KR20030090905A - Preparation Method of Polyanilines - Google Patents

Abstract

PURPOSE: A method for preparing polyaniline is provided, to obtain a nanometer-sized polyaniline having a low surface resistance and a high solubility. CONSTITUTION: The method comprises the step of reacting an aniline monomer represented by the formula 1, a dopant, an azo group-containing initiator, ammonium sulfate and optionally a steric stabilizer. Preferably the azo group-containing initiator is 2,2'-azobis{2-(2-imidazolin-2-yl)propane}dihydrochloride represented by the formula 2; the dopant is selected from the group consisting of HBr, toluenesulfonic acid, dodecyl benzenesulfonic acid, halogen, a Lewis acid, a protonic acid, a transition metal, an organic electron receptor, an organic electron donator and their mixtures; and the steric stabilizer is selected from the group consisting of poly(vinyl alcohol-co-vinyl acetate), polyethylene oxide, methyl cellulose, poly(vinyl pyridine), copolymer of poly(vinyl pyridine), poly(vinyl pyrrolidone) and their mixtures.

Description

Preparation method of polyaniline {Preparation Method of Polyanilines}

The present invention relates to a method for producing polyaniline, which is a conductive polymer, and more particularly, to a method for producing polyaniline having low surface resistance and high solubility by adding a dopant, a steric stabilizer, an ammonium persulfate and an initiator to an aniline monomer. It is about.

A conductive polymer is a material having both the electrical, magnetic and optical properties of a metal and the mechanical properties and processability of a conventional polymer. It is light and flexible, and its electric conductivity and electronic state are freely controlled. In addition, since the present invention can be applied in various forms to special applications that were not feasible in the past, researches on the basics and applications for realizing them are being conducted.

As a result, many conductive polymers such as polyacetylene, polypyrrole, polythiophene, polyaniline, and the like have been released. Among these conductive polymers, polyaniline is easy to synthesize, easy to make derivatives, has high electrical conductivity, thermal atmospheric stability, and low cost. Due to the merits of research, research is being conducted worldwide.

The above-mentioned conductive polymer is a structure exhibiting n-conjugation developed along the main chain, and these compounds do not show conductivity by themselves, and show conductivity when doped with a dopant. The conductive polymer is obtained in the form of a film by the electrochemical polymerization method, the powder of the electroconductive polymer by the chemical oxidation polymerization method, the electrochemical polymerization method can be synthesized relatively simply conductive polymer, but the film forming surface It is limited to the electrode surface, and it is difficult to obtain a large area film, and there is a problem that manufacturing cost is high. In addition, since the conductive polymer obtained by the chemical oxidation polymerization method is poorly soluble in an organic solvent, it is difficult to form a film by a casting method, and in the case of a polymer that is easily dissolved in an organic solvent, there is a problem such as low conductivity.

Meanwhile, polyaniline among the conductive polymers is polymerized relatively simply by chemical oxidation and has a stable property in the air under high conductivity. In particular, they exhibit different chemical structures in the redox, doped, and undoped states. These structural changes occur reversibly, and because they exhibit stable and diverse electrochemical properties, Research is ongoing. However, like other conductive polymers, polyaniline has a π-conjugated structure, and since the benzene ring is bonded in a planar structure, the molecular chain is not flexible, strong attraction between molecules, and the influence of anions used as dopants. Therefore, it is insoluble in organic solvents and exhibits insoluble properties that do not dissolve even when heated, resulting in poor workability and film formation.

In order to solve such a problem, various improvement methods have been studied. In particular, recently, many methods such as changing dopants, complexing with existing resins or introducing branches while maintaining the structure of a conductive polymer have been published.

For example, by using paratoluene sulfonate as an electrolyte during electrochemical polymerization by changing dopants, an improved conductive polymer can be prepared without significant change in conductivity (IBM J. Res. Rev., 1983.27.342). However, in this case, there is a problem in that the dopant used is slowly eluted when the electrochemical redox is repeated.

In addition, polymers obtained by polymerizing heterocycles or aromatic compounds containing heteroatoms such as pyrrole, thiophene, and aniline are suitable as conductive materials because they are stable in the air and exhibit high electrical conductivity. Therefore, the conductivity can be adjusted.

Recently, a method of synthesizing polyaniline dissolved in an organic solvent such as chloroform, m-cresol or n-methylpyrrolidone has been developed. In addition, a process of blending polyaniline with a general polymer to impart electrical conductivity to the general polymer has also been developed. The technology for imparting processability to polyaniline is a multi-step process of dedoping the synthesized polyaniline and then re-doping with an organic acid such as dodecylbenzenesulfonic acid or camphor sulfonic acid (CSA). Therefore, there is a problem that the process is complicated.

In particular, Korean Patent Publication No. 1998-0009325 discloses a method for preparing polyaniline by reacting aniline monomer with dodecylbenzenesulfonic acid as a dopant and ammonium persulfate as an oxidant, and an ammonium derivative as an oxidant to an aniline derivative and an amine monomer. A method of preparing a conductive polymer by mixing persulfate and ferric chloride is described in Korean Patent Laid-Open Publication No. 1999-0010050, and Korean Patent Laid-Open Publication No. 1999-0018821 discloses an aniline monomer and a pyrrole monomer. A method for preparing a conductive polymer by reacting silbenzenesulfonic acid or paratoluenesulfonic acid with ammonium persulfate is described.

However, the above-described method has a problem that post-treatment is required for use in a polymer product because the polyaniline to be prepared is made of crystalline particles and is not easily dissolved in an organic solvent.

The present invention is to solve the above problems, by reacting the aniline monomer, dopant, initiator with azo groups, ammonium persulfate and steric stabilizer to produce a conductive polyaniline, has a low surface resistance and is easily dissolved in an organic solvent However, there is a technical problem in producing polyaniline, which is manufactured from nanometer-sized particles, which does not require a post-treatment process.

In addition, the present invention is to provide a method for producing a soluble conductive polyaniline excellent in chemical stability and reversibility, exhibiting high conductivity, and capable of forming a conductive composite through a blending solution with a general polymer.

1 is a diagram showing an IR spectra of polyaniline according to the present invention.

The present invention is characterized in that polyaniline is obtained by reacting aniline monomers, initiators containing azo groups and dopants and ammonium persulfate (APS).

The aniline monomer according to the present invention is an aromatic amine compound represented by the following Chemical Formula 1, and is a material used in a general polyaniline production method.

The initiator according to the present invention is added to suppress the formation of polyaniline into crystalline particles by reacting with radicals generated during the oxidative polymerization reaction, and any initiator may be used as long as it includes an azo group. , Preferably 2,2'-azobis {2- (2-imidazoline-2-yl) propane} dihydrochloride (2,2'-azobis {2- (2-imidazolin) -2-yl) propane} dihydrochloride) is good.

The dopant according to the present invention is a material used for doping that sends or removes electrons to a part of the bond? Of the conjugated system in order to give conductivity to the conjugated polymer. Hydrogen bromide (HBr) may be used. , Toluene sulfonic acid, dodecylbenzenesulfonic acid, halogen (Br ₂ , I ₂ , IBr, etc.), Lewis acid (AsF ₅ , SO ₃ , FeCl _3, etc.), protonic acid (H ₂ SO ₄ , HClO _4, etc.), Transition metals (eg, AgClO ₄ ), organic electron acceptors (tetracyanoethylene, tetratracynoquinodimethane, 2,3-dichloro-5,6-dicyano-p-benzoquinone (2, 3-dichloro-5,6-dicyano-p-benzoquinone), alkali metals, etc.] and organic electron donors (amines, etc.) may be used alone or in combination of two or more thereof. Preferably, hydrogen bromide and / or toluene sulfonic acid are used. good.

On the other hand, the ammonium persulfate is a material for generating an oxidative polymerization reaction according to the present invention as an oxidizing agent, the increase in the amount of the ammonium persulfate increases the polymerization degree of the conductive polymer, the molecular weight increases to increase the electrical conductivity of the synthesized polyaniline Done. However, if the amount of the oxidizing agent is not more than a certain molar ratio with respect to the aniline monomer, the electrical conductivity of the polyaniline produced no longer increases. On the other hand, when the amount of ammonium persulfate is less than a certain molar ratio with respect to the aniline monomer, the polymerization degree and the molecular weight of the oligomer are formed to have very low electrical conductivity. Therefore, in the present invention, the concentration of ammonium persulfate is 0.6 to 1.5 times in molar ratio with respect to the aniline monomer.

Meanwhile, as another method for preparing polyaniline according to the present invention, polyaniline may be obtained by reacting an aniline monomer represented by Formula 1, a dopant, an initiator represented by Formula 2, ammonium persulfate, and a steric stabilizer. have.

Here, the steric stabilizer is used to inhibit the coagulation of the colloid produced by the polymerization reaction, and the usable steric stabilizer may be polyvinyl alcohol-co-vinylacetate, polyethylene oxide, methyl cellulose, Polyvinyl pyridine, copolymer of polyvinyl pyridine, polyvinyl pyrrolidone and the like can be used alone or in combination of two or more, preferably polyvinyl pyrrolidone.

The polyaniline according to the present invention is an aniline monomer which is an aromatic amine compound represented by Chemical Formula 1, and 2,2'-azobis {2- (2-imidazoline-2-yl) having an azo group represented by Chemical Formula 2 as an initiator. In the form having a repeating unit represented by the following Chemical Formula 3, which has a property of dissolving in an organic solvent in a doped state by oxidative polymerization of propane} dihydrochloride, hydrogen bromide with dopant, and / or toluene sulfonic acid and ammonium persulfate. Are manufactured.

Here, the X ion of Formula 3 is an anion generated by dissociation from a dopant, for example, hydrogen bromide and / or toluene sulfonic acid in a reaction vessel, and acts as a dopant to be conductive by being doped in a polymer. The range is 4 to 12, and the average molecular weight is 2,000 to 4,000 Da.

Referring to the method for producing a polyaniline according to the present invention.

A dopant such as toluene sulfonic acid and / or hydrogen bromide is first added to the reactor maintained at 40 to 50 ° C., and an aromatic amine compound aniline and an oxidizing agent ammonium persulfate are added to the reactor, and then the mixture is slowly added. While stirring, the steric stabilizer is added as necessary, and then the oxidation polymerization reaction is performed for about 24 hours. Then, methanol is added to the reactor to terminate the reaction to obtain a synthesized polymer, which is filtered and washed several times with distilled water, methanol, acetone and the like. The washed polymer is filtered and then dried to obtain a conductive polyaniline.

The reaction mechanism of the above-described polymerization reaction is represented by the following schemes 1 and 2.

Here, the nitrogen molecules generated during the polymerization reaction provide an inert environment to the polymerization reaction, and the free radicals attack the anilium ions while the polymerization reaction proceeds. In addition, the free radicals block the ends of the anion ions to be polymerized to inhibit the production of high molecular weight polyaniline, and the hydrogen atoms forming the branches of nitrogen atoms form hydrogen bonds with oxygen atoms of water or alcohol. It acts to suppress things. For this reason, the polyaniline according to the present invention is made of polyaniline having a molecular weight of 4,000 Da or less, and is easily dissolved in an organic solvent, and does not require post-treatment, and can be applied to various films and polymer products. have.

Particularly, since polyaniline has solubility in a solvent in the state of having a conductive structure, it is possible to form a film having electrical conductivity, and because it can be manufactured in nanometer sized ultrafine particles or liquid phase without being made of crystalline particles, However, the electrode material can be easily prepared by coating a glass plate or a polymer film by solution blending with another polymer material to improve strength.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only for illustrating the present invention in detail and are not intended to limit the scope of the present invention by these examples.

<Example 1>

15 ml of 1 M toluene sulfonic acid [98.5%, ACS reagent, Aldrich Chemical Co., Ltd.] and 15 ml of 1 M hydrogen bromide [Aldrich Chemical Co., Ltd.] were mixed, and the mixed solution was homogenized using a magnetic stirrer. Then, 0.93 g of aniline [Junsei Chemical Co. Ltd, Japan], 2.28 g of ammonium persulfate [Junsei Chemical Co. Ltd, Japan], 0.5 g of 2,2'-azobis {2- (2-imidazoline-2-yl) propane} dihydrochloride [VA-044, Wako Pure Chemical Industries Ltd, Japan] as an initiator is added. After maintaining the temperature of the mixed solution at 50 ℃ and reacted for about 24 hours while stirring. Then, methanol was added to the reaction to terminate the reaction to obtain a powdery polymer. The powdery polymer obtained was washed, filtered and dried to yield 0.63 g of conductive polyaniline.

The composition ratio and reaction conditions of the reactants are shown in Table 1.

<Example 2>

15 ml of 1 M toluene sulfonic acid [98.5%, ACS reagent, Aldrich Chemical Co., Ltd.] and 15 ml of 1 M hydrogen bromide [Aldrich Chemical Co., Ltd.] were mixed, and the mixed solution was homogenized using a magnetic stirrer. Then, 0.93 g of aniline [Junsei Chemical Co. Ltd, Japan] 2.28 g of ammonium persulfate [Junsei Chemical Co. Ltd, Japan], 0.5g and 2,2'-azobis {2- (2-imidazoline-2-yl) propane} dihydrochloride [VA-044, Wako Pure Chemical Industries Ltd, Japan] Polyvinyl pyrrolidone (PVP) as a Rick stabilizer [Junsei Chemical Co. Ltd, Japan] after the addition of 1.0 g, the temperature of the mixed solution was maintained at 44 ° C. and reacted for about 24 hours with stirring.

Then, methanol was added to the reaction to terminate the reaction to obtain a powdery polymer. The powdery polymer obtained was washed, filtered and dried to yield 0.68 g of conductive polyaniline.

The composition ratio of the reactants is shown in Table 1.

Comparative Example 1

15 ml of 1 M toluene sulfonic acid [98.5%, ACS reagent, Aldrich Chemical Co., Ltd.] and 15 ml of 1 M hydrogen bromide [Aldrich Chemical Co., Ltd.] were mixed, and the mixed solution was homogenized using a magnetic stirrer. Then, 0.93 g of aniline [Junsei Chemical Co. Ltd, Japan], after adding 2.28 g of ammonium persulfate, the temperature of the mixed solution was maintained at 50 ° C. and reacted for about 24 hours with stirring.

Then, methanol was added to the reaction to terminate the reaction to obtain a powdery polymer. The powdery polymer obtained was washed, filtered and dried to yield 0.59 g of conductive polyaniline.

The composition ratio of the reactants is shown in Table 1.

Comparative Example 2

The reaction was carried out in the same manner as in Comparative Example 1, but further added 1.0 g of pyrrolidone (PVP) to the mixed solution.

As a result, 0.6 g of polyaniline was obtained.

The composition ratio of the reactants is shown in Table 1.

Aniline (g) TSA (ml) HBr (ml) VA-044 (g) PVP (g) APS (g) Temperature (℃) Color before reaction Example 1 0.93 15 15 0.5 - 2.28 44 Brown Example 2 0.93 15 15 0.5 1.0 2.28 44 Brown Comparative Example 1 0.93 15 15 - - 2.28 50 Colorless Comparative Example 2 0.93 15 15 - 1.0 2.28 50 Colorless

<Experiment>

Color change experiment

Polyaniline (PANi) obtained in order to measure the color change of the conductive polyaniline obtained by Examples 1, 2, Comparative Example 1 and Comparative Example 2 was prepared in a thin cloth form and then After leaving for 4 days to observe the color change.

The results are shown in Table 2.

Surface resistivity experiment

In order to measure the surface resistance of the conductive polyaniline obtained by Examples 1, 2, Comparative Example 1 and Comparative Example 2, the polyaniline obtained by the above Examples was coated on a PMMA thin film and then After drying for a time, the surface resistance was measured by a surface resistance measuring instrument [SM-8220, DKK, TOA Co., Japan].

The results are shown in Table 2.

Particle size measurement

Scanning electron microscope (SEM) [JSM 5410LV, Jeol, Japan] was measured to measure the particle size of the conductive polyaniline obtained by Examples 1, 2, Comparative Example 1 and Comparative Example 2.

The results are shown in Table 2.

Color of PANi after oxidation Surface Resistivity (Ω / cm ² ) Particle size (㎛) Example 1 Green 6.5-7 5-30 Example 2 Green 4.5 to 5 <1 Comparative Example 1 Green 8 to 8.5 > 100 Comparative Example 2 Blackish 8 20-100

As can be seen in Table 2, the surface resistivity and particle size of the polyaniline (Example 2) prepared by adding the initiator and the steric stabilizer was the lowest. Therefore, the polyaniline obtained in Example 2 can be easily dissolved in water, alcohols, organic solvents, and the like, compared to the polyaniline obtained in Example 1, Comparative Example 1, and Comparative Example 2.

IR Spectroscopy Experiment

The polyaniline suspension of Example 2 was dried in a drying oven for about 1 hour, and then 1 mg of 10 g of water, ethanol, methanol, DMSO, MEK, n-hexane, xylene, etc. was added to a spectra measuring instrument [V-550, Jasco, Japan] was used to measure the IR spectra.

Here, in the case of the polyaniline prepared by Example 1, Comparative Example 1 and Comparative Example 2 solubility was not able to perform a spectra measurement experiment, the spectra measurement results of Example 2 is shown in FIG.

1 is a diagram showing an IR spectra of polyaniline according to the present invention.

As shown in FIG. 1, the IR spectra of polyanili in water. In the IR spectra of the polyaniline, a plurality of absorption bands were observed at wavelengths of 300 nm to 900 nm. In particular, in the band between 350 nm and 420 nm, the benzoid ring converts π to π ^* . Absorption by electronic transition, the peak of wavelength 800nm is believed to be due to the absorption of light by the quinoid ring (quinoid ring).

Solubility Experiment

Polyaniline obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was water, methanol, ethanol, dimethyl sulfoxide (DMSO), methyl ethyl ketone (MEK), n-hexane and xylene It was dissolved in an organic solvent and examined for solubility.

The results are shown in Table 3.

menstruum water Methanol ethanol DMSO MEK n-hexane xylene Example 1 ◎ ◎ ◎ ◎ ● ● ● Example 2 ◎ ◎ ◎ ◎ ● ● ● Comparative Example 1 ● ● ● ● ● ● ● Comparative Example 2 ● ○ ○ ○ ● ● ●

◎: completely dissolved

○: partially dissolved

●: Insoluble

Indicates.

As described above, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, the exemplary embodiments described above are to be understood as illustrative in all respects and not as restrictive. The scope of the present invention should be construed that all changes or modifications derived from the meaning and scope of the appended claims and their equivalents, rather than the detailed description, are included in the scope of the present invention.

The present invention provides polyaniline by reacting an aniline monomer, a dopant, an initiator with an azo group, an ammonium persulfate and, if necessary, a steric stabilizer to obtain a nanometer-sized ultrafine polyaniline having low surface resistance and high solubility. Can be.

Claims (5)

A method for producing polyaniline, characterized in that polyaniline is obtained by reacting an aniline monomer represented by the formula (1), a dopant, an initiator containing an azo group, and ammonium persulfate. The method of claim 1, The initiator comprising the azo group is 2,2'-azobis {2- (2-imidazoline-2-yl) propane} dihydrochloride represented by the formula (2). The method of claim 1, The dopant is selected from the group consisting of hydrogen bromide, toluene sulfonic acid, dodecylbenzenesulfonic acid, halogen, Lewis acid, protonic acid, transition metal, organic electron acceptor, organic electron donor and mixtures of two or more thereof Method for producing polyaniline. The process for producing polyaniline according to any one of claims 1 to 3, wherein the steric stabilizer is further mixed. The method of claim 4, wherein The steric stabilizer is selected from the group consisting of polyvinyl alcohol-co-vinylacetate, polyethylene oxide, methyl cellulose, polyvinyl pyridine, copolymers of polyvinyl pyridine, polyvinyl pyrrolidone and mixtures of two or more thereof Process for producing polyaniline