JP4946570B2 - Polymer actuator - Google Patents

Description

  The present invention relates to a polymer actuator.

  An actuator using a polymer material such as a conductive polymer generally has a configuration having a pair of electrode layers and an ion-conducting electrolyte interposed therebetween. Polymer actuators have advantages such as low drive voltage and high energy density, and are being studied with the expectation of application to artificial muscles and the like.

In the case of a polymer actuator, conventionally, a liquid or gel electrolyte is often used (for example, Patent Documents 1 and 2). However, the liquid or gel electrolyte in the conventional polymer actuator does not have sufficient strength as a self-supporting layer itself, and the polymer actuator operates stably in the atmosphere as a self-supporting element. It is difficult to operate while generating a large stress. Moreover, when the strength of the electrolyte is low, the electrolyte is easily damaged when the polymer actuator is repeatedly operated with a large displacement, and the durability is insufficient. Therefore, a polymer actuator using a solid electrolyte has also been studied (Patent Documents 3 and 4).
JP 2006-507080 A JP 2006-288040 A JP 2004-98199 A JP 2006-120596 A

  Conventionally, however, polymer actuators using a solid electrolyte layer have relatively good durability, but their electrical conductivity is not necessarily high, and further improvements have been demanded in this respect. If the electrical conductivity is low, there are many disadvantages in practice, such as requiring a larger voltage and not sufficiently increasing the operating speed as an actuator.

  Therefore, an object of the present invention is to provide a polymer actuator having a sufficiently high conductivity while using an electrolyte layer that can stand alone and has a strength that allows repeated stable operation.

  The polymer actuator according to the present invention includes an electrolyte layer and an electrode layer provided adjacent to the electrolyte layer. The electrolyte layer is a cross-linked structure formed by polymerization of a polymerizable composition containing a polyfunctional polymerizable compound having three or more polymerizable functional groups, and includes a group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom. It contains a crosslinked structure having a repeating unit containing at least one selected atom and an ionic substance.

  In the polymer actuator according to the present invention, the network-like cross-linked structure derived from the polyfunctional polymerizable compound having three or more polymerizable functional groups can be independently independent and can operate stably and repeatedly. A certain degree of strength is imparted to the electrolyte layer. Furthermore, since the repeating unit in the crosslinked structure contains an oxygen atom or the like, high ionic conductivity for efficiently conducting ions of the ionic substance is ensured. That is, the polymer actuator according to the present invention can achieve a sufficiently high conductivity while using an electrolyte layer that can stand alone and has a strength that allows repeated and stable operation.

  The polyfunctional polymerizable compound is preferably a prepolymer having a repeating unit containing at least one atom selected from the group consisting of an oxygen atom, a sulfur atom and a nitrogen atom. Thereby, the ionic conductivity of the electrolyte layer is further enhanced. In addition, the resistance of the polymer actuator to repeated operations is enhanced, and it becomes possible to operate stably for a longer period of time. From the same viewpoint, the prepolymer preferably has a star-shaped branched structure.

  The ionic substance is preferably an ionic liquid. Thereby, the displacement amount as the actuator can be further increased.

  According to the present invention, it is possible to provide a polymer actuator having a sufficiently high conductivity while using an electrolyte layer that can stand alone and has a strength that allows repeated and stable operation. Since the conductivity is high, a polymer actuator more excellent in terms of operating speed, driving voltage, etc. can be obtained. Further, since the actuator itself has a good strength, a relatively large stress can be generated during energization. The ability to generate large stress continuously is a great merit in practical use.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view showing an embodiment of a polymer actuator. The polymer actuator 1 shown in FIG. 1 includes a pair of opposed electrode layers 11 and 12 and an electrolyte layer 20 sandwiched between the pair of electrode layers 11 and 12. Connection terminals 31 and 32 are respectively attached to the outer sides of the electrode layers 11 and 12, and these are connected to a circuit including a variable voltage power source. In the polymer actuator 1, ion conduction is caused by energization and deviation occurs in the distribution of ions in the electrolyte layer 20, thereby causing displacement.

  The electrolyte layer 20 is a solid containing a network-like crosslinked structure formed by polymerization of a polymerizable composition containing a polyfunctional polymerizable compound having three or more polymerizable functional groups, and an ionic substance. It is a gel-like layer. The crosslinked structure in the electrolyte layer 20 has a molecular chain composed of a repeating unit including at least one kind of atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom.

The repeating unit having at least one atom selected from the group consisting of an oxygen atom, a sulfur atom and a nitrogen atom is a group coordinated to an ion (for example, Li ⁺ ) such as a metal ion constituting the ionic substance. preferable. Specific examples of such a repeating unit include those represented by the following chemical formula (10), (11), (12), (13), (20) or (30). Among these, an oxyalkylene group represented by the formula (10) is particularly preferable.

Formulas (10) to (13) are oxygen atoms, (20) is a sulfur atom, and (30) is a repeating unit containing a nitrogen atom. R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ represent a divalent organic group. R ^{1 to} R ⁶ are preferably an alkylene group, more preferably an alkylene group having 1 to 6 carbon atoms. Specific examples of R ^{1 to} R ⁶ include an ethylene group and a propylene group. R ⁷ represents a hydrogen atom or an alkyl group. The alkyl group for R ⁷ preferably has 1 to 3 carbon atoms, and specifically, is preferably a methyl group or a propyl group.

  The crosslinked structure may have other groups having an ionic conductivity in addition to the repeating unit as described above. For example, an anion-trapping group such as a sulfonic acid group and a sulfonic acid amide group or an art-type complex containing boron or aluminum may be introduced into the crosslinked structure. Further, the molecular chain in the crosslinked structure may further have another linear structure such as a polysiloxane chain in addition to the portion composed of the repeating unit represented by the above chemical formula.

  The crosslinked structure can be formed by a polymerization reaction of a polymerizable composition containing a polyfunctional polymerizable compound having three or more polymerizable functional groups. The polymerizable composition is polymerized by heat or light to form a network-like crosslinked structure.

  The polymerizable functional group of the polyfunctional polymerizable compound is a functional group that is cross-linked by a polymerization reaction such as radical polymerization or cationic polymerization. Specific examples of the polymerizable functional group include an acrylate group, a methacrylate group, an epoxy group, an isocyanate group, an oxetane group, and a vinyl ether group. Among these, an acrylate group and a methacrylate group are preferable.

  The polyfunctional polymerizable compound is preferably a prepolymer having a repeating unit containing at least one atom selected from the group consisting of an oxygen atom, a sulfur atom and a nitrogen atom. Thereby, a crosslinked structure in which a repeating unit containing an oxygen atom or the like is introduced can be easily formed.

  The prepolymer preferably has a polymerizable functional group at the terminal. As a result, the crystallinity of the cross-linked structure is lowered, and better ion conductivity and flexibility are obtained.

  The prepolymer may be linear or may have a branched structure. In particular, the prepolymer preferably has a star-shaped branched structure. The star-shaped branched structure is a structure in which three or more linear molecular chains extend from one branch point, and a polymer compound generally called a star-shaped polymer has this star-shaped branched structure. The molecular chain extending from the branch point may be further branched. In other words, in the present invention, the star-shaped branch structure includes a highly branched structure called a so-called hyper branch. The polymerizable functional group is preferably bonded to the end of the star-shaped branched structure.

  FIG. 2 is a schematic view showing an embodiment of a prepolymer having a star-shaped branched structure. The prepolymer of FIG. 2 has one branch point, four linear molecular chains extending from the branch point, and an acrylate group bonded to the end of each molecular chain. Each molecular chain has, for example, a polyoxyalkylene chain.

  A prepolymer having a star-shaped branched structure can be obtained, for example, by a method of introducing a polymerizable functional group into a terminal of a known star-shaped polymer. In addition, a prepolymer having a star-shaped branched structure is commercially available, for example, “TA210” (Daiichi Kogyo Seiyaku Co., Ltd.).

  The branched structure of the prepolymer is not limited to a star shape. For example, the prepolymer may have a comb-shaped branched structure in which side chains of a certain length are regularly bonded to a linear main chain. In this case, the side chain may be further branched.

  The molecular weight of the prepolymer is preferably 300 or more from the viewpoint of good ion conductivity and moderate flexibility of the electrolyte layer. Moreover, it is preferable that the molecular weight of a prepolymer is 50000 or less.

  The polymerizable composition may further contain a monofunctional or bifunctional monomer and / or prepolymer if necessary. When the polymerizable functional group is a radical polymerizable functional group, the polymerizable composition preferably contains an initiator such as a photopolymerization initiator or a thermal radical polymerization initiator.

  The electrolyte layer 20 contains an ionic substance composed of a cation and an anion. The ionic substance is preferably an ionic liquid. Preferable specific examples of the ionic liquid include imidazolium salts, pyridium salts, and quaternary ammonium salts.

  The ratio of the ionic substance in the electrolyte layer 20 is preferably 10 to 400% by mass based on the mass of the crosslinked structure in the electrolyte layer 20. If this proportion is less than 10% by mass, the conductivity of the electrolyte layer 20 tends to decrease, and if it exceeds 400% by mass, the strength of the electrolyte layer decreases or when an ionic liquid is used, the ionic liquid Tend to ooze out easily.

  The electrolyte layer 20 may contain other components as necessary in addition to the above components. For example, the electrolyte layer 20 may contain an ion conductive polymer compound separately from the crosslinked structure. The ion conductive polymer compound preferably has, for example, a repeating unit represented by the above chemical formulas (10) to (13), (20), or (30).

  At least one of the pair of electrode layers 11 and 12 is a conductive polymer layer containing a conductive polymer as a main component, or a conductive material containing a conductive filler such as carbon nanofiber and an insulating polymer material. It is preferable that it is a layer of nature.

  Suitable conductive polymers include polythiophene, polypyrrole and polyaniline. The conductive polymer is preferably doped with a dopant. In the case of this embodiment, polythiophene or polypyrrole doped with poly (styrenesulfonic acid) is particularly preferable. A specific example of a suitable polythiophene is poly (3,4-ethylenedioxythiophene).

  The electrode layers 11 and 12 may contain other components such as a silane coupling agent for improving the adhesion with the electrolyte layer 20 as necessary. Further, the electrode layers 11 and 12 may be metal layers made of metal. Examples of the metal used for the electrode layers 11 and 12 include gold, silver, copper, and nickel. The metal layer may be formed on the electrolyte layer by sputtering or plating, for example, or a separately prepared metal layer may be bonded with an adhesive.

  The polymer actuator 1 includes, for example, a step of forming an electrode layer 11 on a substrate, a polymerizable composition containing a polyfunctional polymerizable compound and, if necessary, an initiator on the electrode layer 11, and an ionic substance. A step of applying an electrolyte composition containing, and a crosslinked structure is formed by polymerizing the polymerizable composition in the applied electrolyte composition to form the crosslinked structure and the ionic substance. It can be obtained by a method comprising a step of forming the electrolyte layer 20 to be contained, a step of forming the electrode layer 12 on the electrolyte layer 20, and a step of peeling the substrate. The polyfunctional polymerizable compound has three or more polymerizable functional groups and a repeating unit containing at least one atom selected from the group consisting of an oxygen atom, a sulfur atom and a nitrogen atom. Usually, a product of a predetermined size is cut out from the sheet of the laminated body after peeling by means such as punching or cutting.

  The electrode layers 11 and 12 are made of, for example, a conductive paste containing a conductive polymer, a solvent in which the conductive polymer is dispersed or dissolved, and, if necessary, other components such as a silane coupling agent as a substrate or It can apply | coat on the electrolyte layer 20 and can be formed by the method of removing a solvent from the apply | coated electrically conductive paste.

  The electrolyte composition for forming the electrolyte layer 20 is prepared, for example, by mixing a polyfunctional polymerizable compound, an ionic substance, and the like, and uniformly dispersing each component by means such as a homogenizer. The electrolyte composition is often a paste. The method for applying the electrolyte composition is not particularly limited, and for example, methods such as an applicator, a bar coater, a knife coater, and screen printing can be appropriately employed.

  The polymerization of the polymerizable composition after coating can be advanced by heating or light irradiation, preferably light irradiation. When the ionic substance is an ionic liquid, it is usually unnecessary to use a solvent such as water, so that a drying step is unnecessary, and the electrolyte layer can be formed with high efficiency.

  The present invention is not limited to the embodiment described above, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the polymer actuator, only one electrode layer may be provided, or a plurality of electrode layers and electrolyte layers may be alternately stacked. The electrode layer is not necessarily provided in direct contact with the electrolyte layer, and the electrode layer may be provided on at least one surface side of the electrolyte layer, and another layer may be provided between the electrolyte layer and the electrode layer. Good. Further, the shape is not limited to a flat plate shape, and can be changed as appropriate depending on the application.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Example 1
Preparation of electrolyte paste The following raw materials were mixed and dispersed using a homogenizer at 10,000 rpm for 10 minutes, and then defoamed to obtain an electrolyte paste.
・ Polyfunctional terminal acrylate polymer having polyoxyalkylene chain (TA210)
: 100 parts by weight-ionic liquid (1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide)
: 34.4 parts by weight-photopolymerization initiator (2,2-dimethoxy-1,2-diphenylethane-1-one, IRG651)
: 1 part by weight

Preparation of conductive polymer paste The following raw materials were mixed and dispersed using a homogenizer to obtain a conductive polymer paste.
-Aqueous dispersion of poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid) (solid content: 1.2% by mass, manufactured by Starck, Baytron P HC V4)
: 100 parts by weight N-methylpyrrolidone: 5 parts by weight γ-glycidyltrimethoxysilane (SH6040, manufactured by Toray Dow Corning)
: 1 part by weight

Actuator preparation and evaluation The conductive polymer paste is spread on a glass substrate using an applicator, dried and crosslinked by heating at 80 ° C. for 30 minutes, and a conductive polymer layer (film thickness: about 5 μm) is formed. Formed. The conductivity of the formed conductive polymer layer was 5 S / cm. Next, the above electrolyte paste was applied on the conductive polymer layer by the same method, and then cured by UV irradiation (integrated light amount 6000 mJ / cm ² ) to form an electrolyte layer. When the ionic conductivity of the formed electrolyte layer was measured by an alternating current impedance method, it was as good as 1.7 × 10 ⁻⁴ S / cm. Further, a conductive polymer layer was formed on the electrolyte layer in the same procedure as the first conductive polymer layer. The obtained three-layer laminate was peeled from the glass substrate to obtain a polymer actuator sheet (thickness: 420 μm). A sample for evaluation having a predetermined size was cut out from the obtained sheet.

  The evaluation sample was clamped with a Kelvin clip, a square wave (± 3 V) voltage was applied by a function generator, and the current value, voltage and displacement at that time were measured simultaneously to evaluate the operating characteristics of the actuator. 2 and 3 are graphs showing the relationship between applied voltage and displacement and measurement time. FIG. 2 shows the results when a voltage is applied to the actuator at a frequency of 200 mHz and FIG. 3 shows a frequency of 1 Hz. In both cases, sufficiently stable operation was maintained for a long time. In addition, the electrolyte layer itself was strong enough to be easily handled and no change was observed in its shape and appearance even after the operation test.

(Comparative Example 1)
Preparation of electrolyte paste The following raw materials were mixed and dispersed using a homogenizer at 10,000 rpm for 10 minutes, and then defoamed to obtain an electrolyte paste.
・ Linear polyethylene glycol diacrylate (molecular weight 600)
: 40 parts by weight / linear polyethylene glycol monoacrylate (molecular weight 600)
: 60 parts by weight ionic liquid (1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide)
: 40 parts by weight of photopolymerization initiator (2,2-dimethoxy-1,2-diphenylethane-1-one, IRG651)
: 1 part by weight

Preparation and Evaluation of Actuator A sample for evaluation of a polymer actuator was prepared in the same manner as in Example 1 except that an electrolyte layer was formed using the above electrolyte paste, and its operating characteristics were evaluated. The ionic conductivity of the formed electrolyte layer was 1.4 × 10 ⁻⁴ S / cm, which was inferior to that of the electrolyte layer of Example 1. FIG. 4 is a graph showing the relationship between applied voltage and displacement and measurement time when a 100 mHz square wave is applied. The displacement decreased sharply in a short time after the start of operation and did not operate normally. The electrolyte layer was weak and weak in gel form, and cracks and peeling from the conductive polymer layer were observed in the electrolyte layer after the test. A large amount of ionic liquid oozes out from the electrolyte layer, which causes a decrease in adhesion to the conductive polymer layer and a decrease in film strength.

(Example 2)
An electrolyte paste was obtained in the same manner as in Example 1 except that the composition was changed to the following. An electrolyte layer was formed in the same manner as in Example 1 using the obtained electrolyte paste. It was 1.8 * 10 < ^-3 > S / cm when the ionic conductivity of the formed electrolyte layer was measured by the alternating current impedance method.
・ Polyfunctional terminal acrylate polymer having polyoxyalkylene chain (TA210)
: 100 parts by weight-ionic liquid (1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide)
: 100 parts by weight-photopolymerization initiator (2,2-dimethoxy-1,2-diphenylethane-1-one, IRG651)
: 1 part by weight

(Comparative Example 2)
An electrolyte paste was obtained in the same manner as in Example 1 except that the composition was changed to the following. The obtained electrolyte paste was applied onto the conductive polymer layer and cured by heating at 130 ° C. for 3 hours to form an electrolyte layer. When the ionic conductivity of the formed electrolyte layer was measured by an alternating current impedance method, it was 5.3 × 10 ⁻⁵ S / cm, and the ionic conductivity was compared with Example 2 using a prepolymer having an oxyalkylene chain. The degree dropped significantly.
・ Bisphenol F type epoxy resin (manufactured by JER Co., Ltd., 8170C)
: 100 parts by weight-ionic liquid (1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide)
: 100 parts by weight / acid anhydride curing agent (manufactured by Dainippon Ink & Chemicals, B570)
: 20 parts by weight

It is sectional drawing which shows one Embodiment of a polymer actuator. It is a schematic diagram which shows one Embodiment of the prepolymer which has a star-shaped branch structure. It is a graph which shows the relationship between an applied voltage and displacement, and measurement time. It is a graph which shows the relationship between an applied voltage and displacement, and measurement time. It is a graph which shows the relationship between an applied voltage and displacement, and measurement time.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Polymer actuator, 11, 12 ... Electrode layer, 20 ... Electrolyte layer.

Claims (4)

An electrolyte layer, and an electrode layer provided adjacent to the electrolyte layer,
The electrolyte layer is
A crosslinked structure formed by polymerization of a polymerizable composition containing a polyfunctional polymerizable compound having three or more polymerizable functional groups, and at least one selected from the group consisting of an oxygen atom, a sulfur atom and a nitrogen atom A crosslinked structure having a repeating unit containing a species of atom;
An ionic substance,
Polymer actuator.   The polymer actuator according to claim 1, wherein the polyfunctional polymerizable compound is a prepolymer having a repeating unit containing at least one atom selected from the group consisting of an oxygen atom, a sulfur atom and a nitrogen atom.   The polymer actuator according to claim 2, wherein the prepolymer has a star-shaped branch structure.   The polymer actuator according to claim 1, wherein the ionic substance is an ionic liquid.

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