Polymer, aromatic polyamide, shaped body, film, vibration sensor, loudspeaker, structural health monitoring system

Abstract

The present invention provides a polymer, an aromatic polyamide, a molded body, and a film, which have excellent piezoelectric properties and mechanical properties. The solution is a polymer in which each hydrogen-bonding group in the repeating unit is bonded to a ring atom, the number of atoms present on the shortest path in the path of the atoms connecting the hydrogen-bonding groups is odd, and the remanent polarization is 15 mC / m 2 The above 300 mC / m 2 The following.

Description

Technical Field

[0001] This invention relates to polymers, aromatic polyamides, molded articles, and films that have ferroelectric properties. Background Technology

[0002] Ferroelectric materials are used in various sensors and image recording applications due to their piezoelectric and pyroelectric properties. Previously, known ferroelectric materials included inorganic materials such as PbZrTiO3 (PZT), and polymeric materials such as polyvinylidene fluoride (PVDF) and polylactic acid (PLA) and odd-numbered nylon. While inorganic materials possess advantages such as excellent pyroelectricity and heat resistance, their poor flexibility and difficulty in molding make them unsuitable for use as materials for large-area, thin-film, and complex-shaped piezoelectric elements.

[0003] On the other hand, although polymer materials have lower piezoelectric and thermoelectric properties than inorganic materials, they have smaller specific heat and dielectric constants, resulting in better performance indices. They are used as piezoelectric elements in applications requiring flexibility, lightweight, and large area, such as wearable devices, and are also being studied for applications in memory materials.

[0004] In the case of polymeric materials, ferroelectricity is exhibited by unifying the orientation of dipoles in the polymer to a single direction, forming remanent polarization. Regarding the orientation of dipoles, in most cases, this is achieved by controlling the higher-order structure of the polymer chains through molecular orientation and crystal system control. Examples of such methods include so-called polarization treatment, which involves placing the polymer at a temperature above its glass transition temperature and below its melting point, thus enabling the polymer chains to move, and then applying an electric field to the polymer for a certain period, maintaining this electric field to fix the structure; and mechanical uniaxial or biaxial stretching methods. However, since the stress and heat generated during use can lead to the destruction of the higher-order structure and the deactivation of ferroelectricity, durability and environmental limitations exist, which is a challenge for polymeric materials.

[0005] Aromatic polyamides are promising polymer materials that combine ferroelectricity and high durability. In particular, fully aromatic polyamides possess excellent heat resistance and chemical resistance, and are therefore used as heat-resistant fibers and highly elastic fibers. Furthermore, due to the presence of amide bonds with large dipole moments, by appropriately selecting the aromatic structure, they are expected to exhibit ferroelectricity similar to that of odd-numbered nylons. Examples of such materials include a polyamide film with residual polarization disclosed in Patent Document 1; a polyamide-based liquid crystal alignment agent varnish disclosed in Patent Document 2; a mixture of ferroelectric aromatic polyamide and liquid crystal polymer disclosed in Patent Document 3; a block copolymer of ferroelectric aromatic polyamide and polymers with melting points and glass transition temperatures disclosed in Patent Document 4; and a method for manufacturing a piezoelectric polyamide film by coating an aliphatic polyamide dissolved in an organic solvent onto a substrate and drying it, followed by heat treatment, cooling, and uniaxial stretching of the film.

[0006] Existing technical documents

[0007] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 8-302036

[0009] [Patent Document 2] Japanese Patent Application Publication No. 2002-363280

[0010] [Patent Document 3] Japanese Patent Application Publication No. 2002-37889

[0011] [Patent Document 4] Japanese Patent Application Publication No. 2001-279117

[0012] [Patent Document 5] Japanese Patent Application Publication No. 2020-167203 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] However, the aromatic polyamides disclosed in Patent Documents 1 and 2 are not fully aromatic polyamides. Due to the presence of alkyl sites in their structure, the dielectric constant and remanent polarization may sometimes decrease. Furthermore, regarding the aromatic polyamide materials disclosed in Patent Documents 3 and 4, a flexible polymer structure is introduced to make the polymer's glass transition temperature and / or melting point industrially manageable. However, this sometimes leads to a decrease in the content of aromatic polyamide sites, thereby reducing ferroelectricity. The piezoelectric film manufacturing method disclosed in Patent Document 5 is limited to aliphatic polyamides. Due to differences in polymer solubility and packing properties, the described manufacturing method is difficult to apply to fully aromatic polyamides. Additionally, due to the aforementioned structural differences, the materials disclosed in Patent Documents 1 to 5 exhibit poorer heat and stress durability compared to fully aromatic polyamides.

[0015] The purpose of this invention is to provide molded articles and / or films with excellent piezoelectric properties, mechanical properties and heat resistance by forming ferroelectric aromatic polyamides in which each amide group in the repeating unit is connected by an odd number of atoms and the amide group is bonded to aromatic ring atoms.

[0016] Methods for solving problems

[0017] The present invention, which achieves the above objectives, has the following features.

[0018] (1) A polymer having the structure shown in the following chemical formula (I) as a repeating unit, and the polymer satisfying (i) and (ii) below.

[0019] (i): In chemical formula (I), the hydrogen-bonding group A is bonded to the ring atom.

[0020] (ii): In chemical formula (I), the shortest path between the two atoms of A has an odd number of atoms.

[0021]

[0022] A is a hydrogen-bonded group, B 1 B 2 It is an n-membered ring group (where n is any natural number greater than 5 and less than 10).

[0023] (2) The polymer as described in (1), wherein the residual polarization is 15 mC / m 2 Above and 300mC / m 2 the following.

[0024] (3) The polymer as described in (1) or (2), wherein the hydrogen-bonding group A is at least one of amide, urea, or urethane.

[0025] (4) An aromatic polyamide, wherein the hydrogen-bonding group A is an amide group, and B 1 B 2 All are aromatic groups.

[0026] (5) An aromatic polyamide containing the structure shown in chemical formula (II) as a repeating unit, and satisfying (iii) and (iv) below, and having a remanent polarization of 15 mC / m 2 above,

[0027] (iii): X in chemical formula (II) is bonded to an aromatic ring atom.

[0028] (iv): In the path connecting the two X atoms in chemical formula (II), the number of atoms present in the shortest path is odd.

[0029]

[0030] X is an amide group, Ar 1 Ar 2 It is an aromatic group.

[0031] (6) The polymer and / or aromatic polyamide as described in any one of (1) to (5), wherein the structure in the repeating unit satisfies at least one of (v) to (viii) below.

[0032] (v): In the path along the bond connecting the two amide N atoms, the atoms along the shortest path are bonded to electron-donating groups.

[0033] (vi): In the path along the bond connecting the two amide carbon atoms, the atoms along the shortest path are bonded with electron-withdrawing groups.

[0034] (vii): In the path along the bond connecting two amide N atoms, atoms not on the shortest path are bonded with electron-withdrawing groups.

[0035] (viii): In the path along which the bond connects the two amide C atoms, the atoms not on the shortest path are bonded with electron-donating groups.

[0036] (7) The polymers and / or aromatic polyamides as described in (1) to (6), having a molecular backbone structure as shown in the following chemical formula (III),

[0037]

[0038] Ar 3 Ar 4 It is a group containing the molecular skeleton structure shown in chemical formulas (IV) to (VIII).

[0039] Chemical formula (IV):

[0040]

[0041] Chemical formula (V)

[0042]

[0043] Chemical formula (VI)

[0044]

[0045] Chemical formula (VII)

[0046]

[0047] R 1 For any group that satisfies (v) to (viii) in (6).

[0048] Chemical formula (VIII):

[0049]

[0050] R 2 For any group that satisfies (v) to (viii) in (6).

[0051] (8) The polymers and / or aromatic polyamides as described in (1) to (7), having the structure shown in the following chemical formula (IX),

[0052] Chemical formula (IX):

[0053]

[0054] Ar 5 Ar is a group containing the structure shown in chemical formulas (X) to (XII). 6 It is a group containing the structure shown in chemical formulas (XIII) to (XV).

[0055] Chemical formula (X):

[0056]

[0057] R 3 R is a -H or electron-donating group. 4 It is an electron-withdrawing group.

[0058] Chemical formula (XI):

[0059]

[0060] R 5 As an electron-donating group,

[0061] Chemical formula (XII):

[0062]

[0063] R 6 It is an electron-withdrawing group.

[0064] Chemical formula (XIII):

[0065]

[0066] R 7 R is an electron-withdrawing group. 8 It is a -H or electron-donating group.

[0067] Chemical formula (XIV):

[0068]

[0069] R 9 It is an electron-withdrawing group.

[0070] Chemical formula (XV):

[0071]

[0072] R 10 It is an electron-donating group.

[0073] (9) The polymers and / or aromatic polyamides described in (1) to (8) contain at least one of the following groups: perfluoroalkyl, nitro, cyano, and sulfonyl groups, which have 1 or more but less than 3 carbon atoms.

[0074] (10) The polymers and / or aromatic polyamides described in (1) to (9) have a glass transition temperature of 130°C or higher and 400°C or lower.

[0075] (11) A molded body having the polymers and / or aromatic polyamides described in (1) to (10) as the main components.

[0076] (12) The molded body as described in (11) has a piezoelectric constant d 31 and d 33 At least one of them is greater than 0 pC / N and less than 50.0 pC / N.

[0077] (13) A membrane having the polymers and / or aromatic polyamides described in (1) to (10) as the main components.

[0078] (14) The membrane as described in (13) is characterized in that the elastic modulus measured by AFM is 4.0 GPa or more and 15.0 GPa or less.

[0079] (15) The membrane described in (13) has a normalized molecular orientation MORc of 1.1 or more and 15 or less.

[0080] (16) The molded body as described in (11), wherein, when the electrostatic constant after heat treatment at 150°C for 10 minutes is denoted as d', the absolute value of the change in piezoelectric constant caused by the heat treatment is |(d')|. 31 -d' 31 ) / d 31 | and | (d 33 -d' 33 ) / d 33 The larger of the values ​​in | is greater than 0 and less than 0.5.

[0081] (17) A piezoelectric element comprising the molded body described in (11) and / or the membrane described in (13).

[0082] (18) An actuator comprising the molded body of (11) and / or the membrane of (13).

[0083] (19) An oscillator comprising the molded body described in (11) and / or the membrane described in (13).

[0084] (20) A vibration sensor having the piezoelectric element described in (17).

[0085] (21) A loudspeaker having the actuator described in (18).

[0086] (22) A structural health monitoring system having at least the vibration sensor and communication device described in (20), and detecting the vibration state of a structure and diagnosing the structure by means of the vibration sensor.

[0087] The effects of the invention

[0088] According to the present invention, the polymers and / or aromatic polyamides of the present invention can provide molded articles and / or films with excellent piezoelectric properties, mechanical properties, and heat resistance. Therefore, the polymers, aromatic polyamides, molded articles, and films of the present invention are particularly suitable for use in piezoelectric elements, actuators, oscillators, and other components. Detailed Implementation

[0089] The polymer of the present invention contains the structure shown in chemical formula (I) as a repeating unit, characterized in that it satisfies the following (I) and (ii).

[0090] (i): In chemical formula (I), the hydrogen-bonding group A is bonded to the ring atom.

[0091] (ii): In the path connecting the two A atoms in chemical formula (I), the number of atoms present in the shortest path is odd.

[0092] By satisfying these characteristics, it is possible to take into account both the excellent mechanical properties and thermal stability derived from hydrogen-bonded groups, as well as the ferroelectricity derived from molecular shape and orientation.

[0093] From the viewpoint of exhibiting excellent ferroelectricity, the remanent polarization of the polymer of the present invention is preferably 15 mC / m. 2 Above and 300mC / m 2 Below. Furthermore, from the viewpoint of efficiently obtaining hydrogen bonds, the hydrogen-bonding group A in the chemical formula (I) of the polymer of the present invention is preferably at least one of an amide group, a urea group, or a carbamate group.

[0094] The aromatic polyamide of the present invention is characterized by containing the structure shown in the following chemical formula (II) as a repeating unit, and satisfying (iii) and (iv) below.

[0095] (iii): X in chemical formula (II) is bonded to an aromatic ring atom.

[0096] (iv): In the path connecting the atoms between the two X atoms in chemical formula (II), the number of atoms in the shortest path is odd.

[0097] Chemical formula (II):

[0098]

[0099] X is an amide group, Ar 1 Ar 2 It is an aromatic group.

[0100] By satisfying these characteristics, the excellent mechanical properties and thermal stability derived from aromatic polyamides can be combined with the ferroelectricity derived from molecular shape and orientation.

[0101] In this context, aromatic ring atoms refer to the atoms that form the ring structure in an aromatic cyclic molecule. Furthermore, the path connecting the atoms between two X's in chemical formula (II) refers to the path formed by the bonds between atoms bonded to one X's atoms and the other X's atoms in adjacent X's bonds. The shortest path is the path with the fewest atoms connecting the atoms between two X's. For example, Ar, as a chemical formula (II) 1 Ar 2When X is bonded to the 1st and 3rd positions of the benzene ring (the number of atoms in the shortest path is 3) and when X is bonded to the 2nd and 7th positions of the naphthalene ring (the number of atoms in the shortest path is 5), the above conditions (iii) and (iv) are satisfied. However, when X is bonded to the 1st and 4th positions of the benzene ring (the number of atoms in the shortest path is 4), condition (iv) is not satisfied.

[0102] The lower limit of remanent polarization of the polymers and / or aromatic polyamides of the present invention is preferably 15 mC / m. 2 The above. A more preferred lower limit for residual polarization is 20 mC / m. 2 The above is further preferred to be 25mC / m 2 The lower limit of remanent polarization is less than 15 mC / m. 2 In such cases, the ferroelectricity is low, so piezoelectricity is sometimes not achieved when fabricating molded bodies or films. Furthermore, the upper limit of remanent polarization is preferably 300 mC / m. 2 The following is more preferably 50mC / m 2 The preferred range for residual polarization is 15 mC / m. 2 Above and 300mC / m 2 The following is more preferably 20mC / m 2 Above and 300mC / m 2 The following is a further preferred value: 25 mC / m 2 Above and 300mC / m 2 The optimal value is 25 mC / m. 2 Above and 50mC / m 2 Therefore, in order to keep the residual polarization within the above range, it is important that aromatic polyamides contain the above structure and that stretching, polarization, and other treatments are performed to improve the packing and anisotropy of aromatic polyamides.

[0103] In the aromatic polyamide of the present invention, the structure of the repeating unit shown in chemical formula (II) preferably satisfies at least one of (v) to (viii) below.

[0104] (v): In the path along the bond connecting the two amide N atoms, the atoms on the shortest path are bonded with electron-donating groups.

[0105] (vi): In the path along the bond connecting the two amide C atoms, the atoms on the shortest path are bonded with electron-withdrawing groups.

[0106] (vii): In the path along which the bonds connect two amide N atoms, the atoms not on the shortest path are bonded with electron-withdrawing groups.

[0107] (viii): In the path along the bond connecting the two amide C atoms, the atoms not on the shortest path are bonded with electron-donating groups.

[0108] Among them, electron-withdrawing and electron-donating groups are determined by Hammett substituent constants (Chem. Rev. 1991, 91, 99-257, etc.), σ p Functional groups with positive values ​​are electron-withdrawing groups, σ p Functional groups with negative values ​​are electron-donating groups. In this invention, electron-withdrawing groups are preferably groups containing at least one of perfluoroalkyl, sulfonyl, nitro, and cyano groups with 1 to 3 carbon atoms, and electron-donating groups are preferably groups containing at least one of alkyl, alkoxy, and hydroxyl groups with 1 to 3 carbon atoms, but are not limited to these structures. By satisfying at least one of (v) to (viii) above, a dipole moment can be induced, remanent polarization can be increased, and piezoelectric properties can be improved.

[0109] As aromatic polyamides that satisfy these characteristics, meta-linked fully aromatic polyamides can be listed, but from the viewpoints of polymerizability and availability of raw materials, structures having the following chemical formula (III) are particularly preferred.

[0110] Chemical formula (III):

[0111]

[0112] Ar 3 Ar 4 It is a group containing the molecular skeleton structure shown in chemical formulas (IV) to (VIII), and any group that satisfies any of (v) to (viii) above can be bonded to each molecular skeleton structure.

[0113] Chemical formula (IV):

[0114]

[0115] Chemical formula (V):

[0116]

[0117] Chemical formula (VI):

[0118]

[0119] Chemical formula (VII):

[0120]

[0121] R 1 For any group that satisfies (v) to (viii) above.

[0122] Chemical formula (VIII):

[0123]

[0124] R 2 For any group that satisfies (v) to (viii) above.

[0125] Furthermore, from the viewpoint of achieving high rigidity, the above structure is particularly preferred to include structural units represented by the following chemical formula (IX).

[0126] Chemical formula (IX):

[0127]

[0128] Ar 5 Ar is a group containing the structure shown in chemical formulas (X) to (XII). 6 It is a group containing the structure shown in chemical formulas (XIII) to (XV).

[0129] Chemical formula (X):

[0130]

[0131] R 3 R is a -H or electron-donating group. 4 It is an electron-withdrawing group.

[0132] Chemical formula (XI):

[0133]

[0134] R 5 It is an electron-donating group.

[0135] Chemical formula (XII):

[0136]

[0137] R 6 It is an electron-withdrawing group.

[0138] Chemical formula (XIII):

[0139]

[0140] R 7 R is an electron-withdrawing group. 8 It is a -H group or an electron-withdrawing group.

[0141] Chemical formula (XIV):

[0142]

[0143] R 9 It is an electron-withdrawing group.

[0144] Chemical formula (XV):

[0145]

[0146] R 10 It is an electron-donating group.

[0147] In the aromatic polyamide of the present invention, the number of repeating units containing the above-described structure preferably accounts for 80% or more and 100% or less of the total number of repeating units in the polymer. When the proportion of repeating units containing the above-described structure is less than 80%, the orientation of the polymer chain and dipole moment may become poor, and the ferroelectricity may decrease.

[0148] The lower limit of the glass transition temperature of the polymer and / or aromatic polyamide of the present invention is preferably 130°C or higher, more preferably 200°C or higher. Furthermore, as a range, it is preferably 130°C or higher and 400°C or lower, more preferably 200°C or higher and 400°C or lower. By setting the glass transition temperature to 130°C or higher and 400°C or lower, a decrease in ferroelectricity due to heat or time can be prevented. To achieve a glass transition temperature of 130°C or higher and 400°C or lower, methods include aromatic polyamides containing the above-described structure and methods for reducing the content of components with low glass transition temperatures.

[0149] As embodiments of the present invention, molded articles and / or films using the polymers and / or aromatic polyamides of the present invention as main components can be cited. Here, using polymers and / or aromatic polyamides as main components means that the most abundant component in the molded article and / or film is the polymer and / or aromatic polyamide described in the present invention. The amount of component is not particularly limited, but as a lower limit, it is preferably 70% by weight or more, more preferably 80% by weight or more, relative to the entire film. As a range of component amounts, preferably 70% by weight or more and 100% by weight or less, more preferably 80% by weight or more and 100% by weight or less, relative to the entire film, further enhances the mechanical properties derived from the aromatic polyamides.

[0150] The molded articles and / or films of the present invention may contain ferroelectric materials. By containing ferroelectric materials in the molded articles and / or films of the present invention, ferroelectricity can sometimes be improved, resulting in excellent piezoelectric properties. The ferroelectric materials can be either organic or inorganic. Examples of organic ferroelectric materials include polyvinylidene fluoride (PVDF), copolymers of PVDF and trifluoroethylene, and nylon. Examples of inorganic ferroelectric materials include lead zirconate titanate (PZT), barium titanate (BTO), lead titanate (PTO), and sodium bismuth titanate-barium titanate (BNT-BT). Preferably, the ferroelectric material containing these materials has a greater residual polarization than the polymers and / or aromatic polyamides of the present invention when subjected to polarization treatment under the same conditions.

[0151] Furthermore, the membrane thickness of the present invention is preferably 1 μm or more and 200 μm or less. When the membrane thickness is less than 1 μm, the operability sometimes deteriorates. When the membrane thickness is greater than 200 μm, the flexibility sometimes decreases, and the processability of the membrane decreases.

[0152] The piezoelectric constant d of the molded body of the present invention 31 and d 33 The lower limit of at least one of them is preferably greater than 0 pC / N, more preferably 5 pC / N or more. Furthermore, the upper limit is preferably 50 pC / N or less, more preferably 40 pC / N. As a range, it is preferably greater than 0 pC / N and less than 50.0 pC / N, more preferably greater than 0 pC / N and less than 40.0 pC / N. In this invention, the piezoelectric constant d... 31 and d 33 There are no particular limitations on the measurement method, as long as it can obtain sufficiently accurate values; any method can be used to measure and determine the value. For example, measuring the area formed by the upper and lower surfaces of the sample in a plan view, which is 6 × 10⁻⁶. -5 m 2 Aluminum electrodes are deposited separately in a repeating manner. Two leads made of aluminum foil reinforced with insulating tape can be bonded to the upper and lower planar electrodes respectively using conductive epoxy resin. Using a dynamic viscoelasticity measuring device, strain is applied to both ends of the sample at a certain frequency and amplitude, and the piezoelectric signal exhibited is measured by a recorder via a charge amplifier to calculate the amount of charge generated per unit area. In order to make the piezoelectric constant of the molded body of the present invention within the above-mentioned range, it is preferable to increase the residual polarization of the molded body by performing polarization treatment and using a stretching orientation treatment.

[0153] The lower limit of the elastic modulus of the membrane of the present invention, as measured by atomic force microscopy (AFM), is preferably 4.0 GPa or higher, more preferably 5.0 GPa or higher. Furthermore, the upper limit is preferably 15.0 GPa or lower, more preferably 7.0 GPa or lower. The range of elastic modulus is preferably 4.0 GPa or higher and 15.0 GPa or lower, more preferably 5.0 GPa or higher and 15.0 GPa or lower, and even more preferably 5.0 GPa or higher and 15.0 GPa or lower. When the elastic modulus is less than 4.0 GPa, it is prone to cracking or breakage when used as a molded body or membrane. When the elastic modulus is greater than 15.0 GPa, it is difficult to deform, and sometimes piezoelectric properties cannot be obtained. By making the elastic modulus of the membrane within the above range, excellent piezoelectricity in response to strain and / or electric field changes can be obtained, improving the responsiveness of the sensor, or widening the bandwidth of the oscillation frequency of the oscillator.

[0154] The elastic modulus measured by atomic force microscopy (AFM) can be determined through force curve mapping in AFM. AFM is a scanning probe microscope that uses atomic forces between the sample and a probe to obtain information about the sample surface. By changing the distance between the sample and the probe (which is part of the cantilever), the force acting on the probe (the deflection of the cantilever) is measured, thus obtaining a force curve. This force curve contains various information about the sample surface, and by resolving the force curve, various physicochemical properties of the sample surface can be evaluated. Force curve mapping involves scanning the sample surface parallel to the surface, acquiring the force curve at multiple points on the sample surface. The sample is fixed on the AFM sample stage, and the shape of the sample is determined using PeakForce QNM mode (a mode for continuous automatic determination of force curves at multiple points). The elastic modulus of the sample can be evaluated by resolving the elastic modulus based on the results of the force curve mapping measurement using existing software.

[0155] The lower limit of the standardized molecular orientation (MORc) of the membrane of the present invention is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. Furthermore, the upper limit is preferably 15 or less, and even more preferably 2 or less. The range of MORc is preferably 1.1 or more and 15 or less. More preferably, MORc is 1.2 or more and 15 or less, and even more preferably, MORc is 1.3 or more and 15 or less. The standardized molecular orientation (MORc) is a value determined based on the molecular orientation degree (MOR), which is an indicator of the degree of orientation of polymer chains in the membrane. The molecular orientation degree (MOR) can be measured by the following microwave measurement method.

[0156] That is, by placing a polymer piezoelectric film in a microwave resonant waveguide of a known microwave transmission type molecular orientation system, and measuring the microwave intensity transmitted through the sample by rotating it 0 to 360° in a plane perpendicular to the microwave propagation direction, the degree of molecular orientation (MOR) can be determined.

[0157] The standardized molecular orientation MORc is the degree of molecular orientation MOR when the reference thickness tc is 50 μm, and it can be calculated using the following formula.

[0158] MORc=(tc / t)×(MOR-1)+1

[0159] Where tc is the reference thickness and t is the film thickness.

[0160] The standardized molecular orientation (MORc) can be measured using a known molecular orientation meter, such as the MOR-7015 manufactured by Oji Measuring Machine Co., Ltd. When the film is a stretched film, the standardized molecular orientation (MORc) can be controlled by stretching conditions such as the film stretching ratio and stretching temperature, as well as film-forming conditions such as temperature and speed. By keeping the standardized molecular orientation (MORc) within the above-mentioned range, the orientation and / or stacking of molecular chains in the film can be improved, thereby obtaining excellent piezoelectric properties. To keep the MORc within the above-mentioned range, it is preferable to use the polymer and / or aromatic polyamide described in this invention as the main component of the molded body and / or film, or to perform uniaxial stretching.

[0161] The absolute value of the rate of change of piezoelectric constant caused by the heat treatment of the molded body and / or film of the present invention, when the piezoelectric constant after heat treatment at 150°C for 10 minutes is denoted as d', is |(d' - d'). 31 -d' 31 ) / d 31 | and | (d 33 -d' 33 ) / d 33 The value of the larger of the two values ​​is preferably 0 or more and 0.5 or less, more preferably 0 or more and 0.3 or less, and even more preferably 0 or more and 0.2 or less. By keeping the rate of change of the piezoelectric constant caused by heat treatment within the above range, the piezoelectric properties are less dependent on temperature conditions, and the performance of the sensor and actuator can be stabilized under high temperature conditions and long-term use. In order to keep the rate of change of the piezoelectric constant caused by heat treatment within the above range, it is preferable that the main component of the molded body and / or film is the polymer and / or aromatic polyamide described in this invention.

[0162] Among them, the piezoelectric constant d' after heating at 150℃ for 10 minutes 31 and d' 33 In addition to using heat-treated molded bodies and / or films as samples, the above-mentioned d 31 and d 33The same method is used for measurement. The heat treatment of the molded body and / or film is preferably performed by placing the molded body and / or film in a hot air oven set to 150°C for 10 minutes. The molded body and / or film of the present invention may contain thermosetting resins, UV-curable resins, hydrolyzed / condensed resins, alkoxysilane compounds, or other organic-inorganic hybrid resins for the purpose of adjusting mechanical properties, density, etc. Additionally, particles may be included. These particles can be inorganic or organic particles. Inorganic particles are not particularly limited and can include oxides, silicides, nitrides, borides, chlorides, carbonates, etc. of metals or half-metals. Specifically, examples include silicon dioxide (SiO2), aluminum oxide (Al2O3), zinc oxide (ZnO), zirconium oxide (ZrO2), titanium oxide (TiO2), antimony oxide (Sb2O3), and indium tin oxide (ITO). In addition, to increase ferroelectricity, lead zirconate titanate (PZT), barium titanate (BTO), lead titanate (PTO), sodium bismuth titanate-barium titanate (BNT-BT), etc., may be contained.

[0163] For the polymers, aromatic polyamides, molded bodies, films, and other contents of the present invention, when it is necessary to identify the chemical structure, the functional groups contained therein, and the composition ratio, the components can be separated by combining methods such as chromatography, distillation, liquid-liquid separation, and reprecipitation, and then analyzed by combining nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), mass spectrometry (MS), elemental analysis, and single crystal structure analysis.

[0164] The following describes the manufacturing methods of the polymer, aromatic polyamide, molded article, and solution of the present invention, but the present invention is not limited thereto.

[0165] Methods for obtaining polymers and / or aromatic polyamides can employ various known methods such as solution polymerization and precipitation polymerization. For example, in the case of polymerizing aromatic polyamides by solution polymerization, diacyl chloride and diamine can be used as raw materials, and polymerization can be carried out in an aprotic solvent at low temperature. An aprotic solvent refers to a polar solvent that does not have proton (hydrogen ion) donation capability, and examples include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylisobutyramide, 3-methoxy-N,N-dimethylpropionamide, tetrahydrofuran, γ-butyrolactone, ethyl acetate, acetonitrile, dimethylformamide, and dimethyl sulfoxide. To suppress the deactivation of diacyl chloride, it is preferable that the water content of the solvent used for polymerization is greater than 0 ppm and less than 500 ppm (by mass, the same applies below), more preferably greater than 0 ppm and less than 200 ppm. When the molar ratio of diacyl chloride to diamine is equal, ultra-high molecular weight polymers tend to form. Therefore, it is preferable to adjust the molar ratio to 96.0% to 99.8% of the diacyl chloride, more preferably 96.0% to 99.0%. In polymerization at this molar ratio, the diamine is in excess relative to the diacyl chloride, thus the terminal functional group is amino. Furthermore, the polymerization reaction of aromatic polyamides is accompanied by heat generation, but it is preferable to keep the solution temperature during polymerization below 40°C. If the temperature exceeds 40°C, side reactions may occur, and sometimes the degree of polymerization cannot be sufficiently increased. The solution temperature during polymerization is more preferably below 30°C.

[0166] In the case of using diacyl chloride and diamine as raw materials, hydrogen chloride is generated as a byproduct during the reaction, resulting in a strongly acidic solution of aromatic polyamide. This solution is highly corrosive, and direct use may corrode components such as metal substrates used in the molding process and film manufacturing, rendering them unusable. Methods for removing the generated hydrogen chloride include adding a neutralizing agent during polymerization and precipitating and separating the polymer. For example, neutralization during polymerization can be achieved using inorganic neutralizing agents such as lithium carbonate, calcium carbonate, or calcium hydroxide. In the case of neutralization with inorganic neutralizing agents, the solution contains inorganic salts (e.g., lithium chloride) generated during the neutralization reaction. These inorganic salts ionize in the solvent and coordinate with the amide groups of the aromatic polyamide, acting as solvent dissolving aids, thus effectively extending the pot life of the solution and inhibiting polymer aggregation during molding. However, a cleaning process to remove the inorganic salts is required during the molding process, so this method may not be applicable depending on the size of the molded body and / or film and the manufacturing process.

[0167] Furthermore, in cases where the polymer is precipitated and separated, the polymer solution obtained from solution polymerization is mixed with a large amount of undesirable solvent such as water, causing the polymer to precipitate in solid form. This solid polymer is then separated from the solution by filtration or similar means, thereby separating the polymer from hydrogen chloride. The separated polymer can be re-dissolved in the aforementioned aprotic solvent to form a solution. By precipitating the polymer and separating it from hydrogen chloride, no neutralization products generated from the reaction of the neutralizing agent and hydrogen chloride are present, thus reducing the amount of residual impurities in the molded body and film.

[0168] As a method for introducing electron-withdrawing and / or electron-donating groups into the aromatic polyamide of the present invention to satisfy at least one of (v) to (viii) above, examples include methods such as polymerizing aromatic polyamides using monomers having substituents with electron-withdrawing and / or electron-donating groups pre-positioned at the target position as raw materials, and methods such as polymerizing the raw material aromatic polyamide and then functionalizing it to introduce the group. In the case of introducing the group through functionalization of aromatic polyamides, methods can be listed that derive the target functional group starting from a detached group such as -H or halogen group introduced on the aromatic ring. However, depending on the functional group conversion reaction used, sometimes poor position selectivity results in a non-target structure, or insufficient reactivity leads to a low introduction rate of the functional group. Therefore, it is preferable to use monomers having substituents with electron-withdrawing and / or electron-donating groups pre-positioned as raw materials.

[0169] The molded articles and / or films of the present invention are preferably obtained by filling a solution containing the polymer and / or aromatic polyamide of the present invention into a mold or casting it onto a substrate, and then curing it. The material, shape, filling, and / or casting method of the mold and substrate are not limited and can be arbitrarily selected according to the purpose and use of the molded articles and / or films.

[0170] The membrane of the present invention can be obtained by dissolving the polymer obtained as described above in a solvent and coating it onto a substrate. The solvent is not limited as long as it can dissolve the polymer, but aprotic solvents are preferred. Furthermore, for the purpose of improving membrane properties, the solution may contain the aforementioned resin, electrolyte, particles, etc. Examples of membrane-forming methods include, for instance, a dry-wet method involving a pre-drying step, a cleaning step in a wet bath followed by heat treatment, a dry method involving solvent drying without a cleaning step, or a wet method involving heat treatment after introducing the material into a wet bath without a solvent drying step. While membrane formation can be performed using any of these methods, from the viewpoint of process simplicity and the processability of forming a membrane on an object during device manufacturing, a dry method is preferred.

[0171] The coating method for the substrate can be selected from known methods such as die coating, orifice coating, roller coating, wire rod coating, and gravure coating. The substrate can be any material that is not corroded by the raw material solution and does not deform or change under heating for solvent drying; examples include glass plates, thin-film glass, resin films, metal plates, quartz plates, and silicon wafers. Furthermore, the surface structure of the substrate can be smooth or have a fine structure.

[0172] Methods for solvent drying include hot air, infrared irradiation, and microwave irradiation, among others, with no particular limitation. The drying temperature is preferably 50–400°C. From the viewpoint of improving thermal dimensional stability, a process including a temperature range of 150–400°C in the drying step is more preferable. To prevent surface roughness due to rapid solvent evaporation, pre-drying at 50–200°C followed by staged solvent drying at 200–400°C is further preferred.

[0173] As a method for imparting residual polarization to the polymer, aromatic polyamide, molded body, and film of the present invention, stretching and polarization treatment can be performed during molding. When stretching is performed, it is preferable to stretch the film after the drying process using a stretching machine. Alternatively, polarization treatment can be performed by applying a voltage to the resulting film and / or molded body. Examples of methods for applying voltage include known DC voltage application treatment, AC voltage application treatment, and corona discharge treatment; an appropriate method can be selected based on the shape of the film or molded body. The applied electric field is preferably in the range of 10 kV / mm or more and 150 kV / mm or less. Examples of electrodes include conventionally used needle electrodes, wire electrodes, mesh electrodes, and flat plate electrodes, but the present invention is not limited to these. Furthermore, a magnetic field can also be used for polarization treatment.

[0174] The polymers, aromatic polyamides, molded articles, and films of the present invention can be well used in piezoelectric elements, sensors, actuators, vibratory plates, oscillators, and their raw materials.

[0175] The piezoelectric elements, actuators, and oscillators obtained by incorporating the molded body and / or film of the present invention are characterized in that at least one side of the molded body and / or film of the present invention has a conductive thin film. Therefore, while maintaining the same simplicity as piezoelectric elements, actuators, and oscillators comprising conventional polymer-based piezoelectric materials, excellent responsiveness and heat resistance can be achieved. The piezoelectric elements, actuators, and oscillators of the present invention can be well used as components mounted in vibration sensors, loudspeakers, etc.

[0176] The structural monitoring system of the present invention is characterized by having at least the vibration sensor and communication device described in the present invention, through which the vibration sensor diagnoses the vibration state of the structure. It is a system. The structural monitoring system of the present invention, by incorporating the vibration sensor of the present invention, can improve durability and reduce maintenance frequency. Specifically, a structural health monitoring system refers to a system that diagnoses the degree of durability of a structure by measuring the vibration state of the object structure relative to external factors such as earthquakes, vibrations generated by driving components such as motors, etc., or by monitoring annual deterioration, or calculating the timing of structural repairs.

[0177] Example

[0178] The following examples illustrate the invention in more detail.

[0179] The physical properties of this invention are evaluated in the form of a membrane as an example. The sample membranes provided for evaluating each physical property are prepared using the aromatic polyamide of this invention according to the following method.

[0180] First, the sample solution was cast into a film using a coater onto a glass plate with an Al electrode. At this point, the temperature of the sample solution, the glass plate, and the casting environment was room temperature. The casting thickness was adjusted so that the film thickness after solvent drying was 10 μm. Next, the glass plate was placed in a hot air oven and dried for 10 minutes at a temperature of Tb-50°C, where Tb is the boiling point of the aprotic solvent constituting the solution (in the case of mixed solvents, this is the boiling point of the solvent with the highest boiling point relative to the total solvent content of 30% or more by mass).

[0181] Next, an aluminum electrode layer (100 nm) was deposited onto the surface of the obtained dried film by vapor deposition. Under the condition of applying an electric field of 100 kV / mm using a DC high-voltage stabilization power supply EV10-1AVR+ (manufactured by Kasuga Electric Corporation) connected to a wire electrode, the temperature was increased to Tb+40°C at a rate of 5°C / min. This temperature was maintained for 15 minutes, and then gradually cooled to room temperature under the applied voltage, thereby performing polarization treatment.

[0182] In addition, the methods for measuring physical properties and evaluating effects in this invention are performed according to the following methods.

[0183] (1) Remanent polarization

[0184] An aluminum electrode (planar electrode) was vacuum-deposited in a 5mm × 5mm area in the center of a 20mm × 20mm sample film. Two aluminum foil leads (3mm × 80mm) reinforced with insulating tape were attached to this planar electrode using conductive double-sided tape. The sample film, function generator, high-voltage amplifier, and oscilloscope were connected to a Sawyer-Tower circuit, and a triangular wave (maximum ±10kV) was applied to the sample film. The response of the sample film was measured using the oscilloscope, thereby determining the remanent polarization under an applied electric field of 100kV / mm.

[0185] (2) Glass transition temperature

[0186] For the sample film, the glass transition temperature is determined from the inflection point of the storage modulus (E') by dynamic viscoelasticity determination (DMA) according to ASTM E1640-13. DMA is performed using the following apparatus and under the following conditions.

[0187] Apparatus: DMS6100 viscoelasticity measuring apparatus (manufactured by Seiko Instruments)

[0188] Measurement mode: Tensile mode

[0189] Measurement frequency: 1 Hz

[0190] Heating rate: 5℃ / min

[0191] Temperature range: 25℃~400℃

[0192] Duration: 2 minutes.

[0193] (3) Piezoelectric constant

[0194] Using a SINOCERA PIEZOTRONICS YE2730 piezoelectric meter or an equivalent, forces of 0.25 N and 110 Hz were applied to 10 selected points on the sample, and the d values ​​were measured. 31 and d 33 Compare the measured d 31 and d 33 The arithmetic mean of each sample is used, and the larger of these means is taken as the piezoelectric constant of that sample. Additionally, d 31 d 33 The measured value may be positive or negative depending on the front or back or direction of the sample being measured. In this specification, its absolute value is used as the measured value.

[0195] (4) Rate of change of piezoelectric constant caused by heat treatment

[0196] Let the sample stand for 10 minutes. Remove it from the hot air oven and cool it in air at room temperature. Then determine d' in the same manner as described in the piezoelectric constant section (3) above. 31 and d' 33 Using the measured d 31 d 33 ,d' 31 ,d' 33 Calculate | (d 31 -d' 31 ) / d 31 | and | (d 33 -d' 33 ) / d 33 | The larger of these values ​​is taken as the rate of change of the piezoelectric constant of the sample caused by heat treatment.

[0197] (5) Elastic modulus

[0198] Measurements were performed using an AFM (Burker Corporation Dimensionlcon) in PeakForce QNM mode. The accompanying analytical software NanoScopeAnalysis V1.40 was used for analysis based on JKR contact theory, and the elastic modulus distribution was determined from the obtained force curves.

[0199] Specifically, according to the PeakForce QNM mode manual, the bending sensitivity, elastic constant, and tip curvature of the cantilever were corrected. Then, measurements were performed under the following conditions, using the data from the DMT Modulus channel as one data point for the elastic modulus. Furthermore, the elastic constant and tip curvature may vary depending on the cantilever; however, to avoid affecting the measurement, cantilevers meeting the conditions of an elastic constant of 0.3 N / m to 0.5 N / m and a tip curvature radius of 15 nm or less were used in the measurement.

[0200] The above measurements were performed on any five samples collected, and the average of the measured data was taken as the elastic modulus of the sample membrane.

[0201] The measurement conditions are as described above.

[0202] Measurement apparatus: Atomic force microscope (AFM) manufactured by Burker Corporation.

[0203] Measurement mode: PeakForceQNM (force curve method)

[0204] Cantilever: SCANASYST-AIR manufactured by Bruker AXS

[0205] (Material: SI, elastic constant K: 0.4 N / m, tip curvature radius R: 2 nm)

[0206] Measurement environment: 23℃, atmospheric temperature

[0207] Measurement range: 3μm tetragonal

[0208] Resolution: 512×512

[0209] Cantilever movement speed: 10μm / s

[0210] Maximum indentation load: 10 nN.

[0211] (6) Standardized molecular orientation

[0212] For a sample piece cut from the sample film in the shape of 10 cm × 10 cm, the standardized molecular orientation (MORc) is determined under the following test conditions.

[0213] Measuring apparatus: OR-7015 manufactured by Oji Measurement Equipment Co., Ltd.

[0214] Frequency: 15GHz

[0215] Base thickness tc: 50mm.

[0216] (Example 1)

[0217] In dehydrated DMAc (boiling point 165°C), under a nitrogen stream, 5-nitro-m-phenylenediamine, as a diamine, was dissolved at 100 mol% relative to the total diamine content. The liquid temperature was cooled to 5°C in an ice-water bath. While maintaining the system in an ice-water bath under a nitrogen stream, 2-nitro-isophthaloyl chloride, at 99 mol% relative to the total diamine content, was added over 30 minutes. After the complete addition, stirring was carried out for approximately 1 hour, thereby polymerizing an aromatic polyamide (polymer A). The resulting polymerization solution was added to a large volume of pure water under stirring, thereby solidifying polymer A into a fibrous form. The polymer was then pulverized with a stirrer for 5 minutes, dried in a hot air oven at 80°C for 1 hour, and then dried in a vacuum oven at 120°C for 12 hours, thus obtaining polymer A powder.

[0218] Polymer A was dissolved in DMAc at a polymer concentration of 10% by mass to obtain a solution. The polymer A solution was coated as a film onto a glass plate with an Al electrode, dried in a hot air oven at 130°C for 10 minutes, and then polarized under the same conditions to obtain a 10 μm thick film formed from polymer A. The hot air oven used was a SPH100 ​​safety oven (manufactured by ESPEC Corporation), and it was used after the temperature display reached the set temperature for 1 hour with the damper on / off at 50%. The evaluation results of the obtained samples are shown in Table 1. Additionally, polymer A has Ar... 5 Chemical formula (X), Ar 6The structure described by the chemical formula (VIV) when the chemical formula is (XIII).

[0219] (Example 2)

[0220] Instead of 5-nitro-m-phenylenediamine, 5-trifluoro-m-phenylenediamine was used, and the procedure was otherwise followed in the same manner as in Example 1 to obtain aromatic polyamide (polymer B) and its film. The evaluation results of the obtained samples are shown in Table 1. Additionally, polymer B exhibits Ar... 5 Chemical formula (X), Ar 6 The structure described in chemical formula (IX) when it is chemical formula (XIII).

[0221] (Example 3)

[0222] Instead of 2-nitroisophthaloyl chloride, 3,3'-sulfonylbisbenzoyl dichloride was used, and the procedure was otherwise followed in the same manner as in Example 1 to obtain aromatic polyamide (polymer C) and its film. The evaluation results of the obtained samples are shown in Table 1. Additionally, polymer C exhibits Ar... 5 Chemical formula (X), Ar 6 The structure described in chemical formula (IX) when it is chemical formula (XIV).

[0223] (Example 4)

[0224] Instead of 5-nitro-m-phenylenediamine, 4,4'-diaminodiphenyl sulfone was used, and the procedure was otherwise followed in the same manner as in Example 1 to obtain aromatic polyamide (polymer D) and its film. The evaluation results of the obtained samples are shown in Table 1. Furthermore, polymer D exhibits Ar... 5 Chemical formula (X), Ar 6 The structure recorded in chemical formula (IX) when the chemical formula is (XI).

[0225] (Example 5)

[0226] Instead of 2-nitroisophthaloyl chloride, 2,7-naphthalenedicarboxyl chloride was used, and the procedure was otherwise followed in the same manner as in Example 1 to obtain aromatic polyamide (polymer E) and its film. The evaluation results of the obtained samples are shown in Table 1. Additionally, polymer E exhibits Ar... 3 Chemical formula (IV), Ar 4 The structure described in chemical formula (III) when it is chemical formula (V).

[0227] (Example 6)

[0228] Instead of 2-nitroisophthaloyl chloride, 1,6-naphthalenedicarboxylate chloride was used, and the procedure was otherwise followed in the same manner as in Example 1 to obtain aromatic polyamide (polymer F) and its film. The evaluation results of the obtained samples are shown in Table 1. Additionally, polymer F exhibits Ar... 3 Chemical formula (IV), Ar 4 The structure described in chemical formula (III) when it is chemical formula (VI).

[0229] (Example 7)

[0230] 2,5-Thiophenedicarboxylic acid-1,1-dioxide was dissolved in dehydrated chlorobenzene, and then oxalyl chloride, equivalent to 2.2 molar equivalents of the dicarboxylic acid, was added dropwise at room temperature. The solution was heated to 60°C and stirred for 2 hours, then returned to room temperature and subjected to vacuum distillation to remove excess oxalyl chloride. 2,5-Thiophenedicarboxylic chloride-1,1-dioxide was precipitated by adding heptane to the reaction solution. The powder was filtered off and dried under reduced pressure for further separation.

[0231] Using 2,5-thiophenedicarboxylic chloride-1,1-dioxide obtained by the above method instead of 2-nitroisophthaloyl chloride, the process was otherwise carried out in the same manner as in Example 1 to obtain aromatic polyamide (polymer G) and its film. The evaluation results of the obtained samples are shown in Table 1. In addition, polymer G does not have the structure described in either chemical formula (III) or (IX).

[0232] (Example 8)

[0233] Instead of adding 100 mol% of 5-nitro-m-phenylenediamine relative to the total diamine content, 80 mol% of 5-nitro-m-phenylenediamine and 20 mol% of 2-chloro-p-phenylenediamine relative to the total diamine content were added, and the process was otherwise identical to that in Example 1 to obtain aromatic polyamide (polymer H) and its film. The evaluation results of the obtained samples are shown in Table 1. Furthermore, polymer H has Ar... 5 Chemical formula (IX), Ar 6 The structure described in chemical formula (IX) when it is chemical formula (XIII).

[0234] (Example 9)

[0235] Instead of adding 2-nitroisophthaloyl chloride at 99 mol% relative to the total diamine content, 2-nitroisophthaloyl chloride at 80 mol% relative to the total diamine content and 2-chloroterephthaloyl chloride at 19 mol% were added, otherwise the procedure was the same as in Example 1, to obtain aromatic polyamide (polymer I) and its film. The evaluation results of the obtained samples are shown in Table 1. Additionally, polymer I has Ar... 5Chemical formula (X), Ar 6 The structure described in chemical formula (IX) when it is chemical formula (XIII).

[0236] (Example 10)

[0237] Instead of performing polarization treatment, the dried film was clamped at both ends and uniaxially stretched 1.1 times at 130°C using a stretching machine. Otherwise, the procedure was the same as in Example 1 to obtain aromatic polyamide (polymer A) and its film. The evaluation results of the obtained samples are shown in Table 1.

[0238] (Comparative Example 1)

[0239] In dehydrated DMAc, under a nitrogen stream, 100 mol% of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) was dissolved as a diamine, and the liquid temperature was cooled to 5°C in an ice-water bath. While maintaining the system in an ice-water bath under a nitrogen stream, 99 mol% of 2-chloroterephthaloyl chloride (CTPC) was added over 30 minutes. After the complete addition, stirring was carried out for approximately 1 hour, thereby polymerizing an aromatic polyamide (polymer J). The resulting polymerization solution was added to a large volume of pure water under stirring, thereby solidifying polymer J into a fibrous form. The polymer was then pulverized with a stirrer for 5 minutes, dried in a hot air oven at 80°C for 1 hour, and then dried in a vacuum oven at 120°C for 12 hours, thus obtaining polymer J powder. Subsequently, the process was repeated as in Example 1 to obtain a film formed from polymer J. The evaluation results of the obtained samples are shown in Table 1. In addition, polymer J does not have the structure described in either of the chemical formulas (III) and (IX).

[0240] (Comparative Example 2)

[0241] In dehydrated DMAc, under a nitrogen flow, 5-nitro-m-phenylenediamine, as a diamine, was dissolved at a concentration of 100 mol% relative to the total diamine content. The liquid temperature was cooled to 5°C in an ice-water bath. While maintaining the system in an ice-water bath under a nitrogen flow, CTPC, at a concentration of 99 mol% relative to the total diamine content, was added over 30 minutes. After the complete addition, stirring was performed for approximately 1 hour, thereby polymerizing an aromatic polyamide (polymer K). The resulting polymerization solution was added to a large volume of pure water under stirring, thereby solidifying polymer K into a fibrous form. The polymer was then pulverized with a stirrer for 5 minutes, dried in a hot air oven at 80°C for 1 hour, and then dried in a vacuum oven at 120°C for 12 hours, thus obtaining polymer K powder.

[0242] Polymer K was dissolved in DMAc at a polymer concentration of 10% by mass to obtain a solution. The polymer K solution was coated as a film onto a glass plate with an Al electrode, dried in a hot air oven at 130°C for 10 minutes, and then polarized under the same conditions to obtain a 10 μm thick film formed from polymer K. The evaluation results of the obtained samples are shown in Table 1. Furthermore, polymer K does not possess the structures described in either chemical formula (III) or (IX).

[0243] (Comparative Example 3)

[0244] In dehydrated DMAc (boiling point 165°C), under a nitrogen flow, m-phenylenediamine, as a diamine, was dissolved at a concentration of 100 mol% relative to the total diamine content. The liquid temperature was cooled to 5°C in an ice-water bath. While maintaining the system in an ice-water bath under a nitrogen flow, isophthaloyl chloride, at a concentration of 99 mol% relative to the total diamine content, was added over 30 minutes. After the complete addition, stirring was carried out for approximately 1 hour, thereby polymerizing an aromatic polyamide (polymer L). The resulting polymerization solution was added to a large volume of pure water under stirring, thereby solidifying polymer L into a fibrous form. The polymer was then pulverized with a stirrer for 5 minutes, dried in a hot air oven at 80°C for 1 hour, and then dried in a vacuum oven at 120°C for 12 hours, thus obtaining polymer L powder.

[0245] Polymer L was dissolved in DMAc at a polymer concentration of 10% by mass to obtain a solution. The polymer L solution was coated as a film on a glass plate with an Al electrode, dried in a hot air oven at 130°C for 10 minutes, and then polarized under the same conditions to obtain a 10 μm thick film formed from polymer L. The hot air oven used was a SPH100 ​​safety oven (manufactured by ESPEC Corporation), and the film was used after reaching the set temperature for 1 hour with the damper on / off at 50%. The evaluation results of the obtained samples are shown in Table 1. Additionally, polymer L has Ar... 3 Ar 4 The structures described in chemical formula (III) when all are chemical formula (IV).

[0246] (Comparative Example 4)

[0247] Instead of aromatic polyamide, nylon 11 (Rilsan(R)PA11, polymer M) was used, and the procedure was otherwise followed as in Example 1 to obtain a film formed from polymer M. The evaluation results of the obtained samples are shown in Table 1. In addition, polymer M does not have the structure described in either chemical formula (III) or (IX).

[0248] (Comparative Example 5)

[0249] Commercially available piezoelectric PVDF films (KF piezoelectric film, manufactured by Kureha Co., Ltd.) were used as samples for various evaluations. The evaluation results are shown in Table 1. Furthermore, PVDF does not possess the structures described in either chemical formula (III) or (IX). Standardized molecular orientation determination was not performed.

[0250]

Claims

1. A polymer having the structure shown in the following chemical formula (I) as a repeating unit, and said polymer satisfying (i) and (ii) below. (i): In chemical formula (I), the hydrogen-bonding group A is bonded to the ring atom. (ii): In chemical formula (I), the shortest path between the two atoms of A has an odd number of atoms. A is a hydrogen-bonded group, B 1 B 2 It is an n-membered cyclic group, where n is any natural number greater than 5 and less than 10.

2. The polymer of claim 1, wherein, The remanent polarization is 15 mC / m 2 Above and 300mC / m 2 the following.

3. The polymer of claim 1, wherein, The hydrogen-bonding group A is at least one of amide, urea, or carbamate groups.

4. An aromatic polyamide, which is the polymer of claim 1, wherein the hydrogen-bonding group A is an amide group, and B... 1 B 2 All of them are aromatic groups.

5. The aromatic polyamide as described in claim 4, wherein, The structure in the repeating unit satisfies at least one of the following conditions (v) to (viii): (v): In the path along the bond connecting the two amide N atoms, the atoms along the shortest path are bonded to electron-donating groups. (vi): In the path along the bond connecting the two amide carbon atoms, the atoms along the shortest path are bonded with electron-withdrawing groups. (vii): In the path along the bond connecting two amide N atoms, atoms not on the shortest path are bonded with electron-withdrawing groups. (viii): In the path along which the bond connects the two amide C atoms, the atoms not on the shortest path are bonded with electron-donating groups.

6. The aromatic polyamide of claim 5, having the molecular backbone structure shown in chemical formula (III) below, Chemical formula (III): Ar 3 Ar 4 It is a group containing the molecular skeleton structure shown in chemical formulas (IV) to (VIII). Chemical formula (IV): Chemical formula (V): Chemical formula (VI): Chemical formula (VII): R 1 To satisfy any group in claims 5 (v) to (viii), Chemical formula (VIII): R 2 For any group that satisfies (v) to (viii) in claims 5.

7. The aromatic polyamide of claim 5, having the structure shown in the following chemical formula (IX), Chemical formula (IX): Ar 5 Ar is a group containing the structure shown in chemical formulas (X) to (XII). 6 It is a group containing the structure shown in chemical formulas (XIII) to (XV). Chemical formula (X): R 3 -H or electron-donating groups, R 4 It is an electron-withdrawing group. Chemical formula (XI): R 5 As an electron-donating group, Chemical formula (XII): R 6 It is an electron-withdrawing group. Chemical formula (XIII): R 7 It is an electron-withdrawing group, R 8 It is a -H or electron-donating group. Chemical formula (XIV): R 9 It is an electron-withdrawing group. Chemical formula (XV): R 10 It is an electron-donating group.

8. The aromatic polyamide of claim 7, wherein it contains at least one group selected from perfluoroalkyl, nitro, cyano, and sulfonyl groups having 1 or more but less than 3 carbon atoms.

9. The aromatic polyamide as described in claim 4, wherein the glass transition temperature is above 130°C and below 400°C.

10. A molded article having the aromatic polyamide of claim 4 as its main component.

11. The molded article as claimed in claim 10, wherein the piezoelectric constant d 31 and d 33 At least one of them is greater than 0 pC / N and less than 50.0 pC / N.

12. A membrane having the aromatic polyamide of claim 4 as its main component.

13. The membrane as claimed in claim 12, characterized in that, The elastic modulus measured by AFM is above 4.0 GPa and below 15.0 GPa.

14. The membrane of claim 12, wherein the normalized molecular orientation MORc is 1.1 or higher and 15 or lower.

15. The molded article as claimed in claim 10, wherein, Let d' be the electrostatic constant after a 10-minute heat treatment at 150°C. The absolute value of the change in piezoelectric constant caused by the heat treatment is |(d' / d'). 31 -d' 31 ) / d 31 | and | (d 33 -d' 33 ) / d 33 The larger of the values ​​in | is greater than 0 and less than 0.

5.

16. A piezoelectric element comprising the molded body of claim 10 and / or the membrane of claim 12.

17. An actuator comprising the molded body of claim 10 and / or the membrane of claim 12.

18. An oscillator comprising the molded body of claim 10 and / or the membrane of claim 12.

19. A vibration sensor having the piezoelectric element of claim 16.

20. A loudspeaker having the actuator of claim 17.

21. A structural health monitoring system comprising at least the vibration sensor and communication device as described in claim 19, wherein the vibration sensor detects the vibration state of a structure and diagnoses the structure.

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