KR20210151328A - Transparent porous polysiloxane substrate and the method preparing the same - Google Patents

Abstract

The present invention relates to a transparent porous polysiloxane substrate and a method for manufacturing the same. Furthermore, the present invention relates to a method for manufacturing a transparent porous polysiloxane substrate easily and economically, by using an organic solvent with excellent affinity for both water and a siloxane-based prepolymer. More specifically, the present invention relates to a transparent porous polysiloxane substrate that has closed pores with a uniform diameter distribution by controlling the average diameter of the closed pores, and thus has high light transmittance in the visible light range, and to a method for manufacturing the same.

Description

Porous transparent siloxane-based polymer substrate and manufacturing method thereof

The present invention relates to a porous transparent siloxane-based polymer substrate and a method for manufacturing the same, and to a method for easily and economically manufacturing a porous transparent siloxane-based polymer substrate using an organic solvent having excellent affinity between water and a siloxane-based prepolymer. . More specifically, it relates to a porous transparent siloxane-based polymer substrate having closed pores having a uniform diameter distribution and controlled average diameter of closed pores so as to have high light transmittance in the visible light range, and a method for manufacturing the same.

Porous polymers with many pores inside the polymer have superior flexibility and elasticity compared to polymers without pores, so research is being actively conducted as materials for electronic devices, biomaterials, molecular diagnostic sensors, and separators.

Among them, as a material applicable to the optical film of a smart window, which is an electronic device field, research on materials that can control the visible light transmittance using external stimuli such as electricity, heat, light, etc. are being actively researched. Porous polydimethylsiloxane is attracting attention as a candidate.

Porous polydimethylsiloxane (PDMS) is inexpensive, non-toxic, non-flammable, elastic and flexible. In addition, it is being studied as one of the porous polymers applicable to the field of electronic devices because it is thermally stable at -50 to 200 °C and has high mechanical properties that can be easily deformed along a curved surface.

However, in order to apply the porous polydimethylsiloxane to the smart window field, it is necessary to improve the visible light transmittance by controlling the shape of the pores, the diameter of the pores, and the distribution of the pore diameters.

As a method for producing porous polydimethylsiloxane, a method using a blowing agent, a method using an emulsion system, and a method using a cosolvent system have been proposed.

The method of using a foaming agent is a method of randomly forming pores in a polydimethylsiloxane substrate by the generation of random cells, and the volume of the pores can be adjusted according to the content of the foaming agent. The method has high economic efficiency and productivity by using a relatively simple process, but has the disadvantage that the shape, diameter and distribution of pores cannot be controlled.

In the method of using the emulsion system, a good solvent having a solubilizing power for polydimethylsiloxane and a non-solvent having no solubilizing power for polydimethylsiloxane and not having miscibility with a good solvent at the same time are mixed. Thus, the solvent forms a dispersed phase and the good solvent and polydimethylsiloxane form a continuous phase. This emulsion system can be roughly divided into a method using a surfactant (emulsifier) and a method not using a surfactant (emulsifier) again.

An emulsion system using a surfactant mixes a good solvent, a surfactant, polydimethylsiloxane and a nonsolvent, and mechanically disperses the nonsolvent through an appropriate mixing device to finely disperse the nonsolvent in the continuous phase composed of the good solvent and polydimethylsiloxane. to form an opaque or translucent emulsion. By subsequently removing the good solvent and the non-solvent from the emulsion, the volume occupied by the non-solvent is converted into pores to prepare porous polydimethylsiloxane. The method has the advantage that the dispersed phase has high colloidal stability because the surfactant is located at the interface of the emulsion to minimize Gibb's free energy. However, since the particle size of the dispersed phase is controlled according to the energy of the mechanical stirring device rather than thermodynamically, it is not easy to control the diameter and distribution of the pores, and the surfactant is embedded in the substrate, so it is practically difficult to remove the surfactant from the substrate. The downside is that it's impossible.

In order to solve this drawback, a method of using a good solvent and a non-solvent without including a surfactant has been proposed. However, since the interface has a very high free energy, the dispersed phases easily coalesce, and very low colloidal stability. Therefore, it is difficult to form pores having an average diameter of 100 μm or less, and it is difficult to reproducibly control the diameter and distribution of pores.

In order to solve the problems described above, a method for preparing porous polydimethylsiloxane using water and a ketone-based organic solvent has been proposed. However, the method using the ketone-based organic solvent also has difficulty controlling the average diameter and distribution of closed pores, and thus has a low light transmittance in visible light. Therefore, there is a need for development of a method for preparing a porous transparent polydimethylsiloxane capable of increasing the light transmittance in visible light by controlling the average diameter and distribution of closed pores.

Republic of Korea Patent Publication No. 10-1670232 (2016.10.24)

An object of the present invention is to provide a novel porous transparent siloxane-based polymer substrate with improved light transmittance in visible light by uniformly controlling the average diameter of closed pores and the diameter distribution of pores, and a method for manufacturing the same, in order to solve the above problems will provide Specifically, it has closed pores of smaller and uniform average diameter compared to the prior art, and thus the closed pores reduce the path taken for light to pass through, thereby remarkably improving light transmittance in visible light of 400 to 700 nm. To provide a method for manufacturing a siloxane-based polymer substrate.

The method for producing a porous transparent siloxane-based polymer according to the present invention comprises the steps of: a) preparing a reaction solution by mixing a mixed solution of water and a C3 to C4 alcohol, and a siloxane-based prepolymer; and b) curing the reaction solution; It is characterized in that it includes.

The C3 to C4 alcohol may be 1-propanol, isopropanol, n-butanol, tert-butanol, sec-butanol or isobutanol.

The water may be included in an amount of 1 to 10 wt%, the C3 to C4 alcohol in an amount of 1 to 30 wt%, and the siloxane-based prepolymer in an amount of 60 to 98 wt%.

The porous transparent siloxane-based polymer substrate according to the present invention has a light transmittance of 70% or more in visible light of 400 to 700 nm, and includes a plurality of closed pores.

The plurality of closed pores may have an average diameter of 0.1 to 10 μm.

The porous transparent siloxane-based polymer substrate according to the present invention has the effect of remarkably improved light transmittance in visible light because the average diameter of the closed pores and the diameter distribution of the pores are uniform. In detail, the porous transparent siloxane-based polymer according to the present invention has closed pores having a smaller and uniform average diameter compared to the prior art, and thus the closed pores reduce the path taken for light to pass through, thereby reducing light in the visible light range of 400 to 700 nm. The transmittance can be significantly improved.

In addition, in the method of manufacturing a porous transparent siloxane-based polymer substrate according to the present invention, the average diameter and distribution of pores are not kinetically-controlled, but thermodynamically controlled, and thus have high reproducibility and are incorporated into the porous transparent siloxane-based polymer substrate. It has the advantage that the average diameter of the pores to be formed is small and the distribution of the pores is uniform.

In addition, the method for manufacturing a porous transparent siloxane-based polymer substrate according to the present invention has an advantage in that it can be easily and economically prepared on a porous transparent siloxane-based polymer substrate through a solvent evaporation process by using a simple co-solvent system.

1 is a photograph taken with a scanning electron microscope of a cross section of a porous transparent siloxane-based polymer substrate prepared according to (a) Example 4, (b) Comparative Example 2, and (c) Comparative Example 1. FIG.
2 is a photograph taken with a scanning electron microscope of a cross section of a porous transparent siloxane-based polymer substrate prepared according to (a) Comparative Example 5, (b) Comparative Example 2, (d) Comparative Example 4, and (d) Example 4; to be.
3 is a view showing the change in light transmittance at 400 to 700 nm of the porous transparent siloxane-based polymer substrate according to the content of isopropanol. IPA 0 means Comparative Example 1, PDMS means Comparative Example 3, IPA 1 means Example 1, IPA 2 means Example 2, IPA 5 means Example 3, and IPA 10 means Example 4.
4 is a view showing the contact angle measurement of the porous transparent siloxane-based polymer substrate prepared according to (a) Comparative Example 3, (b) Comparative Example 1, (c) Example 1, (d) Example 3, (e) Example 4; A drawing showing the results.

Hereinafter, the present invention will be described in more detail. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

Also, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

As used herein, the term 'siloxane-based prepolymer' is a polymer including siloxane-based repeating units, and refers to a siloxane-based polymer before curing.

The inventors of the present invention have improved research on a method for manufacturing a porous siloxane-based polymer substrate using a co-solvent system, and have deepened research on a new manufacturing method capable of improving light transmittance in the visible light region. Meanwhile, when a porous siloxane-based polymer substrate is prepared using a co-solvent system of a specific type of alcohol and water, it has affinity for both water and the siloxane-based prepolymer, thereby reducing the time and energy required for mixing. However, it was found that the mixture can be uniformly mixed. Moreover, in the case of manufacturing using the alcohol and water co-solvent system, the average diameter of the closed pores formed inside the siloxane-based polymer is much smaller than that of the conventional manufacturing method, and the distribution of pores is uniform, so that light is transmitted The present invention was completed by discovering that there is a remarkable effect of increasing the light transmittance by decreasing the path.

Hereinafter, a method for manufacturing a porous transparent siloxane-based polymer substrate according to the present invention will be described in detail.

The method for producing a porous transparent siloxane-based polymer according to the present invention comprises the steps of: a) preparing a reaction solution by mixing a mixed solution of water and a C3 to C4 alcohol, and a siloxane-based prepolymer; and b) curing the reaction solution.

First, the step of a) preparing a reaction solution by mixing a mixed solution of water and a C3 to C4 alcohol with a siloxane-based prepolymer will be described in detail.

Among alcohols, C3 to C4 alcohols are solvents that are friendly to both water and the siloxane-based prepolymer, and can increase the miscibility between water and the siloxane-based prepolymer to reduce the time and energy required for mixing.

Specifically, the C3 to C4 alcohol may be 1-propanol, isopropanol, n-butanol, tert-butanol, sec-butanol or isobutanol. The above type of alcohol may uniformly dissolve or disperse the siloxane-based prepolymer in water and an alcohol cosolvent, rather than using methanol, ethanol, or C5 or higher alcohol. Specifically, the C3 to C4 alcohol has strong hydrophilicity, thereby weakening the hydrophobicity of the hydrophobic siloxane-based prepolymer, thereby improving miscibility with water. In addition, by having a certain level of surface activity through the hydrocarbon chain of the C3 to C4 alcohol, small, uniform, and widely dispersed water droplets in the continuous phase of the siloxane-based prepolymer can be made. On the other hand, in ethanol, the hydrocarbon chain is too short to uniformly and widely disperse water droplets in the continuous phase of the siloxane-based prepolymer, and alcohols of C5 or higher have too long chains to form small and uniform water droplets.

The siloxane-based prepolymer includes at least one reactive functional group in a main chain or side chain, and includes aliphatic polysiloxane, aromatic polysiloxane, or siloxane repeating units each independently comprising an aliphatic group and an aromatic group in one repeating unit. A polysiloxane prepolymer comprising can be Preferably, the siloxane-based prepolymer may be liquid at room temperature.

The reactive functional group may be a vinyl group or an acrylic group as a polymerizable functional group. Specific examples of the prepolymer may be selected from polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polydimethylsiloxane-co-diethylsiloxane, polydimethylsiloxane-co-ethylmethylsiloxane, and the like, and the aromatic polysiloxane is polydiethylsiloxane. phenylsiloxane, polymethylphenylsiloxane, polyethylphenylsiloxane, poly(dimethylsiloxane-co-diphenylsiloxane), and the like. The polysiloxane comprising a siloxane repeating unit including both an aliphatic group and an aromatic group in one repeating unit or each independently includes both the repeating unit of the aliphatic siloxane and the repeating unit of the aromatic siloxane as illustrated above, or the aliphatic substituent and The aromatic substituents exemplified above may mean a form in which each is bonded to a silicon element positioned within one repeating unit, but is not limited thereto.

In particular, among the above examples, when polydimethylsiloxane is used, the C3 to C4 alcohol with strong hydrophilicity effectively reduces the hydrophobicity of the polydimethylsiloxane, so that it can be uniformly mixed with water and the C3 to C4 alcohol. have. Accordingly, small and uniform water droplets are formed therein, so that upon curing, a plurality of closed pores having an average diameter of several μm, specifically, an average diameter of 0.1 to 10 μm can be manufactured, which is more preferred.

The siloxane-based prepolymer may include a crosslinking agent. The crosslinking agent may be a polyfunctional organic crosslinking agent, a siloxane-based curing agent containing a Si-O bond, or an organosilazane-based curing agent containing a Si-N bond, but is not limited thereto. As a non-limiting example, it may be an aliphatic or aromatic polysiloxane containing -(RaHSiO)-group. Ra may be an aliphatic group or an aromatic group, the aliphatic group may be a methyl group, an ethyl group, or a propyl group, and the aromatic group may be a phenyl group or a naphthyl group, and the substituent is substituted with another substituent within a range that does not affect the crosslinking reaction. It may be or may be unsubstituted, but this is only an example and the number of carbon atoms and types of substituents are not limited. In one non-limiting embodiment, polymethylhydrogensiloxane [(CH3)3SiO(CH3HSiO)xSi(CH3)3], polydimethylsiloxane [(CH3)2HSiO((CH3)2SiO)xSi(CH3)2H], poly It may be phenylhydrogensiloxane [(CH3)3SiO(PhHSiO)xSi(CH3)3] or polydiphenylsiloxane [(CH3)2HSiO((Ph)2SiO)xSi(CH3)2H], and in this case, the addition-type silicone-based prepolymer It is preferable to control the content of Si-H according to the number of vinyl groups contained therein, and for example, x may be 1 or more, and more preferably 2 to 10, but is not limited thereto.

Specifically, preparing the reaction solution is a step in which the C3 to C4 alcohol improves the miscibility of water and the siloxane-based prepolymer so that small water droplets can be uniformly dispersed in the siloxane-based prepolymer. . In addition, the C3 to C4 alcohol is a compound having a hydrocarbon chain, so that water droplets are uniformly and widely dispersed in the siloxane-based prepolymer to form uniformly and widely distributed closed pores upon curing.

Of the total weight of the reaction solution, 1 to 10% by weight of water, 1 to 30% by weight of the C3 to C4 alcohol, and 60 to 98% by weight of the siloxane-based prepolymer. Preferably, the water may be included in an amount of 1 to 6 wt%, the C3 to C4 alcohol in an amount of 5 to 25 wt%, and the siloxane-based prepolymer in an amount of 70 to 94 wt%.

In the mixed solution, the weight ratio of water and C3 to C4 alcohol may be 1: 0.01 to 10, preferably 1: 0.02 to 5, and more preferably 1: 0.05 to 4. In the reaction solution, a weight ratio of the mixed solution and the siloxane-based prepolymer may be 1: 2 to 30, preferably 1: 5 to 20.

As the weight ratio of the alcohol in the mixed solution increases, the average diameter of the pores decreases and it may be preferable to use the same or a larger amount of the alcohol as the water in that the average diameter of the pores decreases and the pores can have a more uniform diameter distribution. The weight ratio of the C3 to C4 alcohol may be 1:1 to 4, preferably 1:1 to 2, but is not limited to the above numerical range.

As a method of mixing the mixed solution obtained by mixing water and C3 to C4 alcohol with the siloxane-based prepolymer, a known method commonly used for mixing a liquid may be used, and examples include a homomixer, an ultrasonic stirrer, and mechanical stirrers such as magnetic stirrers and overhead stirrers. When using the mechanical stirrer, the reaction solution can be prepared by stirring at 15 to 30 ° C. at 100 to 2,000 rpm, preferably at 300 to 1,000 rpm for 0.5 to 30 minutes, preferably for 0.5 to 20 minutes, to prepare a reaction solution. do not receive

Next, the step of b) curing the reaction solution will be described in detail. The method of curing the reaction solution may be any method generally used for curing the siloxane-based polymer, and for example, high temperature thermosetting, room temperature curing, ultraviolet curing, ultrasonic curing, etc. may be used. During the high-temperature thermosetting, the reaction solution may be poured into a mold and cured in an oven at 60 to 100° C., preferably at 70 to 90° C., for 0.1 to 5 hours, preferably 0.3 to 2 hours. In the curing of the reaction solution, water and a C3 to C4 alcohol allow the water droplets formed inside the siloxane-based polymer to evaporate while forming closed pores.

After the curing process as described above, drying is performed at 15 to 30° C. for 0.5 to 10 hours, preferably 0.5 to 5 hours, and water and alcohol are removed to finally prepare a porous transparent siloxane-based polymer substrate.

Hereinafter, the porous transparent siloxane-based polymer substrate according to the present invention will be described in detail.

The porous transparent siloxane-based polymer substrate according to the present invention can be manufactured through the manufacturing method as described above, and has a light transmittance of 70% or more in visible light of 400 to 700 nm, and includes a plurality of closed pores. .

The plurality of closed pores may have an average diameter of 0.1 to 10 μm, preferably 0.5 to 5 μm.

As described above, in the manufacturing method according to the present invention, a mixed solution of water and a C3 to C4 alcohol having strong hydrophilicity is used to reduce the hydrophobicity of the siloxane-based prepolymer to be well mixed with water, and water is the siloxane-based prepolymer. To form small and uniform water droplets within, it is possible to form closed pores having an average diameter in the above range upon curing. Therefore, it is possible to form pores having a smaller and more uniform diameter compared to preparing a porous transparent siloxane-based polymer using only water.

The porous transparent siloxane-based polymer substrate may have high light transmittance despite having a pore structure, and may have a mechanical strength in a range substantially similar to that of a transparent siloxane-based polymer substrate not including a pore structure. Preferably, the porous transparent siloxane-based polymer substrate may have a light transmittance of 75% or more in visible light of 400 to 700 nm, more preferably 80% or more, and may be 95% or less without limitation. In addition, low-molecular-weight additives such as surfactants that may reduce the physical properties of the substrate or reduce applicability in commercial applications may not be included.

In addition, when the average diameter of the plurality of closed pores is 1 to 5 μm, the standard deviation may be 1 or less, preferably 0.8 or less, more preferably 0.75 or less, and may be 0.5 or more without limitation.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following examples and comparative examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following examples and comparative examples.

[Method of measuring physical properties]

1. Light transmittance

Using a UV-visible spectrophotometer (V650, JASCO Co.), the transmittance of the samples of Examples and Comparative Examples was measured in the visible region of 400 to 700 nm. The thickness of the sample was measured to be 2 mm, and the results are shown in Table 1 and FIG. 3 .

2. SEM image

Cross sections of the samples of Examples and Comparative Examples having a thickness of 2 mm were measured with a scanning electron microscopy (SEM) of JEOL's model name IT-500, and the results are shown in FIGS. 1 and 2 .

3. Contact angle measurement (hydrophobicity)

The area of the prepared Examples and Comparative Examples samples was cut to 0.5 cm2, 1 μl distilled water was dropped on the surface in the form of water droplets, and the contact angle with the surface was measured using AD7013MT optical microscope equipment of Dino lite, and the results were obtained. 4 is shown.

[Example 1]

A mixed solution was prepared by including water and isopropanol in a weight ratio of 5: 1, and the mixed solution and polydimethylsiloxane were included in a weight ratio of 1: 16, and stirred at 500 rpm for 1 minute using a stirrer at 25 ° C. to prepare a reaction solution.

The prepared reaction solution was poured into a mold, cured in an oven at 80° C. for 30 minutes, and dried at 25° C. for 1 hour to prepare a porous siloxane-based polymer substrate. The light transmittance, SEM image, and contact angle at 400 to 700 nm were measured It was measured and the results are shown in Table 1 and FIGS. 1 to 4 .

[Example 2]

In Example 1, the mixed solution contained water and isopropanol in a weight ratio of 5:2, and the dispersion was prepared by including the mixed solution and polydimethylsiloxane in a weight ratio of 1:13, except that it was prepared in the same manner.

[Example 3]

In Example 1, the mixed solution contained water and isopropanol in a weight ratio of 1:1, and the dispersion was prepared by including the mixed solution and polydimethylsiloxane in a ratio of 1:9, except that it was prepared in the same manner.

[Example 4]

In Example 1, the mixed solution contained water and isopropanol in a weight ratio of 1: 2, and the dispersion was prepared by including the mixed solution and polydimethylsiloxane in a weight ratio of 1: 5.6, except that it was prepared in the same manner.

[Comparative Example 1]

In Example 1, without using isopropanol, water and polydimethylsiloxane were included in a weight ratio of 1:19, and the stirring speed was 2000 rpm, except for stirring for 1 hour.

[Comparative Example 2]

Example 1 was carried out in the same manner except that acetone was used instead of isopropanol.

[Comparative Example 3]

Example 1 was carried out in the same manner except for using only polydimethylsiloxane without using water and isopropyl alcohol.

[Comparative Example 4]

Example 1 was carried out in the same manner except that ethanol was used instead of isopropanol.

[Comparative Example 5]

Example 1 was carried out in the same manner except that chloroform was used instead of isopropanol.

Pore area fraction (%) total number of pores
(128 × 96 μm per ²⁾ Average pore diameter (㎛) Example 1 5.13 133 2.16 Example 2 5.78 232 1.81 Example 3 5.92 307 1.59 Example 4 7.36 418 1.55 Comparative Example 1 6.81 49 2.97 Comparative Example 3 - - -

Referring to Table 1, FIGS. 1 and 2, in Examples 1 to 4, it was found that a large number of pores were generated, the average diameter of the pores was controlled within 2.5 μm, and the diameters of the pores were also uniformly distributed. In particular, Example 4 showed that the light transmittance at 400 to 700 nm was substantially equivalent to that of the polydimethylsiloxane substrate (pristine PDMS substrate) not including pores. On the other hand, in Comparative Example 1, in which porous polysiloxane was prepared using only water, some large-diameter pores were generated, and light transmittance was not good at 70 or less at 400 to 700 nm.

In addition, in Comparative Example 2 prepared using acetone, Comparative Example 3 prepared using only polydimethylsiloxane, Comparative Example 4 using ethanol, and Comparative Example 5 using chloroform, the average diameter of the pores was large and the distribution of pores was very non-uniform. It was found that the light transmittance was remarkably low at 400 to 700 nm.

In addition, as can be seen in FIG. 3 below, it can be confirmed that the light transmittance increases at 400 to 700 nm when prepared by gradually increasing isopropanol. This suggests that water is more uniformly dispersed in the polydimethylsiloxane continuous phase as water droplets having a smaller particle diameter by increasing the surface activity effect as the content of isopropanol in water increases.

4 is a graph showing the measurement of contact angles between water droplets and the surface of the porous transparent siloxane-based polymer substrates prepared according to Examples 1, 3, 4, Comparative Examples 1 and 3, respectively. Referring to FIG. 4 , it can be seen that the contact angle increases as the sample prepared by increasing the content of isopropanol increases.

As described above, the present invention has been described by specific matters and limited examples, but these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and the field to which the present invention belongs Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims described below, but also all of the claims and all equivalents or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (5)

a) preparing a reaction solution by mixing a mixed solution of water and a C3 to C4 alcohol, and a siloxane-based prepolymer; and
b) curing the reaction solution;
A method for producing a porous transparent siloxane-based polymer substrate comprising a. The method of claim 1,
Wherein the C3 to C4 alcohol is 1-propanol, isopropanol, n-butanol, tert-butanol, sec-butanol or isobutanol. The method of claim 1,
The water is 1 to 10% by weight, the C3 to C4 alcohol is 1 to 30% by weight, and the siloxane-based prepolymer is included in an amount of 60 to 98% by weight. A porous transparent siloxane-based polymer substrate having a light transmittance of 70% or more at 400 to 700 nm and comprising a plurality of closed pores. 5. The method of claim 4,
The plurality of closed pores has an average diameter of 0.1 to 10 ㎛ porous transparent siloxane-based polymer substrate.

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