Composite, elastomer, method for producing the same, actuator, and sensor

Abstract

Provided is a polymer containing: a unit (A) originating from a (meth)acrylate monomer having an ether structure; and a unit (B) originating from (meth)acrylamide having a cyano group.

Description

Technical Field

[0001] The present invention relates to polymers, elastomers, methods for producing the same, actuators, and sensors, and more particularly to polymers and elastomers that can be suitably used as dielectric elastomers.

Background Art

[0002] In recent years, various elastomers have been developed and their applications have also expanded. For example, as an elastomer used for a dielectric material or the like, a dielectric elastomer capable of displacing its shape by applying a voltage is known. Dielectric elastomers can be used for applications such as actuators, sensors used in industrial robots, power generation elements, speakers, microphones, noise cancelers, transducers, artificial muscles, small pumps, and medical instruments. For example, in order to provide a dielectric elastomer material having a large relative permittivity and flexibility, a technique related to a dielectric elastomer using a copolymer having a polar group has been proposed (for example, see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 described above discloses the use of a monomer in which a polar group is bonded to a polymer main chain via three or more atoms connected in a straight chain, and a cyano group is exemplified as one type of polar group.

[0005] However, even when using monomers that meet the above requirements, there is still room for improvement from the perspectives of the types of monomers having polar groups and the combinations with monomers to be combined with the monomers, and further development of polymers with higher dielectric constants and excellent displacement amounts is expected.

[0006] An object of the present invention is to provide a polymer capable of forming an elastomer having a high dielectric constant and excellent displacement amount when a voltage is applied in order to solve the above problems. Another object of the present invention is to provide an elastomer having high flexibility and dielectric constant, excellent in displacement amount when a voltage is applied, a method for producing the same, and an actuator and a sensor using the elastomer.

Means for Solving the Problems

[0007] <1> A unit (A) derived from a (meth)acrylate monomer having an ether structure, and A unit (B) derived from a (meth)acrylamide having a cyano group, and A polymer containing the same. <2> The polymer according to <1>, wherein the (meth)acrylate monomer having an ether structure is represented by the following formula (1).

Chemical Formula

Chemical Formula

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a polymer capable of forming an elastomer having a high dielectric constant and excellent displacement amount when a voltage is applied. Further, according to the present invention, it is possible to provide an elastomer having high flexibility and dielectric constant, excellent in displacement amount when a voltage is applied, a method for producing the same, and an actuator and a sensor using the elastomer.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described, but the content of the present invention is not limited to the following description. Also, throughout this specification, when referred to as “(meth)acrylate” or the like, it means “acrylate” or “methacrylate”. Further, unless otherwise specified, when referred to as “alkyl group”, it includes linear, branched and alicyclic alkyl groups. Furthermore, when indicating a numerical range using “~”, it includes the numerical values at both ends thereof.

[0011] 《Polymer of the Present Embodiment》 The polymer of the present embodiment includes a unit (A) derived from a (meth)acrylate monomer having an ether structure (hereinafter sometimes simply referred to as “unit (A)”) and a unit (B) derived from a (meth)acrylamide having a cyano group (hereinafter sometimes simply referred to as “unit (B)”).

[0012] Throughout this specification, “the polymer of the present embodiment” means a polymer containing unit (A) and unit (B) as constituent units, and includes any of liquid, solid, uncured and cured states. Also, “the elastomer of the present embodiment” is an elastomer (elastic body) containing the polymer of the present embodiment, and when the polymer of the present embodiment itself functions as an elastic body, the polymer of the present embodiment itself can be referred to as the elastomer of the present embodiment. Further, the elastomer of the present embodiment may contain various additives as necessary in addition to the polymer of the present embodiment.

[0013] The polymer of the present embodiment includes a relatively highly polar and flexible unit (A) derived from a (meth)acrylate monomer having an ether structure (hereinafter sometimes simply referred to as "monomer (A)"), and a highly polar unit (B) derived from a (meth)acrylamide having a cyano group (hereinafter sometimes simply referred to as "monomer (B)"). By including these, it is possible to achieve both excellent dielectric constant and displacement amount during voltage application in a high dimension. The polymer of the present embodiment is particularly suitable for use as a dielectric elastomer that can be used in applications such as actuators, sensors used in industrial robots, power generation elements, speakers, microphones, noise cancelers, transducers, artificial muscles, small pumps, and medical instruments. Note that by achieving both a high dielectric constant and high flexibility (low Young's modulus) of the polymer or elastomer, the displacement amount during voltage application can be increased.

[0014] <Unit (A)> The polymer of the present embodiment includes, as a constituent unit, a unit (A) derived from a (meth)acrylate monomer (monomer (A)) having an ether structure. Monomer (A) is a (meth)acrylate having a (meth)acrylate structure in its structure and containing at least one ether structure (-C-O-C-) other than the said structure. The number of ether structures other than the (meth)acrylate structure in unit (A) is not particularly limited, but from the viewpoint of the balance between dielectric constant and flexibility, 1 to 3 are preferable, 1 or 2 are more preferable, and 1 is even more preferable.

[0015] Monomer (A) preferably has a high dissolving power (solubility) with respect to monomer (B) to be combined. When using monomer (A) having a high dissolving power, even when monomer (B) is a solid substance at normal temperature, monomer (B) can be dissolved, and thus, without using a solvent, for example, the polymer of the present embodiment can be synthesized by the bulk polymerization method described later. According to the bulk polymerization method, the polymer of the present embodiment can be polymerized to a high molecular weight as desired.

[0016] The solubility of monomer (B) in 100 g of monomer (A) (under 1 atm, liquid temperature 25 °C) is preferably 1 mass% or more, more preferably 10 mass% or more, still more preferably 30 mass% or more, and particularly preferably 40 mass% or more from the viewpoints of improving the dielectric constant and the displacement amount when a voltage is applied. The solubility can be determined, for example, by dropping monomer (B) into 10 g of monomer (A), heating and mixing at 50 °C, checking the state after cooling, and taking the upper limit concentration at which no insoluble matter can be visually confirmed after cooling and a uniform solution is obtained as the solubility of monomer (B).

[0017] As the (meth)acrylate monomer having an ether structure, monomer (A) represented by the following formula (1) can be used. Monomer (A) represented by formula (1) has a relatively high dielectric constant and excellent flexibility. Also, monomer (A) represented by formula (1) is advantageous from the viewpoint of the dissolving power for monomer (B) represented by formula (2) described later.

[0018] [Chemical formula] (In the formula, R 1 represents a hydrogen atom or a methyl group. R 2 represents an alkyl group having 1 to 5 carbon atoms which may have a halogen atom. X 1 represents an alkylene group having 1 to 10 carbon atoms which may have a halogen atom. n represents an integer of 1 to 3.)

[0019] In formula (1), R 1 is a hydrogen atom or a methyl group. Among them, a hydrogen atom is preferable from the viewpoints of ease of polymerization and obtaining a polymer with a low Young's modulus.

[0020]

[0021] In formula (1), R 2 is an alkyl group having 1 to 5 carbon atoms which may have a halogen atom. The alkyl group may be linear, branched or cyclic, but from the viewpoint of the dielectric constant, a linear alkyl group is preferable.

[0021] Examples of the alkyl group having 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a sec-butyl group, an n-pentyl group, an isoamyl group, and the like. Among these, R 2 is preferably a linear alkyl group having 1 to 4 carbon atoms from the viewpoint of dielectric constant, and more preferably a methyl group, an ethyl group, or a propyl group.

[0022] Examples of the halogen atom that may be included in the alkyl group include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like. The number of halogen atoms contained in the alkyl group varies depending on the number of carbon atoms of the alkyl group and the like, and thus cannot be determined unconditionally, but it is preferably adjusted as appropriate within a range that does not inhibit the object of the present embodiment.

[0023] Examples of the alkyl group having 1 to 5 carbon atoms having a halogen atom include a trifluoromethyl group, a trifluoroethyl group, a trifluoro-n-propyl group, a trifluoroisopropyl group, a trifluoro-n-butyl group, a trifluoroisobutyl group, a trifluorotert-butyl group, and the like, but the present embodiment is not limited only to these examples.

[0024] In formula (1), X 1 is an alkylene group having 1 to 10 carbon atoms that may have a halogen atom. The alkylene group may be linear, branched, or cyclic, but is preferably a linear alkylene group from the viewpoint of dielectric constant.

[0025] Examples of the alkylene group having 1 to 10 carbon atoms include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, a tert-butylene group, a sec-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, and the like. Among these, X 1From the perspective of dielectric constant, a linear alkylene group having 1 to 6 carbon atoms is preferred, a linear alkylene group having 1 to 4 carbon atoms is more preferred, and a methylene group and an ethylene group are particularly preferred. Also, the alkylene group represented by X 1 may have the above-mentioned halogen atom as a substituent.

[0026] In formula (1), n is an integer of 1 to 3. Although not particularly limited, from the perspective of dielectric constant, n is preferably 1 or 2, and more preferably 1.

[0027] Examples of the monomer (A) represented by formula (1) include methoxyethyl (meth)acrylate (MTA), ethoxyethyl (meth)acrylate, methoxymethyl (meth)acrylate, methoxypropyl (meth)acrylate, ethoxymethyl (meth)acrylate, and (meth)acrylate monomers having an alkyl group containing a plurality of ether structures (for example, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, etc.). From the perspective of dielectric constant, methoxyethyl (meth)acrylate (MTA) and methoxypropyl (meth)acrylate are preferred. These monomers (A) may be used alone or in combination of two or more.

[0028] In addition, examples of the monomer (A) other than the monomer (A) represented by formula (1) include (meth)acrylate monomers having an alkyl group containing a cyclic ether structure such as tetrahydrofurfuryl acrylate.

[0029] <Unit (B)> The polymer of this embodiment contains, as a constituent unit, a unit (B) derived from a (meth)acrylamide having a cyano group (monomer (B)). The monomer (B) is a (meth)acrylamide having a (meth)acrylamide structure in the structure and further containing at least one cyano group (CN-). The number of cyano groups in the unit (B) is not particularly limited, but from the perspective of dielectric constant, 1 to 2 are preferred, and 1 is preferred.

[0030] As the (meth)acrylamide having a cyano group, the monomer (B) represented by the following formula (2) can be used. The monomer (B) represented by the formula (2) has a particularly high dielectric constant.

[0031]

Chemical formula

[0032] In formula (2), R 1 is a hydrogen atom or a methyl group. Among R 1 , a hydrogen atom is preferable from the viewpoints of ease of polymerization and obtaining a polymer with a low Young's modulus.

[0033] In formula (2), R 3 is a hydrogen atom or a methyl group. Among R 3 , a hydrogen atom is preferable from the viewpoint of Young's modulus.

[0034] In formula (2), X 2 is an alkylene group having 1 to 10 carbon atoms which may have a halogen atom. The alkylene group may be linear, branched or cyclic, but from the viewpoint of dielectric constant, a linear alkyl group is preferable.

[0035] Examples of the alkylene group having 1 to 10 carbon atoms include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, a tert-butylene group, a sec-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, and the like. Among these, X 2From the perspective of dielectric constant, a linear alkylene group having 1 to 5 carbon atoms is preferable, a linear alkylene group having 1 to 3 carbon atoms is more preferable, and a methylene group and an ethylene group are preferable. Further, the alkylene group represented by X 2 may have the above-mentioned halogen atom as a substituent.

[0036] Examples of the monomer (B) represented by the formula (2) include cyanoethyl acrylamide (CEAAM), N-(2-cyanoethyl)-N-methyl acrylamide, cyanomethyl acrylamide, etc. From the viewpoint of the balance between dielectric constant and flexibility, cyanoethyl acrylamide (CEAAM) is preferable. These monomers (B) may be used alone or in combination of two or more.

[0037] In addition, examples of the monomer (B) other than the monomer (B) represented by the formula (2) include N,N-bis(2-cyanoethyl)acrylamide, N,N-bis(2-cyanomethyl)acrylamide, etc.

[0038] <Other monomer (unit C)> In addition to the unit (A) and the unit (B), the polymer of the present embodiment may optionally have a unit (C) derived from a monomer (C) other than the monomer (A) and the monomer (B). Examples of the monomer (C) include alkyl (meth)acrylate monomers, alkyl (meth)acrylate monomers substituted with halogen atoms, hydroxyalkyl (meth)acrylate monomers, (meth)acryloyloxyalkyl isocyanate monomers, carboxyl group-containing monomers, aryl group-containing monomers, styrene-based monomers, fatty acid vinyl ester-based monomers, betaine monomers, etc. However, the present embodiment is not limited only to such examples. These monomers may be used alone or in combination of two or more.

[0039] Examples of the alkyl (meth)acrylate monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, sec-butyl (meth)acrylate, n-pentyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, methylpentyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like. Examples of the alkyl (meth)acrylate monomer substituted with the halogen atom include 2,2,2-trifluoroethyl acrylate and the like.

[0040] Examples of the hydroxyalkyl (meth)acrylate monomer include hydroxyethyl acrylate, 4-hydroxybutyl acrylate (4HBA), 1-acryloyloxy-3-hydroxyadamantane, 1,3-cyclohexanedimethanol monoacrylate, and the like.

[0041] Examples of the (meth)acryloxyalkyl isocyanate monomer include (meth)acryloxyethyl isocyanate, 2-methacryloxyethyl isocyanate ethylene glycol (MOI-EG), 1,1-(bisacryloyloxymethyl)ethyl isocyanate (BEI), and the like.

[0042] <Polymer> The content of unit (A) in the polymer of this embodiment is not particularly limited, but from the viewpoints of low Young's modulus, dielectric properties, and solubility in monomer (B), it is preferably 10 to 99 mol%, more preferably 30 to 95 mol%, and particularly preferably 60 to 70 mol% with respect to the total amount of the monomers of this embodiment. The content of unit (B) in the polymer of this embodiment is not particularly limited, but from the viewpoints of low Young's modulus and dielectric properties, it is preferably 1 to 90 mol%, more preferably 5 to 70 mol%, and particularly preferably 30 to 40 mol% with respect to the total amount of the monomers of this embodiment. For the purpose of imparting a crosslinked structure or the like, the polymer of this embodiment can be copolymerized with other units (unit (C1) described later), and further, other units (C2 described later) can be bonded to unit C1. In this case, the content of unit (C1) in the polymer is not particularly limited, but from the viewpoints of the resilience and low Young's modulus of the resulting elastomer, it is preferably 0.05 to 10 mol parts, more preferably 0.1 to 5 mol parts, and particularly preferably 0.25 to 2.5 mol parts with respect to 100 mol parts of the total amount of the monomers.

[0043] The weight average molecular weight (Mw) of the polymer of this embodiment is preferably from 200,000 to 4,000,000, more preferably from 500,000 to 3,800,000, and particularly preferably from 1,000,000 to 3,500,000 from the viewpoints of film-forming property and mechanical properties (low Young's modulus, low hysteresis loss). The weight average molecular weight of the polymer of this embodiment can be measured in terms of polystyrene using gel permeation chromatography [manufactured by Tosoh Corporation, product number: HLC-8320GPC, column: manufactured by Tosoh Corporation, product number: TSKgel GMHH-R, solvent: tetrahydrofuran, flow rate: 0.6 mL / min].

[0044] In this embodiment, the combination of each constitutional unit is not particularly limited, but from the viewpoint of achieving both high dielectric constant and flexibility in a high dimension, for example, the following combinations can be mentioned. (A) A combination of MTA (unit (A)) and CEAAM (unit (B)) (B) A combination of MTA (unit (A)), CEAAM (unit (B)), and 4HBA (unit (C)) (C) A combination of MTA (unit (A)), CEAAM (unit (B)), 4HBA (unit (C1)), and MOI-EG (unit (C2))

[0045] Examples of the polymer of this embodiment include polymers having a structure represented by the following formula (3).

[0046]

Chemical formula

[0047] 《Elastomer of the Present Embodiment》 As described above, the elastomer of the present embodiment is an elastomer (elastic body) containing the polymer of the present embodiment. When the polymer of the present embodiment itself functions as an elastic body, the polymer of the present embodiment itself can be referred to as the elastomer of the present embodiment. The shape such as the width, thickness, and length of the elastomer of the present embodiment is not particularly limited.

[0048] The Young's modulus of the elastomer of the present embodiment is preferably 1 MPa or less, more preferably 0.5 MPa or less, and particularly preferably 0.2 MPa or less. The elongation rate, Young's modulus, and hysteresis loss of the elastomer of the present embodiment can be measured, for example, according to the method described in the examples described later using a tensile measuring instrument. The elongation rate of the elastomer of the present embodiment is preferably 200% or more, more preferably 400% or more, and particularly preferably 700% or more. When the elastomer of the present embodiment is used for a sensor or the like where returnability is required, its hysteresis loss is preferably 10% or less, and more preferably 5% or less.

[0049] The dielectric constant of the elastomer of the present embodiment is not particularly limited. However, in the case of dielectric actuator applications, it is preferably 6 or more, more preferably 8 or more, and particularly preferably 10 or more. The dielectric constant of the elastomer of the embodiment can be measured by the method described in the examples described later.

[0050] The change rate when voltage is applied to the elastomer of this embodiment can be measured by the method described in the examples below. Although it is not particularly limited, in the case of dielectric actuator applications, the displacement amount when 1 kV is applied (displacement amount @1 kV (%)) is preferably 0.1% or more, more preferably 0.3% or more, and particularly preferably 0.5% or more. Similarly, the maximum change rate (%) of the displacement amount (Max displacement amount (%)) is preferably 2% or more, more preferably 5% or more, and particularly preferably 10% or more.

[0051] The breakdown voltage of the elastomer of this embodiment is preferably 10 (v / μm) or more, more preferably 20 (v / μm) or more, in the case of dielectric actuator applications.

[0052] The glass transition temperature of the elastomer of this embodiment is not particularly limited, but from the viewpoint of low Young's modulus, it is preferably 30°C or lower, more preferably 0°C or lower, and particularly preferably -20°C or lower. The measurement of the glass transition temperature can be carried out in accordance with JIS.K6240:2011.

[0053] 《Synthesis Methods of Polymers and Elastomers》 The production methods of the polymers and elastomers of this embodiment are not particularly limited. For example, they can be appropriately synthesized by known methods such as bulk polymerization method, solution polymerization method, emulsion polymerization method, suspension polymerization method, etc. However, this embodiment is not limited only to such examples. Among these polymerization methods, from the viewpoint of increasing molecular weight, the bulk polymerization method and the emulsion polymerization method are preferred, the bulk polymerization method is more preferred, and the photo-bulk polymerization method is even more preferred. When the elastomer of this embodiment is polymerized by the bulk polymerization method, it is not necessary to use a dispersant or a solvent during synthesis, so there is no need to remove the dispersant or the solvent from the system in which the polymer is synthesized, and the productivity is excellent.

[0054] As described above, the elastomer of the present embodiment can be produced by a method for producing an elastomer including, for example, a step of polymerizing a (meth)acrylate monomer having an ether structure (monomer (A)) and a (meth)acrylamide having a cyano group (monomer (B)) to obtain a polymer. Further, in the step of obtaining the above-mentioned polymer, the (meth)acrylate monomer having an ether structure (monomer (A)) and the (meth)acrylamide having a cyano group (monomer (B)) can be polymerized by bulk photopolymerization.

[0055] When synthesizing the polymer or elastomer of the present embodiment (hereinafter sometimes referred to as "the polymer etc. of the present embodiment") by a bulk photopolymerization reaction, specifically, monomer (A) and monomer (B) are polymerized using a polymerization initiator as necessary (for example, bulk polymerization by ultraviolet irradiation), and a polymer composed of structural units (A) and (B) can be synthesized.

[0056] The atmosphere when polymerizing the polymer etc. of the present embodiment is not particularly limited, and it may be air, or an inert gas such as nitrogen gas or argon gas.

[0057] The temperature when polymerizing the polymer etc. of the present embodiment is not particularly limited, and usually, it is preferably about 5 to 100 °C. The time required to polymerize the monomer component is arbitrary because it varies depending on the polymerization conditions and cannot be determined unconditionally, but usually, it is about 10 minutes to 20 hours.

[0058] The polymerization reaction can be arbitrarily terminated when the amount of the remaining monomer component reaches 20% by mass or less. The amount of the remaining monomer component can be measured, for example, using gel permeation chromatography. At this time, in addition to monomer (A) and monomer (B), a photopolymerization initiator described later etc. may be used. The conditions for the bulk polymerization of the polymer etc. of the present embodiment are not particularly limited, but from the viewpoint of obtaining those in the above-mentioned preferable molecular weight range and from the viewpoint of reducing hysteresis loss, the ultraviolet irradiance is 10 mW / cm 2The following is preferable, 1 mW / cm 2 The following is more preferable, 0.6 mW / cm 2 The following is even more preferable. Also, from the viewpoint of polymerizability, 0.01 mW / cm 2 or more is preferable.

[0059] In order to synthesize the polymer of the present embodiment by polymerizing the above monomer components, a polymerization initiator (photoinitiator, thermal polymerization initiator), a chain transfer agent, etc. may be used. For these, known ones can be appropriately selected and used.

[0060] <Photoinitiator> A photoinitiator is a compound that is activated by various actinic rays, such as ultraviolet rays, etc., and initiates a polymerization reaction. Examples of photoinitiators include radical photoinitiators, cationic photoinitiators, and anionic photoinitiators. These photoinitiators may be used alone or in combination of two or more. For example, two or more radical photoinitiators can be used in combination.

[0061] It is desirable to appropriately select a compound having absorption at the exposure light wavelength when photocuring the polymer of the present embodiment as the photoinitiator. For example, benzoin ether, benzoin α, α-dimethylbenzyl ketal, α, α-diethoxyacetophenone, 2-hydroxy-2-methyl-phenylacetone-1, 1-hydroxy-cyclohexylbenzophenone, 2-hydroxy-2-methyl-p-hydroxyethyl ether phenylacetone-1, [2-methyl 1-(4-carboxyphenyl)-2-morpholinone-1], [2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)butanone-1], benzoyl formate, 2,4,6-trimethylphenylacyl-ethoxy-phenylphosphine oxide, 2,4,6-trimethylphenylacyl diphenylphosphine oxide, bis(2,4,6-trimethylphenyl)phenylphosphine oxide, and 4-p-tolylhydrazyl benzophenone, etc. One or more radical photoinitiators selected from the group consisting of can be used.

[0062] Since the content of the photoinitiator in the polymer of this embodiment varies depending on the type of the photoinitiator and the like, it cannot be generally determined. However, usually, it is preferably about 0.01 to 20 parts by mass with respect to 100 parts by mass of the elastomer-forming composition.

[0063] (Surfactant) A surfactant may be used in the synthesis of the polymer or the like of this embodiment. When the polymer or the like of this embodiment contains a surfactant, a film or a membrane with less surface irregularities can be formed. The content of the surfactant in the polymer of this embodiment is not particularly limited. However, from the viewpoint of suppressing the generation of irregularities on the coating film surface during coating, 0.01 to 1% by mass is preferable, 0.05 to 0.5% by mass is more preferable, and 0.1 to 0.3% by mass is particularly preferable with respect to the total amount of the polymer of this embodiment.

[0064] Examples of the surfactant include dimethylsiloxane-based surfactants and fluorine-based surfactants, and dimethylsiloxane-based surfactants are preferable. Further, as the surfactant, a surfactant having a crosslinkable functional group such as acryloyl group-containing polyether-modified dimethylsiloxane is preferable. Examples of the crosslinkable functional group include (meth)acryloyl group and allyl group.

[0065] As the dimethylsiloxane-based surfactant, as commercially available products, for example, BYK-UV3500, BYK-UV3505, BYK-UV3510, BYK-UV3535, BYK-UV3570, BYK-UV3575, BYK-UV3576, etc. manufactured by BYK Additives & Instruments can be used, and among them, BYK-UV3500 is preferable.

[0066] In addition, the polymer of this embodiment can be used in combination with a chain transfer agent, a thermal initiator, a photosensitizer, etc. as desired within a range not impairing the effects of the present invention.

[0067] (Formation of crosslinked structure) In addition to units (A) and (B), the polymer and the like of the present embodiment can also be provided with a crosslinked structure by using a monomer (C1) having a substituent such as a hydroxyl group (for example, a hydroxyalkyl (meth)acrylate monomer such as 4HBA). In this case, if necessary, a polymer or the like obtained by polymerizing monomers (A) to (C1) is dissolved in a solvent to form a solution, and a monomer (C2) serving as a crosslinking agent (for example, a monomer having an isocyanate group) is further added to the solution (using a catalyst if necessary). As a result, the monomer (C2) serving as a crosslinking agent binds to the unit (C1) of the polymer, a polymer chain in which the monomers (C2) are polymerized is formed, hydrogen bonds are formed between the side chains of each polymer, or the main chain and side chains of each polymer are intertwined with each other, so that it is considered that a polymer or the like having a crosslinked structure can be obtained. As described above, by using a monomer (C1) having a substituent such as a hydroxyl group (for example, a hydroxyalkyl (meth)acrylate monomer such as 4HBA) and a monomer (C2) serving as a crosslinking agent (for example, a monomer having an isocyanate group), a crosslinked structure is imparted to the polymer and the like of the present embodiment, thereby improving the resilience of the polymer and the like and reducing the hysteresis loss. That is, those having such a crosslinked structure are also included in the polymer and the like of the present embodiment.

[0068] Depending on various purposes such as imparting a crosslinked structure to the polymer and the like of the present embodiment, the polymer and the like of the present embodiment can be dissolved in a solvent to form a resin solution. The solvent is not particularly limited, and for example, benzene-based solvents, ketone-based solvents, ester-based solvents, etc. can be used, and specifically, toluene, cyclopentanone, butyl acetate, carbitol acetate, etc. can be mentioned.

[0069] Further, when imparting a crosslinked structure to the polymer and the like of the present embodiment, a catalyst can be used together with the monomer (C2) functioning as a crosslinking agent. The catalyst is mainly added for the purpose of adding a monomer (C2) such as isocyanate used as a crosslinking agent to the hydroxyl group or the like of the unit (C1) in the polymer and the like of the present embodiment. The catalyst is not particularly limited, and for example, a tin catalyst or the like can be used.

[0070] As the monomer (C1), it can be appropriately selected from the above-mentioned monomers (C). For example, hydroxyalkyl (meth)acrylate monomers, carboxyl group-containing monomers, etc. can be used. As the monomer (C2) used as a crosslinking agent, it can be appropriately selected from the above-mentioned monomers (C). For example, (meth)acryloyloxyalkyl isocyanate monomers, etc. can be used. When imparting a crosslinked structure to the polymer and the like of the present embodiment using the monomer (C1) and the monomer (C2), from the viewpoint of the return property and the like of the polymer and the like, the content of the monomer (C2) is preferably 25 to 800 mol%, more preferably 50 to 400 mol%, and particularly preferably 100 to 200 mol% with respect to the total amount of the monomer (C1).

[0071] The reaction conditions in the reaction between the hydroxyl group and the like of the unit (C1) in the polymer and the like of the present embodiment and the isocyanate and the like of the unit (C2) in the polymer and the like of the present embodiment are not particularly limited. However, from the viewpoint of preventing the reaction between the monomers (C2) such as isocyanate used as a crosslinking agent, the heating temperature is preferably 40 to 100°C, more preferably 60 to 80°C; the heating time is preferably 0.5 to 12 hours, more preferably 1 to 6 hours. Also, when reacting (meth)acryloyl groups and the like of the unit (C) in the polymer and the like by light irradiation using a photoinitiator, the light irradiation conditions are not particularly limited, but ultraviolet rays and the like can be used. The ultraviolet illuminance is preferably 10 to 10,000 mW / cm 2 and more preferably 100 to 1,000 mW / cm 2 The ultraviolet integrated irradiation dose is preferably 100 mJ / cm 2 or more.

[0072] 《Usage form of elastomer》 The elastomer of this embodiment can be appropriately designed in terms of shape etc. according to the intended use. The elastomer of this embodiment can be used, for example, as a sheet-shaped elastomer or a laminate in which elastomers are laminated.

[0073] When the elastomer of this embodiment is made into a sheet shape, the sheet thickness is not particularly limited. For example, in the case of dielectric elastomer applications, it is preferably 10 μm to 300 μm. Further, when the elastomer of this embodiment is made into a laminate, for example, in the case of dielectric elastomer applications, it can be formed by laminating 100 to 300 sheet-shaped elastomers with a thickness of 10 μm to 50 μm.

[0074] The elastomer of this embodiment may contain an appropriate amount of other polymers according to desired purposes such as adjusting its viscosity. Examples of other polymers include acrylic resin, polyacrylonitrile, poly(meth)acrylamide, polyamide, polyvinyl chloride, polyurethane, polyester, carboxymethyl cellulose, etc., but this embodiment is not limited only to these examples. These other polymers may be used alone or in combination of two or more.

[0075] The elastomer of this embodiment may contain a neutralizing agent if necessary. Examples of neutralizing agents include inorganic basic compounds such as sodium hydroxide and potassium hydroxide; organic basic compounds such as monoethanolamine, dimethylethanolamine, diethylethanolamine, triethanolamine, morpholine, aminomethylpropanol, aminomethylpropanediol, octylamine, tributylamine, aniline, etc., but this embodiment is not limited only to such examples. These neutralizing agents may be used alone or in combination of two or more.

[0076] The elastomer of the present embodiment may contain additives as long as the object of the present embodiment is not inhibited. Examples of the additives include a colorant, an antioxidant, an ultraviolet absorber, an anti-aging agent, a thermal conductivity filler, a conductive filler, etc., but the present embodiment is not limited only to such examples.

[0077] 《Use of Elastomer》 When the elastomer of the present embodiment is in the form of a sheet, depending on the application, it can be used as it is, but from the viewpoint of imparting toughness, it is preferably uniaxially stretched or biaxially stretched, and more preferably biaxially stretched. From the viewpoint of imparting toughness, the stretching ratio of the sheet is preferably 1.2 times or more, more preferably 1.5 times or more, still more preferably 2 times or more, and although it also depends on the thickness of the film, from the viewpoint of preventing breakage during stretching, it is preferably 8 times or less, more preferably 6 times or less, still more preferably 5 times or less. When stretching the sheet, it may be heated if necessary.

[0078] The elastomer of the present embodiment can be used as a dielectric elastomer whose thickness and size are displaced according to the applied voltage. The dielectric elastomer of the present embodiment is expected to be used, for example, in electric devices such as actuators, sensors used in industrial robots, power generation elements, speakers, microphones, noise cancelers, transducers, artificial muscles, small pumps, and medical instruments. Among these, the elastomer of the present embodiment can be preferably used for actuators because it can be designed to show a large displacement amount even when the applied voltage is low.

[0079] Hereinafter, as an example of an electric device using the elastomer of the present embodiment, an actuator will be described. Note that the present invention is not limited only to the embodiments shown in the following description.

[0080] FIG. 1 is a schematic plan view showing an embodiment of the actuator of the present invention. FIG. 2 is a schematic cross-sectional view taken along line A-A of the actuator shown in FIG. 1. FIG. 3 is a schematic diagram for explaining the displacement of the elastomer.

[0081] As shown in FIGS. 1 and 2, the actuator 1 is formed of a film-shaped elastomer 2 and a pair of electrodes 3A and 3B. The elastomer 2 and the electrodes 3A and 3B can be adhered, for example, with a conductive paste (not shown). Examples of the conductive paste include a conductive paste containing a conductive filler such as carbon or silver.

[0082] The elastomer 2 is preferably uniaxially or biaxially stretched, preferably biaxially stretched. The stretching ratio of the elastomer 2 is not particularly limited, but from the viewpoint of imparting toughness, it is preferably 1.2 times or more, more preferably 1.5 times or more, still more preferably 2 times or more. Also, although it depends on the thickness of the elastomer, from the viewpoint of preventing breakage during stretching, it is preferably 8 times or less, more preferably 6 times or less, still more preferably 5 times or less.

[0083] The thickness of the elastomer 2 is preferably 1 to 100 μm, more preferably 1 to 80 μm, still more preferably 1 to 50 μm, and even more preferably 1 to 30 μm from the viewpoint of enabling the actuator 1 to exhibit a large displacement amount even when the applied voltage is low.

[0084] As shown in FIG. 2, the electrodes 3A and 3B are arranged so as to face both sides of the elastomer 2, respectively. Each electrode is formed of an electrode material. Examples of the electrode material include metals and metal oxides such as indium tin oxide (ITO), antimony tin oxide (ATO), fluorine-doped tin oxide (FTO), tin fluoride oxide (FTO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), tin oxide (NESA), indium zinc oxide (IZO), silver oxide, vanadium oxide, molybdenum oxide, gold, silver, platinum, copper, indium, chromium, etc., silicon-based materials such as polycrystalline silicon and amorphous silicon, and carbon materials such as carbon black, graphite, and glassy carbon. However, the present invention is not limited to such examples only. These electrode materials may be used alone or in combination of two or more.

[0085] The shapes, sizes, and thicknesses of the electrodes 3A and 3B are not particularly limited and can be arbitrarily determined according to the use of the actuator 1. Examples of the shapes of the electrodes 3A and 3B include circular, elliptical, triangular, square, rectangular, etc. As an example of the size of the electrodes 3A and 3B, a circular one with a diameter of 1 to 20 mm can be mentioned. The thickness of the electrodes 3A and 3B is not particularly limited, but is usually about 50 to 500 μm.

[0086] A terminal 4A is disposed on the outer peripheral surface in the diameter direction of the electrode 3A, and a terminal 4B is disposed on the outer peripheral surface in the diameter direction of the electrode 3B. The terminals 4A and 4B are connected to the power source 6 via the conducting wires 5A and 5, respectively.

[0087] When a voltage is applied to the electrodes 3A and 3B by the power source 6, an electrostatic attraction force is generated between the electrodes. As shown in FIG. 3, the elastomer 2 is compressed in the direction indicated by the thick arrow in FIG. 3. Therefore, the thickness (W in FIG. 2) of the elastomer 2 becomes smaller, and the elastomer 2 is stretched in the width direction (the direction indicated by the thin arrow in FIG. 3). At this time, the electrodes 3A and 3B are stretched in the width direction together with the elastomer 2.

[0088] By attaching the marker 7 to the electrode 3A, the displacement amount of the actuator 1 when a voltage is applied to the electrodes 3A and 3B can be measured with the displacement meter 8.

Example

[0089] Hereinafter, the present invention will be specifically described using examples. However, the present invention is not limited to the following examples.

[0090] [Example 1] (Synthesis of elastomer) 21.0 g of methoxyethyl acrylate (MTA; monomer (A)), 223 g of cyanoethyl acrylamide (CEAAM; monomer (B)), and 0.118 g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide [manufactured by BASF, trade name: Irgacure TPO] as a polymerization initiator were mixed to obtain a monomer component containing a polymerization initiator.

[0091]

Chemical formula

[0092] The obtained monomer component was filled in a molding container made of SUS (vertical: 43 cm, horizontal: 43 cm, depth: 2 mm), covered with transparent glass (vertical: 43 cm, horizontal: 43 cm, thickness: 2 mm) from above, and then the monomer component was irradiated with ultraviolet rays from above so that the illuminance became 0.58 mW / cm 2 and bulk polymerized for 2 hours to obtain a sheet-like elastomer containing the following MTA-CEAAM structure.

[0093]

Chemical formula

[0094] [Examples 2 to 4, Comparative Examples 1 to 5] In Example 1, each elastomer (sheet) was produced in the same manner as in Example 1, except that monomer (A) and monomer (B) and their usage amounts were changed according to the following table. In addition, BA (butyl acrylate) and CNEA (cyanoethyl acrylate) in the following table are shown below.

[0095] [Chemical formula]

[0096] [Evaluation] According to the method shown below, each physical property of the sheets of the examples and comparative examples was measured. The results are shown in the following table.

[0097] [Weight-average molecular weight] Using gel permeation chromatography [manufactured by Tosoh Corporation, product number: HLC-8320GPC, column: manufactured by Tosoh Corporation, product number: TSKgel GMHH-R, solvent: tetrahydrofuran, flow rate: 0.6 mL / min], the weight-average molecular weight (Mw) of each elastomer sheet was measured in terms of polystyrene.

[0098] [Film thickness] For each elastomer sheet, the sheet thickness was measured using a thickness gauge (manufactured by Nikon Corporation, product name DIGIMICRO MFC-101A). The measurement was performed 5 times at arbitrary sites, and the average value was taken as the thickness of the sheet.

[0099] [Glass transition temperature (Tg) of the elastomer] The measurement of the glass transition temperature of the elastomer in this embodiment was carried out in accordance with JIS K6240:2011.

[0100] [Measurement of Young's modulus] Test pieces were obtained by punching out each elastomer sheet into a dumbbell-shaped No. 7 form specified in 6.1 of JIS K6251. The obtained test pieces were attached so that the chuck distance of a tensile testing machine (manufactured by A&D Company, Limited, product number: Tensilon RTG-1310) was 19 mm, and an operation of applying a tensile load at a tensile speed of 100 mm / min until the test pieces broke was performed to measure the Young's modulus. The elongation of the film obtained above was determined based on the formula: [Elongation of film (%)] = [(Length of test piece at break (mm) - Original length of test piece (mm)) ÷ (Original length of test piece (mm))] × 100. The data storage interval was recorded at 0.1 second.

[0101] [Measurement of dielectric constant] The dielectric constant of each elastomer sheet was measured with an impedance analyzer (manufactured by Ametek, product number: 1260A).

[0102] [Measurement of actuator evaluation (change rate (%) of film)] [Measurement of displacement amount @ 1 kV (%)] By applying carbon black to the central portions of both sides of each elastomer sheet, electrodes (diameter: 2.5 mm, thickness: 5 μm) were formed to fabricate an actuator. A voltage was applied to the electrodes of the obtained actuator, and the displacement amount and the change rate of the actuator when the voltage was increased were calculated according to the following method.

[0103] First, a displacement amount measurement marker was attached to one of the electrodes of the actuator, and a DC voltage (1000 V) was applied between the electrodes with a voltage amplifier (manufactured by Matsueda Precision Co., Ltd., product number: HEOPS-10B2). At this time, the displacement amount (mm) of the marker was measured with a displacement meter (manufactured by Keyence Corporation, product number: LK-GD500).

[0104] Thereafter, the change rate of the displacement amount (displacement amount @ 1 kV (%)) was determined based on the following formula. [Change rate of displacement amount (%)] = [(Displacement amount (mm) ÷ Radius of electrode before voltage application (mm))] × 100

[0105] (Measurement of MAX displacement amount (%)) The DC voltage applied between the electrodes was varied, and the maximum change rate (%) of the displacement amount and the applied voltage at that time were measured.

[0106] [Example 5] (Synthesis of elastomer) 220 g of methoxyethyl acrylate (MTA; monomer (A)), 21.2 g of cyanoethyl acrylamide (CEAAM; monomer (B)), 5.48 g of 4-hydroxybutyl acrylate (4HBA), and 0.412 g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide [manufactured by BASF, trade name: Irgacure TPO] as a polymerization initiator were mixed to obtain a monomer component containing a polymerization initiator.

[0107] [Chemical formula]

[0108] The obtained monomer component was bulk polymerized for 2 hours in the same manner as in Example 1 except that ultraviolet rays were irradiated from above so that the illuminance became 0.62 mW / cm 2 to obtain an elastomer. 112 g of the obtained elastomer was dissolved in 1011 g of butyl acetate to obtain a resin solution.

[0109] 6.88 g of MOIEG (2-methacryloyloxyethyl isocyanate ethylene glycol) and 0.22 g of a tin catalyst [manufactured by Nitto Kasei Co., Ltd., product name: Neostan U-100] were added to the obtained resin solution, and this was stirred well at a temperature of 80 °C for 2 hours to obtain a resin solution containing an MTA-CEAAM-4HBA-MOIEG structure.

[0110] [Chemical formula]

[0111] To 1130 g of the obtained resin solution (11% by mass solution) (containing 119 g of MTA-CEAAM-4HBA-MOIEG), 1.19 g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide [manufactured by BASF, trade name: Irgacure TPO] as a polymerization initiator and 1.13 g of a surfactant (manufactured by BYK Additives & Instruments, trade name: BYK-UV3500) were added and stirred to prepare a curable resin composition.

[0112] (Formation of sheet-like elastomer) Two release films (manufactured by Panac Co., Ltd., trade name: SP-PET 100-O1-BU) were prepared. The curable resin composition obtained above was applied onto one of the release films to form a coating film. Thereafter, the coating film was heated at a temperature of 120 °C for 30 minutes to remove the solvent and obtain a film-like coating film.

[0113] The other release film was attached onto the obtained coating film, and pressing treatment was performed using a heated laminator (manufactured by FUJIPLA, used at 90 °C). The obtained film-like coating film was cured in an air atmosphere with an ultraviolet irradiance of 500 mW / cm 2 × for 2.4 seconds × 1 pass (integrated irradiation dose: 1200 mJ / cm 2 ) to produce an elastomer (sheet) sandwiched between the front-side film and the back-side film, and the same evaluation as in Example 1 was performed.

[0114] [Measurement of hysteresis loss] Regarding the resilience of the elastomer sheets obtained in Examples 1 and 5, the hysteresis loss serving as the evaluation index was derived. Specifically, using the above test pieces and a tensile testing machine, the following measurements were performed, and the hysteresis loss was calculated using the obtained graph. The measurement was performed by applying a tensile load to the test piece up to 100% elongation (operation of setting the distance between chucks to 38 mm) and returning the test piece that had reached 100% to 0% (operation of returning the distance between chucks of 38 mm to 19 mm) (both at 100 mm / min) as one cycle, and performing two cycles. The hysteresis loss was calculated from the graph of the measurement results of the second cycle. The data was recorded at a storage interval of 0.1 seconds.

[0115] The method for calculating the hysteresis loss will be described in detail with reference to Fig. 4. Fig. 4 is a graph for explaining the hysteresis loss. The horizontal axis represents the film elongation, and the vertical axis represents the normalized stress. The normalized stress is the value obtained by dividing the observed value of the stress at each time by the observed value of the stress when the film elongation is 100%. The hysteresis loss was calculated as the area of the region enclosed by the dotted line (forward path) and the solid line (return path) in Fig. 4. The smaller the hysteresis loss, the better the followability. The area was calculated as follows. First, the stress at strain 1 (film elongation of 100%) was taken as σ A , and the normalized stress Z t at time t was obtained based on the following equation (1). Equation (1): [Normalized stress Z t at time t] = [Stress σ t (MPa) at time t] ÷ [Stress σ A (MPa) at strain 1] Also, let the film elongation at a certain time t be ε t . When changing from a certain time t - 1 to the next time (0.1 seconds later) t, the area enclosed by the SS curve, the straight line Z = 0, the straight line ε = ε t-1 , and the straight line ε = ε t was approximated as the area of a trapezoid and obtained by the following equation (2). Equation (2): [Area S t of the trapezoid when changing from time t - 1 to t] = (Z t-1 + Z t ) × (ε t - ε t-1 ) ÷ 2 Finally, the S t obtained from the start to the end of the second cycleThe sum was obtained and regarded as the hysteresis loss.

[0116]

Table 1

[0117]

Table 2

[0118] As can be seen from the results in the table, all of the elastomers in the examples had a Young's modulus comparable to or higher than that of the elastomers in the comparative examples, while having a high dielectric constant and a large displacement amount when a voltage was applied. Specifically, from the comparison between Example 1 and Comparative Example 1, it was found that when cyanoethyl acrylamide (CEAAM; monomer (B)) was copolymerized with methoxyethyl acrylate (MTA; monomer (A)), the dielectric constant increased and the displacement amount became larger compared to the case where only MTA was used. Therefore, it was found that by adding highly polar CEAAM, the dielectric constant of the elastomer can be improved and the displacement amount can be further increased. Also, from the comparison between Example 1 and Comparative Example 2, a combination of MTA / CEAAM using more highly polar CEAAM (Example 1) resulted in a high dielectric constant and high displacement elastomer compared to the case of using cyanoethyl acrylate (CNEA; acrylic having a cyano group). Therefore, it was found that copolymerizing acrylamide having a cyano group with MTA rather than acrylic having a cyano group results in higher dielectric constant and higher displacement. From the comparison between Example 1 and Comparative Example 5, Example 1 in which MTA, which is as flexible as BA and highly polar, was copolymerized rather than Comparative Example 5 in which highly polar CEAAM and butyl acrylate (BA) were copolymerized had a larger dielectric constant and displacement amount. Therefore, it was found that by copolymerizing highly polar CEAAM with soft and relatively highly polar MTA, the dielectric constant and the displacement amount can be increased.

[0119] From the comparison between Examples 3 and 4 and Comparative Example 4, Examples 3 (MTA / CEAAM (molar ratio) = 70 / 30) and 4 (MTA / CEAAM (molar ratio) = 60 / 40) had a larger displacement of the elastomer compared to Comparative Example 4 using the copolymer (BA / CNEA (molar ratio) = 30 / 70) disclosed in the examples of JP-A-2018-59042. Also, from the comparison between Examples 1 to 4, in the combination of MTA / CEAAM, the higher the ratio of CEAAM to MTA, the higher the dielectric constant and displacement of the obtained elastomer. Furthermore, from the comparison between Example 1 and Example 5, the elastomer (Example 5) in which 4HBA of the crosslinking group was introduced to improve the return property, MOI-EG was added to the hydroxy group, and then a crosslinked structure was imparted by a photocrosslinking reaction could reduce the hysteresis loss compared to Example 1.

Industrial Applicability

[0120] The elastomer of the present invention is not particularly limited, but is useful as a dielectric elastomer, and is expected to be used, for example, in actuators, sensors used in industrial robots, power generation elements, speakers, microphones, noise cancelers, transducers, artificial muscles, small pumps, medical instruments, etc.

[0121] The disclosure of Japanese Patent Application No. 2021-186160 filed on November 16, 2021 is incorporated herein by reference in its entirety. Also, all documents, patent applications, and technical standards described in the specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference.

Explanation of Reference Signs

[0122] 1: Actuator, 2: Elastomer, 3A, 3B: Electrodes, 4A, 4B: Terminals, 5A, 5B: Conductive wires, 6: Power source, 7: Marker, 8: Displacement meter

Claims

1. A unit (A) derived from a (meth)acrylate monomer having an ether structure represented by the following formula (1), a unit (B) derived from a (meth)acrylamide having a cyano group, and a polymer containing the same. 【Chemical Formula 1】 (In the formula, R1 represents a hydrogen atom or a methyl group. R2 represents an alkyl group having 1 to 5 carbon atoms which may have a halogen atom. X1 represents an alkylene group having 1 to 10 carbon atoms which may have a halogen atom. n represents an integer of 1 to 3.)

2. A unit (A) derived from a (meth)acrylate monomer having an ether structure, and a unit (B) derived from a (meth)acrylamide having a cyano group represented by the following formula (2), and a polymer containing the same. [Chemical Formula 2] (In the formula, R 1 represents a hydrogen atom or a methyl group. R 3 represents a hydrogen atom or a methyl group. X 2 represents an alkylene group having 1 to 10 carbon atoms which may have a halogen atom.)

3. The polymer according to Claim 1, having a weight average molecular weight of 200,000 to 4,000,000.

4. An elastomer containing the polymer according to any one of Claims 1 to 3.

5. A method for producing the elastomer according to Claim 4, comprising: a step of polymerizing a (meth)acrylate monomer having an ether structure and a (meth)acrylamide having a cyano group to obtain a polymer. A method for producing an elastomer containing the same.

6. The method for producing an elastomer according to Claim 5, wherein the (meth)acrylate monomer having an ether structure and the (meth)acrylamide having a cyano group are polymerized by bulk photopolymerization.

7. An actuator comprising the elastomer according to Claim 4.

8. A sensor comprising the elastomer according to Claim 4.

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