Polymer-graphene composite, method for preparing same, and polymer-graphene composite composition using same

Abstract

The present invention relates to a polymer-graphene composite, in which a polymer has been introduced onto the surface of graphene while maintaining the structural features and mechanical properties of the graphene, thereby realizing an excellent dispersibility in an organic solvent, a method for preparing the same, and a polymer-graphene composite composition using the same.

Claims

1. A polymer-graphene composite comprising: graphene having a planar structure; and a polymer which is bound to the graphene through a functional group including a carbonyl group and an alkylene group having 1 to 20 carbon atoms, wherein in the polymer-graphene composite, the carbonyl group and the graphene are directly bound to each other, and wherein the graphene contains one or more oxidative functional groups selected from the group consisting of a hydroxyl group, a carbonyl group and a carboxyl group in an amount of less than 1% by weight based on a total weight of graphene, wherein in the functional group, the carbonyl group and the alkylene group having 1 to 20 carbon atoms are directly bound to each other, wherein a ratio of a diameter to a thickness of the graphene is 50 to 6,000.

2. The polymer-graphene composite according to claim 1, wherein in the polymer-graphene composite, the alkylene group having 1 to 20 carbon atoms and the polymer are directly bound to each other.

3. The polymer-graphene composite according to claim 1, wherein the functional group is a functional group represented by the following Chemical Formula 1: ##STR00007## wherein in Chemical Formula 1, A represents an alkylene group having 1 to 20 carbon atoms, X represents a point bound with the graphene, and Y represents a point bound with the polymer.

4. The polymer-graphene composite according to claim 1, where in a content of the polymer included in the polymer-graphene composite is 0.1% by weight to 30% b y weight.

5. The polymer-graphene composite according to claim 1, wherein the polymer includes one or more polymers selected from the group consisting of a polyglycol-based polymer, a polyvinyl-based polymer, a polyolefin-based polymer, a polyester-based polymer, a polyamide-based polymer, a polyimide-based polymer, a polyether-based polymer, a polysilicon-based polymer, polyfluorine-based polymer, a nylon-based polymer, and a polyurethane-based polymer.

6. The polymer-graphene composite according to claim 5, wherein the polyvinyl-based polymer includes one or more polymers selected from the group consisting of polystyrene, polyacrylate, polymethacrylate, and polyacrylonitrile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates the measurement results of IR spectrum for the graphene obtained in the Preparative Examples.

(2) FIG. 2 illustrates the measurement results of IR spectrum for the functionalized graphene obtained in the Examples.

(3) FIG. 3 illustrates the measurement results of IR spectrum for the polymer-graphene composite obtained in the Examples.

(4) FIG. 4 illustrates the measurement results by thermogravimetric analysis for the graphene 1 obtained in the Preparative Examples, the functionalized graphene 2 obtained in the Examples, the polymer-graphene composite 3 obtained in the Examples, and the polymer-graphene composite 4 obtained in Comparative Example 2.

(5) FIG. 5 illustrates the measurement results of dispersibility for the polymer-graphene composite dispersion obtained in the Examples.

(6) FIG. 6 illustrates the measurement results of dispersibility for the graphene dispersion obtained in the Comparative Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) The present invention will be described in more detail with reference to the Examples below. However, these Examples are provided for illustrative purposes only, and should not be construed as limiting the scope of the present invention to these Examples.

Preparative Examples: Preparation of Graphene

(8) (1) Preparation of Dispersant

(9) The following oxidation and purification processes were performed on pitch, which is a petroleum byproduct obtained from POSCO, to prepare a dispersant.

(10) First, 0.5 to 1.5 g of the pitch was added to 75 ml of a mixed solution of sulfuric acid/nitric acid (volume ratio of 3:1), and oxidation reaction was performed at 70° C. for about 3.5 hours.

(11) Subsequently, the pitch reaction solution, which had undergone the oxidation reaction, was cooled to room temperature, then diluted approximately 5-fold with distilled water, and then centrifuged at about 3500 rpm for 30 minutes. Then, the supernatant was removed, an equal amount of distilled water was added for re-dispersion, followed by centrifugation again under the same conditions to finally recover and dry the precipitate. In this way, a dispersant was prepared.

(12) (2) Preparation of Graphene Flake

(13) 2.5 g of planar graphite was added to 500 ml of an aqueous dispersion, in which 0.1 g of the dispersant was dispersed, to form a dispersion. This dispersion was introduced into the inlet of a high-pressure homogenizer at a high pressure of about 1,600 bar to pass through the micro channel. This process was repeated ten times. In this way, the planar graphite was exfoliated, and thus a graphene flake was prepared.

Examples: Preparation of Functionalized Graphene, Graphene-Polymer Composite and Graphene-Polymer Composite Dispersion

(14) 1. Preparation of Functionalized Graphene

(15) ##STR00005##

(16) In an ice bath, 6.65 g of an AlCl.sub.3 catalyst was added to 100 ml of 1,2-dichlorobenzene, and 7 g of the graphene flake prepared in the Preparative Examples and 11.5 g of α-bromoisobutyryl bromide (BIBB) were added and mixed, and then the mixture was subjected to a Friedel-Craft acylation reaction at a temperature of 90° C. for 20 hours to prepare a functionalized graphene.

(17) 2. Preparation of Polymer-Graphene Composite

(18) ##STR00006##

(19) 50 mg of copper bromide (CuBr) and 87 mg of N,N,N′,N,N-pentamethyldiethylenetriamine (PMDETA) were added to 100 ml of styrene, and the mixture was stirred at room temperature for 20 minutes while injecting nitrogen. Then, 3 g of the functionalized graphene was added, followed by an atom transfer radical polymerization (ATRP) reaction at a temperature of 100° C. for 40 hours to prepare a polymer-graphene composite.

(20) 3. Preparation of Polymer-Graphene Composite Dispersion

(21) The polymer-graphene composite obtained in the Examples was added at a concentration of 0.5 mg/ml to the respective solvents of dimethylformamide (DMF), dichloromethane (DCM), tetrahydrofuran (THF), toluene, and methyl ethyl ketone (MEK), and sonicated for 30 minutes to prepare polymer-graphene composite dispersions.

Comparative Examples: Preparation of Graphene Dispersion

Comparative Example 1

(22) The graphene flake obtained in the Preparative Examples was added at a concentration of 0.5 mg/ml to the respective solvents of dimethylformamide (DMF), dichloromethane (DCM), tetrahydrofuran (THF), toluene, and methyl ethyl ketone (MEK), and sonicated for 30 minutes to prepare graphene dispersions.

Comparative Example 2

(23) A polymer-graphene oxide composite was prepared in the same manner as in the Examples, except that graphene oxide (GO) powder prepared by a conventional oxidation process (for example, Hummer's method or a modified Hummer's method) of graphite was used instead of the graphene flake prepared in the Preparative Example.

Experimental Examples: Measurement of Properties for Preparative Examples, Examples and Comparative Examples

(24) The properties for the graphene obtained in the Preparative Examples, and the functionalized graphene, graphene-polymer composite and graphene-polymer composite dispersion obtained in the Examples were measured by the following methods. In the same manner, the properties for the graphene-polymer composite or graphene dispersion obtained in the Comparative Examples were measured and compared.

Experimental Example 1. IR Spectrum

(25) IR spectrum was measured for each of the graphene obtained in the Preparative Examples, and the functionalized graphene and graphene-polymer composite obtained in the Examples, and the results were illustrated in FIGS. 1 to 3, respectively, as set forth in Table 1 below.

(26) TABLE-US-00001 TABLE 1 Results of Experimental Example 1 Functionalized Polymer-graphene Category Graphene graphene composite IR Spectrum FIG. 1 FIG. 2 FIG. 3

(27) As illustrated in FIGS. 1 and 2, it can be seen that there was no significant difference in terms of IR spectrum between the graphene and the functionalized graphene. However, in the case of the polymer-graphene composite illustrated in FIG. 3, it can be seen that a significant difference was observed in terms of IR spectrum as a polymer was introduced. In particular, in view of the fact that the IR peak corresponding to the main characteristics of a polystyrene polymer was measured, it can be seen that a polymer was actually introduced into the polymer-graphene composite.

Experimental Example 2. Thermogravimetric Analysis (TGA)

(28) For the graphene 1 obtained in the Preparative Examples, the functionalized graphene 2 and graphene-polymer composite 3 obtained in the Examples, and the graphene-polymer composite 4 obtained in Comparative Example 2, a thermogravimetric analyzer was used to measure the change in weight while heating from room temperature to a temperature of 600° C. under a nitrogen atmosphere, and the results were illustrated below in Table 2 and FIG. 4.

(29) TABLE-US-00002 TABLE 2 Results of Experimental Example 2 Polymer- Polymer- graphene oxide graphene composite of Functionalized composite of Comparative Category Graphene graphene the Examples Example 2 Weight 0.2 wt % 1.4 wt % 10.2 wt % 48 wt % (at loss 220° C. or less: 30 wt %/ at 220° C. to 430° C.: 18 wt %)

(30) As illustrated in the above Table 2 and FIG. 4, it can be seen that the pure graphene of the Preparative Examples had almost no change in weight, which is approximately 0.2 wt % even when heated at a high temperature. In addition, it can be seen that the weight loss was increased to 1.4 wt % when a BIBB-derived functional group as a functionalizing group was introduced into the graphene, and to 10.2 wt % when a polymer was introduced into the graphene.

(31) In particular, in the case of the polymer-graphene composite of the Examples, it can be seen that since the polymer introduced into the graphene is burned as the temperature is increased, the amount of weight loss is increased. In this way, it can be seen that about 10 wt % of the polymer was introduced with respect to the entire polymer-graphene composite.

(32) On the other hand, in the case of the polymer-graphene oxide composite of Comparative Example 2, it can be seen that that the pyrolysis curve was completely different from those of the Preparative Examples and the Examples. Specifically, referring to the thermogravimetric analysis results of the polymer-graphene oxide composite of Comparative Example 2 as illustrated below in FIG. 4, at the temperature range of 220° C. or lower, a remarkable weight loss of about 30 wt % occurred as hydroxyl group (—OH) of the graphene oxide was decomposed due to dehydration, and at the temperature range of 220° C. to 430° C., a weight loss of about 18 wt % occurred as the polymer introduced into the graphene oxide was decomposed.

(33) That is, it can be seen that the polymer-graphene oxide composite of Comparative Example 2 contains a total of about 48 wt % of a non-conductive composition including a hydroxyl group and a polymer, and the polymer-graphene prepared in the Examples contains about 10 wt % of a non-conductive composition. As a result, it can be seen that Comparative Example 2 had a low electric conductivity compared to the Examples.

Experimental Example 3. Dispersibility

(34) Each of the graphene-polymer composite dispersion obtained in the Examples and the graphene dispersion obtained in Comparative Example 1 was allowed to stand under the conditions of room temperature and atmospheric pressure for 48 hours, and the dispersibility was evaluated. The results were illustrated in FIGS. 5 and 6 as set forth in Table 3 below.

(35) TABLE-US-00003 TABLE 3 Results of Experimental Example 3 Category Examples Comparative Example 1 Dispersibility FIG. 5 FIG. 6

(36) As illustrated in FIG. 5, it can be seen that the polymer-graphene composite dispersion prepared in the Examples was uniformly dispersed in all solvents, indicating an excellent dispersibility.

(37) On the other hand, in the case of the dispersion prepared in Comparative Example 1, it can be seen that when the functionalized graphene was dispersed in a solvent, the functionalized graphene was not uniformly dispersed in the solvent and precipitated at the bottom, as illustrated in FIG. 6.

(38) From these results, it can be seen through experiments that in the case of using the composite, in which a polymer is bound to graphene, as in the Examples, it is possible to exhibit an excellent dispersibility in an organic solvent.

Experimental Example 4. Electrical Conductivity

(39) Each of the graphene-polymer composite obtained in the Examples and the graphene-polymer composite obtained in Comparative Example 2 was dispersed in a THF solvent, then filtered through a nylon filter, and dried to prepare a specimen of graphene-polymer composite sheet. The electrical conductivities of the specimens were measured under the conditions of room temperature and atmospheric pressure using a 4-probe method, and the results were illustrated in Table 4 below.

(40) TABLE-US-00004 TABLE 4 Results of Experimental Example 4 Category Examples Comparative Example 2 Electrical conductivity (S/cm) 120 0.42

(41) As illustrated in the above Table 4, it can be seen that in the case of the Examples using the pure graphene flake in a unoxidized state of the Preparative Examples, the electrical conductivity of the polymer-graphene composite was measured as high as 120 S/cm, whereas in the case of Comparative Example 2 using graphene oxide powder, the electrical conductivity of the polymer-graphene composite was significantly reduced to 0.42 S/cm. Accordingly, it can be seen that in the case of the composite of the Examples using the unoxidized graphene of the Preparative Examples, the composite has an electric conductivity as high as about 300 times that of the composite of Comparative Example 2 which is made of an oxidized graphene.