Structures, methods for manufacturing structures, and thermal insulation materials

Abstract

A structure according to one embodiment of the present disclosure comprises: a plurality of nano particles or nano fibers each having a surface coated with an amphipathic molecule or an organic silane molecule; and crosslinking parts at which the plurality of nano particles or nano fibers are connected to each other.

Description

[Technical Field]

[0001] This disclosure relates, for example, to structures using nanoparticles or nanofibers, methods for manufacturing such structures, and thermal insulation materials. [Background technology]

[0002] For example, Patent Document 1 discloses a heat insulating sheet having a sheet-like structure in which hollow particles are linked together, the average pore diameter of the sheet is 70 nm or less, the porosity of the sheet is 90 to 99 volume%, and the light transmittance is 85% or more. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2012-102204 [Overview of the project]

[0004] Incidentally, when it comes to thermal insulation materials, there is a desire to improve light transmittance in order to enhance the aesthetic appeal of products using them.

[0005] It is desirable to provide a structure having high light transmittance, a method for manufacturing the structure, and a thermal insulation material.

[0006] A structure according to one embodiment of the present disclosure comprises a plurality of nanoparticles or nanofibers whose surfaces are coated with amphiphilic molecules or organosilane molecules, and a crosslinking portion that connects the plurality of nanoparticles or nanofibers to each other. It is equipped with such that the nanoparticles or nanofibers and the crosslinking portion form a covalent bond. .

[0007] A method for manufacturing a structure according to one embodiment of the present disclosure involves adding amphiphilic molecules or organosilane molecules to a dispersion in which a plurality of nanoparticles or a plurality of nanofibers are dispersed, thereby coating the surface of the plurality of nanoparticles or a plurality of nanofibers, and further adding a crosslinking agent to connect the plurality of nanoparticles or a plurality of nanofibers to each other via crosslinking portions made of the crosslinking agent. Furthermore, the nanoparticles or nanofibers and the crosslinked portion form a covalent bond. .

[0008] The heat insulating material according to one embodiment of the present disclosure includes the structure according to one embodiment of the present disclosure.

[0009] In the structure according to one embodiment of the present disclosure, the manufacturing method of the structure according to one embodiment, and the heat insulating material according to one embodiment, a plurality of nanoparticles or a plurality of nanofibers whose surfaces are coated with amphiphilic molecules or organosilane molecules are connected to each other via crosslinking portions, thereby preventing aggregation between the plurality of nanoparticles or the plurality of nanofibers, and forming voids between the connected plurality of nanoparticles or between the plurality of nanofibers.

Brief Description of Drawings

[0010] [Figure 1] It is a schematic diagram showing an example of the schematic configuration of the structure according to one embodiment of the present disclosure. [Figure 2A] It is a schematic diagram showing an example of the structure of the nanoparticles shown in FIG. 1. [Figure 2B] It is a schematic diagram showing another example of the structure of the nanoparticles shown in FIG. 1. [Figure 3] It is an image diagram when photographing the structure of this embodiment using a transmission electron microscope. [Figure 4A] It is a schematic diagram showing an example of the mode of connection between nanoparticles when the nanoparticles shown in FIG. 2A are used. [Figure 4B] It is a schematic diagram showing another example of the mode of connection between nanoparticles when the nanoparticles shown in FIG. 2B are used. [Figure 5A] It is a schematic diagram explaining the conditions of the crosslinking portion where the nanoparticles connected to each other do not aggregate. [Figure 5B] It is a schematic diagram explaining the conditions of the crosslinking portion where the nanoparticles connected to each other do not aggregate. [Figure 6] It is a diagram showing the spatial arrangement of a plurality of nanoparticles connected by a crosslinking portion. [Figure 7] It is a flowchart showing the manufacturing process of the structure shown in FIG. 1. [Figure 8]This is a schematic diagram showing an example of the general configuration of a structure relating to a modified example of this disclosure. [Figure 9] This is a schematic diagram showing another example of the schematic configuration of the structure relating to the modified form of the present disclosure. [Figure 10] This is a characteristic diagram showing the relationship between the particle size of nanoparticles and their transmittance. [Modes for carrying out the invention]

[0011] The embodiments of this technology will be described in detail below with reference to the drawings. The following description is one specific example of this disclosure, and this disclosure is not limited to the following embodiments. Furthermore, this disclosure is not limited to the arrangement, dimensions, and dimensional ratios of each component shown in each figure. The order of description is as follows. 1. Embodiment (Example of a structure consisting of multiple nanoparticles that are surface-modified and linked to each other via crosslinking portions) 1-1. Structure 1-2. Method for manufacturing the structure 1-3. Action and Effects 2. Variations (other examples of structures) 3. Other application examples

[0012] <1. Embodiment> (1-1. Structure of the Structure) Figure 1 schematically shows an example of the configuration of a structure (structure 1) according to one embodiment of the present disclosure. Structure 1 is used as an insulating material to reduce the heat balance of a window, for example, by being attached to a glass window or sandwiched between double-glazed windows. In this embodiment, structure 1 consists of a plurality of nanoparticles 11 whose surfaces are coated with amphiphilic molecules 12 (Figure 2A) or organosilane molecules 13 (Figure 2B), which are linked to each other via crosslinking portions 21.

[0013] The nanoparticles 11 are, for example, silica particles. The average particle size (median diameter) of the nanoparticles 11 is, for example, 14 nm or less, preferably 9 nm or less. The surface of the nanoparticles 11 is coated with an amphiphilic molecule 12, for example, as shown in Figure 2A. Alternatively, the surface of the nanoparticles 11 is deactivated by reacting with an organosilane molecule 13, for example, as shown in Figure 2B. As a result, multiple nanoparticles 11 cannot form covalent bonds with each other.

[0014] The average particle size (median diameter) of the nanoparticles 11 is determined as follows. First, the structure 1 to be measured is processed and thinned using methods such as Focused Ion Beam (FIB). When using the FIB method, a carbon film and a tungsten film are formed as protective films as a pretreatment before observing the transmission electron microscope (TEM) image of the cross-section described later. The carbon film is formed on the surface of structure 1 by vapor deposition. The tungsten film is formed on the surface of structure 1 by vapor deposition or sputtering. As a result, a cross-section of structure 1 is formed by thinning.

[0015] The cross-section of the obtained thin section sample will be observed using a transmission electron microscope (FEI Tecnai G2) with an acceleration voltage of 200kV and a field of view of 50nm × 50nm, allowing for the observation of multiple nanoparticles 11. A TEM image will then be taken. The imaging position will be randomly selected from the thin section sample.

[0016] Next, 50 nanoparticles 11 whose diameter is clearly identifiable in the direction of the observation plane are selected from the captured TEM images. If there are fewer than 50 nanoparticles 11 with clearly identifiable diameters within one captured field of view, 50 nanoparticles 11 with clearly identifiable diameters in the direction of the observation plane are selected from multiple fields of view. Figure 3 is an illustrative image of a TEM image taken of structure 1 using a transmission electron microscope. For example, in Figure 3, nanoparticles a and b, whose diameters are clearly identifiable, are selected. On the other hand, nanoparticles c and d, for example, are not suitable for measurement because their shapes cannot be confirmed due to overlapping nanoparticles 11 in the depth direction of observation. The maximum diameter of each of the 50 selected nanoparticles 11 is measured.

[0017] Here, the maximum diameter is defined as the maximum distance between two parallel lines drawn from any angle so as to be tangent to the contour of the nanoparticle 11 (the so-called maximum Ferret diameter). When measuring the maximum diameter (maximum Ferret diameter), the diameter of the particle portion excluding the coating portion (amphiphilic molecule 12 or organosilane molecule 13) that covers the surface of the nanoparticle 11 is measured. By calculating the median of the 50 maximum diameters (maximum Ferret diameters) obtained in this way, the average particle diameter (median diameter) of the nanoparticle 11 is obtained.

[0018] As described above, the amphiphilic molecule 12 coats the surface of the nanoparticles 11 to prevent them from bonding together. Specific examples of amphiphilic molecules 12 include surfactant molecules, amino acid molecules, and polymers such as block copolymers of phospholipids and polyalkylene glycols.

[0019] The organic silane molecule 13 is for inactivating the surface of the nanoparticles 11 to prevent the bonding between the plurality of nanoparticles 11 as described above. The organic silane molecule 13 preferably has a reactive functional group for forming a covalent bond with the nanoparticles 11 and a covalent bond with the crosslinking portion 21. Examples of the reactive functional group include a vinyl group, a methacryl group, an acryl group, a glycidyl group, a mercapto group, an amino group, a hydrosilyl group, a hydroxyl group, a carboxyl group, a cyano group, an amino group, a cyano group, etc. Examples of the organic silane compound having the above reactive functional group include those represented by the following general formula (1) or general formula (2). (Chemical formula 1) R 1 X Si(OR 2 ) 4-X ···(1) (Chemical formula 2) R 1 X SiCl 4-X ···(2) (R 1 is any one of a hydrogen atom, a vinyl group, an acryloxy group, a methacryloxy group, an aminopropyl group, a glycidoxypropyl group, and a mercaptopropyl group. R 2 is any one of a methyl group, an ethyl group, a propyl group, and an isopropyl group. X is an integer of 3 or less.)

[0020] Incidentally, regarding the presence or absence of the amphiphilic molecule 12 and the organic silane molecule 13 coating the surface of the nanoparticles 11 and the mode of bonding between the nanoparticles 11 and the amphiphilic molecule 12 or the organic silane molecule 13, it can be confirmed by, for example, component analysis or composition analysis. Examples of the component analysis and composition analysis include Fourier transform infrared spectroscopy (FT-IR), gas chromatograph analysis (GC), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance analysis (NMR), and energy dispersive X-ray analysis (EDX). Regarding the presence or absence of the amphiphilic molecule 12 and the organic silane molecule 13 coating the surface of the nanoparticles 11 and the mode of bonding between the nanoparticles 11 and the amphiphilic molecule 12 or the organic silane molecule 13, it can be analyzed using one or a plurality of the above analysis methods.

[0021] As described above, the crosslinking portion 21 connects multiple nanoparticles 11 to each other. Specifically, the crosslinking portion 21 is an organic or inorganic substance that directly covalently bonds with the nanoparticles 11, for example, as shown in Figure 4A. Alternatively, the crosslinking portion 21 is an organic or inorganic substance that indirectly covalently bonds with the nanoparticles 11 via an organic silyl group (organosilane molecule 13), for example, as shown in Figure 4B. The crosslinking portion 21 forms a covalent bond with one or two nanoparticles 11.

[0022] The length of the crosslinking portion 21 is preferably less than half (1 / 2) of the average particle diameter of the nanoparticles 11. Specifically, as shown in Figure 5A, the length of the crosslinking portion 21 is preferably such that, when two nanoparticles 11B and 11C are bonded to one nanoparticle 11A via the crosslinking portion 21 at their furthest positions (diagonal positions), the nanoparticles 11B and 11C do not touch each other. That is, as shown in Figure 5B, the length of the crosslinking portion 21 is preferably less than 60° of the circumference of the nanoparticle 11 (11A) (= π / 6 of the diameter). This prevents aggregation of multiple nanoparticles 11 within the structure 1.

[0023] Examples of such crosslinked portions 21 include crosslinking agents having two or more reaction sites. Among these, examples of crosslinking agents that directly form covalent bonds with nanoparticles 11 include silane compounds represented by the following general formulas (3), (4), (5), or (6). (C3)R 3 Y Si(OR 4 ) 4-Y ...(3) (C4)R 3 Y SiCl 4-Y ...(4) (C5)(R 4 O) 3-Y R 3 Y Si-R 5 -SiR 3 Y (OR4 ) 3-Y ...(5) (C6)Cl 3-Y R 3 Y Si-R 5 -SiR 3 Y Cl 3-Y ...(6) (R 3 R is one of the following: a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, or a phenyl group. 4 R is one of the following: a methyl group, an ethyl group, a propyl group, or an isopropyl group. 5 (Y is one of the following groups: methylene, ethylene, propylene, butylene, pentylene, hexylene, or phenylene. Y is an integer less than or equal to 2.)

[0024] Crosslinking agents that indirectly covalently bond to nanoparticles 11 via organosilyl groups (organosilane molecules 13) include those having two or more reactive functional groups that react with the functional groups of organosilane molecules 13. Examples of such crosslinking agents include polyfunctional allyl (vinyl), polyfunctional thiol, polyfunctional (meth)acrylate, and polyfunctional glycidyl.

[0025] Specific examples of polyfunctional allyl (vinyl) include diallyl ether, diallyl sulfide, diallylamine, diallyl adipate, diallyldimethylsilane, diallyl isophthalate, diallylurea, dimethyldivinylsilane, divinyltetramethyldisiloxane, hexadiene, tetraallyloxyethane, triallyl cyanurate, and triallylamine.

[0026] Specific examples of polyfunctional thiols include ethanedithiol, propanedithiol, hexanedithiol, pentaerythritol tetrakis(mercaptoacetate), pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinan-2,4,6-trione, and trimethylolpropane tris(3-mercaptobutyrate).

[0027] Specific examples of polyfunctional (meth)acrylates include diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, tetraethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate.

[0028] Specific examples of polyfunctional glycidyls include glycidyl ether type epoxy resins such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and resorcinol diglycidyl ether, as well as diglycidyl phthalate esters and diglycidyl dimer esters, triglycidyl ether triphenylmethane, tetraglycidyl ether tetraphenylethane, bisphenol S diglycidyl ether, cresol novolac glycidyl ether, triglycidyl isocyanurate, and tetrabrom bisphenol A diglycidyl ether.

[0029] In the structure 1 of this embodiment, the number of nanoparticles 11 in contact with a single nanoparticle 11 is 1 to 4, and within the structure 1, the 4 nanoparticles 11 have a diamond structure, for example, as shown in Figure 6. Such a structure 1 has a porosity of, for example, 66% or more, which allows the structure 1 to obtain high light transmittance.

[0030] The voids G formed in structure 1 consist, for example, of continuous pores. These pores have an average pore diameter of, for example, several nanometers to tens of nanometers. As a result, structure 1 has a fine-grained, spongy bulk structure. Normally, air is present inside the voids G, but the thermal conductivity of structure 1 can be further reduced by creating a vacuum or by sealing in a gas with a lower thermal conductivity than air, such as helium (He) or argon (Ar).

[0031] The number of nanoparticles 11 in nearest proximity to a single nanoparticle 11 can be determined, for example, as follows. First, the structure 1 to be measured is processed into thin sections using the FIB method or the same method as when determining the average particle size (median diameter) of the nanoparticles 11 as described above. The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Tecnai G2, manufactured by FEI) with an acceleration voltage of 200kV and a field of view of 50nm × 50nm, so that multiple nanoparticles 11 can be observed, and a TEM image is taken. The imaging position is randomly selected from the test piece.

[0032] Next, 50 nanoparticles 11 whose diameter can be clearly identified in the direction of the observation plane are selected from the captured TEM images. If there are fewer than 50 nanoparticles 11 whose diameter can be clearly identified in the direction of the observation plane within one captured field of view, 50 nanoparticles 11 whose diameter can be clearly identified in the direction of the observation plane are selected from multiple fields of view. For example, in Figure 3, nanoparticles e and f, whose diameter can be clearly identified in the direction of the observation plane, are selected. On the other hand, nanoparticles c and d, for example, are not suitable for measurement because the particles overlap in the depth direction of the observation, making it impossible to correctly determine the position of the particles.

[0033] For each of the 50 selected nanoparticles 11, the number of nanoparticles (e.g., nanoparticles e-1, e-2, e-3 and nanoparticles f-1, f-2, f-3, f-4) located closer than a certain distance from other nanoparticles (e.g., nanoparticles e and f) is measured. Here, the certain distance is defined as 0.5 times the diameter of the nanoparticle 11, which is the maximum length of the crosslinking portion 21. Since the crosslinking portion 21 does not appear in electron microscope images, it is difficult to directly confirm its existence. However, if the crosslinking portion 21 does not exist, the linked structure of the nanoparticles 11 cannot be maintained. Therefore, it can be assumed that a crosslinking portion 21 exists between the nanoparticles 11. In other words, the number of nanoparticles 11 closest to one nanoparticle 11 corresponds to the number of nanoparticles 11 bound via the crosslinking portion 21.

[0034] The number of nanoparticles 11 that are closest to one nanoparticle 11, that is, the number of nanoparticles 11 that are bonded via the cross-linking portion 21, is the same as the number of other nanoparticles 11 that are bonded to one nanoparticle 11 via the cross-linking portion 21. For example, if one nanoparticle 11 is bonded to just one other nanoparticle 11 via multiple cross-linking portions 21, then the number of nanoparticles 11 that are bonded to that nanoparticle 11 via the cross-linking portion 21 is 1. By calculating the simple average (arithmetic mean) of the number of other nanoparticles 11 that are bonded via the cross-linking portion 21 to each of the 50 nanoparticles 11 obtained in this way, the "number of nanoparticles 11 that are closest to one nanoparticle 11" can be obtained.

[0035] Furthermore, when the component analysis and compositional analysis of structure 1 are performed using the above FT-IR, GC, XPS, NMR, and EDX methods, if components other than the nanoparticles 11 and the amphiphilic molecules 12 or organosilane molecules 13 (silane coupling agents) coating them are detected, these components can be considered to originate from the crosslinking portion 21, and it can be determined that a crosslinking portion 21 consisting of these components exists between the nanoparticles 11.

[0036] Furthermore, the number of nanoparticles 11 in close proximity to a single nanoparticle 11 is not necessarily limited to four or fewer. For example, if the simple average (arithmetic mean) of the number of nanoparticles 11 in close proximity to a single nanoparticle 11 within a single field of view is four or less, then a single field of view may contain a nanoparticle 11 in close proximity to five or more other nanoparticles 11.

[0037] (1-2. Method of manufacturing the structure) Figure 7 shows a flowchart of the manufacturing process for structure 1. Below, we will first describe the manufacturing method for structure 1, in which multiple nanoparticles 11, whose surfaces are coated with amphiphilic molecules 12, are linked together by crosslinking portions 21.

[0038] (Method for manufacturing a structure using multiple nanoparticles whose surfaces are coated with amphiphilic molecules) First, nanoparticles 11 (e.g., silica particles) are synthesized using a liquid-phase method (step S101). Generally, methods for producing silica nanoparticles are broadly classified into two types: gas-phase and liquid-phase methods. However, as described above, minute nanoparticles 11 with a diameter of 10 nm or less can be isolated without aggregation by using the liquid-phase method. As a precursor for the liquid-phase method, it is preferable to select a molecule represented by the following general formula (7) that can form a three-dimensional polysiloxane skeleton (Si-O-Si) through hydrolysis and condensation polymerization reactions. Examples of such precursors include water glass (sodium silicate) and alkoxysilane molecules. The alkoxysilane molecule may be a molecule in which some alkoxy groups are substituted with non-hydrolyzable functional groups, and this does not hinder the formation of the polysiloxane skeleton. (C7)R 6 Z Si(OR 7 ) 4-Z ...(7) (R 6R is one of the following groups: methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, dodecyl group, hexadecyl group, vinyl group, phenyl group, acryloxy group, methacryloxy group, aminopropyl group, glycidoxypropyl group, and mercaptopropyl group. 7 (where Z is one of the following: a hydrogen atom, a methyl group, an ethyl group, a propyl group, or an isopropyl group. Z is an integer less than or equal to 2.)

[0039] After dissolving the above precursor in water or an organic solvent, the acidity or basicity is adjusted. This causes a polymerization reaction to form silica particles. However, the manufacturing method is not limited to the above, as long as the diameter of the final nanoparticles 11 is 10 nm or less. The following are examples of references. For example, Reference 1 (T. Yokoi et al. Chem. Mater. 2009, 21, 3719-3729) reports the formation of 8 nm diameter nanoparticles in an aqueous solution in the presence of amino acids, and the nanoparticles can be isolated without aggregation by coating the surface with amino acid molecules. Reference 2 (S. Sakamoto et al. Langmuir 2018, 34, 1711-1717) reports the formation of 3 nm diameter nanoparticles using an inverse micelle-type liquid crystal phase as a template, and the nanoparticles can be isolated without aggregation by coating the surface with surfactant molecules.

[0040] Next, the nanoparticles 11 are dispersed in a solvent for surface modification (step S102). To the dispersion of nanoparticles 11, an amphiphilic molecule 12, such as a surfactant molecule, an amino acid molecule, or a polymer, is added. The added surfactant molecule, amino acid molecule, or polymer adsorbs onto the surface of the nanoparticles 11 and prevents aggregation of the nanoparticles. As described in references 1 and 2 above, depending on the manufacturing method, nanoparticles 11 whose surfaces are coated with surfactant molecules, amino acid molecules, or polymers can be obtained. In that case, the addition of the amphiphilic molecule 12 is omitted.

[0041] Next, the nanoparticles 11 are crosslinked using a crosslinking agent (silane compound) (step S103). A silane compound having two or more reaction sites is added as a crosslinking agent to a dispersion containing nanoparticles 11 whose surfaces are coated with amphiphilic molecules 12 such as surfactant molecules, amino acid molecules, or polymers. The amount of silane compound added is such that 1 to 4 nanoparticles 11 are bound to one nanoparticle 11. After adding the silane compound, the dispersion is heated as needed. As a result, the crosslinking reaction of the nanoparticles 11 proceeds in the dispersion, and a structure 1 having a three-dimensional structure is formed. The dispersion gradually loses its fluidity and becomes a gel.

[0042] Finally, the dispersion, now in a gel state, is dried to obtain structure 1 (step S104). Methods for removing the solvent and drying include, for example, drying at atmospheric pressure and increased temperature. If there is concern about the collapse of structure 1 due to interfacial tension during drying, it is preferable to use supercritical drying or freeze-drying. In this embodiment, the surface of the nanoparticles 11 (silica particles), which cause high interfacial tension, is inactivated by being coated with amphiphilic molecules 12. Therefore, compared to the case where the surface is not coated, structure 1 is less likely to collapse during drying. Thus, structure 1 shown in Figure 1 is obtained.

[0043] Next, we will describe a method for manufacturing a structure 1 in which multiple nanoparticles 11, each coated with an organic silane molecule 13, are linked together by a cross-linking portion 21.

[0044] (Method for manufacturing a structure using multiple nanoparticles whose surfaces are coated with organosilane molecules) First, nanoparticles 11 (e.g., silica particles) are synthesized using a liquid-phase method (step S101) in the same manner as the nanoparticles 11 whose surface is coated with amphiphilic molecules 12 as described above. Then, the nanoparticles 11 are dispersed in a solvent for surface modification (step S102). Here, instead of amphiphilic molecules 12, an organic silane molecule 13 (silane coupling agent) represented by general formula (1) or general formula (2) is added to the dispersion. After adding the silane coupling agent, heating is performed as needed to cause the nanoparticles 11 (silica particles) and the organic silane molecule 13 to react and form covalent bonds, thereby inactivating the surface of the nanoparticles 11 and preventing aggregation of the nanoparticles 11.

[0045] Next, the nanoparticles 11 are crosslinked using a crosslinking agent having two or more reactive functional groups (step S103). A silane compound such as the polyfunctional allyl (vinyl), polyfunctional thiol, polyfunctional (meth)acrylate, and polyfunctional glycidyl mentioned above is added as a crosslinking agent to a dispersion containing nanoparticles 11 whose surfaces are coated with organic silane molecules 13. After adding the silane compound, heating or light irradiation is performed as necessary. As a result, a crosslinking reaction proceeds with the organic functional groups of the organic silane molecules 13 in the dispersion, and a structure 1 having a three-dimensional structure is formed. The dispersion gradually loses its fluidity and becomes a gel state. If the crosslinking reaction is an organic reaction such as a radical reaction, cationic polymerization, or anionic polymerization, an appropriate reaction initiator may be added.

[0046] Finally, the gel-like dispersion is dried in the same manner as the nanoparticles 11 whose surfaces are coated with amphiphilic molecules 12 as described above, to obtain structure 1 (step S104). Thus, structure 1 shown in Figure 1 is obtained.

[0047] (1-3. Action and Effects) In the structure 1 of this embodiment, a plurality of nanoparticles 11 whose surfaces are coated with amphiphilic molecules 12 or organosilane molecules 13 are linked to each other via crosslinking portions 21. This prevents aggregation of the plurality of nanoparticles 11 and creates voids G between the linked plurality of nanoparticles 11. This will be explained below.

[0048] In buildings such as ordinary houses and offices, the majority of heat loss during heating and cooling occurs through openings such as glass windows. For example, during heating, heat loss through openings accounts for 48% of the total. During cooling, heat gain through openings accounts for 71% of the total. Methods to improve the insulation of openings such as glass windows include applying insulating films with a porous structure to the glass surface or sandwiching insulating material between double-glazed windows to improve insulation performance.

[0049] However, currently used thermal insulation materials have insufficient transparency, posing a significant challenge in terms of reducing transparency. Transparent thermal insulation materials currently in use are composed of aerogels, which form a porous structure by linking silica particles in a bead-like fashion. Typical aerogels have a bead-like framework about 10 nm wide and contain voids of several tens of nanometers, and light is scattered in aerogels depending on the thickness of the framework. The scattering intensity is proportional, for example, to the sixth power of the particle size.

[0050] Aerogels are manufactured, for example, as follows: First, a silica alkoxide precursor is dissolved in a solvent such as ethanol, and nanoparticles are grown by hydrolysis and condensation polymerization. Then, the nanoparticles are copolymerized to form a framework and gel. The resulting wet gel is then dried, for example by supercritical drying, to remove the solvent and obtain a porous aerogel. In the above manufacturing method, particle growth continues even during the framework formation and drying processes, causing the aerogel framework to thicken and reducing its transparency.

[0051] As an example of an insulating material designed to improve transparency, as mentioned above, an insulating sheet has been reported that uses a sheet-like structure in which hollow particles are linked together, with an average sheet pore diameter of 70 nm or less, a sheet porosity of 90-99% by volume, and a light transmittance of 85% or more, thereby improving not only transparency but also insulating performance and mechanical strength. However, while using hollow particles as constituent units is an effective means of improving insulating performance, it increases optical scattering, making it difficult to sufficiently improve transparency compared to conventional aerogels.

[0052] In contrast, the structure 1 of this embodiment coats the surface of the nanoparticles 11 with an amphiphilic molecule 12 or an organic silane molecule 13, and connects the nanoparticles 11 to each other via a crosslinking portion 21 made of, for example, a silane compound. This prevents aggregation of multiple nanoparticles 11. Furthermore, it is possible to form voids G between the connected multiple nanoparticles 11.

[0053] As described above, in this embodiment, multiple nanoparticles 11 whose surfaces are coated with amphiphilic molecules 12 or organic silane molecules 13 are linked to each other via crosslinking portions 21, thereby preventing aggregation of the multiple nanoparticles 11. Furthermore, voids G are formed between the linked multiple nanoparticles 11. Therefore, it is possible to realize a structure 1 that has high light transmittance while maintaining thermal insulation properties, and can be used, for example, as a thermal insulation material.

[0054] For example, when the structure 1 of this embodiment is attached to a glass window as described above, or sandwiched between double-glazed windows, it is possible to ensure high light transmittance while suppressing the heat balance of the glass window and improving heating and cooling efficiency, compared to using a general aerogel. Therefore, it is possible to achieve both a reduction in energy costs and an environmental contribution.

[0055] Furthermore, by using the structure 1 of this embodiment as an insulating material, it becomes possible to enhance the design of products that generally use opaque insulating materials, such as refrigerators and bathtubs.

[0056] Next, a modified example of the above embodiment will be described. In the following, components similar to those in the above embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0057] <2. Variant> Figure 8 schematically shows an example of the configuration of a modified structure (structure 1A) according to the present disclosure. Structure 1A, like structure 1 in the above embodiment, is used as an insulating material to reduce the heat balance of a window, for example, by being attached to a glass window or sandwiched between double-glazed windows. Structure 1A of this modified example differs from the above embodiment in that it uses multiple nanofibers 31 instead of multiple nanoparticles 11.

[0058] The nanofiber 31 is a fibrous material whose length is, for example, 100 times or more its diameter, and is, for example, a silica nanofiber. The average diameter (φ) of the nanofiber 31 is, for example, 10 nm or less, preferably 5 nm or less. Similar to the nanoparticles 11, the surface of the nanofiber 31 is coated with an amphiphilic molecule 12 or an organosilane molecule 13, and multiple nanofibers 31 cannot be covalently bonded to each other.

[0059] Multiple nanofibers 31 are connected to each other via crosslinking portions 21, similar to the embodiment described above. The length of the crosslinking portion 21 is preferably less than half (1 / 2) the diameter (φ) of the nanofiber 31. This prevents aggregation of multiple nanofibers 31 within the structure 1A.

[0060] Nanofiber 31 can form silica nanofibers with a diameter of 5 nm to 10 nm by using, for example, an inverse micelle-type liquid crystal phase as a template (Reference 3 (W.-C. Lai, L et al. J. Taiwan Inst. Chem. Eng. 2019, 99, 207-214)). Furthermore, nanofiber 31 can form twisted rod-shaped silica nanofibers by utilizing, for example, the self-assembly of aminopropyltrimethoxysilane (Reference 4 (Y. Kaneko et al. Chem. Mater. 2004, 16, 3417-3423)).

[0061] The above manufacturing method is merely one example, and is not limited to this method, as long as a nanofiber 31 with a diameter of 10 nm or less is ultimately obtained.

[0062] Surface modification of the nanofibers 31, crosslinking of the nanofibers 31 with a crosslinking agent, and drying can be performed using the same methods as described above for surface modification of the nanoparticles 11, crosslinking of the nanoparticles 11 with a crosslinking agent, and drying.

[0063] Although the structure 1A shown in Figure 8 is an example composed solely of nanofibers 31, it is not limited to this. For example, as shown in the structure 1B in Figure 9, nanoparticles 11 and nanofibers 31 may be mixed together. In this case as well, the nanoparticles 11 are connected to each other, the nanofibers 31 to each other, and the nanoparticles 11 and nanofibers 31 are connected via the crosslinking portion 21 described above.

[0064] As described above, in the modified structures 1A and 1B, some or all of the nanoparticles 11 are replaced with nanofibers 31, and the surface is coated with an amphiphilic molecule 12 or an organic silane molecule 13, so that the nanoparticles 11 and nanofibers 31 or the nanofibers 31 are linked to each other via a crosslinking portion 21 made of, for example, a silane compound. This prevents aggregation of multiple nanoparticles 11, multiple nanofibers 31, or nanoparticles 11 and nanofibers 31 that constitute structures 1A or 1B. Furthermore, gaps G can be formed between the linked multiple nanoparticles 11, multiple nanofibers 31, or between the nanoparticles 11 and nanofibers 31. Thus, the same effects as in the above embodiment can be obtained.

[0065] <3. Other application examples> The structure described in the above embodiments and modifications (for example, structure 1) can be used in automobile windows and the like if it has a transmittance of, for example, 70% or more. Furthermore, if structure 1 has a transmittance of, for example, 90% or more, it can be used as a substitute material for building windows, glass substrates, or plastics.

[0066] Figure 10 shows the transmittance at a wavelength of 550 nm when a structure 1 with a thickness of 1 mm is formed. For example, if the number of nearest nanoparticles 11 to one nanoparticle 11 among the multiple nanoparticles 11 constituting structure 1 is 4, then the 4 nanoparticles 11 in structure 1 take on a diamond structure (see Figure 6). In such a structure 1, the packing density of the nanoparticles 11 is 34 volume%, and as shown in Figure 10, if the primary particle diameter is 14 nm, structure 1 can obtain a transmittance of 70%. Furthermore, if the primary particle diameter is 9 nm, structure 1 can obtain a transmittance of 90%. On the other hand, if the number of nearest nanoparticles 11 to one nanoparticle 11 among the multiple nanoparticles 11 constituting structure 1 is less than 4, then the packing density of the nanoparticles 11 in structure 1 is less than 34 volume%. Therefore, similar to the case where the number of nearest nanoparticles 11 to one nanoparticle 11 is 4, if the primary particle diameter is 14 nm or less, structure 1 can obtain a transmittance of 70% or more. Furthermore, if the primary particle diameter is 9 nm or less, structure 1 can achieve a transmittance of 90% or more.

[0067] The present disclosure has been described above with reference to embodiments and modifications, but the present disclosure is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiments, silica particles were given as nanoparticles 11 and silica nanofibers as nanofibers 31 as examples, but the disclosure is not limited to these, and nanoparticles or nanofibers made of inorganic oxides, inorganic nitrides, inorganic carbides, or organic materials can also be used. Furthermore, the structure of the present disclosure (for example, structure 1) may be composed of multiple types of nanoparticles and / or nanofibers, for example, selected from the above materials as appropriate.

[0068] Furthermore, while the above embodiments mention application examples of structure 1 such as attachment to glass windows, placement between double-glazed windows, and insulation for refrigerators and bathtubs, the structure 1 of this disclosure may also be used as a functional component other than insulation in other electronic devices. For example, it can be used in applications similar to general porous materials, such as an adsorbent for odor components, bacteria, and viruses, a moisture absorber to maintain a constant humidity level in the air, and a sound absorber to hinder the propagation of sound waves. In addition, because it can be used in applications requiring transparency, it can be applied to structural materials for electronic devices such as photocatalysts, artificial photosynthesis devices, solar cells, and semiconductors, as well as materials for low dielectric constant films and anti-reflective films.

[0069] Furthermore, the effects described herein are merely illustrative and not limited to those described herein, and other effects may also occur.

[0070] Furthermore, this technology can also be configured as follows. According to this configuration, multiple nanoparticles or nanofibers whose surfaces are coated with amphiphilic molecules or organosilane molecules are linked to each other via crosslinking portions. This prevents aggregation of multiple nanoparticles or multiple nanofibers, and creates voids between the linked multiple nanoparticles or multiple nanofibers. Therefore, it is possible to improve light transmittance while maintaining thermal insulation. (1) Multiple nanoparticles or nanofibers whose surfaces are coated with amphiphilic molecules or organosilane molecules, A crosslinking portion that connects the plurality of nanoparticles or the plurality of nanofibers to each other Equipped with, The aforementioned nanoparticles or nanofibers and the crosslinked portion form a covalent bond. A structure equipped with [something]. (2 ) before The (1) comprises both a plurality of nanoparticles and a plurality of nanofibers, wherein in some cases the nanoparticles and the nanofibers are connected via the crosslinking portion. ) The structure described. (3) The average number of nanoparticles in contact with a single nanoparticle is between 1 and 4. (1) or (2) above The structure described above. (4) The aforementioned one nanoparticle and the nanoparticle in nearest contact with the aforementioned one nanoparticle are connected via the crosslinking portion. (3) above The structure described above. (5) The length of the crosslinked portion is less than half the average particle diameter of the plurality of nanoparticles. The above (1) to (4) A structure described in any one of the following. (6) The length of the crosslinked portion is less than half the average diameter of the plurality of nanofibers. The above (1) to (5) A structure described in any one of the following. (7) The aforementioned amphiphilic molecule is a surfactant molecule, an amino acid molecule, or a polymer. The above (1) to (6) A structure described in any one of the following. (8) The polymer is a block copolymer of phospholipids or polyalkylene glycols. (7) The structure described above. (9) The crosslinked portion is an organic or inorganic material that is directly covalently bonded to the nanoparticles or nanofibers. The above (1) through (8) A structure described in any one of the following. (10) The crosslinked portion is an organic or inorganic substance that is covalently bonded to the nanoparticles or nanofibers via silyl groups. The above (1) through (8) A structure described in any one of the following. (11) The average particle size of the aforementioned plurality of nanoparticles is 14 nm or less. The above (1) to (10) A structure described in any one of the following. (12) The average particle size of the aforementioned plurality of nanoparticles is 9 nm or less. The above (1) to (10)A structure described in any one of the following. (13) The average diameter of the aforementioned multiple nanofibers is 10 nm or less. The above (1) to (12) A structure described in any one of the following. (14) Amphiphilic molecules or organosilane molecules are added to a dispersion in which multiple nanoparticles or multiple nanofibers are dispersed, thereby coating the surface of the multiple nanoparticles or multiple nanofibers. Furthermore, a crosslinking agent is added to connect the multiple nanoparticles or the multiple nanofibers to each other via the crosslinked portion made of the crosslinking agent. death, The aforementioned nanoparticles or nanofibers and the crosslinked portion form a covalent bond. A method for manufacturing a structure. (15) Multiple nanoparticles or nanofibers whose surfaces are coated with amphiphilic molecules or organosilane molecules, The structure includes a plurality of nanoparticles or a crosslinking portion that connects the plurality of nanofibers to each other. 、 The aforementioned nanoparticles or nanofibers and the crosslinked portion form a covalent bond. Insulation material.

[0071] This application claims priority based on Japanese Patent Application No. 2021-009119, filed with the Japan Patent Office on 22 January 2021, and all contents of that application are incorporated herein by reference.

[0072] Those skilled in the art will understand that various modifications, combinations, subcombinations, and changes can be conceived depending on design requirements and other factors, and that these fall within the scope of the attached claims and their equivalents.

Claims

1. Multiple nanoparticles or nanofibers whose surfaces are coated with amphiphilic molecules or organosilane molecules, The system comprises a plurality of nanoparticles or a crosslinking portion that connects the plurality of nanofibers to each other, The aforementioned nanoparticles or nanofibers and the crosslinked portion form a covalent bond. structure.

2. The structure according to claim 1, comprising both the plurality of nanoparticles and the plurality of nanofibers, wherein in some cases the nanoparticles and the nanofibers are connected via the crosslinking portion.

3. The structure according to claim 1, wherein the average number of nanoparticles in contact with a single nanoparticle is 1 or more and 4 or less.

4. The structure according to claim 3, wherein one nanoparticle and the nanoparticle in nearest contact with the one nanoparticle are connected via the crosslinking portion.

5. The structure according to claim 1, wherein the length of the crosslinked portion is less than half the average particle diameter of the plurality of nanoparticles.

6. The structure according to claim 1, wherein the length of the crosslinked portion is less than half the average diameter of the plurality of nanofibers.

7. The structure according to claim 1, wherein the amphiphilic molecule is a surfactant molecule, an amino acid molecule, or a polymer.

8. The structure according to claim 7, wherein the polymer is a block copolymer of a phospholipid or a polyalkylene glycol.

9. The structure according to claim 1, wherein the crosslinked portion is an organic or inorganic material that is directly covalently bonded with the nanoparticles or nanofibers.

10. The structure according to claim 1, wherein the crosslinked portion is an organic or inorganic material that is covalently bonded to the nanoparticles or nanofibers via silyl groups.

11. The structure according to claim 1, wherein the average particle size of the plurality of nanoparticles is 14 nm or less.

12. The structure according to claim 1, wherein the average particle size of the plurality of nanoparticles is 9 nm or less.

13. The structure according to claim 1, wherein the average diameter of the plurality of nanofibers is 10 nm or less.

14. Amphiphilic molecules or organosilane molecules are added to a dispersion in which multiple nanoparticles or multiple nanofibers are dispersed, thereby coating the surface of the multiple nanoparticles or multiple nanofibers. Furthermore, a crosslinking agent is added to connect the plurality of nanoparticles or the plurality of nanofibers to each other via the crosslinking portion made of the crosslinking agent. The aforementioned nanoparticles or nanofibers and the crosslinked portion form a covalent bond. A method for manufacturing a structure.

15. Multiple nanoparticles or nanofibers whose surfaces are coated with amphiphilic molecules or organosilane molecules, The structure includes a plurality of nanoparticles or a crosslinking portion that connects the plurality of nanofibers to each other, The aforementioned nanoparticles or nanofibers and the crosslinked portion form a covalent bond. Insulation material.

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