JP7223375B2 - Method for forming polymer brush layer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a polymer brush layer that can suitably form a polymer brush layer with a low coefficient of dynamic friction.

Conventionally, it has been known that a sliding surface having a polymer brush layer exhibits a low coefficient of friction. For example, Patent Document 1 discloses a sliding mechanism consisting of a block with a polymer brush film on a DLC-Si film and a ring with a similar polymer brush film.

Further, in Patent Document 2, a detailed study is made on a sliding mechanism between polymer brush layers using an atomic force microscope, and the brush layers are slid on a micro level measurable by an atomic force microscope. Techniques are disclosed.

JP 2012-56165 A Japanese Patent Application Laid-Open No. 2006-316169

However, the techniques of Patent Literature 1 and Patent Literature 2 have the following problems: the material used as the base material for forming the polymer brush layer is limited; the installation cost is extremely high; There is a problem that it is difficult to form a polymer brush layer having a practical area as a mechanism.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of forming a polymer brush layer that can suitably form a polymer brush layer with a low coefficient of dynamic friction.

As a result of intensive research to achieve the above object, the present inventors used a solution or dispersion obtained by mixing or dispersing a monomer in a nonvolatile solvent, and on a substrate, the solution or dispersion have found that a polymer brush layer having a low coefficient of dynamic friction can be suitably formed by polymerizing the monomer contained in in a non-volatile solvent, and have completed the present invention.

That is, according to the first aspect of the present invention, there is provided a method for forming a polymer brush layer on a substrate surface, comprising:
A step of forming on the substrate a layer composed of a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent;
forming a polymer brush layer having a thickness of 20 μm or less on at least a part of the substrate surface by polymerizing a monomer contained in the solution or dispersion in a nonvolatile solvent. A method is provided.

According to a second aspect of the present invention, there is provided a method for forming a polymer brush layer on the inner porous surface of a continuous porous body or the inner surface of a tubular body, comprising:
a step of impregnating the interior of the continuous porous body or the interior of the tubular body with a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent;
forming a polymer brush layer on at least a part of the porous inner surface of the continuous porous body or the inner surface of the tubular body by polymerizing the monomer contained in the solution or dispersion liquid in a nonvolatile solvent. A method of forming a polymer brush layer comprising:

According to the first aspect of the present invention, it is possible to provide a method for forming a polymer brush layer that can suitably form a polymer brush layer with a low coefficient of dynamic friction.
Further, according to the second aspect of the present invention, a polymer brush layer can be suitably formed inside the continuous porous body or the tubular body, whereby a desired polymer brush layer can be formed inside the continuous porous body or the tubular body. Functions can be given.

FIG. 1 is a schematic diagram showing a polymer brush layer formed by a method according to a first embodiment of the invention. FIG. 2 is a schematic diagram showing a polymer brush layer formed by a method according to a second embodiment of the invention.

<First embodiment>
A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing a polymer brush layer formed by a method according to a first embodiment of the invention. FIG. 1 shows a state in which a polymer brush layer 20 according to a first embodiment of the present invention is formed on a substrate 10. FIG.

The base material 10 is not particularly limited, and iron and iron alloys such as cast iron, steel, and stainless steel, non-ferrous metals and non-ferrous alloys such as aluminum and copper, and non-metals such as silicon wafers, glass, and quartz are used. In addition, preferably used are cleavable minerals such as exfoliated pieces of mica, planar substrates provided with polymer thin films having reactive substituents such as hydroxyl groups on the surface, and the like.

The polymer brush layer 20 is a layer formed by the forming method according to the first embodiment, and as shown in FIG. It is formed by swelling with

The method of forming the polymer brush layer according to the first embodiment is a method of forming the polymer brush layer 20 on the substrate 10 as shown in FIG. Alternatively, a step of forming a layer made of the dispersion on the substrate 10;
a step of forming a polymer brush layer 20 having a thickness of 20 μm or less on at least part of the surface of the substrate 10 by polymerizing the monomer contained in the solution or dispersion in a non-volatile solvent on the substrate 10; Be prepared.

In the first embodiment, when the polymer brush layer 20 is formed, the monomers for forming the polymer graft chains that constitute the polymer brush layer 20 are mixed or dispersed in a nonvolatile solvent, and the nonvolatile Polymerization is carried out in a solvent, whereby the polymerization of the monomer can be formed more stably, and as a result, the polymer brush length of the polymer graft chain in the polymer brush layer 20 (that is, the polymer graft chain (average absolute molecular weight) can be increased. By increasing the polymer brush length of the polymer graft chain, the dynamic friction coefficient of the polymer brush layer 20 formed of such a polymer graft chain can be made low. In particular, when the polymer brush layer 20 is used as a sliding surface due to the large polymer brush length of the polymer graft chain, the large polymer brush length increases the cushioning effect on the mating material, thereby reducing friction. In addition, high friction durability can be achieved, and such an effect is particularly effective when the surface smoothness of the mating material is low.

Further, according to the first embodiment, since the polymerization of the monomer is performed in a nonvolatile solvent, the ratio of the monomer contained in the solution or dispersion liquid before polymerization to be used, and the amount formed on the substrate 10, The thickness of the polymer brush layer 20 obtained can be controlled by adjusting the thickness of the layer composed of the solution or dispersion liquid before polymerization and the polymerization conditions. In this case, the polymer brush layer 20 can be suitably formed. Specifically, the polymer brush layer 20 can be formed with a thickness of 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 1 μm or less. is usually 10 nm or more.

In particular, when the monomer is polymerized in a volatile solvent rather than a non-volatile solvent, a large amount of solution is used as a solution in which the monomer is dissolved in the volatile solvent. Therefore, it is difficult to control the polymerization reaction by such a method, and it is difficult to control the thickness of the obtained polymer brush layer 20 with high accuracy. Met. In addition, when the monomer is polymerized in a volatile solvent, since the polymerization is carried out in a large amount of solution, convection occurs during the polymerization reaction. When the length (molecular weight) is increased, the polymer brush length distribution between the formed polymer graft chains becomes wide (the molecular weight distribution becomes large), and the desired friction characteristics cannot be obtained. There was also
On the other hand, according to the forming method according to the first embodiment, such problems can be effectively solved, and as a result, polymer graft chains with a narrow molecular weight distribution can be formed while increasing the molecular weight. is. Since polymer graft chains having a high molecular weight and a narrow molecular weight distribution can be formed, the obtained polymer brush layer 20 can have a reduced coefficient of dynamic friction during sliding. In particular, when the molecular weight distribution of the polymer graft chains is narrow, the length of the polymer brushes of the polymer graft chains is almost uniform, so that the effect of reducing the dynamic friction coefficient is enhanced. In addition, when the monomer is polymerized in a volatile solvent, it is difficult to control the thickness of the formed polymer brush layer 20 because the polymerization is carried out in a large amount of solution. 20 can not be suitably formed, but according to the forming method according to the first embodiment, such a problem can be appropriately solved, and the polymer brush can be formed as thin as 20 μm or less. It is possible to form the layer 20 preferably and with high precision.

The number-average molecular weight (Mn) of the polymer graft chains constituting the polymer brush layer 20 is preferably 500 to 10,000,000, more preferably 200,000, because the coefficient of dynamic friction during sliding can be further reduced. ~10,000,000. In addition, the weight average molecular weight (Mw) of the polymer graft chain that constitutes the polymer brush layer 20 is preferably 500 to 10,000,000, more preferably 200, because the coefficient of dynamic friction during sliding can be further reduced. ,000 to 10,000,000. Further, the molecular weight distribution (Mw/Mn) of polymer graft chains constituting the polymer brush layer 20 is preferably close to 1, preferably 1.0, from the point of view of further reducing the coefficient of dynamic friction during sliding. 5 or less, more preferably 1.3 or less, still more preferably 1.2 or less, and particularly preferably 1.01 to 1.15.

The number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the polymer graft chains constituting the polymer brush layer 20 are increased from the substrate 10 by, for example, hydrofluoric acid treatment. A method of cutting out a molecular graft chain, performing measurement by a gel permeation chromatography method using the cut out polymer graft chain, and calculating using a calibration curve in terms of polyethylene oxide may be mentioned. Alternatively, assuming that the free polymer generated during polymerization has the same molecular weight as the polymer graft chain introduced into the substrate 10, the free polymer is measured by gel permeation chromatography, and a calibration curve in terms of polyethylene oxide is obtained. may be used to calculate the number average molecular weight (Mn), the weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn), and use them as they are.

In addition, the occupied area ratio (occupancy ratio per polymer cross-sectional area) with respect to the area of the surface of the base material 10, that is, the graft density of the polymer graft chains is preferably 10% or more, more preferably 15% or more, and further preferably 15% or more. is 20% or more. The graft density can be calculated from the weight average molecular weight (absolute value of Mw, the amount of the grafted polymer, and the surface area of the base material 10) of the graft chain. The cross-sectional area is obtained from the repeating unit length in the extended form and the bulk density of the polymer, and it can be calculated by multiplying the graft density.The occupied area ratio is calculated by dividing the surface of the substrate 10 by the graft point (the first monomer ) occupies (100% in close packing, no more grafting is possible).

〔上記一般式（１）中、ｍは、１以上１０以下の整数を示す。ｎは、１以上５以下の整数を示す。Ｒ^１は、水素原子、または炭素数１～３のアルキル基を示す。Ｒ^２、Ｒ^３、Ｒ^４は、炭素数１～５のアルキル基を示す。Ｒ^２、Ｒ^３、Ｒ^４は、酸素原子、硫黄原子、フッ素原子から選ばれる１種以上のヘテロ原子を含んでいてもよく、Ｒ^２、Ｒ^３、Ｒ^４は、２つ以上が連結して環状構造であってもよい。また、Ｙは一価のアニオンを示す。〕The monomer for forming the polymer graft chain, which constitutes the polymer brush layer 20, is not particularly limited. can suppress the composition fluctuation in the polymer brush layer 20 with a desired design composition. It is preferable to use at least a monomer having By using a monomer having an ionic dissociation group, the polymer graft chain obtained by polymerization can have an ionic dissociation group. As a monomer for forming a polymer graft chain, in addition to a monomer having an ionic dissociation group, a monomer copolymerizable therewith may be used. Monomers having such an ionic dissociative group are not particularly limited, but include, for example, compounds represented by the following general formula (1).

[In the above general formula (1), m represents an integer of 1 or more and 10 or less. n represents an integer of 1 or more and 5 or less. R ¹ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R ² , R ³ and R ⁴ represent alkyl groups having 1 to 5 carbon atoms. R ² , R ³ and R ⁴ may contain one or more heteroatoms selected from an oxygen atom, a sulfur atom and a fluorine atom, and two or more of R ² , R ³ and R ⁴ are linked may have a cyclic structure. Moreover, Y represents a monovalent anion. ]

The monovalent anion Y in the general formula (1) is not particularly limited, and is BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ^{− ,} SbF ₆ − , AlCl ₄ ⁻ , NbF ₆ ⁻ , HSO ₄ ⁻ , ClO ₄ ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , Cl ⁻ , Br ⁻ , I ⁻ and other anions can be used. , considering the degree of dissociation, stability and mobility in the liquid substance when swollen in the liquid substance, especially BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , CF ₃ SO ₃ ⁻ , or CF ₃ CO ₂ ⁻ are preferred.

〔上記一般式（２）～（９）中、ｍ、Ｒ^１、Ｒ^２、Ｙは、上記一般式（１）と同様である。〕Among the compounds represented by the general formula (1), the compounds represented by the following general formulas (2) to (9) are particularly preferable because they have a greater effect of reducing the friction coefficient of the sliding surface. can be used. In addition, these can be used individually by 1 type or in combination of 2 or more types.

[In the general formulas (2) to (9), m, R ¹ , R ² and Y are the same as in the general formula (1). ]

Further, the non-volatile solvent may be a solvent having a vapor pressure of less than 10 Pa at a temperature of 25 ° C., but a solvent having a vapor pressure of less than 1 Pa at a temperature of 25 ° C. is preferable and has excellent non-volatility. In addition, ionic liquids are preferred because they have high solubility in various monomers.

That is, in the first embodiment, it is particularly preferable to use a monomer having an ionic dissociation group as the monomer for forming the polymer brush layer 20 and use an ionic liquid as the nonvolatile solvent (i.e. , a combination of a monomer having an ionic dissociative group and an ionic liquid is particularly preferred). When an ionic liquid is used in the polymerization system, the viscosity of the solution at the initial stage of polymerization may become relatively high during the polymerization, which makes it difficult to form the desired polymer graft chains. By using a combination of a monomer having an ionic dissociative group and an ionic liquid, the high compatibility between them allows the polymerization reaction of the monomer having an ionic dissociative group to proceed well. , a desired polymer graft chain can be formed relatively easily, and as a result, a polymer brush layer having a low coefficient of dynamic friction can be suitably formed with high productivity.

In the first embodiment, the monomers for forming the polymer graft chains are mixed or dispersed in the nonvolatile solvent and polymerized in the nonvolatile solvent. It is preferable to leave the solvent as it is, so that the finally obtained polymer brush layer 20 can have the polymer graft chains swollen with the non-volatile solvent used for the polymerization. In particular, according to such a method, a monomer for forming a polymer graft chain and a substance having a high affinity with the polymer graft chain after polymerization are selected as the nonvolatile solvent. Since it is sufficient to use only the amount necessary for forming the polymer brush layer 20, the process for removing the solvent can be omitted, and as a result, the production efficiency can be improved. . From this point of view, when a monomer having an ionic dissociation group is used as a monomer for forming a polymer graft chain, an ionic liquid is used as a nonvolatile solvent in consideration of mutual affinity. It is preferred to use

〔上記一般式（１０）中、Ｒ^３～Ｒ^６は互いに同一もしくは異種の炭素数１～５のアルキル基、またはＲ’－Ｏ－（ＣＨ_２）_ｎ－で表されるアルコキシアルキル基（Ｒ’はメチル基またはエチル基を示し、ｎは１～４の整数である。）を示し、これらＲ^３、Ｒ^４、Ｒ^５およびＲ^６のいずれか２個の基が環を形成していても構わない。ただし、Ｒ^３～Ｒ^６の内少なくとも１つは上記アルコキシアルキル基である。Ｘは窒素原子またはリン原子を示し、Ｙは一価のアニオンを示す。〕As the ionic liquid, for example, one represented by the following general formula (10) and having a melting point of 50° C. or lower, preferably 25° C. or lower can be used.

[In the above general formula (10), R ³ to R ⁶ are the same or different alkyl groups having 1 to 5 carbon atoms, or alkoxyalkyl groups represented by R′—O—(CH ₂ ) _n — (R ' represents a methyl group or an ethyl group, and n is an integer of 1 to 4.), and any two groups of R ³ , R ⁴ , R ⁵ and R ⁶ form a ring; I don't mind. However, at least one of R ³ to R ⁶ is the above alkoxyalkyl group. X represents a nitrogen atom or a phosphorus atom, and Y represents a monovalent anion. ]

Examples of alkyl groups having 1 to 5 carbon atoms include methyl group, ethyl group, propyl group, 2-propyl group, butyl group and pentyl group. The alkoxyalkyl group represented by R'-O-(CH ₂ ) _n - includes methoxy or ethoxymethyl group, methoxy or ethoxyethyl group, methoxy or ethoxypropyl group, methoxy or ethoxybutyl group and the like.

Further, as compounds in which any two groups of R ³ , R ⁴ , R ⁵ and R ⁶ form a ring, when a nitrogen atom is adopted for X, aziridine ring, azetidine ring, pyrrolidine ring , a quaternary ammonium salt having a piperidine ring, etc. On the other hand, when a phosphorus atom is employed for X, a quaternary phosphonium salt having a pentamethylenephosphine (phosphorinane) ring, etc. can be mentioned.

〔上記一般式（１１）中、Ｒ’はメチル基またはエチル基を示し、Ｘは窒素原子またはリン原子を示し、Ｙは一価のアニオンを示す。また、Ｍｅはメチル基を、Ｅｔはエチル基を意味する。〕In particular, a quaternary ammonium salt having at least one methoxyethyl group in which R' is a methyl group and n is 2 as a substituent is preferable.
A quaternary salt represented by the following general formula (11) having a methyl group, two ethyl groups and an alkoxyethyl group as substituents can also be preferably used.

[In the above general formula (11), R' represents a methyl group or an ethyl group, X represents a nitrogen atom or a phosphorus atom, and Y represents a monovalent anion. Me means a methyl group, and Et means an ethyl group. ]

The monovalent anions Y in the general formulas (10) and (11) are not particularly limited, and are BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , AlCl ₄ ⁻ , NbF ₆ ⁻ , HSO ₄ ⁻ , ClO ₄ ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , Cl ⁻ , Br ⁻ , I ^{− ,} etc. BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , CF ₃ SO ₃ ⁻ in particular, considering the degree of dissociation, stability and mobility in non-aqueous organic solvents. , or CF ₃ CO ₂ ^— .

Among the quaternary salts represented by the general formulas (10) and (11), specific examples of suitably used quaternary ammonium salts and quaternary phosphonium salts include the following compounds (12) to (20). (Me represents a methyl group and Et represents an ethyl group), and in particular, considering obtaining an electricity storage device excellent in low-temperature characteristics and the like, a quaternary ammonium salt represented by the following formula (12) or (17) is used. A quaternary ammonium salt represented by the following formula (17) is particularly preferable because it has a low viscosity and can further reduce the coefficient of dynamic friction during sliding.

〔上記一般式（２１）中、Ｒ^７は炭素数１～４のアルキル基または水素原子であり、特に炭素数１のメチル基が好ましい。また、Ｒ^８は炭素数１０以下のアルキル基（エーテル結合を含んでいてもよい）であり、好ましい例はエチル基である。Ｒ^９、Ｒ^１０、Ｒ^１１は、それぞれ独立で、炭素数が１から２０のアルキル基で酸素原子を含んでもよい。また、Ｒ^９、Ｒ^１０、Ｒ^１１は、水素原子でもよい。〕

In addition, an ionic liquid other than the compound represented by the general formula (10) may be used. For example, such an ionic liquid includes an ionic liquid containing imidazolium ions represented by the following general formula (21), Examples include ionic liquids containing other aromatic cations represented by the following formulas (22) to (27). As the counter anion forming the ionic liquid containing these imidazolium ions and the ionic liquid containing other aromatic cations, monovalent anions similar to the compounds represented by the above general formulas (10) and (11) are used. can be mentioned.

[In the above general formula (21), R ⁷ is an alkyl group having 1 to 4 carbon atoms or a hydrogen atom, preferably a methyl group having 1 carbon atom. Also, R ⁸ is an alkyl group having 10 or less carbon atoms (which may contain an ether bond), and a preferred example is an ethyl group. R ⁹ , R ¹⁰ and R ¹¹ are each independently an alkyl group having 1 to 20 carbon atoms and may contain an oxygen atom. Also, R ⁹ , R ¹⁰ and R ¹¹ may be hydrogen atoms. ]

In the first embodiment, the method of forming a layer composed of a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent on the substrate 10 is not particularly limited, but such a solution or dispersion on the substrate 10 by a doctor blade method or spin coating method, a method of dropping onto the substrate 10, and a solution obtained by mixing or dispersing the substrate 10 with a monomer in a nonvolatile solvent Alternatively, a method of immersing in a dispersion liquid may be used.

Moreover, the method of polymerizing the monomer contained in the solution or dispersion in the non-volatile solvent on the base material 10 is not particularly limited, but a surface-initiated living radical polymerization method and the like can be mentioned.

In the surface-initiated living radical polymerization method, a polymerization initiating group is introduced in advance to the surface of the substrate 10 before forming a layer composed of a solution or dispersion obtained by mixing or dispersing a monomer in a nonvolatile solvent, and the polymerization initiating group is is a method of forming a polymer graft chain by performing living radical polymerization with the starting point. can be done.

Further, when the polymerization is performed by the surface-initiated living radical polymerization method, the method for introducing the polymerization initiation group onto the surface of the base material 10 is not particularly limited, but the polymerization initiator can be dissolved or dispersed in a solvent. A method of preparing a solution and immersing the substrate 10 in the prepared polymerization initiator solution can be used.

The polymerization initiator is not particularly limited, but is preferably a compound having a group capable of bonding to the base material 10 and a radical generating group. , TEMPO-based, ATRP-based, RAFT-based, and RTCP-based polymerization initiators can be used. Among these, TEMPO-based, RAFT-based, and RTCP-based polymerization initiators are more preferable. Among TEMPO-based polymerization initiators, DEPN-based polymerization initiators are particularly preferred. Examples of groups that can be bonded to the substrate 10 include -SiCl ₃ , -Si(CH ₃ )Cl ₂ , -Si(CH ₃ ) ₂ Cl, and -Si(OR) ₃ (in these formulas, R represents methyl, ethyl, propyl or butyl.) and the like.

Then, when the polymerization is performed by the surface-initiated living radical polymerization method, the polymerization initiator is fixed to the surface of the base material 10 using the above-described polymerization initiator, thereby introducing the polymerization initiation group to the surface of the base material 10. Next, on the substrate 10 having the polymerization initiation group introduced therein, a layer made of a solution or a dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent is formed, and in a non-oxidizing gas atmosphere, it is heated or exposed to ultraviolet rays or electrons. A polymer graft chain can be formed on the surface of the base material 10 by irradiating with a ray or a gamma ray to progress the polymerization of the monomer in the non-volatile solvent. , a polymer brush layer 20 made of polymer graft chains swollen by the non-volatile solvent used for polymerization can be formed. The polymerization reaction may be carried out under pressurized conditions (for example, pressurized conditions of 50 to 500 MPa), whereby the molecular weight of the polymer graft chain (that is, polymer brush length) can be further increased. .

The thickness of the polymer brush layer 20 formed according to the first embodiment is usually 20 μm or less, preferably 5 μm or less, more preferably 1 μm or less, and the lower limit is usually 10 nm or more.

The solution obtained by mixing or dispersing the monomers in the non-volatile solvent to be used for the polymerization may contain components necessary for the polymerization reaction, such as various radical initiators.

The polymer brush layer 20 obtained by the forming method according to the first embodiment has a low coefficient of dynamic friction, and is therefore suitable for use as, for example, a sliding member or a sliding mechanism using the polymer brush layer as a sliding surface. can be used.

<Second embodiment>
Next, a second embodiment of the invention will be described.
FIG. 2 is a schematic diagram showing a polymer brush layer formed by a method according to a second embodiment of the invention. FIG. 2 shows a state in which the polymer brush layer 20a according to the second embodiment of the present invention is formed in the gap between the first substrate 10a and the second substrate 10b.

The first base material 10a and the second base material 10b are not particularly limited, and the same material as in the first embodiment can be used.

The polymer brush layer 20a is a layer formed by the forming method according to the second embodiment, and similarly to the polymer brush layer 20 according to the first embodiment, a plurality of polymer brush layers fixed on the first substrate 10a by covalent bonds. polymer graft chains are formed by being swollen with a liquid substance.

In the method of forming the polymer brush layer according to the second embodiment, as shown in FIG. This is a method of forming the brush layer 20a, and according to the second embodiment, the polymer brush layer 20a with a low dynamic friction coefficient can be suitably formed in such a narrow gap.

That is, in the method of forming the polymer brush layer according to the second embodiment, the distance d between the first substrate 10a and the second substrate 10b is 500 μm or less, and the monomer is mixed with the non-volatile solvent. or a step of impregnating with a dispersed solution or dispersion;
A polymer brush layer 20a is formed on at least part of the surfaces of the first substrate 10a and the second substrate 10b forming the gap by polymerizing the monomer contained in the impregnated solution or dispersion in a non-volatile solvent. and a step of performing.

According to the method of forming the polymer brush layer according to the second embodiment, the distance d between the first base material 10a and the second base material 10b is preferably 500 μm or less, more preferably 100 μm or less. Even if there is a gap, the polymer brush layer 20a with a low coefficient of dynamic friction can be preferably formed.

In the second embodiment, when forming the polymer brush layer 20a, a solution or dispersion obtained by mixing or dispersing a monomer for forming a polymer graft chain constituting the polymer brush layer 20a in a non-volatile solvent. The gap between the first base material 10a and the second base material 10b is impregnated with the dispersion liquid, and then the monomer for forming the polymer graft chain is polymerized in the gap in a non-volatile solvent. As a result, the polymer brush layer 20a can be suitably formed even with a minute gap.

In particular, according to the second embodiment, such a narrow gap is impregnated with a solution or dispersion obtained by mixing or dispersing a monomer in a nonvolatile solvent, and polymerization is performed in the narrow gap. Due to the effect of the narrowed reaction space, it is possible to highly suppress the occurrence of convection during the polymerization reaction. As a result, it is possible to effectively suppress the broadening of the polymer brush length distribution (increasing the molecular weight distribution) due to the occurrence of convection, and as a result, the molecular weight can be increased. However, it can form polymer graft chains with a narrow molecular weight distribution. Further, since polymer graft chains having a high molecular weight and a narrow molecular weight distribution can be formed, the obtained polymer brush layer 20a can have a further reduced coefficient of dynamic friction during sliding. In particular, when the molecular weight distribution of the polymer graft chains is narrow, the length of the polymer brushes of the polymer graft chains is almost uniform, so that the effect of reducing the dynamic friction coefficient is enhanced.

The number-average molecular weight (Mn) of the polymer graft chains constituting the polymer brush layer 20a is preferably 500 to 10,000,000, more preferably 200,000, because the coefficient of dynamic friction during sliding can be further reduced. ~10,000,000. In addition, the weight average molecular weight (Mw) of the polymer graft chain that constitutes the polymer brush layer 20 is preferably 500 to 10,000,000, more preferably 200, because the coefficient of dynamic friction during sliding can be further reduced. ,000 to 10,000,000. Further, the molecular weight distribution (Mw/Mn) of polymer graft chains constituting the polymer brush layer 20 is preferably close to 1, preferably 1.0, from the point of view of further reducing the coefficient of dynamic friction during sliding. 5 or less, more preferably 1.3 or less, still more preferably 1.2 or less, and particularly preferably 1.01 to 1.15. Further, the thickness of the polymer brush layer 20a is not particularly limited, and the thickness corresponding to the distance d between the first base material 10a and the second base material 10b, that is, the thickness substantially equal to the distance d. is preferably 500 μm or less, more preferably 100 μm or less.

In addition, in the second embodiment, in the gap between the first base material 10a and the second base material 10b, a monomer for forming a polymer graft chain is mixed or dispersed in a non-volatile solvent. , Polymerization is carried out in a non-volatile solvent, but by leaving the non-volatile solvent used for polymerization as it is, the finally obtained polymer brush layer 20a is formed by the polymer graft chains in the non-volatile solvent used for polymerization. It can be swollen with

In particular, according to the second embodiment, the polymer brush layer 20a is formed in the narrow gap between the first base material 10a and the second base material 10b because the monomer is polymerized in the non-volatile solvent. In this case, as the solution or dispersion before polymerization, it is sufficient to impregnate only the amount necessary for forming the polymer brush layer 20a.In addition, the formed polymer brush layer 20a is also impregnated. correspond to the amount of pre-polymerization solution or dispersion impregnated (i.e., formed at a location corresponding to the impregnated pre-polymerization solution or dispersion with a corresponding formation area); Therefore, the polymer brush layer 20a can be preferably formed in such a narrow gap.

Therefore, according to the second embodiment, when forming the polymer brush layer 20a in the narrow gap formed by the first base material 10a and the second base material 10b, such a first base material The facing structure of 10a and second base material 10b is dismantled once, a polymer brush layer is formed on each surface, and the first base material 10a and second base material 10b on which the polymer brush layer is formed again face each other. This eliminates the need to take the step of setting the number of parts to one another, thereby dramatically improving the production efficiency. In addition, when adopting a method of separately forming polymer brush layers on the surfaces of the first base material 10a and the second base material 10b and making them face each other again in this manner, the polymer brush layers are formed on these. Since the polymer brush layer does not necessarily match the size of the gap between the first base material 10a and the second base material 10b (for example, the size of the gap between the first base material 10a and the second base material 10b On the other hand, the polymer brush layer may be too thick or too thin), and it is assumed that sufficient sliding properties cannot be exhibited. In particular, in the embodiment shown in FIG. 2, an example is shown in which the polymer brush is formed in the gap between the two planes formed by the first base material 10a and the second base material 10b. When forming a layer, when forming a polymer brush layer in a gap formed by a leveling surface, and when forming a polymer brush layer in a gap having a more complicated shape, such a problem becomes more pronounced. become conspicuous.

In contrast, according to the second embodiment, such problems can be effectively resolved.

The monomer for forming the polymer graft chain, which constitutes the polymer brush layer 20, is not particularly limited, and the same monomer as in the above-described first embodiment can be used, but it has an ionic dissociation group. It is preferable to use at least a monomer (in particular, a monomer having an ionic dissociation group and a reactive double bond group), and in addition to the monomer having an ionic dissociation group, a monomer copolymerizable therewith is used. good too. Moreover, as the monomer having an ionic dissociation group, the same monomer as in the above-described first embodiment can be used. In particular, since a monomer having an ionic dissociation group is excellent in penetrating into narrow gaps, it is preferable to use a monomer having an ionic dissociation group from this point of view as well.

In addition, the non-volatile solvent is not particularly limited, and the same one as in the above-described first embodiment can be used, but it is excellent in non-volatility and has high solubility in various monomers. Furthermore, ionic liquids are preferred from the viewpoint of excellent permeability into narrow gaps. Moreover, as the ionic liquid, the same liquid as in the above-described first embodiment can be used.

That is, in the second embodiment, it is particularly preferable to use a monomer having an ionic dissociation group as the monomer for forming the polymer brush layer 20a, and use an ionic liquid as the nonvolatile solvent (i.e. , a combination of a monomer having an ionic dissociative group and an ionic liquid is particularly preferred). When an ionic liquid is used in the polymerization system, the viscosity of the solution at the initial stage of polymerization may become relatively high during the polymerization, which makes it difficult to form the desired polymer graft chains. By using a combination of a monomer having an ionic dissociative group and an ionic liquid, the polymerization reaction of the monomer having an ionic dissociative group can be favorably achieved due to their high compatibility and the polymerization environment of narrow gaps. As a result, a desired polymer graft chain can be formed relatively easily, and as a result, a polymer brush layer having a low coefficient of dynamic friction can be preferably formed with high productivity. .

In the second embodiment, a solution or dispersion obtained by mixing or dispersing a monomer for forming a polymer graft chain constituting the polymer brush layer 20a in a non-volatile solvent is combined with the first base material 10a, The method for impregnating the gap with the second base material 10b is not particularly limited, but examples include a method of dripping such a solution or dispersion near the entrance of the gap and impregnating using capillary action. be done.

In addition, in the second embodiment, the method of polymerizing the monomer contained in the solution or dispersion impregnated into such gaps in a non-volatile solvent is not particularly limited, but is the same as in the above-described first embodiment. , surface-initiated living radical polymerization, and the like.

Specifically, in the second embodiment, the surface of the first base material 10a and the surface of the second base material 10b before being impregnated with a solution or dispersion obtained by mixing or dispersing a monomer in a nonvolatile solvent are preliminarily A polymerization initiating group is introduced, and living radical polymerization is performed using the polymerization initiating group as a starting point, thereby forming a plurality of polymer graft chains fixed by covalent bonds on the first base material 10a and the second base material 10b. Multiple polymer grafts can be formed covalently anchored thereon.

Further, when the polymerization is performed by the surface-initiated living radical polymerization method, the method of introducing the polymerization initiating group to the surface of the first base material 10a and the surface of the second base material 10b is not particularly limited, but the polymerization initiator is dissolved in a solvent. Alternatively, a method of preparing a polymerization initiator solution by dispersing, impregnating the prepared polymerization initiator solution into the gap between the first base material 10a and the second base material 10b, and then removing the solvent. be done.

Although the polymerization initiator is not particularly limited, for example, the same initiator as in the first embodiment can be used.

Then, when the polymerization is performed by the surface-initiated living radical polymerization method, the above-described polymerization initiator is used to introduce the polymerization initiation group to the surface of the first substrate 10a and the surface of the second substrate 10b, and then the first The gap between the base material 10a and the second base material 10b is impregnated with a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent, and heated in a non-oxidizing gas atmosphere or exposed to ultraviolet rays, electron beams, γ Forming a plurality of polymer graft chains on the surface of the first base material 10a and the surface of the second base material 10b, respectively, by irradiating with rays to promote polymerization of monomers in a nonvolatile solvent. A polymer brush layer 20a composed of a plurality of polymer graft chains swollen with the non-volatile solvent used for polymerization is formed in the minute gap between the first base material 10a and the second base material 10b. can be done.

In the polymer brush layer 20a thus formed, a plurality of polymer graft chains covalently fixed on the first base material 10a and a plurality of polymer graft chains covalently fixed on the second base material 10b A plurality of polymer graft chains are swollen with a non-volatile solvent and face each other. Therefore, according to the second embodiment, the polymer brush layer 20a with a low coefficient of dynamic friction can be suitably formed in a minute gap.

The solution obtained by mixing or dispersing the monomers in the non-volatile solvent to be used for the polymerization may contain components necessary for the polymerization reaction, such as various radical initiators.

In addition, in the second embodiment, a mode in which a plurality of polymer graft chains are formed on the surface of the first base material 10a and the surface of the second base material 10b, respectively, is illustrated, but only the surface of the first base material 10a, or , a plurality of polymer graft chains may be formed only on the surface of the second substrate 10b.

The polymer brush layer obtained by the forming method according to the second embodiment has a low coefficient of dynamic friction. It can be suitably used as a sliding member or a sliding mechanism that develops a sliding mechanism by sliding the members 10b and 10b against each other.

<Other embodiments>
In the second embodiment described above, an aspect of forming the polymer brush layer 20a in the gap between the first substrate 10a and the second substrate 10b was illustrated, but the present invention is not particularly limited to such an aspect. The method of forming the polymer brush layer can be applied to various gaps.

For example, in the above-described second embodiment, an embodiment is illustrated in which the polymer brush layer 20a is formed in the biplanar gap formed between the first base material 10a and the second base material 10b as shown in FIG. According to the second embodiment described above, not only gaps formed by flat surfaces, but also gaps with curved surfaces, gaps formed by smoothing surfaces, and gaps with complicated shapes have dynamic friction coefficients. A polymer brush layer 20a having a low .times..times..times..times..times..times.

Moreover, according to the present invention, it is also possible to provide a method for forming a polymer brush layer on the inner porous surface of a continuous porous body.
The interior of the continuous porous body is impregnated with a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent, and then the monomer contained in the solution or dispersion is polymerized in the non-volatile solvent to obtain a continuous porous body. A polymer brush layer can be formed on at least a portion of the porous inner surface of the.

The continuous porous body is not particularly limited, but includes, for example, a porous body having a continuous skeleton of a three-dimensional network structure and voids, that is, a monolithic porous body. According to the method of the present invention, a polymer brush layer can be formed on the inner surface of the pores constituting such a continuous porous body, thereby adjusting the pore diameter in the pores constituting the continuous porous body. (The pore diameter can be adjusted by the thickness of the polymer brush layer to be formed.). Further, by forming a polymer brush layer on the inner surface of the pores constituting the continuous porous body, various functions can be imparted to the inner surface of the pores. By introducing a functional group corresponding to the function, it is possible to impart a desired function to the inner surface of the porous structure, thereby making it possible to apply it to a wide range of applications.

In addition, the present invention can also provide a method for forming a polymer brush layer on the inner surface of a tubular body, such method comprising:
The inside of the tubular body is impregnated with a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent, and then the monomer contained in the solution or dispersion is polymerized in the non-volatile solvent. A polymer brush layer can be formed on at least part of the surface.

The tubular body is not particularly limited, and examples thereof include capillary tubes and microchannels. According to the method of the present invention, a polymer brush layer can be formed on the inner surface of such a tubular body, whereby various functions can be imparted to the inner surface of the tubular body. By introducing a functional group corresponding to a desired function into the monomer for forming the brush layer, it is possible to impart the desired function to the inner surface of the tubular body, thereby making it possible to apply it to a wide range of applications. It becomes possible.

In either of the method of forming the polymer brush layer on the inner porous surface of the continuous porous body and the method of forming the polymer brush layer on the inner surface of the tubular body, The same configuration as in the second embodiment can be used without limitation (for example, the same monomers and non-volatile solvents can be used, and the polymerization method, polymerization conditions, etc. can also be the same).

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

<Example 1>
0.4 g of 3-((3-(triethoxysilyl)propyl)thio)propyl-2-bromo-2-methylpropanoate (BPTPE) as an immobilized initiator and 20 ml of ethanol were mixed and then , 20 ml of ethanol containing 1.8 g of aqueous ammonia was mixed to prepare an immobilized initiator-containing solution. Then, the silicon substrate was immersed in the immobilized initiator-containing solution prepared above for 18 hours to prepare a silicon substrate having a polymerization initiation group introduced on its surface.

In addition to the above, as a monomer having an ionic dissociation group (ionic liquid monomer), N,N-diethyl-N-(2-methacryloylethyl)-N-methylammonium bis(trifluoromethylsulfonyl)imide (DEMM-TFSI) 16 g, ethyl-2-bromo-2-methylpropionate (EBIB) 0.013 g as a radical initiator, 2,2-bipyridyl 0.033 g as a ligand, CuCl as a copper catalyst 0.132 g, 0.0448 g of CuCl ₂ in N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide (DEME -TFSI) to obtain a monomer solution.

Then, the resulting monomer solution was applied to the surface of the silicon substrate having the polymerization initiation group introduced above, and then this was placed in an incubator under an argon atmosphere at 70°C for 32 hours. By heating, atom transfer radical polymerization (ATRP) proceeds to form polymer graft chains on the surface of the silicon substrate, thereby forming a polymer brush layer (poly(DEMM)) having a thickness of 0.5 μm on the surface of the silicon substrate. -TFSI) formed a polymer brush layer) swollen with DEME-TFSI. In addition, when the number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the free polymer jointly obtained in the synthesis system were measured at this time, Mn = 6.68 × 10 ⁵ , Mw=7.93×10 ⁵ , Mw/Mn=1.18. Therefore, it can be said that the polymer graft chains introduced on the surface of the silicon substrate also have the same number average molecular weight and molecular weight distribution.

The number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the free polymer were determined by gel permeation chromatography (GPC). For the measurement, Showa Denko Co., Ltd. "Shodex GPC-101" (columns ("Shodex OHpak SB-806M HQ", Showa Denko Co., Ltd.) are connected in series) as a measuring device. A 1:1 (volume ratio) mixture of 0.2 M sodium nitrate aqueous solution and 0.5 M acetonitrile acetate solution was used as an eluent. Moreover, the measurement was performed at 40° C. and the flow rate was 1.0 ml/min. Then, from the obtained measurement results, the number average molecular weight (Mn) and the molecular weight distribution (Mw/Mn) of the free polymer were determined using a polyethylene oxide-equivalent calibration curve prepared by Shodex480II.

Then, silica thin film-formed silica spheres (untreated silica spheres are coated with an adhesive to form a thick film on the surface of the polymer brush layer-formed silicon substrate obtained above, on which the polymer brush layer is formed). A silicon substrate having a polymer brush layer formed thereon was slid while pressing a silica sphere to which a silica thin film of 3 μm was adhered) with the following load, and the dynamic friction coefficient was measured from the frictional force sensed by the load cell. The measurement conditions were as follows. As a result, the coefficient of dynamic friction in this example was 0.004, and it was confirmed that the coefficient of dynamic friction was reduced.
・ Measuring device: Surface property measuring machine “TRIBOGEAR, TYPE38” (manufactured by Shinto Kagaku Co., Ltd.)
・Load: 500 g (surface pressure: 301 MPa)
・Movement speed: 600mm/min (10mm/sec)
・Test temperature: 24.0°C
・Test humidity: 25%

<Example 2>
Two slide glasses were prepared, and a narrow gap was formed by inserting a silicone rubber spacer having a thickness of 0.1 mm between the two slice glasses. Next, in the same manner as in Example 1, a solution containing an immobilization initiator was prepared, and then, two slices of glass were placed in a state in which a narrow gap was formed, and the immobilization initiator prepared in the same manner as in Example 1 Polymerization initiation groups were introduced onto the surfaces of the two sliced glass sheets by immersing them in the agent-containing solution for 18 hours.

Next, in the same manner as in Example 1, a monomer solution was prepared, and the obtained monomer solution was dropped near the entrance of the gap between the two sliced glasses into which the polymerization initiating group was introduced, Impregnation was carried out in the gap using capillary action. Next, this is heated in an incubator under an argon atmosphere at 70° C. for 32 hours to allow atom transfer radical polymerization (ATRP) to proceed, and polymer By forming graft chains, a polymer brush layer (a polymer brush layer formed by swelling poly(DEMM-TFSI) with DEME-TFSI) was formed in a narrow gap formed by two pieces of sliced glass.

Regarding the polymer brush layer (poly(DEMM-TFSI) obtained above, the number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) were measured in the same manner as in Example 1. The results were almost the same as in Example 1. Further, when the dynamic friction coefficient of the polymer brush layer obtained above was measured, the level was almost the same as in Example 1, and the dynamic friction coefficient was approximately the same as in Example 1. It was confirmed that it was reduced.

<Example 3>
A solution containing an immobilized initiator was prepared in the same manner as in Example 1, and then a silica monolith (having a pore diameter of about 2 μm) as a porous substrate was immersed in the prepared solution containing an immobilized initiator. introduced polymerization initiation groups to the inner surface of the pores of the silica monolith.

Next, in the same manner as in Example 1, a monomer solution was prepared, the silica monolith into which the polymerization initiation group obtained above had been introduced was immersed in the monomer solution, and the silica monolith was recovered from the monomer solution. was impregnated with the monomer solution. Next, this is heated in an incubator under an argon atmosphere at 70° C. for 32 hours to allow atom transfer radical polymerization (ATRP) to proceed, and polymer graft chains are formed on the inner surface of the pores of the silica monolith. A polymer brush layer (poly(DEMM-TFSI) swollen with DEME-TFSI) was formed in the pores of the silica monolith.

Regarding the polymer brush layer (poly(DEMM-TFSI) obtained above, the number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) were measured in the same manner as in Example 1. By the way, the results were almost the same as in Example 1.

<Example 4>
A monomer solution was prepared in the same manner as in Example 1, and the obtained monomer solution was applied to the surface of a silicon substrate having a polymerization initiating group introduced in the same manner as in Example 1. , Sealed in a Teflon (registered trademark) container under an argon atmosphere, and heated at 70 ° C. for 5 hours in a medium pressure polymerization container of 100 MPa (medium pressure polymerization conditions) to perform atom transfer radical polymerization. (ATRP) to form a polymer graft chain on the surface of the silicon substrate, a 0.2 μm thick polymer brush layer (poly (DEMM-TFSI) formed a polymer brush layer) swollen with DEME-TFSI. In addition, when the number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the free polymer jointly obtained in the synthesis system were measured at this time, it was found that under medium pressure polymerization conditions, had a degree of polymerization of 2215, Mn=3.01×10 ⁵ , Mw=3.88×10 ⁵ and Mw/Mn=1.29. On the other hand, when carried out in a normal pressure incubator under the same conditions, the degree of polymerization was 805, Mn = 9.65 × 10 ⁴ , Mw = 1.12 × 10 ⁵ , Mw/Mn = 1.16. A degree of polymerization about 2.8 times higher than that obtained under pressure was obtained by combining medium pressure polymerization.

When the dynamic friction coefficient of the polymer brush layer (poly (DEMM-TFSI) obtained above was measured, the level was almost the same as in Example 1, confirming that the dynamic friction coefficient was reduced. did it.

Claims (8)

A method for forming a polymer brush layer on a substrate surface, comprising:
A step of forming on the substrate a layer composed of a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent;
forming a polymer brush layer having a thickness of 20 μm or less on at least a part of the substrate surface by polymerizing the monomer contained in the solution or dispersion in a nonvolatile solvent;
A method for forming a polymer brush layer, wherein the non-volatile solvent is an ionic liquid. a step of impregnating a gap formed by the first substrate and the second substrate facing each other at a distance of 500 μm or less with a solution or dispersion obtained by mixing or dispersing a monomer in a nonvolatile solvent; ,
By polymerizing the monomer contained in the impregnated solution or dispersion in a non-volatile solvent, at least part of the substrate surface of at least one of the first substrate and the second substrate forming the gap is polymerized. a step of forming a brush layer;
A method for forming a polymer brush layer , wherein the non-volatile solvent is an ionic liquid . A method for forming a polymer brush layer on the inner porous surface of a continuous porous body or the inner surface of a tubular body, comprising:
a step of impregnating the interior of the continuous porous body or the interior of the tubular body with a solution or dispersion obtained by mixing or dispersing a monomer in a non-volatile solvent;
forming a polymer brush layer on at least a part of the porous inner surface of the continuous porous body or the inner surface of the tubular body by polymerizing the monomer contained in the solution or dispersion liquid in a nonvolatile solvent. prepared ,
A method for forming a polymer brush layer , wherein the non-volatile solvent is an ionic liquid . The method for forming a polymer brush layer according to any one of claims 1 to 3, wherein the non-volatile solvent has a vapor pressure of less than 10 Pa at a temperature of 25°C. The method for forming a polymer brush layer according to any one of claims 1 to 4, wherein the polymerization of the monomer is carried out by a surface-initiated living radical polymerization method on the surface of the substrate. As polymerization initiators, as groups capable of bonding to the substrate surface, —SiCl ₃ , —Si(CH ₃ )Cl ₂ , —Si(CH ₃ ) ₂ Cl, and —Si(OR) ₃ (wherein R represents methyl, ethyl, propyl or butyl.) and a compound having a radical generating group. 7. The method for forming a polymer brush layer according to claim 5, wherein the surface-initiated living radical polymerization is performed under a pressure condition of 50 to 500 MPa. 8. The method of forming a polymer brush layer according to claim 1, wherein the monomer contains at least a compound having an ionic dissociation group.

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