JP2005264421A - Organic and inorganic composite nanofiber, organic and inorganic composite structure and methods for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide organic and inorganic composite nanofiber that can fix and concentrate a variety of substances in its structure and can highly be grouped, organic and inorganic composite structure comprising the organic and inorganic composite fiber and methods for simply producing the same. <P>SOLUTION: The organic and inorganic nanofiber comprises crystalline polymer filament of a polymer having straight-chain polyethyleneimine skeleton and silica covering the crystalline polymer filament. The process for producing the organic and inorganic nanofiber comprises a step where the organic and inorganic composite nanofiber are dissolved in the solvent and the solution is precipitated in the presence of water to obtain the crystalline polymer filament having the straight chain polyethyleneimine skeleton, and a step where the crystalline polymer filament is allowed to come into contact with an alkoxy silane in the presence of water thereby the polymer filament is covered with silica. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic-inorganic composite nanofiber comprising a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and silica covering the crystalline polymer filament, a structure comprising the organic-inorganic composite nanofiber, and It relates to the manufacturing method.

  Nano-sized materials are known to exhibit different properties from the bulk state, and nanofibers with nanometer thickness and tens of times longer than that thickness Because of its high aspect ratio, it is attracting attention as one of the advanced materials because it exhibits a size effect peculiar to fiber shape. Silica nanofibers have a high aspect ratio and a large surface area that are unique to nanofibers, as well as various physical properties such as semiconductor properties, conductivity, surface properties, and mechanical strength that are unique to inorganic materials. The application development is promising in various advanced material fields including the science field. In addition, a single nanofiber (one-dimensional) is aggregated into a cloth-like (two-dimensional) or bulk-like (three-dimensional) structure while maintaining the properties of the nanofiber. The use of silica nanofibers is expected to expand.

  In particular, silica nanofibers combined with organic materials have a wide range of applicability. When combined with materials that can immobilize microorganisms, they can be applied as biofilters with high reactivity and processing efficiency. If it is combined with a material that can immobilize sensor molecules, it can be expected to be applied as a biosensor. Moreover, if it is a material which can adsorb | suck a harmful substance, the application as an efficient filter is anticipated with the porosity and molecular selection system which silica nanofiber itself has.

  It is expected that a novel material that has never existed before can be obtained by combining an organic material having a specific function with an inorganic nanofiber. However, many of these attempts are still in the research stage. As the nanofiber in which an organic material and an inorganic material are combined, for example, an organic-inorganic nanofiber in which a low molecular weight organic compound such as a sugar chain having a helical fiber structure or a cholesterol derivative is combined with silica is disclosed. (See Patent Documents 1 and 2). However, these low-molecular-weight organic compounds are merely used as templates for producing silica nanofibers, and do not exhibit functions specific to nanofibers.

  Also disclosed is a metal oxide composite fine particle in which an organic compound having a plurality of amino groups in a molecule is homogeneously incorporated into an amorphous metal oxide spherical fine particle as a nanometer-sized composite material. (See Patent Document 3). However, since the composite fine particles have a particle shape with an aspect ratio of approximately 1: 1, it is clear that the composite fine particles cannot be aggregated and integrated only with the composite fine particles. It was difficult to form a retained structure.

  On the other hand, as a method for producing a nanofiber in which an organic material and an inorganic material are combined, a method is disclosed in which a silica nanofiber is formed along the template using the above-described low molecular organic material as a template. (See Patent Documents 1 and 2). However, when such an organic material is used, the process becomes complicated, and thus it takes a long time to manufacture the composite. For this reason, when industrial productivity was considered, the method of manufacturing easily in a shorter time was desired. In addition, various studies have been made on technologies for controlling nanostructured materials such as silica nanofibers into filter-like structures such as those described above, but they produce nanofiber structures containing inorganic materials such as silica. It was difficult to do.

JP 2000-203826 A JP 2001-253705 A JP-A-2-263707

  The problem to be solved by the present invention is an organic-inorganic composite nanofiber that can fix and concentrate various substances in the structure and can be highly assembled, and an organic-inorganic composite comprising the organic-inorganic composite nanofiber The object is to provide a structure and a simple manufacturing method thereof.

  In preparing silica nanofibers, it is considered that (i) a template for inducing the nanofiber shape, (ii) a scaffold for fixing silica, and (iii) a catalyst for polymerizing the silica source are indispensable.

  In the present invention, a polymer having a linear polyethyleneimine skeleton is used as the organic material satisfying the above three elements. Although linear polyethyleneimine is soluble in water, water-insoluble crystals can be formed at room temperature due to the presence of water molecules. Such a polymer having a linear polyethyleneimine skeleton forms a crystalline polymer filament of nanometer thickness having crystal properties by forming a crystal between the linear polyethyleneimine skeleton portions of the polymers. it can. This crystalline polymer filament serves as a template. In addition, there are inevitably many free polyethyleneimine chains that are irrelevant to the crystal on the surface of the crystalline polymer filament, and these free chains are in a state of hanging on the surface of the crystalline polymer filament. These chains are scaffolds for fixing the polymerized silica in the vicinity thereof, and simultaneously serve as a catalyst for polymerizing the silica source.

  The ethyleneimine unit in the linear polyethyleneimine skeleton can adsorb various ionic substances including metal ions, and the polymer having the linear polyethyleneimine skeleton can be blocked with other polymers. Since grafting is easy, various functions derived from the other polymer portion can be imparted. In the present invention, a crystalline polymer filament of a polymer having such a linear polyethyleneimine skeleton is used as a template, and the crystalline polymer filament is coated with chemically stable silica, whereby a conventional material is obtained. We realized organic / inorganic nanofibers with excellent functions.

  Further, in the present invention, the crystalline polymer filament is found to give a hydrogel whose shape can be easily controlled in the presence of water, and after forming the hydrogel into an arbitrary shape, a sol-gel reaction is performed. An organic-inorganic composite structure composed of the organic-inorganic nanofibers was realized.

  Furthermore, the crystalline polymer filament can be easily formed by dissolving it in a solvent and then precipitating it in the presence of water, and the sol-gel reaction of silica source using the crystalline polymer filament as a template is also easy. As a result, a simple method for producing an organic-inorganic composite nanofiber was realized.

  That is, the present invention relates to an organic-inorganic composite nanofiber comprising a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and silica covering the crystalline polymer filament, and an organic-inorganic composite comprising the organic-inorganic composite nanofiber. A composite structure is provided.

  Furthermore, the present invention includes (1) a step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent and then precipitating it in the presence of water to obtain a crystalline polymer filament of the polymer having a linear polyethyleneimine skeleton, And (2) providing a method for producing an organic-inorganic nanofiber comprising the step of coating the crystalline polymer filament with silica by bringing the crystalline polymer filament into contact with alkoxysilane.

  Since the organic-inorganic composite nanofiber of the present invention includes a polymer having a linear polyethyleneimine skeleton capable of suitably concentrating metal ions in the central axis of the fiber, it can be usefully used as a metal removal filter. Moreover, since the polyethyleneimine skeleton in the polymer having a linear polyethyleneimine skeleton can be easily cationized, it is possible to adsorb and immobilize various ionic substances. Furthermore, since a polymer having a linear polyethyleneimine skeleton can be easily blocked or grafted with another polymer, it can impart various functions derived from the other polymer portion. As described above, the organic-inorganic composite nanofiber of the present invention can easily impart the above-mentioned various functions in addition to the large surface area and excellent molecular selectivity of silica. It is useful in various fields such as corresponding product fields.

  In addition, the organic-inorganic composite structure of the present invention is a sol-gel prepared by adding a silica source to a dispersion liquid in which crystalline polymer filaments, which are precursors, or a hydrogel composed of crystalline polymer filaments are formed into an arbitrary shape. By reacting, the outer shape can be easily controlled. At this time, a secondary structure having a size of micro to millimeter is present in the organic-inorganic composite structure, and further, an organic-inorganic composite nanofiber having a nanometer thickness is present in the secondary structure. Therefore, according to the present invention, the structure of the composite can be controlled from an organic-inorganic composite nanofiber having a nanometer thickness to an organic-inorganic composite structure having a size of micrometer and millimeter or more.

  In the organic-inorganic composite nanofiber of the present invention, a certain thickness of silica covers the crystalline polymer filament by a sol-gel reaction of a silica source that proceeds only on the surface of the nanometer-thick crystalline polymer filament. Can be easily manufactured. According to this manufacturing method, an organic-inorganic composite nanofiber can be obtained in a shorter reaction time than the conventional method.

  Furthermore, since the crystalline polymer filament in the organic-inorganic composite nanofiber of the present invention can be easily removed by sintering, it can be applied to the production of silica nanotubes containing a tubular space.

  The organic-inorganic composite nanofiber of the present invention comprises a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and silica (silicon oxide) covering the crystalline polymer filament.

[Polymer having linear polyethyleneimine skeleton]
The linear polyethyleneimine skeleton in the present invention refers to a linear 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 polymer filament, it is preferable that the constant chain length of the polymer chain consists of continuous ethyleneimine units. . The length of the linear polyethyleneimine skeleton is not particularly limited as long as the polymer having the skeleton can form a crystalline polymer filament, but in order to form a crystalline polymer filament suitably, the skeleton portion The number of repeating units of the ethyleneimine unit is preferably 10 or more, and particularly preferably in the range of 20 to 10,000.

  The polymer used in the present invention is not particularly limited as long as it has the linear polyethyleneimine skeleton in its structure. Even if the shape is linear, star-shaped or comb-like, it is crystalline in the presence of water. Any material capable of providing a polymer filament may be used.

  Further, these linear, star-shaped or comb-shaped polymers may be composed of only a linear polyethyleneimine skeleton or a block composed of a linear polyethyleneimine skeleton (hereinafter abbreviated as a polyethyleneimine block). And a block copolymer of the other polymer block. Other polymer blocks include, for example, water-soluble polymer blocks such as polyethylene glycol, polypropionylethyleneimine, polyacrylamide, or polystyrene, polyoxazoline polyphenyloxazoline, polyoctyloxazoline, polydodecyloxazoline, polyacrylates Hydrophobic polymer blocks such as polymethyl methacrylate and polybutyl methacrylate can be used. By using a block copolymer with these other polymer blocks, the shape and characteristics of the crystalline polymer filament can be adjusted.

  When the polymer having a linear polyethyleneimine skeleton has other polymer blocks or the like, the proportion of the linear polyethyleneimine skeleton in the polymer is not particularly limited as long as it can form a crystalline polymer filament. In order to form a crystalline polymer filament, the proportion of the linear polyethyleneimine skeleton in the polymer is preferably 25 mol% or more, more preferably 40 mol% or more, and more preferably 50 mol% or more. More preferably it is.

  The polymer having a linear polyethyleneimine skeleton is a polymer having a linear skeleton composed of polyoxazolines serving as a precursor thereof (hereinafter abbreviated as a precursor polymer) under acidic conditions or alkaline conditions. It can be easily obtained by hydrolysis. Therefore, the shape of a polymer 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. 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. Furthermore, when forming a block copolymer having a linear polyethyleneimine skeleton, the precursor polymer is used as a block copolymer, and the linear skeleton composed of polyoxazolines in the precursor is selectively hydrolyzed. Can be obtained at

  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 functional groups are preferred because of high polymerization initiation efficiency, and alkyl bromide and toluene sulfonate alkyl are particularly 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.

  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, 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, an oxazoline monomer can be polymerized 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 hydroxyl group in a side chain such as polyvinyl alcohol with bromine or iodine, or converting it to a toluenesulfonyl group and then using the converted moiety as a polymerization initiating group. .

  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.

  Hydrolysis under acidic conditions can obtain polyethyleneimine hydrochloride, for example, by stirring polyoxazoline under heating in an aqueous hydrochloric acid solution. By treating the obtained hydrochloride with excess ammonium water, a basic polyethyleneimine crystal powder 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, polyoxazoline can be converted to polyethyleneimine by using an aqueous sodium hydroxide solution. After reacting under alkaline conditions, the reaction solution is washed with a dialysis membrane to remove excess sodium hydroxide and to obtain polyethyleneimine crystal powder. 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.

  In the hydrolysis under acidic conditions or alkaline conditions, the amount of acid or alkali used may be 1 to 10 equivalents relative to the oxazoline unit in the polymer. In order to improve reaction efficiency and simplify post-treatment. About 3 equivalents are preferred.

  By the hydrolysis, a linear skeleton composed of polyoxazolines in the precursor polymer becomes a linear polyethyleneimine skeleton, and a polymer having the polyethyleneimine skeleton 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 high solubility in organic solvents compared to (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 polymer filament]
In the crystalline polymer filament of the present invention, a plurality of linear polyethyleneimine skeletons in the primary structure of a polymer having a linear polyethyleneimine skeleton are crystallized in the presence of water molecules, so that the polymers associate with each other. It grows in the form of fibers and has crystal properties in its structure.

  The crystalline polymer filament has a thickness in the range of about 1 to 100 nm, preferably 2 to 30 nm, more preferably 2 to 10 nm, and a length of 10 times or more, preferably 100 times or more of the thickness. The shape (hereinafter, the fiber shape may be referred to as a primary shape).

  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 secondary amines, and the secondary amine type linear polyethyleneimines can be crystallized while being water-soluble. It is.

  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, pp. 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 polymer filament of the polymer 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, star-shaped. Even in the shape of a comb or the like, a crystalline polymer filament can be obtained if the polymer has a linear polyethyleneimine skeleton in the primary structure.

  The presence of crystalline polymer filaments can be confirmed by X-ray scattering, and is derived from a linear polyethyleneimine skeleton in a crystalline hydrogel in the vicinity of 20 °, 27 °, and 28 ° as 2θ angle values in a wide angle X-ray diffractometer (WAXS). The peak value is confirmed.

  Moreover, although the melting point in the differential scanning calorimeter (DSC) of a crystalline polymer filament is dependent also on the primary structure of the polymer of a polyethyleneimine frame | skeleton, the melting | fusing point appears at 45-90 degreeC in general.

  Crystalline polymer filaments can form a hydrogel having a three-dimensional network structure by physical bonding between the crystalline polymer filaments in the presence of water, and further by crosslinking the crystalline polymer filaments with a crosslinking agent. Crosslinked hydrogels with chemical crosslinks can also be formed.

  In the hydrogel of crystalline polymer filaments, the crystalline polymer filaments associate with each other in the presence of water to form a micro to millimeter size three-dimensional shape (hereinafter, the fine three-dimensional shape is a secondary shape). May form). Between the aggregates having these secondary shapes, the crystalline polymer filaments in the aggregate further physically associate to form a crosslinked structure, and a three-dimensional network structure composed of the crystalline polymer filaments as a whole is formed. Since these occur in the presence of water, a hydrogel containing water is formed in the three-dimensional network structure. When a cross-linking agent is used, the crystalline polymer filaments are chemically cross-linked to form a cross-linked hydrogel in which the three-dimensional network structure is fixed by chemical cross-linking.

  The three-dimensional network structure here is different from ordinary polymer hydrogel, and nanoscale crystalline polymer filaments are formed by physical cross-linking by hydrogen bonds of free ethyleneimine chains existing on the surface. The net structure. 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, a crystalline polymer filament grows, and physical crosslinks due to hydrogen bonds are formed between the crystals, so that a three-dimensional network structure appears again.

  The secondary shape formed by the crystalline polymer filament in the hydrogel depends on the geometric shape of the polymer structure, the molecular weight, the non-ethyleneimine moiety that can be introduced into the primary structure, and the conditions for forming the crystalline polymer filament. By adjusting, it can be controlled to various shapes such as a fiber shape, a brush shape, and a star shape. In addition, the hydrogel can maintain a general outer shape (hereinafter, the outer shape of the hydrogel may be referred to as a tertiary shape), but can be arbitrarily deformed by an external force, so that the shape can be easily controlled. It is.

  The crystalline polymer filament utilizes the property that a polymer having a linear polyethyleneimine skeleton is insoluble in water at room temperature, and after the polymer having a linear polyethyleneimine skeleton is dissolved in a solvent, It is obtained by precipitating.

  As a specific method, a polymer having a linear polyethyleneimine skeleton is dissolved in water or a mixed solvent of water and a hydrophilic organic solvent (hereinafter referred to as an aqueous medium), and the solution is heated and then cooled. Examples thereof include a method and a method of dissolving a polymer having a linear polyethyleneimine skeleton in a hydrophilic organic solvent and adding water to the solution.

  As the solvent for dissolving the polymer having a linear polyethyleneimine skeleton, an aqueous medium or a hydrophilic organic solvent can be preferably used. Examples of the hydrophilic organic solvent include hydrophilic organic solvents such as methanol, ethanol, tetrahydrofuran, acetone, dimethylacetamide, dimethylsulfone oxide, dioxirane, and pyrrolidone.

  Precipitation occurs in an aqueous medium because the presence of water is essential to precipitate crystalline polymer filaments from a solution of a polymer having a linear polyethyleneimine skeleton.

  Moreover, in the said method, the hydrogel which consists of a crystalline polymer filament can be obtained by adjusting the quantity of the polymer which has a linear polyethyleneimine frame | skeleton. For example, in the hydrogel, a polymer having a linear polyethyleneimine skeleton is first dispersed in water, and the dispersion is heated to obtain a transparent aqueous solution of the polymer having a polyethyleneimine skeleton. Subsequently, it is obtained by cooling the heated polymer aqueous solution to room temperature. The hydrogel is deformed by an external force such as a shearing force, but has a state like an ice cream capable of maintaining a general shape, and can be deformed into various shapes.

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

  The secondary shape of the crystalline polymer filament in the resulting hydrogel can be adjusted by the process of lowering the temperature of the aqueous polymer solution to room temperature. As an example of a method for lowering the temperature, the polymer aqueous solution is kept at 80 ° C. for 1 hour, then brought to 60 ° C. over 1 hour, and kept at the temperature for another 1 hour. Thereafter, the temperature is lowered to 40 ° C. over 1 hour, and then the solution is naturally lowered to room temperature. The polymer aqueous solution is cooled at once with freezing water at a freezing point, methanol / dry ice at a freezing point, or a refrigerant liquid of acetone / dry ice. After that, there are a method of holding the state in a room temperature water bath or a method of lowering the temperature of the polymer aqueous solution to room temperature in a room temperature water bath or a room temperature air environment.

  Since the process of lowering the temperature of the polymer aqueous solution strongly affects the association between the crystalline polymer filaments in the resulting hydrogel, the secondary shape formed by the crystalline polymer filaments in the hydrogel obtained by the different methods is Not the same.

  When the temperature of the aqueous polymer solution is lowered in a multistage manner with a constant concentration, the secondary shape formed by the crystalline polymer filaments in the hydrogel can be made into a fiber shape. When this is rapidly cooled and then returned to room temperature, it can be in the form of a petal. Moreover, when this is rapidly cooled again with dry ice-like acetone and returned to room temperature, it can be made into a wavy form. Thus, the shape of the secondary shape formed by the crystalline polymer filament in the hydrogel of the present invention can be set to various shapes.

  The hydrogel obtained by the above is an opaque gel in which crystalline polymer filaments made of a polymer having a polyethyleneimine skeleton are formed, and the crystalline polymer filaments are physically cross-linked by hydrogen bonding, A three-dimensional physical network structure is formed. The crystalline polymer filaments in the hydrogel once formed remain insoluble at room temperature, but when heated, the crystalline polymer filaments dissociate and the hydrogel changes to a sol state. Therefore, the physical hydrogel of the present invention can be reversibly changed from sol to gel and from gel to sol by heat treatment.

  The hydrogel referred to in the present invention contains at least water in the three-dimensional network structure, and a hydrogel containing an organic solvent can be obtained by adding a hydrophilic organic solvent during the preparation of the hydrogel. Examples of the hydrophilic organic solvent include hydrophilic organic solvents such as methanol, ethanol, tetrahydrofuran, acetone, dimethylacetamide, dimethylsulfone oxide, dioxirane, and pyrrolidone.

  The content of the 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 hydrophilic organic solvent, the form of the crystalline polymer filament can be changed, and crystals having a form different from that of a simple aqueous system can be provided. For example, even in the case of a branched secondary shape having a fibrous spread in water, when a certain amount of ethanol is included in the preparation, it is possible to obtain a cocoon-like secondary shape in which the fibers contract. it can.

  The hydrogel containing a water-soluble polymer can be obtained by adding another water-soluble polymer during the preparation of the hydrogel in the present invention. 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, more preferably in the range of 0.5 to 2 times the mass of the polymer having a linear polyethyleneimine skeleton.

  The form of the crystalline polymer filament can also be changed by containing the water-soluble polymer, and a secondary shape different from a simple aqueous system can be provided. It is also effective in increasing the viscosity of the hydrogel and improving the stability of the hydrogel.

  In addition, the hydrogel obtained by the above method is treated with a compound containing two or more functional groups that react with the amino group of polyethyleneimine, so that the crystalline polymer filament surfaces in the hydrogel are linked by chemical bonds. 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, 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 immersing the obtained hydrogel in a solution of the cross-linking agent or by adding the cross-linking agent solution into the hydrogel. At this time, the cross-linking agent permeates into the hydrogel as the osmotic pressure changes in the system, where the crystalline polymer filaments are connected to each other by 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 crystalline polymer filament, but in order to prevent the reaction from occurring inside the crystalline polymer filament, the melting point of the crystalline polymer filament forming the hydrogel It is desirable to perform the reaction at the following temperature, and it is most desirable to perform the crosslinking reaction at room temperature.

  When the crosslinking reaction proceeds at room temperature, the crosslinked hydrogel can be obtained by leaving the hydrogel mixed 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% with respect to the number of moles of ethyleneimine units in the polymer having a polyethyleneimine skeleton used for hydrogel formation, and more preferably 1 to 10%.

  The hydrogel can express gel structures having various morphologies because the gelling agent is a crystalline polymer filament. Even a small amount of crystalline polymer filament has a high water retention property because it suitably forms a three-dimensional network structure in water. Furthermore, the polymer having a linear polyethyleneimine skeleton to be used is easy to design and synthesize, and easy to adjust the hydrogel. Further, the shape of the hydrogel can be fixed by crosslinking the crystalline polymer filaments in the hydrogel with a crosslinking agent.

[Organic inorganic composite nanofiber, organic inorganic composite structure]
The organic-inorganic composite nanofiber of the present invention comprises the above-described crystalline polymer filament and silica that covers the crystalline polymer filament. The organic-inorganic composite nanofiber can be obtained by sol-gel reaction of a silica source on the surface of a crystalline polymer filament.

  The organic-inorganic composite nanofiber of the present invention has a thickness of 10 to 1000 nm, preferably 15 to 100 nm, and has a length of 10 times or more, preferably 100 times or more of the thickness. is there. Since the aspect ratio of the organic-inorganic composite nanofiber of the present invention having such a shape is very high, when added to other materials, the strength of the added material is dramatically higher than when particles are added. Can be improved. Moreover, it is also possible to make a shape such as a nonwoven fabric by assembling or hierarchizing nanofibers.

  The content of silica in the organic-inorganic composite nanofiber varies within a certain range depending on reaction conditions and the like, but can be in the range of 30 to 90% by mass of the entire organic-inorganic composite nanofiber. The silica content increases with increasing amount of polymer used in the sol-gel reaction. Moreover, it increases by lengthening the sol-gel reaction time.

  The organic-inorganic composite nanofiber of the present invention is a composite having a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton as a core, and the crystalline polymer filament coated with silica. Therefore, the organic-inorganic composite nanofiber of the present invention can highly concentrate and adsorb metal ions by the ethyleneimine unit present in the crystalline polymer filament. Further, since the ethyleneimine unit can be easily cationized, the organic-inorganic composite nanofiber of the present invention can adsorb and immobilize various ionic substances such as anionic biomaterials. Furthermore, the polymer having the linear polyethyleneimine skeleton is easy to block and graft with other polymers, and the structure side chain and terminal structure are easy to control. Various functions can be imparted to the organic-inorganic composite nanofiber by blocking or controlling the terminal structure.

  Examples of the function addition include immobilization of a fluorescent substance. For example, by using a star-shaped polyethyleneimine centered on porphyrin, a porphyrin residue can be incorporated into the organic-inorganic composite nanofiber. Further, by using a polymer obtained by reacting a small amount of pyrenes, for example, pyrene aldehyde (preferably, 10 mol% or less with respect to imine) on the side chain of the linear polyethyleneimine skeleton, the pyrene residue is combined with an organic-inorganic composite. Can be incorporated into nanofibers. Furthermore, fluorescent dyes such as porphyrins, phthalocyanines, pyrenes having an acidic group, for example, a carboxylic acid group or a sulfonic acid group, are added to the base of the linear polyethyleneimine skeleton (preferably with respect to the number of moles of imine. (1 mol% or less) These fluorescent substances can be incorporated into the organic-inorganic composite nanofiber by using a mixture of a small amount.

  In addition, the organic-inorganic composite nanofiber of the present invention is characterized in that an organic-inorganic composite structure having various shapes can be formed by associating with each other. In the organic-inorganic composite structure, the silica source is brought into contact with the crystalline polymer filament in a state in which the crystalline polymer filament is crosslinked with a crosslinking agent, in a state in which the crystalline polymer filament forms a hydrogel, or in a state in which the hydrogel is crosslinked with a crosslinking agent. Thus, an organic-inorganic composite structure composed of organic-inorganic composite nanofibers can be obtained. Therefore, the organic-inorganic composite has a shape derived from the shape formed by the hydrogel or the crosslinked hydrogel of the crystalline polymer filament described above.

  The organic-inorganic composite structure of the present invention has an arbitrary outer shape by arbitrarily forming a tertiary shape of a hydrogel or a crosslinked hydrogel formed by a crystalline polymer filament, and then coating the crystalline polymer filament in the hydrogel with silica. A structure molded into a shape. In addition, since the secondary shape of the aggregate formed in the hydrogel is also copied in the organic-inorganic composite structure, the organic-inorganic composite nanofiber derived from the secondary shape formed by the crystalline polymer filament is used. There are shapes formed by aggregates (hereinafter referred to as aggregate shapes).

  Thus, since the tertiary shape formed from the crystalline polymer filament can be fixed, the outer shape of the organic-inorganic composite structure of the present invention can be arbitrarily shaped. The aggregate shape of the organic-inorganic composite structure is the geometric shape of the polymer structure used, the molecular weight, the non-ethyleneimine moiety that can be introduced into the primary structure, and the silica source. Depending on the amount used, it can have various shapes such as a fiber shape, a brush shape, a star shape, a lettuce shape, a sponge shape, an aster shape, a cactus shape, and a dandelion shape. The size of these aggregate shapes can be about 3 μm to 1 mm. The shape of this size is a three-dimensional shape formed from the association and spatial arrangement of organic-inorganic composite nanofibers that are basic units. The organic-inorganic composite nanofiber as the basic unit includes a crystalline polymer filament core. That is, in the organic-inorganic composite structure of the present invention, crystalline polymer filaments are connected to each other by a physical bond by hydrogen bonding in water to form a three-dimensional template of various shapes. It is considered that the silica is fixed along the surface, and the organic-inorganic composite nanofibers are associated with each other to form a form arranged in the space.

  The organic-inorganic composite structure of the present invention is an assembly in which crystalline polymer filaments are associated with each other, and a hydrogel obtained by further associating and physically cross-linking is fixed with silica. Alternatively, by adjusting the amount of silica source, etc., when the silica is fixed with silica, the physical cross-linking between the aggregates is cut, and the aggregate of crystalline polymer filaments or a plurality of aggregates of the aggregates are silica. It is also possible to take out an aggregate of organic-inorganic composite nanofibers by fixing with.

The organic-inorganic composite nanofiber of the present invention is
(1) A step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent and then precipitating it in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and (2) Coating the crystalline polymer filament with silica by contacting the crystalline polymer filament with an alkoxysilane in the presence of water;
It can manufacture with the manufacturing method which consists of.

  The step (1) is as described above, and the crystalline polymer filament may be in a hydrogel state or a crosslinked hydrogel state.

  The organic-inorganic composite nanofiber of the present invention can be obtained by bringing a crystalline polymer filament and a silica source into contact with each other in the presence of water by the step (2). In addition, when the crystalline polymer filament is crosslinked with a crosslinking agent, the crystalline polymer filament is in the form of a hydrogel, or the hydrogel is crosslinked with a crosslinking agent, the silica source is brought into contact with An organic-inorganic composite structure composed of fibers can be obtained.

  As a method of bringing the crystalline polymer filament into contact with the silica source, the silica source was dissolved in a solvent that can be used in a normal sol-gel reaction in a dispersion of the crystalline polymer filament in water or a hydrogel or a crosslinked hydrogel of the crystalline polymer filament. The method of adding a solution and making it sol-gel react at room temperature is mentioned. By this method, an organic-inorganic composite nanofiber and an organic-inorganic composite structure can be easily obtained.

  Examples of the compound used as the silica source include tetraalkoxysilanes and alkyltrialkoxysilanes.

  Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and tetra-t-butoxysilane.

  Examples of alkyltrialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, iso-propyltrimethoxysilane, iso -Propyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycitoxypropyltrimethoxysilane, 3-glycitoxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltomethoxysilane, 3-mercaptotriethoxysilane, 3,3,3-trifluoro Propyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, p-chloromethyl Examples thereof include phenyltrimethoxysilane, p-chloromethylphenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, and diethyldiethoxysilane.

  The sol-gel reaction that gives organic-inorganic composite nanofibers proceeds in the presence of crystalline polymer filaments in an aqueous medium such as water or a mixed solution of water and a hydrophilic organic solvent, but the reaction does not occur in the aqueous liquid phase. Instead, it proceeds on the surface of the crystalline polymer filament. Accordingly, the reaction conditions are arbitrary as long as the crystalline polymer filaments do not dissolve under the complexing reaction conditions.

  In order to make the crystalline polymer filament insoluble, in the sol-gel reaction, the presence of water in the aqueous liquid containing the hydrophilic organic solvent is preferably 20% or more, and more preferably 40% or more. .

  In the sol-gel reaction, an organic-inorganic nanofiber can be suitably formed by making the amount of alkoxysilane, which is a silica source, excessive with respect to ethyleneimine, which is a monomer unit of polyethyleneimine. The degree of excess is preferably in the range of 2 to 1000 times equivalent to ethyleneimine.

  The polymer concentration in the aqueous medium when forming the crystalline polymer filament is preferably 0.1 to 30% based on the amount of polyethyleneimine contained in the polymer. In addition, the amount of polyethyleneimine in the aqueous medium can be increased to a concentration exceeding 30% by concentrating in a state where the crystalline form of the crystalline polymer filament is maintained. As a concentration method at this time, a method of filtering the crystalline polymer filament dispersion in water or the crystalline polymer filament hydrogel at atmospheric pressure or under reduced pressure can be used.

  The sol-gel reaction time varies from 1 minute to several days. In the case of methoxysilanes having a high alkoxysilane reaction activity, the reaction time may be from 1 minute to 24 hours. It is more preferable to set it to 30 minutes to 5 hours. In the case of ethoxysilanes and butoxysilanes having low reaction activity, the sol-gel reaction time is preferably 24 hours or longer, and it is also desirable to set the time to about one week.

  By adjusting the geometric shape of the polymer structure, the molecular weight, the non-ethyleneimine moiety that can be introduced into the primary structure, and the formation conditions of the organic-inorganic composite structure when creating the organic-inorganic composite, The aggregate shape in the organic-inorganic composite structure can be adjusted. The aggregate shape is highly dependent on the molecular structure of the polymer used, the degree of polymerization, the composition, and the method for lowering the temperature when preparing the organic-inorganic composite structure.

  For example, as a polymer having a linear polyethyleneimine skeleton, a linear polyethyleneimine having a degree of polymerization of 300 or more is used, and a hydrogel is obtained by naturally lowering the temperature from 80 ° C. or higher to room temperature, and then using the hydrogel. By performing the sol-gel reaction, an organic-inorganic composite structure having a lettuce-like secondary shape can be obtained. In the lettuce-like aggregate shape, the thickness of the leaf-forming portion increases as the polymer concentration in the polymer solution decreases when the polymer is crystallized, but at a concentration of 2% or more, the thickness of the leaf portion is 100 nm. When the concentration is 1% or less, the thickness of the leaf portion is around 500 nm.

  Moreover, when using star-shaped polyethyleneimine, the secondary shape obtained can be controlled also by changing the structure of the central residue which becomes the nucleus. For example, when the central residue has a large pie plane such as porphyrin, the secondary shape in the obtained organic-inorganic composite structure is an aster shape, and the crystal size of one aster shape is 2 to 2. It is about 6 μm. When the concentration is 1% or more, the number of aster arms is small and each arm tends to bind, and when the concentration is less than that, the number of arms is large and each arm tends to separate. In addition, when the central residue is a small structure such as a benzene ring, the aggregate shape in the resulting organic-inorganic composite structure is a fiber shape in which many yarns are bound, and the fibers are entangled with each other, and as a whole A sponge-like organic-inorganic composite structure is formed. The thickness of one fiber shape is around 150 nm.

  Furthermore, organic-inorganic composite structures of various shapes can be obtained by using a crosslinked hydrogel in which crystalline polymer filaments are crosslinked by chemical bonds. The shape and size can be made the same as the size and shape of the container used at the time of preparing the crosslinked hydrogel, and for example, it can be prepared in any shape such as a disk shape, a cylindrical shape, a plate shape, and a spherical shape. Further, the crosslinked hydrogel can be cut or scraped to be formed into a desired shape. An organic-inorganic composite structure having an arbitrary shape can be easily obtained by immersing the crosslinked hydrogel thus formed in a silica source solution. The time for immersing in the silica source solution varies from 1 hour to 1 week depending on the type of silica source to be used. In the solution of ethoxysilanes, about 1 to 7 days is preferable.

  As described above, the organic-inorganic composite nanofiber of the present invention dissolves a polymer having a linear polyethyleneimine skeleton, precipitates it in the presence of water to obtain a crystalline polymer filament, and then in the presence of water, It can be easily produced by bringing a crystalline polymer filament into contact with an alkoxysilane. In this production method, it is possible to perform the step of obtaining crystalline polymer filaments and the silica sol-gel reaction step in a short time. Moreover, the dispersion liquid of a crystalline polymer filament and the hydrogel of a crystalline polymer filament can be easily adjusted, and the organic-inorganic composite structure of the present invention can be easily produced by bringing the dispersion liquid or hydrogel into contact with an alkoxysilane.

  As described above, the organic-inorganic composite nanofiber of the present invention has a linear surface shape in addition to the large surface area of the silica nanofiber and the excellent molecular selectivity and chemical stability derived from the silica to be coated. Various substances can be immobilized and concentrated by a polymer having a polyethyleneimine skeleton. As described above, since the organic-inorganic composite nanofiber of the present invention can fix and concentrate metals and biomaterials in the shape of nano-sized fibers, it can be used in various fields such as the electronic materials field, the bio field, and the environment-friendly product field. It is a useful material in the field.

  The organic-inorganic composite structure of the present invention is a template linked by physical bonds, obtained by forming a crosslinked structure by further associating secondary shapes formed by crystalline polymer filaments in the presence of water. As the silica is immobilized along the organic nano-composite nanofibers, nano-sized organic-inorganic composite nanofibers are associated with each other. Therefore, the organic-inorganic composite structure is a state in which the organic-inorganic composite nanofiber is highly assembled to form a three-dimensional network structure while maintaining the characteristics of the organic-inorganic composite nanofiber. It can be arbitrarily molded with a size of millimeter or more. Since the organic-inorganic composite structure has a three-dimensional network structure inside, it is useful for high-functional filters such as biofilters and air filters, and for catalysts with a high specific surface area by fixing metal inside the fiber structure. it can. In addition, the organic-inorganic composite structure can be easily controlled in its external structure, and various fine secondary shapes can be realized in the structure. As a promising material.

  Therefore, the organic-inorganic composite nanofiber and the organic-inorganic composite structure of the present invention are novel composites that completely clear the difficulty of shape control during the production of conventional silica materials, and are easy to manufacture. High expectations are placed on applications regardless of industry or domain. In addition, since the organic-inorganic composite nanofiber and the organic-inorganic composite structure of the present invention include a crystalline polymer filament made of a polymer having a linear polyethyleneimine skeleton inside, of course, it is a general application area of silica materials. It is also a useful material in the area where polyethyleneimine is applied.

  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 by X-ray diffraction method]
Place the isolated and dried sample on the holder for the measurement sample, set it on the wide-angle X-ray diffractometer “Rint-Ultma” manufactured by Rigaku Corporation, Cu / Kα ray, 40 kV / 30 mA, scan speed 1.0 ° / min. The measurement was performed under conditions of a scanning range of 10 to 40 °.

[Analysis by differential thermal scanning calorimetry]
The isolated and dried sample was weighed with a measurement patch, set in a thermal analysis device “DSC-7” manufactured by Perkin Elmer, and measured in a temperature range of 20 ° C. to 90 ° C. with a temperature increase rate of 10 ° C./min Went.

[Shape analysis by scanning electron microscope]
The isolated and dried sample was placed on a glass slide and observed with a surface observation device VE-7800 manufactured by Keyence.

[Observation with transmission electron microscope]
The isolated and dried sample was placed on a carbon-deposited copper grid, and observed with a Topcon Co., Ltd., EM-002B manufactured by Nolan Instruments, VOYAGER M3055 high-resolution electron microscope.

(Synthesis Example 1)
<Synthesis of linear polyethyleneimine (L-PEI)>
5 g of commercially available polyethyloxazoline (number average molecular weight 500000, average polymerization degree 5000, manufactured by Aldrich) was dissolved in 20 mL of 5M aqueous 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, the precipitated powder was filtered, and the powder was washed 3 times with cold water. The washed powder was dried in a desiccator at room temperature 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 5000 before hydrolysis.

(Synthesis Example 2)
<Synthesis of Porphyrin-Centered Star Polyethylenimine (P-PEI)>
Jin et al. , J .; Porphyrin & Phthalocyanine, 3, 60-64 (1999); Jin, Macromol. Chem. Phys. , 204, 403-409 (2003), a precursor polymer, a porphyrin-centered star-type polymethyloxazoline, was synthesized as follows.

After replacing a 50 ml two-necked flask equipped with a three-way cock with argon gas, 0.0352 g of tetra (p-iodomethylphenyl) porphyrin (TIMPP) and 8.0 ml of N, N-dimethylacetamide were added at room temperature. Stir to dissolve TIMPP completely. To this solution, 3.4 ml (3.27 g) of 2-methyl-2-oxazoline corresponding to 1280 times the number of moles of porphyrin was added, and then the temperature of the reaction solution was brought to 100 ° C. and stirred for 24 hours. The reaction solution temperature was lowered to room temperature, 10 ml of methanol was added, and the mixture solution was concentrated under reduced pressure. The residue was dissolved in 15 ml of methanol and the solution was poured into 100 ml of tetrahydrofuran to precipitate the polymer. In the same manner, the polymer was re-precipitated, and after suction filtration, the obtained polymer was put into a desiccator in which P ₂ O ₅ was placed and sucked and dried with an aspirator for 1 hour. Furthermore, the pressure was reduced with a vacuum pump, and the precursor polymer (TPMO-P) was obtained by drying under vacuum for 24 hours. The yield was 3.05 g, and the yield was 92.3%.

The number average molecular weight by GPC of the obtained precursor polymer (TPMO-P) was 28000, and molecular weight distribution was 1.56. Moreover, the average polymerization degree of each arm was 290 when the integral ratio of the ethylene proton in the polymer arm and the pyrrole ring proton of porphyrin at the polymer center was calculated by ¹ H-NMR. Therefore, the number average molecular weight by ¹ H-NMR was estimated to be 99900. ^{The fact that the} number average molecular weight value by ¹ H-NMR greatly exceeds the number average molecular weight value by GPC is consistent with a general feature in star polymers.

Using this precursor polymer, polymethyloxazoline was hydrolyzed in the same manner as in Synthesis Example 1 to obtain star-shaped polyethyleneimine (P-PEI) in which four polyethyleneimines were bonded to the porphyrin center. ^{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.

(Synthesis Example 3)
<Synthesis of star-shaped polyethyleneimine (B-PEI) centered on benzene ring>
Jin, J .; Mater. Chem. , 13, 672-675 (2003), a star-shaped polymethyloxazoline having 6 polymethyloxazoline arms bonded to the center of the benzene ring as the precursor polymer was performed 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 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 22700, 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, the 1.98 ppm peak derived from the side chain methyl of the precursor polymer before hydrolysis completely disappeared.

  The obtained star-shaped polymethyloxazoline was hydrolyzed by the same method as in Synthesis Example 1 to obtain star-shaped polyethyleneimine (B-PEI) in which six polyethyleneimines were bonded to the benzene ring core.

(Synthesis Example 4)
<Synthesis of block copolymer PEG-b-PEI>
A block copolymer of polyethylene glycol and polyoxazoline, which is a precursor block polymer, is performed as follows using a polymer in which tosylate is bonded to the end of polyethylene glycol having a number average molecular weight of 4000 as a polymerization initiator (PEG-I). It was.

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%.

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, and 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 12000 and the molecular weight distribution was 1.27.

Using this precursor block polymer, polyoxazoline 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.

(Example 1)
<Organic-inorganic composite structure from linear polyethyleneimine system>
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 hydrogels (11) to (15). The obtained hydrogel was deformed when a shearing force was applied, but was an ice cream-like hydrogel capable of maintaining a general shape.

  As a result of X-ray diffraction measurement of the obtained hydrogel (15), it was confirmed that peaks of scattering intensity appeared at 20.7 °, 27.6 °, and 28.4 °. Moreover, the endothermic peak was confirmed at 64.7 ° C. from the measurement result of the endothermic state change by the calorimeter. From these measurement results, the presence of L-PEI crystals in the hydrogel was confirmed.

  As shown in Table 1, 1 mL or 2 mL of a mixture solution of tetramethoxysilane (TMSO) and ethanol (volume ratio) of 1 mL or 2 mL was added to 1 mL of the hydrogel thus obtained. After stirring for 1 minute, it was left as it was for 40 minutes. Then, it wash | cleaned with excess acetone, and it wash | cleaned 3 times with the concentric separator. The obtained solid was collected and dried at room temperature to obtain organic-inorganic composite structures 11-15. From the X-ray diffraction measurement of the organic-inorganic composite structure 14, peaks of scattering intensity appeared at 20.5 °, 27.2 °, and 28.2 °.

  When the obtained organic-inorganic composite structure was observed with a scanning microscope, a lettuce-like aggregate shape was confirmed in each of the organic-inorganic composite structures 11-15. A scanning micrograph of the obtained organic-inorganic composite structure 14 is shown in FIG. Further, when the organic-inorganic composite structure 14 was observed with a transmission electron microscope, it was confirmed that the surface of the crystalline polymer filament having a thickness of about 5 nm was coated with silica as shown in FIG.

(Example 2)
<Organic-inorganic composite structure using porphyrin-containing star-shaped polyethyleneimine>
In Example 1, instead of using L-PEI powder, P-PEI synthesized in Synthesis Example 2 was used, and P-PEI hydrogels (21) having various concentrations shown in Table 2 were prepared in the same manner as in Example 1. To (25) were obtained. The obtained hydrogel was deformed when a shearing force was applied, but was an ice cream-like hydrogel capable of maintaining a general shape.

  As a result of X-ray diffraction measurement of the obtained hydrogel (25), it was confirmed that peaks of scattering intensity appeared at 20.4 °, 27.3 °, and 28.1 °. Moreover, the endothermic peak was confirmed at 64.1 degreeC by the measurement result of the endothermic state change by a calorimeter. From these measurement results, the presence of P-PEI crystals in the hydrogel was confirmed.

  As shown in Table 2, 1 mL or 2 mL of a mixture of tetramethoxysilane (TMSO) and ethanol (volume ratio) of 1 mL or 2 mL was added to 1 mL of the hydrogel thus obtained. After stirring for 1 minute, it was left as it was for 40 minutes. Then, it wash | cleaned with excess acetone, and it wash | cleaned 3 times with the concentric separator. The obtained solid was collected and dried at room temperature to obtain organic-inorganic composite structures 21 to 25. As a result of X-ray diffraction measurement of the organic-inorganic composite structure 24, the same scattering peaks as before silica coating appeared at 20.5 °, 27.4 °, and 28.1 °.

  When the obtained organic-inorganic composite structure was observed with a scanning microscope, all of the organic-inorganic composite structures 21 to 25 were confirmed to have an aster-like aggregate shape. A scanning micrograph of the obtained organic-inorganic composite structure 24 is shown in FIG.

(Example 3)
<Organic inorganic composite structure using polyethyleneimine with benzene ring center>
In Example 1, instead of using L-PEI powder, B-PEI synthesized in Synthesis Example 3 was used, and B-PEI hydrogels (31) having various concentrations shown in Table 3 were prepared in the same manner as in Example 1. To (35) was obtained. The obtained hydrogel was deformed when a shearing force was applied, but was an ice cream-like hydrogel capable of maintaining a general shape. The gelation temperature of the resulting hydrogel is shown in Table 3.

  The obtained hydrogel (34) was subjected to X-ray diffraction measurement, and as a result, it was confirmed that peaks of scattering intensity appeared at 20.3 °, 27.3 °, and 28.2 °. Moreover, the endothermic peak was confirmed at 55.3 ° from the measurement result of the endothermic state change by the calorimeter. From these measurement results, the presence of B-PEI crystals in the hydrogel was confirmed.

  As shown in Table 3, 1 mL or 2 mL of a mixture of tetramethoxysilane (TMSO) and ethanol (volume ratio) of 1 mL or 2 mL was added to 1 mL of the hydrogel thus obtained. After stirring for 1 minute, it was left as it was for 40 minutes. Then, it wash | cleaned with excess acetone, and it wash | cleaned 3 times with the concentric separator. The obtained solid was collected and dried at room temperature to obtain organic-inorganic composite structures 31-35. From the X-ray diffraction measurement of the organic-inorganic composite structure 34, peaks of scattering intensity appeared at 20.5 °, 27.5 °, and 28.3 °.

  When the obtained organic-inorganic composite structure was observed with a scanning microscope, all of the organic-inorganic composite structures 31-35 were in the form of sponges in which fiber-like aggregate shapes gathered together. A scanning micrograph of the obtained organic-inorganic composite structure 34 is shown in FIG.

Example 4
<Hydrogel using block polymer>
In Example 1, the PEG-b-PEI hydrogel 41 having a concentration of 5% was prepared in the same manner as in Example 1 except that the PEG-b-PEI synthesized in Synthesis Example 4 was used instead of the L-PEI powder. Obtained.

  To 1 mL of the hydrogel thus obtained, 1.5 mL of a mixed solution of tetramethoxysilane (TMSO) and ethanol (volume ratio) 1/1 (volume ratio) was added, and the ice cream state was lightly stirred for 1 minute, and then directly 40 Left for a minute. Then, it wash | cleaned with excess acetone, and it wash | cleaned 3 times with the concentric separator. The obtained solid was collected and dried at room temperature, and an organic-inorganic composite structure 41 was obtained in the same manner as in Example 1.

  When the obtained organic-inorganic composite structure was observed with a scanning microscope, a cactus-like aggregate shape was confirmed in the organic-inorganic composite structure 41. A scanning micrograph of the obtained organic-inorganic composite structure 34 is shown in FIG.

(Example 5)
<Organic-inorganic composite structure from polyethyleneimine hydrogel containing organic solvent>
Instead of distilled water in Example 1, the same procedure as in (14) in Example 1 was used except that a mixed solution of water and a hydrophilic organic solvent in which the organic solvent shown in Table 5 was contained in distilled water was used. Organic solvent-containing hydrogels (51) to (53) were obtained. The obtained hydrogel was deformed when a shearing force was applied, but was an ice cream-like hydrogel capable of maintaining a general shape.

  As shown in Table 5, add 1 mL or 2 mL of a 1/1 (volume ratio) mixture of tetramethoxysilane (TMSO) and ethanol to 1 mL of the hydrogel thus obtained. After lightly stirring for 1 minute, it was left as it was for 40 minutes. Then, it wash | cleaned with excess acetone, and it wash | cleaned 3 times with the concentric separator. The obtained solid was collected and dried at room temperature to obtain organic-inorganic composite structures 51-53.

  When the obtained organic-inorganic composite structure was observed with a scanning microscope, the organic-inorganic composite structures 51-53 all had different aggregate shapes. The scanning micrograph of the obtained organic-inorganic composite structure 51 is shown in FIG. 6, the scanning micrograph of the organic-inorganic composite structure 52 is shown in FIG. 7, and the scanning micrograph of the organic-inorganic composite structure 53 is shown in FIG. Shown respectively.

(Example 6)
<Organic-inorganic composite structure from polyethyleneimine hydrogel cross-linked with dialdehyde>
As shown in Example 1, 1 mg of hydrogel with 3% L-PEI concentration: 20 mg) was prepared into a plate and added to 10 mL of an aqueous solution of glutarylaldehyde (5%) at room temperature. Left for 24 hours. The hydrogel before chemical crosslinking was in an ice cream state, and the shape was arbitrarily changed by shearing force, but the shape of the hydrogel obtained by chemical crosslinking treatment did not change due to shearing force.

  The plate was immersed in 2 mL of a TMOS / EtOH (1/1) mixture for 24 hours. The plate was repeatedly immersed in acetone and washed. Thereby, an organic-inorganic composite structure 61 was obtained.

  A scanning micrograph of the obtained organic-inorganic composite structure 61 plate is shown in FIG. 9, and a scanning micrograph of the surface of the organic-inorganic composite structure plate is shown in FIG.

It is a scanning microscope picture of the organic-inorganic composite structure having a lettuce-like aggregate shape in Example 1 of the present invention. It is a transmission electron micrograph of the crystalline polymer filament coat | covered with the silica in the organic inorganic composite structure in Example 1 of this invention. It is a scanning microscope picture of the organic inorganic composite structure which has an aster-like aggregated body shape in Example 2 of this invention. It is a scanning microscope picture of the organic inorganic composite structure which has a fiber-like aggregated body shape in Example 3 of this invention. It is a scanning microscope picture of the organic inorganic composite structure which has a cactus-like aggregated body shape in Example 4 of this invention. It is a scanning microscope picture of the organic inorganic composite structure which has from the system containing acetone in Example 5 of this invention. It is a scanning microscope picture of the organic inorganic composite structure from the system containing DMF in Example 5 of the present invention. It is a scanning microscope picture of the organic inorganic composite structure from the system containing ethanol in Example 5 of the present invention. It is a scanning microscope picture of the organic inorganic composite structure plate from the system bridge | crosslinked by the chemical bond in Example 6 of this invention. It is a scanning microscope picture of the organic inorganic composite structure plate surface from the system bridge | crosslinked by the chemical bond in Example 6 of this invention.

Claims (16)

An organic-inorganic composite nanofiber comprising a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and silica covering the crystalline polymer filament. The organic-inorganic composite nanofiber according to claim 1, wherein the polymer having a linear polyethyleneimine skeleton is any one of a linear shape, a star shape, and a comb shape. The organic-inorganic composite nanofiber according to claim 1 or 2, wherein the polymer having a linear polyethyleneimine skeleton is composed of a block copolymer of a linear polyethyleneimine block and another polymer block. The organic-inorganic composite nanofiber according to any one of claims 1 to 3, wherein a ratio of the polyethyleneimine skeleton in the polymer having the linear polyethyleneimine skeleton is 25 mol% or more. The organic-inorganic composite nanofiber according to any one of claims 1 to 4, wherein the silica content is in the range of 30 to 90 mass%. The organic-inorganic composite nanofiber according to any one of claims 1 to 5, wherein the thickness is in the range of 10 to 1000 nm. The organic-inorganic composite nanofiber according to any one of claims 1 to 6, wherein a thickness of the crystalline polymer filament is in a range of 1 to 100 nm. An organic-inorganic composite structure in which the organic-inorganic composite nanofibers according to any one of claims 1 to 7 are associated with each other by association of crystalline polymer filaments in the organic-inorganic nanofibers. The organic-inorganic composite structure according to claim 8, wherein the crystalline polymer filaments are crosslinked with a crosslinking agent. (1) A step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent and then precipitating it in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and (2) Coating the crystalline polymer filament with silica by contacting the crystalline polymer filament with an alkoxysilane in the presence of water;
The manufacturing method of the organic inorganic nanofiber which consists of. The method for producing an organic-inorganic composite nanofiber according to claim 10, wherein the alkoxysilane is a trivalent or higher-valent alkoxysilane. The amount of alkoxysilane brought into contact with the crystalline polymer filament in the step (2) is in the range of 2 to 1000 times equivalent to the ethyleneimine unit of the polymer having a linear polyethyleneimine skeleton that forms the crystalline polymer filament. The method for producing an organic-inorganic composite nanofiber according to claim 10 or 11. (1 ′) A polymer having a linear polyethyleneimine skeleton is dissolved in a solvent, and then precipitated in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and the crystalline property Obtaining a hydrogel comprising polymer filaments;
(2 ′) a step of coating the crystalline polymer filament in the hydrogel with silica by bringing the hydrogel composed of the crystalline polymer filament into contact with an alkoxysilane in the presence of water;
A method for producing an organic-inorganic composite structure comprising: The method for producing an organic-inorganic composite structure according to claim 13, wherein the hydrogel is crosslinked with a crosslinking agent after the step (1 '). The method for producing an organic-inorganic composite structure according to claim 13 or 14, wherein the alkoxysilane is a trivalent or higher-valent alkoxysilane. The amount of alkoxysilane to be contacted with the hydrogel in the step (2 ′) is 2 to 1000 times the ethyleneimine unit of the polymer having a linear polyethyleneimine skeleton that forms a crystalline polymer filament in the hydrogel. The method for producing an organic-inorganic composite structure according to any one of claims 13 to 15, which is in an amount range.