JPH0768361B2 - Method for producing thin film or flaky material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an ultrathin film or flaky material having a basic thickness on a molecular level.

[Conventional technology]

Research on organic and inorganic ultra-thin films has been conducted in various fields, focusing on their wide range of functions. For example, a semiconductor substrate required for manufacturing electronic parts needs to have extremely fine and precise adjustment of a conductive region, an insulating region, a doping region, etc. on an atomic or molecular scale as the degree of integration increases. Become. In addition, in the case of oxygen / nitrogen separation membranes and reverse osmosis membranes used for seawater desalination,
It is known that the ultra-thin layer on the surface influences the performance. Alternatively, also in a biocompatible material such as an artificial blood vessel, the molecular layer on the outermost surface of the material is related to the function.

[Problems to be Solved by the Invention]

By the way, vacuum deposition CVD, PV
Dry methods such as D and ion plating are known. According to these methods, a thin film having a film thickness on the order of several μm can be manufactured relatively easily. However, if it is attempted to manufacture a thin film having a smaller atomic or molecular level film thickness than that, the economical burden on the apparatus itself increases, and the productivity is not necessarily good. As a result, the obtained thin film becomes expensive.

As a wet method, the LB method is known in which a film developed on a sub-phase such as a water surface is transferred to an appropriate substrate to form a single-layer or multi-layer ultra-thin film. This method is inferior in productivity because it is necessary to repeat the process many times until the required film thickness is obtained. Further, when a polymer thin film is produced by the water surface development method, productivity is improved, but precise control of the structure is difficult.

As a method for producing an organic thin film, it is also known to introduce a monomer between layers of an inorganic substance having a layered structure such as clay mineral and polymerize the monomer between the layers. However, in this method, it is difficult to introduce the monomer with a uniform distribution between the layers of the inorganic substance having a layered structure. Moreover, it is difficult to isolate the polymer obtained by the polymerization from the layers. Therefore, this method has not been widely adopted.

Furthermore, the sol-gel method is often adopted as a means for producing an inorganic substance thin film. For example, a gel coating film is formed by adding alcohol or water to a metal alkoxide, immersing the substrate in this solution, pulling it up, and then heating it. Also in this case, the film thickness is about 0.05 μm or more, and the film thickness cannot be controlled at the molecular level.

The present inventors have continued to study synthetic bilayer membranes for the past dozen years. The synthetic bilayer membrane is similar to the bilayer membrane of biological lipids in most aspects such as structure, morphology, and physical properties, and the molecular design of many membrane substances is possible. Therefore, it is expected as an ultrathin film having a precise structure. It was clarified that this synthetic bilayer membrane can be obtained not only as an aqueous dispersion but also as a transparent cast film having self-supporting property by gradually removing water after being spread on a solid substrate. The obtained cast film maintains a regular bilayer membrane structure, and research as a functional material utilizing its properties is being actively conducted widely not only by the present inventor but also in Japan and overseas.

It is an object of the present invention to take these studies one step further to produce a completely novel organic or inorganic ultra-thin film or flaky material by utilizing the ordered structure of a bilayer membrane cast film.

[Means for Solving the Problems]

In order to achieve the object, the present invention prepares a developing solution containing an amphipathic substance having a polar group and a hydrophobic group added to both ends of a molecule and a soluble polymer substance or a polymerization precursor, and the developing solution. By developing a liquid on the surface of the substrate and removing the solvent from the developing liquid, a multi-layered structure in which the soluble polymer substance or the polymerization precursor is distributed between the layers of the bilayer film made of the amphipathic substance It is characterized in that a bilayer film is prepared and then the amphipathic substance is removed from the film having the multilayer structure.

FIG. 1 is a molecular schematic diagram of an amphipathic substance used in the present invention. FIG. 1A shows a polar group 2 at the end of the molecular skeleton 1.
However, a hydrophobic group 3 such as an alkyl group is added to each of the other ends. A chain serving as a spacer 4 is introduced between the molecular skeleton 1 and the polar group 2 as needed. In this case, it is necessary for the molecular skeleton 1 to have a hard skeleton such as an arylene group in order to separate the amphipathic substance from the developing solution with high orientation.

As the arylene group used as the rigid molecular skeleton 1,
Without limiting the present invention, the following are exemplified.

The polar group 2 added to the molecular skeleton 1 includes a sulfonate, a sulfate, an ammonium salt, a polyamine salt, a carboxylate, a sulfonate, a phosphate, a phosphonate, a phosphonium salt, a polyether, and a sugar residue. Polyols, including groups and the like, and combinations of these groups can be used.

As the hydrophobic group 3, an alkyl group having 6 to 15 carbon atoms in the straight chain portion, a fluoroalkyl group and a combination thereof,
Or a portion thereof is a double bond, an alicyclic group, -S _i O -, - CONH
There are those substituted with-, -COO-, -O-, -S-, etc.

In FIGS. 1B and 1C, two and three hydrophobic groups 7 are added to the polar group 2 via connectors 5 and 6, respectively. Further, a chain serving as a spacer 4 is introduced between the connectors 5 and 6 and the polar group 2 as needed. The hydrophobic group 7 in this case, an alkyl group having carbon atoms of straight chain moiety is 10 to 22, a fluoroalkyl group, and combinations thereof, or a portion thereof is a double bond, an alicyclic group, -S _i O-, −CONH−, −COO
There are those substituted with-, -O-, -S-, etc.

The connector 5 connects the two hydrophobic groups 7 and the polar group 2, and is a trifunctional unit such as a disubstituted amide group, a glutamic acid residue, an aspartic acid residue, and a glycerin unit.
The connector 6 connects the three hydrophobic groups 7 and the polar group 2, and is a tetrafunctional unit such as a treethanolamine group and a trishydroxymethylaminomethane unit.

These molecular skeleton 1, polar group 2, hydrophobic group 3, 7, spacer 4 and connectors 5, 6 have solubility and dispersibility in developing solvent, affinity for polymer materials for thin film formation and polymerization precursor, and formation of multilayer structure. It is set in consideration of Noh, etc.

As described above, the amphipathic substance having the polar group 2 and the hydrophobic groups 1, 3, and 7 forms a multilayer film based on self-organization. It is well known that a general surfactant or the like forms a liquid crystal aggregate in a concentrated state. These liquid crystals are so-called "stable phases" that are thermodynamically treated, and this state is maintained by the infinite lattice structure of the liquid crystal lamella. That is, it has been recognized that "lattice force" is the main factor that maintains the structure.

On the other hand, an amphipathic compound having a self-organizing property is one that can form a bilayer film structure when dissolved or dispersed in a medium, without depending on the lattice force. is there. The amphipathic substances having such characteristics belong to the type of molecular structure as shown in FIG. 1, but several hundred kinds of substances such as biological lipids and synthetic membrane compounds are known. For example, regarding the group of single-chain, double-chain, and triple-chain compounds mainly having an ammonium group as the polar group 2, the present inventor has described “DSC Studies of the Phase Tra
nsition Behavior of Synethetic Bilayer Membranes P
art I. Bilayer Membranes of Double-Chain Amphiphil
es "(published by Faculty of Engineering, Kyushu University in 1986), pages 221-243 and" Part II Bilayer Membranes of Single-Chein and T "
riple-Chain Amphiphiles "(published by Faculty of Engineering, Kyushu University, 1986), pages 245-263. However, the film-forming substance used in the present invention is not limited to those reported in these documents.

On the other hand, as the substance formed in the ultra-thin film between the layers of the bilayer film, various substances are selected from organic substances, inorganic substances and the like according to the kind of the thin film to be manufactured. Specifically, the soluble polymer substance includes polysaccharides such as starch, nucleic acids, biopolymers such as linear polypeptides, polyvinyl alcohol, polyacrylamide, polyamic acid, polyacrylic acid,
It includes hydrophilic polymers and copolymers such as polyvinylamine and polyether, hydrophobic polymers and copolymers such as polymethyl acrylate and polyvinyl acetate, and inorganic polymers such as siloxane polymers and polyphosphazene derivatives.

After combining with these polymeric substances to form a multilayer bilayer membrane structure, only the amphipathic substance is extracted and removed using a suitable solvent. At this time, if necessary, the amphipathic substance can be extracted and removed after treatments such as solubility reduction by chemical treatment, branching, increase in polymerization degree, insolubilization by crosslinking, and the like.

Examples of the polymerization precursor include vinyl monomers, non-conjugated dienes, polyfunctional monomers and the like, which are insolubilized by polymerization or have a significantly lower solubility than amphiphiles.
Further, a coordination compound which is insolubilized by the formation of a metal chelate, a system which is polymerized and insolubilized by hydrolysis (alkoxysilane, FeCl ₂ , FeCl _3, etc.) are also useful as precursors.
In particular, with regard to the latter, most of the starting materials for the method for producing ceramics using the sol-gel method, such as metal alkoxides, metal carboxylates, metal nitrates, metal oxychlorides, and metal chlorides, can be used in the present invention.

As an example of the chemical treatment in the claims,
Water insolubilization due to neutralization with polyamic acid, formation of bridged structure by polymerization with non-conjugated diene, insolubilization with reaction of bis ligand and hexacoordinate metal ion in case of chelate formation, hydrolysis polymerization with acid or alkali for alkoxysilane Etc.

Substrates on which the developing solution is spread include glass substrates, quartz plates, fluoropores, graphite plates, Si substrates, dense polymer films, porous polymer films, and the like. The surface of the substrate may be hydrophilized or hydrophobized depending on the type of developing solution. For example, a part of the substrate surface is hydrophilized so that the developing solution is spread over a predetermined area on the substrate surface,
It is also effective to hydrophobize the remaining surface portion.

The solvent is removed from the developing solution spread on the substrate, and the bilayer film has a structure in which it is laminated in multiple layers. At this time, in order to secure the orientation of the bilayer film and the regularity of the multilayer structure, it is preferable to remove the solvent as gradually as possible. As the solvent, in many cases, water can be used, but when the polymer substance or polymerization precursor to be introduced is poorly soluble in water or is water-decomposable, a polar organic solvent is used. Good to use. In this case, an amphipathic compound such as fluorocarbon is preferably used as the bilayer film forming substance.

The bilayer membrane having a multilayer structure produced in this way is extracted with an extractant selected according to the type of amphiphile,
A thin film or flaky material formed by the material distributed between the layers is obtained.

[Action]

According to the present invention, a thin film having a film thickness on a molecular level and having structural units arranged in a two-dimensional plane is formed.
The formation of such a thin film is based on the affinity of the thin film-forming polymer or its polymerization precursor (hereinafter collectively referred to as "thin film material") with the polar group or hydrophobic group of the amphipathic substance. . Therefore, the thin film forming process inferred by the present inventor will be described below with reference to FIG. 2 schematically showing the thin film forming process. In the following description, water is used as the developing solution and hydrophilic one is used as the thin film material.

As shown in FIG. 2 (a), the amphipathic substance in the developing solution 21.
Most of 22 forms a bilayer film, and the thin film material 23 freely floats in the developing solution 21. The amphipathic substance 22 has a hydrophilic group and a hydrophobic group added to both ends.

When this developing solution 21 is developed on the substrate 24, the developing solution 21 becomes
As shown in FIG. 2B, the surface of the substrate 24 is raised. The substrate 24 is preferably one in which a part of the surface is hydrophilized in a ring shape and the other part is hydrophobized. The developing liquid 21 spread on the surface-treated substrate 24 in this way does not spread to the surrounding water-repellent portion 25, and the hydrophilic portion 26
It rides as a hemisphere on the water repellent part 25 separated by. Also,
The surface (gas-liquid interface) of the hemispherical developing solution 21 is a hydrophobic surface because the hydrophobic groups of the amphiphile 22 are oriented.

When this state is maintained, as shown in FIG. 2 (c), water gradually evaporates from the gas-liquid interface 27 of the developing liquid 21 and the drying progresses. With this drying, the concentration of the amphipathic substance 22 aggregate increases. At the interface, first a layer of amphiphile 22 is formed. At this time, since the hydrophilic group is aligned on the other side of the amphipathic substance 22, the hydrophilic thin film material 23 is collected there.
And, for this hydrophilic part, the amphipathic substance of the next layer
The hydrophilic surface of the bilayer membrane 28 of 22 is oriented. In this way, the developing solution 21 and the thin film material 23 are sandwiched between the hydrophilic groups of the amphipathic substance 22.

In the initial stage of drying, the developing solution 21 located far from the gas-liquid interface 27 is still in an undried state in which the aggregate of the amphipathic substance 22 and the thin film material 23 are freely floating. As the drying progresses further, the layer structure of the amphipathic substance 22 formed in the dry part 29 near the gas-liquid interface 27 grows, and the concentration of the aggregate of the amphipathic substance 22 in the undried part 30 becomes the gas-liquid interface. It becomes higher from the 27 side. Then, a new layer of the bilayer film is further oriented and the thin film material 23 is distributed between the hydrophilic groups. In this way, the bilayer film 28 grows sequentially and becomes thicker in the multilayer structure.

When the drying of the developing solution 21 is completed, as shown in FIG. 2D, a bilayer membrane 28 is stacked in multiple layers from the gas-liquid interface 27 to the substrate 24 to form a laminated structure. And each bilayer
The thin film material 23 is distributed between 28. This thin film material
The 23 layers are extremely thin with a thickness on the molecular level.

Next, the amphipathic substance 22 forming the bilayer film 28 is extracted from this laminated structure to obtain a multilayer thin film made of the thin film material 23. When a precursor is used as the thin film material 23, the precursor is converted into an insoluble thin film in the state shown in FIG. 2 (d).

This conversion means includes, for example, a method in which a monomer is cross-linked to form a polymer, a method in which a metal chloride is treated with a basic solution to form an oxide, and a method in which a polysubstituted ligand is required to form an insoluble metal complex. There are methods such as changing the pH and adding additives to lower the solubility of the polymer, and insolubilization by the interpolymer reaction, and a method corresponding to the type of precursor is selected.

The thin film or flaky material thus obtained becomes a layer having a thickness at the molecular level and a two-dimensional spread due to its production process, and there is substantially no dispersion of the thin film material 23 in the film thickness direction. Therefore, a thin film having an extremely large effective area per unit volume can be obtained. The main characteristics of this thin film or flaky material are as follows.

Since each layer has an ultra-thin film structure having a molecular level thickness, when it is used as a carrier for a metal catalyst or enzyme, it becomes an ultra-high density carrier having an extremely large effective area.

Due to the similar ultrathinness of each layer, the flux is expected to increase dramatically when used as a mass separation membrane. In addition, since the molecular structure has anisotropy, it exhibits a unique substance separation function.

Since it has a two-dimensional structure at the molecular level, it exhibits molecular structural anisotropy that cannot be seen in conventional films having a film thickness of several hundred angstroms or more. This produces new functions such as electrical, electronic, magnetic, and optical functional characteristics as well as material separability.

The bilayer membrane cast film acts as a molecular template for the newly formed interlayer thin film or interlayer thin piece. Therefore,
By using a bilayer unit having an appropriate molecular structure, it becomes possible to design the molecular structure and orientation of the interlayer product. This feature is extremely advantageous in any of the above-mentioned forms.

The LB method and the vacuum deposition method are conventional techniques for manufacturing a thin film whose structure can be controlled on a molecular or atomic scale, but since they are operations for each layer, their productivity is extremely poor. In contrast,
According to the method of the present invention, it is possible to produce a multilayer structure of ultra-thin films at the molecular level all at once. Therefore, the present invention is a technique that simultaneously satisfies the incompatible requirements of structure control on the molecular scale and high productivity.

In the explanation of FIG. 2, a hydrophilic material is used as the thin film material 23. However, the present invention is not limited to this, and a hydrophobic substance may be used as long as it has good dispersibility in the developing solution 21. Again, the hydrophobic material is collected between the polar layers of the stacked bilayers 28. Also from this cast film, the target thin film or flaky material can be obtained by extracting the amphipathic lipid by utilizing the difference in solubility.

〔Example〕

Various compounds having the following structures were used as amphipathic lipids.

On the other hand, among the thin film or flakes forming materials, soluble polymer substances include hydrophilic polymers and copolymers such as polyvinyl alcohol, modified polyacrylamide, polyamic acid, polyallylamine, polyvinylamine, polystyrene sulfonic acid, polyethylene oxide, and maleic anhydride. Hydrophobic polymers and copolymers such as copolymers, polymethyl acrylate and polyvinyl acetal were used.

Further, as the precursor, a compound containing a plurality of ligands such as acrylamide, acrylated oligoethylene glycol, acrylonitrile, epichlorohydrin, and bisacetylacetonatobenzene, a metal alkoxide, a metal carboxylate, and a metal chloride were used.

Then, 10 to 20 mM of the amphipathic substance and 10 to 20 mM of the soluble polymer substance or the polymerization precursor were dispersed in pure water as shown in Table 1 to prepare various developing solutions. This developing solution was dropped onto a glass substrate which had been surface-treated as shown in FIG. 2 (b). Then, this glass substrate was kept in an atmosphere having a temperature of 25 ° C. and a humidity of 60% for 3 days to evaporate the water content of the developing solution.
From the multilayer bilayer film thus formed, Example 1
In Example 7, chloroform was used as an extractant after polymerization after irradiation with ultraviolet rays. In Example 7, tetrahydridol was used as an extractant after treating the multilayer film with caustic soda. In Example 9, chloroform was used as an extractant after ammonia treatment and amphiphile was used. The volatile substance was removed by extraction.

When the cast film obtained was subjected to X-ray diffraction, the film thickness was 40-75.
It has been found that the intercalation substance has a bilayer film structure of Å and is distributed with high orientation.

[Effects of the Invention] As described above, in the present invention, when the amphipathic substance is separated from the developing solution, the polar group and the hydrophobic group of the lipid face each other between the respective layers, so that the polar The thin film-forming polymer substance or polymerization precursor is distributed between the groups or between the groups. Therefore, when lipids are extracted and removed from the obtained multilayer lipid bilayer membrane structure, a thin film in which the interlayer substances are aligned at the molecular level and which is substantially independent in the film thickness direction is produced. Then, when the characteristics of the substance forming the thin film are selected according to the purpose, it is used as a material having a novel function in various fields.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a molecular model showing an amphipathic lipid used in the present invention, and FIG. 2 is a diagram for sequentially explaining a thin film formation process. 1: Molecular skeleton, 2: Polar group 3,7: Hydrophobic chain, 4: Spacer 5,6: Connector 21: Developing solution, 22: Amphiphile (lipid) 23: Thin film material, 24: Substrate 25: Water repellent Part, 26: hydrophilic part 27: gas-liquid interface, 28: bilayer film 29: dried part, 30: undried part

Claims (1)

[Claims] 1. A developing solution containing an amphipathic substance having a polar group and a hydrophobic group at both ends of a molecule and a soluble polymer substance or a polymerization precursor is prepared, and the developing solution is spread on the surface of a substrate. Then, by removing the solvent from the developing solution, a bilayer membrane film having a multilayer structure in which the soluble polymer substance or the polymerization precursor is distributed between the layers of the bilayer membrane laminated film made of the amphipathic substance. A method for producing a thin film or flaky material, which is characterized in that the amphiphilic substance is extracted from the film having the multilayer structure as it is or after chemical treatment.