JP5095288B2 - Polymer / silica composite nanostructure, polymer / metals / silica composite nanostructure, and method for producing silica-based inorganic structure - Google Patents

Description

  In the present invention, a crystalline aggregate formed in an aqueous medium of a polymer having a linear polyethyleneimine skeleton is used as a reaction field, and by mixing water glass therewith, the polymer and silica are combined in nanometer order. Method of manufacturing the structure (hereinafter referred to as nanostructure in the present invention), and further, metal ions and metal nanoparticles of the order of several nanometers (hereinafter referred to as metal ions and metal nanoparticles) in the polymer / silica composite structure. The present invention relates to a method for producing a polymer / metal / silica composite nanostructure containing particles) and a method for producing a silica-based inorganic structure obtained by thermally firing these.

  Silicon is the second most abundant existence after oxygen on the earth's crust, and natural quartz, quartz, opal, mica, diatoms, etc. are well-known oxides of silicon. The creation of a silica material having a regular spatial structure or pattern structure is a major research subject in the field of material science, and technological development related to this has greatly advanced.

  As a method for expressing a certain structure in a silica material, a method in which a molecular organization is used as a template (template) and silica is fixed around the organization is widely used in the field. For this template, a surfactant (for example, see Non-Patent Document 1), a block polymer (for example, see Non-Patent Document 2), a virus, a bacterium (for example, see Non-Patent Document 3), or the like is used. Silica having nano cavities synthesized using these as templates, for example, MCM-41 (mesoporous) series materials, can be applied to catalysts, electronic materials, nanofilters, biotechnology, and the like. With regard to these materials, studies have been conducted for more precise control of the structure, and the size and arrangement of the cavities or the control of cavities in spherical silica are being studied.

  On the other hand, in parallel with such control of nanocavities, a technique for controlling the shape of silica from nano to micron and even macro scale is attracting attention. This is partly due to the enlightenment of biosilica in ecosystems (see Non-Patent Document 4, for example). Diatoms can be taken up as natural biosilica. Diatoms are composed of silica and have complex and precise shapes and patterns. Proteins or polypeptides are involved in the construction of the silica (see, for example, Non-Patent Document 5), but these act as a catalyst for the silica immobilization reaction or provide a scaffold for silica shape growth. To do. One of the indispensable chemical structures for the formation of such biological biosilica is a long-chain polyamine. The polyamine works by being incorporated into a peptide structure or works together with the polypeptide as a polyamine having a constant molecular weight by itself (see, for example, Non-Patent Document 6).

  As described above, it has been widely known in recent years that a silica source such as silicic acid, sodium silicate or alkoxysilane can be immobilized as silica gel at room temperature in the presence of polyamine. However, since they are usually made by dissolving polyamine in water and sol-gel reaction of silica source in the aqueous solution, even if silica gel can be formed, the shape of the silica gel cannot be controlled, and regular. It was difficult to realize a silica gel having a simple structure.

  Unlike the above method, the present inventors have used silica nanofibers by using, as a reaction field for silica precipitation, a unique molecular aggregate in which a linear polyethyleneimine composed of a secondary amine is expressed in an aqueous medium. The present inventors have found silica-containing nanostructures having various shapes typified by (1) and methods for producing the same (see Patent Documents 1 to 4). In these inventions, when a polymer having a linear polyethyleneimine skeleton is spontaneously associated in water and then mixed with a silane compound of alkoxysilanes in the associated fluid, the silanes are selectively polymerized. The present invention has been completed by finding that a nanostructure in which a polymer and silica are combined is produced by hydrolytic condensation on the surface of the aggregate. This process is highly efficient for controlling the structure of the silica-based nanostructure, but the silica source used is alkoxysilanes. Therefore, since the alkoxysilanes are expensive, the production cost of the nanostructure to be produced is high, and further alcohols are generated by hydrolysis of the alkoxysilanes. Is inevitable. If a silica nanostructure can be constructed with an inexpensive and carbon-free water glass, it has an important industrial significance.

C. T.A. Kresge et al. , Nature, 1992, 359, p. 710 A. Monnier et al. , Science, 1993, 261, p1299 S. A. Davis et al. , Nature, 1997, 385, p420. W. E. G. Muller Ed. , Silicon Biomineralization: Biology-Biotechnology-Molecular Biology-Biotechnology, 2003, Springer N. Kroger et al. Science, 1999, 286, p. 1129 N. Kroger et al. , Proc. Natl. Acad. Sci. USA, 2000, 97, p14133 JP 2005-264421 A JP 2005-336440 A JP 2006-063097 A JP 2007-051056 A

  The problems to be solved by the present invention include a polymer / silica composite nanostructure having various shapes, a polymer / metals / silica composite nanostructure, and a process that is low in production cost and does not generate organic waste. An object of the present invention is to provide a simple method for producing a silica-based inorganic structure obtained by calcining these.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a template, a crystalline aggregate formed by a specific polymer in water was used, and the pH was adjusted in advance under conditions where the polymer was stably present. When mixed with water glass, the silicon of water glass was precipitated as silica around the aggregate, and it was found that a nanostructure in which a polymer and silica were combined without generation of organic substances was completed.

  That is, the present invention comprises a polymer (A) having a linear polyethyleneimine skeleton (a1) as a crystalline aggregate in an aqueous medium, and water glass (B) having a pH adjusted to 8.5 or higher. A method of producing a polymer / silica composite nanostructure characterized by mixing to precipitate silica (b1), and further, metal ions (c1) or metal nanoparticles (c2) are added to the polymer / silica composite nanostructure. The present invention provides a method for producing a polymer / metal / silica composite nanostructure contained therein, and a method for producing a silica-based inorganic structure obtained by thermally firing these.

  The production method of the present invention uses a water glass which is industrially cheapest and highly versatile as a silica source, and is a simple and non-waste organic matter polymer / silica composite nanostructure and polymer / metals / silica composite. A nanostructure is obtained. The nanostructure obtained from this manufacturing method is a silica-based material mainly composed of silica, in which unit structures such as nano-dimensional fibers and lamellas are widely spread in a three-dimensional space and have various complex shapes and structures. .

  Since the polymer / silica composite nanostructure obtained by the present invention contains a polymer having a linear polyethyleneimine skeleton in the silica, the function inherent to the polymer can be utilized. For example, since polyethyleneimine can form a polymer metal complex with metal ions, the polymer / silica composite nanostructure of the present invention can be used for concentration / separation of metal ions and fixation of metal complexes. A silica / silica composite nanostructure.

  In addition, since polyethyleneimine can form an acid / base complex with an acidic organic compound, a biopolymer having an acidic functional group, or the like, the polymer / silica composite nanostructure of the present invention is capable of separating many acidic substances. Can be used for fixation.

  In addition, since polyethyleneimine has fungicidal and antiviral functions, the polymer / silica composite nanostructure and the polymer / metals / silica composite nanostructure obtained in the present invention are, for example, antibacterial agents, fungicides, It can be used as a virus or cosmetic additive.

  Furthermore, since the polymer / silica composite nanostructure obtained by the present invention has a characteristic of being composed of entangled silica nanofibers, it can also be used as a nanofilter for purifying water and air.

  In addition, the silica-based inorganic structure obtained by firing the polymer / silica composite nanostructure or the polymer / metals / silica composite nanostructure has a high specific surface area and is suitable for filters, catalyst supports, fillers, and the like. It can be used for.

  In the present invention, a water glass (B) having a pH of 8.5 or more adjusted by using a polymer (A) having a linear polyethyleneimine skeleton (a1) as a crystalline aggregate in an aqueous medium and using this as a template. ) To precipitate the silica (b1) around the aggregate, thereby combining the polymer (A) and silica (b1) to obtain a nanostructure.

  In the production of a structure containing silica, a reaction without using alkoxysilanes must be realized in order to eliminate disposal of organic substances into the environment. This is very difficult to construct silica-containing nanostructures that have a certain shape and structure in three-dimensional space.

  A nanostructure in which a polymer and silica are composited is basically generated by a specific structure formed by a polymer in a medium functioning as a template for depositing silica. The more stable the shape of the polymer template, the more stable the resulting polymer / silica composite nanostructure will have a distinct nanostructure.

  Specifically, in order to make silica into a specific shape, the following three conditions are required: (1) the polymer template that induces the shape is stably formed, and (2) the template can concentrate the silica source. (3) The template needs to promote the polymerization of the silica source. At this time, when alkoxysilane was used for the silica source, this condition was satisfied for a relatively wide range of polymers, which was advantageous for obtaining a composite nanostructure having a controlled structure. Silica sources in place of alkoxysilanes are only water-soluble silicates (sodium silicate, potassium silicate, etc.) or water-dispersed silica colloidal particles. When such a silica source is used, it is considered that the problem of disposal of alcohols caused by hydrolysis of alkoxysilane into the environment can be solved. However, when water-soluble silicates are used, water glass, which is a concentrated solution, is water-soluble, but it becomes unstable due to minute changes in the aqueous medium (for example, changes in pH, mixing of additives, etc.), and spontaneous As long as the polymer template and water glass cannot be stably mixed, the silica is precipitated by concentrating the silicate on the template surface, so that the polymer / silica composite nanostructure is deposited. It is impossible to get a body.

  In the present invention, in order to solve the above-described problems, a crystalline aggregate formed in an aqueous medium by a polymer (A) having a linear polyethyleneimine skeleton (a1) is used as a template. The polymer (A) having a linear polyethyleneimine skeleton (a1) is soluble in water, but exists as a crystalline molecular aggregate at room temperature. When the water glass (B) whose pH is adjusted to 8.5 or more is mixed here, the stability of the crystalline aggregate is maintained and the silica in the aqueous medium containing the crystalline aggregate is maintained. It is possible to prevent precipitation of the silicate itself, and the silicate has been found to selectively precipitate as silica (silicon oxide) (b1) around the template using this crystalline aggregate as a template. The present invention has been completed.

  The nanostructure obtained in the present invention is a composite of a polymer (A) having a linear polyethyleneimine skeleton and silica (b1), and the nanostructure becomes a space depending on the hardness of silica (b1). Has a wide variety of shapes.

[Polymer having linear polyethyleneimine skeleton]
The linear polyethyleneimine skeleton (a1) referred to in the present invention is a polymer skeleton having an ethyleneimine unit of a secondary amine as a main structural unit. In the skeleton (a1), structural units other than the ethyleneimine unit may be present, but in order to form a crystalline aggregate, a constant chain length in the polymer skeleton (a1) is continuous. Preferably, the ethyleneimine unit. The length of the linear polyethyleneimine skeleton (a1) is not particularly limited as long as the polymer (A) having the skeleton can form a crystal, but in order to form a crystal suitably, the skeleton ( The number of repeating units of the ethyleneimine unit in the a1) part is preferably 10 or more, particularly preferably in the range of 20 to 10,000.

  The polymer (A) used in the present invention is not particularly limited as long as it has a linear polyethyleneimine skeleton (a1) in its structure, and the overall shape of the polymer (A) is linear, star-shaped or comb-shaped. Even in such a case, the crystalline aggregate can be provided in water or an aqueous medium that is a mixed solvent of water and a hydrophilic organic solvent (hereinafter, both are collectively referred to as an aqueous medium).

  In addition, these linear, star-like or comb-like polymers may be composed of only a linear polyethyleneimine skeleton (a1) or a block composed of a linear polyethyleneimine skeleton (a1) (hereinafter referred to as polyethyleneimine). It may be composed of a block copolymer of abbreviated as a block) and other polymer blocks. Other polymer blocks include, for example, water-soluble polymer blocks such as polyethylene glycol, polypropionylethyleneimine, polyacrylamide, or polystyrene, polyoxazoline polyphenyloxazoline, polyoctyloxazoline, polydodecyloxazoline, polyacrylates And hydrophobic polymer blocks such as polymethyl methacrylate and polybutyl methacrylate. By using a block copolymer with these other polymer blocks, the shape of the crystalline aggregate formed from the polymer and the characteristics of the resulting nanostructure can be adjusted.

  When the polymer (A) having a linear polyethyleneimine skeleton is a block copolymer, the proportion of the linear polyethyleneimine skeleton (a1) in the polymer (A) is within a range where a crystalline aggregate can be formed. Although not particularly limited, in order to suitably form the aggregate, the proportion of the linear polyethyleneimine skeleton (a1) in the polymer (A) is preferably 40 mol% or more, and 50 mol% or more. More preferably.

  The polymer (A) having the linear polyethyleneimine skeleton (a1) is an acidic polymer (hereinafter abbreviated as precursor polymer) having a linear skeleton composed of polyoxazolines serving as a precursor. It can be easily obtained by hydrolysis under the conditions or alkaline conditions. Accordingly, the shape of the polymer (A) having the linear polyethyleneimine skeleton (a1) such as a linear shape, a star shape, or a comb shape can be easily designed by controlling the shape of the precursor polymer. . Further, the degree of polymerization and the terminal structure can be easily adjusted by controlling the degree of polymerization and the terminal functional group of the precursor polymer. Further, when forming a block copolymer having a linear polyethyleneimine skeleton (a1), the precursor polymer is used as a block copolymer, and the linear skeleton composed of polyoxazolines in the precursor is selectively hydrolyzed. It can be obtained by decomposing.

  The precursor polymer can be synthesized by a cationic polymerization method or a synthesis method such as a macromonomer method using an oxazoline monomer. By selecting an appropriate synthesis method and initiator, a linear polymer can be obtained. It is possible to synthesize precursor polymers having various shapes such as a star shape or a comb shape.

  Oxazoline monomers such as methyl oxazoline, ethyl oxazoline, methyl vinyl oxazoline, and phenyl oxazoline can be used as the monomer that forms a linear skeleton composed of polyoxazolines.

  As the polymerization initiator, a compound having a functional group such as an alkyl chloride group, an alkyl bromide group, an alkyl iodide group, a toluenesulfonyloxy group, or a trifluoromethylsulfonyloxy group in the molecule can be used. These polymerization initiators can be obtained by converting the hydroxyl groups of many alcohol compounds into other functional groups. Of these, brominated, iodinated, toluene sulfonated, and trifluoromethyl sulfonated compounds are preferred as functional group conversion because of their high polymerization initiation efficiency, especially alkyl bromide groups and toluene sulfonate alkyl groups. Is preferred.

  Moreover, what converted the terminal hydroxyl group of poly (ethylene glycol) into bromine or iodine, or converted into a toluenesulfonyl group can also be used as a polymerization initiator. In that case, the degree of polymerization of poly (ethylene glycol) is preferably in the range of 5 to 100, particularly preferably in the range of 10 to 50.

  Also, dyes having a functional group having the ability to initiate cationic ring-opening living polymerization and having a skeleton of any of a porphyrin skeleton, a phthalocyanine skeleton, or a pyrene skeleton having a light emission function, an energy transfer function, and an electron transfer function by light Can impart a special function to the resulting polymer (A) and nanostructure.

  The linear precursor polymer is obtained by polymerizing the oxazoline monomer with a polymerization initiator having a monovalent or divalent functional group. Examples of such a polymerization initiator include methyl benzene, methyl benzene bromide, methyl benzene iodide, methyl benzene toluene sulfonate, methyl benzene trifluoromethyl sulfonate, methane bromide, methane iodide, toluene sulfonic acid. Monovalent ones such as methane or toluenesulfonic anhydride, trifluoromethylsulfonic anhydride, 5- (4-bromomethylphenyl) -10,15,20-tri (phenyl) porphyrin, or bromomethylpyrene, dibromo Divalent ones such as methylbenzene, diiodomethylbenzene, dibromomethylbiphenylene, or dibromomethylazobenzene can be mentioned. In addition, linear polyoxazolines that are industrially used such as poly (methyloxazoline), poly (ethyloxazoline), or poly (methylvinyloxazoline) can be used as a precursor polymer as they are.

  The star-shaped precursor polymer is obtained by polymerizing the oxazoline monomer as described above with a polymerization initiator having a trivalent or higher functional group. Examples of the trivalent or higher polymerization initiator include trivalent compounds such as tribromomethylbenzene, tetravalent compounds such as tetrabromomethylbenzene, tetra (4-chloromethylphenyl) porphyrin, tetrabromoethoxyphthalocyanine, hexa Examples thereof include pentavalent or higher valent compounds such as bromomethylbenzene and tetra (3,5-ditosilylethyloxyphenyl) porphyrin.

  In order to obtain a comb-like precursor polymer, it is obtained by polymerizing an oxazoline monomer from the polymerization initiating group using a linear polymer having a polyvalent polymerization initiating group. It can also be obtained by halogenating a hydroxyl group of a polymer having a plurality of hydroxyl groups in a side chain such as a resin or polyvinyl alcohol with bromine or iodine, or converting it to a toluenesulfonyl group and then using the converted moiety as a polymerization initiating group. be able to.

  As a method for obtaining a comb-like precursor polymer, a polyamine type polymerization terminator can also be used. For example, a monovalent polymerization initiator is used to polymerize oxazoline, and the end of the polyoxazoline is bonded to the amino group of a polyamine such as polyethyleneimine, polyvinylamine, or polypropylamine to obtain a comb-shaped polyoxazoline. Can do.

  Hydrolysis of the linear skeleton portion composed of the polyoxazolines of the precursor polymer obtained as described above may be performed under any of acidic conditions or alkaline conditions. Hydrolysis under acidic conditions can obtain polyethyleneimine hydrochloride by, for example, stirring the precursor polymer under heating in an aqueous hydrochloric acid solution. By treating the obtained hydrochloride with excess ammonium water, a crystalline polymer powder having a basic polyethyleneimine skeleton can be obtained. The hydrochloric acid aqueous solution used may be concentrated hydrochloric acid or an aqueous solution of about 1 mol / L, but it is desirable to use a 5 mol / L aqueous hydrochloric acid solution for efficient hydrolysis. The reaction temperature is preferably around 80 ° C.

  For hydrolysis under alkaline conditions, for example, by using an aqueous sodium hydroxide solution, a skeleton composed of polyoxazolines can be converted into a polyethyleneimine skeleton. After reacting under alkaline conditions, the reaction solution is washed with a dialysis membrane to remove excess sodium hydroxide and to obtain a polymer crystal powder having a polyethyleneimine skeleton. The concentration of sodium hydroxide to be used may be in the range of 1 to 10 mol / L, and is preferably in the range of 3 to 5 mol / L in order to perform a more efficient reaction. The reaction temperature is preferably around 80 ° C.

  The amount of acid or alkali used in hydrolysis under acidic conditions or alkaline conditions may be 1 to 10 equivalents relative to the oxazoline unit in the precursor polymer, which improves reaction efficiency and simplifies post-treatment. Therefore, it is preferable to set it as about 3 equivalents.

  By the hydrolysis, a linear skeleton composed of polyoxazolines in the precursor polymer becomes a linear polyethyleneimine skeleton (a1), and a polymer (A) having the polyethyleneimine skeleton (a1) is obtained.

  In the case of forming a block copolymer of a linear polyethyleneimine block and another polymer block, the precursor polymer is a block copolymer composed of a linear polymer block composed of polyoxazolines and another polymer block. And a linear block composed of polyoxazolines in the precursor polymer can be selectively hydrolyzed.

  When the other polymer block is a water-soluble polymer block such as poly (N-propionylethyleneimine), poly (N-propionylethyleneimine) is converted to poly (N-formylethyleneimine) or poly (N-acetyl). A block copolymer can be formed by taking advantage of its higher solubility in organic solvents than ethyleneimine). That is, 2-oxazoline or 2-methyl-2-oxazoline is subjected to cationic ring-opening living polymerization in the presence of the above-described polymerization initiating compound, and then 2-ethyl-2-oxazoline is further polymerized to the obtained living polymer. Thus, a precursor polymer composed of a poly (N-formylethyleneimine) block or a poly (N-acetylethyleneimine) block and a poly (N-propionylethyleneimine) block is obtained. The precursor polymer is dissolved in water, and an emulsion is formed by mixing and stirring an organic solvent incompatible with water in which the poly (N-propionylethyleneimine) block is dissolved in the aqueous solution. A linear polyethyleneimine block is obtained by preferentially hydrolyzing a poly (N-formylethyleneimine) block or a poly (N-acetylethyleneimine) block by adding an acid or an alkali to the aqueous phase of the emulsion. And a block copolymer having a poly (N-propionylethyleneimine) block.

  When the valence of the polymerization initiating compound used here is 1 or 2, a linear block copolymer is obtained. When the valence is higher than that, a star-shaped block copolymer is obtained. Further, by making the precursor polymer a multistage block copolymer, the resulting polymer can also have a multistage block structure.

[Crystalline aggregate]
The polymer (A) having the linear polyethyleneimine skeleton (a1) has a structure in which the linear polyethyleneimine skeleton (a1) in the primary structure exhibits crystallinity in an aqueous medium. Induces crystals. The polymer crystals can also form a hydrogel having a three-dimensional network structure by physical bonding between the polymer crystals in the presence of an aqueous medium, and can be chemically obtained by crosslinking the polymer crystals with a crosslinking agent. Crosslinked hydrogels having crosslinks can also be formed.

  Polyethyleneimine that has been widely used heretofore is a branched polymer obtained by ring-opening polymerization of cyclic ethyleneimine, and has primary amine, secondary amine, and tertiary amine in its primary structure. Therefore, branched polyethyleneimine is water-soluble, but has no crystallinity. Therefore, in order to make a hydrogel using branched polyethyleneimine, a network structure must be provided by covalent bonding with a crosslinking agent. However, the linear polyethyleneimine that the polymer used in the present invention has as a skeleton is composed only of a secondary amine, and the secondary amine type linear polyethyleneimine is water-soluble and has excellent crystallinity. Have

  Such linear polyethyleneimine crystals are known to vary greatly in polymer crystal structure depending on the number of water of crystallization contained in the ethyleneimine unit of the polymer (Y. Chatani et al., Macromolecules, 1981). Year, Vol. 14, pages 315-321). Anhydrous polyethylenimine prefers a crystal structure characterized by a double helix structure, but if the monomer unit contains two molecules of water, the polymer is known to grow into a crystal characterized by a zigzag structure. Yes. Actually, the crystal of linear polyethyleneimine obtained from water is a crystal containing bimolecular water in one monomer unit, and the crystal is insoluble in water at room temperature.

  The crystalline aggregate of the polymer (A) having a linear polyethyleneimine skeleton (a1) in the present invention is formed by crystal expression of the linear polyethyleneimine skeleton (a1) as in the above case. Even if the polymer shape is a linear shape, a star shape, a comb shape or the like, if the linear structure has a linear polyethyleneimine skeleton (a1), the crystalline aggregate of the polymer (A) is can get.

  The presence of the crystalline aggregate of the polymer (A) in the present invention can be confirmed by, for example, X-ray scattering, and a scattering peak at 20 °, 27 °, and 28 ° in terms of 2θ angle in a wide angle X-ray diffractometer (WAXS). Indicates.

  In addition, the melting point in the differential scanning calorimeter (DSC) of the polymer (A) crystal in the present invention depends on the structure of the polymer (A) having the linear polyethyleneimine skeleton (a1). Appears at 45-90 ° C.

  The crystalline aggregate of the polymer (A) in the present invention includes the geometric structure of the polymer (A) constituting the crystal, the molecular weight, the non-ethyleneimine moiety introduced into the primary structure, and the conditions for forming the polymer crystal. Various shapes can be taken due to the influence of the above, and for example, it has a shape such as a bundle, a brush, or a star.

  The crystalline aggregate has a fibrous structure of nanometer order of about 5 to 30 nm as a basic unit, and the fibrous structures are hydrogen-bonded by free ethyleneimine chains existing on the surface of the fibrous structure. They are connected to each other by physical coupling and are grown in a three-dimensional shape as described above.

  The crystalline aggregate of the present invention uses the property that the polymer (A) having a linear polyethyleneimine skeleton (a1) is insoluble in water at room temperature, and the polymer having the linear polyethyleneimine skeleton (a1) It can be obtained by dissolving (A) in water-crystal conversion.

  For example, a polymer (A) having a linear polyethyleneimine skeleton (a1) is first dispersed in an aqueous medium, and the dispersion is heated to obtain a transparent solution of the polymer (A). Subsequently, a crystalline aggregate is obtained by cooling the aqueous solution of the polymer (A) in a heated state to room temperature. At this time, as the polymer concentration is higher, the crystalline aggregate has a state like an ice cream and can be formed into various shapes.

  The heating temperature of the aqueous polymer solution is preferably 100 ° C. or less, and more preferably in the range of 90 to 95 ° C. Further, the polymer content (concentration) in the aqueous solution of the polymer is not particularly limited, but is preferably in the range of 0.01 to 20% by mass, in order to obtain a crystalline aggregate composed of a crystal of a stable shape. Is more preferably in the range of 0.1 to 10% by mass. Thus, in the present invention, when the polymer (A) having the linear polyethyleneimine skeleton (a1) is used, a crystalline aggregate can be formed even with a very small polymer concentration.

  The crystal shape in the resulting crystalline aggregate can be adjusted by the process of lowering the temperature of the aqueous polymer solution to room temperature (25 ° C.). For example, the aqueous solution is held at 80 ° C. for 1 hour, then brought to 60 ° C. over 1 hour and held at the temperature for an additional hour. Thereafter, the temperature is lowered to 40 ° C. over 1 hour, and then naturally lowered to room temperature, whereby a hydrogel crystal in which the water of the aqueous solution has lost its fluidity can be obtained. Also, after the aqueous solution of the polymer is cooled at once with freezing water at a freezing point, or with a refrigerant liquid of methanol / dry ice or acetone / dry ice at a temperature below freezing point, the water in that state is kept in a constant temperature bath at room temperature (25 ° C.). A crystalline aggregate can be obtained by holding at. Furthermore, the crystalline aggregate can also be obtained by lowering the temperature of the above aqueous polymer solution to room temperature in a constant temperature bath or room temperature air environment.

  Since the step of lowering the temperature of the aqueous polymer solution strongly affects the shape of the resulting crystalline aggregate, the form of the crystalline aggregate obtained by the different steps is not the same.

  The crystalline aggregate obtained as described above remains insoluble at room temperature, but when heated to a temperature higher than the crystal melting point, the crystal dissociates and changes to a transparent solution. When it is returned to room temperature, it becomes a crystalline aggregate again. Therefore, it is possible to reversibly change the aggregate.

  By adding another water-soluble polymer at the time of adjusting the crystalline aggregate, a crystalline aggregate containing the water-soluble polymer can be obtained. Examples of the water-soluble polymer include polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, poly (N-isopropylacrylamide), polyhydroxyethyl acrylate, polymethyloxazoline, polyethyloxazoline and the like.

  The content of the water-soluble polymer is preferably in the range of 0.1 to 5 times, and in the range of 0.5 to 2 times the mass of the polymer (A) having the linear polyethyleneimine skeleton (a1). Is more preferable.

  By containing the water-soluble polymer, the form of the crystal aggregate can be changed, and a crystal aggregate having a form different from that of a simple system can be provided.

  By treating the crystalline aggregate obtained by the above method with a compound containing two or more functional groups that react with the amino group of polyethyleneimine, the polymers in the aggregate are linked by chemical bonds to crosslink. Can be made.

  Examples of the compound containing two or more functional groups capable of reacting with the amino group at room temperature include aldehyde crosslinking agents, epoxy crosslinking agents, acid chlorides, acid anhydrides, and ester crosslinking agents. Examples of the aldehyde crosslinking agent include malonyl aldehyde, succinyl aldehyde, glutaryl aldehyde, phthaloyl aldehyde, isophthaloyl aldehyde, terephthaloyl aldehyde, and the like. Examples of the epoxy crosslinking agent include polyethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, glycidyl chloride, and glycidyl bromide. Examples of the acid chlorides include malonyl chloride, succinyl chloride, glutaryl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, and the like. Examples of the acid anhydride include phthalic anhydride, succinic anhydride, and glutaric anhydride. Examples of the ester crosslinking agent include malonic acid methyl ester, succinic acid methyl ester, glutaric acid methyl ester, phthaloyl acid methyl ester, and polyethylene glycol carboxylic acid methyl ester.

  The cross-linking reaction can be performed by a method of immersing the obtained crystalline aggregate in a solution of a cross-linking agent or a method of adding a cross-linking agent solution into the crystalline aggregate. At this time, the cross-linking agent permeates into the aggregate as well as changes in the osmotic pressure in the system, where the polymers (A) are connected by hydrogen bonds or cause a chemical reaction with the nitrogen atom of ethyleneimine.

  The cross-linking reaction proceeds even with the reaction with free ethyleneimine on the surface of the crystalline aggregate, but in order to keep it, it is desirable to carry out the reaction at a temperature below the melting point of the crystalline aggregate, and further the cross-linking reaction. It is most desirable to carry out at room temperature.

  When the crosslinking reaction is allowed to proceed at room temperature, a crosslinked hydrogel can be obtained by leaving the crystalline aggregate in a mixed state with the crosslinking agent solution. The time for the crosslinking reaction may be from a few minutes to a few days, and the crosslinking proceeds suitably by leaving it to stand overnight.

  The amount of the crosslinking agent may be 0.05 to 20 mol% with respect to the number of moles of the ethyleneimine unit in the polymer (A) having the polyethyleneimine skeleton (a1) to be used, and it may be 1 to 10 mol%. More preferred.

[Silica sauce]
In the present invention, water glass (B) is used as the silica source. The water glass (sodium silicate or lithium silicate) is not particularly limited as long as it is represented by the general formula Na ₂ O.xSiO ₂ or Li ₂ O.xSiO _2. Can be suitably used.

  The water glass (B) represented by the above formula is usually water-soluble, but its stability is sensitive to pH and can only be a stable solution within a very narrow pH range. For example, an aqueous solution of sodium silicate hardens rapidly when the pH of the aqueous solution is 6.5 or more and less than 8.5, and there is a high possibility that the silica gel is structurally irregular. In the production method of the present invention, the water glass (B) must be used in a stabilized state. For that purpose, it is essential that the pH of the aqueous solution of water glass (B) or water glass (B) is 8.5 or more. For advanced structural control, it is more preferable that the pH of the water glass (B) or the aqueous solution of water glass is 9 to 11.

  In the production method of the present invention, it is preferable to use water glass (B) as an aqueous solution previously diluted to a range of 0.01 to 2.0 mol / L, and in particular, mixed with a crystalline aggregate of polymer (A). It is preferable to make it 0.1-1.0 mol / L from the point which is easy to maintain the stability at the time of doing.

[Polymer / silica composite nanostructure, polymer / metals / silica composite nanostructure]
The polymer / silica composite nanostructure obtained in the present invention is a silica glass source water glass (pH) adjusted in advance in an aqueous dispersion or hydrogel of the crystalline aggregate of the polymer (A). It can be easily obtained by mixing B) or an aqueous solution thereof and allowing the mixture to stand at room temperature to 50 ° C.

  The sol-gel reaction in which water glass (B) is converted to silica (b1) in the above-mentioned mixture that gives the nanostructure must proceed in a state where the crystalline aggregate formed by the polymer (A) is not unraveled. That is, the silica precipitation reaction does not occur at any place in the aqueous medium, but proceeds selectively on the surface of the crystalline aggregate. If it is a premise satisfying this, the reaction conditions for producing the nanostructure can be arbitrarily set.

  In the step of mixing the aqueous dispersion or hydrogel of the crystalline aggregate with the water glass (B) or an aqueous solution thereof, the pH and concentration of the water glass (B) or the aqueous solution thereof are adjusted, thereby adjusting the crystalline aggregate. It can be maintained in an insoluble state. As described above, it is essential that the pH is 8.5 or more, and it is more preferable to adjust the pH to a range of 9 to 11. The concentration is more preferably in the range of 0.1 to 1.0 mol / L.

  Moreover, in the said mixing process, if the quantity of the silicon of a silica source is made excessive with respect to the ethyleneimine unit in the polymer (A) to be used, a nanostructure can be suitably formed. As an excessive range, it is preferable that silicon is in the range of 10 to 1000 times equivalent to the ethyleneimine unit.

  Further, when the crystal aggregate is formed, the concentration of the polymer (A) in the aqueous medium is 0.1 to 0.1 on the basis of the amount of the linear polyethyleneimine skeleton (a1) contained in the polymer (A). The concentration is preferably 30% by mass, and in order to most effectively control the structure of the composite nanostructure, the concentration is desirably 0.5 to 10% by mass.

  The time for the precipitation reaction of silica (b1) varies from several minutes to several tens of hours. Basically, it may be 10 minutes to 10 hours, and the reaction time is set to 30 minutes to 5 hours in order to increase the reaction efficiency. It is more preferable. Further, the temperature at the time of the precipitation reaction can be preferably set as long as it is not higher than the melting point of the crystalline aggregate, but it is basically desirable to carry out the reaction at a temperature not higher than 70 ° C.

  The polymer / silica composite nanostructure obtained by the present invention is greatly characterized by having various shapes, but the shape is an enlarged copy of the shape of the crystalline aggregate. Accordingly, before the silica (b1) is precipitated, the shape of the nanostructure obtained by growing the crystal of the polymer (A) in an aqueous medium and adjusting the shape of the crystalline aggregate can be controlled.

  The shape of the resulting polymer / silica composite nanostructure can be adjusted to various three-dimensional shapes macroscopically. The size of these composites can be as small as several μm to several mm, but the shape of this size is related to the association of fibrous or lamellar composites with a thickness of 20 to 50 nm, which are regarded as basic units. It is a three-dimensional shape formed from a spatial arrangement. The fibrous or lamellar composite having a thickness of 20 to 50 nm serving as the basic unit includes a crystalline aggregate having a size of several nanometers.

  As described above, the shape of the polymer (A) includes the geometric structure, the molecular weight, the non-ethyleneimine moiety that can be introduced into the primary structure, the concentration of the polymer (A), the crystallization temperature, and the polymer crystal formation described later. It can be adjusted according to various conditions such as the addition of metal ions.

  For example, as a polymer (A) having a linear polyethyleneimine skeleton (a1), a linear polyethyleneimine having a polymerization degree of 300 or more is used and heated to 80 ° C. or higher to obtain a completely transparent solution. The temperature of the solution is naturally lowered to room temperature to obtain an aqueous dispersion of crystalline aggregates. Thereafter, an aqueous solution of water glass (B) adjusted in pH is added to the dispersion, and a silica (b1) precipitation reaction is allowed to proceed, whereby a nanofiber sponge-like structure is obtained.

  When a star-shaped polymer (A) having 4 to 6 polyethyleneimine arms bonded to a benzene ring core is used as the polymer (A) having a linear polyethyleneimine skeleton (a1), the same operation as above Thus, a fan-shaped nanostructure can be obtained.

  Furthermore, by using a crosslinked hydrogel in which the above-described crystalline aggregate is crosslinked by a chemical bond, the macro shape of the composite nanostructure can be controlled, and the structure can be formed into various shapes. The shape and size can be made the same as the size and shape of the container used at the time of adjusting the crosslinked hydrogel, and can be adjusted to any shape such as a disk shape, a column shape, a plate shape, and a spherical shape. Further, the crosslinked hydrogel can be cut or scraped to be formed into a desired shape. By immersing the crosslinked hydrogel thus formed in an aqueous solution of water glass (B), which is a silica source, a molded body composed of a polymer / silica composite nanostructure can be easily obtained. At this time, the time for immersing in the aqueous solution of water glass (B) varies from 1 hour to 1 week depending on the concentration of the aqueous solution of water glass (B) used and the pH of the aqueous solution. 1 to 48 hours is preferable.

  The polymer / silica composite nanostructure obtained in the present invention is composed of a crystalline aggregate comprising polymer (A) and silica (b1), and the content of silica (b1) in the composite nanostructure is determined by the reaction. Although it can be adjusted according to conditions and the like, a material in the range of 30 to 90% by mass of the whole nanostructure can be obtained. The content of the silica (b1) can be increased by increasing the concentration of the polymer (A) used or increasing the reaction time.

  Further, when the crystalline aggregate is formed in the aqueous medium using the polymer (A), the metal ion (c1) is previously present in the aqueous medium, whereby the polymer (A) Since the linear polyethyleneimine skeleton (a1) and the metal ion (c1) form a complex, an aqueous dispersion of a crystalline aggregate containing the metal ion (c1) can be obtained. A polymer / metal ion / silica composite nanostructure can be obtained by conducting a precipitation reaction of silica (b1) using this dispersion in the same manner as described above.

  When adjusting the mixed liquid of the polymer (A) and the metal ion (c1), the molar ratio of the ethyleneimine unit and the metal ion (c1) in the polymer (A) is arbitrary within the range of 1/1 to 100/1. By adjusting this molar ratio, it is possible to adjust the respective contents in the resulting polymer / metal ion / silica composite nanostructure.

  The metal species of the metal ion (c1) is not particularly limited, and examples thereof include transition metals such as Na, Li, K, and Cs such as alkali metals, Ca and Mg as alkaline earth metals, and Fe and Mn as transition metals. , Co, Cr, Cu, Ru, Rh, V, Pd, Mo, Ti, Zr, Eu, Gd, Zn, Cd, and the like, semimetals such as Al, Ga, Sn, In, and Pb can be suitably used. .

  The metal ion (c1) in the polymer / metal ion / silica composite nanostructure obtained above was reduced by adding a reducing agent (D), and nanometer-order metal nanoparticles (c2) were included. It can also be a polymer / metal nanoparticle / silica composite nanostructure.

  The reducing agent (D) that can be used for reducing the metal ion (c1) in the composite nanostructure to the metal nanoparticle (c2) is preferably a low molecular weight reducing agent, such as ascorbine. Examples include acid, sodium citrate, sodium borohydride, ammonium borohydride, hydrogen, hydrazine, and aldehyde.

  The aqueous solution or alcohol solution of the reducing agent (D) and the polymer / metal ion / silica composite nanostructure are mixed, and the mixture is stirred at room temperature to 60 ° C. for 0.5 to 24 hours. Metal ions (c1) can be easily reduced to metal nanoparticles (c2).

  Further, without using a reducing agent, the polymer / silica composite nanostructure is mixed with a solution containing one or more metal ions (c1 ′) selected from the group consisting of gold, silver, and platinum, A polymer / metal nanoparticle / silica composite nanostructure can also be obtained by the reducing action and spontaneous reduction of the linear polyethyleneimine skeleton (a1) in the polymer (A). Examples of gold, silver, and platinum ions include aqueous solutions of chloroauric acid, sodium chloroaurate, silver nitrate, chloroplatinic acid, and sodium chloroplatinate, and these aqueous solutions and polymer / silica composite nanostructures are mixed. Then, the polymer / metal nanoparticle / silica composite nanostructure containing each metal nanoparticle (c2 ′) can be obtained by stirring it at room temperature to 60 ° C. or less. At this time, the metal ion (c1 ′) and the metal nanoparticle (c2 ′) coexist in the middle of the reduction of the metal ion (c1 ′) and the metal nanoparticle (c2 ′). The / metals / silica composite nanostructure includes this coexisting state.

[Silica-based inorganic structure]
Silica from which the polymer has been removed by heating and baking the polymer / silica composite nanostructure, polymer / metal ion / silica composite nanostructure, and polymer / metal nanoparticle / silica composite nanostructure obtained above. A structure, a metal oxide / silica composite, and a metal nanoparticle / silica composite (in the present invention, these are collectively referred to as a silica-based inorganic structure) can be obtained.

  When performing the firing, the powder of the composite nanostructure described above is left in an electric furnace, the furnace temperature is raised to 500 ° C., maintained at that temperature for 1 to 3 hours, and then the temperature is naturally raised to room temperature. A method of lowering to a lower limit is preferable. By this operation, a silica-based inorganic structure from which the polymer (A) has been removed can be easily obtained. The resulting structure is a structure in which only the polymer (A) is removed from the nanostructures used as raw materials, respectively, from a 20-50 nm thick fibrous or lamellar spatial arrangement seen as a basic unit. The formed three-dimensional shape has a high specific surface area.

  EXAMPLES Hereinafter, although a synthesis example and an Example demonstrate this invention further more concretely, this invention is not limited to these. Unless otherwise specified, “%” represents “mass%”.

[Analysis of nanostructures by X-ray diffraction]
The isolated and dried nanostructure is placed on a measurement sample holder, which is set on a wide-angle X-ray diffractometer “Rint-Ultma” manufactured by Rigaku Co., Ltd., Cu / Kα ray, 40 kV / 30 mA, scan speed 1.0 °. The measurement was performed under the conditions of / min and scanning range of 10 to 40 °.

[Thermogravimetric analysis of nanostructures by TG-DTA (differential differential thermal balance)]
The isolated and dried nanostructure is weighed with a measurement patch, and is set in “TG-DTA 6300” manufactured by SII Nanotechnology Co., Ltd., and the temperature rise rate is 10 ° C./min. Measurements were made at

[Elemental analysis of nanostructures by X-ray fluorescence analysis]
Elemental composition analysis was performed by X-ray fluorescence analysis manufactured by Rigaku Corporation.

[Silicon analysis of nanostructures by solid-state ²⁹ Si-NMR]
The nanostructure powder was measured by the CP / MAS method using NMR “JNM-ECA600” manufactured by JEOL Ltd. Polydimethylsilane (-33.8 ppm) was used as an external standard for the measurement.

[Shape analysis of nanostructures by scanning electron microscope]
The isolated and dried nanostructure was placed on a glass slide and observed with a surface observation apparatus VE-9800 manufactured by Keyence.

[Observation of nanostructures by transmission electron microscope]
The isolated and dried nanostructure was placed on a carbon-deposited copper grid and observed with a transmission electron microscope “JEM-2200FS” manufactured by JEOL Ltd.

Synthesis example 1
<Synthesis of linear polyethyleneimine (L-PEI)>
5 g of commercially available polyethyloxazoline (number average molecular weight 500,000, average polymerization degree 5,000, manufactured by Aldrich) was dissolved in 20 mL of 5 mol / L hydrochloric acid. The solution was heated to 90 ° C. in an oil bath and stirred at that temperature for 10 hours. Acetone 50 mL was added to the reaction solution to completely precipitate the polymer, which was filtered and washed three times with methanol to obtain a white polyethyleneimine powder. When the obtained powder was identified by ¹ H-NMR (heavy water), peaks 1.2 ppm (CH ₃ ) and 2.3 ppm (CH ₂ ) derived from the side chain ethyl group of polyethyloxazoline completely disappeared. It was confirmed that That is, it was shown that polyethyloxazoline was completely hydrolyzed and converted to polyethyleneimine.

  The powder was dissolved in 5 mL of distilled water, and 50 mL of 15% aqueous ammonia was added dropwise to the solution while stirring. The mixture was allowed to stand overnight, and then the precipitated crystal powder was filtered, and the crystal powder was washed three times with cold water. The crystal powder after washing was dried in a desiccator at room temperature (25 ° C.) to obtain linear polyethyleneimine (L-PEI). The yield was 4.2 g (including crystal water). In polyethyleneimine obtained by hydrolysis of polyoxazoline, only the side chain reacts and the main chain does not change. Therefore, the polymerization degree of L-PEI is the same as 5,000 before hydrolysis.

Synthesis example 2
<Synthesis of star-shaped polyethyleneimine (B-PEI) centered on benzene ring>
Jin, J .; Mater. Chem. , 13, 672-675 (2003), a star-shaped polymethyloxazoline in which six polymethyloxazoline arms were bonded to the center of the benzene ring as a precursor polymer was synthesized as follows.

Put 0.021 g (0.033 mmol) of hexakis (bromomethyl) benzene as a polymerization initiator in a test tube set with a magnetic stirrer, attach a three-way cock to the test tube, and then put it in a vacuum state. Was replaced with nitrogen. Under a nitrogen stream, 2.0 ml (24 mmol) of 2-methyl-2-oxazoline and 4.0 ml of N, N-dimethylacetamide were sequentially added from the inlet of the three-way cock using a syringe. When the test tube was heated to 60 ° C. on an oil bath and kept for 30 minutes, the mixture became transparent. The transparent mixture was further heated to 100 ° C. and stirred at that temperature for 20 hours to obtain a precursor polymer. From the ¹ H-NMR measurement of this mixture, the monomer conversion was 98 mol% and the yield was 1.8 g. When the average degree of polymerization of the polymer was estimated based on this conversion, the average degree of polymerization of each arm was 115. Moreover, in the molecular weight measurement by GPC, the mass average molecular weight of the polymer was 22,700, and the molecular weight distribution was 1.6.

Using this precursor polymer, polymethyloxazoline was hydrolyzed in the same manner as in Synthesis Example 1 to obtain star-shaped polyethyleneimine B-PEI in which 6 polyethyleneimines were bonded to the benzene ring core. ^{As a result of 1} H-NMR (TMS external standard, heavy water) measurement, it was confirmed that the peak of 1.98 ppm derived from the side chain methyl of the precursor polymer before hydrolysis completely disappeared.

  The powder was dissolved in 5 mL of distilled water, and 50 mL of 15% aqueous ammonia was added dropwise to the solution while stirring. The mixture was allowed to stand overnight, and then the precipitated crystal powder was filtered, and the crystal powder was washed three times with cold water. The washed crystal powder was dried in a desiccator at room temperature (25 ° C.) to obtain star-shaped polyethyleneimine (B-PEI) in which six polyethyleneimines were bonded to the benzene ring core. The yield was 1.3 g (including crystal water).

Synthesis example 3
<Synthesis of block copolymer PEG-b-PEI>
A block copolymer of PEG and polyoxazoline, which is a precursor block polymer, uses a polymer in which tosylate is bonded to one end of polyethylene glycol (PEG) having a number average molecular weight of 4,000 as a polymerization initiator (PEG-I). The synthesis was performed as follows.

PEG-I 1.5 g (0.033 mmol) as a polymerization initiator is introduced into a test tube set with a magnetic stirrer, a three-way cock is attached to the test tube port, and then the state is evacuated before nitrogen. Replacement was performed. Under a nitrogen stream, 6.0 ml (72 mmol) of 2-methyl-2-oxazoline and 20.0 ml of N, N-dimethylacetamide were sequentially added from the inlet of the three-way cock using a syringe. The test tube was heated to 100 ° C. on an oil bath and stirred at that temperature for 24 hours to obtain a precursor block polymer. From the ¹ H-NMR measurement of the obtained liquid mixture, it was found that the monomer conversion was 100 mol%.

The yield of the precursor block polymer after purification was 93%. Further, in the ¹ H-NMR measurement, each integration ratio based on the polymer terminal tosyl group was determined. The degree of polymerization of PEG was 45 and the degree of polymerization of polyoxazoline was 93. That is, the average degree of polymerization of the block polymer was 138. Moreover, in the molecular weight measurement by GPC, the number average molecular weight of the polymer was 12,000, and the molecular weight distribution was 1.27.

Using this precursor block polymer, the polyoxazoline block was hydrolyzed in the same manner as in Synthesis Example 1 to obtain a block copolymer (PEG-b-PEI) in which polyethyleneimine was bonded to PEG. ^{As a result of 1} H-NMR (TMS external standard, heavy water) measurement, the 1.98 ppm peak derived from the side chain methyl of the precursor polymer before hydrolysis completely disappeared.

Examples 1-1 to 1-3 and Comparative Examples 1 to 3
<Production of nanostructures from linear polyethyleneimine>
The L-PEI powder obtained in Synthesis Example 1 was used and dispersed in distilled water, and then heated to 90 ° C. in an oil bath to obtain a completely transparent aqueous solution. The aqueous solution was allowed to stand at room temperature and naturally cooled to room temperature to obtain 1% of an opaque crystalline aggregate. On the other hand, water glass No. 3 (manufactured by Kishida Chemical Co., Ltd., pH = 11.3) was used, and the pH value was 9.4 (Example 1-1), 9.8 (Example 1-2), 10 (implemented) A 0.2 mol / L water glass aqueous solution of Example 1-3) and pH 2 (Comparative Example 1), 4 (Comparative Example 2), and 6 (Comparative Example 3) was prepared. For adjusting the pH value of the water glass aqueous solution, 1 mol / L hydrochloric acid and 25% aqueous ammonia were used.

  10 g of the aqueous dispersion of the crystalline aggregate having a concentration of 1% obtained above and 20 ml of a 0.2 mol / L water glass aqueous solution were mixed, stirred for 5 minutes, and then allowed to stand at 50 ° C. Precipitation reaction was performed for a time, and a white precipitate was obtained. The supernatant in the reaction solution was removed, and the precipitate was washed with distilled water and then repeatedly washed three times by centrifugation. The obtained solid was dried at room temperature and then dried in a vacuum dryer at 60 ° C. for 12 hours to obtain nanostructures (1-1) to (1-3) and Comparative Examples 1 to 3. The yield of the obtained powder is shown in Table 1.

  The results of scanning micrograph (SEM) observation of the obtained nanostructure are shown in FIGS. The structures (1) to (3) obtained from the aqueous water glass solution having a pH value of 2 to 6 were basically bulky lumps, but obtained from the aqueous water glass solution having a pH value adjusted to 9.4 to 10. Nanostructures (1-1) to (1-3) were sponges having a fiber network structure.

  A transmission electron microscope (TEM) photograph of the nanostructure (1-3) obtained in Example 1-3 is shown in FIG. In very thin lamellar silica (left), a constant shadow (right) was observed. The shade is presumed to be a contrast due to a portion where the polymer and silica are combined at a level of several nanometers.

From the solid ²⁹ Si-NMR (CP / MAS) measurement of the nanostructure (1-3) obtained in Example 1-3, a Q4 signal indicating a silica bond structure appears at −110 ppm, and a Q3 signal appears at −101 ppm. The integration ratio of Q4 / Q3 was 1.00 / 0.68 (see FIG. 8). No Q2 binding signal appeared. This strongly suggests that the silica forming the fibrous network has a high degree of Si (0Si) ₄ bonding units.

  Furthermore, as a result of elemental analysis of the nanostructure (1-3) obtained in Example 1-3, Si: 30%, C: 15%, H: 4.1%, N: 8.2%, Na : 0.8%. This suggested that the nanostructure (1-3) was complexed with linear polyethyleneimine other than silicon, and its content was about 27%. That is, the obtained nanostructure is a structure in which silica and a polymer are combined.

Example 2
The nanostructure (1-3) obtained in Example 1-3 was put in a 0.1 g alumina crucible, heated to 500 ° C. in an electric furnace, and fired at that temperature for 1 hour. The yield was 0.07g. Was fired at 500 ° C. for 1 hour to obtain a silica-based inorganic structure. As a result of SEM observation, there was no change in the fiber structure (see FIG. 9), and in ²⁹ Si-NMR (CP / MAS), the integration ratio of Q4 / Q3 was 1.00 / 0.52 (see FIG. 10). . That is, the Q4 structural component tended to increase slightly.

Furthermore, as a result of measuring the specific surface area of the structure before and after thermal firing using Flow Sorb II 2300 (Micromeritics) in an N ₂ / He mixed gas (3/7 volume ratio) adsorption-desorption experiment method, it was 149 m before firing. ^{From 2} / g to 315 m ² / g after firing, there was a large increase of about 2 times. It was suggested that polymer removal by calcination increases the surface area.

Example 3-1
<Nanostructures containing gold nanoparticles>
0.05 g of the nanostructure (1-3) obtained in Example 1-3 was added to 2 mL of a 0.1 mol / L NaAuCl ₄ solution, stirred for 5 minutes at room temperature (25 ° C.), and then 25 Let sit for a minute. The obtained solid was washed with distilled water and then dried at room temperature. From the XRD measurement of the powder thus obtained, scattering peaks (2θ) indicating the presence of gold crystals were confirmed at 38.1 °, 44.4 °, 64.5 °, and 77.6 °. From TEM observation, it was observed that gold nanoparticles having a size of 2 to 3 nm were confined in silica (FIG. 11). This was very different from the image of FIG. 7 in which no metal nanoparticles were included.

Example 3-2
<Nanostructures containing platinum nanoparticles>
0.05 g of the nanostructure (1-3) obtained in Example 1-3 was added to 2 mL of a 0.1 mol / L Na ₂ PtCl ₄ solution, stirred at room temperature for 5 minutes, and then allowed to stand for 25 minutes. I let you. The obtained solid was washed with distilled water and then dried at room temperature. From the XRD measurement of the powder thus obtained, scattering peaks (2θ) indicating the presence of platinum crystals were observed at 40.0 °, 46.4 °, and 67.7 °. From TEM observation, it was observed that platinum nanoparticles having a size of 2 to 3 nm were confined in silica (FIG. 12). This was very different from the image of FIG. 7 in which no metal nanoparticles were included.

Example 4
<Nanostructures from polyethyleneimine with benzene ring center>
Using B-PEI synthesized in Synthesis Example 2, a dispersion of a crystalline aggregate of 2% polymer was prepared in the same manner as in Example 1. To 10 g of this dispersion, 20 mL of a 0.2 mol / L water glass aqueous solution having a pH value of 9.6 was added and allowed to stand at room temperature (25 ° C.) for 1 hour. The supernatant was taken out and the solid was washed with distilled water and then repeatedly washed three times with a centrifuge. The obtained solid was dried at room temperature and then dried in a vacuum dryer at 60 ° C. for 12 hours to obtain a white nanostructure (4). The yield was 0.53g.

  The SEM observation photograph and TEM observation photograph of the nanostructure (4) obtained above are shown in FIG. 13 and FIG. The image of a fan-shaped composite nanostructure appeared clearly. In addition, in the XRD measurement of the nanostructure (4), scattering peaks derived from polymer crystals were confirmed at 20.3 °, 27.3 °, and 28.2 °.

Examples 5-1 to 5-4
<Nanostructures from block copolymers>
Using the block copolymer (PEG-b-PEI) obtained in Synthesis Example 3 and containing 3 kinds of 2% polymer solution containing sodium nitrate, copper nitrate and aluminum nitrate and metal ions under heating at 90 ° C No polymer solution was prepared. Table 2 shows the molar ratio between each metal ion in the solution and the ethyleneimine unit (EI) in the polymer. These solutions were allowed to stand at room temperature for 6 hours to obtain crystalline aggregates. 20 mL of a 0.2 mol / L water glass aqueous solution having a pH value of 9.6 was added to 10 g of the dispersion of each crystalline aggregate, and the mixture was stirred for 5 minutes and allowed to stand at room temperature for 1 hour. The precipitated solid was washed with distilled water and further washed three times with a centrifuge. The obtained solid was dried at room temperature and then dried at 60 ° C. for 12 hours in a vacuum dryer to obtain polymer / metal ion / silica composite nanostructures (5-1) to (5-4). Yields are shown in Table 2.

  SEM observation photographs of the nanostructures (5-1) to (5-4) obtained in Examples 5-1 to 5-4 are shown in FIGS. It was suggested that a large change occurred in the shape of the resulting structure due to the presence of metal ions.

Example 6
A sample of 0.3 g of the nanostructure (5-3) containing copper ions of Example 5-3 was mixed with 10 mL of a 0.1 mol / L aqueous solution of ammonium borohydride, and 40 ° C. under a nitrogen atmosphere. For 1 hour. The resultant was washed with ethanol under a nitrogen atmosphere and dried under a nitrogen atmosphere. The powder thus obtained completely disappeared from the original blue color and showed a light copper color. From the powder XRD measurement, scattering peaks 2θ (°) indicating the presence of zerovalent copper were observed as 43.4, 50.5, and 74.1, confirming that the reduction reaction occurred.

2 is a scanning electron micrograph of the structure (1) obtained in Comparative Example 1. 4 is a scanning electron micrograph of the structure (2) obtained in Comparative Example 2. 4 is a scanning electron micrograph of the structure (3) obtained in Comparative Example 3. It is a scanning electron micrograph of the nanostructure (1-1) obtained in Example 1-1. It is a scanning electron micrograph of the nanostructure (1-2) obtained in Example 1-2. It is a scanning electron micrograph of the nanostructure (1-3) obtained in Example 1-3. It is a transmission electron micrograph of the nanostructure (1-3) obtained in Example 1-3. The right figure is a high resolution image of the circular part of the left figure. It is a solid-state ²⁹ Si-NMR (CP / MAS) spectrum of the nanostructure (1-3) obtained in Example 1-3. It is a scanning electron micrograph before and behind thermal baking of the nanostructure (1-3) obtained in Example 1-3. It is a solid-state ²⁹ Si-NMR (CP / MAS) spectrum after the heat calcination of the nanostructure (1-3) obtained in Example 1-3. It is a transmission electron micrograph of the nanostructure (3-1) containing the gold nanoparticle obtained in Example 3-1. The right figure is an enlarged image of the circular part of the left figure. Black spots are photographs of gold nanoparticles of about 2 nm. It is a transmission electron micrograph of the nanostructure (3-2) containing the platinum nanoparticles obtained in Example 3-2. The right figure is an enlarged image of the circular part of the left figure. Black spots are photographs of platinum nanoparticles of about 2 nm. 4 is a scanning electron micrograph of the nanostructure (4) obtained in Example 4. 4 is a transmission electron micrograph of the nanostructure (4) obtained in Example 4. FIG. The right figure is an enlarged view of the left figure. It is a scanning electron micrograph of the nanostructure (5-1) obtained in Example 5-1. The right figure is an enlarged view of the left figure. It is a scanning electron micrograph of the nanostructure (5-2) obtained in Example 5-2. The right figure is an enlarged view of the left figure. It is a scanning electron micrograph of the nanostructure (5-3) obtained in Example 5-3. The right figure is an enlarged view of the left figure. It is a scanning electron micrograph of the nanostructure (5-4) obtained in Example 5-4. The right figure is an enlarged view of the left figure.

Claims (5)

A polymer (A) having a linear polyethyleneimine skeleton (a1) is made into a crystalline aggregate in an aqueous medium, and this is mixed with water glass (B) whose pH is adjusted to 8.5 or higher to obtain silica (b1 ) Is precipitated. A method for producing a polymer / silica composite nanostructure. The polymer (A) having a linear polyethyleneimine skeleton (a1) and the metal ion (c1) are mixed in an aqueous medium to form a crystalline aggregate containing the metal ion (c1), and the pH is adjusted to 8. A method for producing a polymer / metal ion / silica composite nanostructure, wherein silica (b1) is precipitated by mixing water glass (B) adjusted to 5 or more. The polymer (A) having a linear polyethyleneimine skeleton (a1) and the metal ion (c1) are mixed in an aqueous medium to form a crystalline aggregate containing the metal ion (c1), and the pH is adjusted to 8. Mixing with water glass (B) adjusted to 5 or more to precipitate silica (b1), and further reducing metal ions (c1) with a reducing agent (D) to form metal nanoparticles (c2). A method for producing a polymer / metal nanoparticle / silica composite nanostructure. By mixing the polymer / silica composite nanostructure obtained in claim 1 with an aqueous solution containing at least one metal ion (c1 ′) selected from the group consisting of gold, silver and platinum, the metal ion ( Production of polymer / metal nanoparticle / silica composite nanostructure characterized in that c1 ′) is concentrated to the polymer (A) in the nanostructure and converted into metal nanoparticles (c2 ′) by spontaneous reduction. Method. A method for producing a silica-based inorganic structure, wherein the nanostructure obtained by the method according to any one of claims 1 to 4 is further thermally calcined.