JP4297831B2 - Manufacturing method of micro phase separation structure membrane with controlled orientation - Google Patents

Description

  The present invention relates to a microphase comprising a block copolymer with controlled orientation useful as an optical / electronic functional polymer material, an energy-related material, a surface-modifying material, a high-density recording material such as patterned media, and a nanofilter. The present invention relates to a method for manufacturing a separation structure membrane.

The present inventors have already disclosed a block copolymer composed of a hydrophilic polymer component and a hydrophobic polymer component in order to produce a microphase-separated structure film composed of a polymer with a uniform orientation (Patent Document 1, Non-patent document 1). The inventors have also found that a microphase-separated structure film having a uniform alignment direction can be obtained by performing a specific film forming method and heat treatment method using this block copolymer.
On the other hand, three examples of orientation control for a substrate having a microphase separation structure have been reported so far, such as substrate sharing, electric field application, and heat treatment in an organic solvent atmosphere (Non-Patent Documents 2 to 4). In any case, the film thickness is limited, and complete alignment control from the substrate surface to the film / air interface is not achieved.
JP2004-124088 Macromolecules 2002, 35, 3739-3747 Nature vol. 225, 538-539 (1970) Science vol. 273, 931-933, 1996 J. Am. Chem. Soc. 2003, 125, 12211-12216

  It has been known that when a block copolymer thin film composed of a hydrophilic polymer component and a hydrophobic polymer component is formed, this block copolymer self-assembles to form a microphase separation structure (patent) Document 1, Non-Patent Document 1), and a method for controlling the orientation of the block copolymer in this thin film has not been known.

The inventors have made a block having a microphase-separated structure in which the block copolymer in the thin film is oriented in a certain direction by solidifying the block copolymer thin film by applying an electric field of constant strength while heating the block copolymer thin film. It has been found that a copolymer thin film can be formed.
That is, in the present invention, a polymer is applied on a substrate, and an electric field of 1 × 10 ^{5 to} 3 × 10 ⁷ V / m is applied to the polymer film at a temperature 10 to 100 ° C. lower than the melting point of the polymer. Molecular weight distribution (Mw / Mn) in which the polymer is bonded to the hydrophilic polymer component (A) and the hydrophobic polymer component (B) by a covalent bond. Is a process for producing a microphase-separated structure film with controlled orientation, which is a block copolymer having a value of 1.3 or less.

  In particular, when the block copolymer is oriented perpendicularly to the substrate by the method of the present invention, the hydrophilic polymer component and the hydrophobic polymer component form a layer parallel to the substrate. It becomes possible to perform complete orientation control from the substrate surface of the microphase separation structure in the polymer thin film to the film / air interface electrochemically, and it becomes possible to obtain a thin film having specific electrochemical properties. It was. The method of the present invention shows utility as a new electrochemical processing method that simultaneously satisfies the orientation control of the phase separation structure and the construction of the nanocomposite material.

The block copolymer of the present invention is a block copolymer in which a hydrophilic polymer component (A) and a hydrophobic polymer component (B), which are incompatible with each other, are covalently linked to each other. Has physical and physical properties. Moreover, the molecular weight distribution is 1.3 or less, and the order of the constituent polymer chains A and B does not matter.
Examples of the hydrophilic polymer chain A include poly (ethylene oxide), poly (propylene oxide), poly (vinyl alcohol), poly (acrylic acid), poly (methacrylic acid), poly (acrylamide), oligo (ethylene oxide), and crown. Poly (methacrylate) or poly (acrylate) having ether, cryptand or sugar chain in the side chain, preferably poly (ethylene oxide) methyl ether.
Examples of the hydrophobic polymer chain B include poly (methacrylate), poly (acrylate), poly (styrene), and vinyl polymer having a mesogenic side chain, a long alkyl side chain, or a hydrophobic side chain.

The mesogenic side chain is, for example, the following general formula E- (Y1-F) n-Y2-G
The thing which has one or more structural units represented by these is mentioned.
In the formula, E, F and G may be the same or different and are respectively 1,4-phenylene, 1,4-cyclohexylene, 1,4-cyclohexenylene, naphthalene-2,6- Diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, 1,4-bicyclo [2.2.2] octylene, 1,3-dioxane-2 , 5-diyl, pyridine-2,5-diyl, pyrazine-2,5-diyl, pyridazine-3,6-diyl, pyrimidine-2,5-diyl, and Y1 and Y2 are the same Or may be different, a single bond, —CH ₂ CH ₂ —, —CH ₂ O—, —OCH ₂ —, —C (═O) O—, —OC (═O) —, —C≡C -, - CH = CH -, - CF = CF -, - (CH 2) 4 -, _{CH 2 CH 2 CH 2 O -} , - OCH 2 CH 2 CH 2 -, - CH = CH-CH 2 CH 2 -, - CH 2 CH 2 -CH = CH -, - N = N -, - CH = CH -C (= O) O- or -OC (= O) -CH = CH- is represented, and n represents an integer of 0 to 3.
The long-chain alkyl side chain means an alkyl side chain having preferably 6 to 22 carbon atoms.
Examples of the hydrophobic side chain include an aliphatic side chain.
The molecular weight of this block copolymer is preferably 5,000 to 100,000, more preferably 10,000 to 50,000.

This block copolymer has the following general formula (Formula 1)
(In the formula, m and n may be the same or different and each is an integer of 5 to 500, a is an integer of 1 to 22, and R is hydrogen or an alkyl group having 1 to 22 carbon atoms. Is preferred).

When such a block copolymer is dissolved in a solvent to form a film, a microphase separation structure is formed based on the repulsive interaction between different types of AB chains.
However, it has been impossible to control the orientation. For example, as shown in Comparative Example 1 (FIG. 1) to be described later, when such a block copolymer is dissolved in a solvent to form a film, the block copolymer self-assembles to form a microphase separation structure. However, the orientation was random, and each small block was oriented in an arbitrary direction, and its usefulness as a film could not be considered.

In the present invention, this block copolymer is applied on a substrate, and the temperature is 10 to 100 ° C. lower than the melting point of the polymer, for example, 50 to 80 ° C., and at the same time, 1 × 10 ⁵ to By applying an electric field of 3 × 10 ⁷ V / m, the block copolymer is oriented in the electric field direction.
As the substrate, a substrate made of a hydrophobic substance or a substrate whose surface has been subjected to a hydrophobic treatment is preferably used. For example, substrates such as polyester, polyimide, mica plate, silicon wafer, quartz plate, and glass plate, and substrates obtained by subjecting the surface of these substrates to hydrophobic treatment such as carbon deposition treatment or silylation treatment are preferably used.
As a method for coating the block copolymer on the substrate, a method in which the block copolymer is dissolved in a suitable solvent, coated on the substrate and dried is generally used. Examples of the solvent include benzene, toluene, xylene, chloroform, dichloromethane, tetrahydrofuran, dioxane, carbon tetrachloride, ethylbenzene, propylbenzene, ethylene dichloride, and methyl chloride. The concentration of the block copolymer in the solution is preferably about 0.1 to 5% by mass.

Examples of the method for applying the block copolymer on the substrate include spin coating, casting, dip and bar coating.
The thickness of the block copolymer film is preferably about 30 nm to about 10 μm.
After the block copolymer once applied is heated and solidified, the alignment treatment may be performed by heating again, or the alignment treatment and the heating may be performed simultaneously with the application of the block copolymer on the substrate. Good.
This heating temperature is preferably in the range of 10 to 100 ° C. lower than the melting point of the block copolymer (usually 120 to 140 ° C.), more preferably 50 to 80 ° C. The melting point of the block copolymer is measured by a differential scanning calorimetry method.

For the alignment treatment, an electric field of 1 × 10 ^{5 to} 3 × 10 ⁷ V / m, preferably 1 × 10 ^{5 to} 3 × 10 ⁶ V / m is applied in a heated state. Since the block copolymer of the present invention is oriented along the electric field, the electric field may be applied in a desired direction. For example, it is possible to control the orientation of the phase separation structure in a region-selective manner by using a minute comb-shaped electrode or applying a voltage by bringing a minute electrode close to a polymer-coated electrode. In particular, those in which molecules are oriented substantially perpendicular to the substrate are highly useful because they form a hydrophobic block and a hydrophilic block layer in parallel to the substrate. Accordingly, it is preferable to apply an electric field substantially perpendicularly to the substrate and to orient the block copolymer substantially perpendicularly to the substrate. It is desirable that this vertical tolerance is also determined according to the application.
The electric field may be a constant electric field between 1 × 10 ^{5 and} 3 × 10 ⁷ V / m, and the direction of the electric field (+/−) may be any. Further, the maximum value of the electric field is set to 1 × 10 ^{5 to} 3 × 10 ⁷ V / m, and the electric field is alternately swept in the + direction, the − direction, or both directions (specifically, the applied potential is swept). Also good. As is clear from Example 3 described later, it is preferable to switch the direction of the electric field in this way because the orientation becomes clearer.

There is no particular limitation on the method of applying the electric field.
As a simple method, there is a method in which a film is formed using a substrate as an electrode, an electrolytic solution is applied on the film, and a desired voltage is applied between the electrode substrate and the electrolytic solution.
The electrode substrate may be any electrode material having electrical conductivity, and may be a metal plate such as platinum, stainless steel, or gold, graphite, glass coated with indium tin oxide, a plastic film, a silicon wafer, or the like. An ITO glass electrode substrate is preferred.
As an electrolytic solution, water or an organic solvent such as tetrahydrofuran, chloroform, dimethyl sulfoxide, dimethylformamide is used as a solvent, and solutes such as potassium chloride, sodium chloride, potassium bromide, sodium bromide, sodium sulfate, sodium perchlorate A solution in which an electrolyte such as sodium nitrate is dissolved can be used.
In addition to a general electrochemical cell, a special electrochemical cell that can selectively apply an electric field to a minute region using a minute electrode such as a tip of a scanning probe microscope can be used.

Also, when applying this block copolymer on the substrate, inorganic ceramic fine particles, organic transition metal complex crystals, noble metal fine particles, metal oxide fine particles, etc. coexist with the block copolymer and solidify together with the alignment treatment. Then, depending on the properties of the fine particles, the fine particles can be aggregated in the hydrophilic portion or the hydrophobic portion of the layer structure of the block copolymer, and a film having a characteristic layer structure can be formed.
For example, magnetic iron oxide fine particles having a hydrophilic surface are dispersed in a copolymer solution, and this dispersion is applied to a slide glass, a PET film, and the like, and dried at room temperature. A film having a layer structure in which the fine particles are aggregated in the hydrophilic portion can be obtained.

  The microphase separation structure of the block copolymer thus formed is a hexagonal lattice type cylinder and sphere structure, or a lamellar structure. Further, the lattice constant serving as the structural factor depends on the molecular weights of the constituent polymer chains A and B. That is, m and n in the general formula (Formula 1) satisfy m / (m + n) = 0.1 to 0.9.

The following examples illustrate the invention but are not intended to limit the invention.
Production Example 1
A block copolymer was synthesized comprising poly (ethylene oxide) methyl ether (molecular weight 5000) as hydrophilic polymer chain A and polymethacrylate having a polymerization degree of 114 having azobenzene-containing liquid crystalline side chains and hydrophobic polymer chain B as the polymer chain. The synthesis was performed by an atom transfer radical polymerization method using a copper complex as a catalyst.
The obtained block copolymer has the following general formula (Formula 1)
(Wherein, a is 9, R is a normal butyl group, m is 114, and n is 47). The number average molecular weight is 28100, Mw / Mn = 1.08, and the polymethacrylate (MA) content is 82 wt. %, Melting point was 120 ° C.

Comparative Example 1
The copolymer obtained in Production Example 1 is dissolved in toluene so as to be 3% by mass to obtain a copolymer solution. This copolymer solution is made of highly oriented graphite, transparent conductive indium tin oxide (ITO) glass. 0.1 mL of 1 cm ² was dropped on the electrode substrate and the ITO-polyethylene terephthalate film. Immediately after that, the sample bottle containing 30 mL of toluene was transferred to a desiccator having an internal volume of 2 L and allowed to stand for 5 hours. Next, the obtained cast film was heated at a temperature of 50 to 80 ° C. for 5 to 48 hours to obtain a block copolymer thin film. The film thickness was 1.5 μm.
This block copolymer thin film was observed with an atomic force probe microscope (AFM). The result is shown in FIG. The microphase separation structure was mainly in-plane orientation.

  On the block copolymer thin film obtained in Comparative Example 1, a 0.5 mm-thick fluororesin spacer with a 1 cm square hole was placed in the center. A 0.1 M potassium bromide aqueous solution was injected into the hole as an electrolyte. A platinum wire as a counter electrode and a silver / silver chloride electrode as a reference electrode were arranged in the injected electrolyte aqueous solution. An outline of the apparatus is shown in FIG. Using the block copolymer thin film substrate as a working electrode, the set of electrolytic cells was heated to a temperature of 50 to 80 ° C., and a constant potential of +1 V was applied to the working electrode for 15 to 30 minutes.

  An experiment was conducted in the same manner as in Example 1 by applying a constant potential of -1 V to the working electrode on the block copolymer thin film having the same arrangement as in Example 1.

  A block copolymer thin film having the same arrangement as in Example 1 was swept with a working electrode at a potential range of +1 to -1 V at a scanning speed of 1 V / s for 15 to 30 minutes, and an experiment was conducted in the same manner as in Example 1. It was.

Test example 1
Among the block copolymer thin films subjected to electrochemical modification obtained in Examples 1 to 3, samples using highly oriented graphite and ITO glass electrodes as substrates were subjected to atomic force probe microscope observation. The results are shown in FIGS. In any case, it was found that the in-plane oriented microphase separation structure (FIG. 1) observed in Comparative Example 1 disappeared.
Test example 2
The sample obtained in Example 3 was observed with an atomic force probe microscope. The results are shown in FIGS. The microphase-separated structure was oriented vertically in the film thickness direction. This out-of-plane orientation was remarkably observed in the central portion where the electrode reaction was performed.
As a result of observation, it was found that 8 nm diameter pEO (polyethylene oxide) dots were arranged in a hexagonal lattice pattern.
According to the SAXS measurement performed separately, the most stable phase separation structure of this polymer is known to be a hexagonal lattice type cylinder. This suggests that the observed dots are nanopatterns derived from the (001) plane of the pEO hexagonal lattice cylinder.
Test example 3
About the sample which used the ITO-PET film of the block copolymer thin film to which the electrochemical modification was given in Examples 1 to 3 as a substrate, the hydrophilicity was obtained by holding it over an aqueous ruthenium tetroxide solution having a concentration of 0.5 to 1% by mass. Sexual areas were stained. This thin film was embedded with a thermosetting epoxy resin together with a film substrate, an ultrathin section of the film cross section was prepared using an ultramicrotome, and observed with a film cross section transmission electron microscope. The obtained transmission electron micrograph is shown in FIG. Out-of-plane orientation from the substrate / block copolymer interface to the block copolymer / air interface was observed.

A microphase-separated structure film in which the orientation of the block copolymer is controlled can be obtained by the production method of the present invention. Since such a film has its surface hydrophilicity and hydrophobicity controlled as it is, it may be used for a fiber material that is not easily soiled and easily cleaned, or a surface coating agent that is less likely to generate static electricity. In addition, by selective plating using the difference in the properties of each nano-region of the phase-separated structure, ultra-high density magnetic recording materials that reach 10 ¹¹ bits per square centimeter, and metal or semiconductor microdot fabrication substrates using vacuum thin film formation methods Available to: Furthermore, it is utilized for the diaphragm material for batteries using the ionic conductivity of the hydrophilic region.

It is a figure which shows AFM of the block copolymer thin film obtained by the comparative example 1. Since no electric field is applied, it can be seen that the molecules are oriented parallel to the substrate. The topo image represents the surface irregularities mapped by the atomic force microscope, the phase image represents the phase lag in the mechanical response of the atomic force measurement, and can evaluate the local viscoelasticity of the surface . It is a figure which shows the outline of a measuring apparatus. A block copolymer thin film is formed on the glass electrode (ITO), which is immersed in an electrolytic solution, and a voltage is applied between the glass electrode (ITO) and the electrolytic solution to apply an electric field to the block copolymer thin film. did. 2 is a diagram showing an AFM of a block copolymer thin film solidified by applying a voltage of +1 V to a silver / silver chloride electrode in Example 1 (corresponding to an electric field of + 1 × 10 ⁶ V / m). FIG. It is not observed that the molecules observed in FIG. 1 are oriented parallel to the substrate. Therefore, it is considered that the molecules are oriented perpendicular to the substrate. FIG. ⁶ is a diagram showing an AFM of a block copolymer thin film solidified by applying a voltage of −1 V to a silver / silver chloride electrode in Example 2 (corresponding to an electric field of −1 × 10 ⁶ V / m). FIG. It is not observed that the molecules observed in FIG. 1 are oriented parallel to the substrate. Therefore, it is considered that the molecules are oriented perpendicular to the substrate. Silver / (corresponding to the field + 1x10 ⁶ V / m and -1 × 10 ⁶ V / m) by applying a voltage of + 1V or -1V with respect to silver chloride electrode was solidified during which the potential was swept for 15 minutes in Example 3 It is a figure which shows AFM of a block copolymer thin film. It is clearly observed that the molecules are oriented perpendicular to the substrate. It is a figure which shows AFM of the block copolymer thin film similarly solidified by sweeping the electric potential for 30 minutes in Example 3. FIG. The vertical alignment is clearer. It is a figure which shows the transmission electron micrograph of what dye | stained the block copolymer thin film obtained in Example 1 with the ruthenium tetroxide aqueous solution. When no electric field is applied (left figure), the molecules are oriented parallel to the substrate, whereas when an electric field is applied (right figure), the molecules are oriented perpendicular to the substrate.

Claims (5)

A polymer is applied on the substrate, and an electric field of 1 × 10 ^{5 to} 3 × 10 ⁷ V / m is applied to the polymer film at a temperature 10 to 100 ° C. lower than the melting point of the polymer to orient the polymer in the electric field direction. A method for producing a microphase-separated structure film, wherein the electric field is applied by applying a predetermined voltage between the electrode substrate and the electrolytic solution by applying an electrolytic solution on the polymer film using the substrate as an electrode. Control of orientation in which the polymer is a block copolymer having a molecular weight distribution (Mw / Mn) of 1.3 or less, in which a hydrophilic polymer component (A) and a hydrophobic polymer component (B) are bonded by a covalent bond Of a microphase-separated structure membrane. The manufacturing method according to claim 1, wherein the maximum value of the electric field is set to 1 × 10 ^{5 to} 3 × 10 ⁷ V / m, and the electric field is alternately swept in the + direction, the − direction, or both directions. The process according to claim 1 or 2, wherein the temperature is 50 to 80 ° C. The block copolymer has the following general formula (Formula 1)
(Wherein, m and n are each an integer of 5 to 500, a is an integer of 1 to 22, and R is hydrogen or an alkyl group having 1 to 22 carbon atoms). The manufacturing method as described in any one of 1-3. 5. The inorganic polymer fine particles, organic transition metal complex crystals, noble metal fine particles, metal oxide fine particles, and the like coexist with the polymer when the polymer is applied on the substrate. The manufacturing method.