piezoelectric material sheet was peeled from the PET film, and electrodes made of aluminum were attached to one side and the other side of the piezoelectric material sheet by vapor deposition. Then, the electrodes of the piezoelectric material sheet were electrically connected to a high-voltage power supply HARB-20R60 (manufactured by Matsusada Precision Co., Ltd.), and an electric field of 100 MV / m was applied and the device was held at 140°C for 15 minutes. After that, the device was slowly cooled to room temperature while the voltage was still applied, and a polling process was performed to obtain a sheet-like piezoelectric film.

[0103] (Piezoelectric constant d) 33 (Measurement method) A pin with a tip diameter of 1.5 mm was used as a sample fixing jig to attach the piezoelectric film to the measuring device. Piezoelectric constant d 33 The measuring device used was the PM200 piezometer system from PIEZOTEST. Piezoelectric constant d 33 The measured value of will be positive or negative depending on whether the piezoelectric film being measured is facing forward or backward. In this specification, the piezoelectric constant d 33 The absolute value of the measured value should be recorded as the value of .

[0104] As shown in Table 1, the polymers of Examples 1 to 27 were found to have higher glass transition temperatures (Tg) and better heat resistance compared to the polymers of Comparative Examples 1 and 2. Furthermore, the piezoelectric films of Examples 1 to 27, which contain the polymers of Examples 1 to 27, have a piezoelectric constant d compared to the piezoelectric film of Comparative Example 1, which contains the polymer of Comparative Example 1, and the piezoelectric film of Comparative Example 2, which contains the polymer of Comparative Example 2. 33 The coefficient of measurement was high, and the piezoelectric properties were good. In particular, the piezoelectric films of Examples 2 to 5, 8 to 11, 14 to 21, and 24 to 26, which contain polymers with a content of 20 to 80 mol% of the structural unit shown in formula (2), have a piezoelectric constant d 33 The coefficient of measurement was high, and the piezoelectric properties were good. [Industrial applicability]

[0105] The copolymer of the present invention can be used as a piezoelectric material to obtain piezoelectric films with high heat resistance and piezoelectric properties. Since the piezoelectric material of the present invention contains the copolymer of the present invention, a piezoelectric film with high heat resistance and piezoelectric properties can be obtained. The piezoelectric film of the present invention comprises the copolymer of the present invention. Therefore, the piezoelectric film of the present invention and the piezoelectric element of the present invention having the piezoelectric film of the present invention exhibit excellent heat resistance and piezoelectric properties.

Claims

1. A piezoelectric material comprising a copolymer having structural units represented by the following general formula (1) and structural units represented by the following formula (2). 【Chemistry 1】 (In general formula (1), R is a hydrogen atom, a methyl group, an ethyl group, a methoxymethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a (trimethyl)methyl group, a pentyl group, an isopentyl group, a t-pentyl group, a neopentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, an adamantyl group, a phenyl group, an o-acetamidophenyl group, or an m-acetamidophenyl group, which may have 1 to 5 substituents selected from a methyl group, an ethyl group, a methoxy group, an ethoxy group, a fluoro group, a trifluoromethyl group, or a cyano group at any position.) (The benzyl group and phenoxymethyl group may have 1 to 5 substituents selected from methyl, ethyl, methoxy, ethoxy, fluoro, trifluoromethyl, and cyano groups at any position.)

2. The piezoelectric material according to claim 1, wherein R is one of a hydrogen atom, a methyl group, a butyl group, a phenyl group, and a cyanophenyl group in the general formula (1).

3. The piezoelectric material according to claim 1 or claim 2, wherein the content of the structural unit represented by formula (2) is 20 to 80 mol%.

4. A piezoelectric film comprising the piezoelectric material according to claim 1 or claim 2.

5. A piezoelectric element having a piezoelectric film according to claim 4 and an electrode disposed on the surface of the piezoelectric film.

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