JP5038636B2 - Titanium oxide / polymer composite and method for producing the same - Google Patents

Description

  The present invention relates to a titanium oxide / polymer composite composed of titanium oxide useful as a photocatalyst or a fuel cell catalyst and a polymer having a linear polyethyleneimine skeleton, and a process for producing the same. The present invention relates to a titanium oxide / polymer composite characterized by being a network of spherical particles, and a method for producing the composite having the structure under mild conditions of 50 ° C. or lower.

  Among advanced materials, titanium oxide is attracting more and more attention because it exhibits different physical properties from conventional white pigments and high refractive index materials (see Non-Patent Document 1, for example). For example, in the photocatalyst or dye-sensitized catalyst function, titanium oxide is an outstanding catalyst material, and is highly expected in the field of application to next-generation photocatalytic devices and solar cells. In addition, even in fuel cells that have attracted a great deal of attention in terms of energy problems, research and development of electrode layers in which platinum nanoparticles are embedded in titanium oxide have attracted attention. Hydrogen production is required for the practical use of fuel cells, but titanium oxide / platinum composites are also promising candidates for hydrogen production catalysts.

  In these applications of titanium oxide, it is impossible to demonstrate the function of titanium oxide alone, and it is necessary to combine it with other materials. In addition, control of the shape of titanium oxide in the nano-dimensions is a prerequisite for application development. It is a condition. For example, for use as a photocatalyst, it is required to convert the ultraviolet absorption of titanium oxide itself into visible light absorption. Therefore, in many studies, nitrogen doping, which is also called an impurity in titanium oxide, doping of organic components, doping of metal nanoparticles, and the like have been studied. In order to perform such doping in titanium oxide, conventionally, a complicated process is required, and it is an important issue to design a structure of titanium oxide so that various dopings can be easily performed in the titanium oxide manufacturing stage. It is. In addition, in the application of titanium oxide in fuel cells and solar cells, it is required that the titanium oxide is a network having nanodomains. In many cases, the titanium oxide nanoparticles are fired to form a network by fusing the particles. The method of configuring is taken. Finishing the resulting titanium oxide into a fiber network or a network of spherical particles at the titanium oxide production stage is also the key to the application of titanium oxide.

  On the other hand, many techniques relating to titanium oxide nanofibers, nanotubes, or nanoparticles are known (for example, see Non-Patent Documents 2 to 4). However, titanium oxide / polymer composites containing a polymer having a function capable of easily incorporating a metal or an organic substance into them are not known. That is, the development of titanium oxide having a function of spontaneously incorporating functional substances such as metals and pigments is a problem to be solved that is essential for industrial use of titanium oxide.

A. L. Linsebiger et al. Chem. Rev. 1995, 95, 735 S. Kobayashi et al. Chem. Mater. 2000, Vol. 12, p. 1523 Adachi et al, Langmuir, 1999, 15, 7097 D. Pan et al. Adv. Mater. 2005, Vol. 17, 1991

  The problem to be solved by the present invention is a titanium oxide / polymer composite in which a polymer capable of incorporating a functional substance such as a metal or an organic substance and titanium oxide are combined with a layered structure of nanometer order. Another object of the present invention is to provide a simple and short-time method for producing the complex.

  As a result of intensive studies to solve the above problems, the present inventors have found that a polymer having a linear polyethyleneimine skeleton and titanium oxide can form a composite having a nanolayer structure, and that linear polyethylene A titanium oxide / polymer composite is produced under mild conditions by growing a polymer having an imine skeleton into a crystalline aggregate in an aqueous solvent and then bringing the crystalline aggregate into contact with a water-soluble titanium compound. The present invention has been completed by finding out what can be done.

  That is, the present invention provides a titanium oxide / polymer composite characterized in that the polymer (A) having a linear polyethyleneimine skeleton and the titanium oxide (B) have a nanolayer structure.

Furthermore, the present invention is a method for producing a composite in which a polymer (A) having a linear polyethyleneimine skeleton and a titanium oxide (B) have a nanolayer structure,
(I) a step of growing a polymer (A) having a linear polyethyleneimine skeleton into a crystalline aggregate in an aqueous solvent;
(Ii) contacting the crystalline aggregate with the water-soluble titanium compound (C) to form titanium oxide (B) and combine it with the polymer (A);
The present invention also provides a method for producing a titanium oxide / polymer composite characterized by comprising:

  The composite of a polymer having a linear polyethyleneimine skeleton of the present invention and titanium oxide has an interlayer distance of several nanometers in the composite structure, and has a fiber or a spherical particle as a basic unit in shape. A three-dimensional network structure is formed. In such a complex, titanium oxide forms anatase-type nanocrystal domains, and the polymer exists in a state of being sandwiched between the titanium oxide nanodomains. Such a structure / morphology can be easily controlled through a crystalline aggregate of a polymer having a linear polyethyleneimine skeleton.

  Further, in the formation of the composite of the polymer having a linear polyethyleneimine skeleton of the present invention and titanium oxide, a functional substance such as a fluorescent substance can be contained in the polymer. In addition, a function derived from the functional substance can be expressed in the complex.

  In addition, in the composite of the polymer having a linear polyethyleneimine skeleton of the present invention and titanium oxide, the polymer can contain a metal ion, and functions as a composite in which an organometallic complex is combined. be able to.

  Furthermore, since the composite of the present invention contains a polymer having a linear polyethyleneimine skeleton, a complexing agent for forming a metal complex, a reducing agent for reducing a noble metal, formation of an ion complex with an organic acidic substance, etc. Because of its functions, it is widely used in industrial fields, and is developed for advanced materials such as biotechnology and nanomaterials. It can also be used in many areas such as drugs, antivirals, and cosmetics.

  Furthermore, since the polymer in the complex of the present invention can exhibit the intrinsic function as polyethyleneimine, metal nanoparticles, metal complexes, organic acid dyes, etc. can be easily introduced into the complex. Is possible. That is, the titanium oxide / polymer composite of the present invention can be used as a photocatalyst, a photosensitized solar cell member, a hydrogen generation catalyst, or a hydrogen source fuel cell member.

  In addition, the titanium oxide / polymer composite of the present invention can be easily removed by sintering while maintaining its shape. Therefore, since it can be converted into a pure titanium oxide anatase or rutile crystal having a network shape of fibers or spherical particles, it can be applied to applications such as catalysts, electronic materials, and nanofilters.

  The composite of the present invention is a composite in which a polymer (A) having a linear polyethyleneimine skeleton and titanium oxide (A) are combined while having a constant nanometer order interlayer distance. It has a network structure based on the shape of a spherical or spherical particle.

  Many inorganic oxides in biological systems are complex and precise patterns in which biopolymers, for example, basic polypeptides, proteins, or polyamine tissues (aggregates) are used as templates and those biopolymers are included. Form. The present invention is based on the knowledge that a titanium oxide / polymer complex can be obtained by imitating such a process of living organisms, using a functional polymer aggregate as a template, and generating titanium oxide in the presence thereof. Is.

  In the present invention, a polymer (A) having a linear polyethyleneimine skeleton is used as the functional polymer aggregate, and the polymer (A) easily forms a crystalline aggregate in an aqueous solvent. This is applied to produce titanium oxide via the crystalline aggregate. The titanium oxide (B) obtained in this way is combined with the polymer (A) and has a certain shape, which is characterized by a network characterized by fibers or spherical particles. Examples thereof include a network, and these can be easily controlled by changing the conditions for forming the crystalline aggregate of the polymer (A).

[Polymer having linear polyethyleneimine skeleton (A)]
The linear polyethyleneimine skeleton as used in the present invention refers to a polymer skeleton having an ethyleneimine unit of a secondary amine as a main structural unit. In the skeleton, structural units other than the ethyleneimine unit may exist, but in order to form a crystalline association efficiently in an aqueous solvent, a constant chain length of the polymer chain is continuous. An ethyleneimine unit is preferred. The length of the linear polyethyleneimine skeleton is not particularly limited as long as the polymer (A) having the skeleton can form a crystalline aggregate, but the crystalline aggregate can be suitably formed. Therefore, the number of repeating units of the ethyleneimine unit in the skeleton is preferably in the range of 10 to 10,000, particularly preferably in the range of 20 to 8,000.

  The polymer (A) having a linear polyethyleneimine skeleton used in the present invention has a linear polyethyleneimine skeleton in its structure and can give a crystalline aggregate in an aqueous solvent. Any shape may be used, and the shape may be linear, star or comb.

  Further, these linear, star-like or comb-like polymers may be composed only of a linear polyethyleneimine skeleton, or may be a block composed of a linear polyethyleneimine skeleton [hereinafter abbreviated as polyethyleneimine block (a1). To do. ] And another polymer block (a2). Examples of the other polymer block (a2) include water-soluble polymer blocks such as polyethylene glycol, polypropionylethyleneimine, and polyacrylamide, or polystyrene, polyoxazolines such as polyphenyloxazoline, polyoctyloxazoline, polydodecyloxazoline, Mention may be made of hydrophobic polymer blocks such as polyacrylates such as polymethyl methacrylate and polybutyl methacrylate. By using a block copolymer with these other polymer blocks (a2), the shape and characteristics of the crystalline aggregate of the polymer (A) can be adjusted.

  When the polymer (A) having a linear polyethyleneimine skeleton is a block copolymer, the proportion of the polyethyleneimine block (a1) in the polymer (A) is particularly within the range that can form a crystalline aggregate. Although not limited, the proportion of the polyethyleneimine block (a1) in the polymer (A) is usually 25 to 100 mol%, preferably 40 mol% or more, from the viewpoint that the crystalline aggregate can be suitably formed. , 50 mol% or more is particularly preferable.

  The production method of the polymer (A) having a linear polyethyleneimine skeleton is not particularly limited. However, from the viewpoint of excellent industrial production method, a linear chain composed of polyoxazolines as precursors thereof is used. It is preferable to use a method of hydrolyzing a polymer having a skeleton (hereinafter abbreviated as a precursor polymer) under acidic conditions or alkaline conditions. That is, the shape of the polymer (A) having a linear polyethyleneimine skeleton such as a linear shape, a star shape, or a comb shape can be easily designed by controlling the shape of the precursor polymer. Moreover, the polymerization degree and terminal structure of the polymer (A) can be easily adjusted by controlling the polymerization degree and terminal functional group of the precursor polymer. Furthermore, when the polymer (A) having a linear polyethyleneimine skeleton is a block copolymer, the precursor polymer is used as a block copolymer, and the linear skeleton composed of polyoxazolines in the precursor polymer is selectively used. It can be obtained by hydrolysis.

  The precursor polymer can be synthesized by using a monomer such as an oxazoline by a cationic polymerization method or a synthesis method such as a macromonomer method, and by appropriately selecting a synthesis method and a polymerization initiator, Precursor polymers having various shapes such as a star shape, a star shape, or a comb shape are obtained.

  Examples of the oxazoline monomers include methyl oxazoline, ethyl oxazoline, methyl vinyl oxazoline, and phenyl oxazoline.

  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 functional groups are preferred because of their high polymerization initiation efficiency, especially those converted to alkyl bromides and toluene sulfonates. 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, and particularly preferably in the range of 10 to 50.

  In addition, when using a dye having a functional group having the ability to initiate cationic ring-opening living polymerization and having a light-emitting function by light, an energy transfer function, an electron transfer function, a porphyrin skeleton, a phthalocyanine skeleton, or a pyrene skeleton Can give a special function derived from the compound used as an initiator to the resulting polymer or composite.

  The linear precursor polymer can be obtained by polymerizing the above oxazoline monomers 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 can be obtained by polymerizing the above oxazoline monomers 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, and tetrabromoethoxyphthalocyanine. A pentavalent or higher valent compound such as hexabromomethylbenzene and tetra (3,5-ditosilylethyloxyphenyl) porphyrin can be used.

  In order to obtain a comb-like precursor polymer, a linear polymer having a polyvalent polymerization initiating group can be used to polymerize monomers of oxazolines from the polymerization initiating group. It can also be obtained by halogenating the hydroxyl group of a polymer having a hydroxyl group in the side chain such as 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. Can do.

  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 composed of the polyoxazolines of the precursor polymer obtained as described above may be carried out under either acidic conditions or alkaline conditions.

  Examples of the hydrolysis reaction under acidic conditions include a method in which a precursor polymer is stirred under heating in an aqueous hydrochloric acid solution, and a hydrochloride of a polymer having a polyethyleneimine chain can be obtained. By treating the obtained hydrochloride with an excess of aqueous ammonium, crystal powder of a polymer having a basic polyethyleneimine chain 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. Moreover, it is preferable that reaction temperature is 70-90 degreeC.

  Examples of the hydrolysis reaction under alkaline conditions include a method using an aqueous sodium hydroxide solution, and a polyoxazoline chain can be converted into a polyethyleneimine chain. After the reaction under alkaline conditions, the reaction solution is washed with a dialysis membrane to remove excess sodium hydroxide and obtain a polymer crystal powder having a polyethyleneimine chain. 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. Moreover, it is preferable that reaction temperature is 70-90 degreeC.

  The amount of acid or alkali used in hydrolysis under acidic or alkaline conditions is usually 1 to 10 equivalents relative to the oxazoline unit in the precursor polymer, improving reaction efficiency and simplifying post-treatment. For the purpose of conversion, it is preferably 2 to 4 equivalents.

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

  When forming a block copolymer of the polyethyleneimine block (a1) and the other polymer block (a2), the precursor polymer is a linear polymer block made of polyoxazolines and another polymer block (a2). And a method of selectively hydrolyzing a linear polymer block composed of polyoxazolines in the precursor polymer.

  When the other polymer block (a2) is a water-soluble polymer block such as poly (N-propionylethyleneimine), poly (N-propionylethyleneimine) is converted to poly (N-formylethyleneimine) or poly ( Compared to (N-acetylethyleneimine), a block copolymer can be formed by utilizing its high solubility in an organic solvent. 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 initiator, and then the resulting living polymer is further polymerized with 2-ethyl-2-oxazoline. Thus, a precursor polymer composed of a poly (N-formylethyleneimine) block or a poly (N-acetylethyleneimine) block and a poly (N-propionylethyleneimine) block can be 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. Thereafter, the poly (N-formylethyleneimine) block or the poly (N-acetylethyleneimine) block is preferentially hydrolyzed by adding an acid or alkali to the aqueous phase of the emulsion, whereby a polyethyleneimine block is obtained. A block copolymer having (a1) and a poly (N-propionylethyleneimine) block can be formed.

  When the valence of the polymerization initiator 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.

[Polymer crystalline aggregate]
The polymer (A) having the above-described linear polyethyleneimine skeleton is such that the linear polyethyleneimine skeleton in the primary structure exhibits crystallinity in water or a mixed solution of water and a water-soluble solvent (that is, an aqueous solvent). To form polymer crystals. The crystal of the polymer (A) exhibits a form accompanying polymer crystal growth in the presence of water, and forms an aggregate. A cross-linked aggregate having chemical cross-linking can also be formed by cross-linking the aggregate with a cross-linking agent.

  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, although branched polyethyleneimine is water-soluble, it does not have crystallinity, so that a crystalline aggregate cannot be formed using branched polyethyleneimine. However, the polymer (A) used in the present invention has a linear polyethyleneimine as a skeleton, and the linear polyethyleneimine is composed only of a secondary amine and is water-soluble in a heated state. In the temperature range below the melting point, it has excellent crystallinity.

  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 a temperature of 50 ° C. or lower.

  The crystal of the polymer (A) having a linear polyethyleneimine skeleton in the present invention is formed by crystal expression of the linear polyethyleneimine skeleton in the same manner as described above, and the polymer shape is linear or star-shaped. Even in the shape of a comb or the like, the polymer (A) crystal can be obtained as long as it has a linear polyethyleneimine skeleton in the primary structure.

  The presence of the polymer crystal can be confirmed by X-ray scattering, that is, the linear polyethyleneimine skeleton in the crystalline aggregate of 20 °, 27 °, and 28 ° in terms of 2θ angle values in a wide angle X-ray diffractometer (WAXS). It can be confirmed by the derived peak value.

  Moreover, although the melting point in the differential scanning calorimeter (DSC) of the polymer crystal in the present invention depends on the primary structure of the polymer (A) having a linear polyethyleneimine skeleton, a peak appears at about 55 to 90 ° C.

  The crystalline aggregate in the present invention has various shapes depending on the geometrical shape of the polymer structure constituting the crystal, the molecular weight, the non-ethyleneimine moiety that can be introduced into the primary structure, and the formation conditions of the polymer crystal. For example, it has a fiber shape, a brush shape, a star shape, or the like.

  The polymer crystalline aggregate is based on a nanometer-order fiber-like polymer crystal (hereinafter, the crystal is abbreviated as a fiber-like nanocrystal), and the fiber-like nanocrystal. By the free ethyleneimine chain existing on the surface, the fiber-like nanocrystals are connected to each other by a physical bond by a hydrogen bond and are arranged in a space, and grow into a three-dimensional shape as described above. These polymer crystals are further physically bonded to form a crosslinked structure, thereby creating a three-dimensional network structure of the polymer crystals. Since these occur in the presence of water, the result is a cream state in which water is included in the three-dimensional network structure.

  The term “three-dimensional network structure” as used herein refers to a network structure in which micro or nano-scale crystals are physically cross-linked by hydrogen bonds of free ethyleneimine chains existing on the crystal surface. Therefore, at a temperature higher than the melting point of the crystal, the crystal is dissolved in water, and the three-dimensional network structure is also dismantled. However, when it returns to room temperature, polymer crystals grow, and physical crosslinks due to hydrogen bonds are formed between the crystals, so that a three-dimensional network structure appears again.

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

  The crystalline aggregate is prepared by first dispersing a polymer (A) having a linear polyethyleneimine skeleton in a certain amount in water and heating the dispersion to thereby polymer (A) having a linear polyethyleneimine skeleton. Is obtained by cooling the heated aqueous solution of the polymer (A) to room temperature. The aggregate is deformed by an external force such as a shearing force, but has an ice cream-like state capable of maintaining a general shape, and can be deformed into various shapes.

  The heating temperature of the polymer dispersion is preferably 100 ° C. or less, and more preferably in the range of 90 to 95 ° C. In addition, the polymer content in the polymer dispersion is not particularly limited as long as the aggregate is obtained, but is preferably in the range of 0.01 to 20% by mass, and is a cream state made of a crystal of a stable shape In order to obtain, the range of 0.1-10 mass% is further more preferable. Thus, in the present invention, when the polymer (A) having a linear polyethyleneimine skeleton is used, a cream-like aggregate can be formed even with a very small polymer concentration.

  The crystal shape in the obtained aggregate can be adjusted by the process of lowering the temperature of the polymer dispersion to room temperature. For example, the polymer dispersion is held at 80 ° C. for 1 hour, then brought to 60 ° C. over 1 hour, and held at that temperature for another 1 hour. Thereafter, the temperature is lowered to 40 ° C. over 1 hour, and then the temperature is naturally lowered to room temperature, whereby a crystalline aggregate in a state in which the water of the dispersion loses fluidity can be obtained. In addition, after the polymer dispersion is cooled at once by freezing water, or a refrigerant liquid of methanol / dry ice or acetone / dry ice below freezing, the state in that state is held in a water bath at room temperature. A crystalline aggregate can be obtained. Furthermore, a crystalline aggregate can be obtained by lowering the temperature of the polymer dispersion to room temperature in a room temperature water bath or room temperature air environment.

  Since the step of lowering the temperature of the polymer dispersion strongly affects the shape of the polymer crystals in the resulting aggregate, the crystalline form of the polymers in the aggregate obtained by the different steps is not the same.

  In general, polyethyleneimine polymers have a strong coordination ability to metal ions, so adding metal ions to the above polymer dispersion creates a coordination bond between the metal ions and the polymer, thereby suppressing polymer crystal growth. It is also possible to do.

  As metal ions, all metals such as alkali metals, alkaline earth metals, and transition metals can be used. The metal ion valence may be a monovalent to tetravalent metal salt, and they can be preferably used even in a complex ion state.

  The amount of the metal ion to be used is preferably 1/20 to 1/200 equivalent relative to the number of moles of ethyleneimine units in the polymer (A) having a linear polyethyleneimine skeleton.

  When metal ions are present, in the process of crystallization from the polymer dispersion, it is preferable that 5-24 hours elapse to complete crystal growth. Thereby, a stable crystalline aggregate can be obtained.

  The aggregate obtained as described above is in an opaque cream state that is physically cross-linked by hydrogen bonding between polymer crystals. Once formed, the polymer crystals remain insoluble at room temperature, but when heated, the polymer crystals dissociate and the aggregates change to a sol state. Therefore, the cream-like aggregate of the present invention can be reversibly changed from sol to gel or from gel to sol by heat treatment.

  The aggregate referred to in the present invention contains at least water in the three-dimensional network structure, but it can also be made into an aggregate containing the solvent by adding a water-soluble organic solvent during the preparation of the aggregate. is there. Examples of the water-soluble organic solvent that can be used include methanol, ethanol, tetrahydrofuran, acetone, dimethylacetamide, dimethylsulfone oxide, dioxirane, and pyrrolidone.

  The content of the water-soluble organic solvent is preferably in the range of 0.1 to 5 times, more preferably in the range of 1 to 3 times the volume of water.

  By containing the water-soluble organic solvent, the form of the polymer crystal can be changed, and a crystal having a form different from that of a simple aqueous system can be provided. For example, even in the case of a branched crystal form having a fiber-like spread in water, a spherical crystal form in which the fiber contracts can be obtained when a certain amount of ethanol is included in the preparation.

  An aggregate containing a water-soluble polymer can be obtained by adding another water-soluble polymer at the time of preparing the aggregate. 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 0.1 to 5 times, preferably 0.5 to 2 times the mass of the polymer (A) having a linear polyethyleneimine skeleton. More preferable.

  By containing the water-soluble polymer, the form of the polymer crystal can be changed, and a crystal having a form different from that of a simple aqueous system can be provided. Further, it is effective for increasing the viscosity of the aggregate and improving the stability of the aggregate.

  By treating the aggregate obtained by the above method with a compound containing two or more functional groups that react with the amino group of polyethyleneimine, the polymer crystal surfaces in the aggregate are linked by chemical bonds to each other. Can be obtained.

  As the compound containing at least two functional groups capable of reacting with the amino group at room temperature, aldehyde crosslinking agents, epoxy crosslinking agents, acid chlorides, acid anhydrides, and ester crosslinking agents can be used. Examples of the aldehyde crosslinking agent include malonyl aldehyde, succinyl aldehyde, glutaryl aldehyde, adifoyl 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, adifoyl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, and the like. Examples of the acid anhydride include phthalic anhydride, succinic anhydride, glutaric anhydride, and the like. 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 immersing the obtained aggregate in a solution of a cross-linking agent or by adding a cross-linking agent solution into the aggregate. At this time, the cross-linking agent permeates into the inside of the aggregate together with a change in the osmotic pressure in the system, and connects the crystals with hydrogen bonds to cause a chemical reaction with the nitrogen atom of ethyleneimine.

  The crosslinking reaction proceeds by reaction with free ethyleneimine on the surface of the polyethyleneimine crystal, but in order to prevent the reaction from occurring inside the crystal, the temperature is below the melting point of the crystal forming the aggregate. It is desirable to carry out the reaction, and it is most desirable to carry out the crosslinking reaction at room temperature.

  In the case where the crosslinking reaction is allowed to proceed at room temperature, a method of leaving the aggregate in a mixed state with the crosslinking agent solution is preferable. 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 is preferably 0.05 to 20 mol%, preferably 1 to 10 mol%, based on the number of moles of ethyleneimine units in the polymer (A) having a linear polyethyleneimine skeleton used for forming the aggregate. It is particularly preferred that

  Since the above-mentioned aggregate is composed of a crystalline polymer, it can express aggregate structures having various morphologies. Further, even a small amount of polymer crystal has a high water retention property because it suitably forms a three-dimensional network structure in water. Furthermore, the polymer (A) having a linear polyethyleneimine skeleton to be used is easy to design and synthesize, and to easily adjust the aggregate. Further, the shape of the aggregate can be fixed by crosslinking the polymer crystals in the aggregate with a crosslinking agent.

[Complex]
In the composite of the present invention, a titanium source prepared in advance in a solution having a constant pH value is added to the crystalline aggregate in the aqueous solvent of the polymer (A) described above, and hydrolyzed at a temperature of room temperature to 50 ° C. It can be easily obtained by performing a typical condensation reaction.

  As the compound used as the titanium source, a water-soluble titanium compound (C) that is stable in water can be preferably used.

  Examples of the water-soluble titanium compound (C) include titanium bis (ammonium lactate) dihydroxide aqueous solution, titanium bis (lactate) aqueous solution, titanium bis (lactate) propanol / water mixture, titanium (ethyl acetoacetate) diisopropoxide. And oxides.

  When using the said water-soluble titanium compound (C), it can also react by mixing alkoxysilanes other than titanium. Examples of alkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and tetra-t-butoxysilane.

  Alternatively, the reaction can be carried out by mixing alkyltrialkoxysilanes. Examples of alkyltrialkoxysilanes include methyltrimethoxylane, methyltriethoxylane, ethyltrimethoxylane, ethyltriethoxysilane, n-propyltrimethoxylane, n-propyltriethoxysilane, iso-propyltrimethoxysilane, iso- Propyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycitoxypropyltrimethoxysilane, 3-glycitoxypropyltriethoxysilane, 3 -Aminopropyltrimethoxysilane, 3-aminopropyltriethoxylane, 3-mercaptopropyltomethoxysilane, 3-mercaptotriethoxysilane, 3,3,3-trifluoropropyltri Tosisilane, 3,3,3-trifluoropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxylane, p-chloromethylphenyltrimethoxy Orchid, p-chloromethylphenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxycyan and the like.

  The amount of the silane compound used is preferably 1/2 to 1/10 equivalent of the water-soluble titanium compound (C).

  The hydrolytic condensation reaction to give a complex is promoted by the presence of polyethyleneimine in water or an aqueous solvent such as a mixed solvent of water and the water-soluble organic solvent, but polyethyleneimine is insoluble in water. The reaction does not occur in the aqueous solvent phase, but proceeds only on the surface of the crystalline association of the polymer. Accordingly, the reaction conditions are arbitrary as long as the polymer crystals do not dissolve under the complexing reaction conditions.

  In order to make the polymer crystals insoluble, the presence of water in the aqueous solvent containing the water-soluble organic solvent is preferably 20% or more (volume ratio) during the reaction, and it is preferably 40% or more (volume ratio). ) Is more preferable.

  In the above hydrolytic condensation reaction, a composite can be suitably formed if the amount of the water-soluble titanium compound (C) that is a titanium source is excessive with respect to the ethyleneimine unit that is a monomer unit of polyethyleneimine. The degree of excess is preferably in the range of 2 to 1000 times equivalent, particularly 4 to 1000 times equivalent to the ethyleneimine unit.

  The polymer concentration in the aqueous solvent when forming the polymer crystals is preferably 0.1 to 30% by mass based on the amount of polyethyleneimine contained in the polymer.

  The time for the hydrolytic condensation reaction varies from 1 minute to several hours, but it is more preferable to set the reaction time to 30 minutes to 5 hours in order to increase the reaction efficiency.

  The complex of the present invention is characterized by having various shapes, but the shape is related to the initial shape of the polymer crystal. Therefore, the shape of the obtained composite can be controlled by growing the polymer crystal in an aqueous solvent and adjusting the shape of the polymer crystal and the shape of the crystalline aggregate. Preparation of polymer crystals and crystalline aggregates derived from polymer crystals in an aqueous solvent is as described above.

  The shape of the resulting composite can be adjusted to various shapes such as a fiber network such as a non-woven fabric, a fiber network such as a sponge, or a network of spherical particles such as fine particle deposition. The size of these composites can be of the order of 3 μm to 1 mm in the order of micrometers, but the shape of this size is the association of fiber-like composites with a thickness of 10 to 1000 nm, which is regarded as a basic unit. And a three-dimensional shape formed from a spatial arrangement. The fiber-like composite as the basic unit has a layered structure having a distance of about 1 to 2 nm. In the fine particle deposition network, the fine particles have a size of 20 to 200 nm, and the particles are fused to form a network. Even in this case, there exists a layered structure having a distance of about 1 to 2 nm.

  By using the above-mentioned cross-linked aggregate in which polymer crystals are cross-linked by a chemical bond, the macro shape of the composite can be controlled and the composite can be formed into various shapes. The shape and size can be the same as the size and shape of the container used in preparing the crosslinked aggregate, and can be prepared in any shape such as a disk shape, a column shape, a plate shape, a spherical shape, for example. . Furthermore, it can also be formed into the desired shape by cutting or scraping the cross-linked aggregate. By immersing the thus formed crosslinked aggregate in a solution of a titanium source, a molded body composed of a composite of polymer crystals and titanium oxide can be easily obtained. The time for dipping in the titanium source solution is preferably about 1 to 48 hours.

  The composite of the present invention is composed of a polymer (A) and titanium oxide (B), and the content of titanium oxide (B) in the composite varies within a certain range depending on the reaction conditions. The thing of the range of 20-90 mass% of the whole body can be obtained.

  In the composite of the present invention, since the titanium oxide (B) and the polymer (A) have a layered structure, a fluorescent substance can be incorporated into the polymer (A) layer. For example, the dye molecule can be bound to the polyethyleneimine skeleton by mixing the acid dye molecule and the complex in a solution.

  The composite of the present invention is a novel composite that completely clears the difficulty of shape control at the time of producing a conventional titanium oxide material, and its application is highly expected regardless of the type of business or area. The composite of the present invention includes a polymer having a linear polyethyleneimine skeleton having a strong coordination ability to metal while having an anatase crystal of several nanometers of titanium oxide inside. Various metal injections can be performed easily. This has many possibilities for application as a catalyst, a photocatalyst, and a conductive material.

  Furthermore, the present invention comprises mixing a polymer having a linear polyethyleneimine skeleton and an aqueous solvent, heating the mixed solution to dissolve the polymer having the linear polyethyleneimine skeleton, and then the temperature of the solution. Under a mild condition that a crystalline aggregate of a polymer (A) having a linear polyethyleneimine skeleton is formed by lowering the molecular weight, and then the aggregate and the water-soluble titanium compound (C) are brought into contact with each other. It can be easily produced in a short time and is highly useful.

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

[Analysis of complex by X-ray diffraction method (XRD)]
The isolated and dried composite is placed on a measurement sample holder and set on a wide-angle X-ray diffractometer “Rint-Ultma” manufactured by Rigaku Corporation. Cu / Kα ray, 40 kV / 30 mA, scan speed 1.0 ° / The measurement was performed under the conditions of a minute and a scanning range of 0 to 40 °. (Drying conditions: 25 ° C. × 24 hours)

[Analysis of complex by thermogravimetry (TG) / differential thermal analysis (DTA)]
The composite powder measurement patch was weighed and set in a TG / DTA6300 apparatus manufactured by SII Nano Technology Inc. The temperature increase rate was 10 ° C / minute, and the measurement was performed in a temperature range of 20 ° C to 800 ° C. .

[Analysis of complex by Raman spectroscopy (Raman)]
The Raman spectrum of the composite powder was measured using a (REN) Raman-G99013 manufactured by RENISHAW.

[Shape Analysis of Composite by Scanning Electron Microscope (SEM)]
The isolated and dried composite was placed on a glass slide and observed with a surface observation device VE-8100 manufactured by Keyence Corporation. (Drying conditions: 25 ° C. × 24 hours)

[Observation of complex by transmission electron microscope (TEM)]
The isolated and dried composite was placed on a carbon-deposited copper grid and observed with a JEM-2200FS (manufactured by JEOL Ltd.) transmission electron microscope. (Drying conditions: 25 ° C. × 24 hours)

[UV-Vis reflection spectrum]
The UV-Vis reflection spectrum was measured with a Hitachi U-3500 spectrophotometer.

Synthesis Example 1 <Synthesis of polymer having linear linear polyethyleneimine chain (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 M aqueous hydrochloric acid solution. 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, the precipitated polymer crystal powder was filtered, and the crystal powder was washed with cold water three times. The crystal powder after washing was dried at room temperature in a desiccator to obtain a polymer (L-PEI) having a linear linear polyethyleneimine chain. 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 Polymer (H-PEI) Having Star-Shaped Linear Polyethyleneimine Chain Centered on Benzene Ring>
Jin, J .; Mater. Chem. , 13, 672-675 (2003), the synthesis of a polymer having a star-shaped polymethyloxazoline chain in which six polymethyloxazoline arms are bonded to the center of the benzene ring as a precursor polymer is as follows. I went there.

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 mixed liquid, the conversion rate of the monomer was 98%. 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 above, and a star-shaped linear polyethyleneimine chain in which six linear polyethyleneimine chains were bonded to the benzene ring core. A polymer (H-PEI) having was obtained. ^{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.

Example 1 <Composite from a polymer having a linear linear polyethyleneimine chain>
A certain amount of L-PEI powder obtained in Synthesis Example 1 was weighed and dispersed in distilled water to prepare L-PEI dispersions having various concentrations shown in Table 1. These dispersions were heated to 90 ° C. in an oil bath to obtain completely transparent aqueous solutions having different concentrations. The aqueous solution was allowed to stand at room temperature and naturally cooled to room temperature to obtain opaque L-PEI aggregates (11) to (14) shown in Table 1.

  As a result of performing X-ray diffraction measurement on the obtained aggregate (4), it was confirmed that peaks of scattering intensity appeared at 20.7 °, 27.6 ° and 28.4 °.

5 mL (10 wt%, pH 7) water-soluble titanium lactate (TC310, manufactured by Matsumoto Pharmaceutical Co., Ltd.) was added to 5 mL of an aqueous solution of these aggregates, and the mixture was allowed to stand at 50 ° C. for 1 hour. Washing was repeated alternately (3 times) with distilled water and ethanol in a centrifuge.
The white powder was dried at 50 ° C. for 12 hours and analyzed by SEM, TEM, XRD, Raman, TG / DTA.

  From the XRD measurement of the white powder, a strong scattering peak appeared at 2θ = 3.6 to 4.0 ° in the small angle region in any composite. This result strongly suggests that a layered structure of around 2.2-2.4 nm was formed in the composite. When the polymer in the complex was removed, the scattering peak at this angle disappeared completely (see FIG. 1). The polymer was removed by treatment at 500 ° C. for 3 hours.

  From the TG measurement of the white powder, it was found that the weight loss with increasing temperature appeared significantly, and 20% polymer was included in the composite due to the weight loss due to thermal decomposition of the polymer.

In the Raman spectroscopic measurement, vibration wave numbers derived from anatase appeared at 150, 395, 518, and 638 cm ⁻¹ . From this, it was found that an anatase crystal of titanium oxide was present in the complex (see FIG. 2).

  SEM observation suggested that the white powder was a network with a fiber-like structure (FIGS. 3a-d). In addition, SEM observation before and after the heat treatment at 500 ° C./3 hours confirmed that the fiber shape did not change (FIGS. 4a-b). This suggests that the fiber structure of titanium oxide has strong heat resistance.

  Further, in high-resolution TEM observation, a 2-3 nm size titanium oxide crystal domain was observed from the composite fiber (see FIG. 5). This is consistent with the result of the presence of anatase crystals observed from Raman spectroscopy.

Example 2 <Composite from a polymer having a linear linear polyethyleneimine chain containing a metal ion>
A fixed amount of a metal nitrate equivalent to 1/20 equivalent was used for the L-PEI powder obtained in Synthesis Example 1 and the ethyleneimine (EI) unit mole number of the polymer, and the same method as in Example 1 was used. L-PEI aggregates (21) to (24) shown in Table 2 were obtained.

  The obtained aggregate (23) was subjected to X-ray diffraction measurement, and as a result, it was confirmed that peaks of scattering intensity appeared at 20.7 °, 27.6 ° and 28.4 °.

  5 mL (10 wt%, pH 7) water-soluble titanium compound (TC310, manufactured by Matsumoto Chemical) was added to 5 mL of an aqueous solution containing these metal ions, and the mixture was allowed to stand at 50 ° C. for 1 hour. Washing was repeated alternately (3 times) with distilled water and ethanol in a centrifuge. The white powder was dried at 50 ° C. for 12 hours and analyzed by SEM, TEM, XRD, Raman, TG / DTA.

  FIG. 6 shows an SEM photograph image. It is clear that the shape of the composite changes depending on the type of metal ion particles. The complex obtained from the polymer aggregate incorporating Na ions was a fiber network, whereas the complex obtained from the polymer aggregate added with copper ions was a network of spherical particles.

Example 3 <Composite from Star Polymer>
No. 1 in Example 1 except that H-PEI obtained in Synthesis Example 2 was used. Under the same conditions as in No. 12, a polymer crystalline aggregate was prepared and reacted with a water-soluble titanium compound to obtain a white powder composite. An SEM photograph of the obtained powder is shown in FIG. In the same manner as in Example 1, it was confirmed that the obtained powder contained 23% of polymer.

Application example <Injection of platinum nanoparticles using composite 12>
In general, polyethyleneimine can spontaneously reduce metal ions to metal nanoparticles. The composite of the present invention is composed of a titanium oxide nanocrystal and a polymer of a polyethyleneimine skeleton, and metal nanoparticles can be injected into the composite by using the reducing function of the polymer in the composite. No. in Example 1 above. 2 ml of 0.1 M Na ₂ PtCl ₄ aqueous solution was added to the complex obtained in 12 (50 mg) and the mixture was allowed to stand at room temperature for 1 hour. The powder turned gray was washed 3 times with distilled water and dried at room temperature. When this powder was measured by XRD, scattering peaks derived from platinum crystals appeared at 40.04, 46.42, and 67.64 °. From TEM observation, platinum clusters of about 2-3 nm were observed in the complex. The absorption band of the titanium oxide composite in which platinum was injected was shifted to the longer wavelength side of 390 to 720 nm as compared with that before injection. That is, the titanium oxide composite into which platinum nanoparticles were injected had strong absorption in the visible light region. This strongly suggests that metal nanoparticles can be easily injected into the composite of the present invention. In addition, the reflection spectrum of UV-Vis of the composite before and after platinum nanoparticles are introduced is shown in FIG.

Powder sample No. 1 in Example 1. 12 (a), and 14 (b) is an XRD scattering chart. Powder sample No. 1 in Example 1. It is 12 Raman spectroscopy spectra. Powder sample No. 1 in Example 1. 11 (a), no. 12 (b), no. 13 (c), no. It is a SEM photograph of 14 (d). Powder sample No. 1 in Example 1. It is a SEM photograph of 12 before baking (a) and after baking (b). Powder sample No. 1 in Example 1. Twelve high-resolution TEM photographs, inset, are low-resolution photographs of the fiber fragments of the sample. Powder sample No. 2 in Example 2. 21 (a), no. It is a SEM photograph of 23 (b). 4 is a SEM photograph of a powder sample obtained in Example 3. It is the reflection spectrum of UV-Vis of the composite before (a) and after (b) in which the platinum nanoparticle in an application example is introduced.

Claims (12)

A titanium oxide / polymer composite comprising a polymer (A) having a linear polyethyleneimine skeleton and a titanium oxide (B) having a nanolayer structure. The titanium oxide / polymer composite according to claim 1, wherein the titanium oxide / polymer composite is in a fiber form. The titanium oxide / polymer composite according to claim 2, wherein the titanium oxide / polymer composite comprises a network of fibers. The titanium oxide / polymer composite according to claim 1, wherein the titanium oxide / polymer composite comprises a network of spherical particles. The titanium oxide / polymer composite according to claim 1, wherein a ratio of the linear polyethyleneimine skeleton in the polymer (A) having the linear polyethyleneimine skeleton is 25 to 100 mol%. The titanium oxide / polymer composite according to claim 2, wherein the fiber thickness of the composite is in the range of 10 to 1000 nm. The titanium oxide / polymer composite according to claim 1, wherein the content of titanium oxide (B) is in the range of 20 to 90 mass%. The titanium oxide / polymer composite according to any one of claims 1 to 7, wherein the titanium oxide (B) is composed of an anatase type crystal of several nanometers. A polymer (A) having a linear polyethyleneimine skeleton and titanium oxide (B) is a method for producing a composite having a nanolayer structure,
(I) a step of growing a polymer (A) having a linear polyethyleneimine skeleton into a crystalline aggregate in an aqueous solvent;
(Ii) contacting the crystalline aggregate with the water-soluble titanium compound (C) to form titanium oxide (B) and combine it with the polymer (A);
And a method for producing a titanium oxide / polymer composite. In the step (i), 1/20 to 1/200 equivalent of metal ion (D) is added to an aqueous solvent with respect to the ethyleneimine unit of the linear polyethyleneimine skeleton in the polymer (A). A method for producing a titanium oxide / polymer composite according to claim 9 In the step (ii), the amount of the water-soluble titanium compound (C) to be brought into contact with the crystalline aggregate is 2 to 1000 times equivalent to the ethyleneimine unit of the polymer (A) having a linear polyethyleneimine skeleton. The method for producing a titanium oxide / polymer composite according to claim 9, which falls within the range described above. The method for producing a titanium oxide / polymer composite according to any one of claims 9 to 11, further comprising a step of crosslinking the obtained crystalline aggregates with a crosslinking agent after the step (i).

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