JP4022571B2 - Method for producing polymer fine particles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, polymer fine particles may particularly efficient the rod-like polymer fine particles, a process for producing a polymer fine particles to be produced with high uniformity.
[0002]
[Prior art]
Recent advances in microelectronics have led to a surge in demand for nanometer (nm) scale ultrafine particle materials that make up the conventional bulk or molecular size intermediate region. The above-mentioned fine particles exhibit various interesting properties such as a catalytic effect based on a specific surface structure, a light physical property due to a size effect, and nonlinear optical characteristics. So far, methods for producing fine particles of inorganic semiconductors, metals and ceramics have been studied with the intention of applying them to the fields of electronics, catalysts and nonlinear optics.
[0003]
The fine particles of inorganic materials have generally been prepared by a gas phase method such as an electric furnace method or a plasma method, or a liquid phase method such as a freeze drying method or a spray drying method. However, there are few examples of organic material fine particles that are expected to have higher functions than inorganic materials, and examples thereof include a vapor phase method of evaporating in an inert gas. For example, a vapor phase growth method of low molecular weight organic compounds such as anthracene, pyrene and phthalocyanine, and polymer fine particles such as polymethyl methacrylate and polystyrene is described (for example, see Non-Patent Document 1). In addition, there is a description of preparation of fine particles of calcium stearate by a vapor phase method (see, for example, Non-Patent Document 2).
[0004]
However, the vapor phase growth method has essential limitations such as (1) high temperature required and (2) limited to low molecular compounds having a molecular weight of about 10,000 or less. In general, organic materials have low heat resistance and are likely to deteriorate, so there are limits to the application of this method, and it is difficult to specify the particle size, crystallinity, molecular weight, etc. within a specific range, which is problematic for application. It is easy to produce. Therefore, a more effective manufacturing method has been desired.
[0005]
On the other hand, as a method for producing fine particles of various materials including organic substances, a scientific condensation method is known, for example, a method in which sulfur is dissolved in anhydrous alcohol and then poured into water, a method in which carotene is dissolved in acetone and in water. A pouring method and the like are disclosed (for example, see Non-Patent Document 3). However, as a method for producing fine particles of various materials including organic substances, there are practically no examples of meaningful functional organic material fine particles to the extent described above.
[0006]
In addition, the emulsion polymerization method obtained by polymerizing polymer fine particles in the presence of a surfactant is limited to general-purpose polymers such as acrylic resins and styrene resins. Mixing was unavoidable and uniform fine particles could not be obtained.
[0007]
All of the above-mentioned various production methods have been pointed out to be disadvantageous in that it is difficult to control the size and particle size distribution of the produced fine particles, and it is difficult to obtain rod-shaped fine particles.
[0008]
On the other hand, carbon nanotubes, which are typical rod-shaped fine particles, have been actively researched and developed with the expectation of exhibiting their unique electrical properties, but their production methods include arc discharge, laser irradiation, and chemical vapor polymerization. Control of length and aspect ratio is still difficult.
[0009]
Masuda et al. Peeled off the anodized alumina from aluminum and selectively broken the barrier layer by ion beam irradiation to produce through-holes. A polythiophene solution was dropped into the through-holes, poured and dried. This method is not intended to extract particles (see Non-Patent Document 4).
[0010]
In addition, the technical content relevant to this invention is disclosed (for example, refer nonpatent literatures 5 and 6).
[0011]
[Non-Patent Document 1]
Toyoda, Functional Materials, Brother Vol.7, No.6, p.44-49 (June 1987 issue)
[Non-Patent Document 2]
Yase et al., Surface Science Vol. 8, No. 5, pp. 434-439 (1987)
[Non-Patent Document 3]
B. Yagens et al., Tamamushi translation "Colloid Chemistry", pages 20 and 256 (1967 Baifukan Publishing)
[Non-Patent Document 4]
48th Applied Physics Related Conference Lecture Proceedings (2001.3) 29a-ZH-9
[Non-Patent Document 5]
Polymer Science Society Proceedings Vol. 51, no. 4, p. 785
[Non-Patent Document 6]
Polymer Science Society Proceedings Vol. 51, no. 12, p. 3151
[0012]
[Problems to be solved by the invention]
However, in the method developed by Masuda et al. Described above, since the polymer solution is also adhered to the alumina template, the polymer is generated not only in the pores but also on the surface, and the rod-shaped fine particles are polymerized when trying to take out as particles. Only forested structures can be obtained on thin films. In addition, since the polymer solution is injected only where it is selectively aimed, there is a problem that the number of particles is extremely small when trying to take out as a particle.
[0013]
The present invention has been made in view of such problems, and an object thereof is shaped to provide a method for producing a uniform polymer fine particles.
[0015]
[Means for Solving the Problems]
The method for producing polymer fine particles of the present invention is a method using porous alumina obtained by anodizing aluminum as a template when producing polymer fine particles by an electrolytic polymerization method.
[0016]
Here, in the method for producing polymer fine particles described above, it is preferable to take out the polymer fine particles by dissolving the template used for the electropolymerization in an acidic aqueous solution or an alkaline aqueous solution. The fine polymer particles are preferably rod-like fine polymer particles. The average diameter of the rod-like polymer fine particles is preferably in the range of 2 to 200 nm. The average length of the rod-like polymer fine particles is preferably in the range of 10 to 200,000 nm. The fine polymer particles are preferably made of a conductive polymer compound.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
First, a method for producing polymer fine particles will be described.
This manufacturing method is a method in which polymer fine particles are electrolytically polymerized using porous alumina obtained by anodization as a template, and the aluminum fine particles are dissolved to take out the polymer fine particles alone.
[0018]
The porous alumina obtained by anodizing aluminum will be described. The porous alumina used in the present invention is, for example, a porous alumina film formed on the surface of aluminum by anodizing aluminum in an acidic electrolyte solution or an alkaline electrolyte solution. Those having the characteristics that the pores are formed in a self-regulating manner and the uniformity of the pore diameter is relatively good are employed.
[0019]
The method using the aluminum anodized film will be described in more detail. The aluminum anodic oxide film having fine pores on aluminum used in the present invention can be easily obtained by anodizing aluminum in an aqueous solution of sulfuric acid, oxalic acid, phosphoric acid or the like. The pores formed in the anodized film are minute and uniform, substantially parallel to each other, and distributed at almost equal intervals. The pore diameter, length, interval, etc. of the pores are controlled by the electrolytic conditions such as the electrolytic solution used, the voltage between the counter electrodes, and the liquid temperature. By controlling the electrolysis conditions, for example, an aluminum anodic oxide film having a uniform hole diameter and a hole interval having a hole diameter of 5 to 500 nm, a hole length of 0.05 to 500 μm, and a hole interval of 0.05 to 0.5 μm It is possible to obtain
[0020]
Next, the electrolytic polymerization will be described.
When producing the polymer fine particles by the electrolytic polymerization method, the polymer fine particles of the present invention can be produced in the pores by using the above-mentioned porous alumina as a template for the anode.
[0021]
Electropolymerization of the polymer fine particles according to the present invention is performed in the presence of a supporting electrolyte. Supporting electrolytes include tetramethylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, tetra-n-butylammonium tetrafluoroborate, lithium tetrafluoroborate, tetramethylammonium perchlorate, tetraethylammonium perchlorate, Tetra n-butylammonium chlorate, lithium perchlorate, tetramethylammonium hexafluorophosphate, tetra n-butylammonium hexafluorophosphate, sodium hexafluorophosphate, tetra n-butylammonium hexafluoroarsenate, hexafluoroarsenic Sodium sulfate, sulfuric acid, tetramethylammonium hydrogen sulfate, tetra-n-butylammonium hydrogen sulfate, sodium trifluoroacetate, tetramethyl p-toluenesulfonate Ammonium, etc. p- toluenesulfonic acid tetra n- butyl ammonium.
[0022]
The polar solvent used in the electropolymerization is not particularly limited, and water, acetonitrile, DMF, nitrobenzene, chloroform, tetrahydrofuran and the like can be used.
[0023]
The porous alumina described above is used as the anode in the present invention, and an electrode made of iron, carbon, aluminum, gold, platinum, conductive glass or the like is used as the cathode.
[0024]
As the electropolymerization method used in the present invention, a constant voltage method or a constant current method can be used, or a method of changing either voltage or current stepwise, pulsewise or cyclically can be adopted. The polymerization conditions such as voltage value, current value, quantity of electricity, degree of polymerization, polymerization atmosphere, etc. can be appropriately selected according to the type, characteristics, film thickness, etc. of the conductive polymer film to be produced.
[0025]
Examples of the material for producing polymer fine particles used in the present invention include pyrrole, thiophene, furan, α, α, α ′, α′-tetrabromo-p-xylene, aniline, acetylene, and the like.
[0026]
As the polymer fine particles, conductive polymer compounds such as polypyrrole, polyparaphenylene, polyparaphenylene vinylene, polyaniline, polyacetylene, polydiacetylene, and polythiophene are preferable.
[0027]
Next, dissolution of the template will be described.
Only the fine polymer particles can be taken out by dissolving the template used for the electropolymerization in an acidic aqueous solution or an alkaline aqueous solution.
[0028]
Examples of the method for dissolving the template include various methods such as a usual method for dissolving aluminum, such as ultrasonic waves, stirring, and raising the temperature of the solution.
When ultrasonic waves are used, the template can be dissolved by dipping in a 1.25 M NaOH aqueous solution for about 4 minutes.
[0029]
The solution for dissolving the template will be described. The solution for dissolving aluminum oxide is an acidic aqueous solution or an alkaline aqueous solution. Specifically, an acidic aqueous solution such as HCl and H ₂ SO ₄ or an alkaline aqueous solution such as NaOH, KOH, Ca (OH) ₂ , and Ba (OH) ₂ can be used.
[0030]
Next, dialysis of the solution will be described.
After the acidic aqueous solution is added to the alkaline aqueous solution in which the polymer fine particles are dispersed and made acidic, the acidic solution can be dialyzed. Na ⁺ and Al ³⁺ can be removed by dialysis.
[0031]
As the dialysis membrane, cellulose or the like can be used.
This dialysis treatment may be omitted if coexistence with other ions is allowed.
[0032]
Next, the polymer fine particles produced by the above-described method will be described.
The shape of the polymer fine particles is rod-shaped. The bar-shaped cross section is substantially circular. The longitudinal direction of the bar shape has a substantially uniform thickness.
[0033]
Polymer fine particles having an average diameter in the range of 2 to 200 nm can be produced. Here, the average diameter is a value obtained by measuring and averaging the diameters of 20 polymer fine particles by observation with an electron microscope.
[0034]
The average diameter of the polymer fine particles can be controlled by the following method. That is, the average diameter can be changed by controlling the applied voltage when the template is produced by the anodic oxidation method.
[0035]
Polymer fine particles having an average length in the range of 10 to 200,000 nm can be produced. Here, the average length is a value obtained by measuring and averaging the lengths of 20 polymer fine particles by observation with an electron microscope.
[0036]
The average length of the polymer fine particles can be controlled by the following method. That is, the length of the polymer fine particles can be controlled by the electrolytic polymerization time (coulomb amount) in the electrolytic polymerization. The particle length increases in proportion to the electropolymerization time.
[0037]
An application example of polymer fine particles will be described. The polymer fine particles can be used as an additive for a nanocomposite, a single electron transistor, an optical element (nonlinear optical element), or the like. This will be specifically described below.
[0038]
Polymer fine particles are mixed (doped) into materials such as nanocomposite polymers. A polymer mixed with polymer fine particles is melted to form a film (for example). By doing so, an increase in conductivity and strength can be expected. This is because the material of the polymer fine particles is a conductive polymer and has conductivity, so that it can impart conductivity when doped. Further, when doped due to the size and electrostatic property of the polymer fine particles, the strength increases.
[0039]
Single Electron Transistor Unlike conventional transistors, medium charged particles can be reduced to the quantum limit of one electron. This order of one electron is the smallest. As a result, the energy required for the transistor is kept to a minimum, resulting in a transistor having not only a size but also a minimum energy consumption.
[0040]
Single-electron transistors use quantum phenomena such as Coulomb blockade. Conventionally, nano-sized inorganic semiconductors are used, but we use fine polymer particles (conductive polymers). In order to produce a single-electron transistor, it is necessary to reduce the size of the polymer fine particles to a nano-size where a quantum effect appears. If the size is reduced to the nano level, the quantum effect due to the wave nature of photons and electrons appears, and the energy band becomes discretized. In a state where the energy order is discretized, a finite gap is formed in the energy order between a state where one electron is charged in the polymer fine particle and a state where it is not, for example, Coulomb blockade. If this gap is utilized via an electric potential, it is possible to digitally identify the state in which one electron is charged in the polymer fine particle. Such identification is a technique that can be achieved by discretizing, that is, quantizing, energy ranks as particles are minimized.
[0041]
When the polymer fine particles trap and charge one electron, the potential changes due to the electrons, and the energy eigenvalue changes. Using a production electrode consisting of a gate, emitter, and collector like a transistor, and combining so that the tunnel current between the emitter and collector changes greatly due to changes in the energy eigenvalue, a single-electron transistor using polymer particles is realized. It becomes possible.
[0042]
Optical nonlinearity required for optical element light amplification and modulation and optical memory operation. In a nano-sized particle, when a plurality of electrons receiving light energy are present in the particle at the same time, the electrons influence each other and non-linearity occurs. Therefore, nano-sized particles are a promising material for nonlinear optical devices.
[0043]
From the above, according to this embodiment, porous alumina obtained by anodizing aluminum is used as a template, and polymer fine particles are taken out by dissolving this template. Can be obtained. That is, polymer fine particles having a highly controlled average diameter and average length can be obtained. The polymer fine particles can be used as a material in a wide range of fields such as various electronics.
[0044]
The present invention is not limited to the above-described embodiment, and various other configurations can be adopted without departing from the gist of the present invention.
[0045]
【Example】
Next, specific examples of the present invention will be described. However, it goes without saying that the present invention is not limited to these examples.
[0046]
[Example 1]
An electropolished Al plate (thickness = 0.5 mm) is subjected to an anodic oxidation treatment to produce alumina (Al ₂ O ₃ ) as a template. The reaction at this time is carried out in a 15% by mass sulfuric acid aqueous solution (18 ° C.) by applying a potential difference of about 15 V between the anode Al plate and the cathode C over 30 to 35 minutes. By performing an anodic oxidation reaction under these conditions, alumina having a diameter of about 20 nm and a depth of about 10 μm arranged vertically can be obtained.
[0047]
Next, an electrolytic polymerization reaction is performed by applying a potential of about −1.5 V vs. a saturated calomel electrode (SCE) to the working electrode alumina. The reaction at this time includes 0.05M monomer α, α, α ′, α′-tetrabromo-p-xylen, 0.1M electrolyte (tetraethylammonium tetrafluorate), and 0.2% by mass of H ₂ O. In DMF solution (room temperature). A Pt plate was used as the counter electrode. By this polymerization, polyparaphenylene vinylene (poly (p-phenylene vinylene)) is generated in the pores of alumina.
[0048]
Thereafter, in order to obtain a dispersion of polymer fine particles, the template (Al ₂ O ₃ ) in which the polymer is polymerized in the pores is placed in a 1.25 M NaOH aqueous solution for about 4 minutes, and then subjected to ultrasonic cleaning to remove the template. Dissolved. By this operation, polymer fine particles were dispersed in the NaOH aqueous solution.
[0049]
Through a series of operations, poly (p-phenylene vinylene) having an average diameter of 20 nm could be obtained. The confirmation of poly (p-phenylenevinylene) was performed by transmission electron microscope observation.
[0050]
The diameter of the polymer fine particles was measured by measurement using a transmission electron microscope.
[0051]
The average diameter is a value obtained by measuring and averaging the diameters of 20 polymer fine particles by observation with an electron microscope.
[0052]
[Example 2]
An electropolished Al plate (thickness = 0.5 mm) is subjected to an anodic oxidation treatment to produce alumina (Al ₂ O ₃ ) as a template. The reaction at this time is carried out in a 15% by mass sulfuric acid aqueous solution (18 ° C.) by applying a potential difference of about 15 V between the anode Al plate and the cathode C over 30 to 35 minutes. By performing an anodic oxidation reaction under these conditions, alumina having a diameter of about 20 nm and a depth of about 10 μm arranged vertically can be obtained.
[0053]
Next, an electrolytic polymerization reaction is performed by applying a potential of about 1.0 V vs. a saturated calomel electrode (SCE) to the working electrode alumina. The reaction at this time was performed in an acetonitrile solution (room temperature) containing pyrrole as a 0.05 M monomer and 0.1 M electrolyte (lithium perchlorate). A Pt plate was used as the counter electrode. This polymerization produces a polymer in the pores of the alumina.
[0054]
Thereafter, alumina as a template is dissolved in a 1.25 M NaOH aqueous solution, and only the polymer is dispersed in the solution.
[0055]
Through a series of operations, polypyrrole having an average diameter of 20 nm and an average length of 6 μm could be obtained. The polypyrrole was confirmed with a transmission electron microscope.
The length of the polymer fine particles was measured by measurement by observation with a transmission electron microscope.
The average length is a value obtained by measuring and averaging the lengths of 20 polymer fine particles by observation with an electron microscope.
The method for measuring the diameter of the polymer fine particles and the definition of the average diameter are the same as in Example 1.
[0056]
[Example 3]
An electropolished Al plate (thickness = 0.5 mm) is subjected to an anodic oxidation treatment to produce alumina (Al ₂ O ₃ ) as a template. The reaction at this time is carried out in a 15% by mass sulfuric acid aqueous solution (18 ° C.) by applying a potential difference of about 10 V between the anode Al plate and the cathode C over 30 to 35 minutes. By performing an anodic oxidation reaction under these conditions, alumina having a diameter of about 13 nm and a depth of about 10 μm arranged vertically can be obtained.
[0057]
Next, an electrolytic polymerization reaction is performed by applying a potential of about 1.0 V vs. a saturated calomel electrode (SCE) to the working electrode alumina. The reaction at this time was performed in an acetonitrile solution (room temperature) containing pyrrole as a 0.05 M monomer and 0.1 M electrolyte (lithium perchlorate). A Pt plate was used as the counter electrode. This polymerization produces a polymer in the alumina pores.
[0058]
Thereafter, alumina as a template is dissolved in a 1.25 M NaOH aqueous solution, and only the polymer is dispersed in the solution.
[0059]
Through a series of operations, polypyrrole having an average diameter of 13 nm could be obtained. The polypyrrole was confirmed with a transmission electron microscope. The method for measuring the diameter of the polymer fine particles and the definition of the average diameter are the same as in Example 1.
[0060]
[Example 4]
An electropolished Al plate (thickness = 0.5 mm) is subjected to an anodic oxidation treatment to produce alumina (Al ₂ O ₃ ) as a template. The reaction at this time is carried out in a 15% by mass sulfuric acid aqueous solution (18 ° C.) by applying a potential difference of about 15 V between the anode Al plate and the cathode C over 30 to 35 minutes. By performing an anodic oxidation reaction under these conditions, alumina having a diameter of about 20 nm and a depth of about 10 μm arranged vertically can be obtained.
[0061]
Next, an electrolytic polymerization reaction is performed by applying a potential of about 1.0 V vs. a saturated calomel electrode (SCE) to the working electrode alumina. The reaction at this time was performed in an acetonitrile solution (room temperature) containing pyrrole as a 0.05 M monomer and 0.1 M electrolyte (lithium perchlorate). A Pt plate was used as the counter electrode. This polymerization produces a polymer in the pores of the alumina.
[0062]
Thereafter, in order to obtain a dispersion of polymer fine particles, the template (Al ₂ O ₃ ) in which the polymer is polymerized in the pores is placed in a 1.25 M NaOH aqueous solution for about 4 minutes, and then subjected to ultrasonic cleaning to remove the template. Dissolved. By this operation, polymer fine particles were dispersed in the NaOH aqueous solution.
[0063]
Next, the 1.25 M aqueous HCl solution was added to the 1.25 M aqueous NaOH solution in which the polymer fine particles were dispersed in about 2 to 3 times to make it acidic, and the mixture was stirred. When it became clear to some extent, this acidic solution was dialyzed to remove Na ⁺ and Al ^{3 +} .
[0064]
The dialysis treatment was performed by putting the acidic solution into the dialysis membrane, connecting the ends of the dialysis membrane, and immersing the dialysis membrane in a beaker containing pure water. This dialysis treatment was performed until the solution became neutral. The used dialysis membrane was manufactured by Kowa Equipment Co., Ltd., having a hole diameter of 24 angstroms, and was used for dialysis treatment after being washed.
[0065]
The following effects can be obtained by dialysis treatment. By dialysis, only polymer fine particles can be present in pure water, not in an aqueous NaOH solution.
[0066]
Therefore, in the NaOH aqueous solution, Al ions generated when the alumina of the template is dissolved may form a precipitate or a complex. However, since these can be stored in water by dialysis, The possibility of making disappears.
[0067]
In addition, since only polymer fine particles are dispersed in water, there is no other obstacle when measuring the properties of the polymer fine particle dispersion or when observing the particles. It becomes easy to measure properties and observe / measure shapes.
[0068]
Through a series of operations, polypyrrole having an average diameter of 20 nm could be obtained. The polypyrrole was confirmed with a transmission electron microscope. The method for measuring the diameter of the polymer fine particles and the definition of the average diameter are the same as in Example 1.
[0069]
From the above, according to the present embodiment, porous alumina obtained by anodizing aluminum is used as a template, and only the polymer fine particles are taken out by dissolving this template. Can be obtained. That is, polymer fine particles having a highly controlled average diameter and average length can be obtained.
[0070]
【The invention's effect】
Porous alumina obtained by anodizing aluminum is used as a template, and polymer fine particles are taken out by dissolving the template, so that polymer fine particles having a uniform shape can be obtained.

Claims (6)

A method for producing polymer fine particles, characterized in that porous alumina obtained by anodizing aluminum is used as a template when producing polymer fine particles by an electrolytic polymerization method. The method for producing polymer fine particles according to claim 1 , wherein the polymer fine particles are taken out by dissolving the template used for the electropolymerization in an acidic aqueous solution or an alkaline aqueous solution. 3. The method for producing polymer fine particles according to claim 2 , wherein the polymer fine particles are rod-shaped polymer fine particles. The average diameter of rod-shaped polymer particles is in the range of 2 to 200 nm. The method for producing polymer particles according to claim 3 . The average length of rod-shaped polymer fine particles is in the range of 10 to 200,000 nm. The method for producing polymer fine particles according to claim 4 . The method for producing polymer fine particles according to claim 2 , wherein the polymer fine particles comprise a conductive polymer compound.