Polymer, aromatic polyamide, molded object, film, vibration sensor, speaker, and structural-health monitoring system

Abstract

[Problem] To provide a polymer, an aromatic polyamide, a molded object, and a film which have excellent piezoelectric properties and mechanical properties. [Solution] A polymer that has a repeating unit in which hydrogen-bonding groups are bonded to ring-member atoms and the number of atoms present on the shortest of paths which each connect an atom of one hydrogen-bonding group to an atom of another hydrogen-bonding group is an odd number, and that has a residual polarization of 15 mC / m2 to 300 mC / m2.

Description

Polymers, aromatic polyamides, moldings, films, vibration sensors, speakers, structural health monitoring systems

[0001] The present invention relates to a ferroelectric polymer, an aromatic polyamide, a molded article, and a film.

[0002] Ferroelectric materials are used in various sensors and image recording applications due to their piezoelectric and pyroelectric properties. ３ Known piezoelectric materials include inorganic materials such as lead zirconate tantalum titanate (PZT) and polymeric materials such as vinylidene fluoride polymers such as polyvinylidene fluoride (PVDF), polylactic acid, and odd-numbered nylons. Among these, inorganic materials offer advantages such as excellent pyroelectricity and heat resistance, but their poor flexibility and difficulty in processing make them unsuitable for large-area, thin-film, or complex-shaped piezoelectric elements. On the other hand, polymeric materials have lower piezoelectric and pyroelectric constants than inorganic materials, but offer favorable figures of merit due to their low specific heat and dielectric constant. These materials are being used as piezoelectric elements in applications requiring flexibility, light weight, and large areas, such as wearable devices, and are being considered for use as memory materials. In polymeric materials, unidirectional alignment of dipoles within the polymer results in the formation of remanent polarization, resulting in ferroelectricity. Dipole orientation is often achieved by controlling the higher-order structure of the polymer chain through molecular orientation and crystalline systems within the material. Examples of such methods include a method of applying an electric field to the polymer for a certain period of time to fix the structure while maintaining the electric field, which is called poling, after the polymer chains are made mobile by heating the polymer to a temperature above its glass transition temperature and below its melting point, or a method of mechanically stretching the polymer uniaxially or biaxially. However, the high-order structure is destroyed by stress and heat generated in the material during use, which deactivates the ferroelectricity, which limits the durability and usable environment, which is a problem for polymeric materials.

[0003] Aromatic polyamides are a polymeric material expected to have high durability in addition to ferroelectricity. In particular, fully aromatic polyamides have excellent heat and chemical resistance, making them useful as heat-resistant and highly elastic fibers. Furthermore, because they contain amide bonds with large dipole moments, appropriate selection of the aromatic structure is expected to result in ferroelectricity similar to that of odd-numbered nylons. Examples of such materials include a polyamide film with remanent polarization (Patent Document 1). Patent Document 2 discloses a polyamide-based liquid crystal alignment agent varnish. Patent Document 3 discloses a blend of a ferroelectric aromatic polyamide and a liquid crystalline polymer. Patent Document 4 discloses a block copolymer of a ferroelectric aromatic polyamide and a polymer having a melting point and glass transition temperature. Patent Document 5 discloses a method for producing a piezoelectric polyamide film by applying an aliphatic polyamide dissolved in an organic solvent to a substrate, drying the resulting film, heat-treating and cooling it, and then uniaxially stretching it.

[0004] Japanese Patent Laid-Open No. 8-302036 Japanese Patent Laid-Open No. 2002-363280 Japanese Patent Laid-Open No. 2002-37889 Japanese Patent Laid-Open No. 2001-279117 Japanese Patent Laid-Open No. 2020-167203

[0005] However, the aromatic polyamides disclosed in Patent Documents 1 and 2 are not fully aromatic polyamides, and the inclusion of alkyl moieties in the structure may reduce the dielectric constant and remanent polarization. Furthermore, the aromatic polyamide-based materials disclosed in Patent Documents 3 and 4 incorporate a flexible polymer structure to adjust the polymer's glass transition temperature and / or melting point to temperatures that are industrially manageable, but this may reduce the content of aromatic polyamide moieties and reduce ferroelectricity. The piezoelectric film manufacturing method disclosed in Patent Document 5 is limited to aliphatic polyamides, and differences in the polymer's solubility and packing properties make it difficult to apply the described manufacturing method to fully aromatic polyamides. Furthermore, due to the above-mentioned structural differences, the materials disclosed in Patent Documents 1 to 5 may all have inferior durability to heat and stress compared to fully aromatic polyamides.

[0006] The present invention aims to provide a molded article and / or film having excellent piezoelectric properties, mechanical properties, and heat resistance by providing a ferroelectric aromatic polyamide in which each amide group in the repeating unit is connected via an odd number of atoms and the amide group is bonded to an aromatic ring atom.

[0007] The present invention, which has been made to achieve the above object, is characterized as follows: (1) A polymer containing a structure represented by the following chemical formula (I) as a repeating unit, which satisfies the following (i) and (ii): (i): A hydrogen-bonding group A in chemical formula (I) is bonded to a ring member atom. (ii): In the chemical formula (I), the number of atoms present on the shortest path connecting the atoms of two A's is odd. Chemical formula (I):

[0008]

[0009] A is a hydrogen-bonding group, and B １ , B ２ is an n-membered ring group (where n is a natural number between 5 and 10). (2) The remanent polarization is 15 mC / m ２ 300mC / m or more ２ (3) The polymer according to (1) or (2), wherein the hydrogen-bonding group A is at least one of an amide group, a urea group, and a urethane group. (4) The polymer according to (1) or (2), wherein the hydrogen-bonding group A is an amide group, and B is １ , B ２ (5) An aromatic polyamide containing a structure represented by the following chemical formula (II) as a repeating unit, which satisfies the following (iii) and (iv), and has a remanent polarization of 15 mC / m ２ (iii): X in chemical formula (II) is bonded to an aromatic ring atom. (iv): In the chemical formula (II), the number of atoms on the shortest path connecting the atoms of two Xs is odd. Chemical formula (II):

[0010]

[0011] X is an amide group, and Ar １ , Ar ２is an aromatic group. (6) A polymer and / or aromatic polyamide according to any one of (1) to (5), wherein the structure in the repeating unit satisfies at least one of the following (v) to (viii): (v): An electron-donating group is bonded to an atom on the shortest path among the paths along the bond connecting the two amide group N atoms. (vi): An electron-withdrawing group is bonded to an atom on the shortest path among the paths along the bond connecting the two amide group C atoms. (vii): An electron-withdrawing group is bonded to an atom that is not on the shortest path among the paths along the bond connecting the two amide group N atoms. (viii): An electron-donating group is bonded to an atom that is not on the shortest path among the paths along the bond connecting the two amide group C atoms. (7) A polymer and / or aromatic polyamide according to any one of (1) to (6), which has a molecular skeleton structure represented by the following chemical formula (III): Chemical formula (III):

[0012]

[0013] Ar ３ , Ar ４ is a group containing a molecular skeleton structure represented by chemical formulas (IV) to (VIII). Chemical formula (IV):

[0014]

[0015] Chemical formula (V):

[0016]

[0017] Chemical formula (VI):

[0018]

[0019] Chemical formula (VII):

[0020]

[0021] R １ is any group that satisfies (v) to (viii) in (6). Chemical formula (VIII):

[0022]

[0023] R ２is any group satisfying (v) to (viii) in (6). (8) A polymer and / or aromatic polyamide according to any one of (1) to (7), having a structure represented by the following chemical formula (IX):

[0024]

[0025] Ar ５ includes the structures shown in chemical formulas (X) to (XII), and Ar ６ is a group containing a structure represented by chemical formulas (XIII) to (XV). Chemical formula (X):

[0026]

[0027] R ３ is —H or an electron donating group, R ４ is an electron withdrawing group.

[0028]

[0029] R ５ is an electron donating group.

[0030]

[0031] R ６ is an electron withdrawing group.

[0032]

[0033] R ７ is an electron-withdrawing group, R ８ is —H or an electron donating group.

[0034]

[0035] R ９ is an electron withdrawing group.

[0036]

[0037] R １０is an electron-donating group. (9) The polymer and / or aromatic polyamide according to any one of (1) to (8), which contains at least one group selected from the group consisting of a perfluoroalkyl group, a nitro group, a cyano group, and a sulfone group having 1 to 3 carbon atoms. (10) The polymer and / or aromatic polyamide according to any one of (1) to (9), which has a glass transition temperature of 130°C or higher and 400°C or lower. (11) A molded article containing as a main component the polymer and / or aromatic polyamide according to any one of (1) to (10). (12) A piezoelectric constant d ３１ or d ３３ (13) A film mainly composed of the polymer and / or aromatic polyamide according to any one of (1) to (10). (14) The film according to (13), characterized in that the modulus of elasticity obtained by AFM is 4.0 GPa or more and 15.0 GPa or less. (15) The film according to (13), characterized in that the normalized molecular orientation MORc is 1.1 or more and 15 or less. (16) The absolute value of the change in piezoelectric constant due to heat treatment |(d ３１ -d' ３１ ) / d ３１ | and |(d ３３ -d' ３３ ) / d ３３ |, the larger of which is 0 or more and 0.5 or less. (17) A piezoelectric element comprising the molded body according to (11) and / or the film according to (13). (18) An actuator comprising the molded body according to (11) and / or the film according to (13). (19) A vibrator comprising the molded body according to (11) and / or the film according to (13). (20) A vibration sensor comprising the piezoelectric element according to (17). (21) A speaker comprising the actuator according to (18). (22) A structural health monitoring system comprising at least the vibration sensor according to (20) and a communication device, detecting the vibration state of a structure using the vibration sensor and diagnosing the structure.

[0038] According to the present invention, the polymer and / or aromatic polyamide of the present invention can provide a molded article and / or film having excellent piezoelectric properties, mechanical properties, and heat resistance. Therefore, the polymer, aromatic polyamide, molded article, and film of the present invention can be suitably used, particularly as components for piezoelectric elements, actuators, vibrators, and the like.

[0039] The polymer of the present invention is a polymer containing a structure represented by chemical formula (I) as a repeating unit, and is characterized by satisfying the following (i) and (ii): (i): The hydrogen-bonding group A in chemical formula (I) is bonded to a ring member atom, and (ii): The number of atoms present on the shortest path connecting the atoms of two A in chemical formula (I) is odd.

[0040] By satisfying these characteristics, it is possible to simultaneously achieve excellent mechanical properties and thermal stability derived from hydrogen-bonding groups and ferroelectricity due to molecular shape and orientation. From the viewpoint of exhibiting excellent ferroelectricity, the polymer of the present invention has a remanent polarization of 15 mC / m ２ 300mC / m or more ２ It is preferable that the following holds true. Furthermore, in order to obtain efficient hydrogen bonding properties, it is preferable that the hydrogen-bonding group A in the polymer of the present invention is at least one of an amide group, a urea group, and a urethane group. The aromatic polyamide of the present invention contains a structure represented by the following chemical formula (II) as a repeating unit, and is characterized by satisfying the following (iii) and (iv): (iii): X in chemical formula (II) is bonded to an aromatic ring atom. (iv): In the path connecting the atoms of two Xs in chemical formula (II), the number of atoms present on the shortest path is odd. Chemical formula (II):

[0041]

[0042] X is an amide group, and Ar １ , Ar ２ is an aromatic group.

[0043] By satisfying these characteristics, it is possible to combine the excellent mechanical properties and thermal stability inherent in aromatic polyamide with ferroelectricity due to molecular shape and orientation.

[0044] Here, the aromatic ring atom is a constituent atom forming a ring structure in a cyclic molecular structure having aromaticity. In addition, the path connecting the atoms between two Xs in chemical formula (II) refers to a path connecting the atoms present between the atom to which one X is bonded and the atom to which the other X is bonded along the bond between the two adjacent Xs. The shortest path refers to a path in which the number of atoms present on the path connecting the atoms between the two Xs is the smallest. For example, Ar in chemical formula (II) １ , Ar ２ In the case where X is bonded to the 1st and 3rd positions of the benzene ring (the number of atoms on the shortest path is 3), or in the case where X is bonded to the 2nd and 7th positions of the naphthalene ring (the number of atoms on the shortest path is 5), both of the above (iii) and (iv) are satisfied, but in the case where X is bonded to the 1st and 4th positions of the benzene ring (the number of atoms on the shortest path is 4), (iv) is not satisfied.

[0045] The polymer and / or aromatic polyamide of the present invention has a lower limit of remanent polarization of 15 mC / m ２ The lower limit of the remanent polarization is preferably 20 mC / m or more. ２ More preferably, it is 25 mC / m or more. ２ It is more preferable that the lower limit of the remanent polarization is 15 mC / m ２ If the remanent polarization is less than 300 mC / m, the ferroelectricity is so low that piezoelectricity may not be obtained when the molded article or film is formed. ２ It is preferable that the ion concentration is 50 mC / m or less. ２ It is more preferable that the remanent polarization is in the range of 15 mC / m ２ 300mC / m or more ２ It is preferable that the ion concentration is 20 mC / m or less. ２ 300mC / m or more ２ More preferably, it is 25 mC / m or less. ２ 300mC / m or more ２ More preferably, it is 25 mC / m or less. ２ 50mC / m or more ２In order to set the remanent polarization within the above range, it is important that the aromatic polyamide contains the above-mentioned structure and that the aromatic polyamide is subjected to treatment such as stretching or poling to improve the packing and anisotropy of the aromatic polyamide. It is preferable that the structure in the repeating unit represented by chemical formula (II) of the aromatic polyamide of the present invention satisfies at least one of the following (v) to (viii):

[0046] (v): An electron-donating group is bonded to an atom on the shortest path along the bond connecting the two amide group N atoms. (vi): An electron-withdrawing group is bonded to an atom on the shortest path along the bond connecting the two amide group C atoms. (vii): An electron-withdrawing group is bonded to an atom that is not on the shortest path along the bond connecting the two amide group N atoms. (viii): An electron-donating group is bonded to an atom that is not on the shortest path along the bond connecting the two amide group C atoms.

[0047] Here, the electron-withdrawing group and the electron-donating group are determined by Hammett's substituent constant (Chem. Rev. 1991, 91, 99-257, etc.), and σ ｐ Functional groups with a positive value are electron-withdrawing groups, σ ｐ A functional group with a negative value is an electron-donating group. In the present invention, the electron-withdrawing group is preferably a group containing at least one of a perfluoroalkyl group, a sulfone group, a nitro group, and a cyano group having 1 to 3 carbon atoms, and the electron-donating group is preferably a group containing at least one of an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a hydroxy group, but is not limited to these structures. By satisfying at least one of the above (v) to (viii), a dipole moment is induced, increasing the remanent polarization and improving the piezoelectric properties.

[0048] Aromatic polyamides that satisfy these characteristics include meta-junction type wholly aromatic polyamides, and from the viewpoints of polymerizability and raw material availability, those having a structure represented by the following chemical formula (III) are particularly preferred. Chemical formula (III):

[0049]

[0050] Ar ３ , Ar ４ is a group containing the molecular skeleton structure shown in chemical formulas (IV) to (VIII), and any group satisfying any of the above (v) to (viii) may be bonded to each molecular skeleton structure. Chemical formula (IV):

[0051]

[0052] Chemical formula (V):

[0053]

[0054] Chemical formula (VI):

[0055]

[0056] Chemical formula (VII):

[0057]

[0058] R １ is any group that satisfies the above (v) to (viii). Chemical formula (VIII):

[0059]

[0060] R ２ represents any group satisfying the above (v) to (viii).

[0061] Among the above, it is particularly preferable to contain a structural unit represented by the following chemical formula (IX) in order to achieve high rigidity. Chemical formula (IX):

[0062]

[0063] Ar ５ includes the structures shown in chemical formulas (X) to (XII), and Ar ６ is a group containing a structure represented by chemical formulas (XIII) to (XV). Chemical formula (X):

[0064]

[0065] R ３ is —H or an electron donating group, R ４ is an electron withdrawing group.

[0066]

[0067] R ５ is an electron donating group.

[0068]

[0069] R ６ is an electron withdrawing group.

[0070]

[0071] R ７ is an electron-withdrawing group, R ８ is —H or an electron withdrawing group.

[0072]

[0073] R ９ is an electron withdrawing group.

[0074]

[0075] R １０ is an electron-donating group.

[0076] In the aromatic polyamide of the present invention, the number of repeating units containing the above-described structure is preferably 80% or more and 100% or less of the total number of repeating units in the polymer. If the proportion of repeating units containing the above-described structure is less than 80%, the orientation of the polymer chain or dipole moment may be deteriorated, resulting in a decrease in ferroelectricity.

[0077] The polymer and / or aromatic polyamide of the present invention preferably has a glass transition temperature of 130°C or higher, more preferably 200°C or higher. The range is preferably 130°C or higher and 400°C or lower, more preferably 200°C or higher and 400°C or lower. A glass transition temperature of 130°C or higher and 400°C or lower can prevent ferroelectricity from decreasing due to heat or aging. The glass transition temperature can be adjusted to 130°C or higher and 400°C or lower by including the above-described structure in the aromatic polyamide or by reducing the content of components with low glass transition temperatures.

[0078] An embodiment of the present invention includes a molded article and / or film containing the polymer and / or aromatic polyamide of the present invention as the main component. Here, "containing the polymer and / or aromatic polyamide as the main component" means that the polymer and / or aromatic polyamide described in the present invention is the component contained in the molded article and / or film in the largest amount. The amount of the component is not particularly limited, but the lower limit is preferably 70% by weight or more, more preferably 80% by weight or more, based on the entire film. The component amount is preferably in the range of 70% by weight to 100% by weight, more preferably 80% by weight to 100% by weight, based on the entire film, so that the mechanical properties derived from the aromatic polyamide can be more effectively exhibited.

[0079] The molded article and / or film of the present invention may contain a ferroelectric material. By including a ferroelectric material in the molded article and / or film of the present invention, the ferroelectricity may be improved, resulting in excellent piezoelectric performance. The ferroelectric material may be either an organic or inorganic material. Examples of organic ferroelectric materials include polyvinylidene fluoride (PVDF), copolymers of vinylidene fluoride and trifluoroethylene, and nylon. Examples of inorganic ferroelectric materials include lead zirconate titanate (PZT), barium titanate (BTO), lead titanate (PTO), and bismuth sodium titanate-barium titanate (BNT-BT). The ferroelectric material preferably exhibits a remanent polarization greater than that of the polymer and / or aromatic polyamide of the present invention when subjected to a poling treatment under the same conditions.

[0080] The film of the present invention preferably has a thickness of 1 μm or more and 200 μm or less. If the thickness is less than 1 μm, handling may be impaired. If the thickness is more than 200 μm, flexibility may be reduced, resulting in reduced processability as a film.

[0081] The molded article of the present invention has a piezoelectric constant d ３１ or d ３３At least one of the above is preferably greater than 0 pC / N as a lower limit, more preferably 5 pC / N or more. Also, 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 the present invention, the piezoelectric constant d ３１ and d ３３ The measurement method is not particularly limited as long as it is a method that can obtain a sufficiently accurate value, and can be measured and determined by any method. For example, －５ m ２ Aluminum electrodes are vapor-deposited on each electrode so that there is an overlap. Two leads made of aluminum foil reinforced with insulating adhesive tape are attached to the upper and lower planar electrodes using conductive epoxy resin. Using a dynamic viscoelasticity measuring device, a piezoelectric signal is generated when a displacement at a constant frequency and amplitude is applied to both ends of the sample. The piezoelectric signal is measured with a logger via a charge amplifier, and the amount of charge generated per unit area can be calculated. In order to set the piezoelectric constant of the molded product of the present invention within the above range, it is preferable to increase the remnant polarization of the molded product by performing a poling treatment or an orientation treatment by stretching.

[0082] The elastic modulus of the film of the present invention, as measured by atomic force microscopy (AFM), is preferably 4.0 GPa or more as a lower limit, and more preferably 5.0 GPa or more. The upper limit is preferably 15.0 GPa or less, and more preferably 7.0 GPa or less. The elastic modulus is preferably in the range of 4.0 GPa to 15.0 GPa. More preferably, it is 5.0 GPa to 15.0 GPa, and even more preferably, it is 5.0 GPa to 15.0 GPa. If the elastic modulus is less than 4.0 GPa, tearing or breakage may occur when used as a molded article or film. If the elastic modulus is greater than 15.0 GPa, deformation may be difficult, and piezoelectric properties may not be obtained. By setting the elastic modulus of the film within the above range, piezoelectricity with excellent responsiveness to strain and / or electric field changes can be obtained, improving the responsiveness of the sensor and widening the vibration frequency band of the vibrator.

[0083] Here, the elastic modulus obtained by AFM is measured by performing AFM force curve mapping. AFM is a scanning probe microscope that obtains information about the sample surface using the atomic force between the sample and a probe (tip). The force acting on the probe (the amount of cantilever deflection) is measured while changing the distance between the sample and the probe attached to the cantilever to obtain a force curve. This force curve contains various information about the sample surface, and analyzing the force curve allows various physicochemical properties of the sample surface to be evaluated. Force curve mapping measurement obtains this force curve at multiple points on the sample surface by scanning parallel to the sample surface. The sample is fixed to the AFM sample holder, and the topographical image of the sample is measured in PeakForceQNM mode (a mode that automatically and continuously measures force curves at multiple points). The elastic modulus of the sample can be evaluated by analyzing the elastic modulus using existing software based on the results of the force curve mapping measurement.

[0084] The normalized molecular orientation MORc of the film of the present invention is preferably 1.1 or more as a lower limit, more preferably 1.2 or more, and even more preferably 1.3 or more. The upper limit is preferably 15 or less, more preferably 2 or less. The MORc is preferably in the range of 1.1 or more and 15 or less. More preferably, the MORc is 1.2 or more and 15 or less, and even more preferably, the MORc is 1.3 or more and 15 or less. Here, the normalized molecular orientation MORc is a value determined based on the molecular orientation index MOR, which is an index indicating the degree of orientation of polymer chains in the film. The molecular orientation index MOR is measured by the following microwave measurement method.

[0085] That is, the molecular orientation (MOR) can be determined by placing a polymer piezoelectric film in a microwave resonant waveguide of a known microwave transmission type molecular orientation system, rotating it 0 to 360° in a plane perpendicular to the direction of microwave propagation, and measuring the microwave intensity transmitted through the sample. The normalized molecular orientation (MORc) is the molecular orientation (MOR) when the reference thickness (tc) is 50 μm, and can be determined by the following formula: MORc = (tc / t) × (MOR-1) + 1, where tc is the reference thickness and t is the film thickness. The normalized molecular orientation (MORc) can be measured using a known molecular orientation meter, such as the MOR-7015 manufactured by Oji Scientific Instruments Co., Ltd. When the film is a stretched film, the normalized molecular orientation (MORc) can be controlled by the stretching conditions, such as the film stretch ratio and stretching temperature, and the film formation conditions, such as the temperature and speed. By setting the normalized molecular orientation MORc within the above range, the orientation and / or packing of molecular chains in the film is improved, and excellent piezoelectric properties can be obtained. In order to set the MORc within the above range, it is preferable that the molded article and / or film contain the polymer and / or aromatic polyamide described in the present invention as the main component, or that the molded article and / or film are uniaxially stretched. When the piezoelectric constant after heat treatment at 150°C for 10 minutes is d', the absolute value of the rate of change in piezoelectric constant due to heat treatment |(d ３１ -d' ３１ ) / d ３１ | and |(d ３３ -d'３３ ) / d ３３ |, the larger value 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 due to heat treatment within the above range, the piezoelectric characteristics become less dependent on temperature conditions, and the performance of sensors and actuators can be stabilized under high temperature conditions or when used for long periods of time. In order to keep the rate of change of the piezoelectric constant due to heat treatment within the above range, it is preferable that the molded body and / or film contain the polymer and / or aromatic polyamide described in the present invention as the main component. Here, the piezoelectric constant d' after heat treatment at 150°C for 10 minutes ３１ and d' ３３ The same procedure as above d was repeated except that the heat-treated molded body and / or film was used as the sample. ３１ and d ３３ The heat treatment of the molded article and / or film is preferably carried out by leaving the molded article and / or film in a hot air oven set at 150°C for 10 minutes. The molded article and / or film of the present invention may contain organic-inorganic hybrid resins such as thermosetting resins, ultraviolet-curable resins, hydrolysis / condensation resins, and alkoxysilane compounds in order to adjust the mechanical properties and density. Particles may also be contained. Here, the particles may be either inorganic particles or organic particles. The inorganic particles are not particularly limited, but examples thereof include oxides, silicides, nitrides, borides, chlorides, and carbonates of metals and semimetals, and more specifically, silica (SiO ２ ), aluminum oxide (Al ２ O ３ ), zinc oxide (ZnO), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), antimony oxide (Sb ２ O ３ ), and indium tin oxide (ITO). For the purpose of enhancing ferroelectric properties, lead zirconate titanate (PZT), barium titanate (BTO), lead titanate (PTO), bismuth sodium titanate-barium titanate (BNT-BT), etc. may also be contained.

[0086] When it is necessary to identify the chemical structure, contained functional groups, and composition ratios of the polymer, aromatic polyamide, molded article, film, and other contents of the present invention, each component separated by a combination of techniques such as chromatography, distillation, liquid separation, and reprecipitation can be analyzed by a combination of nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), mass spectrometry (MS), elemental analysis, single crystal structure analysis, and the like.

[0087] The methods for producing the polymer, aromatic polyamide, molded article, and solution of the present invention will be described below, but the present invention is not limited thereto.

[0088] Various known methods, such as solution polymerization and precipitation polymerization, can be used to obtain polymers and / or aromatic polyamides. For example, when polymerizing aromatic polyamides by solution polymerization, the raw materials, acid dichloride and diamine, can be reacted in an aprotic solvent at low temperature. Here, the aprotic solvent is a polar solvent that does not have proton (hydrogen ion) donating properties, such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylisobutyramide, 3-methoxy-N,N-dimethylpropanamide, tetrahydrofuran, γ-butyrolactone, ethyl acetate, acetonitrile, dimethylformamide, and dimethyl sulfoxide. To prevent deactivation of the acid dichloride, the water content of the solvent used in polymerization is preferably greater than 0 ppm and less than 500 ppm (by mass, hereinafter), and more preferably greater than 0 ppm and less than 200 ppm. Since an equal molar ratio of acid dichloride to diamine tends to produce an ultrahigh molecular weight polymer, it is preferable to adjust the molar ratio so that one is 96.0 to 99.8%, more preferably 96.0 to 99.0%, of the other. When polymerization is carried out at this molar ratio, the diamine will be in excess relative to the acid dichloride, resulting in amino groups as the terminal functional groups. Furthermore, although the polymerization reaction of aromatic polyamides is exothermic, it is preferable to keep the solution temperature during polymerization below 40°C. If the temperature exceeds 40°C, side reactions may occur, preventing the degree of polymerization from increasing sufficiently. It is more preferable to keep the solution temperature during polymerization below 30°C.

[0089] When acid dichlorides and diamines are used as raw materials, hydrogen chloride is by-produced as the reaction proceeds, resulting in a highly acidic solution of the resulting aromatic polyamide. This solution is highly corrosive, and if left as is, it can corrode components such as metal substrates used in the production process of molded articles and films, making them unusable. Methods for removing the by-produced hydrogen chloride include neutralizing the hydrogen chloride by adding a neutralizing agent during polymerization, and precipitating and isolating the polymer. Neutralizing hydrogen chloride during polymerization can be achieved by neutralizing with an inorganic neutralizing agent such as lithium carbonate, calcium carbonate, or calcium hydroxide. When neutralizing with an inorganic neutralizing agent, the solution contains inorganic salts (e.g., lithium chloride) produced by the neutralization reaction. These inorganic salts ionize in the solvent and coordinate with the amide groups of the aromatic polyamide, acting as a dissolution aid in the solvent and thus improving the pot life of the solution and suppressing polymer aggregation during molding. However, because a washing step to remove the inorganic salt is required during the molding process, this method may not be usable depending on the dimensions of the molded article and / or film and the manufacturing process.

[0090] Furthermore, when isolating the polymer by precipitation, the polymer solution obtained by solution polymerization is mixed with a large amount of a poor solvent such as water to precipitate the polymer as a solid, and then the polymer and hydrogen chloride can be separated by separating the polymer from the solution by filtration or the like. The isolated polymer can be redissolved in the aforementioned aprotic solvent to form a solution. By precipitating the polymer and separating it from the hydrogen chloride, the polymer does not contain the neutralization product generated by the reaction of the neutralizing agent with hydrogen chloride, and the amount of impurities remaining in the molded article or film can be reduced.

[0091] Methods for introducing electron-withdrawing groups and / or electron-donating groups into the aromatic polyamide of the present invention so as to satisfy at least one of the above (v) to (viii) include polymerizing the aromatic polyamide from a monomer that has been previously substituted with an electron-withdrawing group and / or electron-donating group at the desired position, or polymerizing the aromatic polyamide and then functionalizing it. When introducing the groups by functionalizing the aromatic polyamide, a method is available in which the desired functional group is derived from a leaving group, such as -H or a halogen group, introduced on the aromatic group as the starting point. However, depending on the functional group conversion reaction used, poor regioselectivity may result in an undesired structure, or insufficient reactivity may result in a low introduction rate of the functional group. For this reason, the method using a monomer that has been previously substituted with an electron-withdrawing group and / or electron-donating group as the starting material is preferred.

[0092] The molded article and / or film of the present invention is preferably obtained by filling a solution containing the polymer and / or aromatic polyamide of the present invention into a mold or casting it on a substrate, followed by curing. Here, the material and shape of the mold or substrate, and the filling and / or casting method are not limited, and any method can be used depending on the purpose and use of the molded article and / or film.

[0093] The film of the present invention can be obtained by dissolving the polymer obtained as described above in a solvent and applying the solution to a substrate to form a film. The solvent is not limited as long as it dissolves the polymer, but an aprotic solvent is preferred. Furthermore, this solution may contain the aforementioned resin, electrolyte, particles, etc., for the purpose of improving the film properties. Examples of film formation methods include a dry-wet method in which a pre-drying step, a washing step in a wet bath, and then a heat treatment are performed; a dry method in which solvent drying is performed without a washing step; and a wet method in which a film is introduced into a wet bath without a solvent drying step and then a heat treatment are performed. Any of these methods may be used to form a film, but a dry method is preferred from the standpoint of process simplicity and processability, which allows a film to be formed on an object during device manufacturing.

[0094] The coating method on the substrate can be selected from known methods such as die coating, roller coating, wire bar coating, and gravure coating. The substrate may be made of any material that is not corroded by the raw material solution and does not deform or denature when heated for solvent drying, such as a glass plate, thin glass film, resin film, metal plate, quartz plate, or silicon wafer. The substrate surface may be smooth or have a fine structure. Methods for solvent drying include, but are not limited to, hot air, infrared irradiation, and microwave irradiation. The drying temperature is preferably 50 to 400°C. From the viewpoint of improving thermal dimensional stability, it is more preferable for the drying process to include a step in the temperature range of 150 to 400°C. To prevent surface roughening due to rapid solvent evaporation, it is even more preferable to perform preliminary drying at 50 to 200°C, followed by stepwise solvent drying at 200 to 400°C.

[0095] As a method for imparting remanent polarization to the polymer, aromatic polyamide, molded article, and film of the present invention, stretching or poling treatment may be performed during molding. When stretching is performed, it is preferable to stretch the film after the drying process using a stretching machine. Furthermore, poling treatment can be performed by applying a voltage to the obtained film and / or molded article. Examples of voltage application methods include known methods such as DC voltage application treatment, AC voltage application treatment, and corona discharge treatment, and an appropriate method can be selected depending on the shape of the film or molded article. The applied electric field is preferably in the range of 10 kV / mm to 150 kV / mm. Conventionally used electrodes include needle electrodes, wire electrodes, mesh electrodes, and flat electrodes, but the present invention is not limited to these. Furthermore, a magnetic field may be used for the poling treatment.

[0096] The polymers, aromatic polyamides, molded articles, and films of the present invention can be suitably used as piezoelectric elements, sensors, actuators, diaphragms, vibrators, and raw materials thereof. Piezoelectric elements, actuators, and vibrators comprising the molded articles and / or films of the present invention are characterized by having a conductive thin film on at least one surface of the molded articles and / or films of the present invention. This allows them to exhibit excellent responsiveness and heat resistance while maintaining the same ease of use as piezoelectric elements, actuators, and vibrators comprising conventional polymer-based piezoelectric materials. The piezoelectric elements, actuators, and vibrators of the present invention can be suitably used as components to be mounted on vibration sensors, speakers, and the like. The structural monitoring system of the present invention is characterized by comprising at least the vibration sensor described in the present invention and a communication device, and using the vibration sensor to diagnose the vibration state of a structure. The structural monitoring system of the present invention, including the vibration sensor of the present invention, can improve durability and reduce maintenance frequency. Here, a structural health monitoring system is a system that measures the vibration state of a target structure in response to external factors such as earthquakes and vibrations generated by driving units such as motors, thereby diagnosing the structure's durability, detecting deterioration over time, and calculating the timing of structural repairs.

[0097] The present invention will be described in more detail below with reference to examples.

[0098] The respective physical properties in the present invention were evaluated in the form of a film, for example. The sample films to be subjected to the evaluation of the respective physical properties were prepared using the aromatic polyamide of the present invention according to the following method.

[0099] First, a sample solution was cast into a film form using an applicator onto a glass plate equipped with an Al electrode. The temperatures of the sample solution, glass plate, and casting atmosphere were all room temperature. The cast thickness was adjusted so that the film thickness after solvent drying would be 10 μm. Next, the glass plate was placed in a hot air oven and dried for 10 minutes at Tb-50°C, where Tb is the boiling point of the aprotic solvents constituting the solution (in the case of a mixed solvent, the boiling point of the solvent with the highest boiling point among the solvents contained in an amount of 30% by mass or more of the total solvent amount).

[0100] Next, an aluminum electrode layer (100 nm) was attached to the surface of the obtained dried film by vapor deposition, and the temperature was raised to Tb+40°C at a rate of 5°C / min while an electric field of 100 kV / mm was applied using a DC high-voltage stabilized power supply EV10-1AVR+ (manufactured by Kasuga Electric Co., Ltd.) connected to a wire electrode. After maintaining this temperature for 15 minutes, the film was slowly cooled to room temperature with the voltage still applied, thereby performing a poling treatment.

[0101] In the present invention, the methods for measuring physical properties and evaluating effects were as follows.

[0102] (1) Residual Polarization An aluminum electrode (planar electrode) was vacuum-deposited onto the central 5 mm x 5 mm area of ​​a 20 mm x 20 mm sample film. Two aluminum foil leads (3 mm x 80 mm) reinforced with insulating tape were attached to the planar electrode with conductive double-sided tape. The sample film, a function generator, a high-voltage amplifier, and an oscilloscope were incorporated into a Sawyer-Tower circuit, and a triangular wave (maximum ±10 kV) was applied to the sample film. The response of the sample film was measured using an oscilloscope to determine the remnant polarization at an applied electric field of 100 kV / mm.

[0103] (2) Glass Transition Temperature The glass transition temperature of the sample film was determined from the inflection point of the storage modulus (E') by dynamic mechanical analysis (DMA) in accordance with ASTM E1640-13. DMA was performed using the following apparatus and conditions.

[0104] Apparatus: Viscoelasticity measuring apparatus DMS6100 (manufactured by Seiko Instruments Inc.) Measurement mode: Tensile mode Measurement frequency: 1 Hz Heating rate: 5°C / min Temperature range: 25°C to 400°C Holding time: 2 min.

[0105] (3) Piezoelectric constant: Measured by applying a force of 0.25 N, 110 Hz using a piezometer YE2730 manufactured by SINOCERA PIEZOTRONICS or an equivalent. ３１ and d ３３ was measured at 10 selected points on each sample. ３１and d ３３ The arithmetic mean values ​​were compared, and the larger mean value was taken as the value of the piezoelectric constant of the sample. ３１ , d ３３ The measured value of is a positive or negative value depending on the front or back and orientation of the sample being measured, but in this specification, the absolute value is treated as the measured value.

[0106] (4) Rate of change in piezoelectric constant due to heat treatment The sample was left standing for 10 minutes. After removing it from the hot air oven and cooling it to room temperature, d' was measured in the same manner as in the method described in (3) above for the piezoelectric constant. ３１ and d' ３３ The obtained d ３１ , d ３３ , d' ３１ , d' ３３ Using |(d ３１ -d' ３１ ) / d ３１ | and |(d ３３ -d' ３３ ) / d ３３ The larger of these values ​​was determined as the rate of change in the piezoelectric constant of the sample due to the heat treatment.

[0107] (5) Elastic Modulus Measurement was performed using an AFM (Dimension Icon manufactured by Burker Corporation) in PeakForceQNM mode, and the obtained force curve was analyzed based on the JKR contact theory using the attached analysis software NanoScopeAnalysis V1.40 to determine the elastic modulus distribution.

[0108] Specifically, the cantilever's warpage sensitivity, spring constant, and tip curvature were calibrated according to the PeakForceQNM mode manual, and then measurements were performed under the following conditions. The resulting data from the DMT Modulus channel was used as the single data point for the modulus of elasticity. While the spring constant and tip curvature vary depending on the individual cantilever, cantilevers that met the conditions of a spring constant of 0.3 N / m to 0.5 N / m and a tip curvature radius of 15 nm or less were used for the measurements, within the range that would not affect the measurement. The above measurements were performed on five randomly selected samples, and the number average of the obtained data was used as the modulus of elasticity for the sample film.

[0109] The measurement conditions are as follows: Measurement device: Atomic force microscope (AFM) manufactured by Bruker Corporation Measurement mode: PeakForceQNM (force curve method) Cantilever: SCANASYST-AIR manufactured by Bruker AXS (material: Si, spring constant K: 0.4 N / m, tip curvature radius R: 2 nm) Measurement atmosphere: 23°C, in air Measurement range: 3 μm square Resolution: 512 × 512 Cantilever movement speed: 10 μm / s Maximum indentation load: 10 nN.

[0110] (6) Normalized Molecular Orientation A sample piece measuring 10 cm x 10 cm was cut out from the sample film, and the normalized molecular orientation MORc was measured under the following measurement conditions: Measuring device: MOR-7015 manufactured by Oji Scientific Instruments Co., Ltd. Frequency: 15 GHz Reference thickness tc: 50 mm.

[0111] Example 1 5-nitro-m-phenylenediamine, equivalent to 100 mol % of the total diamine amount, was dissolved in dehydrated DMAc (boiling point 165°C) under a nitrogen stream, and the solution was cooled to 5°C in an ice-water bath. While the system was maintained in the ice-water bath under a nitrogen stream, 2-nitroisophthalic acid dichloride, equivalent to 99 mol % of the total diamine amount, was added over 30 minutes. After the entire amount was added, the mixture was stirred for approximately 1 hour to polymerize an aromatic polyamide (polymer A). The resulting polymerization solution was added to a large amount of pure water with stirring to solidify polymer A into a fibrous form, which was then pulverized in a mixer for 5 minutes and dried in a hot air oven at 80°C for 1 hour and in a vacuum oven at 120°C for 12 hours to obtain a powder of polymer A. Polymer A was dissolved in DMAc to obtain a polymer concentration of 10% by mass, thereby obtaining a solution. A solution of polymer A was applied in the form of a film on a glass plate with an Al electrode, dried in a hot air oven at 130°C for 10 minutes, and then subjected to poling treatment under the above conditions to obtain a film of polymer A with a thickness of 10 μm. Here, a safety oven SPH100 ​​(manufactured by Espec Corporation) was used as the hot air oven, and it was used one hour after the temperature display reached the set temperature with the open / close damper at 50%. The evaluation results of the obtained sample are shown in Table 1. Polymer A was prepared by the method described above. ５ is the chemical formula (X), Ar ６ is formula (XIII), and has a structure according to formula (VIV).

[0112] Example 2 An aromatic polyamide (Polymer B) and a film thereof were obtained in the same manner as in Example 1, except that 5-trifluoro-m-phenylenediamine was used instead of 5-nitro-m-phenylenediamine. The evaluation results of the obtained sample are shown in Table 1. Polymer B was prepared by the same method as in Example 1, except that 5-trifluoro-m-phenylenediamine was used instead of 5-nitro-m-phenylenediamine. ５ is the chemical formula (X), Ar ６ is formula (XIII), and has a structure according to formula (IX).

[0113] Example 3 An aromatic polyamide (Polymer C) and a film thereof were obtained in the same manner as in Example 1, except that 3,3'-sulfonylbisbenzoic acid dichloride was used instead of 2-nitroisophthalic acid dichloride. The evaluation results of the obtained sample are shown in Table 1. Polymer C was prepared by the method described in Example 1. ５ is the chemical formula (X), Ar ６ is formula (XIV), and has a structure according to formula (IX).

[0114] Example 4 An aromatic polyamide (Polymer D) and a film thereof were obtained in the same manner as in Example 1, except that 4,4'-diaminodiphenyl sulfone was used instead of 5-nitro-m-phenylenediamine. The evaluation results of the obtained sample are shown in Table 1. Polymer D was obtained by the same method as in Example 1, except that 4,4'-diaminodiphenyl sulfone was used instead of 5-nitro-m-phenylenediamine. ５ is the chemical formula (X), Ar ６ is formula (XI), and has a structure according to formula (IX).

[0115] Example 5 An aromatic polyamide (Polymer E) and a film thereof were obtained in the same manner as in Example 1, except that 2,7-naphthalenedicarbonyl dichloride was used instead of 2-nitroisophthalic acid dichloride. The evaluation results of the obtained sample are shown in Table 1. Polymer E was prepared by the same method as in Example 1, except that 2,7-naphthalenedicarbonyl dichloride was used instead of 2-nitroisophthalic acid dichloride. ３ is represented by the chemical formula (IV), Ar ４ is formula (V), and has a structure according to formula (III).

[0116] Example 6 An aromatic polyamide (Polymer F) and a film thereof were obtained in the same manner as in Example 1, except that 1,6-naphthalenedicarbonyl dichloride was used instead of 2-nitroisophthalic acid dichloride. The evaluation results of the obtained sample are shown in Table 1. Polymer F was obtained by the method described in Example 1. ３ is represented by the chemical formula (IV), Ar ４ is formula (VI), and has a structure according to formula (III).

[0117] Example 7: 2,5-thiophenedicarboxylic acid-1,1-dioxide was dissolved in dehydrated chlorobenzene, and oxalyl chloride equivalent to 2.2 molar equivalents relative to 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 evaporated under reduced pressure to remove excess oxalyl chloride. 2,5-thiophenedicarboxylic acid dichloride-1,1-dioxide was precipitated by adding heptane to the reaction solution. The powder was filtered and then isolated by drying under reduced pressure. An aromatic polyamide (Polymer G) and a film thereof were obtained in the same manner as in Example 1, except that the 2,5-thiophenedicarboxylic acid dichloride-1,1-dioxide obtained by the above method was used instead of 2-nitroisophthalic acid dichloride. The evaluation results of the obtained sample are shown in Table 1. Polymer G does not have either of the structures shown in chemical formulas (III) and (IX).

[0118] Example 8 An aromatic polyamide (Polymer H) and a film thereof were obtained in the same manner as in Example 1, except that instead of adding 5-nitro-m-phenylenediamine in an amount equivalent to 100 mol % of the total amount of diamine, 5-nitro-m-phenylenediamine in an amount equivalent to 80 mol % of the total amount of diamine and 2-chloro-p-phenylenediamine in an amount equivalent to 20 mol % of the total amount of diamine were added. The evaluation results of the obtained sample are shown in Table 1. Polymer H was prepared by adding Ar ５ is represented by the chemical formula (IX), Ar ６ is formula (XIII):

[0119] Example 9 An aromatic polyamide (Polymer I) and a film thereof were obtained in the same manner as in Example 1, except that 2-nitroisophthalic acid dichloride corresponding to 80 mol % and 2-chloroterephthalic acid dichloride corresponding to 19 mol % of the total amount of diamine were added instead of 2-nitroisophthalic acid dichloride corresponding to 99 mol % of the total amount of diamine. The evaluation results of the obtained sample are shown in Table 1. Polymer I was prepared by adding Ar ５ is the chemical formula (X), Ar ６is represented by chemical formula (XIII), and includes a structure represented by chemical formula (IX). (Example 10) An aromatic polyamide (polymer A) and a film thereof were obtained in the same manner as in Example 1, except that instead of performing a poling treatment, both ends of the dried film were supported and uniaxially stretched to 1.1 times at 130°C using a stretching machine. The evaluation results of the obtained sample are shown in Table 1. (Comparative Example 1) 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) as a diamine, equivalent to 100 mol% based on the total amount of diamine, was dissolved in dehydrated DMAc under a nitrogen stream, and the liquid temperature was cooled to 5°C in an ice-water bath. To this, 2-chloroterephthaloyl chloride (CTPC), equivalent to 99 mol% based on the total amount of diamine, was added over 30 minutes while the system was maintained in the ice-water bath under a nitrogen stream. After the entire amount was added, the mixture was stirred for about 1 hour, thereby polymerizing an aromatic polyamide (polymer J). The obtained polymerization solution was added to a large amount of pure water while stirring to solidify Polymer J into a fibrous form, which was then pulverized in a mixer for 5 minutes and dried in a hot air oven at 80°C for 1 hour and in a vacuum oven at 120°C for 12 hours to obtain a powder of Polymer J. Thereafter, a film made of Polymer J was obtained in the same manner as in Example 1. The evaluation results of the obtained sample are shown in Table 1. Note that Polymer J does not have any of the structures described in chemical formulas (III) and (IX).

[0120] Comparative Example 2: 5-nitro-m-phenylenediamine, equivalent to 100 mol % of the total diamine amount, was dissolved in dehydrated DMAc under a nitrogen stream, and the solution was cooled to 5°C in an ice-water bath. While the system was maintained in the ice-water bath under a nitrogen stream, CTPC, equivalent to 99 mol % of the total diamine amount, was added over 30 minutes. After the entire amount was added, the mixture was stirred for approximately 1 hour to polymerize an aromatic polyamide (polymer K). The resulting polymerization solution was added to a large amount of pure water with stirring to solidify polymer K into a fibrous form. The polymer was then pulverized in a mixer for 5 minutes, and dried in a hot air oven at 80°C for 1 hour and in a vacuum oven at 120°C for 12 hours to obtain a powder of polymer K. Polymer K was dissolved in DMAc to a polymer concentration of 10% by mass, thereby obtaining a solution. A solution of polymer K was applied in the form of a film onto a glass plate equipped with an Al electrode, dried in a hot air oven at 130°C for 10 minutes, and then subjected to poling treatment under the conditions described above to obtain a film of polymer K having a thickness of 10 μm. The evaluation results of the obtained sample are shown in Table 1. Note that polymer K does not have either of the structures described in chemical formulas (III) and (IX).

[0121] Comparative Example 3: In dehydrated DMAc (boiling point 165°C), m-phenylenediamine, equivalent to 100 mol% of the total diamine amount, was dissolved under a nitrogen stream, and the solution was cooled to 5°C in an ice-water bath. While the system was maintained in an ice-water bath under a nitrogen stream, isophthalic acid dichloride, equivalent to 99 mol% of the total diamine amount, was added over 30 minutes. After the entire amount was added, the mixture was stirred for approximately 1 hour to polymerize an aromatic polyamide (Polymer L). The resulting polymerization solution was added to a large amount of pure water with stirring to solidify Polymer L into a fibrous form, which was then pulverized in a mixer for 5 minutes and dried in a hot air oven at 80°C for 1 hour and in a vacuum oven at 120°C for 12 hours to obtain a powder of Polymer L. Polymer L was dissolved in DMAc to obtain a polymer concentration of 10% by mass, thereby obtaining a solution. A solution of polymer L was applied in the form of a film on a glass plate with an Al electrode, dried in a hot air oven at 130°C for 10 minutes, and then subjected to poling treatment under the above conditions to obtain a film of polymer L with a thickness of 10 μm. Here, a safety oven SPH100 ​​(manufactured by Espec Corporation) was used as the hot air oven, and it was used one hour after the temperature display reached the set temperature with the open / close damper at 50%. The evaluation results of the obtained sample are shown in Table 1. Polymer L was prepared by the method described above using Ar ３ , Ar ４ and (III) are both of formula (IV).

[0122] Comparative Example 4 A film made of polymer M was obtained in the same manner as in Example 1, except that nylon 11 (Rilsan® PA11, polymer M) was used instead of aromatic polyamide. The evaluation results of the obtained sample are shown in Table 1. Note that polymer M does not have any of the structures shown in chemical formulas (III) and (IX).

[0123] (Comparative Example 5) A commercially available piezoelectric PVDF film (KF Piezofilm, manufactured by Kureha Corporation) was used as a sample and various evaluations were performed. The evaluation results are shown in Table 1. Note that the PVDF does not have any of the structures shown in chemical formulas (III) and (IX). Normalized molecular orientation measurement was not performed.

[0124]

Claims

1. A polymer containing a structure represented by the following chemical formula (I) as a repeating unit, which satisfies the following (i) and (ii): (i): The hydrogen-bonding group A in chemical formula (I) is bonded to a ring member atom. (ii): In the path connecting the atoms of two A in chemical formula (I), the number of atoms present on the shortest path is an odd number. Chemical formula (I): A is a hydrogen bonding group, B １ , B ２ represents an n-membered ring group (where n is a natural number of 5 or more and 10 or less).

2. Residual polarization is 15mC / m ２ 300mC / m or more ２ 2. The polymer of claim 1 , wherein:

3. The polymer according to claim 1, wherein the hydrogen-bonding group A is at least one of an amide group, a urea group, and a urethane group.

4. The polymer according to claim 1, wherein the hydrogen-bonding group A is an amide group and B is an amide group. １ , B ２ are aromatic groups.

5. The aromatic polyamide according to claim 4, wherein the structure in the repeating unit satisfies at least any one of the following (v) to (viii): (v): an electron-donating group is bonded to an atom on the shortest path among paths along the bond connecting two amide group N atoms; (vi): an electron-withdrawing group is bonded to an atom on the shortest path among paths along the bond connecting two amide group C atoms; (vii): an electron-withdrawing group is bonded to an atom that is not on the shortest path among paths along the bond connecting two amide group N atoms; (viii): an electron-donating group is bonded to an atom that is not on the shortest path among paths along the bond connecting two amide group C atoms.

6. The aromatic polyamide according to claim 5, having a molecular skeleton structure represented by the following chemical formula (III): Chemical formula (III): Ar ３ , Ar ４ is a group containing a molecular skeleton structure represented by chemical formulas (IV) to (VIII). Chemical formula (IV): Chemical formula (V): Chemical formula (VI): Chemical formula (VII): R １ is any group satisfying (v) to (viii) in claim 5. Chemical formula (VIII): R ２ represents any group satisfying (v) to (viii) in claim 5.

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

8. The aromatic polyamide according to claim 7, which contains at least one of a perfluoroalkyl group having 1 to 3 carbon atoms, a nitro group, a cyano group, and a sulfone group.

9. The aromatic polyamide according to claim 4, having a glass transition temperature of 130°C or higher and 400°C or lower.

10. A molded article comprising as a main component the aromatic polyamide according to claim 4.

11. Piezoelectric constant d ３１ Or d ３３ The molded article according to claim 10, wherein at least one of the above is greater than 0 pC / N and less than 50.0 pC / N.

12. A film comprising as a main component the aromatic polyamide according to claim 4.

13. The film according to claim 12, characterized in that the elastic modulus obtained by AFM is 4.0 GPa or more and 15.0 GPa or less.

14. The film according to claim 12, having a normalized molecular orientation MORc of 1.1 or more and 15 or less.

15. If the electrostatic constant after heat treatment at 150°C for 10 minutes is d', what is the absolute value of the change in the piezoelectric constant due to heat treatment |(d ３１ -d' ３１ ) / d ３１ | and |(d ３３ -d' ３３ ) / d ３３ The molded body according to claim 10, wherein the larger value of | is 0 or more and 0.5 or less.

16. A piezoelectric element comprising the molded article according to claim 10 and / or the film according to claim 12.

17. An actuator comprising the molded article according to claim 10 and / or the film according to claim 12.

18. A vibrator comprising the molded article according to claim 10 and / or the film according to claim 12.

19. A vibration sensor comprising the piezoelectric element according to claim 16.

20. A speaker comprising the actuator according to claim 17.

21. A structural health monitoring system comprising at least the vibration sensor according to claim 19 and a communication device, for detecting the vibration state of a structure by the vibration sensor and diagnosing the structure.

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