JP2003306531A - Method for electrolytic asymmetric polymerization of conjugated polymer and optically active conjugated polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for an asymmetric polymerization of a conjugated polymer which simply controls the high-order structure of the conjugated polymer, and does not require a complicated operation of column separation or the like. <P>SOLUTION: The method for the asymmetric polymerization of the conjugated polymer comprises adding at least a chiral dopant, a monomer, and a support electrolyte to a nematic liquid crystal, and applying a voltage to the resulting mixture. Compounds having a low ionization potential such as 3,4-ethylene dioxythiophene, isothianaphthene, pyrrole and thiophene are used as the monomer. Thus, the optical activity in the field of the liquid crystal reaction and a spiral structure can be reflected to the conjugated polymer. Further, an optically active conjugated polymer can be obtained without undergoing a complicated isomer separation operation. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The invention of this application relates to electrolytic asymmetric polymerization of a conjugated polymer. More specifically, the invention of this application provides for the electropolymerization of monomers in a nematic liquid crystal in the presence of a chiral dopant,
The present invention relates to a method for polymerizing an optically active conjugated polymer.

[0002]

2. Description of the Related Art Conductive polymers typified by polyacetylene, polythiophene, polypyrrole, and polyaniline have a conjugated double bond in their structure, and therefore show electrical conductivity by doping with iodine or the like. These conjugated polymers can be electropolymerized, and a polymer thin film can be obtained on the anode side by adding a monomer to the electrolyte solution and applying an appropriate voltage.

Conventionally, the electropolymerization of conjugated polymers is carried out by dissolving an electrolyte such as lithium perchlorate or tetrabutylammonium perchlorate in an organic solvent such as acetonitrile and applying an electric field between the anode and the cathode. Came.

However, many of these conjugated polymers are
Since it is insoluble or infusible in most solvents, the electrolytic polymerization method in such a solution system has a problem that its solid structure and morphology are determined at the time of polymerization. In other words, a method of controlling the higher-order structure of the conjugated polymer, a method of providing a helical structure while maintaining conductivity, and a method of obtaining an optically active substance without separation and purification by a column or the like are known. The reality was that there was no such thing. If a simple method for asymmetrically polymerizing a conjugated polymer can be obtained, it is expected to be effective as a new electronic material. In addition, since many biomolecules such as RNA and protein have a helical structure, it is expected that if asymmetric polymerization of a conjugated polymer is realized, new knowledge about biomolecule synthesis will be brought about.

[0005]

[Non-Patent Document 1] K. Akagi et al., Science, Vol. 282,
1683-1688 (1998).

[Non-Patent Document 2] K. Akagi et al., Synthetic Metals,
119, 103-104 (2001).

[Non-Patent Document 3] Akagi, K., Piao, G., Kaneko. S., S
akamaki.K., Shirakawa, H. and Kyotani, M., Scienc
e, 282, 1683-1686 (1998).

[Non-Patent Document 4] Shirakawa, H., Current Appl. Phy
s., 1, 88-89 (2001).

[Non-Patent Document 5] Akagi, K., Kobunshi 44, 456 (199
Five).

[Non-Patent Document 6] Akagi, K., Shirakawa, H., Arraya,
K., Mukoh, A., Narahara, T., Polym. J. 19, 185 (19
87).

[Non-Patent Document 7] Solladie, G., Zimmermann, G., Ange
w. Chem. Int. Ed. Engl., 23, 348-362 (1984).

[Non-Patent Document 8] Huck, NPM, Jaeger, WF, Lan
ge, B., Fringe, BL, Science, 273, 1686-1688 (199
6).

Therefore, the invention of this application solves the problems as described above, controls the higher-order structure of the conjugated polymer, and eliminates the need for complicated operations such as column separation. It is an object to provide a method for simultaneous polymerization.

[0007]

Means for Solving the Problems The invention of this application is intended to solve the problems as described above. First, there is a method for polymerizing an optically active conjugated polymer. A method for electrolytic asymmetric polymerization of a conjugated polymer, which comprises adding at least a chiral dopant, a monomer and a supporting electrolyte and applying a voltage.

Secondly, the invention of this application provides an electrolytic asymmetric polymerization method for a conjugated polymer in which the nematic liquid crystal is selected from the group consisting of alkylphenylcyclohexyl type, alkylcyanobiphenyl type, and alkoxycyanobiphenyl type. Thirdly, a method for electrolytic asymmetric polymerization of a conjugated polymer in which the chiral dopant is a chiral liquid crystal compound is provided.

Fourthly, the invention of this application is
3,4-ethylenedioxythiophene, isothianaphthene,
Provided is an electrolytic asymmetric polymerization method of a conjugated polymer which is at least one selected from the group consisting of pyrrole and thiophene.

The fifth aspect of the invention of this application provides that the supporting electrolyte is selected from tetrabutylammonium perchlorate or lithium perchlorate as an embodiment of the electrolytic asymmetric polymerization method of the conjugated polymer. To do.

Sixth, the invention of this application also provides an optically active conjugated polymer obtained by any one of the above-mentioned polymerization methods.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present application have hitherto found that by adding a chiral dopant to a liquid crystal, optical activity can be imparted to the entire liquid crystal or a chiral nematic phase having a helical structure can be obtained. Reporting.
Further, the inventors have reported that polyacetylene is synthesized by bringing an acetylene gas and a catalyst into contact with each other in such a chiral nematic liquid crystal. (For example, Non-Patent Documents 1 and 2) As a result of further diligent research, the inventors have conducted an electropolymerization of a conductive polymer by using such a liquid crystal as an asymmetric reaction field to enhance the optically active conjugated system. The inventors have found that a molecule can be obtained, and arrived at the present invention.

That is, in the electrolytic asymmetric polymerization method of the conjugated polymer of the invention of this application, the nematic liquid crystal is
At least a chiral dopant, a monomer and a supporting electrolyte are added and a voltage is applied.

At this time, the nematic liquid crystal used as the reaction field may be in any form as long as it does not interfere with the electrolytic polymerization reaction. Liquid crystals are generally classified into nematic, cholesteric, and smectic, but nematic liquid crystals are required to obtain an organic chiral nematic phase as a reaction field. Among them, thermotropic liquid crystals that can realize a liquid crystal form without including a solvent are preferable. In addition, the main chain type and the side chain type are classified into the main chain type liquid crystal having the mesogen in the main chain even if the side chain type liquid crystal in which the liquid crystal forming group (mesogen) is introduced into the flexible main chain is used. It may be. The structure of such a liquid crystal is not particularly limited, and for example, two benzene rings are connected by a connecting group containing a double bond such as trans-stilbene, azoxybenzene, or nitrone, or a connecting group such as biphenyl or cyclohexane. Is exemplified. Furthermore, it is preferable that a flexible substituent such as an alkyl group or an alkoxy group is introduced at the end of the mesogenic compound.
A substituent having an aliphatic chain, a rigid straight chain, or an asymmetric structure may be introduced. The length of these substituents affects the transition temperature of the liquid crystal, and may be appropriately selected in consideration of the temperature of electrolytic polymerization.

Among the various liquid crystals as described above, those which can maintain the liquid crystal state at room temperature or above and have a wide temperature range showing a liquid crystal phase, specifically, 5CB and 6CB of the following formula, or a phenylcyclohexyl group and n PCH _n OR having an alkyl group and a hexamethylene chain is preferred.

[0016]

[Chemical 1]

In the method of electrolytic asymmetric polymerization of a conjugated polymer according to the invention of this application, a chiral dopant can be added to a nematic liquid crystal to impart optical activity or a helical structure to the liquid crystal to obtain a chiral nematic liquid crystal. . As long as these chiral dopants do not inhibit the electropolymerization reaction and have high compatibility with the nematic liquid crystal,
The type is not particularly limited. Various axial chiral compounds, especially chiral liquid crystal compounds can be applied, and preferable examples include binol derivatives and phenylcyclohexyl compounds having asymmetric carbon. Specific examples thereof include a binol derivative represented by the following chemical formula (I) or (II) and a phenylcyclohexyl compound represented by the chemical formula (III) or (IV).

[0018]

[Chemical 2]

[0019]

[Chemical 3]

Further, in the electrolytic asymmetric polymerization method of the conjugated polymer of the invention of this application, a supporting electrolyte for imparting conductivity is added to the nematic liquid crystal which is a reaction field, in addition to the chiral dopant and the monomer. The supporting electrolyte may be any one as long as it does not inhibit the electropolymerization reaction and gives sufficient conductivity to the liquid crystal, and is appropriately selected from various ionic salts or the like generally used in the electrochemical reaction according to the applied voltage. it can.
Specifically, tetrabutylammonium perchlorate (TBAP) and lithium perchlorate are preferable.

In the electrolytic asymmetric polymerization of the conjugated polymer as described above, the applied voltage depends on the kind of the monomer to be polymerized (that is, the intended conjugated polymer), the liquid crystal reaction field used, and the electrode material. It may be appropriately selected according to the above, and is not particularly limited. For example, as shown in Examples described later, the electrolytic polymerization of pyrrole in (R) -PCH5O6-Binol / 6CB can be performed under a voltage of about 1.1 V.
Of course, the applied voltage is not limited to such an example.

Furthermore, in the electrolytic asymmetric polymerization of the conjugated polymer of the invention of this application, any electrode may be used, and it is not particularly limited. For example, gold, silver,
Examples thereof include metal electrodes such as platinum, carbon electrodes, and transparent glass electrodes such as indium oxide / tin (ITO). These are appropriately selected depending on the type of monomer (that is, the target conjugated polymer), the type of liquid crystal, or the amount of the target polymer.

The electrolytic asymmetric polymerization method of the conjugated polymer according to the invention of the present application as described above is applied to various conjugated polymer monomers. Monomers are selected from various compounds that give various polymers such as aliphatic conjugated systems, aromatic conjugated systems, heterocyclic conjugated systems, and heteroatom-containing conjugated systems.
You can select more than one type. If one type is selected, a homopolymer is obtained, and if two or more types are used, a mixed conjugated polymer is obtained. As the monomer, a compound having a low ionization potential is particularly preferable. Specifically, 3,4-ethylenedioxythiophene (EDOT) of the following formula (V), isothianaphthene (ITN) of the formula (VI), and formula (VI) Examples thereof include pyrrole of VII) or thiophene of formula (VIII).

[0024]

[Chemical 4]

Therefore, the invention of this application also provides an optically active conjugated polymer polymerized by the method described above. Such conjugated polymers include polyacetylene, poly (1,6-heptadiyne) and other aliphatic conjugated polymers, poly (paraphenylene) and polynaphthalene,
Aromatic conjugated polymers such as polyanthracene, heterocyclic conjugated polymers such as polypyrrole, polyfuran, and polythiophene, and heteroatom-containing conjugated polymers such as poly (paraphenylene sulfide), poly (paraphenylene oxide), and polyaniline Various things such as molecules are exemplified. Further, as the mixed conjugated polymer obtained by electrolytically polymerizing two or more kinds of monomers, poly (paraphenylene vinylene), poly (thiophenvinylene), poly (2,2'-
Thienylpyrrole) and the like.

It is known that the various conjugated polymers exemplified above generally do not contain asymmetric carbon and have a linear planar structure when synthesized by an isotropic or anisotropic reaction. Has been. However, the conjugated polymer synthesized by the electrolytic asymmetric polymerization method of the invention of this application reflects the helical structure of the chiral nematic liquid crystal, which is the reaction field, and becomes optically active. Therefore, it is possible to obtain an optically active conjugated polymer having a higher-order structure according to the chirality of the liquid crystal reaction field.

Hereinafter, the invention of this application will be described in more detail with reference to Examples. Needless to say, the invention of this application is not limited to the following examples.

[0028]

EXAMPLES <Preparation> Preparation of nematic liquid crystal (1) PCH506Br (1- (p- (trans-4-n-pentylcyclohexoyl)
Synthesis of (phenoxy) -6-bromohexane) 1.12 g (48.6 mmol) of sodium was dissolved in 200 ml of ethanol in a four-necked flask, and PCH500 10.0 g (40.
(5 mmol) ethanol solution was added dropwise, and the mixture was stirred at room temperature for 24 hours. In another four-necked flask, 1,6-dibromohexane 48.8 g
An ethanol solution of (200.0 mmol) was prepared, and the solution was transferred to an isobaric dropping funnel and added dropwise over time. After the dropping, the mixture was heated and refluxed for 12 hours, water was further added and the reaction was stopped by stirring.

The organic layer was extracted with chloroform, dried over calcium chloride, filtered and the solvent was distilled off under reduced pressure. Further, unreacted 1,6-dibromohexane was removed by distillation under reduced pressure, and then recrystallized with ethanol to obtain white plate crystals (1
1.54 g, yield 69.6%).

[0030]

[Chemical 5]

(2) (R) -PCH506-Binol ((R)-(+)-2,2'-d
i- (p- (trans-4-n-pentylcyclohexoyl) phenoxy-1-hexylo
xy) -1,1'-binaphthyl) (chemical formula (A)) in a four-necked flask (R) -BINOL (manufactured by Environmental Science Center Co., Ltd.) 1.5 g (5.24 mmol), the above PCH506Br 5.02 g ( Ten.
48 mmol), 7.24 g (52.4 mmol) of potassium carbonate, a small amount of potassium iodide, and 200 ml of acetone were added, and the mixture was heated to reflux. After 24 hours, the reaction solution was filtered and the solvent was distilled off under reduced pressure. The organic layer was extracted with chloroform, dried over magnesium sulfate, and separated and purified by silica gel chromatography (developing solvent: chloroform) to obtain a yellow oily product (3.92 g, yield 79.2%).

[0032]

[Chemical 6]

<Example 1> (1) Preparation of chiral nematic liquid crystal (R)-or (S) -PCH506-binol / n-heptylcyanobiphenyl (chemical formula (B), hereinafter 6CB) / pyrrole / TBAP .
When prepared with 0: 91.6: 7.2: 0.2 (mol%), (R)-
Thermotropic liquid crystals were obtained for both (S) and.

[0034]

[Chemical 7]

[0035]

[Chemical 8]

A polarization microscope photograph of this liquid crystal at 17 ° C. is shown in FIG. From FIG. 1, since the fingerprint structure was confirmed, it was confirmed that this liquid crystal was a chiral nematic liquid crystal (hereinafter N * -LC).

Next, from differential scanning calorimetry (DSC) and polarized light micrographs, N * -LC shows N * -LC characteristics between 15 and 27 ° C. under heating and 2 to 23 ° C. under cooling. It was confirmed. (2) Electrolytic asymmetric polymerization of pyrrole The above N * -LC was applied to a Teflon (registered trademark) sheet (thickness 0.1
2 mm) as a spacer for indium tin oxide (ITO)
After sandwiching between the electrodes and heating the reaction system to 30 ℃, 10 ℃ up to 17 ℃
Slowly cooled at a rate of / min. A good fingerprint structure was obtained. While maintaining the polymerization temperature of 17 ℃, 9.
When a voltage of 5 V / mm was applied for 24 hours, an insoluble and infusible dark black navy blue thin film (polypyrrole film, 6 μm thick) was formed on the ITO electrode surface while maintaining the N * -LC fingerprint structure.
Hereinafter, PPy *) was precipitated. The PPy * was washed with methanol, water, acetonitrile, and acetone in this order, then peeled from the ITO electrode surface in acetone, and transferred to a quartz plate. Further, PPy * was dried under reduced pressure on a quartz plate.

An electron microscope (SEM) photograph of (R) -PPy * is shown in FIG.
It was shown to. It was confirmed that (R) -PPy * retains the N * -LC fingerprint structure. Moreover, the spiral structure of polypyrrole was also confirmed (FIG. 3).

Left-handedness ((R) -PPy *), right-handedness ((S) -PPy *)
Was determined to depend on the chiral dopant (ie, (R)-and (S) -PCH506-binol) used to prepare the N * -LC system.

From this, it was confirmed that in the electrolytic asymmetric synthesis method of the invention of this application, the helical structure of the chiral nematic liquid crystal, which is the reaction field, is reflected in the obtained conjugated polymer.

Next, a circular dichroism spectrum (CD) was measured and shown in FIG. (R)-and (S) -PPy * show a cotton effect derived from the π → π * transition of the main chain from 352 to 555 nm, even though neither has a chiral substituent on the side chain. It was confirmed.

Further, as shown in FIG. 5, the cotton effect of (R)-and (S) -PCH506-binol added as a chiral dopant is observed only at 240 to 340 nm. It was suggested that the circular dichroism of-and (S) -PPy * is not directly derived from the chiral dopant.

From the above, it was revealed that in the obtained (R)-and (S) -PPy *, the main chain of polypyrrole itself has a helical structure.

On the longer wavelength side than 555 nm, (S) -PP
y * showed a positive cotton effect and (R) -PPy * showed a negative cotton effect. These CD bands are considered to originate from the bipolaron band (> 600 nm) in the absorption spectrum. <Comparative Example 1> In the same manner as in Example 2, electrolytic asymmetric polymerization was carried out.
It was performed under isotropic conditions at 30 ° C. However, the obtained liquid crystal did not show a helical structure, and the electron micrograph of the thin film (PPy) obtained on the ITO electrode by electrolytic polymerization also showed a random spherical structure. In addition, although a characteristic absorption spectrum (UV-visible absorption spectrum) was observed at 290, 457 nm and> 600 nm, the cotton effect was not shown, indicating that PPy has no optical activity. confirmed. Comparative Example 2 A nematic liquid crystal containing no chiral dopant (6CB / pyrrole / TBA) was prepared in the same manner as in Example 2.
P) was prepared and electrolytic polymerization was carried out using the obtained liquid crystal (N-LC) as a reaction field. The resulting thin film (PPy) showed a Schlieren-like uneven structure. This suggested that PPy was polymerizing along with the nematic phase. Moreover, since the CD spectrum of PPy did not show the Cotton effect, it was confirmed that PPy has no optical activity.

[0045]

As described in detail above, according to the invention of this application, the optical activity of the liquid crystal reaction field and the helical structure can be reflected in the conjugated polymer. Further, the invention of this application provides an electrolytic asymmetric polymerization method capable of polymerizing an optically active conjugated polymer without a complicated isomer separation operation. Such a method can be used for various electropolymerizable polymers (eg, polyaniline, polythiophene, PEDOT; pol
It can also be applied to asymmetric polymerization of y (3,4-ethylemnedioxythiophene). Further, the conjugated polymer obtained by such a method is highly useful as a new conductive material because it has optical activity. Furthermore, the liquid crystal reaction field of the invention of this application is expected to be applicable to a wide variety of organic syntheses as various asymmetric synthesis reaction fields.

[Brief description of drawings]

FIG. 1 is a drawing showing a polarization microscope photograph at 17 ° C. of a chiral nematic liquid crystal obtained in an example of the invention of this application.

FIG. 2 is a view showing an electron micrograph of (R) -PPy * polymerized by the method of the present invention in an example of the invention of this application.

FIG. 3 is a view showing a helical structure of (R) -PPy * polymerized by the method of the present invention in an example of the invention of this application.

FIG. 4 is a diagram showing circular dichroism spectra of (R)-and (S) -PPy * polymerized by the method of the present invention in Examples of the invention of this application.

FIG. 5 is a diagram showing circular dichroism spectra of (R)-and (S) -PCH506-binol added as chiral dopants in the examples of the invention of this application.

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[Procedure amendment]

[Submission date] March 4, 2003 (2003.3.4)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

[0045]

As described in detail above, according to the invention of this application, the optical activity of the liquid crystal reaction field and the helical structure can be reflected in the conjugated polymer. Further, the invention of this application provides an electrolytic asymmetric polymerization method capable of polymerizing an optically active conjugated polymer without a complicated isomer separation operation. Such a method can be used for various electropolymerizable polymers (eg, polyaniline, polythiophene, PEDOT; pol
It can also be applied to asymmetric polymerization of y (3,4-ethyl en edioxythiophene). Further, the conjugated polymer obtained by such a method is highly useful as a new conductive material because it has optical activity. Furthermore, the liquid crystal reaction field of the invention of this application is expected to be applicable to a wide variety of organic syntheses as various asymmetric synthesis reaction fields.

Claims (6)

[Claims] 1. A method for polymerizing an optically active conjugated polymer, which comprises adding at least a chiral dopant, a monomer and a supporting electrolyte to a nematic liquid crystal, and applying a voltage, to electrolyze the conjugated polymer. Asymmetric polymerization method. 2. The method of electrolytic asymmetric polymerization of a conjugated polymer according to claim 1, wherein the nematic liquid crystal is selected from the group consisting of an alkylphenylcyclohexyl type, an alkylcyanobiphenyl type, and an alkoxycyanobiphenyl type. 3. The method of electrolytic asymmetric polymerization of a conjugated polymer according to claim 1, wherein the chiral dopant is a chiral liquid crystal compound. 4. The conjugated polymer according to claim 1, wherein the monomer is one or more selected from the group consisting of 3,4-ethylenedioxythiophene, isothianaphthene, pyrrole, and thiophene. Electrolytic asymmetric polymerization method of. 5. The method of electrolytic asymmetric polymerization of a conjugated polymer according to claim 1, wherein the supporting electrolyte is selected from tetrabutylammonium perchlorate or lithium perchlorate. 6. An optically active conjugated polymer obtained by the polymerization method according to any one of claims 1 to 5.