JPH0433918A - Electrochromic material produced by electrolytic polymenrization - Google Patents

Abstract

PURPOSE:To provide the subject material produced by the electrolytic oxidation polymerization of tri(thienyl) triphenylamine as a raw monomer, having excellent oxidation-reduction stability and durability and capable of giving an EC thin film having large area. CONSTITUTION:The objective material is produced by using 4, 4',4''-tri(2-thienyl) triphenylamine of formula as a raw monomer and subjecting the monomer to electrolytic oxidation polymerization.

Description

Detailed Description of the Invention (Industrial Application Field) This invention provides 4,4',4'-tri(2-cheni) in which a thiophene moiety is directly bonded to triphenylamine represented by
The present invention relates to electrochromic (EC) materials produced by electrolytic oxidative polymerization of triphenylamine.

(Prior Art) Various organic and inorganic materials have been proposed as EC materials, but they have not been put into practical use because of problems with drive stability and durability. Among EC materials, so-called conductive polymers are attractive because of their wide range of material variations, good processability, wide variety of colors, possibility of multicolorization, and good responsiveness. However, durability was still an issue. The applicant has previously discovered polytriphenylamines, which have fairly high conductivity (
A series of conductive polymers with particularly excellent drive stability and durability (up to the order of is-cm-' by doping) were developed and disclosed in JP-A-61-28524.

A polytriphenylamine ECI film is prepared as follows. A polymer such as poly(4,4'-)liphenylamine) is dissolved in a solvent such as chloroform, and a film is formed on a transparent conductive glass such as ITO (indium-doped tin oxide) using a spin-coding method, and then heated. It is doped with iodine and crosslinked to make it insoluble and form an electrochromic thin film. The electrochromic thin film created in this way has excellent redox stability, driving stability, and durability.
As mentioned above, it has good moldability and is extremely practical.

(Problem to be solved by the invention) However, polytriphenylamines such as the previously proposed poly(4,4'-triphenylamine) are not practical when constructing large-area EC elements. It is difficult to create an EC3 film that is sufficiently uniform and free of unevenness.
Further, when constructing an EC element including a complicated pattern such as a character, there is a problem in that there is no simple and suitable processing method for accurately removing unnecessary portions after film formation. Therefore, we investigated the production of polytriphenylamine ECI membranes by electrolytic polymerization, and found that if it can be produced by electrolytic polymerization,
Although the above problem can be solved, as shown in Comparative Example 1 below, the stability of the dimer of triphenylamine is adversely affected, and the direct electrolytic polymerization method of triphenylamine has an E.
It was found that a C thin film could not be obtained.

(Means for Solving the Problems) Therefore, the present inventors considered using an electrolytic polymerization method to somehow obtain a conductive polymer thin film containing triphenylamine units, which are extremely excellent reactive sites, in the main chain. I've been doing it. As a result, we found that it was possible to solve the problem by synthesizing a raw material with good electrolytic polymerizability and stability against Grignard reagents, combining thiophene and triphenylamine, and electropolymerizing it. I found out.

This invention was achieved based on such knowledge, and uses 4, 4', 4'' tri(2-thienyl)triphenylamine, in which a thiophene moiety is directly bonded to triphenylamine represented by the following formula, as a raw material monomer. The present invention relates to an EC material containing a triphenyl structural unit produced by electrolytically oxidatively polymerizing the same.

(Examples) The present invention will be specifically explained below using Examples and Comparative Examples.

This 1 stone 11 Direct electrolytic polymerization of triphenylamine.

It has been shown by Yoshino et al. that conductive polymer thin films can be produced by electrolytic oxidative polymerization of condensed hydrocarbons such as benzene (J, Elketroanal, Chem.

195 (1985) 203. and J. Chem.
,Soc,Chem,Commum,.

(1986) 550. ), electrolytic oxidative polymerization of triphenylamine was attempted using this method as follows.

The electrolyte was 0.3M triphenylamine, 0.3M triphenylamine, and 0.3M triphenylamine. I
MCuCl z, 0. A solution of I M LiAsF6 (nitrobenzene) was used. Nesa glass was used as the working electrode and platinum wire was used as the counter electrode, and 10 V was applied between the working electrode and the counter electrode to conduct electrolysis. When benzene was added instead of triphenylamine, a black film was formed, but in this case, the solution turned reddish-brown, but a thin film could not be formed on Nesaglass no matter how much electrolysis was carried out. This is probably because triphenylamine undergoes oxidative polymerization to form a dimer, but the cation is stable, and even if the sication is oxidized, it is stable to some extent, so electrolytic polymerization does not proceed beyond the dimer, so a film cannot be formed. It will be done.

IJJ Tsujigami The monomers used as raw materials for electrolytic polymerization in benzonitrile are new compounds, and for this purpose, the literature (Makromol, Chem, vol.
1891755, (1988)), it was synthesized as follows. Add 4.0 g (0,167 mol) of metallic magnesium for Grignard reagent into a 300 d 3-tube round bottom flask, put a magnetic rotator in it, and after vacuum degassing, diethyl ether dehydrated using metallic sodium is added to the flask. 110d was added by vacuum distillation, the flask was equipped with a condenser, and 25g (0,1
A Grignard reagent was prepared by dropping 53 mol) of 2-bromothiophene. In another 300 d 3 tube round bottom flask add 6 g (0,0125 mol) of 4,4'4''-
Tribromotriphenylamine (synthesized by bromination of triphenylamine) and a catalytic amount (0.15 g) of dichloro(1,3-(diphenylphosphino)propanknickel(II)) were added to transform the magnetic rotor. After vacuum degassing, about 100 ml of dry diethyl ether was added by vacuum distillation, and after cooling in an ice bath, about 80 d (large excess) of the Grignard reagent solution was added using a syringe under nitrogen. Synthesis was carried out by refluxing the above solution for 43 hours.After the reaction was completed, the mixture was cooled in an ice bath and a 2 mol/liter aqueous solution of hydrochloric acid was added to about 70% of the solution while watching to prevent boiling.
d and extracted with a total of 250 d of diethyl ether.

The resulting brown-orange ether phase was washed with saturated aqueous sodium carbonate solution, dried over calcium chloride overnight, and the ether phase was filtered and evaporated to further remove the by-product thiophene. Vacuum bowing was performed using a rotary pump. The crude product was separated and purified by column chromatography (silica gel/benzene:hexane (volume ratio 1:4)) and further recrystallized from ethanol to obtain the target raw material monomer. The raw materials were pale orange crystals. The melting point was 1857°C. The FT-IR results shown later were also consistent. The results of elemental analysis were as follows, and it was confirmed to be the target substance.

Theoretical values: Carbon: 73.3%, Hydrogen: 4.28%, Nitrogen: 2.85%, Sulfur: 19.6%.

Experimental values: Carbon: 73.2%, Hydrogen: 4.26%, Nitrogen: 2.61%, Sulfur: 19.9%.

Electrolytic polymerization of the obtained monomer was carried out under the following conditions.

As a solvent, benzonitrile that was dehydrated with calcium hydride and then vacuum distilled was used, and as a supporting electrolyte, 0
．． Using 1 mol/liter of n-tetrabutylammonium hexafluorophosphate, a silver/silver chloride electrode in propylene carbonate was used as the reference electrode.
They were separated by two glass filters. The concentration of the raw material monomer was 5 mmol/liter. IT is used as a working electrode.
O glass (surface resistance 10 ohms/mouth) was used.

A platinum wire (about 2 cm in length) with a diameter of 0.5 mm was also used as a working electrode in order to more accurately understand the redox properties of the resulting thin film. A platinum wire was used as the counter electrode.

Electrolytic polymerization was carried out in a glove box with a nitrogen atmosphere using a three-chamber electrolytic cell. A working electrode was placed in the central chamber of the cell, a counter electrode was placed in one chamber with a glass filter in between, and a reference electrode was placed in the other chamber with a glass filter in between.

FIG. 1 shows a cyclic portammogram of the above solution using a platinum electrode. When the potential sweep is limited to a range from 0 to 1.1 square meters, a very stable one-electron reversible wave is exhibited and electrolytic polymerization does not occur. However, when the potential sweep was performed up to about 1.5 ■, the amount of reaction electricity increased rapidly as the number of sweeps increased, and the platinum electrode became colored, indicating that an electrolytically polymerized film was formed very easily. A series of results on well-known polythiophenes (e.g. G., Tourillon
in T,A.

Skothheim, (Ed,), f(andboo
k of Conducting PoIymers
vol, 1+ Dekker New York
, 1986. p, 293. ), the proton on the carbon at the 2-15-position next to the sulfur of the thiophene skeleton is removed by oxidation, and the carbons bond to each other to form a polymer. In this case, as shown in Figure 2, since one molecule has three binding sites, it is thought that the polymer grows in a network shape as a result.

FIGS. 2a and 2b show FT-IR spectra of the raw materials and the obtained electrolytically polymerized membrane.

The spectrum of the electropolymerized film is obtained by scraping the film on ITO.
Measured using the Br method. 12701310, 148 unique to triphenylamine moieties in both monomers and polymers
Strong absorption near 0.159OCT11-' is seen, indicating that a triphenylamine moiety is included.

In the polymer, absorption appears near 790 cm-', which is the absorption observed in 2,5-disubstituted thiophene, and the absorption of 6901-1, a monomer containing 2-substituted thiophene, almost disappears. Therefore, it is considered that the polymer grows in the form of a network due to the bonds between the 5-positions of thiophene.

Electrochromic properties of the resulting thin films were performed in propylene carbonate, a more practical solvent. 1
．． The cyclic portammogram of the polymer on ■T○ in a propylene carbonate solution containing 0 mol/liter of lithium perchlorate is shown in FIG. Although redox was repeated over 100 times in the oxidation wave, no change in the waveform was observed and it was very stable. An electrochemical cell for measuring absorption spectra was constructed, and FIG. 4 shows changes in visible-near infrared absorption spectra due to oxidation. With the oxidation in the second wave, the color of the thin film reversibly changed visually from a slightly orange-yellow to black.

1 plate L The amount of electricity injected and the polymer produced when electrolytically polymerized on the rro electrode by constant potential electrolysis at 1.6 V in the same manner as in Example 1 except that the concentration of the sample was changed to 3 mmol/liter. The relationship between the amount of electricity in the reaction of the membrane (the efficiency of the amount of electricity in electrolytic polymerization) was investigated. As the amount of reaction electricity of the polymer, the second wave (up to 0.95 V), which can be approximated to the reaction of the triphenylamine site in the polymer, was used. The results are shown in Figure 5.

As can be seen from the mechanism of electrolytic polymerization shown in the following formula focusing only on the electrical quantity balance and material balance, it is necessary to remove a total of five electrons for one polymerization to proceed. Therefore, the results shown in FIG. 5 show that the electrical efficiency of polymerization is practically 100%, and it can be seen that almost all of the reacted hexamer contributes to the growth of the film without emitting any solution. The reason why the monomer can be polymerized and precipitated very efficiently even though it has already been oxidized one step and is charged to 1° before polymerization is because the monomer is trifunctional. This monomer therefore suggests further possibilities.

The solvent and supporting electrolyte used in the electropolymerization used in this invention are not limited to nitrile solvents and n-tetrabutylammonium hexafluorophosphate, but can be used as a non-aqueous electrolyte as long as it is not oxidatively decomposed at the electropolymerization potential. Solvents and electrolytes used in can be used. Similarly, the driving solvent for the produced electrochromic thin film is not limited to a propylene carbonate solution of lithium perchlorate.

(Effects of the Invention) As explained above, according to the present invention, an E containing a triphenylamine moiety has good redox stability, is excellent in durability, can be made into a large area, and can be easily formed into any shape.
A Cff film can be obtained.

[Brief explanation of drawings]

Figure 1 shows 4.4',4'-tri(2-thienyl)
Cyclic portamogram diagram of tophenylamine in base nitrile solution, Figure 2a is FT-IR of raw material monomer in Example 1
Spectral diagram, Figure 2 is an FT-IR spectrum diagram of the electropolymerized membrane obtained in Example 1, Figure 3 is a cyclic horta modalum diagram of the electrolyzed membrane obtained in Example 1, Figure 4 5 is a diagram showing changes in the absorption spectrum due to oxidation of the electrolytically polymerized membrane obtained in Example 1, and FIG. 5 is a diagram showing the electrical quantity efficiency of electrolytic polymerization in Example 2. Figure 5 Q (Den N Kogo) mc

Claims (1)

[Claims] 1. 4,4',4''-tri(2-thienyl)triphenylamine represented by the following formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼...(I) as a raw material monomer An electrochromic material produced by electrolytic oxidative polymerization.