High heat-dissipating, highly flexible, and high-toughness nanocomposite and method for producing the same

Abstract

To provide an organic-inorganic nanocomposite that exhibits anisotropic high thermal conductivity, superior mechanical characteristics, and high insulation.SOLUTION: An organic-inorganic nanocomposite comprises at least one polyrotaxane or a polymer blend including at least one polyrotaxane, and an inorganic filler that has been plasma-treated, wherein the organic-inorganic nanocomposite contains the inorganic filler in an amount of 30 vol.% or more, the inorganic filler is a two-dimensional material and serves as an insulating filler having thermal anisotropy, and the inorganic filler is oriented with an orientation degree of at least 3 in relation to the thickness direction of the organic-inorganic nanocomposite.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an organic-inorganic nanocomposite comprising a polymer containing a slide-ring polymer and an inorganic filler. More specifically, the invention relates to an organic-inorganic nanocomposite containing anisotropically thermally conductive and insulating inorganic particles as the inorganic filler, and having high anisotropic thermal conductivity, mechanical toughness, and flexibility. [Background technology]

[0002] With the spread of electric vehicles and the development of flexible equipment that comes into contact with the body, such as body monitoring and assistive devices, thermal countermeasures for the electrical circuits at the heart of the device have become recognized as an urgent issue in order to prevent thermal runaway and thermal degradation of surrounding components. Thermal interlayer materials (TIM) such as heat dissipation sheets are used in the substrates of flexible electronics as one way of dealing with heat, and materials with advanced mechanical properties such as flexibility and toughness, as well as functions such as directional thermal conductivity and insulation, are required.

[0003] The heat dissipation ability of a material is determined by its thermal conductivity as well as its shape and thickness. For example, heat dissipation can be improved by making the material thinner, but there is a limit to how thin the material can be in order to maintain mechanical strength. Therefore, a material that has a certain degree of strength, is flexible, and has high thermal conductivity is required.

[0004] Patent Document 1 provides a material that combines the mechanical properties of polymers, such as flexibility and abrasion resistance, with the functionality of inorganic fillers, such as thermal conductivity, even at high filler concentrations. Specifically, it discloses a composite material in which inorganic fillers with one-dimensional structures and varying sizes that have been plasma-treated are dispersed at 50 wt% or more in a slide-ring polymer (polyrotaxane) or a polymer blend containing the slide-ring polymer, and the highly dispersed one-dimensional inorganic fillers are oriented in the heat dissipation direction. The composite material disclosed in Patent Document 1 has thermal directivity limited to the in-plane direction of the composite material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7307940 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an organic-inorganic nanocomposite having directional high thermal conductivity, excellent mechanical properties, and high insulating properties. [Means for solving the problem]

[0007] The present inventors have previously succeeded in developing the organic-inorganic nanocomposite disclosed in Patent Document 1, which is an organic-inorganic nanocomposite that combines the mechanical properties of a polymer, such as flexibility and abrasion resistance, with the functionality of an inorganic filler, such as thermal conductivity, even at a high filler concentration. As a result of extensive research, the present inventors used an insulating filler, which is a two-dimensional material with thermal anisotropy, as the inorganic filler, and further crosslinked the organic-inorganic nanocomposite under a high electric field strength using a bipolar pulse power supply. As a result, they succeeded in producing a nanocomposite that has high directional thermal conductivity in the direction perpendicular to the surface of the organic-inorganic nanocomposite, as well as high mechanical properties and high insulating properties. The present invention has been completed based on the above findings and includes the following aspects:

[0008] One aspect of the present invention is [1] An organic-inorganic nanocomposite comprising one or more types of polyrotaxane or a polymer blend containing one or more types of polyrotaxane and a plasma-treated inorganic filler, The organic-inorganic nanocomposite contains the inorganic filler in an amount of 30 vol% or more, the inorganic filler is a two-dimensional material and an insulating filler having thermal anisotropy; the inorganic filler is oriented with an orientation degree of 3 or more in the direction perpendicular to the surface of the organic-inorganic nanocomposite; This paper deals with organic-inorganic nanocomposites. Here, the organic-inorganic nanocomposite of the present invention is, in one embodiment, [2] The organic-inorganic composite according to [1] above, The organic-inorganic nanocomposite is characterized in that the thermal orientation is 1 or more.

[0009] In one embodiment, the organic-inorganic nanocomposite of the present invention comprises [3] The organic-inorganic nanocomposite according to [1] or [2] above, It is characterized by having a Young's modulus of 200 MPa or less. In one embodiment, the organic-inorganic nanocomposite of the present invention comprises [4] The organic-inorganic nanocomposite according to any one of [1] to [3] above, The organic-inorganic nanocomposite has a thermal conductivity of 3 W / mK or more in the direction perpendicular to the surface. In one embodiment, the organic-inorganic nanocomposite of the present invention comprises [5] The organic-inorganic nanocomposite according to any one of [1] to [4] above, Electrical resistivity is 1.00 x 10 10 The present invention is characterized in that:

[0010] In one embodiment, the organic-inorganic nanocomposite of the present invention comprises [6] The organic-inorganic nanocomposite according to any one of [1] to [5] above, The inorganic filler is hexagonal boron nitride. In one embodiment, the organic-inorganic nanocomposite of the present invention comprises [7] The organic-inorganic nanocomposite according to any one of [1] to [6] above, The inorganic filler has an average particle size of 0.01 to 100 μm. In one embodiment, the organic-inorganic nanocomposite of the present invention comprises [8] The organic-inorganic nanocomposite according to any one of [1] to [7] above, The inorganic filler is characterized in that it contains two types of inorganic fibers with different sizes.

[0011] [9] The organic-inorganic nanocomposite according to any one of [1] to [8] above, The ratio of the large-diameter inorganic filler to the small-diameter inorganic filler is 10:0 to 5:5. In one embodiment, the organic-inorganic nanocomposite of the present invention comprises

[10] The organic-inorganic nanocomposite according to any one of [1] to [9] above, characterized in that the large-diameter inorganic filler has an average particle size of 1 to 50 μm, and the small-diameter inorganic filler has an average particle size of 0.05 to 1 μm. In one embodiment, the organic-inorganic nanocomposite of the present invention comprises

[11] The organic-inorganic nanocomposite according to any one of [1] to

[10] above, It is characterized by the fact that the pulley molecules of the polyrotaxane are chemically modified.

[0012] In another aspect, the present invention provides

[12] A method for producing the organic-inorganic nanocomposite according to any one of [1] to

[11] above, The present invention relates to a method for producing the nanocomposite described in claim 1, characterized in that one or more types of polyrotaxane or a polymer blend containing one or more types of polyrotaxane, a crosslinking agent, and a catalyst for a crosslinking reaction are dissolved in a solvent, the solution in which the inorganic filler is dispersed is subjected to a crosslinking reaction under the application of a high electric field by a bipolar pulse, and then the solvent is removed.

[0013] In another aspect, the present invention provides

[12] An organic-inorganic nanocomposite obtained by a method for producing an organic-inorganic nanocomposite, the method comprising the steps of dissolving one or more types of polyrotaxane or a polymer blend containing one or more types of polyrotaxane, a crosslinking agent, and a catalyst for a crosslinking reaction in a solvent, dispersing the inorganic filler in the solution, and then crosslinking the solution under the application of a high electric field by a bipolar pulse, followed by removing the solvent. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an organic-inorganic nanocomposite having high mechanical properties, high insulating properties, and high directional thermal conductivity. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows a schematic diagram of the electrode circuit used to prepare an organic-inorganic nanocomposite in Example 1 below, a schematic diagram of the application of an electric field during a crosslinking reaction, and a photograph of the nanocomposite to which an electric field was applied. [Figure 2] Figure 2 shows the results of X-ray CT measurements of an organic-inorganic nanocomposite performed in Example 2 below. Figure 2 shows cross-sectional X-ray CT images of the nanocomposite with (a) an applied electric field and without (b) an applied electric field. [Figure 3] Figure 3 shows the results of the evaluation of the degree of orientation of the organic-inorganic nanocomposite by XRD measurement performed in Example 2 below. Figure 3(a) shows the XRD pattern of the nanocomposite surface (black without an applied electric field, gray with an applied electric field). Figure 3(b) shows the peak intensity ratio η and expected particle number ratio R of the hBN (100) plane oriented along the applied electric field to the hBN (200) plane oriented perpendicular to the applied electric field, using the XRD spectra of the nanocomposite without and with an applied electric field. [Figure 4] Figure 4 shows the results of the evaluation of the degree of orientation of the organic-inorganic nanocomposite by FE-SEM measurement performed in Example 2 below. The images show FE-SEM images of the cross section (ab) and surface (cd) of the nanocomposite with an applied electric field, and the cross section (ef) and surface (gh) of the nanocomposite without an applied electric field. Images (b), (d), (f), and (h) are enlarged images of (a), (c), (e), and (g), respectively. [Figure 5] FIG. 5 shows the out-of-plane thermal conductivity (a) and in-plane Young's modulus (b) of the nanocomposite without and with an applied electric field versus the filler hBN diameter d, as measured in Example 2 below. [Figure 6]Figure 6 shows cross-sectional X-ray CT images of a nanocomposite containing two types of hBN fillers without (left) and with (right) an applied electric field, as measured in Example 3 below, and the results of two-dimensional fast Fourier transform. [Figure 7] Figure 7 shows the XRD patterns (left, without applied electric field; right, with applied electric field) of the nanocomposite surface containing two types of hBN fillers, measured in Example 3 below. It also shows the peak intensity ratio η of the hBN (100) plane oriented along the applied electric field to the hBN (200) plane oriented perpendicular to the applied electric field, and the expected particle number ratio R, obtained using the XRD spectra of the nanocomposites without and with applied electric field. [Figure 8] Figure 8 shows the thermal conductivity in the in-plane and perpendicular directions of the nanocomposite without (left) and with (right) an applied electric field, which was measured in Example 3 below, in which two types of hBN fillers were mixed. [Figure 9] FIG. 9 shows the thermal conductivity in the perpendicular direction and Young's modulus in the in-plane direction of the nanocomposite with an applied electric field as a function of the content of the micro-sized hBN filler measured in Example 4 below. [Figure 10] FIG. 10 shows the peak intensity ratio η and expected number ratio R for the hBN content of the nanocomposite of the present invention with an applied electric field measured in Example 4 below and the nanocomposite disclosed in the prior art (wt% was calculated from vol%, and the densities of hBN and polysiloxane were calculated using values ​​of 2.3 and 0.97, respectively). [Figure 11] FIG. 11 shows (a) the in-plane Young's modulus and (b) the perpendicular thermal conductivity versus the hBN content of nanocomposites containing two types of hBN fillers when an electric field is applied, as measured in Example 4 below. [Figure 12] FIG. 12 shows the Young's modulus and thermal conductivity of the composite according to the present invention without (black circles) and with (red circles) an applied electric field. DETAILED DESCRIPTION OF THE INVENTION

[0016] One aspect of the present invention is an organic-inorganic nanocomposite comprising one or more polyrotaxanes or a polymer blend containing one or more polyrotaxanes and a plasma-treated inorganic filler, The organic-inorganic nanocomposite contains the inorganic filler in an amount of 30 vol% or more, the inorganic filler is a two-dimensional material and an insulating filler having thermal anisotropy; The organic-inorganic nanocomposite is provided in which the inorganic filler is oriented with an orientation degree of 3 or more in the direction perpendicular to the surface of the organic-inorganic nanocomposite.

[0017] [Polymers and Slide-Ring Polymers] The polymer constituting the organic-inorganic nanocomposite of the present invention is a polyrotaxane or a mixed polymer of a polyrotaxane with one or more general-purpose polymers (referred to as a polyrotaxane blend polymer).

[0018] A "polyrotaxane" is a molecular assembly having a structure in which a rod-shaped molecule (axis molecule) passes through the hole of a cyclic pulley molecule (ring-shaped molecule), and bulky moieties (end groups) are attached to both ends of the rod-shaped molecule. The cyclic molecule can move freely on the linear polymer. In the present invention, there are no particular limitations on such polyrotaxane, and conventionally known polyrotaxanes can be used. Furthermore, by cross-linking the cyclic molecules between polyrotaxane molecules, a gel or elastomer can be produced (referred to as a slide-ring gel or slide-ring elastomer). Slide-ring elastomers have higher breaking elongation and toughness than fixed-crosslinked elastomers, and are preferable because they can impart these properties to organic-inorganic nanocomposites. Furthermore, while fixed-crosslinked elastomers gradually break down from the location of the shortest cross-linked portion, slide-ring-ring elastomers avoid this, and therefore their mechanical properties are less likely to change even when repeatedly stretched. In a preferred embodiment, the polyrotaxane is one in which the cyclic molecules between polyrotaxane molecules are cross-linked.

[0019] The cyclic pulley molecule is not particularly limited, and examples thereof include cyclodextrins (e.g., α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin), crown ethers, cyclophanes, calixarenes, cucurbiturils, and cyclic amides. These ring-shaped molecules may be used alone or in combination of two or more. Furthermore, such ring-shaped molecules may have a substituent or a side chain. The properties of polyrotaxanes, such as solubility in solvents, can be adjusted by chemically modifying the pulley molecules. Among these cyclic pulley molecules, cyclodextrins having caprolactone chains as graft chains are preferred from the viewpoint of obtaining appropriate flexibility.

[0020] The axial molecule is not particularly limited, and examples thereof include polyethylene glycol, polypropylene glycol, polyethylene, polypropylene, polyisoprene, polyisobutylene, polybutadiene, polylactic acid, polytetrahydrofuran, polydimethylsiloxane, polyvinyl alcohol, and polyvinyl methyl ether. These axial molecules may be used alone or in combination of two or more. Among these axial molecules, polyethylene glycol and polypropylene glycol are preferred because they have a low glass transition temperature and allow the ring-shaped molecule to move smoothly.

[0021] The combination of the cyclic pulley molecule and the axis molecule is not limited, and may be any combination of the pulley molecule and the axis molecule listed above. In a preferred embodiment, the combination of the cyclic pulley molecule and the axis molecule may be a combination of α-cyclodextrin (α-CD) and polyethylene glycol (PEG), a combination of crown ether and secondary ammonium salt, etc.

[0022] The content of polyrotaxane in the polyrotaxane blend polymer can be 0.1 to 100 wt %. The other general-purpose polymers contained in the "polyrotaxane blend polymer" are not particularly limited, and conventionally known general-purpose polymers can be used. Examples include, but are not limited to, silicone (polysiloxane), epoxy resin, etc.

[0023] The polyrotaxane content in the organic-inorganic nanocomposite of the present invention can be 5 to 95 wt%. If the polyrotaxane content is less than 5 wt%, the mechanical properties as a polymer will decrease, which is not preferred. If the polyrotaxane content exceeds 90 wt%, it will be difficult to obtain improvement in thermal conductivity due to the filler, which is also not preferred. The polyrotaxane content is preferably 20 to 90 wt%, and more preferably 35 to 70 wt%.

[0024] [Inorganic filler] The inorganic filler used in the present invention is a two-dimensional material. The use of a "two-dimensional" inorganic filler is advantageous in the following respects: 1) it can provide anisotropy in thermal conductivity in the thickness direction and longitudinal direction due to the filler's crystalline structure, 2) two-dimensional materials can connect thermal conduction paths across their surfaces (while maintaining thermal anisotropy), making it easy to connect thermal conduction paths over a wide range and over long distances, and 3) the arrangement of plate-like two-dimensional filler materials in an organic-inorganic nanocomposite reduces contact resistance with the polymer and improves mechanical properties.

[0025] The inorganic filler used in the present invention has thermal anisotropy. An inorganic filler having thermal anisotropy means that the thermal conductivity varies depending on the direction in the inorganic filler. The inorganic filler has thermal anisotropy in at least two directions. For example, an inorganic filler, which is a two-dimensional material, has thermal anisotropy in two directions: a direction perpendicular to the plane of the inorganic filler and a direction parallel to the plane (in-plane direction). The inorganic filler used in the present invention preferably has high thermal conductivity in one direction and relatively low thermal conductivity in another direction. The direction in which the high or low thermal conductivity is present is not limited. In one embodiment, the inorganic filler has high thermal conductivity in the in-plane direction and relatively low thermal conductivity in the perpendicular direction.

[0026] The inorganic filler that can be used in the present invention is not limited as long as it has the above-mentioned properties, and examples thereof include hexagonal boron nitride and graphite.

[0027] The inorganic filler preferably has a characteristic length of submicrometers or less. The characteristic length of each particle shape is measured in the longitudinal direction of the two-dimensional particle surface. Although not limited to the following, the length of the inorganic filler is preferably within the range of an average particle size of 0.05 to 100 μm, more preferably within the range of 1 to 10 μm. If it is less than 50 nm, the number of particles required to form a heat conduction path increases, making it difficult to improve thermal conductivity, which is undesirable. If it exceeds 100 μm, the particles are large, making it difficult to orient them using an electric field, etc., which is undesirable. The average particle size is the average particle size (D 50 ) value.

[0028] The inorganic filler constituting the organic-inorganic nanocomposite is oriented with an orientation degree of 3 or more in the direction perpendicular to the plane of the organic-inorganic nanocomposite. In this specification, the orientation degree can be calculated by XRD measurement. From the spectrum obtained by XRD measurement, the expected number of particles is calculated from the peaks corresponding to particles oriented in the in-plane direction of the organic-inorganic nanocomposite and the peaks corresponding to particles oriented in the direction perpendicular to the plane of the organic-inorganic nanocomposite. The orientation degree value can be calculated from the ratio of the expected number of particles oriented in the direction perpendicular to the plane of the organic-inorganic nanocomposite to the expected number of particles oriented in the in-plane direction of the organic-inorganic nanocomposite. When the degree of orientation of the inorganic filler is 3 or more, the faces with high thermal conductivity are aligned in one direction, making it possible to produce a nanocomposite with high thermal conductivity in the aligned direction, which is preferable. The degree of orientation of the inorganic filler is more preferably 10 or more, and even more preferably 50 or more.

[0029] In one embodiment, the organic-inorganic nanocomposite of the present invention contains two inorganic fillers of different sizes. In this case, the length of the large-diameter filler is preferably within the range of 1 to 50 μm, more preferably within the range of 3 to 10 μm. The length of the small-diameter filler is preferably within the range of 0.05 to 1 μm, more preferably within the range of 0.1 to 0.5 μm. The weight ratio of large-diameter filler to small-diameter filler contained in the organic-inorganic nanocomposite of the present invention is preferably within the range of 10:0 to 5:5. If the amount of small-diameter filler is greater than the above ratio, the average particle size becomes smaller, which is undesirable because it reduces the thermal conductivity. A more preferable ratio is within the range of 9.5:0.5 to 7:3.

[0030] The surface condition of the inorganic filler may be hydrophilized appropriately to promote chemical bonding with the cyclic molecules in the polyrotaxane polymer, and then particles modified with functional groups (hydroxyl groups, carboxyl groups, amine groups) may be used.

[0031] The inorganic filler may be in the form of a dispersion, a slurry, or a dry powder, with the dry powder being preferred as it does not require a solvent removal process.

[0032] [Plasma treatment] In the present invention, it is desirable to subject the inorganic filler to plasma treatment before blending it with the polyrotaxane or the polymer blend containing the polyrotaxane. The plasma treatment is preferably an aqua plasma treatment, which is carried out on an aqueous solution in which an inorganic filler is dispersed. The concentration of the inorganic filler in the plasma treatment solution is 10 wt % or less, and preferably 1 to 5 wt %. The plasma treatment time is 0.5 to 3 hours, and no time effect is observed with long treatment times. 1 hour is preferable.

[0033] The pulse frequency of the plasma treatment is 10 to 100 kHz, and 80 kHz is preferable.

[0034] The voltage applied in the plasma treatment is 1 to 10 kV, and 1.5 kV is preferable.

[0035] The pulse width of the plasma treatment is 0.1 to 4 μs, and 0.75 μs is preferable.

[0036] The plasma-treated solution is preferably prepared by adding hydroquinone to water to hydrophilize the surface and improve dispersibility. The concentration of hydroquinone in the plasma-treated water can be set within the range of 0.01 to 10 wt %, for example.

[0037] [Mixing method] The polyrotaxane or the blend polymer containing the polyrotaxane and the inorganic filler are preferably mixed using a polar organic solvent capable of dissolving and dispersing the polymer, the crosslinking agent, and the catalyst for the crosslinking reaction. As the organic solvent, toluene, acetone, and dimethyl sulfoxide can be used.

[0038] The cross-linking agent may be hexamethylene diisocyanate (HMDI) or 4,4-methylene diphenyl diisocyanate, and the concentration of the cross-linking agent may be 0.01 to 10 wt %. As a catalyst for the crosslinking reaction, dibutyltin(IV) dilaurate (DBTDL) or triethylenediamine can be used, and the concentration of the catalyst can be set to 0.01 to 10 wt %.

[0039] The kneading method can be a rotation-revolution kneading method, but a vacuum centrifuge method is preferred to suppress the generation of bubbles.

[0040] The inorganic filler is added so that its content in the resulting organic-inorganic nanocomposite is 30 vol% or more. A content of the inorganic filler in the organic-inorganic nanocomposite of 30 vol% or more is preferable because the increased filler content improves the thermal conductivity of the nanocomposite. Furthermore, the inorganic filler concentration in the organic-inorganic nanocomposite is preferably 60 vol% or less. A content of the inorganic filler exceeding 60 vol% is not preferable because the orientation effect is not sufficiently achieved. The content of the inorganic filler can be adjusted appropriately depending on the desired mechanical properties and thermal conductivity. In one embodiment, the content of the inorganic filler in the organic-inorganic nanocomposite is 40 vol% or more, 45 vol% or more, 50 vol% or more, or 55 vol% or more. Increasing the content of the inorganic filler can enhance the effect of directional improvement in the thermal conductivity of the organic-inorganic nanocomposite.

[0041] [Application of electric field] The voltage application can be carried out by applying a bipolar pulse electric field to the kneaded solution during composite crosslinking. The frequency is preferably 0.01 kHz to 100 kHz, more preferably 0.1 kHz to 10 kHz. The electric field strength is preferably an AC electric field of 10 kV / cm or more, more preferably 50 kV / cm or more. Insulating fillers are difficult to polarize in an electric field, so orientation takes time. Meanwhile, heat generated by dielectric loss due to the electric field causes the inorganic filler to gel, turning it into rubber without being aligned. By using a bipolar pulsed electric field power supply, the maximum electric field strength can be significantly increased (e.g., 10, 20, 30, 40, or 50 times or more) compared to conventional AC electrodes. This increases the orientation speed of the inorganic filler, reduces dielectric loss, and suppresses heat generation, allowing the insulating filler to be oriented to the desired degree.

[0042] [Solvent removal and drying] After kneading in a solvent, applying an electric field, and crosslinking, the composite can be dipped or coated, and then the solvent can be removed to obtain an elastomer. The temperature for solvent removal is between room temperature and approximately 105°C, with 105°C being preferred. Vacuum drying is also effective. Drying by hot pressing is also effective.

[0043] [Organic-inorganic nanocomposite] The organic-inorganic nanocomposite has thermal directionality. In this specification, the thermal directionality can be calculated by the ratio of "high thermal conductivity in a first direction within the nanocomposite" to "relatively low thermal conductivity in a second direction within the nanocomposite." The thermal directionality in the present invention can be calculated by the ratio of "thermal conductivity in the direction perpendicular to the surface of the nanocomposite" to "thermal conductivity in the in-plane direction of the nanocomposite." The thermal directivity of the organic-inorganic nanocomposite is 1 or more, preferably 3 or more, and more preferably 5 or more. When the thermal directivity of the organic-inorganic nanocomposite is 3 or more, it is possible to selectively dissipate heat in a desired direction, which is preferable.

[0044] The high thermal conductivity in the first direction within the nanocomposite is 3 W / mK or more, preferably 4 W / mK or more, more preferably 6 W / mK or more, and even more preferably 10 W / mK or more.

[0045] The Young's modulus of the organic-inorganic nanocomposite can be measured under the same conditions as those described in the Examples below. The Young's modulus of the organic-inorganic nanocomposite is 200 MPa or less, preferably 100 MPa or less, and more preferably 50 MPa or less. A Young's modulus of 100 MPa or less is preferred because it results in a flexible nanocomposite.

[0046] The electrical resistivity of the organic-inorganic nanocomposite can be measured under the same conditions as those described in the following examples. The electrical resistivity of the organic-inorganic nanocomposite is 1.00×10 10 or more, preferably 5.00 × 10 10 More preferably, it is 1.00×1011 The electrical resistivity is 1.00×10 10 If the above condition is met, it can be used for circuit boards and the like, which is preferable. [Example]

[0047] (Example 1. Preparation of organic-inorganic nanocomposite 1) 1-1. Plasma treatment of inorganic filler For the plasma surface modification, a solution of inorganic filler dispersed in water was stirred and dispersed using a dispersing device that utilizes cavitation (Nihon Spindle Manufacturing Co., Ltd.), while a bipolar pulse power supply (Kurita Manufacturing, HPP-HV04) was used as the power source for plasma generation to apply an electric field between the electrodes to generate in-liquid plasma, thereby performing in-liquid plasma surface modification. In this example, similar to the previous paper (Inoue K. et al., J Phys Appl Phy;54:425202 (2021)), tungsten electrodes with a diameter of 1 mm and facing each other with a 1 mm gap between the electrodes were used, and in-liquid plasma surface modification was performed using the device shown in Figure 1. An aqueous hydroquinone solution was used for the in-liquid plasma surface modification. The plasma generation conditions are listed in the table below. [Table 1]

[0048] The inorganic filler used was hexagonal boron nitride (hBN), with an average particle size of approximately 200 nm from Sigma-Aldrich, Ltd., and average particle sizes of approximately 5 μm, 7 μm, 18 μm, and 30 μm from Denka Co. Ltd. Samples were prepared using hBN whose surface had been modified using plasma in a hydroquinone aqueous solution, and their properties were evaluated. The procedure for preparing surface-modified hBN was similar to that used in a previous study (Inoue K. et al., J Phys Appl Phys;54:425202 (2021)). 5 g of untreated hBN (rBN) and 10 g of hydroquinone were dispersed in 1000 mL of pure water, which was then subjected to in-liquid plasma surface modification. The supernatant, containing the hBN that remained dispersed even after standing overnight, was filtered. This particularly highly dispersible hBN was then dried and used as the hBN.

[0049] 1-2. Preparation of organic-inorganic nanocomposites The organic-inorganic nanocomposites were prepared using polycaprolactone-modified polyrotaxane (PCL-g-PR; SH2400, Advanced Soft Materials Inc.) as the polymer and plasma-treated hBN (average particle size approximately 200 nm; Sigma-Aldrich, Ltd.; 5 μm, 7 μm, 18 μm, or 30 μm; Denka Co. Ltd.) as the filler. Toluene was used as the solvent to dissolve the PCL-g-PR and disperse the hBN, dibutyltin dilaurate (DBTDL) as the catalyst, and hexamethylene diisocyanate (HMDI) as the crosslinker. Table 2 shows the mixing ratios of the suspensions used to prepare the organic-inorganic nanocomposites (when the total amount of hBN is 50 wt% of the total sample weight excluding the solvent). [Table 2]

[0050] The organic-inorganic nanocomposite was specifically prepared as follows. First, 0.65 g of hBN was thoroughly dispersed in 4 mL of toluene. Next, 0.65 g of polyrotaxane was dissolved in the solution and thoroughly stirred. After thorough stirring, 40 μL of DBTDL and 40 μL of HMDI were added, and after stirring for 1 minute, the mixture was poured into a mold (4 cm x 7 cm) inside a Teflon (registered trademark) sheet for the electrode shown in Figure 1. As crosslinking in the suspension progressed, an electric field for electric field orientation, described below, was applied. The hBN content in the resulting organic-inorganic nanocomposite was 33 vol%.

[0051] 1-3. Electric field alignment treatment The circuit diagram of the electrodes used for electric field orientation is shown in Figure 1. As shown in Figure 1, copper tape was attached to two glass plates, and polyimide tape was attached on top of that. A Teflon sheet (1 mm thick, 28 cm in the center) was placed between the glass plates. 2 A nanocomposite nanoparticle (having a hole with an area of ​​1 mm) sandwiched between two glass plates facing each other was used as the electrodes. To apply an electric field, a Teflon sheet was placed on the first glass plate, and then an appropriate amount of the suspension for nanocomposite production was poured into the mold inside the Teflon sheet, which was then sandwiched between the second glass plate, after which an electric field was applied. As the Teflon sheet was 1 mm thick, the value of the applied voltage (unit: V) was the same as the value of the electric field (unit: V / mm). A bipolar pulse power supply (HPP-HV04, Kurita Manufacturing) was used as the power source for the electrodes, and electric field orientation was attempted by applying a bipolar pulse voltage. In addition, to prevent excessive current from flowing when the electric field was applied, a 680 Ω resistor (HS300 680R J, Arcol) was connected in series with the electrodes during the experiment. After application of the electric field, the mixture was dried in a vacuum at 120°C for 1 hour to obtain an organic-inorganic nanocomposite.

[0052] Example 2: Characterization 2-1. Orientation evaluation (X-ray CT) In this example, the internal structure of the organic-inorganic nanocomposite obtained in Example 1 above was evaluated by X-ray CT. X-ray CT measurements were performed using a μX-ray computed tomography (μX-CT; Skyscan 1272, Bruker). The X-ray source voltage was 30 kV, the current was 80 μA, and the scanning resolution was 0.6 μm / pixel. For comparison, the internal structure of an organic-inorganic nanocomposite prepared without applying an electric field was also measured by X-ray CT. The results are shown in Figure 2(a) and (b). Figure 2 shows the results for an organic-inorganic nanocomposite prepared using hexagonal boron nitride with an average particle size of approximately 7 μm.

[0053] Figure 2(a) shows an X-ray CT image of the cross section of an organic-inorganic nanocomposite with an applied electric field, and Figure 2(b) shows an X-ray CT image of the cross section of an organic-inorganic nanocomposite without an applied electric field. In the sample with an applied electric field, the hBN particles exhibited a columnar structure in the thickness direction of the sample. This structure is thought to act as a thermal conduction path, improving thermal conductivity. Thus, X-ray CT confirmed that the organic-inorganic nanocomposite with an applied electric field had hBN particles oriented in the direction of the electric field, confirming the formation of a columnar structure and thermal conduction paths. On the other hand, such a structure was not observed in the sample without an applied electric field.

[0054] 2-2. Orientation degree evaluation (XRD) In this example, the degree of orientation of the organic-inorganic nanocomposite obtained in Example 1 above was evaluated by XRD measurement. Figure 3(a) shows the XRD measurement results for an organic-inorganic nanocomposite with and without an applied electric field. In the XRD spectrum, the peak near 2θ = 26-27° represents the BN(002) plane peak (corresponding to particles oriented in the in-plane direction of the composite), and the peak near 41-42° represents the BN(100) plane peak (corresponding to particles oriented perpendicular to the plane of the composite). While the sample without an applied electric field has many particles oriented in the in-plane direction, the sample with an applied electric field has many particles oriented perpendicular to the plane. To quantitatively evaluate the ratio of grains oriented in the in-plane and perpendicular directions, the following constants η (simple XRD spectrum peak ratio) and R (expected number of grains oriented perpendicular to the plane / expected number of grains oriented in the in-plane direction: perpendicular to the plane / in-plane orientation) were defined and calculated for comparison. A larger value of η indicates a more two-dimensional orientation in the perpendicular direction. [ka]

[0055] The result of calculating this constant is shown in Fig. 3(b). Referring to this, it has been confirmed that for samples without an applied electric field, the range is 0.1 < R < 1 and the orientation of the particles is in-plane orientation to random orientation, while for samples with an applied electric field, it is about 5 < R < 70, and it has been confirmed that many particles are oriented perpendicular to the plane.

[0056] 2-3. Evaluation of orientation (FE-SEM) In this example, regarding the inorganic filler in the organic-inorganic nanocomposite obtained by the above Example 1, the degree of orientation was evaluated by FE-SEM measurement. FE-SEM images of the cross-section (a, b in Fig. 4) and surface (c, d in Fig. 4) of the sample with an applied electric field, and the cross-section (e, f in Fig. 4) and surface (g, h in Fig. 4) of the sample without an applied electric field are shown below. Fig. 4 shows the results of an organic-inorganic nanocomposite prepared using hexagonal boron nitride with an average particle size of about 7 μm. According to these images, in the sample with an applied electric field, the state of hBN oriented in the longitudinal direction was confirmed, and it is considered that the horizontal edge can be seen. Also, when the surface was confirmed, the upper edge of the particles oriented in the longitudinal direction was confirmed. On the other hand, in the sample without an applied electric field, such longitudinal edges could not be confirmed in the cross-section, and almost no edges could be seen in the surface image, while polymer layers and the like were seen.

[0057] 2-4. Thermal conductivity and Young's modulus In this example, the change in the through-plane thermal conductivity and the in-plane Young's modulus of the organic-inorganic nanocomposite when the presence or absence of an applied electric field and the diameter of the hBN particles were changed was evaluated. The organic-inorganic nanocomposite was prepared in the same manner as in Example 1 except that the diameter of the hBN particles was changed. Thermal diffusivity was measured using a thermal diffusivity measurement device (ai-Phase Mobile M3 type 1, ai-Phase Co., Ltd.) using the temperature wave method. Specific gravity was measured using a dry hydrometer (AccuPyc II 1340, Micromeritics Instrument Corp) using the constant volume expansion method, and specific heat was measured using a differential scanning calorimeter (DSC; DSC 3500 Sirius, NETZSCH). Thermal conductivity k [W / mK] was calculated as the product of the measured thermal diffusivity α [m2 / s], specific gravity ρ [kg / m3], and specific heat cp [J / kg K], as shown in Equation c below. [ka]

[0058] Young's modulus was measured using a uniaxial tensile tester (STB-1225S, A&D Co., Ltd.) at room temperature for 0.03 s -1 The tensile test was performed at a constant strain rate of 100 sq. m / s, and the initial slope of the stress-elongation curve was defined as Young's modulus and calculated. The tensile test was performed using rectangular test pieces (width 2 mm, length 10 mm).

[0059] The results are shown in Figure 5. As shown in Figure 5, it was confirmed that, regardless of particle size, applying an electric field improves thermal conductivity and also improves flexibility. The improvement in thermal conductivity is thought to be due to the orientation of the hBN particles mentioned above and the formation of heat conduction paths due to the columnar structure. The improvement in flexibility is also thought to be due to the fact that the hBN particles are oriented in the perpendicular direction, which does not hinder the movement of polymers in the in-plane direction. Furthermore, when we looked at thermal conductivity, the highest thermal conductivity was observed around 5 to 7 μm. This is similar in shape to the graph of the degree of orientation mentioned above, so it is thought that this varies depending on the degree of orientation. On the other hand, finer particles show lower values, but this is thought to be because a large number of particles are required to connect all the heat conduction paths in the thickness direction, making it difficult to see the effect of improving thermal conductivity through orientation. A peak was also observed in Young's modulus around 7 μm.

[0060] (Example 3. Study of combinations of inorganic fillers) 3-1. Preparation of organic-inorganic nanocomposite 2 In this example, an organic-inorganic nanocomposite was prepared using a combination of inorganic fillers with large and small particle sizes. Specifically, hexagonal boron nitride (hBN) was used as the inorganic filler, and was a mixture of Sigma-Aldrich's hBN with an average particle size of approximately 200 nm and Denka's hBN with an average particle size of approximately 7 μm in a weight ratio of 200 nm:7 μm = 1:9. The mixing ratio of the suspension for preparing the organic-inorganic nanocomposite was as shown in the table below (the total amount of hBN was 65 wt% of the total sample weight excluding the solvent).

[0061] [Table 3]

[0062] Except for changing the inorganic filler to a combination of two types and changing the mixing ratio of the suspension for preparing the organic-inorganic nanocomposite as shown in the table above, an organic-inorganic nanocomposite was prepared in the same manner as in Example 1. The hBN content in the obtained organic-inorganic nanocomposite was 33 vol%.

[0063] 3-2. Orientation degree evaluation (X-ray CT) The internal structure of the obtained organic-inorganic nanocomposite was evaluated by measuring X-ray CT in the same manner as in "2-1. Evaluation of orientation (X-ray CT)" above. The results are shown in Figure 6. As shown in Figure 6, the application of an electric field confirmed the creation of micro-columnar structures and heat conduction paths in the vertical direction of the photograph. The results of the 2D FFT also confirmed that the application of an electric field caused the inorganic filler, which is a 2D material, to be oriented in the 2D plane direction.

[0064] 3-3. Evaluation of orientation (FE-SEM) The degree of orientation of the inorganic filler in the organic-inorganic nanocomposite was evaluated in the same manner as in "2-3. Evaluation of the degree of orientation (FE-SEM)" above. The results are shown in Figure 7. As shown in Figure 7, the degree of orientation of the organic-inorganic nanocomposite without an applied electric field was 0.023. On the other hand, the degree of orientation of the organic-inorganic nanocomposite with an applied electric field increased to 3.97. In this way, it was confirmed that the application of an electric field increased the degree of orientation (the number of particles oriented in the two-dimensional plane direction increased).

[0065] 3-3. Thermal conductivity and Young's modulus The thermal conductivity and Young's modulus of the organic-inorganic nanocomposite obtained in "3-1. Preparation of organic-inorganic nanocomposite 2" above were measured in the same manner as in "2-4. Thermal conductivity and Young's modulus" above, and the thermal conductivity in the perpendicular direction and in-plane direction was measured. The results are shown in Figure 8. As shown in Figure 8, it can be seen that the sample without an applied electric field had a thermal conductivity that was about three times higher in the in-plane direction, while the sample with an applied electric field had a thermal conductivity that was about three times higher in the perpendicular direction. This suggests that the electric field caused a thermal anisotropy of about nine times. Furthermore, the sample with an applied electric field showed a value close to 11 W in the perpendicular direction. When the thermal directionality was evaluated as the thermal conductivity in the filler orientation direction (direction perpendicular to the surface) divided by the thermal conductivity in the direction perpendicular to the filler orientation (in-plane direction), the thermal directionality was 3.0. Thus, the organic-inorganic nanocomposite of the present invention has superior thermal directionality compared to conventional nanocomposites.

[0066] The results of the Young's modulus measurements are shown in the table below. [Table 4] Compared to the sample without an applied electric field, the sample with an applied electric field showed a decrease in Young's modulus (improved flexibility). This is thought to be because the hBN particles were oriented and aligned vertically, which did not inhibit the movement of polymers in the in-plane direction, thereby reducing the decrease in flexibility due to the addition of hBN particles.

[0067] 3-4.Electrical resistivity The electrical resistivity in the thickness direction of the organic-inorganic nanocomposite obtained in "3-1. Preparation of organic-inorganic nanocomposite 2" above was measured using a high resistivity meter (Hirest-UX MCP-HT800, Nittoseiko Analytech) using the MCC-A method. The results are shown in the table below. As the results shown in the table indicate, the composite sample maintained its insulating properties and can be used as an insulating material. The electrical resistivity of the organic-inorganic composite to which an electric field was applied was approximately 2.5 × 10 Ω / cm 2 , which is the same as the electrical resistivity (approximately 2.5 × 10 Ω / cm 2 ) of a conventional sample with an inorganic filler content of 30 wt% (J. Phys. D: Appl. Phys. 54 (2021) 425202 K. Inoue et al.). 10 ) showed high insulation properties. [Table 5]

[0068] (Example 4. Study of the content of small diameter filler) 4-1. Preparation of organic-inorganic nanocomposites 3 In this example, a combination of inorganic fillers with large and small particle sizes was used as the inorganic filler, and the content of small particle size fillers relative to the total amount of inorganic fillers was varied to prepare organic-inorganic nanocomposites, and their properties were evaluated. Specifically, organic-inorganic nanocomposites were prepared in the same manner as in Example 3, except that the content of small diameter fillers relative to the total amount of inorganic fillers was set to 0 wt%, 10 wt%, 20 wt%, 30 wt%, 50 wt%, or 100 wt%.

[0069] 4-2. Thermal conductivity and Young's modulus The thermal conductivity and Young's modulus of the organic-inorganic nanocomposite obtained in "4-1. Preparation of organic-inorganic nanocomposite 3" above were measured in the same manner as described in "2-4. Thermal conductivity and Young's modulus" above. The results are shown in Figure 9. The graph in Figure 9 shows the change in thermal conductivity and Young's modulus as a function of the value of r (the content of 0.2 μm inorganic filler relative to the total amount of inorganic filler). A general trend was observed in which the values ​​of thermal conductivity and Young's modulus both decreased (improving thermal conductivity and flexibility) as the value of r increased.

[0070] (Example 5. Examination of inorganic filler content) 5-1. Preparation of organic-inorganic nanocomposites 4 In this example, inorganic fillers having large particle diameters and small particle diameters were used in combination, and the content of the inorganic fillers was changed to prepare organic-inorganic nanocomposites. Specifically, organic-inorganic nanocomposites were prepared in the same manner as in Example 3, except that the content of the inorganic filler was changed from 50 wt % to 60 wt % or 65 wt %.

[0071] 5-2. Orientation degree evaluation (XRD) The degree of orientation of the organic-inorganic nanocomposite obtained in "5-1. Preparation of organic-inorganic nanocomposite 4" was confirmed in the same manner as in "2-2. Evaluation of degree of orientation (XRD)" above. The results are shown in Figure 10. The graph in Figure 10 includes data from prior literature 1 (Han Y, Lv S, Hao C, Ding F, Zhang Y. Thermal conductivity enhancement of BN / silicone composites cured under electric field: Stacking of shape, thermal conductivity, and particle packing structure anisotropies. Thermochim Acta 2012;529:68-73. https: / / doi.org / 10.1016 / j.tca.2011.11.029.) and prior literature 2 (Cho HB, Nakayama T, Tokoi Y, Endo S, Tanaka S, Suzuki T, et al. Facile preparation of a polysiloxane-based hybrid composite with highly-oriented boron nitride nanosheets and an unmodified surface. Compos Sci Technol 2010;70:1681-6. The graph also shows the degree of orientation of the nanocomposite produced by the method described in [https: / / doi.org / 10.1016 / j.compscitech.2010.05.012.]. As shown in the graph in Figure 10, it has been reported that the degree of orientation decreased when the hBN content was increased in the nanocomposites disclosed in Prior Art Documents 1 and 2. In contrast, the organic-inorganic nanocomposite of this example maintained an extremely high degree of orientation, despite containing a higher hBN content (approximately 30-50 vol%) than conventional nanocomposites.

[0072] 5-3. Thermal conductivity and Young's modulus The thermal conductivity of the organic-inorganic nanocomposite obtained in "5-1. Preparation of organic-inorganic nanocomposite 4" above was measured in the same manner as in "2-4. Thermal conductivity and Young's modulus" above. The results are shown in Figure 11. As expected, an improvement in thermal conductivity was observed by increasing the inorganic filler content. In particular, at 65 wt%, a value of 10 W / mK was obtained, which is thought to be comparable to that of metals. As mentioned above, this improvement in thermal conductivity is thought to be due to the fact that a high degree of orientation is maintained even when the content is increased. Young's modulus also improved (flexibility decreased) as the content increased. However, the effect of the electric field relatively suppressed the decrease in flexibility, and even at an inorganic filler content of 65%, the value was kept at 77 MPa, which is in the elastomer range. When the physical properties of this study are plotted on an Ashby plot, the result is shown in Figure 12. The organic-inorganic nanocomposites provided by the present invention, including the organic-inorganic nanocomposite of this example, exhibit completely new physical properties. The table below compares the perpendicular thermal conductivity of polymer / BN composite sheets of the present invention and conventional ones when an electric field is applied (wt% is calculated from vol%, and the densities of hBN and polysiloxane were calculated using values ​​of 2.3 and 0.97, respectively). The organic-inorganic nanocomposite provided by the present invention successfully achieves electric field orientation at a high inorganic filler content, resulting in a thermal conductivity nearly one order of magnitude higher than that of conventional nanocomposites. [Table 6]

Claims

1. An organic-inorganic nanocomposite comprising one or more polyrotaxanes or a polymer blend comprising one or more polyrotaxanes and a plasma-treated inorganic filler, The organic-inorganic nanocomposite contains the inorganic filler in an amount of 30 vol % or more, the inorganic filler is a two-dimensional material and an insulating filler having thermal anisotropy; the inorganic filler is oriented with an orientation degree of 3 or more in the direction perpendicular to the surface of the organic-inorganic nanocomposite; Organic-inorganic nanocomposites.

2. 10. The organic-inorganic composite of claim 1, The organic-inorganic nanocomposite has a thermal orientation of 1 or more. Organic-inorganic nanocomposites.

3. 2. The organic-inorganic nanocomposite of claim 1, Young's modulus is 200 MPa or less; Organic-inorganic nanocomposites.

4. 2. The organic-inorganic nanocomposite of claim 1, The organic-inorganic nanocomposite has a thermal conductivity of 3 W / mK or more in a direction perpendicular to the surface of the organic-inorganic nanocomposite.

5. 2. The organic-inorganic nanocomposite of claim 1, Electrical resistivity is 1.00 x 10 １０ That's it, organic-inorganic nanocomposite.

6. 2. The organic-inorganic nanocomposite of claim 1, An organic-inorganic nanocomposite, wherein the inorganic filler is hexagonal boron nitride.

7. 2. The organic-inorganic nanocomposite of claim 1, The organic-inorganic nanocomposite, wherein the inorganic filler has an average particle size of 0.01 to 100 μm.

8. 2. The organic-inorganic nanocomposite of claim 1, An organic-inorganic nanocomposite, wherein the inorganic filler comprises two types of inorganic fibers of different sizes.

9. 2. The organic-inorganic nanocomposite of claim 1, The organic-inorganic nanocomposite has a weight ratio of the large-diameter inorganic filler to the small-diameter inorganic filler of 10:0 to 5:

5.

10. 2. The organic-inorganic nanocomposite according to claim 1, wherein the large-diameter inorganic filler has an average particle size of 1 to 50 μm, and the small-diameter inorganic filler has an average particle size of 0.05 to 1 μm.

11. 2. The organic-inorganic nanocomposite of claim 1, An organic-inorganic nanocomposite in which polyrotaxane pulley molecules are chemically modified.

12. 10. A method for producing the organic-inorganic nanocomposite of claim 1, comprising:

2. A method for producing the nanocomposite described in claim 1, characterized in that one or more types of polyrotaxane or a polymer blend containing one or more types of polyrotaxane, a crosslinking agent, and a catalyst for a crosslinking reaction are dissolved in a solvent, the solution in which the inorganic filler is dispersed is subjected to a crosslinking reaction under the application of a high electric field by a bipolar pulse, and then the solvent is removed.

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