KR100823895B1 - Superhydrophobic coating film comprising inorganic particles having different diameters, coating composition, and the forming method of coating film - Google Patents

Abstract

A superhydrophobic coating film, and a method for forming the superhydrophobic coating film are provided to improve self-cleaning property and to allow a nanofiber comprising inorganic particles to be prepared relatively easily and massively. A superhydrophobic coating film comprises at least two kinds of inorganic particles having different diameter. Also the superhydrophobic coating film comprises at least two kinds of inorganic particles having different diameter which are dispersed in a polymer solution. Preferably the inorganic particles are selected from the group consisting of silica, titanium dioxide, alumina, ceria and zirconium oxide. Preferably the polymer of the polymer solution is selected from polyethylene oxide, polyacrylamide, poly(vinyl alcohol), polyethylene glycol, polyacrylonitrile, poly(vinyl pyrrolidone), polystyrene, polycaprolactone, and polyethylene terephthalate.

Description

Superhydrophobic coating film comprising inorganic particles having different diameters, coating composition, and the forming method of coating film}

1 is a schematic diagram of an electrospinning apparatus that may be used to form a superhydrophobic coating film in accordance with the present invention.

Figure 2 is a photograph showing the shape change of the mixture droplets formed on the capillary end with the strength of the voltage applied to the metal capillary connected to the syringe tip.

Figure 3 is an electron micrograph before and after the selective removal of the polymer through the sintering of the composite nanofiber obtained from the silica / polyethylene oxide mixture according to Example 2 of the present invention.

Figure 4 is an electron micrograph before and after the selective removal of the polymer by sintering the composite nanofiber obtained from the silica / polyacrylamide mixture according to Example 2 of the present invention.

FIG. 5 is a photograph of a substrate surface-treated in the method of Example 3 after sintering a composite nanofiber obtained from a silica / polyacrylamide mixture using a 4-inch silicon wafer as a substrate according to Example 2 of the present invention. FIG.

FIG. 6 shows X-ray photoelectron spectroscopy of nanofibers treated with a) before and b) after sintering and c) with the method of Example 3 of silica / polyacrylamide composite nanofibers obtained according to Example 2 of the present invention. Analysis spectrum.

7 is a contact angle photograph of a silicon wafer surface treated according to the method of Example 3 without any structure for comparison, a candle made from b) polyethylene oxide and c) polyacrylamide by the methods of Examples 2 and 3; Contact angle photo for hydrophobic film.

The present invention relates to a superhydrophobic coating layer composed of inorganic particles and a method for forming the same, and more particularly, to a superhydrophobic coating layer made of inorganic particles suitable for self-cleaning, and water droplets easily roll down even with a slight tilt. will be.

Superhydrophobic refers to a surface having a contact angle of water of 150 kPa or more, and is a unique surface property present in the leaves of lotus, wings of butterflies, etc. that exist in nature. This property is due to the surface microstructure of the superhydrophobic structure, which is also called the Lotus effect. If the roughness of the superhydrophobic surface is not sufficient, water droplets will fill the rough superhydrophobic surface and fix it. In this case, even when the superhydrophobic surface is tilted a lot, the water droplets are fixed on the superhydrophobic surface and cannot be removed from the superhydrophobic surface. (Wenzel state) However, the superhydrophobic surface has two different sized rugged structures, which makes the surface rough. If is sufficient, the rugged structure of the superhydrophobic surface can be filled with air instead of water. Water droplets on these superhydrophobic surfaces lie on top of the air filling the rugged structure, causing them to roll off easily with slight tilting. (Cassie-Baxter state) ), Water droplets roll down and contaminants attached to the surface of the superhydrophobic film adhere to the surface of the water droplets and are removed together, thus having a function of self-cleaning.

Various methods have been proposed to implement a superhydrophobic coating having such a self-cleaning function. In particular, recently, due to the advantages of the electrospinning that can be easily coated on the desired structure has been made to use the electrospinning to implement a super hydrophobic coating. However, the conventional implementation of superhydrophobic coating using electrospinning only makes areas in which bead-shaped polymers of irregular sizes are aggregated in the middle of nanofibers by adjusting the operating conditions of electrospinning.

The present invention has been made to solve the problems of the prior art as described above, the object of the present invention is to provide a superhydrophobic coating layer made of inorganic particles suitable for self-cleaning, water droplets easily roll down even a little tilt.

Another object of the present invention is to provide a coating composition that is suitable for self-cleaning, and can be used to prepare a superhydrophobic coating layer made of inorganic particles that easily drop water droplets even when tilted slightly.

Another object of the present invention is to provide a method of forming a super hydrophobic coating layer made of inorganic particles suitable for self-cleaning, water droplets easily roll down even if tilted a little.

In order to achieve the above object, the present invention provides a superhydrophobic coating film including nanofibers made of inorganic particles having at least two different diameters.

The present invention also provides a superhydrophobic coating composition in which inorganic particles having at least two different diameters are dispersed in a polymer solution.

In addition, the present invention comprises the steps of electrospinning the superhydrophobic coating composition in which inorganic particles having at least two different diameters are dispersed in the polymer solution to the surface of the substrate to form inorganic particles / polymer composite nanofibers; And it provides a method of forming a super hydrophobic coating layer comprising the step of removing the polymer from the composite nanofibers.

In addition, the present invention comprises the steps of electrospinning the superhydrophobic coating composition in which inorganic particles having at least two different diameters are dispersed in the polymer solution to the surface of the substrate to form inorganic particles / polymer composite nanofibers; Removing the polymer from the composite nanofibers; And surface-treating the nanofibers from which the polymer has been removed with a fluoro-based self-assembled monolayer.

Hereinafter, the content of the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, electrospinning is performed using a solution in which a large inorganic particle of micro size and a small inorganic particle of several tens of nano size are mixed with a polymer solution in order to obtain a superhydrophobic coating film. (See Fig. 1)

Referring to FIG. 1, a mixture of inorganic particles and a polymer solution is injected into a metal capillary connected to a syringe at a constant flow rate through a syringe pump, and a high voltage generated from a high voltage supply is applied to the metal capillary. Initially, a mixture of inorganic particles and a polymer solution formed at the end of a metal capillary tube is formed in a drop shape due to the surface tension. As the applied voltage becomes stronger, the mixture formed at the end of the metal capillary tube is stretched under the electric maxwell stress, and when the electric field is larger than the threshold value, the water droplet at the end of the metal capillary tube is conical. jet mode). At this time, the mixture of the inorganic particles and the polymer solution ejected from the capillary tube is increased by the influence of the electric field while going to the substrate, and gradually becomes thinner as the solvent evaporates. As a result, the polymer nanofibers made by electrospinning act as a confined space of the inorganic particles, thereby making the inorganic material / polymer composite nanofibers.

Thereafter, the inorganic particles / polymer composite nanofibers are selectively removed by heat-treating the polymer that acted as a confined space at about 400 to 600 ° C. The superhydrophobic film having two different sized uneven structures when surface-treated nanofibers composed of inorganic particles having two different sized uneven structures is treated with a fluorine-based self-assembled monolayer. Can be formed.

As the micro-sized particles used in the present invention, all kinds of inorganic particles which can be made in the size of several hundred nanometers to several micrometers can be used. Preferably, silica, titanium oxide, alumina, ceria, zirconium oxide, and the like are used. Can be used. The micro-sized silica particles used in the embodiment of the present invention can be prepared through a multi-step sol-gel reaction using the Stober-Fink-Bohn method. . Particle size and dispersion can be analyzed by scanning electron microscopy and dynamic light scattering, respectively, and the particle size can be obtained from several hundred nanometers to several micrometers with a dispersion of about 0.5%. . In addition to the inorganic particles of a large size that can be produced through the above process may be used commercially available. In addition, the nano-sized particles used in the present invention can be used for all kinds of inorganic particles that can be made to several tens of nano-size, preferably silica, titanium oxide, alumina, ceria and zirconium oxide may be used.

As the polymer solution used in the present invention, all kinds of polymer solutions capable of electrospinning may be used. Preferably, a polymer solution, such as polyethylene oxide, polyacrylamide, polyvinyl alcohol, polyethylene glycol, which is well soluble in water, which easily disperses particles such as silica and titanium oxide without surface modification, may be used, and the surface may be hydrophobic. When modified, a polymer solution such as polyacrylonitrile, polyvinylpyrrolidone, polystyrene, polycaprolactone and polyethylene terephthalate may be used, but is not limited thereto.

In addition, the solvent constituting the polymer solution may be selected from the group consisting of distilled water, ethanol, toluene, dimethylformamide, methanol, tetrahydrofuran, chloroform, isopropyl alcohol, dichloromethane and a mixture of the solvent. The composition of the polymer solution is prepared by considering the molecular weight of the polymer, the dielectric constant of the solvent, the evaporation rate, and the like so that the content of the polymer is 5 to 30 wt% to have a viscosity suitable for electrospinning. 5 to 10 wt% of the, small silica particles are prepared to be 2 to 5 wt%.

In addition, the polymer solution used in the present invention may be further added to the alcohol as a contact angle regulator. The alcohol to be added includes butanol, pentanol, nucleic acidol, heptanol, and the like, which may be added in an amount of 3 to 7 wt% based on the weight of the polymer solution.

According to the present invention, it is possible to control the surface roughness by adjusting the composition of inorganic particles and polymers having different sizes and the collection time of the nanofibers, and thus the contact angle. Increasing the amount of large particles, for example, increases the coarseness, resulting in a larger contact angle. In addition, it is possible to adjust the contact angle by adjusting the collection time of the nanofibers in a few tens of seconds.

The dispersion for forming the superhydrophobic coating prepared by the above process is coated on the surface of the desired substrate using electrospinning. The substrate for coating of the present invention can be used for all kinds of substrates applicable to electrospinning, and preferably, substrates such as copper, aluminum, silicon wafers, tungsten wafers, glass, etc. may be used, but are not limited thereto.

Electrospinning may be performed under a voltage of 5 ~ 30 kV. The distance between the dispersion and the substrate during electrospinning should be 5 to 20 cm.

According to the present invention, a fluoro-based self-assembled monolayer may be used to surface-treat the nanofibers in which the polymer is removed. Fluorinated self-assembled monolayers that can be used in the present invention are Hapta decafluoro-1, 1, 2, 2-tetrahydrodecyltrichlorosilane, heptadecafluorodecyltriethoxysilane, hapta decafluorodecyltrimethoxy Silane, heptadecafluorodecylisopropylsilane, perfluorodecyltrichlorosilane, perfluorodecyltriethoxysilane, and perfluorodecyltrimethoxysilane.

The superhydrophobic coating prepared through the above process may be applied in various fields such as a self-cleaning surface, an antifouling coating, a coating of a microfluidic device and a biosensor, and an antifouling fiber.

Hereinafter, the present invention will be described in detail with reference to the following examples, which do not limit the scope of the present invention.

Example 1 Preparation of Inorganic Particles / Polymer Mixture

In the presence of ammonia and water, sol-gel reaction was carried out using the Stober-Fink-Bohn method, which is a method of condensing tetraethyl orthosilicate, a precursor of silica, with hydrolysis using ethanol as a solvent. Silica particles were prepared through a sol-gel reaction. Particle size and dispersion were analyzed by scanning electron microscopy and dynamic light scattering, respectively, and the particle size was 700 nm and dispersion was 0.5%. The solution was centrifuged and redispersed in 20 wt% in distilled water.

In order to make a bumpy structure having two different sizes, a 50 wt% 35 wt% silica aqueous solution was mixed at a ratio of 25 wt% to a micro sized silica aqueous solution prepared by the above method. In order to adjust the aqueous solution containing two different sizes of silica particles to a viscosity suitable for producing uniform nanofibers by electrospinning, 10 wt% aqueous polyethylene oxide or polyacrylamide solution was mixed at a ratio of 54 wt%. Mixtures of silica particles and polymer solutions of different sizes were prepared.

Example 2 Preparation of Inorganic Nanofibers by Electrospinning

The inorganic particles / polymer aqueous solution prepared by the above method is placed in a glass syringe connected to a metal capillary tube having a diameter of 110 μm, and has a flow rate of 0.1 ml / h to 1.0 ml / h using a syringe pump. To adjust. As shown in Figure 1, while applying a high voltage of 5 ~ 30 kV to the metal capillary using a high voltage supply to observe the change of the inorganic particles / polymer mixture formed on the end of the metal capillary. As is well known in the art, when the shape of the water droplets formed at the end of the metal capillary is changed into the cone cone jet mode, nanofibers having a uniform size distribution can be produced, so that the cone shape can be stably Electrospinning was performed under the conditions maintained. The substrate to be subjected to the superhydrophobic coating was grounded at a distance of 10 cm from the metal capillary tube to form a film made of inorganic particles / polymer composite nanofibers.

In order to selectively remove the polymer used as a limited space for self-assembly of the inorganic particles in the inorganic particle / polymer composite nanofiber film prepared by the above method, only inorganic particles having different sizes were sintered at 500 ° C. for 3 hours. The constructed nanofiber film was prepared.

3 is an electron micrograph before and after the selective removal of polyethylene oxide through the sintering of silica / polyethylene oxide composite nanofibers obtained under the conditions of the flow rate of 0.5 ml / h, the electric field strength of 0.9 kV / cm in the above operating conditions. In the case of polyethylene oxide, 5 wt% of the mass of the silica / polyethylene oxide aqueous solution was added to prepare a stable inorganic particle nanofiber by improving the wettability between the silica particles and the polymer.

Figure 4 is an electron micrograph before and after the selective removal of polyacrylamide through the sintering of silica / polyacrylamide composite nanofibers obtained under the conditions of the flow rate 0.5 ml / h, the electric field strength 0.9 kV / cm in the above operating conditions to be. As can be seen in Figures 3 and 4, using the method of Example 2 it is possible to quickly and easily create a bumpy structure of two different sizes, which is an essential element for implementing a superhydrophobic film.

Example 3 Surface Treatment of Inorganic Nanofibers

Hydroxyl group (-OH) that is easy to chemically bond with the pluor-based self-assembled monolayer on the surface of the inorganic material before the nanofibers composed of the inorganic particles having two different sizes obtained by the above method is treated with the plur-based self-assembled monolayer Exposure to oxygen plasma for 3 minutes. The nanofibers made of the inorganic particles in which the hydroxy group was produced were placed in a container containing Hapta decaflouro-1, 1, 2, and 2-tetrahydrodecyltrichlorosilane and reacted for about 2 hours.

5 is a polymer selection by sintering the silica / polyacrylamide composite nanofibers obtained under the conditions of the flow rate of 0.5 ml / h, the electric field strength of 0.9 kV / cm in the operating conditions of Example 2 using a 4-inch silicon wafer as a substrate After the removal, the surface of the substrate treated by the method of Example 3 is shown. As can be seen in Figure 5, it was relatively easy to superhydrophobic coating on a large area substrate using electrospinning.

FIG. 6 shows silica before and after selective removal of polyacrylamide through sintering of silica / polyacrylamide composite nanofiber made by the method of Example 2, and by surface treatment with a pluoride self-assembled monolayer by the method of Example 3. This is a result of measuring the surface properties of an X-ray photoelectron spectrometer of nanofibers made of particles. As can be seen in Figure 6, after the sintering of the silica / polyacrylamide composite nanofibers, it can be seen that the polyacrylamide was selectively completely removed from the peak value corresponding to N 1S that existed before the sintering disappeared. have. In addition, in the case of nanofibers composed of surface-treated silica particles, it can be seen that the silica nanofibers were well treated with fluoride self-assembled monolayers from peak values corresponding to F 1S and F auger. In addition, it can be confirmed that the unreacted fluoro-based self-assembled monomolecule was well removed from the fact that peak value corresponding to Cl 1S does not exist.

Example 4 Contact Angle Measurement Experiment

In order to measure the contact angle, 10 μl of pure distilled water droplets were dropped on the superhydrophobic film prepared by the above method. FIG. 7 shows contact angle measurement results of surface treatment with a pluoride self-assembled monomolecular film according to the method of Example 3 on a silicon wafer having no structure for comparison and made from polyethylene oxide and polyacrylamide by the method of Examples 2 and 3. FIG. Results of contact angle measurements for superhydrophobic films with two different sized rugged structures. In the comparative experiments, the contact angle of water was 117.0 °, which did not show the superhydrophobic property. However, in the case of the film having the rugged structure having two different sizes according to Examples 2 and 3, the contact angle was 150 ° or more. It can be seen that it has. In addition, in the case of the superhydrophobic film made according to the method of Examples 2 and 3, the angle of falling of the water droplets is very small, less than 2 °, through the present invention can effectively produce a film (Cassie-Baxter state) suitable for self-cleaning It can be seen that.

According to the present invention, by using the polymer nanofibers made by electrospinning as a confined space, the self-assembly of the inorganic particles having two different sizes is suitable for self-cleaning, and the inorganic particles falling easily drop even with a slight tilt The superhydrophobic film consisting of can be effectively produced. In addition, the present invention can be produced in a relatively large amount of nanofibers made of inorganic particles having two different sizes by using electrospinning.

The superhydrophobic coating layer implemented by the present invention can be efficiently applied in various fields such as self-cleaning surface, antifouling coating, coating of microfluidic device and biosensor, antifouling fiber, and the like.

Claims (17)

A superhydrophobic coating film comprising nanofibers made of inorganic particles having at least two different diameters. The superhydrophobic coating film of claim 1, wherein the inorganic particles are selected from the group consisting of silica, titanium oxide, alumina, ceria, and zirconium oxide. A superhydrophobic coating composition in which inorganic particles having at least two different diameters are dispersed in a polymer solution. The superhydrophobic coating composition according to claim 3, wherein the inorganic particles are selected from the group consisting of silica, titanium oxide, alumina, ceria and zirconium oxide. The method of claim 3, wherein the polymer constituting the polymer solution is composed of polyethylene oxide, polyacrylamide, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyvinylpyrrolidone, polystyrene, polycaprolactone and polyethylene terephthalate. Superhydrophobic coating composition selected from the group. 4. The solvent according to claim 3, wherein the solvent constituting the polymer solution is selected from the group consisting of distilled water, ethanol, toluene, dimethylformamide, methanol, tetrahydrofuran, chloroform, isopropyl alcohol, dichloromethane and mixtures of the above solvents. Superhydrophobic coating composition. The superhydrophobic coating composition according to claim 3, wherein an alcohol is further added to the polymer solution as a contact angle regulator. Electrospinning the superhydrophobic coating composition in which inorganic particles having at least two different diameters are dispersed in the polymer solution to the surface of the substrate to form inorganic particles / polymer composite nanofibers; Forming a super hydrophobic coating layer comprising the step of removing the polymer from the composite nanofibers. Electrospinning the superhydrophobic coating composition in which inorganic particles having at least two different diameters are dispersed in the polymer solution to the surface of the substrate to form inorganic particles / polymer composite nanofibers; Removing the polymer from the composite nanofibers; And surface-treating the nanofibers from which the polymer has been removed with a fluoro-based self-assembled monolayer. The method according to claim 8 or 9, wherein the inorganic particles are selected from the group consisting of silica, titanium oxide, alumina, ceria and zirconium oxide. The method of claim 8 or 9, wherein the polymer constituting the polymer solution is polyethylene oxide, polyacrylamide, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, polyvinylpyrrolidone, polystyrene, polycaprolactone and polyethylene Method for forming a super hydrophobic coating layer selected from the group consisting of terephthalate. The method of claim 8 or 9, wherein the solvent constituting the polymer solution is composed of distilled water, ethanol, toluene, dimethylformamide, methanol, tetrahydrofuran, chloroform, isopropyl alcohol, dichloromethane and a mixture of the solvents. Method for forming a super hydrophobic coating layer selected from the group. 10. The method of forming a superhydrophobic coating layer according to claim 8 or 9, wherein alcohol is added to the polymer solution as a contact angle regulator. 10. The method according to claim 8 or 9, wherein the contact angle is controlled by adjusting the composition of inorganic particles and polymers having different sizes and the collection time of the nanofibers. 10. The method of claim 8 or 9, wherein the electrospinning is carried out under a voltage of 5 ~ 30kV. The method of forming a superhydrophobic coating layer according to claim 8 or 9, wherein the distance between the dispersion and the substrate is 5 to 20 cm during electrospinning. 10. The method of claim 9, wherein the fluorine-based self-assembled monolayer is Hapta decafluoro-1, 1, 2, 2-tetrahydrodecyltrichlorosilane, heptadecafluorodecyltriethoxysilane, hapta decafluorodecyltrimethoxy Method for forming a super hydrophobic coating layer selected from the group consisting of silane, heptadecafluorodecylisopropylsilane, perfluorodecyltrichlorosilane, perfluorodecyltriethoxysilane and perfluorodecyltrimethoxysilane.

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