JP2014105130A - Silica structure and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powdery silica structure having a three-dimensional regular structure and a method for manufacturing the same.SOLUTION: The provided method for manufacturing a silica structure comprises: a step of forming, by mixing, within an organic solvent, a hydrolyzate of a hydrolyzable silane with a diblock copolymer possessing a polar block (B) having a solubility parameter (SP value) of 22-25 (MPa) and a low-polarity block (A) incompatible with the polar block (B), a composite wherein the hydrolyzate is adsorbed on the polar block (B); a step of obtaining, by inducing a self-organization of the composite and a polycondensing reaction of the hydrolyzate within an organic solvent, a phase-separated composite of the diblock copolymer and silica; and a step of removing the diblock copolymer. A powdery silica structure having a three-dimensional regular structure and manufactured by this method for manufacturing a silica structure is also provided.

Description

  The present invention relates to a silica structure and a method for producing the same, and in particular, a method for producing a silica structure using a composite of a diblock copolymer and a hydrolyzate of hydrolyzable silane, and silica obtained by the production method. Concerning the structure.

In the development of inorganic materials, structural control is one of the most important issues. On the other hand, regarding organic materials, it is considered that materials having relatively various structures can be obtained from the diversity of primary structures such as molecular chains and functional groups.
As a method for controlling the structure of an inorganic material, a method of adding an organic material has been studied. A typical example is a method of synthesizing a mesoporous material that is an inorganic porous body using a micelle structure of an organic material. This method is generally a composite of a surfactant having a micelle structure and an inorganic material precursor, which is self-assembled by adding an amphiphilic surfactant to an aqueous solution in which the precursor of the inorganic material is dissolved. Then, the composite is heated at a high temperature to sinter the inorganic material and thermally decompose the surfactant. Thus, the part where the surfactant is decomposed has a regular pore structure. Thus, in this method, since the inorganic precursor surrounds the micelle of the surfactant in the aqueous solution, the inorganic material finally obtained always has a porous structure. That is, the inorganic material surrounds the space that is the pore.
As a surfactant used in this method, a block copolymer containing at least a polyalkylene oxide block such as a tetraalkylammonium surfactant (see Patent Document 1 and Non-patent Document 1), a polyethylene oxide block, a polypropylene oxide block, and the like. A combination (see Patent Documents 2 to 5, Non-Patent Document 2, etc.) is frequently used. A number of methods using block copolymers as surfactants have been reported, but the regularity of the pore structure is limited to a few types, and various structures can be used to further expand the application range of inorganic materials. Synthetic methods that can be produced are desired.

In addition, a method for producing an inorganic material using a variety of self-organized structures by microphase separation of a block copolymer as a template can be mentioned. Here, “microphase separation” means that a block copolymer in which one ends of incompatible polymer chains (blocks) having different properties are connected to each other, the blocks do not cross each other because of the size of the molecular chain. The phenomenon of phase separation. In the microphase separation of block copolymers, various structures have been studied theoretically and experimentally by self-organization. Thus, “microphase separation” is a phenomenon in which incompatible polymer chains are phase-separated, and is different from the micelle structure of the surfactant used in the production of the mesoporous material.
Examples include a method of producing an inorganic material using such a self-organized block copolymer by microphase separation as a template (Patent Documents 6 and 7, etc.). The methods described in Patent Documents 6 and 7 are methods using microphase separation of a block copolymer applied to a substrate, and one block of the block copolymer subjected to microphase separation is irradiated with ultraviolet rays, ozonolysis, etc. In this method, the inorganic material is filled in the space removed in step (b). That is, these methods are methods for forming an organic-inorganic composite of a block copolymer and an inorganic material by a microphase separation and removal step of the block copolymer and a filling step of the inorganic material.

  By the way, in recent years, there has been reported a method for producing an inorganic material having a regular structure at once through a hybrid material of a block copolymer and an inorganic raw material by utilizing microphase separation of the block copolymer ( Patent Document 8 and Non-Patent Documents 3 and 4). In any of these methods, a mixed solution of a block copolymer and an inorganic raw material is applied to a base material, etc. to form a thin film hybrid material, and then the block copolymer is removed to form a thin film with a regular structure. This is a method for obtaining an inorganic material. The inorganic material manufactured by such a method is an extremely thin thin film having a thickness of 100 nm or less, and it is difficult to obtain only the inorganic material by removing the base material, which may limit the use and the like. Therefore, there has been a demand for a method for producing a powdery silica structure that is not limited in its application.

JP 2002-241124 A Special table 2004-536043 gazette JP 2006-70139 A Japanese Patent Application Laid-Open No. 2000-233995 JP 2006-327854 A JP 2010-142881 A JP 2012-1787 A JP 2011-195394 A

Alan Sellinger, Pillar M. Weiss, Anh Nguyen, Yunfeng Lu, Roger A. et al. Assink, Weilong Gong, C.I. Jeffrey Brinker, “Continuous self-assembly of organic-inorganic nanocomposite coatings that mimic nanore”, Nature, 1998, Vol 394, p. 256-260 Dongyuan Zhao, Qisheng Huo, Jianglin Feng, Bradley F. Chmelka, Galen D.C. Stucky, "Nonionic Triblock and Star Diblock Copolymer and Oligomeric Surfactant Syntheses of Highly Ordered, Hydrothermally Stable, Mesoporous Silica Structures", Journal of the American Chemical Society, 1998, Vol 120, p. 6024-6036 Chengdu Liang, Kunlun Hong, Georges A .; Guiochon, Jimmy W. Mays, Sheng Dai, “Synthesis of a Large-Scale Highly Ordered Porous Carbon Film by Self-Assembly of Block Copolymers, A200. 5785-5789. Lixin Song, Yeng Ming Lam, Chris Boothrod, Put Wen Teo, “One-step synthesis of titania nanopol pol PS-P4VP diblock. 135605

  An object of this invention is to provide the powdery silica structure which has a three-dimensional regular structure, and its manufacturing method.

  The inventors of the present invention have carried out the phase separation composite of the diblock copolymer and silica by performing the self-assembly of the diblock copolymer and the condensation polymerization reaction of the hydrolyzable silane hydrolyzate in an organic solvent. It has been found that the body can be obtained in powder form. In addition, silica can be made into a continuous phase or a dispersed phase by selectively using an organic solvent that is compatible with either block of the diblock copolymer as an organic solvent that performs self-assembly and polycondensation reaction. I found. Based on these findings, the inventors have further studied and have come to make the present invention.

That is, the object of the present invention has been achieved by the following technical means.
(1) In an organic solvent, a hydrolyzate of hydrolyzable silane, a polar block (B) having a solubility parameter (SP value) of 22 to 25 (MPa ^1/2 ), and the non-polar block (B) A step of mixing a diblock copolymer having a compatible low polarity block (A) to form a complex in which the hydrolyzate is adsorbed on the polar block (B); Performing a self-assembly of the complex and a condensation polymerization reaction of the hydrolyzate to obtain a phase-separated complex of the diblock copolymer and silica; and the diblock from the obtained phase-separated complex A method for producing a silica structure, comprising a step of removing the copolymer.
(2) The step of forming a complex includes a step of mixing a copolymer organic solution containing the block copolymer and an organic solvent and a hydrolyzate obtained by hydrolyzing the hydrolyzable silane. The manufacturing method of the silica structure as described in (1) which has.
(3) In the step of obtaining the phase separation complex, the organic solvent containing the hydrolyzate and the diblock copolymer is allowed to stand or stir to perform the self-organization and the condensation polymerization reaction. A method for producing a silica structure according to (1) or (2).
(4) The method for producing a silica structure according to any one of (1) to (3), wherein the step of forming the complex and the step of obtaining the phase-separated complex are continuously performed. .
(5) The method for producing a silica structure according to any one of (1) to (4), wherein the polar block has a polyvinylpyridine block.
(6) The method for producing a silica structure according to any one of (1) to (5), wherein the polar block does not contain a polyalkylene oxide block.
(7) The method for producing a silica structure according to any one of (1) to (6), wherein the low polarity block is a polystyrene block.
(8) Powdered silica produced by the method for producing a silica structure according to any one of (1) to (7) and having a three-dimensional ordered structure based on a microphase separation structure of the diblock copolymer Structure.
(9) The silica structure according to (8), wherein the microphase separation structure is a co-continuous structure, a lamellar structure, a cylinder structure, or a sphere structure.

According to the present invention, a powdery silica structure having a three-dimensional ordered structure is obtained by performing microphase separation of a diblock copolymer and polycondensation reaction of a hydrolyzate of hydrolyzable silane in an organic solvent. The body can be manufactured.
Such a silica structure having a regular fine structure of silica becomes various material elements. In particular, the powdered silica structure is not limited in its application, for example, as a material element having functionality in a wide range of fields such as an adsorbent, a catalyst carrier, a sensor, an optical material, a lithium ion battery, and a separation membrane. It can be suitably used.

FIG. 1 is an explanatory diagram for explaining how to make a silica structure by selecting an organic solvent. FIG. 2 is an explanatory diagram for explaining how to make a silica structure when a polar organic solvent is used. FIG. 3 is an explanatory view for explaining how to make a silica structure when a nonpolar organic solvent is used. FIG. 4 is an IR spectrum chart of a diblock copolymer and a complex of a hydrolyzate and a diblock copolymer. FIG. 5 is a scanning electron micrograph of the silica structure produced in Example 1. 6 is a scanning electron micrograph of the silica structure produced in Example 2. FIG. FIG. 7 is a scanning electron micrograph of the silica structure produced in Example 3. FIG. 8 is a scanning electron micrograph of the silica structure produced in Example 4. FIG. 9 is a scanning electron micrograph of the silica structure produced in Example 5. FIG. 10 is a scanning electron micrograph of the silica structure produced in Example 6.

The silica structure of the present invention is a powdery silica structure having a three-dimensional regular structure. This silica structure has a structure in which silica is arranged in a structure corresponding to a microphase separation structure of a diblock copolymer described later. Specifically, the silica structure corresponds to a microphase separation structure, such as a sphere structure (also referred to as a fine particle aggregate) such as a body-centered cubic structure, a lamellar structure (including a spherulite lamellar structure), a co-continuous structure ( (Also called a gyroidal structure) and a cylinder structure.
Here, the sphere structure is a structure in which spherical particles or pores are continuously connected, the co-continuous structure is a structure in which both a silica phase and a void phase are continuous, and the cylinder structure is linear. It has a structure with channel-like pores. The lamellar structure is a structure in which a flat silica phase is laminated through an air phase, and the spherulite lamellar structure is a spherical structure in which silica of a lamellar structure spreads radially.
The particle size in the sphere structure, the thickness of each layer in the lamella structure, the particle size in the spherulite lamella structure, the inner diameter and the interval of the holes in the cylinder structure, etc. are the molecular weight of the diblock copolymer used, the repeating unit constituting each block, For example, it can be appropriately controlled depending on the type, size, and the like.
As will be described later, the silica structure is selected from an organic solvent compatible with one block of the diblock copolymer, the amount of hydrolyzate added to the diblock copolymer, the hydrolysis time of the hydrolyzable silane, or Depending on the pH of the acid or the amount of acid used during hydrolysis relative to the hydrolyzable silane, it is produced in any of the structures described above.

The method for producing a silica structure of the present invention includes a hydrolyzate of hydrolyzable silane, a polar block (B) having a solubility parameter (SP value) of 22 to 25 (MPa ^1/2 ), and an organic solvent. A step of mixing a diblock copolymer having a low polarity block (A) to form a complex in which a hydrolyzate is adsorbed on the polar block (B), and self-assembly of the complex in an organic solvent And a step of performing a condensation polymerization reaction of the hydrolyzate to obtain a phase separation complex of the diblock copolymer and silica, and a step of removing the diblock copolymer from the obtained phase separation complex.
That is, the method for producing a silica structure of the present invention includes a silica structure implemented in an organic solvent utilizing microphase separation of a complex of a diblock copolymer and a hydrolyzate and a condensation polymerization reaction of the hydrolyzate. It is a manufacturing method of a body. The complex in which the hydrolyzate was adsorbed on the polar block (B) of the diblock copolymer adsorbed the hydrolyzate by self-assembly similar to the self-assembly by microphase separation of the single block copolymer. Microphase separation in the state. In the method for producing a silica structure of the present invention, self-organization by microphase separation of a complex on which a hydrolyzate is adsorbed is used, and the hydrolyzate is subjected to a polycondensation reaction in the process of self-assembly, thereby self-organization. Silica is arranged in a structure corresponding to the microphase structure by chemical conversion. Here, as will be described later, the hydrolyzate includes a condensation polymerized hydrolyzate. Thereafter, the diblock copolymer is removed to produce a powdery silica structure.

As described above, the method for producing a silica structure of the present invention is different from the method for producing a mesoporous material using a micelle structure of a surfactant as in Patent Documents 1 to 5, and the like. It is a manufacturing method used. Therefore, the silica structure produced by the method for producing a silica structure of the invention has various unique structures by microphase separation, for example, any of a sphere structure, a lamellar structure, a bicontinuous structure, and a cylinder structure. doing.
Further, the method for producing a silica structure of the present invention has a silica structure having a specific structure without filling a space from which one block of the block copolymer is removed, as in the methods described in Patent Documents 6 and 7. The body can be manufactured all at once.
Furthermore, the method for producing a silica structure of the present invention is a method for forming a complex and a phase-separated complex in an organic solvent without using a substrate or the like as in the method described in Patent Document 8. Therefore, the silica structure produced by the method for producing a silica structure of the present invention has forms such as powder, powder, and granule.

  Thus, according to the method for producing a silica structure of the present invention, a powdery silica structure having various structures and shapes controlled can be obtained.

<Diblock copolymer>
The diblock copolymer used in the method for producing a silica structure of the present invention is a diblock copolymer having two types of blocks, a polar block (B) and a polar block (B) and an incompatible low polarity block (A). It is a block copolymer. The bonding mode of these two types of blocks (A) and (B) is not particularly limited.

The polar block (B) in the diblock copolymer has a solubility parameter (SP value) of 22 to 25 (MPa ^1/2 ). When the polar block (B) has a solubility parameter (SP value) in this range, hydrolysis of siloxane or the like having a solubility parameter (SP value) of 22 to 30 (MPa ^1/2 ) in an organic solvent. The product is adsorbed to form a complex of the diblock copolymer and the hydrolyzate. As such polar block (B), poly (4-vinylpyridine) block (P4VP, solubility parameter (SP value): 24), poly (2-vinylpyridine) block (P2VP, solubility parameter (SP value): 22), polyvinyl alcohol block (solubility parameter (SP value): 25) and the like. Among these, the polar block (B) is preferably a poly (4-vinylpyridine) block or a poly (2-vinylpyridine) block. Although the polar block (B) should just have the solubility parameter (SP value) of 22-25 (MPa < ^1/2 >), it does not need to contain a polyalkylene oxide block especially.

The low polarity block (A) may be a block that is incompatible with the polar block (B). Here, “incompatible with the polar block (B)” means that the block copolymer is incompatible with the polar block (B) to such an extent that microphase separation occurs. The low polarity block (A) incompatible with the polar block (B) having a solubility parameter (SP value) of 22 to 25 (MPa ^1/2 ) is, for example, a solubility of 20 (MPa ^1/2 ) or less. It preferably has a parameter (SP value). When the low polarity block (A) has a solubility parameter (SP value) of 20 (MPa ^1/2 ) or less, the complex of the diblock copolymer and the hydrolyzate undergoes microphase separation. The solubility parameter (SP value) of the low polarity block (A) is preferably substantially 15 (MPa ^1/2 ) or more from the viewpoint of solubility. As such a low polarity block (A), polystyrene block (PS, solubility parameter (SP value): about 18), polyisoprene block (solubility parameter (SP value): 17), polyisobutylene block (solubility parameter (SP) Value): 16), polypropylene block (solubility parameter (SP value): 17), polyethylene block (solubility parameter (SP value): 16), and the like. Among these, the low polarity block (A) is preferably a polystyrene block.

  In the present invention, a solubility parameter (SP value) is used as an index representing the characteristics of each block of the block copolymer and the solvent to be used. The SP value indicates the Hildebrand SP value, the literature value and Fedors's value. The value by the estimation method is adopted.

  A diblock copolymer having such a polar block (B) and a low polarity block (A) is a poly (4-vinylpyridine) block or a diblock copolymer having a poly (2-vinylpyridine) block and a polystyrene block. Particularly preferred is a polymer.

The ratio of the low polar block (A) and the polar block (B) in the diblock copolymer is not particularly limited as long as the diblock copolymer is microphase-separated. For example, the ratio of the number average molecular weight (low The polar block (A): polar block (B)) is preferably 1: 0.2 to 1: 5, more preferably 1: 0.5 to 1: 3, and 1: 0.7 to It is more preferably 1: 2, and particularly preferably 1: 1.
The number average molecular weights of the diblock copolymer and the polar block (B) and the low polarity block (A) are not particularly limited, respectively. For example, in the silica structure, the above-described particle size, thickness, It is appropriately selected according to the inner diameter and interval of the holes. The molecular weight distribution of the diblock copolymer is not particularly limited, but is preferably narrow in that a regular structure can be made uniform in the silica structure.

<Hydrolyzable silane hydrolyzate>
The hydrolyzate used in the method for producing a silica structure of the present invention is a hydrolyzate obtained by hydrolyzing all or part of the hydrolyzable silane. The hydrolyzable silane to be hydrolyzed may be a silane having a hydrolyzable group, and examples thereof include a silane compound having a hydrolyzable group such as a halogen atom or an alkoxy group. The hydrolyzable silane is preferably one having four hydrolyzable groups in terms of high hydrolyzability, and particularly preferably an alkoxysilane having four alkoxy groups. Examples of the alkoxysilane having four alkoxy groups include tetramethoxysilane, tetraethoxysilane (also referred to as TEOS), tetra (n-propoxy) silane, tetra (i-propoxy) silane, and tetra (n-butoxy) silane. And tetra (t-butoxy) silane. Among them, tetraethoxysilane is preferable.

Hydrolysis of the hydrolyzable silane is carried out in a known manner, for example, in a solvent such as alcohol or DMF, in the presence of an inorganic acid such as hydrochloric acid or an organic acid such as acetic acid, and water, at room temperature or under heating. Therefore, the hydrolyzate of hydrolyzable silane may contain a solvent, an acid, water, and a substance derived therefrom, in addition to the hydrolyzate of hydrolyzable silane. The hydrolyzable silane is hydrolyzed, partially adsorbed with a block copolymer after being partially polymerized, so that the target silica structure can be easily formed. For example, it is preferably hydrolyzed at 30 to 60 ° C.
In this invention, the hydrolyzate of the hydrolyzable silane may not be completely hydrolyzed, and a part of the hydrolyzable group or a part of the hydrolyzable silane remains. It may be. In the hydrolysis step of the hydrolyzable silane, in addition to the hydrolysis of the hydrolyzable silane, the condensation polymerization reaction of the hydrolyzed hydrolyzate partially proceeds. Therefore, this hydrolyzate has a hydrolyzate having a molecular chain to some extent. Here, the degree to which the polycondensation reaction proceeds can be controlled by the decomposition temperature, decomposition time, amount of inorganic acid or organic acid used, and / or solvent, for example, the target silica structure as described later. It is set appropriately according to.

<Organic solvent>
The organic solvent used in the method for producing a silica structure of the present invention dissolves a diblock copolymer, but does not dissolve a complex, particularly a phase-separated complex. It is used for separation and condensation polymerization of the hydrolyzate to obtain a phase separation complex. As described above, as the organic solvent, a polar organic solvent or a nonpolar organic solvent is selected according to the target silica structure. In the present invention, the polar organic solvent is an organic solvent having a solubility parameter (SP value) of 22 to 25 (MPa ^1/2 ), and the nonpolar organic solvent is a solubility parameter (SP value) of 19 (MPa ^1/2 ) or less. ).

When the polar organic solvent has a solubility parameter (SP value) of 22 to 25 (MPa ^1/2 ), it is well compatible with the polar block (B) that has adsorbed the hydrolyzate. Therefore, in the polar organic solvent, the complex in which the hydrolyzate is adsorbed on the polar block (B) is microphase-separated so that the polar block (B) on which the hydrolyzate is adsorbed surrounds the low polarity block (A). A hydrolyzate, that is, a silica structure in which silica becomes a continuous phase is obtained.
On the other hand, when the nonpolar organic solvent has a solubility parameter (SP value) of 19 (MPa ^1/2 ) or less, it is well compatible with the low polarity block (A) of the diblock copolymer. Therefore, in the nonpolar organic solvent, the complex in which the hydrolyzate is adsorbed on the polar block (B) is microphase-separated so that the polar block (B) is surrounded by the polar block (B) on which the hydrolyzate is adsorbed. Thus, a hydrolyzate, that is, a silica structure in which silica becomes a dispersed phase is obtained. The solubility parameter (SP value) of the nonpolar organic solvent is preferably substantially 15 (MPa ^1/2 ) or more from the viewpoint of the solubility of the diblock body.
Thus, the polar block (B) and the low polarity block (in the microphase separation of the diblock copolymer) are selected by selecting the organic solvent that is the field for the self-assembly of the composite and the condensation polymerization reaction of the hydrolyzate. The phase of A) is reversed, and the continuous phase and dispersed phase of the silica structure can be controlled. Moreover, the shape of a silica structure can be changed by this.

Examples of the polar organic solvent include N, N-dimethylformamide (DMF, solubility parameter (theoretical SP value): 24.5 MPa ^1/2 ), isopropanol (SP value: 23.5 MPa ^1/2 ), 1-butanol ( Solubility parameter (SP value): 23.1 MPa ^1/2 ) and the like. The polar organic solvent is particularly preferably DMF, isopropanol, 1-butanol or the like from the viewpoint of the solubility of the diblock body. These polar organic solvents may be used alone or in combination of two or more.
Examples of the nonpolar organic solvent include benzene (solubility parameter (SP value): 18.8 MPa ^1/2 ), toluene (solubility parameter (SP value): 18.2 MPa ^1/2 ), xylene (solubility parameter (SP value) ): 18.0 MPa ^1/2 ), tetrahydrofuran (solubility parameter (SP value): 18.6 MPa ^1/2 ), chloroform (solubility parameter (SP value): 19.0) and the like. The nonpolar organic solvent preferably has a solubility parameter (SP value) of 15 to 19 MPa ^1/2 from the viewpoint of the solubility of the diblock body, and examples thereof include benzene, toluene, xylene, and tetrahydrofuran. It is done. These nonpolar organic solvents may be used alone or in combination of two or more.

  The amount of the organic solvent used is not particularly limited.

  Next, the method for producing the silica structure of the present invention will be specifically described. In the method for producing a silica structure of the present invention, a hydrolyzable silane hydrolyzate and a diblock copolymer are mixed in an organic solvent, and the hydrolyzate is adsorbed on the polar block (B). A step of obtaining a phase-separated complex of a diblock copolymer and silica by performing self-assembly of the complex and condensation polymerization of the hydrolyzate in an organic solvent, and a phase obtained Removing the diblock copolymer from the separation complex.

In the step of forming the composite, the hydrolyzable silane hydrolyzate and the diblock copolymer are mixed in an organic solvent. If it does so, a hydrolyzate will adsorb | suck to the polar block (B) of a diblock copolymer, and a composite_body | complex will be formed. Here, “the hydrolyzate is adsorbed to the polar block (B)” means, for example, a state in which the hydrolyzate exists in or near the polar block (B) due to electrostatic attraction, It includes a state in which the decomposition product is surrounded, and in some cases, a state in which the polar block (B) and the hydrolysis product are chemically bonded. The mixing conditions at this time are not particularly limited, and examples include conditions where the hydrolyzate is added to the diblock copolymer under normal temperature or heating, and then stirred or allowed to stand. Stirring or standing can be performed, for example, for 0.5 hour to 7 days.
This step has a step of mixing a copolymer organic solution containing a block copolymer and an organic solvent and a hydrolyzate obtained by hydrolyzing the hydrolyzable silane. It is preferable at the point which can use a product with the solution obtained at the hydrolysis process. This solution contains an aqueous acid solution as a hydrolysis catalyst for hydrolyzable silane, but the shape of the composite may change depending on the amount and strength of the aqueous acid solution added. Specifically, the polarity of the whole solvent changes due to the addition amount and strength of the acid aqueous solution, and the polar block (B) is partially protonated, thereby causing electrostatic action with the hydrolyzate. The structure of the composite may change from the above two points.
Hydrolysis of the hydrolyzable silane is as described above, and a hydrolyzate is obtained as a solution. In this hydrolysis process, the hydrolyzed hydrolyzable silane partially undergoes condensation polymerization, and the hydrolyzed product coexists with the condensation product. In the hydrolysis step of the hydrolyzable silane, if the hydrolyzed hydrolyzable silane is subjected to condensation polymerization, the condensation polymerization of the hydrolyzate can proceed rapidly in the step of forming a composite, The shape of the structure can be controlled. However, if the degree of polycondensation of hydrolyzable silane is excessive in the hydrolysis process of hydrolyzable silane, it is difficult to control the shape of the silica structure because the complex is rapidly formed in the process of forming the complex. It may become.
If the hydrolyzate can be dissolved and dispersed uniformly, the hydrolyzable silane can be hydrolyzed using an organic solvent other than alcohol or DMF, for example, the same organic solvent as the organic solvent of the copolymer solution. Can do.

In the step of forming the complex, the concentration of the diblock copolymer in the organic solvent is 3 to 200 mg / mL before adding the hydrolyzate in terms of solubility and yield of the complex. Preferably, it is 5-100 mg / mL. The concentration of the diblock copolymer is more preferably 10 to 100 mg / mL in a polar organic solvent, particularly preferably 50 mg / mL, and 5 to 100 mg / mL in a nonpolar organic solvent. More preferably, it is more preferably 10 mg / mL.
The amount of the hydrolyzate used is 30 to 600 masses per 100 parts by mass of the polar block (B) of the diblock copolymer because the hydrolyzate is adsorbed to the polar block (B) at a certain ratio. It is preferable that the amount of hydrolyzate in parts is a supply amount, and more preferably 50 to 300 parts by mass. Here, the usage-amount of a hydrolyzate means the usage-amount of the silica component (Si conversion) in a hydrolyzate, when an acid, a solvent, etc. contain in a hydrolyzate. In addition, when water and an acid are contained in this hydrolyzate, the content of water is 5 to 30% by mass in terms of the mixing uniformity of the solvent with respect to the total mass of the hydrolyzate. The acid content (strength) is preferably such that the pH in the acid aqueous solution to be added is -0.3 to 4, and -0.3 is preferred. More preferably, it is ~ 3. Further, when the hydrolyzate contains a solvent, the content of the solvent is preferably 60 to 90% by mass with respect to the total mass of the hydrolyzate in terms of mixing uniformity, and is preferably 70 to 90%. More preferably, it is 80 mass%.

As described above, a polar organic solvent or a nonpolar organic solvent is used as the organic solvent depending on the target silica structure.
Specifically, as shown in FIG. 1, microphase separation is caused by the incompatibility between the low polarity block (A) of the diblock copolymer and the polar block (B ′) on which the hydrolyzate is adsorbed. Thus, the structure of the silica structure is determined. At this time, when a nonpolar organic solvent is used as the organic solvent, the low polarity block (A) surrounds the polar block (B ′) in the organic solvent, and the low polarity block (A) becomes a continuous phase, thereby hydrolyzing. The polar block (B ′) on which the substance is adsorbed becomes the dispersed phase. On the other hand, when a polar organic solvent is used as the organic solvent, the low polarity block (A) and the polar block (B ′) to which the hydrolyzate has been adsorbed are reversed, and the low polarity block (A) becomes a dispersed phase. The polar block (B ′) on which the decomposition product is adsorbed becomes a continuous phase. Thus, by selecting an organic solvent, the structure of the silica structure can be made differently.

The silica structure produced when a polar organic solvent is used as the organic solvent will be described in detail.
When a polar organic solvent is used as the organic solvent, any solvent can be used for hydrolysis of the hydrolyzable silane as long as the water contained in the hydrolyzate and the polar organic solvent can be mixed uniformly. Alternatively, the same solvent as the polar organic solvent in the step of forming the complex may be used. When a hydrolyzate is added to an organic copolymer solution obtained by dissolving a block copolymer in a polar organic solvent, a composite is obtained. At this time, as shown in FIG. 2, when the amount of the acid aqueous solution used for hydrolyzing the hydrolyzable silane is changed with respect to the hydrolyzable silane, the structure of the silica structure to be obtained is made separately. Can do. That is, if the amount of the acid aqueous solution used for the hydrolyzable silane is reduced within the above range, the silica structure takes a cylinder structure, and the amount of the acid used for the hydrolyzable silane is increased within the above range. As it goes on, it changes from a cylinder structure to a sphere structure through a co-continuous structure. On the other hand, even if the amount (mixing amount) of hydrolyzable silane with respect to the concentration of the block copolymer in the organic solution of the copolymer and the hydrolyzate is changed (mixed amount), there is no significant structural change in the resulting silica structure. I can't.

Next, the structure of the silica structure produced when a nonpolar organic solvent is used as the organic solvent will be specifically described.
When a nonpolar organic solvent is used as the organic solvent, water required for hydrolysis and the nonpolar organic solvent can be mixed uniformly. It is preferable to carry out. When the obtained hydrolyzate is added to a copolymer organic solution in which a block copolymer is dissolved in a nonpolar organic solvent, a composite is obtained. At this time, as shown in FIG. 3, when the amount of the hydrolyzate added to the diblock copolymer is changed, the structure of the resulting silica structure can be made differently. That is, if the addition amount of the hydrolyzate with respect to the diblock copolymer is increased within the above range, the sphere structure changes to the spherulite lamella structure and the lamella structure. In the case of a lamella structure, it can have different folding parts depending on hydrolysis conditions such as stirring time during hydrolysis. Specifically, when the hydrolysis time of the hydrolyzable silane is short, that is, when the hydrolysis time is short (hydrolysis reactivity is small), when it is added to the copolymer solution, it first becomes a transparent solution, and for a certain period of time. After the elapse of time, it becomes cloudy and a complex is formed. In this case, the obtained silica structure becomes a spherulite lamellar structure which is a lamellar structure having a particulate shape. On the other hand, if the stirring time of hydrolysis of the hydrolyzable silane is long (the degree of hydrolysis reactivity is large), it becomes cloudy when added to the copolymer solution and a composite is obtained. In this case, the obtained silica structure has a general lamellar structure. Although this lamellar structure has a uniform layer thickness, there is no regularity in the shape (morphology) and folding structure.
Moreover, when the pH of the aqueous solution of the acid used as the hydrolysis catalyst of hydrolyzable silica is changed, specifically, the structure of the silica structure can be made differently by changing the strength of the acid. Specifically, when the pH of the aqueous solution, which is the strength of the acid, is increased, for example, when the pH is 1.7 or 2.6, the silica structure takes a lamellar structure. On the other hand, when the pH of the aqueous solution is reduced, for example, when it is adjusted to pH-0.3 (2N hydrochloric acid), the silica structure takes a co-continuous structure.

  Thus, when using a nonpolar organic solvent, the amount of hydrolyzate added to the diblock copolymer, the hydrolysis time, and the pH of the hydrolysis catalyst are changed to change the sphere structure to the spherulite lamellar structure and Through the lamellar structure, it can be made up to a co-continuous structure.

In the method for producing a silica structure of the present invention, the self-assembly and hydrolysis of the composite are then performed in an organic solvent, that is, in an organic solvent in which a copolymer solution and a hydrolyzate of hydrolyzable silane are mixed. A step of performing a polycondensation reaction of the product to obtain a phase separation composite of the diblock copolymer and silica is carried out. In this step, preferably, after the copolymer solution and the hydrolyzate of hydrolyzable silane are mixed, the organic solvent containing the hydrolyzate and the diblock copolymer is stirred or allowed to stand at room temperature or under heating. Etc., preferably by standing. At this time, the time to be stirred or allowed to stand may be a time during which the self-organization and the condensation polymerization reaction proceed, for example, the time when the mixture is sufficiently cloudy or sufficient powdery precipitate is formed, More specifically, for example, it is 0.5 hours to 7 days at room temperature. The heating time of the mixture is not particularly limited, and can be set to the boiling point of the organic solvent or less, for example, from room temperature to 60 ° C. In this way, the composite is self-assembled, and the hydrolyzate is further polycondensed to obtain a phase-separated composite.
As described above, this step is performed by stirring or standing the mixture of the hydrolyzate and the organic solvent, so that the step of forming the composite and the step of obtaining the silica structure are performed separately or It can be carried out continuously, preferably continuously. Thus, the process of obtaining a phase-separated complex in the state and density | concentration as it is can be implemented in the complex in the organic solvent obtained in the process of forming a complex. Therefore, in the step of obtaining this phase separation complex, an organic solvent may be newly added, but without addition, self-organization and polycondensation are performed at the concentration and state of the complex obtained in the step of forming the complex. It is preferred to carry out the reaction.
In this step, the self-assembly of the complex and the condensation polymerization reaction of the hydrolyzate are performed by stirring or standing at room temperature or under heating, and the self-assembly and the condensation polymerization reaction are controlled. In this step, when the hydrolyzate of hydrolyzable silane is used as the solution obtained in the above-described hydrolysis step, the condensation polymerization of the hydrolyzate that has progressed during the hydrolysis of the hydrolyzable silane is further advanced. When the self-assembly of the composite and the condensation polymerization reaction of the hydrolyzate proceed, the mixture becomes cloudy and becomes a dispersed state, or a powdery precipitate is generated. Therefore, in this step, the self-assembly of the composite and the polycondensation reaction of the hydrolyzate are allowed to proceed until the mixture is sufficiently cloudy or has a sufficient powdery precipitate.

  In the method for producing a silica structure of the present invention, the obtained phase separation composite is then collected by a solid-liquid separation means such as filtration and dried if desired, and then the diblock copolymer contained in the phase separation composite is contained. A step of removing the polymer is performed. This process includes, for example, a process of heating the phase-separated complex to a temperature equal to or higher than the temperature at which the diblock copolymer is burned out, for example, 500 ° C. or higher. The heating time is appropriately set. When the phase-separated composite is heated, both the diblock copolymer, that is, the polar block (B) and the low polarity block (A) are pyrolyzed, and the existing region of the diblock copolymer becomes pores or voids, and silica remains. Thus, a silica structure is manufactured.

  In this way, for example, a powdery silica structure having a particle size of 20 nm to 30 μm can be produced. The measuring method of the particle size is based on the measurement result by observation with an electron microscope.

  The method for producing a silica structure of the present invention is a production method carried out in an organic solvent using microphase separation of a complex of a diblock copolymer and a hydrolyzate and a condensation polymerization reaction of the hydrolyzate. . Depending on the selection of the organic solvent, the amount of hydrolyzate added to the diblock body, the hydrolysis time or pH of the hydrolyzable silica, or the amount of acid used during hydrolysis with respect to the hydrolyzable silane The structure can be divided into a bicontinuous structure, a lamellar structure, a cylinder structure, or a sphere structure.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

<Diblock copolymer>
As a polystyrene-poly (4-vinylpyridine) block copolymer (hereinafter abbreviated as PS-P4VP), the number average molecular weight of a PS block manufactured by Polymer Source is 11,800 (the number of polymerization is about 113), and a P4VP block. The number average molecular weight of 11,500 (the number of polymerization is about 109) was used. This PS-P4VP was previously dissolved in the following solvent and used as a copolymer solution.
Moreover, hydrochloric acid was diluted with pure water in advance to prepare 2N hydrochloric acid and dilute hydrochloric acid adjusted to pH 2.6.

<Example 1>
As hydrolyzable silane, 0.50 g of tetraethoxysilane (TEOS), 0.4 g of dilute hydrochloric acid water, and 2.5 mL of ethanol were placed in a beaker and stirred at 60 ° C. for 2 hours to prepare a hydrolyzate of hydrolyzable silane. . A copolymer solution in which PS-P4VP (0.025 g) was dissolved in toluene (2.5 mL) as a solvent was prepared. 3 mL of the hydrolyzate was added to the copolymer solution and stirred at 25 ° C. for 1 hour. Thus, the process of forming a composite was implemented. In this step, when a hydrolyzate was added, the hydrolyzate was adsorbed on the poly (4-vinylpyridine) block of PS-P4VP to form a complex of the hydrolyzate and block copolymer, which became cloudy.
The stirring of the organic solvent, that is, the mixture of the hydrolyzate and the copolymer solution is stopped, and the mixture is allowed to stand at 25 ° C. for 1 day or longer to advance the self-assembly of the complex and the condensation polymerization reaction of the hydrolyzate. The phase-separated composite was formed as a powdery aggregate. Thus, the process of obtaining a phase-separation composite_body | complex was implemented.
The resulting phase separation complex (aggregates and precipitates in the mixture) was collected by filtration. The collected phase separation composite was dried and then heated at 550 ° C. for 4 hours to remove the block copolymer. Thus, the process of removing a diblock copolymer was implemented, and the powdery silica structure (0.0970g) was obtained. When the obtained silica structure was observed with a scanning electron microscope (SEM), it was found that the silica structure was a silica structure having a lamellar structure with a thickness of about 15 nm as shown in FIG. It was. The obtained silica structure has a lamellar structure having a fold part peculiar to organic polymer materials, and no material having such a fold structure as a silica structure has been reported so far. The silica structure having such a structure has characteristic birefringence and can be applied to a wide range of applications as described above, and is useful for applications such as optical material elements.

<Example 2>
Example 2 is an experimental example in which the hydrolysis catalyst is less than in Example 1 and the hydrolysis time of tetraethoxysilane is shorter than in Example 1.
In the same manner as in Example 1, 0.5 g of tetraethoxysilane (TEOS), 0.2 g of dilute hydrochloric acid water, and 2.5 mL of ethanol were placed in a beaker and stirred at 60 ° C. for 15 minutes to obtain a hydrolyzate of hydrolyzable silane. Prepared. A copolymer solution in which PS-P4VP (0.025 g) was dissolved in toluene (2.5 mL) as a solvent was prepared. 3 mL of hydrolyzate was added to the copolymer solution. Immediately after the addition, the mixed solution was a colorless and transparent solution, and further agitated at 25 ° C. for 1 hour to form a complex of silica and a block copolymer, which became cloudy.
Stirring of the mixture of hydrolyzate and copolymer solution is stopped, and the mixture is allowed to stand at 25 ° C. for 1 day or more, so that the self-assembly of the complex and the polycondensation reaction of the hydrolyzate proceed, and phase separation is performed. The composite was formed as a powdery aggregate.
The resulting phase separation complex was collected by filtration. The collected phase separation composite was dried and then heated at 550 ° C. for 4 hours to remove the block copolymer. In this way, a powdery silica structure (0.0137 g) was obtained. SEM observation of the obtained silica structure revealed that this silica structure was a spherical silica structure having a lamellar structure with a thickness of about 15 nm, as shown in FIG. The obtained particles of 1 μm to 5 μm are arranged so that the lamellar structure spreads radially. This is a spherulite lamellar structure peculiar to organic polymer materials, and no such material has been reported as a silica structure. The silica structure having such a structure has characteristic birefringence and can be applied to a wide range of applications as described above, and is useful for applications such as optical material elements.

<Example 3>
Example 3 is an experimental example in which the amount of hydrolyzate added is smaller than that in Example 1.
Tetraethoxysilane (TEOS) 0.5 g, dilute hydrochloric acid water 0.4 g, and ethanol 2.5 mL were placed in a beaker and stirred at 60 ° C. for 30 minutes to prepare a hydrolyzate of hydrolyzable silane. A copolymer solution in which PS-P4VP (0.025 g) was dissolved in toluene (2.5 mL) as a solvent was prepared. The copolymer solution was kept at 60 ° C., 1.5 mL of the hydrolyzate was slowly added, and the mixture was stirred at 25 ° C. for 1 hour. At this time, a composite of silica and a block copolymer was formed and became cloudy immediately after mixing the two solutions.
Stirring of the mixture of hydrolyzate and copolymer solution is stopped, and the mixture is allowed to stand at 25 ° C. for 1 day or more, so that the self-assembly of the complex and the polycondensation reaction of the hydrolyzate proceed, and phase separation The composite was formed as a powdery aggregate.
The resulting phase separation complex was collected by filtration. The collected phase separation composite was dried and then heated at 550 ° C. for 4 hours to remove the block copolymer. In this way, a powdered silica structure (0.0700 g) was obtained. According to SEM observation of the obtained silica structure, this silica structure has a structure in which silica nanoparticles of about 30 nm are regularly arranged in a three-dimensional manner at regular intervals, as shown in FIG. I understood. In this silica structure, the silica phase had a sphere structure (body-centered legislation (BBC) structure). That is, this sphere structure is such that the phase-separated complex covers the silica adsorbed by P4VP, which is the polar block (B) of the diblock copolymer, with PS, which is another low-polar block (A). This is caused by taking various forms. A silica structure having such a sphere structure cannot be produced by a method for producing a mesoporous material using a micelle structure of a surfactant, and the sphere structure is obtained by microphase separation and hydrolysis of a composite in an organic solvent. It is a unique structure that can be formed by the method for producing a silica structure of the present invention using a condensation polymerization reaction of a decomposition product. Since the silica structure having such a structure has a large surface area, it can be applied to a wide range of applications as described above. For example, it is useful for applications such as increasing the sensitivity of a sensor.

<Example 4>
Example 4 is an experimental example in which the amount of the acid aqueous solution used as the hydrolysis catalyst is higher than that in Example 1.
Prepare hydrolyzate of hydrolyzable silane by taking 0.5g of tetraethoxysilane (TEOS) as hydrolyzable silane, 0.2g of 2N hydrochloric acid and 2.5mL of ethanol in a beaker and stirring at 60 ° C for 30 minutes. did. A copolymer solution in which PS-P4VP (0.025 g) was dissolved in toluene (2.5 mL) was prepared. 3 mL of the hydrolyzate was slowly added to the copolymer solution and stirred at 25 ° C. for 1 hour. Immediately after stirring the mixed solution, a complex of silica and a block copolymer was formed and became cloudy.
Stirring of the mixture of hydrolyzate and copolymer solution is stopped, and the mixture is allowed to stand at 25 ° C. for 1 day or more, so that the self-assembly of the complex and the polycondensation reaction of the hydrolyzate proceed, and phase separation is performed. The composite was formed as a powdery silica composite.
The resulting phase separation complex was collected by filtration. The collected phase separation composite was dried and then heated at 550 ° C. for 4 hours to remove the block copolymer. In this way, a powdery silica structure (0.0105 g) was obtained. SEM observation of the obtained silica structure revealed that this silica structure had a co-continuous structure (gyroidal structure) as shown in FIG. The silica structure having such a structure can be easily applied to a wide range of applications as described above because it is easy to change the substance in the pores. For example, it is useful for applications such as adsorbents and catalyst carriers.

<Example 5>
Example 5 is an experimental example using dimethylformamide (DMF), which is a polar solvent, different from toluene, which is a nonpolar solvent used in Examples 1 to 4.
As a hydrolyzate of hydrolyzable silane, 0.25 g of tetraethoxysilane (TEOS), 0.4 g of dilute hydrochloric acid water adjusted to pH 2.6 in advance, and 2.5 mL of dimethylformamide (DMF) are placed in a beaker and heated at 60 ° C. for 1 hour. A hydrolyzate of hydrolyzable silane was prepared by stirring. A copolymer solution in which PS-P4VP (0.125 g) was dissolved in DMF (2.5 mL) as a solvent was prepared. When 3.2 mL of the hydrolyzate was added to the copolymer solution at 25 ° C., the mixed solution was colorless and transparent. Then, it stirred at 25 degreeC for 1 hour.
Stirring of the mixture of hydrolyzate and copolymer solution is stopped, and the mixture is allowed to stand at 25 ° C. for 3 days or more, so that the self-assembly of the complex and the polycondensation reaction of the hydrolyzate proceed, and phase separation The composite was formed as a powdery aggregate.
The resulting phase separation complex was collected by filtration. The collected phase separation composite was dried and then heated at 550 ° C. for 4 hours to remove the block copolymer. In this way, a powdered silica structure (0.0701 g) was obtained. According to SEM observation of the obtained silica structure, this silica structure was a fine particle having a hexagonal column shape as shown in FIG. Each particle was found to have a hexagonal symmetric cylinder structure called a hexagonal structure in which pores having a linear channel shape having an inner diameter of about 10 nm. The particle size was 400 to 800 nm, and it was found that all particles had the same structure. The particle diameter is a value measured based on an image obtained by SEM observation. The silica structure having such a structure has the properties of a porous material having a uniform pore diameter, and can be applied to the wide range of applications described above, for example, for applications such as adsorbents, separation membranes, and catalyst carriers. Useful.

<Example 6>
Example 6 is an experimental example in which the amount of the acid aqueous solution used as the hydrolysis catalyst is larger than that of Example 5 among the experimental examples performed with the polar solvent DMF.
In the same manner as in Example 5, 0.5 g of tetraethoxysilane (TEOS), 0.8 g of dilute hydrochloric acid water and 2.5 mL of dimethylformamide (DMF) were placed in a beaker and stirred at 60 ° C. for 30 minutes. A hydrolyzate was prepared. A copolymer solution in which PS-P4VP (0.125 g) was dissolved in DMF (2.5 mL) as a solvent was prepared. When 3.2 mL of the hydrolyzate was added to the copolymer solution at 25 ° C., the mixed solution was colorless and transparent. Then, it stirred at 25 degreeC for 1 hour.
Stirring of the mixture of hydrolyzate and copolymer solution is stopped, and the mixture is allowed to stand at 25 ° C. for 3 days or more, so that the self-assembly of the complex and the polycondensation reaction of the hydrolyzate proceed, and phase separation The composite was formed as a powdery aggregate.
The resulting phase separation complex was collected by filtration. The collected phase separation composite was dried and then heated at 550 ° C. for 4 hours to remove the block copolymer. In this way, a powdery silica structure (0.0724 g) was obtained. As a result of SEM observation of the obtained silica structure, as shown in FIG. 10, this silica structure has a sphere structure (body-centered (BBC) structure in which spherical pores having an inner diameter of about 20 nm are continuously connected). ) This is a reverse phase of the sphere structure of the silica phase of Example 3. That is, this sphere structure is due to the fact that the phase-separated complex is in such a form that the hydrolyzate adsorbed on the P4VP block of the diblock copolymer covers the periphery of the PS block. A silica structure having such a structure has the properties of a porous material having a uniform pore diameter, and can be applied to a wide range of applications as described above. For example, it is useful for applications such as a catalyst carrier for precision synthesis. is there.

<Reference Example 1>
In the step of forming a complex in the method for producing a silica structure of the present invention, it was confirmed by IR spectrum that the hydrolyzate was adsorbed on the P4VP block which is the polar block (B) of the diblock body.
The spectrum of PS-P4VP alone was also measured. As a result, a single PS-P4VP has five characteristic peaks, each having 2 peaks (1452 cm ⁻¹ and 1493 cm ⁻¹ ) due to the PS block and 3 peaks (1415 cm ⁻¹ , 1556 cm) due to P4VP. ⁻¹ and 1597 cm ⁻¹ ).
A composite was prepared in the same manner as in Example 1 (using toluene solvent) and Example 6 (using DMF solvent), and after washing and drying, an infrared absorption spectrum was measured. The spectrum chart is shown in FIG. In the complexes prepared in both solvents, only the peak due to P4VP was shifted to the short wavelength side. This suggests that the hydrolyzate was adsorbed on the P4VP block.

Claims (9)

In an organic solvent, it is incompatible with the hydrolyzate of hydrolyzable silane, the polar block (B) having a solubility parameter (SP value) of 22 to 25 (MPa ^1/2 ), and the polar block (B). Mixing a diblock copolymer having a low polarity block (A) to form a complex in which the hydrolyzate is adsorbed on the polar block (B);
In the organic solvent, performing a self-assembly of the complex and a condensation polymerization reaction of the hydrolyzate to obtain a phase-separated complex of the diblock copolymer and silica;
And a step of removing the diblock copolymer from the obtained phase-separated composite.   The step of forming the complex has a step of mixing a copolymer organic solution containing the block copolymer and the organic solvent and a hydrolyzate obtained by hydrolyzing the hydrolyzable silane. Item 2. A method for producing a silica structure according to Item 1.   The step of obtaining the phase-separated complex is a step of performing the self-organization and the condensation polymerization reaction by standing or stirring the organic solvent containing the hydrolyzate and the diblock copolymer. Item 3. A method for producing a silica structure according to Item 1 or 2.   The method for producing a silica structure according to any one of claims 1 to 3, wherein the step of forming the composite and the step of obtaining the phase-separated composite are carried out continuously.   The method for producing a silica structure according to any one of claims 1 to 4, wherein the polar block (B) has a polyvinylpyridine block.   The method for producing a silica structure according to any one of claims 1 to 5, wherein the polar block (B) does not contain a polyalkylene oxide block.   The said low polarity block (A) is a polystyrene block, The manufacturing method of the silica structure of any one of Claims 1-6.   A powdery silica structure produced by the method for producing a silica structure according to claim 1 and having a three-dimensional regular structure by a microphase separation structure of the diblock copolymer. The silica structure according to claim 8, wherein the microphase separation structure is a co-continuous structure, a lamellar structure, a cylinder structure, or a sphere structure.