JPH01164804A - actuator - Google Patents

Abstract

PURPOSE:To eliminate a limit related to working environment, by a method wherein a mechanochemical material is immersed in the electrolyte of a battery having a plurality of electrodes formed by different materials. CONSTITUTION:A polypyrol film formed by doping chlorine ion through electrolytic polymerization of pyrol under the presence of chlorine ion is formed on the surface of a platinum film to form an electrode 1. A mixture film of polystyrene sulfonic acid and polypyrol through electrolytic polymerization of pyrol under the presence of polystyrene sulfonic acid potassium having a molecular weight of approximate 70,000 is formed on the surface of a platinum film to form an electrode 2. The electrodes 1 and 2 and a mechanochemical material 3 are immersed in an electrolyte 4 to form an actuator. This constitution enables prevention of the generation of gas due to chemical reaction between the electrodes 1 and 2 and sealing of the actuator, resulting in the possibility to eliminate a limit related to working environment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an actuator using a mechanochemical material that causes mechanical deformation due to chemical change, and particularly relates to an actuator that uses a mechanochemical material that causes mechanical deformation due to chemical change. It relates to actuators that cause changes and produce mechanical deformations.

[Conventional technology]

It is known that the swelling and contraction of crosslinked polymeric materials can be controlled by the chemical environment, and attempts have been made to directly convert chemical energy into mechanical work using such mechanochemical materials. .

For example, Matsushima and Mori reported a method of filling a piston with particles of a crosslinked polymer material that swells and contracts with alkali and acid to push up the load (Matsushima and Mori: Production Research, 15.96 (1963)). ).

Furthermore, without supplying acids and alkalis as liquids,
Pioneering research is being carried out at General Electric Company in the United States to generate electrically generated materials around cross-linked polymeric materials. (R.P. Hamlen.

C, E, Kent, S, N, 5hafer;
ature, 206°1149 (1965)) Furthermore, a cell was formed in which the pH of an aqueous solution was changed by passing an electric current using a cation exchange membrane and an anion exchange membrane, and a mechanochemical material could be expanded and contracted within the cell. is being attempted. (A, Fragala et a
l ; Electrochimica Acta, 17
．． 1507 (1972)) also reported that during the day, a gel immersed in a solvent contracts by applying a voltage to a pair of electrodes that sandwich it, and that the amount of contraction is controlled by the applied voltage. .

(T, Tanaka et al;
CE, 218.467 (1982)) In this way, actuators that use crosslinked polymer materials as actuating substances, which are different from actuators in practical use today, have low specific gravity, light weight, and mechanical properties similar to muscles. This has been the subject of much research for these reasons, and attempts have been made to electrically drive such actuators as a method to achieve simple control.

[Problem that the invention is trying to solve] However,
According to conventional reports, the voltage applied to the electrodes to electrically drive these crosslinked polymer materials is l
The value is from volts to about 30 ports. The liquid in which the cross-linked polymer material is immersed is mainly water-based, so if a voltage higher than 1.23 volts, which is the theoretical decomposition voltage of water, is applied to such a liquid, For example, it is inevitable that gas will be generated from the system due to the decomposition of water. If the actuator inevitably generates gas when driven, the entire actuator cannot be sealed, which limits the environment in which it can be used. Further, during repeated use, it is necessary to regularly replenish water that is lost due to decomposition, which poses problems in the lifespan and maintainability of the actuator. Furthermore, actuators that generate acid/hydrogen explosions from water when driven have safety problems. If a sufficiently dehydrated nonaqueous solvent system is used as the liquid, the above-mentioned problem of electrolysis of water can be avoided, but depending on the applied voltage, electrolysis of the solvent or solute may occur. If the decomposition product is a gas, problems similar to those of water electrolysis described above arise. Further, even if the decomposition products are solid or liquid, undesirable phenomena such as covering the electrode surface and forming a film with low conductivity may occur. Although the mechanism of the phenomenon in which mechanochemical materials are electrically deformed in a liquid remains unclear even today, it is possible to It has become clear that deformation of chemical materials occurs and that significant deformation does not occur even when voltages are applied to electrodes such that little electrochemical reaction occurs on the electrodes. Therefore, in order to put into practical use an actuator that electrically deforms such a mechanochemical material, it is necessary to solve the above-mentioned problems regarding the electrochemical reactions that proceed on the electrodes.

[Means and effects for solving the problems] In the present invention,
In an actuator in which a mechanochemical material is changed by electrical action, the actuator can be sealed by preventing the generation of gas due to electrochemical reactions at the electrodes, thereby eliminating restrictions regarding the environment in which it can be used. Furthermore, in addition to preventing the constituent components of the actuator from being lost to gas due to electrochemical reactions, the actuator is sealed to prevent volatile constituent components such as solvents from evaporating, so that it can be used for a long period of time. This provides a maintenance-free actuator that does not require replenishment of these components. Furthermore, the reversibility of the electrochemical reaction at the electrode is ensured, and the reversible drive of the actuator is guaranteed. Furthermore, it prevents the formation of a low-conductivity layer on the electrode surface as a result of electrochemical reactions in the electrode, and keeps the electrode in a state where sufficient drive current can be supplied to the actuator, allowing rapid actuation. It is to do so.

The present invention involves immersing a mechanochemical material that swells or contracts in response to changes in various ion concentrations into an electrolyte solution for a battery formed by having a plurality of electrodes made of different materials. It is characterized by driving the mechanochemical material by changing the ion concentration in the electrolyte by charging or discharging the battery.

Such mechanochemical materials, which swell or contract in response to changes in ion concentration, have functional groups in their main chains that interact with specific ions in the electrolyte to form bonds such as ionic bonds and coordinate bonds. Alternatively, it must be a crosslinked polymer having on its side chain. Such polymers include, for example, carboxyl groups and sulfonic acid groups as some of their constituent units.

It is a polymer that has one or more types of polar groups such as hydroxyl groups, amine groups, imino groups, carbonyl groups, etc., and the amount of these polar groups present is 50 micro equivalents or more, 50 micro equivalents per 1 g of dry weight of mechanochemical material. It should be in the milliequivalent range or less. In other words, when the amount of polar groups present is less than this, even if a bond is formed between the polar group and the above-mentioned specific ion, the abundance ratio to the entire polymer is small, so the properties of the polymer cannot be sufficiently changed. First, as a mechanochemical material, it cannot undergo effective deformation in liquid. Moreover, if the amount of polar groups present exceeds the above range,
Since the amount of the above-mentioned specific ions required to sufficiently change the properties of the polymer increases, it becomes difficult to electrically control this ion amount by practical means.

On the other hand, the ionic species whose concentration is controlled in order to deform the mechanochemical material as described above can be any of cationic species, anionic species, inorganic ion species, organic ion species, etc. It is necessary that the mechanochemical material can interact with the polar groups that it has in its molecular structure and form bonds such as ionic bonds and coordinate bonds.

Furthermore, these binding equilibria must be able to shift significantly with control of the concentration of external ionic species.

To give a specific example, when a hydrogen ion is used as an ionic species, the equilibrium of the bond between a polar group and a hydrogen ion is determined by the value known as the acid dissociation constant of the polar group or the conjugate acid of the polar group. can be evaluated. The solvent that can be used to carry out the driving method of the present invention is not particularly limited as long as it is a polar solvent that can solvate the ionic species. Mixed solvents can be used.

When water or a mixed solvent mainly composed of water is used, the hydrogen ion concentration that can normally be achieved is in the range of 1M or less and 10-'M or more.
The range is less than M and more than 10-18M. Therefore, due to changes in hydrogen concentration within this range, the acid dissociation equilibrium of the polar groups of the polymers constituting the mechanochemical material or the conjugate acids of those polar groups must change significantly. is less than 10-2M, 10-12
M or more, particularly preferably 10-” M
Hereinafter, a range of 10-"M or more is desirable. When using water or a mixed solvent mainly composed of water as a solvent, it is also possible to consider hydroxide ions, which are conjugated bases with respect to the solvent, instead of hydrogen ions. From the same discussion as above, it is clear that the appropriate range for the acid dissociation constant of the polar group possessed by the polymer constituting the mechanochemical material or the conjugate acid of the polar group is the same as that described above.

When using a solvent that contains all (or almost no) water, the above range of acid dissociation constants no longer generally applies, but depending on each solvent, the same arguments as above can be made. There is an optimal range for each.

Similar to the case of hydrogen ions, even if other ionic species are used,
The ions used form ionic bonds with the polar groups of the polymers that make up the mechanochemical material.

If a coordinate bond can be formed, it is possible to drive a mechanochemical material according to the present invention, but in that case, the complex dissociation constant between the polar group and the ionic species needs to be an appropriate value. . This is because when the concentration of general ionic species is controlled by the electrochemical method of the present invention, the concentration range that can be practically obtained is 10-1M or less and 10-'M or more.

In a concentration range higher than this, a large amount of electricity is required to obtain a significant concentration change, so the current density or current application time must be increased, which is not practical. Also,
If one attempts to control a trace amount of ions of 10-'M or less, it is difficult to avoid the influence of other coexisting ion species, which is impractical (with regard to the hydrogen ions mentioned above,
' The reason why it was possible to control the concentration at a level below M is that the hydrogen ion concentration could be equivalently controlled by controlling the concentration of a conjugate base such as hydroxyl ion at a relatively high concentration. ). From this, the complex dissociation constant between the polar group of the polymer constituting the mechanochemical material and the above-mentioned ions must be within a certain range, and according to experiments, this range is 0.1 M or less, 10 -''M or more. Note that a complex formation reaction generally proceeds through multiple steps, and the complex dissociation constant referred to here refers to the successive complex dissociation constant for each of those steps.

Polyaniline is known as a conductive polymer material.

Polypyrrole, polythiophene, polyphenylene.

Polymers such as polyazulene and polyacetylene are known to reversibly release and absorb anions or cations as a result of redox reactions in their polymer chains. An electrode can be made by using an electrode material as a base and coating the surface with these conductive polymer materials, and the concentration of anions or cations can be controlled by passing current through an electrolytic solution.

Electrodes that can be used in the practice of the present invention are those that can electrochemically reversibly change the concentration of a certain ion in the electrolyte, and as long as they have this property, they can be used in the above examples. It is not limited to. However, it is necessary to avoid generating gases such as hydrogen and oxygen due to reactions on the electrodes. Therefore,
It is necessary to use a combination of ions and electrodes that can control the ion concentration as described above at a potential that does not substantially exceed the generation potential of hydrogen, oxygen, etc. in the electrolytic solution used.

Furthermore, in order to pass current through the system, at least one pair of electrodes is used, and at this time, a pair of electrodes must be used to control the concentration of different types of ions. This is because when current is passed between electrodes that control the concentration of the same ion, with one electrode as the anode and the other as the cathode, the ions are supplied to the electrolyte from one electrode, but the ions are supplied to the electrolyte at the other electrode. In principle, equal amounts of ions are consumed, and as a result the purpose of changing the ion concentration is not achieved. Generally, in a pair of electrodes to be used in the method for driving a mechanochemical material of the present invention, ionic species released into or supplied from the electrolyte by an electrode reaction that dominates the potential of one electrode are simultaneously applied to the other electrode. The above condition must be satisfied that it does not participate in the electrode reaction. More specifically, this can be achieved by satisfying the following two conditions. (1) Select electrodes that involve anions in the electrolytic solution and cations that participate in the electrode reaction, and pass a current between them. (2) Selecting materials such that the potential at which the anion is oxidized on the opposite electrode is more positive than the potential of the electrode reaction involving the cation on that electrode. (3) Similarly, materials are selected such that the potential at which the cation is reduced on the opposite electrode is more negative than the potential of the electrode reaction involving the anion on that electrode.

In addition, since it is necessary that the concentration of the ions changes sufficiently by passing an electric current, the anions and cations are generated between them or with ions previously dissolved in the electrolyte. The salt must be readily soluble in the solvent used for the electrolyte.

If a pair of electrodes, chosen keeping in mind the above points, is immersed in a suitable electrolyte solution containing ions corresponding to the electrodes, a battery is formed and a potential difference is created between the electrodes (of course, in special cases, the potential difference can also be zero). By charging or discharging such a battery, an electrochemical reaction progresses on each electrode, and the concentration of specific ions in the electrolyte changes.

Therefore, if a mechanochemical material that has the property of deforming according to the change in the concentration of the ions is present in the electrolyte, it can be deformed. Several mechanisms of deformation due to changes in ion concentration in mechanochemical materials have been described. For example, mechanochemical materials composed of polymers with weakly acidic or weakly basic functional groups have This change causes an increase or decrease in the charge density on the polymer chains, which mainly changes the magnitude of the interaction between the polymer chains and changes the degree of swelling of the entire mechanochemical material. Also, for example, ionic bonds with metal ions such as carboxyl groups.

A functional group that can have relatively strong interactions such as coordination bonds.

By interacting with these ions, mechanochemical materials composed of polymeric materials that have Since the dots are formed, the degree of swelling changes according to the change in the concentration of ions. In addition, even in mechanochemical materials composed of polymeric materials that do not have functional groups that interact particularly strongly with ions, changes in ion concentration may cause, for example, differences in the osmotic pressure of fluids inside and outside the material. The degree of swelling changes due to changes in the number of solvent molecules that solvate relatively highly polar functional groups in the molecular structure.

In this way, the mechanochemical material can be driven by passing current through the pair of electrodes, and if an electrochemically reversible system is selected, the mechanochemical material can be driven reversibly. It is clear that this method can be used for new actuators and the like. Note that it is also a preferred embodiment of the present invention to use a large number of electrodes for the purpose of rapidly and evenly changing the ion concentration in the electrolytic solution.

〔Example〕

[Example-1] Two platinum films were irradiated with ultrasonic waves in an alumina powder suspension to roughen the surface. - Pyrrole is electrolytically polymerized in the presence of chlorine ions to form a polypyrrole film doped with chlorine ions on the surface. The other one has a molecular weight of about 7
Pyrrole was electrolytically polymerized in the presence of 10,000 potassium polystyrene sulfonate to form a mixed film of polystyrene sulfonic acid and polypyrrole on the surface, and then in a KCn solution, which corresponded to 8% of the amount of electricity required for electrolytic polymerization. A quantity of electricity is passed in the opposite direction to partially reduce the mixed membrane.

The two electrodes thus created are shown in FIG. 1, electrode 1.
This is called electrode 2.

30mj of a monomer aqueous solution of 0.6M N-isopropylacrylamide, 0.12M N-methylolacrylamide, and 0.08M sodium acrylate! is prepared, tetramethylethylenediamine and ammonium persulfate are added as initiators, and radical polymerization is performed to obtain a polymer solution.

FIG. 2 is an illustration of another embodiment of the invention, in which the mechanochemical material 3 is shaped into a cylinder, with electrodes 1.2 arranged closely along the inside and outside of the cylinder. With the configuration shown in this figure, an electrode having a relatively wide area can be accommodated in a limited volume. Furthermore, this is one of the preferred embodiments because the time required for ion diffusion between the electrode and the mechanochemical material can be shortened.

FIG. 3 is an explanatory diagram of yet another embodiment of the present invention.

In the figure, mechanochemical material 3 is formed into a rod shape, and electrode 1
, 2 has electrodes having a shape having a large number of branches arranged closely together. This configuration is one of the preferred embodiments because the electrode area can be made relatively large using limited electrode materials. The shape of electrodes 1 and 2 is as follows:
It is also possible to use needle-like electrodes with many branches, mesh-like electrodes, and even electrodes with multiple plate-like protrusions.
This is a preferred embodiment of the present invention.

After defoaming, this liquid is extruded into a saturated aqueous sodium sulfate solution through a nozzle with a diameter of 0.4 mm to solidify it into a thread. The thread-like polymer was vacuum dried at 150°C for 3 hours and finally dried with 3 x 10-3 mol of K.
Mechanochemical material 3 is obtained by washing with C1 aqueous solution. In addition, an aqueous solution of KCj! of 3 x 10-" moles is used as electrolyte 4. Using the above materials, a device of the form shown in FIG.
When a current is passed between and 2, it is observed that the mechanochemical material 3 contracts to about 78% of its original length and the fitting 7 is pulled up.

Next, when the same amount of electricity is passed in the opposite direction, the length of the mechanochemical material 3 recovers to about 98% of its initial length. By repeating energization and energization in the opposite direction five times in this way, reversible expansion and contraction of the mechanochemical material occurs, and during this time,
It was confirmed that no air bubbles were visually observed in the container.

[Example 2] Two platinum films with roughened surfaces were prepared in the same manner as in Example 1, and the - sheet was electropolymerized with aniline in the presence of sulfate ions, and the surface was coated with polyaniline doped with sulfate ions. Form. For the other sheet, a mixed film of polystyrene sulfonic acid and polypyrol was formed in the same manner as in Example Q, and when a device of the form shown in FIG. Shrinkage of the mechanochemical material is observed almost the same as in Example 1.

In the device of this example as well, the mechanochemical material expands and contracts reversibly depending on the direction of the current, and at this time, no bubbles are observed to be generated within the device.

〔Effect of the invention〕

As explained above, by using an actuator made of a mechanochemical material using an electrolytically polymerized membrane, it is possible to provide a sealed actuator without the generation of bubbles, which has been a problem in the past. With the actuator of the present invention,
Mechanochemical materials can be electrically driven without irreversibly decomposing the constituent components of the system, and therefore reversible driving is possible and there is no need to replenish decomposed components.

Furthermore, it is possible to provide an actuator that exhibits smooth movement with low current.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the method for driving a mechanochemical material according to the present invention. FIG. 2 is an explanatory diagram showing an example of an apparatus for carrying out the method for driving a mechanochemical material according to the present invention, in which the mechanochemical material is made into a pipe shape and two electrodes are arranged along the outer and inner walls. be. FIG. 3 is an explanatory diagram showing an example of an apparatus for carrying out the method for driving a mechanochemical material, similar to FIGS. 1 and 2;
Two electrodes are installed in the form of branches. 1... Electrode 1 2... Electrode 2 3... Mechanochemical material 3 4... Electrolyte 5... Container 6... Flexible film 7... Connection device patent applicant Canon Co., Ltd. company

Claims (1)

[Claims] A mechanochemical material is a mechanochemical material that is composed of a crosslinked polymer and a liquid that can be impregnated with it, and in which the crosslinked polymer swells or contracts in response to changes in various ion concentrations such as ionic strength and pH in the liquid. An actuator comprising: two or more electrodes substantially made of different conductive polymer materials and the mechanochemical material immersed in the liquid.