JPH04122764A - Conductive polymer gel - Google Patents

Abstract

PURPOSE:To prepare the title gel applicable to a chemomechanical system and excellent in electric conductivity and durability by selecting the title gel using a specific substance as the medium. CONSTITUTION:The title gel (e.g. one obtd. by doping polydimethylaminopropylacrylamide with tetracyanoquinodimethane) using an org. substance (e.g. dimethylformamide) as the medium is selected.

Description

[Detailed Description of the Invention] In recent years, the demand for incorporating the sophisticated motor functions of living organisms into engineering systems has been increasing with the rapid development of highly functional robots and system control methods.

However, when simulating the movement functions and mechanical energy generation mechanisms in living organisms, the ability and scope of application are naturally limited when conventional rigid materials mainly made of metal are used.

This is why it is necessary to develop active soft-body machines and soft-body materials that perform work, such as those found in biological muscles, which are mainly made of polymer gels.

A polymer gel is a substance in which a polymer with a three-dimensional network structure coexists with a liquid medium; when the medium is water, it is called a hydrogel, and when the medium is an organic substance, it is called an organogel.

<Prior Art> In recent years, research on chemomechanical (mechanochemical) systems using polymer hydrogels has been actively conducted. Chemomechanical systems are systems that achieve deformation (contraction, expansion, bending) and generate stress due to environmental changes and external stimuli such as pH changes, temperature changes, solvent exchange, light, and electrical stimulation, and are applied to artificial muscles and actuators. can. −
Examples include polymethyl vinyl ether fibers produced by temperature changes and bipolar polymer electrolyte gels produced by solvent substitution. Among these, a comparatively large number of researchers are conducting basic development research on electrically driven chemomechanical systems because they are easy to operate and have a variety of input forms. For example, it is known that when a voltage is directly applied to a polyacrylic acid gel, the gel contracts and deforms, and drive systems and chemical valves (selection 11, sustained release control, etc.) that utilize this principle are being used. Furthermore, such a gel can be made into a sandwich element using transparent electrodes, etc., and by passing an electric current through the necessary parts, it can be contracted and deformed and colored, and can be used as various display and recording elements such as displays (for example, Suzube et al. Edited by Hiroyuki “Mechanochemistry”
(See Maruzen, +989). However, this system has significant drawbacks. It involves electrolysis of water, which is used as a gel medium, so it has low efficiency and generates gas. The former is an impediment to achieving faster and higher responsiveness, and the latter is a major barrier to the development of sealed devices. Another drawback is that water evaporates and durability is lacking. On the other hand, polymer gels (organogels) swollen in organic media do not generate gas, but they generally have extremely low electrical conductivity and have never been applied to electrically driven chemomechanical systems.

Under the above circumstances, the development of a chemomechanical system that operates by electrical stimulation without gas generation has been long awaited. This research is concerned with the development of organogel with high electrical conductivity in consideration of this situation.

The present invention relates to a method for changing the shape of a polymer material using electrical energy as a medium, and more specifically, by applying a potential, a polymer material medium is reversibly expanded and contracted without generating bubbles, and converted into mechanical energy. It is concerned with the method of changing the form. This invention will be described in detail below.

Using this method, it is possible to achieve a current equal to or higher than that of the conventional /X hydrogel, and it does not involve any gas generation, so it can be applied to highly efficient and closed-type chemomechanical / stems. be. Furthermore, since a high boiling point solvent can be used as the medium, evaporation of the medium is also reduced.

The principle of the morphological change in this research is based on polymer charge transfer complexes (C
-T complex) formation, or based on highly swellable and highly conductive polymer gels through donor-acceptor interactions. That is, when an electron-donating component and an electron-accepting component coexist in a polymer gel, the two form a complex through charge transfer interaction. Since this complex generally has ionic properties, it has high conductivity even in organic solvents when voltage is applied. Therefore, when a voltage is applied to such a gel, the medium components undergo an electrokinetic phenomenon.
cPheno anon) moves to the opposite electrode, causing the gel to contract or swell. The principle can be considered similar to the contraction and expansion phenomenon in the case of hydrogels. (These details can be found in the above-mentioned book, Y,
0sada, Advances in Polym
er 5science82 Conversion
of Chemical Into M
mechanicalEnergy by 5ynt
hetic Polymers (Chemome
chani-cal Systems), Spring
ger (+987)). However, the important thing here is that in the case of hydrogels, water is used as a solvent, so hydrogen and oxygen are generated due to water electrolysis, but in the case of organogels like the one in this study, Since there is no water decomposition, there is no gas generation.

As components that form a polymer CT complex or perform donor-acceptor interactions, both may be polymers, or one may be a low molecule. Alternatively, the low-molecular CT complex may be dispersed in a suitable polymer gel. Here are some specific examples.

Nitrogen, oxygen, sulfur, aromatic rings, etc. are generally electron-donating groups. Therefore, polymers containing these elements, such as polydimethylaminopropylacrylamide (PDM
APAA), poly4-vinylpyridine, polystyrene, etc., are synthesized by, for example, radical polymerization,
When this is swollen in a polar solvent such as dimethylformamide and impregnated with an electron-withdrawing compound such as tetracyano-cow-nodimeta-7 (TCNQ), phthalocyanine, chloranil, etc. (doping), the polymer network forms a CT complex and [ A taut and sometimes colored gel is obtained (hereinafter referred to as CT gel). Table 1 shows examples of polymer donors and low molecule acceptors. C thus obtained
T-gels are generally 10-5 to 102 due to charge transfer interactions.
It has high electrical conductivity.

The above gel is obtained by reacting a charge-withdrawing low molecule with an electron-donating polymer, but the reverse is possible, that is, a combination of an electron-withdrawing low molecule and an electron-donating polymer is also possible.

An example is a reaction of maleic anhydride polymer gel with pyridine in DMF. In addition, when both are low molecular weight, specifically, triethylamine and tetracyanobenzene may be solubilized in dimethyl sulfoxide of, for example, structured methyl methacrylate. Examples of these electron-donating compounds include compounds containing a pyridyl group, a carbazole group, an ether group, an imidazole group, a phenyl group, a naphthyl group, an anthryl group, and the like. Further, examples of electron-accepting compounds include chloranil, benzoquinone, iodine, tetracyanoethylene, and tetra/anobenzene.

As a method for synthesizing highly conductive polymer organogel, a polymer gel may be synthesized by a polymerization reaction after coexisting an electron-donating compound and an electron-accepting compound, or after synthesizing a polymer gel in advance. , a complex may be formed by later impregnating with one component of the CT complex. It is also possible to form a complex while applying a voltage, and in this case, a change in form can be brought about simultaneously with the formation of the complex.

The solvent may be any organic compound, including DMF,
Dimethylsulfoquine (DMSO), propylene carbonate (PC), acetonitrile, etc. are suitable because they are chemically inert and have a high boiling point.

If the polymeric substance constituting the gel itself has the ability to retain its shape, it can be used as is, or by applying a gelling agent, a crosslinking agent, or an appropriate insolubilization treatment as necessary, it can be used to form gels, films, laminated membranes, fibers, etc. Can be used in solid form. In order to effectively charge these substances, an appropriate solvent such as alcohol or acetone may be used in combination depending on the case. Furthermore, for the purpose of controlling the charge state, salts such as sodium chloride, tetrabutylammonium salts, organic phosphates, long-chain fatty acids, etc., and organic electrolytes can also be mixed.

When a DC voltage is applied to such a gel using a suitable electrode, the gel deforms. At this time, when the electrode is in contact with the gel, it generally contracts, and when it is away from the gel, it contracts, expands, or bends depending on the conditions (rIIJl). The dilatation of these conductive polymer gels is influenced by this material, the solvation state of the gel, the charge density, etc., and therefore the deformation response and the converted mechanical energy are influenced.

A In the present invention, the electric potential applied to the thin molecular chemomechanical substance is not particularly limited, but generally ranges from several volts to several hundred volts.The value depends on the size, physicochemical state, and charge of the chemomechanical stretchable polymer. Determined by density etc. Direct current is the most efficient electrical stimulus to apply, but modified waves such as rectangular waves and sine waves may also be used. but,
The efficiency decreases as the frequency increases, so a range of several hertz to several tens of hertz is desirable. Further, voltage application may be performed through the gel in the atmosphere or through a suitable conductive medium.

The electrode to which the voltage is applied may be a platinum plate, platinum wire carbon plate, carbon wire, transparent electrode, ITO glass, or the like. However, as mentioned above, the deformation behavior differs depending on whether it is in contact with the gel or away from the gel, so it is necessary to use it properly depending on the purpose. Examples of uses of such reversible tactile transformation and mechanical energy generation systems using electrical energy include the following.

(1) Application as actuators or artificial muscles controlled by electrical stimulation.

(2) Electric diaphragm or sound wave generating plate or vibration absorbing material as a piezoelectric material.

(3) By installing a membrane or valve on a pipe through which liquid or gas flows, and applying an electric potential to this membrane or valve! 1[
The flow rate of liquid and gas is controlled by expanding and contracting the membrane and the valve. (Chemical pulp) Furthermore, solutes in the circulating liquid are selectively separated.

(4) Switching elements, relay devices, vibrators, no-saws (5) Sensors sensitive to humidity and metal ions (6) Lenses that can electrically focus, apertures, crystalline lenses, artificial eyes such as iris, artificial fingers, etc. Artificial legs, electrically bending bimetallic deformations, and rock destruction.

(7) Prevention of water leakage.

(8) Dehumidification and dehydration agent.

(9) Water-absorbing material that operates repeatedly.

(IO) Salt removal gel, electrodialysis gel.

Examples will be described below.

Example 1 Methylene bisacrylamide (MBA
A) 0.1 g and 100 mg of azobisisobutylnitrile (A IBN) as a radical polymerization initiator were dissolved, and polymerization was carried out at 60°C for 20 hours under an argo atmosphere according to a conventional method.
PAA) A gel was obtained. This gel is T CN Q
A CT polymer gel was prepared by immersing and doping in DMF solution 1001 containing 10 g for 3 days. Upon impregnation with TCNQ solution, the PDMAPAA gel took on a dark green color, indicating CT complex formation. At the same time, the volume is the first 3
It has doubled. The visible absorption spectrum of this sample shows that in addition to the absorption based on TCNQ (400n), the visible absorption spectrum is 750.
[Based on CTff body formation of 150n (absorption was observed, confirming that CT gel was created.

The thus obtained hCT gel exhibited electrical conductivity as shown in Table 2 due to TCNQCN conversion.

The samples in Table 2 were cut into rectangular parallelepipeds measuring 30 x 10 x losm, and when a current of 0.3 mA was applied in the atmosphere using the apparatus shown in Figure 1-a, the gel shrank as shown in Table 3-1.

In addition, using the apparatus shown in Figure 1-b, the gel was mixed at 0.5 aol/IT.
1. CNQ immersed in DMF solution 10-1.
When a current of omA was applied, the gel shrank as shown in Table 3-2.

Example 2 Gel 10 with a length of 30 cm and a diameter of 41 cm obtained in Example 1
m1, 4 X 10-'■ D of TCNQ of 01/1
A pair of platinum electrodes were placed at a distance of 10 mm from both sides of the gel using the apparatus shown in FIG. 1-c. Then, when a voltage of 20 volts was applied, expansion and contraction of the gel was observed as shown in Table 4.

Example 3 0.2 gs of ethylene glycol methacrylate as a crosslinking agent, 2 g of tetracyanoethylene as an acceptor, and 100 ml of azobisisobutyronitrile as a polymerization initiator were dissolved in a DMS O20 solution containing 51 vinyl carbazole. , 25 at 60℃ according to the conventional method.
Polymerization was carried out under vacuum for hours to obtain a charge transfer complex gel. After parallel swelling of this gel in a large amount of DMSO, it was cut into a cylinder with a length of 50 cm and a diameter of 10 cm, and a pair of platinum electrodes were brought into contact with both ends of the gel using the apparatus shown in Figure 1-b. 3. While immersed in DMS○30 Otori 1. When a DC voltage of O1^ was applied, the gel contracted as shown in Table 5.

Example 4 The gel obtained in Example 1 was immersed in 1 x 10-2 mol/l of TCNECN, and a pair of carbon electrodes (electrode area: 4 cm) were placed at a distance of 20 mm from each end of the gel.
m2) were arranged in parallel. Then, when a voltage of 50'f was applied according to the method of Example 2, bending of the gel as shown in Table 6 was observed.

Example 5 4g DMAPAA, 30 Snow I water, 150++! 80 g of SPAN was mixed as an emulsifier into benzene. To this was added 10 g of potassium persulfate as a polymerization initiator and 20 g of methylenebisacrylamide as a crosslinking agent, and emulsion polymerization was carried out at 60 DEG C. for 48 hours in a four-necked flask with vigorous stirring under an argon atmosphere. After the reaction solution was filtered, it was washed with a large amount of water and methanol and subjected to equilibrium swelling. The diameter of the obtained PDMPAA microparticles was 100-300μ.

1 piece of PDMAPAA particles obtained in this way
using a pair of transparent electrodes (CITO, distance between electrodes 115 mg) as shown in Figure 1-d, at 5 V/
When a voltage of cm was applied, the particles shrank at the speed shown in Table 7.

Example 6 1 PDMAPAA microparticle obtained in Example 5
++ ol/I of a DMF solution containing TCNQ. When a voltage of 5 V/c- was applied using the apparatus of Example 5, the microparticles expanded as shown in Table 8.

0.8rnA Table 3-1 1.0mA Table 3-2 Table 6 a Moving path at the lower end of Nigel l1l (a @) b = Nigel length (30 mm) Table 7 d 'tζ7 Procedural amendments 1, Indication of the case 1990 Patent Review No. 24 07 2, Name of the invention Conductive polymer gel 3゜ Person making the amendment Relationship to the case Patent applicant address Mito, Ibaraki Prefecture Ichihorimachi Name: Yoshihito Nagata 47-94 Agent (zip code: 150) Shibuya Homes 423, 2-1 Udayoumachi, Shibuya-ku, Tokyo November 13, 1990 (Delivered: November 27, 1990) 6 , "Brief explanation of drawings" item of the specification subject to amendment and statement 7 in that column,
The following statement will be added to page 19 of the detailed statement of amendments.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are cross-sectional views illustrating a case in which a DC voltage is applied to a pair of electrodes for gel contraction in a chemomechanical measuring device, and FIG.
d) is a perspective view showing an example thereof. ”

Claims (6)

[Claims] (1) Conductive polymer gel using an organic substance as a medium. (2) The conductive polymer gel according to claim 1, which is based on charge transfer complex formation. (3) Deformation (contraction, expansion,
The polymer gel according to claim 1, which bends). (4) The polymer gel according to claim 1, which comprises a polymer donor and a low molecule acceptor. (5) The polymer gel according to claim 1, wherein the electrical stimulation is a DC voltage. (6) Polymer gel according to claim 1 using a high boiling point organic solvent as a medium