KR20170112327A - Method for preparation of polymer-graphene hybrid - Google Patents

Abstract

The method of producing graphene according to the present invention is characterized in that graphene precursor is treated by an electrochemical method and at the same time polyvinylpyrrolidone is formed on the surface of graphene, It has a feature that it can give functionality to graphene.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of preparing a polymer-graphene hybrid,

The present invention relates to a method for producing a polymer-graphene hybrid using a method of electrochemically treating a graphene precursor.

Graphene is a semimetallic material with a thickness corresponding to the carbon atomic layer, with the carbon atoms forming a hexagonally connected arrangement in two dimensions on the sp2 bond. Recently, evaluation of the characteristics of a graphene sheet having one carbon atom layer has revealed that the electron mobility is about 50,000 cm ² / Vs or more, which can exhibit a very good electric conductivity.

Graphene also has structural, chemical stability and excellent thermal conductivity characteristics. In addition, it is easy to process one- or two-dimensional nanopatterns composed of carbon, which is a relatively light element. Graphene is expected to replace silicon-based semiconductor technology and transparent electrodes due to its electrical, structural, chemical, and economic properties, and it is expected to be applicable to flexible electronic devices due to its excellent mechanical properties.

Due to the many advantages and excellent properties of such graphenes, various methods have been proposed or studied to more effectively produce graphene from carbon-based materials such as graphite. Particularly, there have been various studies on a method for easily producing a graphene sheet or flake having a thinner thickness and a larger area so that excellent characteristics of graphene can be more dramatically developed. Such conventional methods of producing graphene include the following.

First, a method of peeling a graphene sheet from graphite by a physical method such as using a tape is known. However, this method is not suitable for mass production methods, and the peeling yield is also very low.

There is known a method for obtaining graphene or an oxide thereof which is peeled off from an intercalation compound in which an acid, a base, a metal or the like is interposed between carbon layers of graphite, or by peeling by a chemical method such as oxidizing graphite.

However, in the former method, a large number of defects may be generated on the finally produced graphene in the process of oxidizing the graphite to proceed the exfoliation and reducing the graphene oxide obtained therefrom to obtain graphene again. This may adversely affect the properties of the final produced graphene. In addition, the latter method requires additional processes such as using and treating an intercalation compound, which may complicate the overall process, resulting in a low yield and a low cost. Further, in this method, it is not easy to obtain a large-area graphene sheet or flake.

Recently, a method of producing graphene by separating carbon layers contained in graphite by ultrasonic irradiation or a milling method using a ball mill or the like has been applied most recently in the state where graphite or the like is dispersed in a liquid state. However, these methods have also been problematic in that it is difficult to obtain graphene having a sufficiently thin thickness and a large area, a large number of defects are formed on the graphene in the peeling process, or the yield of peeling is insufficient. As a result, there is a continuing need for a manufacturing method capable of easily producing a graphene sheet or flake having a thinner thickness and a larger area with higher yield. Further, graphene is not well dispersed in a hydrophilic solvent as a hydrogenated material, and therefore, there is a problem that a separate process for imparting functionality to the graphene or the use of a dispersant is required to apply graphene.

Thus, the inventors of the present invention have completed the present invention by confirming a method capable of effectively producing graphene and simultaneously imparting functionality to the surface of graphene.

The present invention provides a method for producing a polymer-graphene hybrid using a method of electrochemically treating a graphene precursor.

In order to solve the above-described problems, the present invention provides a method of manufacturing a thin film transistor comprising a first electrode including a graphene precursor; A second electrode; And a step of applying a voltage to the first electrode and the second electrode in an electrolyte comprising 1-vinyl-2-pyrrolidinone, and ammonium ion or pyridinium ion, wherein the polyvinylpyrrolidone- A method for producing a pin hybrid is provided.

The term "graphite" used in the present invention refers to a material which is also called graphite or talc and belongs to a hexagonal system having a crystal structure such as quartz, and is a material having a black color and metallic luster. The graphite has a plate-like structure. A single layer of graphite is called "graphene" to be produced in the present invention, and thus graphite becomes the main raw material for the production of graphene.

In order to separate graphene from graphite, it is necessary to apply energy to overcome the pi-pi interaction between the stacked graphenes. In the present invention, an electrochemical treatment is used.

Specifically, the manufacturing method according to the present invention is a step of peeling a graphene precursor from a first electrode including a graphene precursor, and is also referred to as electrochemical exfoliation (ECE) because of the use of a voltage or the like. The peeling process of the graphene precursor according to the step 1 is schematically shown in FIG.

As shown in FIG. 1, in an apparatus including a first electrode, a second electrode, and an electrolyte existing between the electrodes, the first electrode includes a graphene precursor and serves as a cathode, It plays a role.

At this time, the electrolyte contains two kinds of substances, one of which is ammonium ion or pyridinium ion, and the other is 1-vinyl-2-pyrrolidinone. When a voltage is applied to the first electrode and the second electrode, ammonium ions or pyridinium ions contained in the electrolyte migrate between the layers of the graphene precursor, thereby increasing the spacing between the graphene layers. Also, the 1-vinyl-2-pyrrolidinone contained in the electrolyte is intercalated between the graphene layers. When a voltage is continuously applied to maintain the electric field, 1-vinyl-2-pyrrolidinone inserted between the graphene layers is electropolymerized to form polyvinylpyrrolidone. As the polyvinylpyrrolidone is formed, the interlayer spacing of the graphene is further widened and the peeling proceeds, and at the same time, the polyvinylpyrrolidone is grafted to the graphene surface.

As used herein, the term " polyvinylpyrrolidone-graphene hybrid " used in the present invention refers to a substance prepared by the production method according to the present invention, wherein polyvinylpyrrolidone is physically / chemically ≪ / RTI > Generally, since graphene has hydrophobicity, it tends to be agglomerated without being well dispersed in a hydrophilic solvent such as water. However, the polyvinylpyrrolidone-graphene hybrid prepared according to the present invention is a polyvinylpyrrolidone- Because money is formed, it can be dispersed well in hydrophilic solvent.

According to the above production method, graphene can be easily peeled from a graphene precursor, for example, graphite, and at the same time, functionality can be imparted to the graphene surface to improve dispersibility and the like, A vinyl pyrrolidone-graphene hybrid can be produced.

In the first electrode comprising the graphene precursor, the graphene precursor is preferably graphite. More preferably, the first electrode is made of graphite, and for example, a graphite foil can be used. In addition, the graphene precursor peeled off by the manufacturing method according to the present invention should be understood as a material in which the gap between the graphene layers in the graphene precursor used for the first electrode is widened or the graphene layers are separated from each other.

The second electrode is not particularly limited as long as it is a conductive material and preferably a Pt electrode, an Au electrode, a carbon rod, a graphite electrode, a steel electrode, an Hg electrode, an Ag electrode, a Cu electrode, W electrodes can be used.

The ammonium ion contained in the electrolyte may be represented by the following Formula 1:

[Chemical Formula 1]

R ₁ R ₂ R ₃ R ₄ N ⁺

In Formula 1,

R ₁ to R ₄ are each independently hydrogen or C _1-10 alkyl.

Preferably, R ₁ to R ₄ in the general formula (1) are C _1-10 alkyl. Specific examples of the ammonium ion include tetraethylammonium, tetra-n-tetrabutylammonium, and perchlorate may be used as a counter ion of the ammonium ion or the pyridinium ion.

It is preferable that the ammonium ion or the pyridinium ion is contained in the electrolyte at a concentration of 0.01 M to 0.5 M, more preferably 0.05 M to 0.25 M. The 1-vinyl-2-pyrrolidinone is preferably a monomer of polyvinylpyrrolidone and is contained in the electrolyte in a concentration of 0.001 M to 0.1 M, more preferably 0.005 M to 0.05 M.

As the solvent used in the electrolyte, water, DMF (N, N-dimethylformamide), DME (1,2-dimethoxyethane), DMSO, or propylene carbonate may be used.

In addition, the voltage applied to the first electrode and the second electrode is preferably 0.01 to 200 V, more preferably 1 to 10 V, and most preferably 3 to 4 V. The voltage application time is preferably 1 minute to 3 hours, more preferably 10 minutes to 1 hour.

In addition, the magnitude of the voltage and the voltage application time can be adjusted step by step, as needed, by dividing the voltage into several steps. For example, a voltage may be applied for a first time with a first voltage, and then a voltage may be applied with a second voltage for a second time. Accordingly, the degree of the movement of the ammonium ion or the pyridinium ion between the layers of the graphene precursor and the degree of polymerization of the 1-vinyl-2-pyrrolidone inserted between the layers can be controlled stepwise.

Further, in the polyvinylpyrrolidone-graphene hybrid prepared above, the content of polyvinylpyrrolidone is preferably 0.1% by weight to 20% by weight. The weight average molecular weight of the polyvinyl pyrrolidone is 8,000 to 50,000. The content and the weight average molecular weight of the polyvinyl pyrrolidone can be controlled according to the concentration of the ammonium ion or the pyridinium ion contained in the electrolyte, the concentration of the polyvinyl pyrrolidone, or the voltage and the voltage application time.

Meanwhile, the production method according to the present invention may further include a step of recovering the polyvinylpyrrolidone-graphene hybrid prepared. The method may further include washing and / or drying the recovered polyvinylpyrrolidone-graphene hybrid.

The polyvinylpyrrolidone-graphene hybrid prepared according to the present invention has not only a uniform graphene size but also a grafted polyvinylpyrrolidone on the surface of the graphene grains, so that the dispersibility in a hydrophilic solvent is excellent Feature. Accordingly, the composition can be re-dispersed in various solvents and used for various applications such as a composition for forming a heat dissipation substrate, a conductive paste composition, a conductive ink composition, an electrically conductive composite, an EMI package composite, a conductive material for a battery, or a slurry.

The method of producing graphene according to the present invention is characterized in that graphene precursor is treated by an electrochemical method and at the same time polyvinylpyrrolidone is formed on the surface of graphene, It has a feature that it can give functionality to graphene.

Fig. 1 schematically shows a manufacturing method of the present invention.
Fig. 2 shows TGA analysis results of the graphene prepared in Examples and Comparative Examples of the present invention.
Fig. 3 shows the dispersibility of graphene prepared in the example of the present invention.
FIG. 4 shows SEM images and TEM images of graphene prepared in Examples and Comparative Examples of the present invention.
Fig. 5 is a graph showing relative sedimentation rates of graphene prepared in Examples and Comparative Examples of the present invention.

Best Mode for Carrying Out the Invention Hereinafter, preferred embodiments are shown to facilitate understanding of the present invention. However, the following examples are intended to illustrate the present invention without limiting it thereto.

Example  1 to 4

As shown in FIG. 1, a graphite foil (2.5 cm x 3.5 cm) having a thickness of 0.1 mm to 1 mm was used as a cathode, and a Pt mesh electrode having the same area as an anode was charged with 250 ml Of DMF was used as the electrolyte. And a direct current was supplied thereto under the conditions shown in Table 1 below. The polyvinylpyrrolidone-graphene hybrid formed on the cathode was then recovered, washed with water and dried.

Electrolyte Direct current VP ¹⁾ TEAP ^{2 )} Voltage Voltage application time Example 1 0.005 M 0.05 M 3 ~ 4 V 10 minutes Example 2 0.05 M 0.05 M 3 ~ 4 V 60 minutes Example 3 0.05 M 0.25 M 3 ~ 4 V 10 minutes Example 4 0.05 M 0.25 M 3 ~ 4 V 60 minutes 1) VP: 1-vinyl-2-pyrrolidinone
2) TEAP (tetraethylammonium perchlorate)

Experimental Example  One

The polyvinylpyrrolidone-graphene hybrid prepared in the above Example was analyzed for the content of polyvinylpyrrolidone formed on the graphene surface.

Specifically, according to FIG. 2 (a) in which TGA (Thermogravimetric Analysis) of commercial polyvinylpyrrolidone PVP 8k (Mw: 8,000) and PVP 58k (Mw: 58,000) was analyzed, PVP58k exhibited a weight loss at about 400 ° C. , PVP8k having a low molecular weight has a weight loss at 350 deg. Based on the results, it was confirmed from the decrease of peaks occurring at about 250 to 400 ° C according to FIG. 2 (b) in which TGA was analyzed for the polyvinylpyrrolidone-graphene hybrid prepared in the above example, Can be analyzed. Thus, the polyvinylpyrrolidone-graphene hybrids prepared in Examples 1 to 4 had 5.1 wt%, 6.9 wt%, 11 wt%, and 12.1 wt% polyvinylpyrrolidone, respectively. . In addition, the weight average molecular weight of the polyvinylpyrrolidone formed on the graphene surface is expected to be about 10,000.

Experimental Example  2

The dispersibility of the polyvinylpyrrolidone-graphene hybrid prepared in the above Example was analyzed. Specifically, 0.05 g of the polyvinylpyrrolidone-graphene hybrid of Example 4 was placed in 10 mL of the solvent as shown in FIG. 3, followed by bath sonication for 30 minutes, and the degree of dispersion was observed and shown in FIG.

As shown in FIG. 3, it showed excellent dispersibility in all solvents except water, acetone, DCM and ethanol.

Experimental Example  3

The surface of the polyvinylpyrrolidone-graphene hybrid prepared in the above example was observed by SEM and TEM images. Specifically, the surface of the polyvinylpyrrolidone-graphene hybrid prepared in Example 4 was observed by SEM and TEM images and shown in Figs. 4 (a) and 4 (c), respectively. As a comparative example, 2.5 g of graphite (BNB90) and 0.5 g of PVP8k were placed in 500 g of DMF, followed by bath sonication for 30 minutes, and then the surface of the prepared graphene was observed with SEM and TEM images, And Fig. 4 (d).

The comparative example uses 20 wt% of PVP 8k as graphite, and the example according to the present invention has a PVP adsorption amount of about 12 wt%. However, as shown in Fig. 4, it can be confirmed that the embodiment according to the present invention in which the PVP content is smaller exhibits better peeling and dispersibility.

Experimental Example  4

The dispersion stability of the polyvinylpyrrolidone-graphene hybrid prepared in the above Example was evaluated. Specifically, 2.5 g of the polyvinylpyrrolidone-graphene hybrid prepared in Example 4 was added to 500 g of DMF and subjected to bath sonication for 30 minutes. 4 mL of the solution was transferred to a transparent cell (2 mm in thickness, 8 mm in width) And then set at 1,000 rpm, and the rate at which the point at which the transmittance of 865 nm light was changed by 30% with time was measured. As a comparative example, 2.5 g of graphite (BNB90), 0.5 g of PVP8k or PVP58k was added to 500 g of DMF, and the solution was subjected to bath sonication for 30 minutes. Then, 4 mL of the solution was measured in the same manner as above, As shown in Fig.

The comparative example uses 20 wt% of PVP8k or PVP58k relative to graphite, and the embodiment according to the present invention has a PVP adsorption amount of about 12 wt%. However, as shown in Fig. 5, it can be confirmed that the embodiment according to the present invention having a smaller PVP content shows better dispersion stability. This is because dispersion stability is improved by polyvinylpyrrolidone formed on the surface of graphene.

Claims (13)

A first electrode comprising a graphene precursor; A second electrode; And a step of applying a voltage to the first electrode and the second electrode in an electrolyte comprising 1-vinyl-2-pyrrolidinone, and ammonium ion or pyridinium ion, wherein the polyvinylpyrrolidone- / RTI >
The method according to claim 1,
Wherein the first electrode comprising the graphene precursor is graphite.
Gt;
The method according to claim 1,
Wherein the second electrode is a Pt electrode, an Au electrode, a carbon rod, a graphite electrode, a steel electrode, an Hg electrode, an Ag electrode, a Cu electrode, a Ti electrode,
Gt;
The method according to claim 1,
Wherein the ammonium ion is represented by the following general formula (1)
Manufacturing method:
[Chemical Formula 1]
R ₁ R ₂ R ₃ R ₄ N ⁺
In Formula 1,
R ₁ to R ₄ are each independently hydrogen or C _1-10 alkyl.
5. The method of claim 4,
Wherein R ₁ to R ₄ are C _1-10 alkyl.
Gt;
5. The method of claim 4,
Wherein the ammonium ion is tetraethylammonium or tetra-n-tetrabutylammonium.
Gt;
The method according to claim 1,
Wherein the concentration of the ammonium ion or the pyridinium ion in the electrolyte is 0.01 M to 0.5 M,
Gt;
The method according to claim 1,
Wherein the concentration of 1-vinyl-2-pyrrolidone in the electrolyte is 0.001 M to 0.1 M,
Gt;
The method according to claim 1,
Wherein the solvent of the electrolyte is water, N, N-dimethylformamide, 1,2-dimethoxyethane, DMSO, or propylene carbonate.
Gt;
The method according to claim 1,
Wherein the voltage applied to the first electrode and the second electrode is in the range of 0.01 V to 200 V,
Gt;
The method according to claim 1,
Wherein the voltage application time is from 1 minute to 3 hours.
Gt;
The method according to claim 1,
Wherein the content of polyvinylpyrrolidone in the polyvinylpyrrolidone-graphene hybrid is 0.1 wt% to 20 wt%
Gt;
The method according to claim 1,
Wherein the weight average molecular weight of the polyvinyl pyrrolidone is 8,000 to 50,000.
Gt;

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