JPH0726060B2 - Method for producing organic silicon thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a porous organic silicon thin film whose structure is controlled at the molecular level.

[Prior Art] Conventionally, as a substance used for substance separation or a carrier, for example, porous silica gel made of sodium silicate,
There are porous glass, layered polysilicate, etc. manufactured by utilizing the phase separation property of borosilicate glass, or manufactured by a sintering method or a sol-gel method. There is also an example in which aluminosilicate zeolite or a layered clay mineral such as montmorillonite is used as a related substance having a similar pore structure. Since these substances are in the form of powder, they are used by being granulated and formed into particles, plates, or lumps. But,
Since it is difficult to form a thin film, its handling becomes troublesome.

Therefore, a thin film with a pore structure of molecular order is used for gas separation of hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide, methane, etc., and liquid separation of alcohol, water, etc. by utilizing its microscopic structure. It has been studied and developed for use. It is also known to use the surface hydroxyl group of the thin film or the surface active group introduced by chemically modifying the hydroxyl group to adsorb and separate metal ions or the like and use the thin film for an ion exchanger or the like. Further, an example in which a thin film is used as a carrier for catalysts, enzymes, microorganisms and the like by utilizing the pore structure and surface active groups has been reported.

In any of these applications, it is necessary to control the fine structure (morphology) at the molecular level and the orientation of the surface active groups in order to effectively exert the action resulting from the pore structure. Further, in order to increase the permeation amount of the substance to be separated in the substance separation membrane and the reaction substance in the carrier such as the catalyst, it is required to reduce the membrane resistance by maintaining the membrane strength and reducing the membrane thickness. It

For example, making a thin film of polydimethylsiloxane polymer and using it as a gas separation membrane is a "new functional membrane".
(Published by Kodansha in 1984, written by Shimizu, Saito and Nakagawa) 97th
Reported on page 100. However, this thin film has a thickness of 2
If the thickness is 5 μm or less, pinholes are likely to be formed and the film strength is also reduced. Further, the production of a thin film by the sol-gel method is also reported in "Science of the sol-gel method" (published by Agne Jofu Co., Ltd., 1988, by Sakuhana Seo), pp. 85-153. In this case, a hydrolysis solution of an alkoxysilane substance is prepared, the solution is applied to a substrate, and a gel coating film is formed by heat treatment to form an organosilicon thin film. At this time, a porous body is used as the substrate as the separation membrane.

[Problems to be Solved by the Invention]

When an organic silicon thin film is manufactured by a conventional sol-gel method, solvent evaporation or siloxane bond (Si-O
The contraction of the volume occurs along with the crosslinking reaction due to the formation of -Si). Therefore, cracks are likely to occur, the structure becomes brittle, and it is difficult to form a thin film having a uniform structure and film thickness. From this point, it is considered impossible to manufacture a film-like film by the sol-gel method.

In addition, since the substrate and the support film are used, the adhesion between the coating film and the substrate and the mechanical strength required to withstand the volume shrinkage during film formation are required for the substrate. Occurs. The thickness of the coating film is limited to 10 to 20 μm when it is thick and about 0.1 μm when it is thin. Such a thick film cannot be a thin film whose structure can be controlled at the molecular level.

Moreover, since the organic silicon thin film formed by the sol-gel method is a three-dimensional crosslinked body, it has a pore size of about 10 to 200Å and an amorphous pore structure. It is difficult to increase the pore size beyond this, and therefore it is not suitable as a carrier for catalysts and the like. Further, it is not possible to control the orientation of the surface active groups.

As described above, in the conventional sol-gel method, it is impossible to control the film thickness of the organic silicon thin film, the pore structure, the orientation of the surface active groups, etc. at the molecular level.

Therefore, the present invention utilizes the aggregated state of the amphipathic substance present in the solvent and forms a film from a liquid containing this amphipathic substance and an alkoxysilane substance as a thin film precursor by a developing method. The purpose of the present invention is to produce an organic silicon thin film capable of controlling the structure at the molecular level.

[Means for Solving the Problems]

In the present invention, a developing solution containing an amphipathic substance in which a polar group and a hydrophobic group are added to both ends of a molecule and an alkoxysilane substance is prepared, and the developing solution is spread on the surface of the substrate and formed on the substrate. By removing the solvent from the formed liquid film, an organic silicon thin film containing an amphipathic substance is prepared. This organic silicon thin film is, as it is, or after being subjected to a chemical treatment,
Used by extracting amphiphiles.

The amphipathic substance used in the present invention is a compound having both a polar group and a hydrophobic group in the same molecule at the same time. Examples of polar groups include sulfonates, sulfates, ammonium salts, polyamine salts, carboxylates, sulfonyl salts, phosphates, phosphonates, phosphonium salts, polyethers, alcohols, sugar residues, etc. Polyols and combinations of these groups can be used. On the other hand, as the hydrophobic group, an alkyl group, an alkylallyl group, an alicyclic group, a condensed polycyclic group and a combination of these groups can be used.

As the alkoxysilane substance serving as a precursor of the organic silicon thin film, a compound containing a SiOR group (RO: alkoxy group or acyloxy group) is used. This SiOR group undergoes a hydrolysis reaction to form a silanol group SiOH, and a siloxane bond Si- is formed by a polycondensation reaction between SiOHs or between SiOHs and SiORs.
The formation of O-Si crosslinks to form a thin film.

The reaction at this time can be represented by an equation, for example, as follows.

Hydrolysis reaction Polycondensation reaction Therefore, in order to form a thin film, the precursor alkoxysilane material should be at least 3
It is necessary that at least one alkoxy group OR is present in one molecule. This can be expressed by a general formula as follows.

R ¹ mSi (OR) _4- m (m: 0 or 1) (N = 2, p = 1 or n = 3, p = 0) and their hydrolyzed polycondensates Note that R in the above formula must be hydrolyzed to generate a silanol group. Are methyl, ethyl, propyl, butyl, acetoxy, acetylacetonato, etc.

The above alkoxysilane compounds may be used alone or in combination of two or more. It is also possible to add an alkoxysilane compound with low crosslinkability to the above-mentioned alkoxysilane for the purpose of modification by organic chains, increase in porosity by decreasing crosslink density, sealing of residual SiOH, SiOR, etc. Is. Examples of the low-crosslinking alkoxysilane compound used include the following.

However, R ⁴ , R ⁵ and R ⁶ may be the same or different and R ¹
You can choose from the same groups as. In this case, R ⁴ R ⁵
Chlorosilanes such as SiCl ₂ , R ⁴ R ⁵ R ⁶ SiCl may be used.

In addition, R ¹ in the above formula is methyl, ethyl, propyl, butyl, octyl, octadecyl, phenyl, naphthyl, fluoroalkyl, vinyl, allyl, γ-chloropropyl, γ-aminopropyl, N- (β-amino. Ethyl) -γ-aminopropyl, γ-mercaptopropyl,
γ-glycidoxypropyl, γ-methacryloxypropyl and the like.

Further, R ² includes the following.

_{-CH 2 CH 2 -, - CH} 2 CH 2 CH 2 -, - CH 2 CH 2 CH 2 CH 2 -, -CH 2 CH 2 OCH 2 CH 2 -, - CH 2 CH 2 CH 2 OCH 2 CH 2 CH _2- , It is also possible to add an alkoxy compound of a metal element M other than silicon, a carboxy compound, a halogen compound, a nitric acid compound or the like to the alkoxysilane substance.

As will be described later, since the developing solution is mainly an aqueous solution, some of these compounds are highly hydrolyzable and precipitate during the preparation of the developing solution. Therefore, the added amount varies depending on the compound used and is difficult to uniquely determine. Further, those which are hardly hydrolyzable and do not form Si-OM bonds cannot be used. In this respect, the metal alkoxy compound M (OR) n, which is generally highly compatible, is suitable for the alkoxysilane substance. However,
Since metal alkoxy compounds other than silicon have high hydrolyzability, when a metal alkoxy compound alone is added to a developing solution, a precipitate may be generated. In that case, prior to the preparation of the developing solution, it is preferable that the alkoxysilane substance and the metal alkoxy compound are mixed in a predetermined amount to prepare an adduct, which is used as a raw material. Incidentally. There are no restrictions on the metal element M that can be added to Si, and there are alkoxy compounds for most of the metal element M.

From the viewpoint of suppressing hydrolyzability, R (M (OR) n) generally preferably has a large number of carbon atoms. Further, various carboxyl compounds M (OOCR ') shown below are also preferable compounds.

Ti (OC ₄ H ₉ ) ₄ , Ti (OC ₃ H ₇ ) (OOCC ₁₇ H ₃₅ ) ₃ , Ti (OC ₃ H ₇ ) (OC (CH ₃ ) CHCOCH ₃ ) ₂ , Zr (OC ₄ H ₉ ) _{4 , ZrO (OOCCH 3) 2,} ZrOCl 2, VO (OC 4 H 9) 3, Al (OOCH) 3, Al (OOCCH 3) 3, Al (OC 3 H 7) 3, Al (OC (CH 3) CHCOOC _{The 2} H ₅ ) ₃ developing solution is prepared by dissolving or dispersing a predetermined amount of an amphipathic substance and an alkoxysilane substance in a solvent. Water is often used as the solvent, but it is also possible to add an organic solvent. However, a minimum amount of water is required to hydrolyze SiOR. Alkoxysilane substances are poorly water-soluble except for a part thereof, and in the case of an aqueous solution, they are uniformly dissolved or dispersed in a developing solution as SiOH is generated by hydrolysis of SiOR groups. Therefore, a small amount of an acidic substance or a basic substance may be added to accelerate the hydrolysis of the SiOR group.

The substrate on which the developing solution is spread includes a glass substrate, a quartz plate, a fluoropore, a graphite plate, a silicon substrate, a dense polymer film, a porous polymer film and the like. The surface of the substrate may be hydrophilized or hydrophobized depending on the type of developing solution. For example, it is also effective to hydrophilize a part of the substrate surface and hydrophobize the remaining surface part so that the developing solution is spread on a predetermined area on the substrate surface.

The solvent is removed from the developing solution spread on the substrate, and the growth of siloxane bonds forms an organic silicon thin film. At this time, it is preferable to gradually remove the solvent in order to uniformly promote the growth of siloxane bonds and to ensure the regularity of the molecular assembly of the amphipathic substance.

The organic silicon thin film containing an amphipathic substance obtained after removing the solvent (hereinafter, simply referred to as a thin film) has a self-supporting property that can be used as it is. However, it is also possible to carry out further chemical treatment or heat treatment. This chemical treatment involves residual SiOR and SiOH.
In order to further promote the hydrolysis polycondensation reaction of, the treatment using an acidic substance or a basic substance is listed.

The thin film is treated by directly immersing the thin film in a liquid or solution of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, ammonia, amine, sodium hydroxide or the like. A method of exposing the thin film to the vapor of these acidic or basic substances using a closed container is also effective. In addition, unreacted in the thin film
R ⁴ R ⁵ R ⁶ Si (OR), R ⁴ R ⁵ R to deactivate SiOR and SiOH
Liquid ⁶ SiCl or hexamethyldisilazane silazane compounds, also treated in the same manner with a solution or vapor.

It is possible to perform the above-mentioned treatment after extracting the amphipathic substance with an extractant, but in order to sufficiently reflect the ordered structure of the amphipathic substance in the organic silicon thin film, the amphipathic substance is The processing in the state of including is effective.

The thin film produced in this manner becomes an organic silicon thin film whose structure is controlled at the molecular level by extracting and removing the amphipathic substance with an extractant selected according to the type of the amphipathic substance.

[Action]

The present inventors have focused on amphipathic substances forming various molecular assemblies, and when applying the sol-gel method with a regular molecular assembly formed by these amphiphiles as a reaction field, at the molecular level. The present invention has been completed as a result of earnest research, considering that it is possible to manufacture an organic silicon thin film having a controlled structure.

An amphipathic compound having a polar group and a hydrophobic group at both ends of the molecule, when dissolved or dispersed in a medium such as an aqueous solution,
It is known to form spherical, disc-shaped, rod-shaped, cylindrical, or lamellar molecular aggregates (for example, "Molecular aggregates-its organization and function", edited by The Chemical Society of Japan, 1983, Ed. See page 106). Further, some kind of amphipathic substance forms a molecular assembly having a bilayer membrane structure similar to that of a biological membrane. The amphipathic substance forming the bilayer membrane can be obtained not only as a water medium, but can also be cast on a transparent self-supporting cast film by gradually removing water after being spread on a solid substrate. The regular bilayer film structure is maintained even in the obtained cast film. On the other hand, it is difficult to mold a self-supporting cast film with an amphipathic substance having no ability to form a bilayer film, a so-called general surfactant.

The ability to form an organic silicon thin film varies depending on the type of amphipathic substance used. That is, in a general surfactant having no ability to form a bilayer film, when the amount of the alkoxysilane substance is small with respect to the amphipathic substance (for example, 3 times or less mol), it is brittle and easily cracked even if it is developed, and the self It does not easily become a thin film with supportive properties.

On the other hand, when an amphipathic substance having a self-organizing property that takes a bilayer membrane structure similar to a biological membrane in an aqueous dispersion system is used,
It is possible to manufacture an organic silicon thin film with a film thickness at the molecular level.

Regarding the characteristics of the amphipathic substance having a bilayer structure and the reason why the ability to form a thin film is high, Japanese Patent Application No.
Since it is described in detail in No. 58889, it is omitted here, but in short, it is considered that the stability and regularity of the bilayer membrane structure are similar to the biological membrane.

The amphipathic compound forms a molecular aggregate such as a sphere, a disc, a rod, a cylinder, or a lamella when dissolved or dispersed in a medium such as an aqueous solution. The assembly mode or assembly form of this molecular assembly is determined by the affinity of the polar group or hydrophobic group constituting the amphipathic substance with the medium, and the molecular orientation based on the molecular structure of the hydrophobic group. This is because when an alkoxysilane substance is added, the alkoxysilane substance is hydrolyzed and dispersed in the medium, and is crosslinked and immobilized by a method in which a molecular assembly is used as a template.

Therefore, the pore structure of the organic silicon thin film produced by the method of the present invention reflects the morphology of the molecular aggregate formed by the amphipathic substance and has molecular level precision. Therefore, it is possible to control the morphology and size of the pores by appropriately selecting the amphipathic substance.

In particular, the use of a self-organizing amphipathic substance having a lamellar structure with high two-dimensional flatness makes it possible to form an ultrathin film at the molecular level. Further, the surface active group introduced by R ¹ Si or the like also has a regular orientation due to the interaction with the molecular assembly.

Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 - by dispersing a predetermined amount of CH ₃ Si (OCH _{3) 3} as Example 1 various amphiphiles 50mM and alkoxysilane material in pure water, and the various developing solution was prepared. This developing solution is dropped on a fluoropore surrounded by a cellulose acetate film frame as a substrate (hereinafter, simply referred to as fluoropore) or a glass petri dish,
Keep this in an atmosphere of temperature 25 ℃ and humidity 60% for 3 days,
The water content of the developing solution was evaporated. Then, the liquid film from which water was removed was sealed with ammonia gas in a closed container, and the temperature was adjusted to 20
The mixture was allowed to stand at ℃ for 1 week, and finally the amphipathic substance was extracted with chloroform or methanol to obtain an organic silicon thin film.

Observation of the obtained thin film with a scanning electron microscope (SEM) revealed that the structure with closed cells (Fig. 1) and the film with pores were layered in layers depending on the type of amphiphile and manufacturing conditions. Stuff (Fig. 2), woven fabric-entangled stuff (Fig. 3),
Various pore structures were obtained, such as a structure in which the capillary holes were three-dimensional or extended in the film surface direction.

Table 1 shows the manufacturing conditions at this time and the morphological characteristics of the obtained organic silicon thin film. The compounds in Table 1 are shown below by structural formulas. Of these, compounds 1 and 2 are ordinary surfactants, and compounds 3 to 5 are amphipathic substances capable of forming a bilayer.

Compound 1 Compound 2 CH ₃ (CH ₂ ) ₁₀ O (CH ₂ CH ₂ O) ₉ H Compound 3 Compound 4 Compound 5 In addition, as an example of no addition of amphiphile, CH ₃ Si (OCH ₃ )
_A solution obtained by adding 0.1% by weight of ammonia water to the 5% by weight aqueous solution of ₃ was used to dry the liquid film by the same method. In this case, the state after drying was in the form of flakes and no pores were observed.

Since the pore structure of the obtained thin film can be changed according to the kind of the amphipathic substance used and the production conditions in this way, the organic silicon thin film has a function corresponding to various purposes.

For example, in the case of having the closed cells shown in FIG. 1, when the functional substance such as a dye is put in the bubbles, the dispersion form of the functional substance is at the molecular level, so that the excellent fluorescent characteristics,
It is used as an optical material having a light absorbing property or a light hole burning effect. In addition, in the thin film having the pore structure arranged in layers as shown in FIG. 2, the film thickness of one layer is the molecular thickness, so that the film resistance is small and the substance permeation amount is large, and the surface orientation of the active groups is large. Therefore, it is used as a material separation material for selective gas separation, ion exchange, adsorption / desorption, etc. Further, in the thin film in which the pores are arranged in a woven fabric shape as shown in FIG. 3, since it has a large-diameter space of the order of μm or more,
It is used not only as a catalyst but also as a carrier for immobilizing enzymes and microorganisms. Furthermore, in thin films with extended molecular size capillary pores,
It is used as a filtration material for molecules or molecular aggregates, bacteria, etc., or as a membrane reactor in which a catalyst is supported and the reaction is controlled by utilizing the permeation selectivity of the reaction substrate or reaction product.

-Example 2-The above-mentioned compound 4 was used as an amphipathic substance. Then, a developing solution was prepared by adding an alkoxysilane substance in a 3-fold molar equivalent amount to 50 mM of Compound 4. The alkoxysilane materials used here are as follows.

NH ₂ CH ₂ CH ₂ CH ₂ Si (OCH ₃ ) _{3 CH 3 (CH 2) 17 Si} (OCH 3) 3 CF 3 (CF 2) 7 CH 2 CH 2 Si (OC 2 H 5) 3 Si (OC 2 H 5) 4 in the same manner these developing solution as in Example 1 The method was applied to obtain an organic silicon thin film. In each case, the obtained organic silicon thin film was in the form of a film, and the pore structure observed by SEM was in the form of a multilayer film.

- addition of Example _{3- CH 3 Si (OCH 3)} 3 1/10 parts by weight of _{Ti (OC 4 H 9) 4} , to yield a clear slightly yellow liquid with stirring and mixing. This liquid was converted to Si in terms of Si for 50 mM of the amphipathic substance of compound 3.
A developing solution was prepared by dispersing it in pure water at a double molar ratio. Then, it was developed in the same manner as in Example 1 to evaporate water, treated with ammonia, and then extracted with amphiphile with chloroform to obtain a white film. In addition, Zr (OC ₄ H
₉ ) For ₄ as well, a white film was similarly obtained in a system in which 1/10 parts by weight was added to CH ₃ Si (OCH ₃ ).

The organic silicon thin films thus obtained are all SE
As a result of M observation, it had a layered pore structure.

〔The invention's effect〕

As described above, in the present invention, a regular molecular assembly formed when a liquid containing an amphipathic substance is spread on a substrate is used as a reaction field, and the precursor alkoxysilane is used. An organic silicon thin film is made from a compound. According to this method, a thin film having high orientation and capable of controlling the structure at the molecular level can be obtained. The thin film thus obtained exerts an excellent function as a substance separation membrane, various carriers and the like due to its structure.

[Brief description of drawings]

Each of the figures is a microstructure photograph of the crystal structure of the thin film produced according to the present invention. FIG. 1 is a thin film having closed cells, FIG. 2 is a thin film in which pores are arranged in layers, and FIG. The figure shows a thin film in which the pores are woven.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C09D 183/02 PMP 183/14 // C08L 83:04

Claims (4)

[Claims] 1. A sulfonate, a sulfate, an ammonium salt,
Polyamine salt, carboxylate, sulfonyl salt, phosphate, phosphonate, phosphonium salt, polyether acid,
A polar group selected from alcohols, polyols containing sugar residues, and combinations thereof, and an alkyl group having 8 to 22 carbon atoms, an alkylallyl group, an alicyclic group, a condensed polycyclic group, and combinations thereof. A developing solution containing an amphipathic substance having hydrophobic groups added to both ends of the molecule and an alkoxysilane substance having at least three or more alkoxy groups bonded to Si atoms in one molecule is prepared. A method for producing an organic silicon thin film, comprising: spreading a liquid on a substrate surface and then removing a solvent from the liquid film on the substrate. 2. A liquid film after removing the solvent according to claim 1, after being subjected to a chemical treatment or a thermal treatment for accelerating the hydrolytic polycondensation reaction of residual SiOR, SiOH, etc. A method for producing an organic silicon thin film, which comprises extracting an amphipathic substance with. 3. A method for producing an organic silicon thin film, wherein the developing solution according to claim 1 further contains a metal alkoxy substance other than silicon capable of forming a metalloxane bond. 4. A method for producing an organic silicon thin film, wherein the amphipathic substance according to claim 1 is capable of forming a bilayer film.