JP2855206B2 - Porous selective permeable membrane made of polyaniline and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a porous selective permeable membrane made of polyaniline and a method for producing the same.

Prior artA method for producing a conductive polyaniline, which is obtained by chemically oxidizing and polymerizing aniline with a chemical oxidizing agent and containing an electrolyte ion as a dopant and having a conductivity of 10 ^-6 S / cm or more, is already known. Furthermore, in the production of polyaniline by such chemical oxidative polymerization, the standard electrode potential determined as the electromotive force in the reduction half-cell reaction based on the standard hydrogen electrode is
An oxidizing agent having a voltage of 0.6 V or more is particularly preferably used,
It is already described in JP-A-61-258831.

However, the conductive polyaniline obtained by the above method is insoluble and infusible.
As in the case of solvent-soluble resins such as polysulfone, polyacrylonitrile, and polyimide, it is not possible to form a porous film by a wet method or a uniform film by a casting method, and develop applications of conductive polyaniline. This is a major obstacle.

JP-A-60-235831 and J. Polymer Sci., Polymer
As described in Chem. Ed., 26 , 1531 (1988),
According to the electrolytic oxidation polymerization of aniline, a film of a conductive organic polymer can be formed on the electrode, but it is difficult to obtain a large-area film because the film forming surface is limited to the electrode surface. In addition, production costs are high due to electrolytic oxidation.

Therefore, conventionally, an intermediate soluble in an organic solvent was produced,
Various methods have been proposed for converting the intermediate into a conductive polymer by physical or chemical means after the solution is formed into a film by a casting method. However, according to this method, a treatment at a high temperature is required, or the conversion of the intermediate to the conductive polymer does not always proceed as theoretically. However, it is not practical as a method for producing a conductive organic polymer film.

On the other hand, in the field of chemical oxidative polymerization of aniline, recently, about 1/4 mole of ammonium peroxodisulfate is used as an oxidizing agent for aniline to chemically oxidize and polymerize aniline to obtain organic solvent-soluble polyaniline. Is reported to be possible (AGMacDiarmid e
t al., Synthetic Metals, 21 , 21 (1987); AGMacDiarmi
d et al., L. Alcacer (ed.), Conducting Polymers, 105
-120 (D. Reidel Publishing Co., 1987). However, since this polymer is soluble not only in N-methyl-2-pyrrolidone and dimethyl sulfoxide but also in 80% acetic acid and 60% formic acid aqueous solution, its molecular weight is low. It is also described that a self-supporting film can be obtained from a solution of a polymer such as N-methyl-2-pyrrolidone or dimethyl sulfoxide. Furthermore, it is described that a conductive polymer film doped with acetic acid can be obtained from an acetic acid solution, and this film is de-doped with ammonia. However, the undoped film has low strength due to the low molecular weight of polyaniline, and is easily broken by bending, so that it cannot be put to practical use.

It is also known that aniline can be oxidized with ammonium peroxodisulfate to obtain polyaniline soluble in tetrahydrofuran (J. Tang, Synthet).
ic Metals, 24 , 231 (1988). However, this polymer is also considered to have a low molecular weight from the viewpoint of dissolving in tetrahydrofuran.

As described above, although some progress has been made recently in film formation of conductive polyaniline, a porous selectively permeable membrane made of conductive polyaniline has not yet been known.

DISCLOSURE OF THE INVENTION The present inventors have made intensive studies to obtain a high molecular weight organic polymer which is soluble in an organic solvent by chemical oxidative polymerization of aniline. Although it has a high molecular weight, it is soluble in various organic solvents in the undoped state, and a porous membrane can be easily obtained from the solution by a wet method. The present inventors have found that by doping, it is possible to obtain a porous selective permeable membrane made of a high-molecular-weight, high-conductivity polyaniline insoluble in an organic solvent, leading to the present invention.

Accordingly, an object of the present invention is to provide a porous selective permeable membrane made of polyaniline and a method for producing the same.

Means for Solving the Problems The porous selective permeable membrane according to the present invention has a general formula (In the formula, m and n each represent a mole fraction of a quinone diimine structural unit and a phenylenediamine structural unit in the repeating unit, and are 0 <m <1, 0 <n <1, and m + n = 1). It is characterized by being composed of undoped polyaniline having a repeating unit and having an intrinsic viscosity [η] of 0.40 dl / g or more measured at 30 ° C. in N-methylpyrrolidone in the undoped state.

According to the present invention, the porous selective permeable membrane made of such undoped polyaniline has an acid dissociation constant pKa value of 3.0.
A standard electrode potential determined as an electromotive force in a reduction half-cell reaction based on a standard hydrogen electrode while maintaining the temperature at 5 ° C. or lower in aniline in a solvent in the presence of An aqueous solution of the oxidizing agent is added in an amount equivalent to one mole of the oxidizing agent divided by the number of electrons required to reduce one molecule of the oxidizing agent per mole of aniline, and two or more equivalents are added. Polyaniline doped with the above protonic acid was prepared, and then the polyaniline was dedoped with a basic substance, and the intrinsic viscosity [η] measured at 30 ° C. in N-methylpyrrolidone was 0.40 dl / g.
With the above polyaniline, then, dissolve this polyaniline in an organic solvent, apply it on a suitable supporting substrate, then evaporate a part of the organic solvent, and then have miscibility with the organic solvent. By contacting with a coagulating solvent that does not dissolve the polyaniline, and removing the solvent to make it porous.

Further, the conductive porous selective permeable membrane according to the present invention has a general formula (In the formula, m and n each represent a mole fraction of a quinone diimine structural unit and a phenylenediamine structural unit in the repeating unit, and are 0 <m <1, 0 <n <1, and m + n = 1). Having a repeating unit, polyaniline having an intrinsic viscosity [η] of 0.40 dl / g or more measured at 30 ° C. in N-methylpyrrolidone in the undoped state has a pKa value of 4.0.
It is characterized by being made of a doped conductive polyaniline doped with the following protonic acid.

According to the present invention, a porous selectively permeable membrane comprising such a doped polyaniline is converted into aniline in a solvent in the presence of a protonic acid having an acid dissociation constant pKa of 3.0 or less,
While maintaining the temperature at 5 ° C. or lower, an aqueous solution of an oxidizing agent having a standard electrode potential of 0.6 V or more, which is defined as an electromotive force in a reduction half-cell reaction based on a standard hydrogen electrode, was added to the oxidizing agent per mole of aniline. Is added to the polyaniline doped with the above-mentioned protonic acid by adding 1 mol of the above-mentioned compound to an equivalent defined as the amount obtained by dividing the number of electrons required to reduce one molecule of the oxidizing agent, and then adding the polyaniline. To a polyaniline having an intrinsic viscosity [η] of 0.40 dl / g or more measured at 30 ° C. in N-methylpyrrolidone, and then dissolving the polyaniline in an organic solvent, After being applied on a suitable supporting substrate, a part of the organic solvent is evaporated, and thereafter, a contact is made with a coagulating solvent which is miscible with the organic solvent but does not dissolve the polyaniline, and is removed. It can be obtained by doping the porous membrane with a solvent to make it porous and then using a protonic acid having a pKa value of 4.0 or less.

First, the production of an organic solvent-insoluble polyaniline doped with a protonic acid and the production of an organic solvent-soluble polyaniline by dedoping will be described.

When oxidizing and polymerizing aniline in the presence of a protonic acid to produce polyaniline doped with the above protonic acid, the oxidizing agent includes manganese dioxide, ammonium peroxodisulfate, hydrogen peroxide, a ferric salt, Iodate and the like are particularly preferably used. Among them, for example, ammonium peroxodisulfate and manganese dioxide usually have an amount in the range of 1 to 1.25 mol per 1 mol of aniline since two electrons per molecule are involved in the oxidation reaction. Is used.

The above-mentioned protonic acid is not particularly limited as long as the acid dissociation constant pKa value is 3.0 or less.For example, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hydrofluoric acid, hydrofluoric acid, hydrofluoric acid, etc. Inorganic acids such as hydrogen acid and hydroiodic acid; aromatic sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid; alkanesulfonic acids such as methanesulfonic acid and ethanesulfonic acid; phenols such as picric acid; Examples thereof include aromatic carboxylic acids such as nitrobenzoic acid, and aliphatic carboxylic acids such as dichloroacetic acid. Also, polymeric acids can be used. Examples of such a polymer acid include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, and polyvinyl sulfate.

The amount of protonic acid used depends on the mode of reaction of the oxidizing agent used. For example, in the case of manganese dioxide, the oxidation reaction is represented by MnO ₂ + 4H ⁺ + 2e ⁻ → Mn ²⁺ + 2H ₂ O.
It is necessary to use a protonic acid capable of supplying a double molar amount of protons. Also, in the case of hydrogen peroxide, the oxidation reaction is represented by H ₂ O ₂ + 2H ⁺ + 2e ⁻ → 2H ₂ O. Therefore, a proton acid capable of supplying at least twice the amount of protons of hydrogen peroxide to be used is used. There is a need. On the other hand, in the case of ammonium peroxodisulfate,
Since the oxidation reaction is represented by S ₂ O ₈ ²⁻ + 2e ⁻ → 2SO ₄ ²⁻ , it is not particularly necessary to use a protonic acid. However, in the present invention, even when ammonium peroxodisulfate is used as the oxidizing agent, it is preferable to use an equimolar amount of the protonic acid with the oxidizing agent.

As a solvent in the oxidative polymerization of aniline, a solvent that dissolves aniline, a protonic acid and an oxidizing agent and that is not oxidized by the oxidizing agent is used. Water is most preferably used, however, if necessary, alcohols such as methanol and ethanol, nitriles such as acetonitrile, N-methyl-2-pyrrolidone, polar solvents such as dimethyl sulfoxide, ethers such as tetrahydrofuran, Organic acids such as acetic acid can also be used. Also, a mixed solvent of these organic solvents and water can be used.

In the process of obtaining a solvent-soluble aniphosphorylated polymer, it is important that the temperature of the reaction mixture is always kept at 5 ° C. or lower during the reaction, especially during the addition of the oxidizing agent solution to the aniline solution. Therefore, the oxidant solution should be added slowly to the aniline so that the temperature of the reaction mixture does not exceed 5 ° C. When the oxidizing agent is added rapidly, the temperature of the reaction mixture increases due to external cooling to produce a low-molecular-weight polymer, or a solvent-insoluble oxidizing polymer even after dedoping described later. Is generated.

In particular, in the present invention, it is preferable to keep the reaction temperature at 0 ° C. or lower.
-Methyl-2-pyrrolidone at 30 ° C.
the same. ) A high molecular weight solvent-soluble aniline oxidized polymer having an intrinsic viscosity [η] of 1.0 dl / g or more can be obtained.

Thus, an oxidized polymer of aniline doped with the used protonic acid, that is, polyaniline can be obtained. In the dope state, this polyaniline does not dissolve in an organic solvent as described later because it forms a salt with a protonic acid. It is well known that salts of high molecular weight amines are generally poorly soluble in organic solvents. However, according to the present invention, polyaniline which is soluble in an organic solvent can be obtained by dedoping the organic solvent-insoluble polyaniline.

Since the dedoping of polyaniline doped with such a protonic acid is a kind of neutralization reaction, it is not particularly limited as long as it is a basic substance capable of neutralizing the protonic acid as a dopant. Preferably, metal hydroxides such as aqueous ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, and calcium hydroxide are used. In the dedoping, after the oxidative polymerization of aniline, a basic substance may be directly added to the reaction mixture, or the polymer may be once isolated and then acted on by the basic substance.

Doped polyaniline obtained by oxidative polymerization of aniline usually has an electrical conductivity of 10 ^-6 S / cm or more,
It has a blackish green color, but after undoping, is purple or purple-tinted copper. This discoloration is because the amine nitrogen of the salt structure in the polymer was changed to a free amine. The conductivity is usually on the order of 10 ^-10 S / cm.

The undoped polyaniline thus obtained has a high molecular weight and is soluble in various organic solvents. Such organic solvents include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, 1,3-dimethyl-2.
-Aprotic polar organic solvents such as imidazolidinone and sulfolane.

The solubility of the undoped polyaniline in such an organic solvent depends on the average molecular weight of the polyaniline and the solvent, but 1 to 100% of the polyaniline can be dissolved to obtain a 1 to 30% by weight solution. In particular, undoped polyaniline exhibits high solubility in N-methyl-2-pyrrolidone,
Usually, 20 to 100% of it is dissolved to obtain a 3 to 30% by weight solution. However, it does not dissolve in tetrahydrofuran, 80% acetic acid aqueous solution, 60% formic acid aqueous solution, acetonitrile and the like.

Next, the production of a porous selective permeable membrane using such a solvent-soluble polyaniline will be described.

According to the present invention, first, such a solvent-soluble polyaniline is dissolved in the above-mentioned organic solvent to form a film-forming solution, and the film-forming solution is applied on an appropriate supporting substrate, and then preferably heated. Then, a part of the organic solvent is evaporated. Thereafter, the organic solvent is brought into contact with a coagulating solvent which is miscible with the organic solvent but does not dissolve the polyaniline, and the solvent is removed to obtain a porous film. As the organic solvent for the film forming solution, the aprotic organic solvent as described above is used in order to keep the polyaniline in the undoped state, and in particular, N-methyl-2-pyrrolidone has a poor solubility in polyaniline. Since it is excellent, it is preferably used in the present invention.

Thus, in general, a method for producing a porous membrane from a membrane-forming solution containing a polymer is already well known as a wet method, and an ultrafiltration membrane or a reverse osmosis membrane is produced by such a method. . Such a film is a so-called anisotropic porous film in which a so-called dense skin layer is integrally supported by a porous layer. The porous layer may include a finger-like structure having a cavity. The porous film obtained from the solvent-soluble polyaniline obtained as described above is also an anisotropic film having such a structure.

In the present invention, in order to obtain a tough and highly flexible porous film, it is desirable to use the above-mentioned solvent-soluble polyaniline having an intrinsic viscosity [η] of 0.40 or more.

The concentration of polyaniline in the film forming solution is usually 1 to
It is in the range of 30% by weight, preferably 5-20% by weight. When the polyaniline concentration in the membrane-forming solution is too small, the obtained selectively permeable membrane becomes inferior in selective separation. On the other hand, when the polyaniline concentration is too large, the permeation speed of the obtained selectively permeable membrane becomes small. Therefore, it is not preferable in practical use. Although related to the polyaniline concentration, the film-forming solution preferably has a viscosity of 10 to 1000 poise when applied to a supporting substrate.

In the present invention, various additives may be added to the membrane forming solution in order to adjust the water permeation rate of the obtained selectively permeable membrane. Such additives need to be dissolved in the film forming solution, and for example, alkali metal salts and alkaline earth metal salts are preferably used. Specific examples include, for example, lithium nitrate, potassium nitrate, lithium bromide, and the like, but are not limited thereto. Such an inorganic additive is generally used in a range of 200 parts by weight or less per 100 parts by weight of polyaniline. When the additive is used excessively, the uniformity of the membrane forming solution tends to be impaired, and it becomes difficult to obtain a uniform selective permeable membrane.

In addition, polyhydric alcohols, alkylene glycols, polyalkylene glycols, ketones, esters, ethers, amides, and sulfoxides can also be used as additives. Such additives also need to be dissolved in the film forming solution. Specific examples include, for example, glycerin, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butanediol,
Examples include, but are not limited to, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, dioxane, dimethylformamide, dimethyl sulfoxide, and the like. These organic additives are generally used in a range of 1000 parts by weight or less per 100 parts by weight of polyaniline. If necessary, the inorganic additive and the organic additive can be used in combination.

The support substrate to which the film forming solution is applied is not particularly limited. When using a plate member or a tube member having a smooth surface made of a material exemplified by glass, stainless steel, aluminum, polyethylene, polypropylene, etc., since polyaniline solidifies, it is easily separated from these substrates, Sheet and tubular porous membranes can be obtained.

Further, as the supporting base material, a woven or nonwoven sheet member or a tube member made of organic fibers such as polyester fibers and acrylic fibers, and inorganic fibers such as glass fibers and carbon fibers can be used. By applying a film-forming solution on such a supporting substrate and forming a film, a composite film integrated with these substrates can be obtained.

The coating thickness of the membrane-forming solution on the supporting substrate is different depending on the use of the obtained selectively permeable membrane and the type of the substrate, but usually, the thickness of the obtained porous membrane is 10 to 700 μm, Preferably, it is applied so as to have a thickness of 50 to 200 μm. When the film thickness is too thin, the obtained selectively permeable membrane becomes inferior in mechanical strength. On the other hand, when it is too thick, the selective separation property is increased, but the water permeation rate is reduced, and both are inferior in practical use. It will be.

As described above, it is preferable to apply the film-forming solution to a thin layer on the supporting substrate and then evaporate a part of the organic solvent from this layer to promote the formation of the skin layer. The conditions for the evaporation of the solvent are:
The component composition of the film-forming solution, or is appropriately selected depending on the application and use conditions of the obtained selectively permeable membrane, but a temperature lower than the boiling point of the solvent, for example, when the solvent is N-methyl-2-pyrrolidone If so, the temperature is in the range of 0 to 200 ° C., and the time for evaporation is usually 30 minutes or less.

Next, the substrate coated with the film forming solution is immersed in a coagulation solvent to remove the polyaniline and coagulate to form a porous film. The coagulating solvent does not dissolve the polyaniline, but has good compatibility with the solvent of the film forming solution, preferably, it is compatible with an arbitrary ratio, and further, it is necessary to dissolve the additives described above. Typically, water is used. Other examples of the coagulation solvent include a mixed solvent of water and an organic solvent compatible with water, and specific examples of such an organic solvent include, for example, acetone, glycerin, and methanol. . The amount of these organic solvents in the coagulating solvent is usually 50% by weight or less, but if necessary, such organic solvents can be used alone as the coagulating solvent.

The temperature at which the polyaniline is brought into contact with the coagulating solvent to form the polyaniline into a porous film is generally lower than the boiling point of the coagulating solvent used. When water is used as the coagulating solvent, the temperature is usually in the range of 0 to 80 ° C, preferably 0 to 50 ° C. The time required for coagulation is not particularly limited, but may range from 1 minute to 20 hours.

Thus, a porous selective permeable membrane comprising polyaniline according to the present invention can be obtained.

Further, the porous selective permeable membrane made of conductive polyaniline according to the present invention can be obtained by doping the porous selective permeable membrane made of polyaniline described above with a protonic acid. That is, according to the present invention, the polyaniline obtained as described above is then doped with a protonic acid having a pKa value of 4.0 or less by doping the porous selective permeable membrane made of polyaniline, whereby the polyaniline becomes conductive. To obtain the conductive porous selective permeable membrane according to the present invention.

Such doping agents include, for example, hydrochloric acid, sulfuric acid,
Inorganic acids such as nitric acid, perchloric acid, hydrofluoric acid, hydrofluoric acid, hydrofluoric acid, hydroiodic acid, benzenesulfonic acid, aromatic sulfonic acid such as p-toluenesulfonic acid, methanesulfonic acid, Examples include aliphatic sulfonic acids such as ethanesulfonic acid, phenols such as picric acid, aromatic carboxylic acids such as m-nitrobenzoic acid, and organic acids such as aliphatic carboxylic acids such as dichloroacetic acid and malonic acid.

The doping of the polyaniline porous film may be usually carried out by immersing the film in a solution containing the above-mentioned doping agent and then washing the film.

The doped polyaniline, which has been provided with conductivity, like the polyaniline prepared in the presence of a protonic acid, is doped with a protonic acid. Does not dissolve.

The soluble aniphosphorylated polymer according to the present invention, elemental analysis, infrared absorption spectrum, ESR spectrum, thermogravimetric analysis, solubility in solvents, from visible to near infrared absorption spectrum, (In the formula, m and n each represent a mole fraction of a quinone diimine structural unit and a phenylenediamine structural unit in the repeating unit, and are 0 <m <1, 0 <n <1, and m + n = 1). It is a polymer having a repeating unit.

Thus, the oxidized polymer of aniline according to the present invention,
Since it has a quinone diimine structural unit and a phenylenediamine structural unit as a repeating unit, it has conductivity only by an acid-base reaction without a redox reaction when doped with a protonic acid. It is explained as. This conductive mechanism is based on AGMacDiarmid et al. (AGMacDiarmid et al., J. Chem. So
c., Chem. Commun., 1987 , 1784), by doping with a protonic acid, as shown below, the quinone diimine structure is protonated, which takes on the semiquinone cation radical structure and has conductivity. is there. Such a state is called a polaron state.

The conductivity of the conductive porous selectively permeable membrane made of polyaniline obtained by doping depends on the pKa value of the protonic acid used. For polyaniline doping, p
Protonic acid having a Ka value of 4.0 or less is effective, and a pKa value of 1 to
When the proton acid of No. 4 is used, the conductivity of the resulting film is higher as the pKa value is smaller, that is, as the acidity is stronger. However, when the pKa value is smaller than 1, the conductivity of the resulting film is almost unchanged and almost constant.

The conductivity of the polyaniline after doping with a protonic acid is usually greater than or equal to 10 ⁻⁶ S / cm, often greater than or equal to 10 ⁻⁴ S / cm, and this conductivity is not affected by humidity. In particular, the property that the conductivity does not change in a low humidity region is characteristic of the conductive polyaniline according to the present invention.
Conventionally known surfactants and polyelectrolytes as antistatic agents have an increased electrical resistance at low humidity due to their ionic conductivity, but the conductivity of the conductive polyaniline according to the present invention is Since it is electronically conductive, it is hardly affected by humidity.

Effect of the Invention As described above, the porous selective permeable membrane produced from the solvent-soluble polyaniline according to the present invention has a much higher molecular weight than conventionally known polyaniline, so that it is tough. Excellent in strength and durability, and also excellent in chemical resistance and organic solvent resistance.

Further, the conductive porous selective permeable membrane according to the present invention is also tough, excellent in flexibility and heat resistance, and has high conductivity, so that battery electrode materials, semiconductor devices,
Furthermore, it can be used for various sensors, separation membranes for various applications including electrochemical ion separation and electrical control, and the like.

EXAMPLES Hereinafter, the present invention will be described with reference to Examples along with Reference Examples for showing production and physical properties and structures of polyaniline according to the present invention, but the present invention is not limited to these Examples.

Reference Example 1 (Production of a Doped Conductive Organic Polymer by Oxidative Polymerization of Aniline) In a 1 volume separable flask equipped with a stirrer, a thermometer and a dropping funnel, 450 g of distilled water, 30 ml of 36% hydrochloric acid and 30 g of aniline (0.322 Mol) were added in this order to dissolve the aniline. Separately, while cooling with ice water, 32 g (0.32 mol) of 97% concentrated sulfuric acid was added to 112 g of distilled water in a beaker and mixed to prepare a sulfuric acid aqueous solution. This aqueous sulfuric acid solution was added to the separable flask, and the entire flask was cooled to a temperature of 5 ° C. or lower with ice water.

Next, 73.5 g (0.322 mol) of ammonium peroxodisulfate was added to 172 g of distilled water in a beaker and dissolved,
An oxidizing agent aqueous solution was prepared.

The entire flask was cooled in a cooling thermostat, and while maintaining the temperature of the reaction mixture at −3 ° C. or lower, the aqueous ammonium peroxodisulfate solution was gradually added dropwise to the aqueous aniline salt solution over 105 minutes with stirring. Initially, the colorless and transparent solution turned from green-blue to black-green as the polymerization proceeded, and then a black-green powder was deposited. After the completion of the dropwise addition of the aqueous solution of ammonium peroxodisulfate, stirring was continued for a further 45 minutes at a temperature of -3 ° C.

A part of the obtained polymer powder was collected, washed with water, washed with acetone, and vacuum-dried at room temperature to obtain a black-green polymer powder. This was pressed into a disk having a diameter of 13 mm and a thickness of 700 μm, and its electric conductivity was measured by the Van der Pauw method. As a result, it was 18 S / cm.

(Dedoping of Conductive Organic Polymer with Ammonia) To the reaction mixture in the flask containing the doped conductive organic polymer powder, 150 ml of 25% aqueous ammonia was added, and the mixture was stirred for 1.5 hours while cooling to 3 ° C. The reaction mixture is
The color changed from black-green to blue-violet.

The powder was filtered off with a Buchner funnel and washed repeatedly with distilled water until the filtrate became neutral and colorless while stirring in a beaker, and then washed with acetone until the filtrate became colorless. . Thereafter, the powder is vacuum-dried at room temperature for 10 hours to obtain a purple-purple copper-colored undoped polymer powder.
22.5 g were obtained.

This polymer was soluble in N-methyl-2-pyrrolidone, and the solubility was 8 g (7.4%) per 100 g of the same solvent. The intrinsic viscosity [η] measured at 30 ° C. using this as a solvent was 1.20.

The polymer had a solubility of less than 1% in dimethylsulfoxide and dimethylformamide. It did not substantially dissolve in tetrahydrofuran, pyridine, 80% aqueous acetic acid, 60% aqueous formic acid and acetonitrile.

Reference Example 2 (Preparation of a self-supporting film using a soluble aniphosphorylated polymer) 5 g of the undoped aniphosphorylated polymer powder obtained in Reference Example 1 was added little by little to 95 g of N-methyl-2-pyrrolidone, and the mixture was cooled to room temperature. To give a dark blue solution. When this solution was vacuum-filtered with a G3 glass filter, the amount of insolubles remaining on the filter was extremely small. The filter was washed with acetone, and the remaining insolubles were dried and weighed to give 75 mg. Therefore, 98.5% of the polymer was dissolved, and 1.5% of the insoluble matter was dissolved.

The polymer solution thus obtained was cast on a glass plate, wrung with a glass rod, and then N-methyl-2-pyrrolidone was evaporated in a hot air circulating drier. Thereafter, the polymer film was naturally peeled off from the glass plate by immersing the glass plate in cold water, thus obtaining a polymer film having a thickness of 40 μm.

After washing this film with acetone, it was air-dried at room temperature to obtain a film having a copper-colored metallic luster.

Films differ in strength and solubility depending on the drying temperature. When the drying temperature is 100 ° C. or lower, the obtained film dissolves in a small amount in N-methyl-2-pyrrolidone and has relatively low strength. However, the film obtained by heating at a temperature of 130 ° C. or more is very tough and does not dissolve in N-methyl-2-pyrrolidone or other organic solvents. Also, it does not dissolve in concentrated sulfuric acid. Thus, when heated at a high temperature, the polymer molecules are expected to crosslink with each other in the process and become insoluble.

The undoped film thus obtained is
The conductivity was in the order of 10 ^-11 S / cm.

The film did not crack even after being bent 10,000 times, and had a tensile strength of 840 kg / cm ² .

Reference Example 3 (Doping of self-supporting film with protonic acid) In Reference Example 2, the self-supporting film obtained by heating and drying at 150 ° C. for 30 minutes was placed in a 1N aqueous solution of sulfuric acid, perchloric acid and hydrochloric acid at room temperature for 66 minutes. After soaking for a time, the film was washed with acetone and air-dried to obtain a conductive film.

Each of the films exhibited a deep blue color, and the electrical conductivity was 8.2 S / cm, 11 S / cm, and 5 S / cm, respectively. The tensile strength of the film doped with perchloric acid is 500 kg / cm ²
It was.

REFERENCE EXAMPLE 4 (Spectrum and Structure of Soluble Polymer and Insoluble Film-Formed Polymer Both in Dedoped State) The soluble polymer powder obtained in Reference Example 1 and the insoluble polymer film obtained in Reference Example 2 FT-IR spectra by the KBr tablet method are shown in FIGS. 1 and 2, respectively. Since the two spectra are almost the same, although the solvent is insoluble by cross-linking by heating and drying the solvent after casting the solvent-soluble polymer, no significant change in the chemical structure has occurred. Is recognized.

FIG. 3 shows the results of thermogravimetric analysis of the soluble polymer powder and the insoluble polymer film. All have high heat resistance. Considering that the insoluble film does not decompose to a higher temperature and is insoluble in concentrated sulfuric acid, it indicates that the polymer molecules are crosslinked in the insoluble film.

FIG. 4 shows an ESR spectrum. The spin concentration was 1.4 × 10 ¹⁸ spin / g for the soluble polymer and 2.7 × 10 ¹⁷ spin / g for the insoluble polymer. As described above, the decrease in the spin concentration from the soluble polymer to the insoluble polymer is considered to be due to crosslinking of the polymer molecules during the heating and drying process of the solvent in the film preparation.

Next, the results of elemental analysis of the soluble polymer and the insoluble polymer are shown below.

Soluble polymer C, 77.97; H, 5.05; N, 14.68 (total 97.70) Insoluble polymer C, 78.31; H, 5.38; N, 15.31 (total 99.00) Based on this elemental analysis, standardized to C12.00 The composition formula of the soluble polymer is C _12.00 H _9.26 N _1.94 , and the composition formula of the insoluble polymer is C _12.00 H _9.82 N _2.01 . On the other hand, similarly, the quinone diimine structural unit and the phenylenediamine structural unit normalized to C12.00 are as follows, respectively.

Quinone diimine structural unit C ₁₂ H ₈ N ₂ phenylenediamine structural unit C ₁₂ H ₁₀ N _{2 Accordingly} , as described above, both the soluble polymer and the solvent-insoluble polymer mainly include the quinone diimine structural unit and the phenylenediamine structural unit. It is a polymer having a unit.

Next, the reflection spectra in the visible to near infrared region of the undoped film obtained in Reference Example 2 and the perchloric acid-doped film obtained in Reference Example 3 are shown in FIG. 5, respectively. In the undoped state, almost near-infrared light is reflected, but after doping, near-infrared light is absorbed, and it is recognized that there is almost no reflection. This is based on absorption by polarons or bipolarons which provides the conductivity created by proton acid doping.

By doping the undoped film with perchloric acid, the ESR absorption is greatly increased, and the spin concentration reaches 3.8 × 10 ²¹ spin / g. This is derived from the generated polaron, a semiquinone radical.

Reference Example 5 The polymer film obtained in Reference Example 2 was immersed in an aqueous solution or an alcohol solution of a protonic acid having various pKa values to examine whether or not doping was possible. The results are shown in FIG.
The conductivity of polymer films obtained by doping with protonic acids having various pKa values is shown in Table 1.

The above results indicate that a protonic acid having a pKa value of 4.0 or less is effective for polymer doping.

Example 1 4.8 g of the undoped polyaniline obtained in Reference Example 1 was
-Methyl-2-pyrrolidone was dissolved in 50 g to prepare a film-forming solution. After the film-forming solution was cast and applied on a glass plate at room temperature, the solvent was evaporated in a dryer at 100 ° C. for 10 minutes. Immediately after being taken out of the dryer, it was immediately immersed in water at 20 ° C., and the solvent was removed to form a porous film. After several hours, the porous membrane was peeled off from the glass plate. The film thickness was 50 μm. This film has an anisotropic structure in which a skin layer with a dense surface is integrally supported by a porous layer having a finger-like structure.

This membrane was attached to a batch type measuring cell, and pure water and a 0.5% aqueous solution of polyethylene glycol having an average molecular weight of 20,000 were supplied under the conditions of a temperature of 26 ° C. and a pressure of 1 kg / cm ² , and a polyethylene glycol rejection defined by the following equation: And the water permeation rate were evaluated.

The results are shown in Table 2. In addition, the polyethylene glycol concentration of the solute was measured with a TOC (total organic carbon) analyzer.

Example 2 5.0 g of the undoped polyaniline obtained in Reference Example 1 was
-Methyl-2-pyrrolidone was dissolved in 40 g, and 5 g of dimethylsulfoxide was further added and dissolved to prepare a film forming solution. This film-forming solution was applied on a glass plate by casting at room temperature, and then heated in a dryer at 80 ° C. for 15 minutes to evaporate the solvent. Immediately after being taken out from the dryer, it was immersed in water at 20 ° C., and the solvent was removed to form a porous film. The film peeled from the glass plate had a thickness of 110 μm. This film does not have a finger-like structure but has an anisotropic structure in which a dense skin layer is integrally supported on a porous layer having a sponge-like structure.

The membrane was evaluated for water permeability and polyethylene glycol rejection in the same manner as in Example 1. The results are shown in Table 2.

Example 3 The polyaniline porous membrane obtained in Example 1 was immersed in a 1N aqueous solution of sulfuric acid at room temperature for 24 hours, and was doped to impart conductivity. The apparent conductivity of the obtained conductive porous film was 0.23 S / cm.

This conductive porous membrane was evaluated for water permeability and polyethylene glycol rejection in the same manner as in Example 1. The results are shown in Table 2.

Example 4 The polyaniline porous membrane obtained in Example 2 was immersed in a 1N aqueous solution of sulfuric acid at room temperature for 24 hours, and doped to impart conductivity. The apparent conductivity of the obtained conductive porous film was 0.55 S / cm.

This conductive porous membrane was evaluated for water permeability and polyethylene glycol rejection in the same manner as in Example 1. The results are shown in Table 2.

[Brief description of the drawings]

FIG. 1 shows the KBr of polyaniline soluble in the undoped state.
FT-IR spectrum by the tablet method, FIG. 2 is an FT-IR spectrum of the solvent-insoluble film obtained by casting the above-mentioned solvent-soluble polyaniline by the KBr tablet method, and FIG. 3 is the above-mentioned soluble polyaniline and insoluble polyaniline. Thermogravimetric analysis of the film, FIG. 4 shows the ESR spectrum of the soluble polyaniline and the insoluble polyaniline, FIG.
The figure shows the reflection spectra of the undoped polyaniline film and the film doped with perchloric acid in the visible to near-infrared region, and FIG. 6 shows the undoped polyaniline film having various pKa values. 5 is a graph showing the relationship between the pKa value of a protonic acid and the conductivity of the obtained film when doped with an acid.

Claims (4)

(57) [Claims] (1) General formula (In the formula, m and n each represent a mole fraction of a quinone diimine structural unit and a phenylenediamine structural unit in the repeating unit, and are 0 <m <1, 0 <n <1, and m + n = 1). A porous unit having a repeating unit and having an intrinsic viscosity [η] of 0.40 dl / g or more in N-methylpyrrolidone measured at 30 ° C. in a undoped state, comprising undoped polyaniline. Permeable membrane. 2. The general formula (In the formula, m and n each represent a mole fraction of a quinone diimine structural unit and a phenylenediamine structural unit in the repeating unit, and are 0 <m <1, 0 <n <1, and m + n = 1). Having a repeating unit, polyaniline having an intrinsic viscosity [η] of 0.40 dl / g or more measured at 30 ° C. in N-methylpyrrolidone in the undoped state has a pKa value of 4.0.
A conductive porous selective permeable membrane comprising a doped conductive polyaniline doped with the following protonic acid. 3. An aniline in a solvent in the presence of a protonic acid having an acid dissociation constant pKa of 3.0 or less, and a reaction in a reduction half-cell reaction using a standard hydrogen electrode as a reference while maintaining the temperature at 5 ° C. or less in a solvent. An aqueous solution of an oxidizing agent having a standard electrode potential defined as an electromotive force of 0.6 V or more is defined as the amount obtained by dividing one mole of the oxidizing agent by the number of electrons required to reduce one molecule of the oxidizing agent per mole of aniline. Add 2 equivalents or more with defined equivalents to prepare polyaniline doped with the above protonic acid, then dedope the polyaniline with a basic substance, and measure at 30 ° C. in N-methylpyrrolidone. Polyaniline having an intrinsic viscosity [η] of 0.40 dl / g or more, and then dissolving the polyaniline in an organic solvent and applying it on a suitable support substrate, and then evaporating a part of the organic solvent, After, on Production of a porous selective permeable membrane made of undoped polyaniline, characterized in that it is miscible with the organic solvent but is brought into contact with a coagulation solvent that does not dissolve the polyaniline, and is desolvated to make it porous. Method. 4. A reduction half-cell reaction using aniline in a solvent in the presence of a protonic acid having an acid dissociation constant pKa of 3.0 or less, and maintaining the temperature at 5 ° C. or less, based on a standard hydrogen electrode. An aqueous solution of an oxidizing agent having a standard electrode potential of 0.6 V or more determined as an electromotive force is defined as the amount obtained by dividing one mole of the oxidizing agent by the number of electrons required to reduce one molecule of the oxidizing agent per mole of aniline. Add 2 equivalents or more with defined equivalents to prepare a polyaniline doped with the above protonic acid, then dedope the polyaniline with a basic substance, and measure in N-methylpyrrolidone at 30 ° C. Polyaniline having an intrinsic viscosity [η] of 0.40 dl / g or more, and then dissolving the polyaniline in an organic solvent and applying it on a suitable support substrate, and then evaporating a part of the organic solvent, After, on It is miscible with the organic solvent, but is brought into contact with a coagulating solvent that does not dissolve the polyaniline, and is desolvated to make it porous.
A method for producing a porous selective permeable membrane comprising a doped conductive polyaniline, wherein the porous selective permeable membrane is doped with a protonic acid having a pKa value of 4.0 or less.