JP3128782B2 - Method for producing crosslinked polymer thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a crosslinked polymer thin film having excellent strength and stability.

[0002]

2. Description of the Related Art The LB method is known as a method for producing an organic thin film whose structure is controlled at a molecular level. In the LB method, a developing solution is prepared by dissolving an amphiphilic substance in an organic solvent, and the developing solution is developed on a subphase such as water.
The amphiphilic substance becomes a molecular aggregate in which a hydrophilic group and a hydrophobic group are oriented toward the liquid phase and the gas phase, respectively, and forms a monomolecular film at the air-water interface. When this monomolecular film is transferred onto an appropriate substrate such as a glass plate, a thin film laminated in monomolecular film units is formed. In the specification of the present application, "thin film" is used to mean both a monomolecular film and a cumulative film.

A typical example of the amphiphile is a long-chain alkyl carboxylic acid. However, organic thin films made from long-chain alkyl carboxylic acids do not have sufficient strength. For example, when immersed in an organic solvent, the film structure is easily disturbed, and there is a problem in the stability of the thin film.

In order to improve the strength of a thin film, a method is used in which a polymer compound is used as an amphipathic substance having polymerizability, polymerized in advance at an air-water interface, and then transferred to a substrate [R. R. M
cCaffery et al. Polym. Phys. Ed
23 1523 (1985)], a method of transferring a monomer as it is to a substrate and causing a polymerization reaction on the substrate [A. C
emel et al. Polym. Sci. A-1 10
2061 (1972)] and the like, it has been proposed to polymerize and stabilize a thin film. Also,
A method for producing a high-strength thin film by using an amphiphilic polymer compound [R. J. Elbert et al. A
m. Chem. Soc. 107 4134 (198
5)] and a method of accumulating an ion complex of an amphiphilic tertiary amine and a polyanion [Masa-aki
KAKIMOTO et al. Chem. Lett., 823
(1986)].

Further, it has been reported that a thin film having a high strength can be produced by a method in which an amphiphilic polymer having an unsaturated bond is spread on a water surface, and then the polymer is crosslinked and accumulated [R. JIONES and others Thin Soli
d Films, 186 (1990)].

[0006] The present inventors also formed a two-dimensional polyion complex between an amphiphilic polymer having a cationic or anionic group in the hydrophilic part and an anionic or cationic water-soluble polymer. On how to fabricate a salt-crosslinked polymer thin film [Toyoyoshi Kunitake et al. Macromol
ecules 22 485 (1984)]. In addition, after forming a polyion complex between the polymers using an amphiphilic polymer having an anionic group in the hydrophilic part and a cationic water-soluble polymer, two-dimensionally salt-crosslinking and accumulating, He also introduced stabilization of thin films by forming covalent crosslinks between polymers [Toyoki Kunitake et al.
Chem. Lett., 1927 (1990)].

[0007]

SUMMARY OF THE INVENTION A method of transferring a bilayer film to a substrate after preliminarily polymerizing at a gas-water interface using a polymerizable amphiphilic substance, and transferring the bilayer film to a substrate in a monomer state. The method of polymerizing a bilayer film on a substrate, the method of accumulating an amphiphilic polymer compound, the method of accumulating an ion complex of an amphiphilic tertiary amine and a polyanion, etc.
All of the obtained thin films are linear polymers and do not yet have sufficient strength. Therefore, when transferring a thin film to a porous substrate having a diameter of several μm, the pores on the substrate cannot be covered with the thin film. Or even if the pores are covered with a thin film,
Since the film structure is not sufficiently maintained at the time of immersion in the solvent, a defect occurs when the transferred thin film is immersed in the solvent.

On the other hand, a method in which an amphiphilic polymer having an unsaturated bond is developed at an air-water interface and then the polymer is cross-linked and accumulated, and a polyion complex is formed between the amphiphilic polymer and the water-soluble polymer. A thin film produced by a method or the like, or a thin film crosslinked by a covalent bond, has excellent coatability on a porous substrate and exhibits excellent properties such as barrier properties when immersed in a solvent. However, in a system for forming a polyion complex, either the polycation or the polyanion is required to be an amphiphilic polymer having both a hydrophobic site and a hydrophilic site. In addition, in the method of cross-linking and accumulating the polymer after the amphiphilic polymer is developed at the air-water interface, the polymer is not only amphiphilic, but also needs to have an unsaturated bond. Are very limited.

[0009] The present invention has been devised to solve such a problem, and by using an amphipathic substance separately from a water-soluble polycation and polyanion,
An object of the present invention is to provide a crosslinked polymer thin film which relaxes restrictions on usable polycations and polyanions, has good coatability on a porous substrate, and has excellent strength and stability.

[0010]

According to the present invention, there is provided a method for producing a crosslinked polymer thin film, comprising the steps of:
An ion complex consisting of a water-soluble polyanion and a water-soluble polycation is generated at the air-water interface, and after transferring the ion complex onto a substrate, a shared ion is formed between the polyanion and the polycation constituting the ion complex. It is characterized by forming crosslinks by bonding.

When a tertiary amine having a long-chain alkyl group, a polyanion having a carboxyl group and a polycation having a primary or secondary amine are used as the amphiphilic substance, the water-soluble polyanion and the water-soluble polycation, After accumulating the polyion complex, the amphiphile is removed by heat treatment. Then, by performing a condensation reaction between the carboxylic acid and the amine, a two-dimensionally crosslinked polymer thin film can be obtained.

[0012]

In the present invention, a polyion complex comprising an amphiphilic substance, a water-soluble polyanion and a water-soluble polycation is formed at the air-water interface. The polyion complex is transferred to a substrate to form a covalent crosslink between the polyanion and the polycation. The obtained thin film has a two-dimensionally crosslinked structure by covalent bonds on the substrate, and is very stable.
In addition, since the thin film at the air-water interface is transferred onto the substrate as a stable film that is ion-crosslinked between polymers, it has excellent coverage on the pores on the substrate surface, and is free from defects even on a porous substrate. Is formed.

The use of an amphiphile stabilizes a polyion complex consisting of a water-soluble polyanion and a water-soluble polycation at the air-water interface. Therefore, a thin film can be formed from a polymer that cannot be used in the method of forming a polyion complex between an amphiphilic polymer and a water-soluble polymer.

The amphiphilic substance used in the present invention has a hydrophobic chain having excellent orientation and an anionic or cationic hydrophilic part. For example, there is a hydrophobic chain having one or more alkyl chains having 10 or more carbon atoms, a cationic hydrophilic portion includes a primary, secondary or tertiary amine, and an anionic hydrophilic portion. Examples include a carboxyl group, a sulfone group and a phosphoric acid group.

Such amphiphilic substances include those represented by the following structural formulas (1) to (4). However, R ¹ in the formula contains a hydrophobic group such as an alkyl chain or a fluorocarbon chain, and as long as the amphiphilic substance forms a stable film at the air-water interface, an ether bond, an ester bond, an amino bond Etc. may be included. R ¹ can have two or more alkyl chains or fluorocarbon chains through these bonds. Further, the amphiphilic substance may be in a salt state as long as a stable film is formed at the air-water interface. R ² and R ³ represent hydrogen or a methyl group.

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Further, an amphiphilic substance represented by the following formula can also be used.

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As the water-soluble polyanion, those having an anionic group such as a carboxyl group in the side chain are used. For example, water-soluble polyanions having the structures represented by the following formulas (5) to (7) are listed. Here, R ¹ in the formulas (5) to (7) is hydrogen, a phenyl group, an alkoxyl group or an alkyl group. Further, m and n indicate the fraction (%) of each group, and n is a numerical value of 0 or more that satisfies the condition of n + m = 1.

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As the water-soluble polycation, those having a cationic group such as a primary amine or a secondary amine in a side chain and being soluble in water while forming an ion complex are used. Specifically, there are polyvinylamine, polyethyleneimine, polyallylamine and the like.

When a cationic amphiphile is used, a polyion complex comprising an amphiphile, a water-soluble polyanion and a water-soluble polycation is used in an organic solvent containing the amphiphile and an anionic water-soluble polymer. A solution is prepared, and an organic solvent solution is developed on an aqueous solution containing a cationic water-soluble polymer, whereby the solution is formed at the air-water interface. When an anionic amphiphilic substance is used, an organic solvent solution containing an amphiphilic substance and a cationic water-soluble polymer is prepared, and the organic solvent solution is placed on an aqueous solution containing an anionic water-soluble polymer. To expand.

The monomolecular film of the polyion complex formed at the air-water interface is transferred to a substrate by an appropriate method. For the transfer, various methods known as the LB method can be adopted. As a result, a cumulative film in which one or two or more monomolecular films are stacked on the substrate surface is obtained.

When a tertiary amine having a long-chain alkyl group, a polyanion having a carboxyl group and a polycation having a primary or secondary amine are used as the amphiphile, water-soluble polyanion and water-soluble polycation, respectively, The amphiphile is removed by heating the thin film transferred to. Then, a condensation reaction between the carboxylic acid and the amine is performed to convert the polymer thin film into a two-dimensionally crosslinked polymer thin film by an amide bond, an imide bond, or the like.
This conversion can also be performed by immersing the thin film in a solution containing a condensing agent such as carbodiimide.

[0022]

【Example】

Example 1 An amphiphilic substance having the structure of the following formula (8) was used, and a commercially available polymer having a structure of the following formula (9) was purified and used as a water-soluble polyanion. As the water-soluble polycation, a commercially available polyallylamine hydrochloride having a structure of the formula (10) neutralized was used.

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An amphiphilic substance (8) and a water-soluble polyanion (9) were dissolved in a solvent in which tetrahydrofuran and dimethyl sulfoxide were mixed at a ratio of 7: 3 to prepare a developing solution. The ratio of the water-soluble polyanion (9) to the amphipathic substance (8) was set such that the repeating unit of the water-soluble polyanion (9) contained one molecule of the amphipathic substance (8). The developing solution is water-soluble polycation (10)
Was spread on an aqueous solution containing 11.4 mg / l to form an ion complex at the air-water interface.

FIG. 1 shows a surface pressure-occupied area curve (π-A curve) of the formed ion complex thin film. As is clear from FIG. 1, the surface pressure sharply rises in a region of about 0.5 nm ² / repeated unit or more, and it can be seen that a monomolecular film is formed at the air-water interface.

Next, a surface pressure of 30 m was obtained by the vertical accumulation method.
At N / m, the polyion complex thin film was transferred onto a calcium fluoride plate, a porous fluorocarbon film and a silicon wafer, respectively. Regardless of which substrate was used, the monomolecular film was accumulated on the substrate surface in both the lowering step when the substrate was immersed in the aqueous solution and the rising step when the substrate was pulled up from the aqueous solution, and a Y-type cumulative film was obtained.

In order to convert the salt of the carboxylic acid and the primary amine in the formed thin film into a covalent bond, the condensation reaction is promoted by heating the thin film formed on the substrate to 180 ° C. under reduced pressure for 10 hours. Was. 23 on calcium fluoride substrate
As shown in FIG. 2, the FT-IR spectrum of the thin film having accumulated layers was different before and after the heat treatment. That is, FIG.
, The ammonium salt of a carboxyl group and a primary amine is converted into an imide bond by heat treatment,
It is confirmed that absorption occurs at m ^-1 . Note that FIG.
Is the value obtained by integrating the results of 200 measurements by the transmission method.

When the thin film obtained by accumulating the four thin films on the porous fluorocarbon film was observed by a scanning electron microscope before the heat treatment, the thin film had a structure shown in FIG. In addition,
The measurement was performed on a thin film subjected to Pt-Pd sputtering. From FIG. 3, it can be seen that the pores present in the substrate are completely covered with the thin film.

The thin film obtained by accumulating six layers on the porous fluorocarbon film had the structure shown in FIG. 4 after the heat treatment.
FIG. 4 also shows that the pores present on the substrate are completely covered with the thin film. When the film thickness of the thin film accumulated on the silicon wafer was measured, the film thickness per layer was 44.9 ° before the heat treatment and 21.8 ° after the heat treatment.

Example 2: Using a water-soluble polyanion having a repeating unit of the structural formula (11), the ratio of one molecule of the amphiphilic substance (8) to two repeating units of the water-soluble polyanion (11) A developing solution containing the amphiphile (8) and the water-soluble polyanion (11) was prepared. This developing solution was spread on an aqueous solution containing a water-soluble polycation (10) in the same manner as in Example 1, and the polyion complex thin film formed at the air-water interface was transferred to a fluorocarbon substrate, and six layers were accumulated on the substrate surface. A thin film was prepared.

Embedded image The obtained thin film had a structure shown in FIG. 5 before the heat treatment. Also in this case, the pores existing in the substrate are:
It was completely covered with a thin film.

Example 3 A water-soluble polyanion having a repeating unit represented by the structural formula (12) was used and developed on an aqueous solution containing a water-soluble polycation (10) in the same manner as in Example 1 to form an air-water interface. The obtained polyion complex thin film was transferred to a fluorocarbon substrate, and a thin film in which four layers were accumulated on the substrate surface was produced. The obtained thin film had a structure shown in FIG. 6 before the heat treatment. Also in this case, the pores existing in the substrate were completely covered with the thin film.

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Example 4: Using a water-soluble polyanion having a repeating unit represented by the structural formula (13), it was developed on an aqueous solution containing a water-soluble polycation (10) in the same manner as in Example 1 to form an air-water interface. The obtained polyion complex thin film was transferred to a fluorocarbon substrate, and a thin film in which four layers were accumulated on the substrate surface was produced. The obtained thin film had a structure shown in FIG. 7 before the heat treatment. Also in this case, the pores of the substrate were completely covered with the thin film.

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Example 5: Using a water-soluble polyanion having a repeating unit represented by the structural formula (14), a polyion complex thin film formed at the air-water interface was transferred to a fluorocarbon substrate in the same manner as in Example 1, and was applied to the substrate surface. A thin film in which six layers were accumulated was produced. The obtained thin film had a structure shown in FIG. 8 before the heat treatment. Also in this case, the pores of the substrate were completely covered with the thin film.

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Example 6: Using a water-soluble polyanion having a repeating unit represented by the structural formula (15), a polyion complex thin film formed at an air-water interface was transferred to a fluorocarbon substrate in the same manner as in Example 1, and was applied to the surface of the substrate. A thin film in which four layers were accumulated was produced. The obtained thin film had a structure shown in FIG. 9 before the heat treatment. Also in this case, the pores of the substrate were completely covered with the thin film.

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Example 7: An amphipathic substance having the structural formula (16) was used at a ratio of one molecule of the amphipathic substance (16) to one repeating unit of the water-soluble polycation (10). , Amphiphile (16) and water-soluble polycation (1
0) was dissolved in a 2: 3 mixed solvent of isopropyl alcohol and benzene to prepare a developing solution. 30 to an aqueous solution containing 34.8 mg / l of a water-soluble polyanion (9)
The developing solution was developed at ℃ to form an ion complex at the air-water interface.

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The ion complex thin film formed at the air / water interface was transferred to a fluorocarbon substrate in the same manner as in Example 1, and six thin films were formed on the substrate. When the state of the obtained thin film before the heat treatment was observed with a scanning electron microscope, it had the structure shown in FIG. FIG. 10 shows that the pores on the substrate surface are completely covered with the thin film.

Example 8 Using an amphiphilic substance having the structural formula (17), an ion complex thin film formed at the air-water interface was transferred to a fluorocarbon substrate in the same manner as in Example 7, and six layers were formed on the substrate. An accumulated thin film was prepared. The obtained thin film had a structure shown in FIG. 11 before the heat treatment. FIG. 11 shows that the pores on the substrate surface are completely covered with the thin film. Further, this thin film is subjected to 1
After heating at 80 ° C. for 10 hours and immersing in chloroform for 6 hours, the structure shown in FIG. 12 was obtained. The thin film after the heat treatment also completely covered the pores on the substrate surface.

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Example 9: An amphipathic substance having the structural formula (18) was used, and the amount of the amphiphilic substance (18) was one molecule per 15 repeating units of the water-soluble polycation (10). , An amphiphile (16) and a water-soluble polycation (10) in a ratio of 2: 3 of isopropyl alcohol and benzene.
A developing solution was prepared by dissolving in a mixed solvent.

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The developing solution was spread at 30 ° C. in an aqueous solution containing a water-soluble polyanion (9) in the same manner as in Example 7, and the ion complex thin film formed at the air-water interface was transferred to a fluorocarbon substrate, and two layers were formed on the substrate. An accumulated thin film was prepared. After heat treatment of the obtained thin film, chloroform
Soaked for hours. The heat-treated thin film had the structure shown in FIG. FIG. 13 shows that the pores on the substrate surface are completely covered with the thin film.

[0039]

As described above, in the present invention, an ion complex of a water-soluble polyanion and a water-soluble polycation is formed by utilizing a reaction field formed by a molecular assembly of an amphipathic substance. By transferring the ion complex onto a substrate and forming a crosslink by a covalent bond, a crosslinked polymer thin film having excellent strength and stability is manufactured. According to this method, restrictions on usable water-soluble polyanions and water-soluble polycations are relaxed, and it becomes possible to produce a thin film having functions according to various requirements.

[Brief description of the drawings]

FIG. 1 is a surface pressure-molecule occupation area curve of an ion complex thin film formed at an air-water interface in Example 1.

FIG. 2 is an FT-IR spectrum of a thin film produced in Example 1 before and after a heat treatment.

FIG. 3 shows a structure of a thin film before heat treatment manufactured in Example 1.

FIG. 4 shows the structure of a thin film after heat treatment produced in Example 1.

FIG. 5 shows a structure of a thin film before heat treatment manufactured in Example 2.

FIG. 6 shows the structure of a thin film before heat treatment manufactured in Example 3.

FIG. 7 shows the structure of a thin film before heat treatment manufactured in Example 4.

FIG. 8 shows a structure of a thin film before heat treatment manufactured in Example 5.

FIG. 9 shows a structure of a thin film before heat treatment manufactured in Example 6.

FIG. 10 shows a structure of a thin film before heat treatment manufactured in Example 7.

FIG. 11 shows a structure of a thin film before heat treatment manufactured in Example 8.

FIG. 12 shows the structure of a thin film after heat treatment produced in Example 8.

FIG. 13 shows the structure of a thin film after heat treatment produced in Example 9.

Continuation of front page (56) References JP-A-4-15231 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18-5/22

Claims (3)

(57) [Claims] 1. An ion complex comprising an amphiphilic substance, a water-soluble polyanion, and a water-soluble polycation is formed at an air-water interface, and the ion complex is transferred onto a substrate. A method for producing a cross-linked polymer thin film, comprising forming a cross-link by a covalent bond between the polymer film and 2. The method for producing a crosslinked polymer thin film according to claim 1, wherein the ionic group of the polyanion is a carboxyl group and the ionic group of the polycation is a primary or secondary amine. 3. The method for producing a crosslinked polymer thin film according to claim 1, wherein the covalent bond is a condensation reaction between a carboxylic acid and an amine.