US20170015483A1

US20170015483A1 - Graphene oxide nanocomposite membrane having improved gas barrier characteristics and method for manufacturing the same

Info

Publication number: US20170015483A1
Application number: US15/123,967
Authority: US
Inventors: Ho Bum Park; Hyo Won Kim; Byung Min Yoo; Seung Jin JANG
Original assignee: Industry University Cooperation Foundation IUCF HYU
Current assignee: Industry University Cooperation Foundation IUCF HYU
Priority date: 2014-03-07
Filing date: 2015-03-06
Publication date: 2017-01-19
Also published as: KR20150105236A; CN106061593A; KR101972439B1; CN106061593B

Abstract

The present invention relates to a technique of manufacturing a graphene oxide nanocomposite membrane in which 3 μm to 5 μm-sized graphene oxide is coated with a thickness of 10 nm or more on various supports, or a graphene oxide nanocomposite membrane having a structure in which graphene oxide is inserted into a polymer. The graphene oxide nanocomposite membrane manufactured according to the present invention has excellent barrier characteristics against various gases even when graphene oxide, of which the size is controlled to 3 μm to 5 μm, is coated as a nanometer-thick thin film on various supports or the graphene oxide nanocomposite membrane has a simple structure in which graphene oxide is inserted into a polymer, and thus the graphene oxide nanocomposite membrane can be applied to the packaging of display devices, food, and medical products.

Description

TECHNICAL FIELD

The present invention relates to a graphene oxide nanocomposite membrane with improved gas barrier characteristics and a method for manufacturing the same. More specifically, the present invention relates to a method of manufacturing a nanocomposite membrane including 3 μm to 50 μm-sized graphene oxide coated to a thickness of 10 nm or more on various supports, or a graphene oxide nanocomposite membrane having a structure in which graphene oxide is inserted into a polymer, wherein the nanocomposite membranes exhibit excellent barrier characteristics against various gases and thus can be applied to packaging of display devices, food and medical products.

BACKGROUND ART

Graphene is a substance composed of a single carbon atom layer in the form of a hexagonal honeycomb, which has most been in the highlight in industry and academia since it was first discovered in 2004, because it is quite interesting and exhibits excellent physical and chemical properties owing to the structural characteristic, so-called “two-dimensional lamella structure”. That is, graphene is the thinnest substance in the world, but has 200 times or more stronger mechanical properties than steel, 100 times or more higher current permeability than copper and 100 times or more faster electron mobility than silicon. In particular, graphene is known to exhibit excellent barrier characteristics against gas and ion molecules owing to superior mechanical strength in spite of being a single atomic layer.
However, excellent barrier characteristics against gas and ion molecules of graphene can be only realized by a graphene structure that is free from defects. When defects are generated in graphene, gas and ion molecules are easily permeated into defective graphene parts and inherent barrier characteristics thereof are thus lost. For this reason, when graphene is formed as a thin film, disadvantageously, it cannot maintain barrier characteristics against gas and ion molecules.
A variety of technologies related to barrier characteristics of graphene against gas and ion molecules have been developed. Recently, there was made an attempt to produce a graphene laminate barrier film including at least one graphene laminate including a hydrophilic graphene layer and a hydrophobic graphene layer, wherein the graphene layer has a controlled thickness of 0.01 μm to 1,000 μm, and apply the same to food packaging using barrier characteristics thereof. However, the structure of the graphene laminate film is slightly complicated and only data showing oxygen and water vapor permeability is shown and barrier characteristics thereof against various gases are not known to date (Patent Document 1).
In addition, graphene/polymer composite protective membranes including a plurality of graphene layers and a plurality of polymer layers between the respective graphene layers are known, but it is only disclosed that the graphene composite membranes have complex structures and are applicable as gas and water barriers, and detailed results associated with gas barrier characteristics of the graphene composite membranes are not disclosed and practical application of the graphene composite membranes to the industry is limited (Patent Document 2).
In addition, a gas diffusion barrier including a polymer matrix and functionalized graphene having a surface area of 300 to 2,600 m²/g and a bulk density of 40 to 0.1 kg/m³is also known. The gas diffusion barrier is characterized in that the surface area and bulk density of functionalized graphene are controlled. The gas diffusion barrier is a thick membrane in which functionalized graphene is dispersed in the polymer matrix. In a case in which the gas diffusion barrier is a thin film, whether or not the gas diffusion barrier has gas barrier characteristics cannot be expected, and actions and effects demonstrated by qualitative data associated with gas barrier characteristics are not described in detail (Patent Document 3).
In addition, research on graphene/polyurethane nanocomposites in which graphite oxide as a nano-filler is incorporated into thermoplastic polyurethane by melt mixing, solution blending or simultaneous polymerization, and gas barrier characteristics thereof is also known. Barrier characteristics against a nitrogen gas depending on the amount of graphene present as a filler in thermoplastic polyurethane was found, but barrier characteristics against various gases depending on control of the size of graphene oxide and of thickness of graphene oxide film are not known (Non-patent Document 1).

PRIOR ART DOCUMENT

Patent Document

Patent Document 1. Korean Patent Laid-open Publication No. 10-2014-0015926
Patent Document 2. Korean Patent Laid-open Publication No. 10-2013-0001705
Patent Document 3. US Patent Laid-open Publication No. US 2010/0096595

Non-Patent Document

Non-patent Document 1. Hyunwoo Kim et al., Chem. Mater. 22, 3441-3450(2010)

DISCLOSURE

Technical Problem

Therefore, it is an object of the present invention to provide a graphene oxide nanocomposite membrane which exhibits excellent gas barrier characteristics against various gases, although it includes graphene oxide with a controlled size coated in the form of a nano-scale thin film on a support, or has a simple structure in which graphene oxide is inserted into a polymer, and a method of manufacturing the same.

Technical Solution

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a graphene oxide nanocomposite membrane with gas barrier characteristics including a support and a coating layer including 3 μm to 50 μm-sized graphene oxide coated to a thickness of 10 nm or more on the support and having nanopores.
The support may include any one selected from the group consisting of polymer, ceramic, glass, paper and metal layers.
The polymer may include any one selected from the group consisting of polyester, polyolefin, polyvinyl chloride, polyurethane, polyacrylate, polycarbonate, polytetrafluoroethylene, polysulfone, polyether sulfone, polyimide, polyether imide, polyamide, polyacrylonitrile, cellulose acetate, cellulose triacetate and polyvinylidene fluoride.
The ceramic may include any one selected from the group consisting of alumina, magnesia, zirconia, silicon carbide, tungsten carbide and silicon nitride.
The metal layer may be a metal foil, a metal sheet or a metal film.
The metal layer may include any one material selected from the group consisting of copper, nickel, iron, aluminum and titanium.
The graphene oxide may be functionalized graphene oxide in which a hydroxyl group, a carboxyl group, a carbonyl group or an epoxy group present in graphene oxide is converted into an ester group, an ether group, an amide group or an amino group.
The nanopores may have a mean diameter of 0.5 nm to 1.0 nm.
The coating layer may include graphene oxide including a single layer or multiple layers.
The graphene oxide including a single layer may have a thickness of 0.6 nm to 1 nm.
In another aspect of the present invention, provided is a graphene oxide nanocomposite membrane with gas barrier characteristics having a structure in which graphene oxide is inserted into a polyethylene glycol diacrylate or polyethylene glycol dimethacrylate polymer.
The graphene oxide may have a size of 100 to 1000 nm.
The graphene oxide may be present in an amount of 5% by weight in the nanocomposite membrane.
In another aspect of the present invention, provided is a display device including the graphene oxide nanocomposite membrane with gas barrier characteristics.
In another aspect of the present invention, provided is a food packaging material including the graphene oxide nanocomposite membrane with gas barrier characteristics.
In another aspect of the present invention, provided is a medical product packaging material including the graphene oxide nanocomposite membrane with gas barrier characteristics.
In another aspect of the present invention, provided is a method of manufacturing a graphene oxide nanocomposite membrane with gas barrier characteristics including i) dispersing graphene oxide in distilled water and treating the dispersion with an ultrasonic grinder for 0.1 to 6 hours to obtain a graphene oxide dispersion, ii) centrifuging the dispersion to form graphene oxide having a controlled size of 3 μm to 50 μm, iii) dispersing the graphene oxide formed in step ii) in distilled water again to obtain a graphene oxide dispersion, and iv) coating a support with the dispersion obtained in step iii) to form a coating layer having nanopores.
The graphene oxide may be functionalized graphene oxide in which a hydroxyl group, a carboxyl group, a carbonyl group or an epoxy group present in graphene oxide is converted into an ester group, an ether group, an amide group or an amino group.
The support may include any one selected from the group consisting of polymer, ceramic, glass, paper and metal layers.
The polymer may include any one selected from the group consisting of polyester, polyolefin, polyvinyl chloride, polyurethane, polyacrylate, polycarbonate, polytetrafluoroethylene, polysulfone, polyether sulfone, polyimide, polyether imide, polyamide, polyacrylonitrile, cellulose acetate, cellulose triacetate and polyvinylidene fluoride.
The ceramic may include any one selected from the group consisting of alumina, magnesia, zirconia, silicon carbide, tungsten carbide and silicon nitride.
The metal layer may be a metal foil, a metal sheet or a metal film.
The metal layer may include any one material selected from the group consisting of copper, nickel, iron, aluminum and titanium.
The coating may be carried out by any one method selected from the group consisting of direct evaporation, transfer, spin coating and spray coating.
The spin coating may be conducted three to ten times.
The nanopores may have a mean diameter of 0.5 nm to 1.0 nm.
The coating layer may include graphene oxide including a single layer or multiple layers.
The graphene oxide including a single layer may have a thickness of 0.6 nm to 1 nm.

Effects of the Invention

The graphene oxide nanocomposite membrane manufactured according to the present invention has excellent barrier characteristics against various gases even when graphene oxide, the size of which is controlled to 3 μm to 50 μm, is coated as a nanometer-thick thin film on various supports or the graphene oxide nanocomposite membrane has a simple structure in which graphene oxide is inserted into a polymer, and thus the graphene oxide nanocomposite membranes can be applied to the packaging of display devices, food and medical products.

DESCRIPTION OF DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a structure of graphene oxide and a structure of functionalized graphene oxide;

FIG. 2 is a transmission electron microscope (TEM) image showing graphene oxide having a controlled size according to Example 1;

FIG. 3 is an image showing a graphene oxide nanocomposite membrane produced in Example 1;

FIG. 4 is a transmission electron microscope (TEM) image showing a cross-section of a graphene oxide film coated on a polymer support (PES) according to Example 1;

FIG. 5 is an image showing a graphene oxide nanocomposite membrane depending on the content of graphene oxide produced in Example 2 (graphene oxide size: 270 nm);

FIG. 6 is a scanning electron microscope (SEM) image showing a graphene oxide nanocomposite membrane depending on the content of graphene oxide produced in Example 2 (graphene oxide size: 270 nm).

FIG. 7 is an image showing a graphene oxide nanocomposite membrane depending on the size of graphene oxide produced in Example 2 (graphene oxide content: 4% by weight);

FIG. 8 is a schematic view showing a configuration of a constant pressure/variable volume gas measurement device equipped with a gas chromatography apparatus;

FIG. 9 is a graph showing gas barrier characteristics and gas permeation pressures of an ultrathin film graphene oxide film depending on the size of graphene oxide;

FIG. 10 is a scanning electron microscope (SEM) image showing a graphene oxide film with a thickness of about 5 μm produced by ordinary vapor filtration;

FIG. 11 is a graph showing gas barrier characteristics of the graphene oxide film produced by ordinary vapor filtration depending on size of graphene oxide;

FIG. 12 is a graph showing theoretical gas barrier characteristics depending on the size of graphene oxide and the thickness of the graphene oxide thin film;

FIG. 13 is a graph showing oxygen permeability of graphene oxide nanocomposite membrane depending on the content of graphene oxide produced in Example 2 (graphene oxide size: 270 nm); and

FIG. 14 is a graph showing oxygen permeability of graphene oxide nanocomposite membrane depending on the size of graphene oxide produced in Example 2 (graphene oxide content: 4% by weight).

BEST MODE

Hereinafter, the nanocomposite membrane in which 3 μm to 50 μm-sized graphene oxide is coated to a thickness of 10 nm or more on various supports and the method of manufacturing the same according to the present invention will be described in detail with reference to the annexed drawings.
First, the support can be made of a variety of substances which function as a reinforcing material to support the coating layer and contact the coating layer, and the support may include any one selected from the group consisting of polymer, ceramic, glass, paper and metal layers. In particular, the polymer includes any one selected from the group consisting of polyester, polyolefin, polyvinyl chloride, polyurethane, polyacrylate, polycarbonate, polytetrafluoroethylene, polysulfone, polyether sulfone, polyimide, polyether imide, polyamide, polyacrylonitrile, cellulose acetate, cellulose triacetate and polyvinylidene fluoride, but is not limited thereto. Among these polymers, polyether sulfone is more preferably used, but the polymer is not limited thereto.
In addition, the ceramic support includes any one selected from the group consisting of alumina, magnesia, zirconia, silicon carbide, tungsten carbide, silicon nitride and silicon nitride, and the ceramic support is preferably alumina or silicon carbide.
In addition, when the support is formed of a metal layer, the metal layer may have various forms such as a metal foil, a metal sheet and a metal film. The material for the metal layer may include any one selected from the group consisting of copper, nickel, iron, aluminum and titanium.
Next, the coating layer having nanopores in which 3 μm to 50 μm-sized graphene oxide is coated to a thickness of nm or more on various supports will be described in detail.
The graphene oxide used for the present invention can be mass-produced by oxidizing graphite using an oxidant and includes a hydrophilic functional group such as a hydroxyl group, a carboxyl group, a carbonyl group or an epoxy group. At present, most graphene oxide is manufactured by Hummers' method [Hummers, W. S. & Offeman, R. E. Preparation of graphite oxide. J. Am. Chem. Soc. 80. 1339(1958)] or a partially modified version of Hummers' method. In the present invention, graphene oxide is obtained by Hummers' method as well.
In addition, the graphene oxide of the present invention may be functionalized graphene oxide in which a hydrophilic functional group such as a hydroxyl group, a carboxyl group, a carbonyl group or an epoxy group present in the graphene oxide is converted into an ester group, an ether group, an amide group or an amino group by chemical reaction with other compounds and examples thereof include functionalized graphene oxide in which a carboxyl group of graphene oxide is reacted with alcohol and is thus converted into an ester group, functionalized graphene oxide in which a hydroxyl group of graphene oxide is reacted with alkyl halide and is thus converted into an ester group, functionalized graphene oxide in which a carboxyl group of graphene oxide is reacted with alkyl amine and is thus converted into an amide group, and functionalized graphene oxide in which an epoxy group of graphene oxide is ring-opening reacted with alkyl amine and is thus converted into an amino group.
Regarding the size of graphene oxide, as the size thereof increases, gas barrier characteristics increase. When the size thereof is less than 50 μm, gas permeation is obtained, opposite to barrier characteristics. In the present invention, barrier characteristics against gases can be improved by controlling the thickness of graphene oxide, although the size of graphene oxide is controlled below 50 μm. Thus, the size of the graphene oxide is controlled to 50 μm or less. In a case in which the size of graphene oxide is excessively small, it is difficult to maintain barrier characteristics against various gases having different molecular sizes. Accordingly, the size should be controlled to 3 μm or more. That is, in order for the graphene oxide thin film according to the present invention to exhibit excellent barrier characteristics against various gases having different molecular sizes, the size of graphene oxide is preferably controlled within the range of 3 μm to 50 μm, particularly preferably the range of 3 μm to 10 μm because graphene oxide exhibits excellent gas barrier characteristics although it is formed as an ultrathin film. FIG. 1 shows a structure of graphene oxide obtained by Hummers' method from graphite and a structure of functionalized graphene oxide produced by reacting graphene oxide with other compounds.
Meanwhile, according to the present invention, the graphene oxide coating layer formed on various supports includes graphene oxide having a single layer or multiple layers, and graphene oxide having a single layer has a thickness of 0.6 nm to 1 nm. In addition, graphene oxide having a single layer may be laminated to form graphene oxide having multiple layers. An additional movement route is formed between grain boundaries due to small distance between graphene oxide layers of about 0.34 nm to 0.5 nm, and barrier characteristics against various gases having different molecular sizes can be improved by controlling the pore and channel size between grain boundaries. Accordingly, the graphene oxide coating layer more preferably includes graphene oxide having multiple layers.
As the thickness of the graphene oxide coating layer increases, gas barrier characteristics thereof are improved. As described above, in the present invention, when the size of graphene oxide is controlled to the range of 3 μm to 50 μm, although a graphene oxide coating layer is formed as an ultrathin film having a thickness of at least 10 nm, it can exhibit gas barrier characteristics. Accordingly, the thickness of graphene oxide coating layer is preferably 10 nm or more. Furthermore, the graphene oxide coating layer forms nanopores having a mean diameter of 0.5 nm to 1.0 nm.
In addition, in addition to the gas barrier graphene oxide nanocomposite membrane including graphene oxide coated on various supports including polymer supports as described above, the present invention provides a graphene oxide nanocomposite membrane with gas barrier characteristics having a structure in which graphene oxide is inserted into polyethylene glycol diacrylate or a polyethylene glycol dimethacrylate polymer.
That is, in the polymerization, into a polymer, of the polyethylene glycol diacrylate or polyethylene glycol dimethacrylate macromer having a carbon-carbon double bond at an end thereof, and in the formation of a cross-linked structure, graphene oxide as a filler is inserted into the polymer, thereby further improving gas barrier effects. In this case, the polyethylene glycol diacrylate or polyethylene glycol dimethacrylate macromer preferably has a number average molecular weight (Mn) of 250 to 1000 in terms of UV polymerization using a photoinitiator and formation of a cross-linked structure.
In addition, the graphene oxide preferably has a size of 100 to 1,000 nm. When the size of graphene oxide is less than 100 nm, gas barrier characteristics may be deteriorated and when the size thereof exceeds 1,000 nm, the graphene oxide may not be uniformly inserted and dispersed in the polyethylene glycol diacrylate or polyethylene glycol dimethacrylate polymer having a cross-linked structure.
In addition, the amount of graphene oxide present in the graphene oxide nanocomposite membrane with gas barrier characteristics having a structure in which graphene oxide is inserted into the polyethylene glycol diacrylate or polyethylene glycol dimethacrylate polymer is preferably less than 5 wt % because an effect of reducing gas permeability can be maximized.
In addition, the present invention provides a method of manufacturing a graphene oxide nanocomposite membrane with gas barrier characteristics, including: i) dispersing graphene oxide in distilled water and treating the dispersion with an ultrasonic grinder for 0.1 to 6 hours to obtain a graphene oxide dispersion, ii) centrifuging the dispersion to form graphene oxide having a controlled size of 3 μm to 50 μm, iii) dispersing the graphene oxide formed in step ii) in distilled water again to obtain a graphene oxide dispersion, and iv) coating a support with the dispersion obtained in step iii) to form a coating layer having nanopores.
The graphene oxide in step i) may be functionalized graphene oxide in which a hydroxyl group, a carboxyl group, a carbonyl group or an epoxy group present in graphene oxide is converted into an ester group, an ether group, an amide group, or an amino group.
In addition, in step i), the graphene oxide is dispersed in distilled water and then treated with an ultrasonic grinder for 0.1 to 6 hours to obtain a graphene oxide dispersion, thereby improving dispersibility of graphene oxide in the dispersion. In addition, the dispersion obtained in step iii) is a 0.01 to 0.5 wt % aqueous graphene oxide solution which has pH adjusted to 10.0 with a 1M aqueous sodium hydroxide solution. When the concentration of the aqueous graphene oxide solution is less than 0.01 wt %, it is disadvantageously difficult to obtain the uniform coating layer and, when the concentration thereof exceeds 0.5 wt %, coating cannot be disadvantageously efficiently conducted due to excessively high viscosity. Thus, the concentration of the aqueous graphene oxide solution is preferably 0.01 to 0.5 wt %.
In addition, in step iv), the support can be made of a variety of substances which function as a reinforcing material to support the coating layer and contact the coating layer, and the support may be made of any one selected from the group consisting of polymer, ceramic, glass, paper and metal layers. In particular, the polymer includes any one selected from the group consisting of polyester, polyolefin, polyvinyl chloride, polyurethane, polyacrylate, polycarbonate, polytetrafluoroethylene, polysulfone, polyether sulfone, polyimide, polyether imide, polyamide, polyacrylonitrile, cellulose acetate, cellulose triacetate and polyvinylidene fluoride, but the polymer is not limited thereto. Among these polymers, polyether sulfone is more preferably used, but the polymers are not limited thereto.
In addition, the ceramic support includes any one selected from the group consisting of alumina, magnesia, zirconia, silicon carbide, tungsten carbide and silicon nitride, and the ceramic support is preferably alumina or silicon carbide.
In addition, when the support is formed of a metal layer, the metal layer may have various forms such as a metal foil, a metal sheet or a metal film. The material for the metal layer may include any one selected from the group consisting of copper, nickel, iron, aluminum and titanium.
In step iv), any well-known coating method may be used for forming the coating layer without imitation and the coating method is preferably selected from the group consisting of direct evaporation, transfer, spin coating method, and spray coating. Among these methods, spin coating is more preferable because a uniform coating layer can be easily obtained.
Spin coating is preferably conducted 3 to 10 times. When spin coating is conducted less than three times, the function of a gas barrier layer cannot be disadvantageously obtained and, when the spin coating is conducted 10 times or more, a uniform coating layer cannot be disadvantageously obtained due to excessive thickness of the coating layer.
In step iv), the coating layer may include graphene oxide with a single layer or multiple layers and the graphene oxide with a single layer may have a thickness of 0.6 nm to 1 nm. The graphene oxide coating layer forms nanopores having a mean diameter of 0.5 nm to 1.0 nm.

MODE FOR INVENTION

Hereinafter, specific examples will be described in detail.

Example 1

Graphene oxide prepared by Hummers' method was distilled in distilled water and treated with an ultrasonic grinder for 3 hours to obtain a graphene oxide dispersion. The dispersion was centrifuged to form graphene oxide having a controlled size of 3 μm and the graphene oxide was dispersed in distilled water again to obtain a 0.1 wt % aqueous graphene oxide solution having a pH adjusted to 10.0 with a 1M aqueous sodium hydroxide solution. 1 mL of the aqueous graphene oxide solution was spin-coated on a porous polyether sulfone (PES) support 5 times to produce a graphene oxide nanocomposite membrane having a graphene oxide coating layer with a thickness of 10 nm.

Example 2

A polyethylene glycol diacrylate (PEGDA) macromer (having number average molecular weight of 250) was mixed with deionized water in a weight ratio of 7:3 and stirred for 12 hours to obtain a homogenous solution. 1% by weight of graphene oxide prepared by Hummers' method and 0.1% by weight of hydroxycyclohexyl phenyl ketone as a photoinitiator with respect to the weight of the PEGDA macromer were added to the solution, and the resulting mixture was ultrasonicated for 2 hours and stirred for 24 hours to obtain a precursor solution. The precursor solution was cast on a glass plate and 312 nm UV was applied thereto under a nitrogen atmosphere for 5 minutes to produce a graphene oxide nanocomposite membrane (at this time, graphene oxide had a size of 270 nm or 800 nm and the content thereof was changed to 1, 2, 3, and 4% by weight with respect to the weight of the PEGDA macromer).

Test Example

Gas barrier characteristics of graphene oxide nanocomposite membranes produced in Examples 1 and 2 were measured with a constant pressure/variable volume gas measurement device equipped with a gas chromatography apparatus.
FIG. 2 shows a transmission electron microscope (TEM) image of graphene oxide obtained by centrifuging a graphene oxide dispersion according to an example of the present invention and it can be seen that the size thereof was controlled to about 3 μm.
The camera image of FIG. 3 shows that the graphene oxide nanocomposite membrane produced according to an example of the present invention includes a graphene oxide coating layer formed on a polyether sulfone support.
FIG. 4 is a transmission electron microscope (TEM) image showing a cross-section of a graphene oxide film coated to a thickness of 10 nm on a porous polyether sulfone (PES) support according to an example of the present invention. From FIG. 4, it can be seen that graphene oxide was uniformly laminated.
Meanwhile, as can be seen from the image of FIG. 5, showing a graphene oxide nanocomposite membrane depending on the content of graphene oxide produced in Example 2 (size of graphene oxide: 270 nm), as the content of graphene oxide increases, the color becomes darker. This means that the content of graphene oxide increases and graphene oxide is uniformly dispersed and inserted in a PEGDA polymer having a cross-linked structure.
In addition, as can be seen from the scanning electron microscope (SEM) image of FIG. 6, showing a graphene oxide nanocomposite membrane depending on the content of graphene oxide produced in Example 2 (size of graphene oxide: 270 nm), a PEGDA polymer (pristine PEG) membrane containing no graphene oxide has a smooth surface, whereas a composite membrane containing graphene oxide (2 wt % GO and 4 wt % GO) has a layer structure including graphene oxide.
Furthermore, as can be seen from the image of FIG. 7, showing a graphene oxide nanocomposite membrane depending on the size of graphene oxide produced in Example 2 (graphene oxide content: 4% by weight), although the size of graphene oxide increases from 270 nm to 800 nm, graphene oxide is uniformly dispersed and inserted in a PEGDA polymer having a cross-linked structure.
In addition, gas barrier characteristics of the graphene oxide film according to the present invention were evaluated with a constant pressure/variable volume gas measurement device equipped with a gas chromatography apparatus, as shown in FIG. 8. From FIG. 9, it can be seen that, as the size of graphene oxide increases, a pressure at which gas permeation begins gradually increases, in particular, in a case in which a thin film is produced using graphene oxide having a size of 3.0 μm (=3000 nm), gas cannot be permeated even upon application of a relatively high pressure (180 mbar).
Meanwhile, in order to confirm the size of graphene oxide and the thickness of the graphene oxide thin film which have an effect on gas barrier characteristics of the graphene oxide thin film depending on presence of the support, a graphene oxide film having no support was produced by an ordinary vapor filtration method. FIG. 10 shows a scanning electron microscope (SEM) image of a graphene oxide film with a thickness of about 5 μm produced by an ordinary vapor filtration method. As can be seen from the image, graphene oxide having a two-dimensional structure was laminated without any voids.
In addition, FIG. 11 shows gas barrier characteristics of a graphene oxide film, in which graphene oxide was controlled to have certain sizes (0.5, 1.0 and 5.0 μm), produced by an ordinary vapor filtration method. As can be seen from FIG. 11, as the size of graphene oxide increases, gas permeability was changed to gas barrier characteristics and in particular, gas barrier characteristics are excellent, when the size of graphene oxide is 3.0 μm or more. This indicates that gas barrier characteristics can be improved by controlling the size of graphene oxide without any support.
Furthermore, FIG. 12 is a graph showing theoretical gas permeation channel lengths of graphene oxide films having various sizes at the same thickness. As can be seen from FIG. 12, as the size of graphene oxide increases at the same thickness, the gas permeation channel length gradually increases, and when a film is produced using graphene oxide having a certain size (3.0 μm), gas permeation channel length increases and superior gas barrier characteristics are obtained. This corresponds to measurement results of Test Example according to the present invention.
In addition, FIG. 13 shows a graph showing oxygen permeability of the graphene oxide nanocomposite membrane depending on the content of graphene oxide produced in Example 2 (graphene oxide size: 270 nm). As can be seen from FIG. 13, as the content of graphene oxide increases, oxygen permeability gradually decreases, and in particular, when the amount of graphene oxide present in the graphene oxide nanocomposite membrane is 4% by weight, oxygen permeability is decreased to 83% as compared to the PEGDA polymer (pristine PEG) membrane containing no graphene oxide.
In addition, FIG. 14 is a graph showing oxygen permeability of a graphene oxide nanocomposite membrane depending on the size of graphene oxide produced in Example (graphene oxide content: 4% by weight). As can be seen from FIG. 14, as the size of graphene oxide increases, gas barrier characteristics are gradually improved, and in particular, when the size of graphene oxide inserted into the graphene oxide nanocomposite membrane is 800 nm, oxygen permeability was decreased to 90% as compared to the PEGDA polymer (pristine PEG) membrane containing no graphene oxide.

INDUSTRIAL APPLICABILITY

Accordingly, the graphene oxide nanocomposite membrane manufactured according to the present invention has excellent barrier characteristics against various gases even when graphene oxide, the size of which is controlled to 3 μm to 5 μm, is coated as a nanometer-thick thin film on various supports or the graphene oxide nanocomposite membrane has a simple structure in which graphene oxide is inserted into a polymer, and thus the graphene oxide nanocomposite membrane can be applied to the packaging of display devices, food and medical products.

Claims

1. A graphene oxide nanocomposite membrane with gas barrier characteristics comprising:

a support; and

a coating layer comprising 3 μm to 50 μm-sized graphene oxide coated to a thickness of 10 nm or more on the support and having nanopores.

2. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 1, wherein the support comprises any one selected from the group consisting of polymer, ceramic, glass, paper and metal layers.

3. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 2, wherein the polymer comprises any one selected from the group consisting of polyester, polyolefin, polyvinyl chloride, polyurethane, polyacrylate, polycarbonate, polytetrafluoroethylene, polysulfone, polyether sulfone, polyimide, polyether imide, polyamide, polyacrylonitrile, cellulose acetate, cellulose triacetate and polyvinylidene fluoride.

4. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 2, wherein the ceramic comprises any one selected from the group consisting of alumina, magnesia, zirconia, silicon carbide, tungsten carbide and silicon nitride.

5. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 2, wherein the metal layer is a metal foil, a metal sheet or a metal film.

6. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 5, wherein the metal layer comprises any one material selected from the group consisting of copper, nickel, iron, aluminum and titanium.

7. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 1, wherein the graphene oxide is functionalized graphene oxide in which a hydroxyl group, a carboxyl group, a carbonyl group or an epoxy group present in graphene oxide is converted into an ester group, an ether group, an amide group or an amino group.

8. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 1, wherein the nanopores have a mean diameter of 0.5 nm to 1.0 nm.

9. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 1, wherein the coating layer comprises graphene oxide including a single layer or multiple layers.

10. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 9, wherein the graphene oxide including a single layer has a thickness of 0.6 nm to 1 nm.

11. A graphene oxide nanocomposite membrane with gas barrier characteristics having a structure in which graphene oxide is inserted into a polyethylene glycol diacrylate or polyethylene glycol dimethacrylate polymer.

12. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 11, wherein the graphene oxide has a size of 100 to 1000 nm.

13. The graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 11, wherein graphene oxide is present in an amount of 5% by weight in the nanocomposite membrane.

14. A method of manufacturing a graphene oxide nanocomposite membrane with gas barrier characteristics comprising:

i) dispersing graphene oxide in distilled water and treating the dispersion with an ultrasonic grinder for 0.1 to 6 hours to obtain a graphene oxide dispersion;

ii) centrifuging the dispersion to form graphene oxide having a controlled size of 3 μm to 50 μm;

iii) dispersing the graphene oxide formed in step ii) in distilled water again to obtain a graphene oxide dispersion; and

iv) coating a support with the dispersion obtained in step iii) to form a coating layer having nanopores.

15. The method according to claim 14, wherein the graphene oxide is functionalized graphene oxide in which a hydroxyl group, a carboxyl group, a carbonyl group or an epoxy group present in graphene oxide is converted into an ester group, an ether group, an amide group or an amino group.

16. The method according to claim 14, wherein the support comprises any one selected from the group consisting of polymer, ceramic, glass, paper and metal layers.

17. The method according to claim 16, wherein the polymer comprises any one selected from the group consisting of polyester, polyolefin, polyvinyl chloride, polyurethane, polyacrylate, polycarbonate, polytetrafluoroethylene, polysulfone, polyether sulfone, polyimide, polyether imide, polyamide, polyacrylonitrile, cellulose acetate, cellulose triacetate and polyvinylidene fluoride.

18. The method according to claim 16, wherein the ceramic comprises any one selected from the group consisting of alumina, magnesia, zirconia, silicon carbide, tungsten carbide and silicon nitride.

19. The method according to claim 16, wherein the metal layer is a metal foil, a metal sheet or a metal film.

20. The method according to claim 19, wherein the metal layer comprises any one material selected from the group consisting of copper, nickel, iron, aluminum and titanium.

21. The method according to claim 14, wherein the coating is carried out by any one method selected from the group consisting of direct evaporation, transfer, spin coating and spray coating.

22. The method according to claim 21, wherein the spin coating is conducted three to ten times.

23. The method according to claim 14, wherein the nanopores have a mean diameter of 0.5 nm to 1.0 nm.

24. The method according to claim 14, wherein the coating layer comprises graphene oxide including a single layer or multiple layers.

25. The method according to claim 24, wherein the graphene oxide including a single layer has a thickness of 0.6 nm to 1 nm.

26. A display device comprising the graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 1.

27. A food packaging material comprising the graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 1.

28. A medical product packaging material comprising the graphene oxide nanocomposite membrane with gas barrier characteristics according to claim 1.