Method for preparing functionalized graphene

Abstract

The present invention relates to a method for preparing a functionalized graphene. The method for preparing a functionalized graphene according to the present invention can functionalize graphene by a simple method and does not use any other substance other than graphene and a salt containing a double bond, thereby enabling functionalization of graphene while exhibiting characteristics inherent to graphene.

Claims

1. A method for preparing a functionalized graphene, comprising: 1) mixing graphene with a salt containing a double bond to prepare a mixture; 2) heat-treating the mixture at 150 to 300° C., and 3) forming the functionalized graphene.

2. The method of claim 1, wherein the salt containing a double bond is a compound represented by the following Chemical Formula 1 or 2: ##STR00002## in Chemical Formula 1, R.sup.1 is a single bond; a substituted or unsubstituted alkylene having 1 to 60 carbon atoms; or a substituted or unsubstituted arylene having 6 to 60 carbon atoms, X.sup.1 is CO, or SO.sub.2, and M.sup.1 is an alkali metal,
M.sup.2O—X.sup.2—R.sup.2—X.sup.2—OM.sup.2  [Chemical Formula 2] in Chemical Formula 2, R.sup.2 is a substituted or unsubstituted alkenylene having 1 to 60 carbon atoms, X.sup.2 is CO, or SO.sub.2, and M.sup.2 is an alkali metal.

3. The method of claim 2, wherein R.sup.1 is a single bond; or phenylene.

4. The method of claim 2, wherein R.sup.2 is ethenylene (—CH═CH—).

5. The method of claim 2, wherein the salt containing a double bond is 4-styrenesulfonic acid sodium salt, sodium acrylate, maleic acid sodium salt, or vinylsulfonic acid sodium salt.

6. The method of claim 2, wherein the salt containing a double bond is mixed in an amount of 0.2 to 5.0 parts by weight based on 1 part by weight of graphene.

7. The method of claim 2, wherein the heat treating is performed for 10 minutes to 24 hours.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 schematically shows the principle of the present invention.

(2) FIG. 2 shows TGA and DSC data of 4-styrenesulfonic acid sodium salt used in one embodiment of the present invention.

(3) FIG. 3 shows the dispersibility of a functionalized graphene according to one embodiment of the present invention.

(4) FIG. 4 shows the dispersion stability of a functionalized graphene according to one embodiment of the present invention.

(5) FIG. 5 shows NMR data of a functionalized graphene according to an embodiment of the present invention. FIG. 5(a) shows the case where the heat treatment time is 10 minutes, and FIG. 5(b) shows the case where the heat treatment time is 2 hours.

(6) FIG. 6 shows TOF-SIMS analysis result of a functionalized graphene according to one embodiment of the present invention.

(7) FIG. 7 shows TGA and DSC data of sodium acrylate used in one embodiment of the present invention.

(8) FIG. 8 shows the dispersibility of a functionalized graphene according to one embodiment of the present invention.

(9) FIG. 9 shows the dispersibility of a functionalized graphene according to one embodiment of the present invention.

(10) FIG. 10 shows the dispersibility of a functionalized graphene in various solvents according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(11) Hereinafter, preferred examples are provided for better understanding of the invention. However, these Examples are given for illustrative purposes only and are not intended to limit the scope of the present invention thereto.

Example 1: Functionalization of Graphene Using 4-styrenesulfonic Acid Sodium Salt

(12) 1) TGA and DSC Analysis of 4-styrenesulfonic Acid Sodium Salt

(13) In order to determine the heat treatment temperature of 4-styrenesulfonic acid sodium salt (hereinafter referred to as ‘SS’), TGA and DSC data were measured when SS was heated from room temperature to 900° C. under a nitrogen atmosphere, and the results are shown in FIG. 2.

(14) As shown in FIG. 2, it was confirmed that an exothermic reaction occurred at about 300° C. Therefore, the heat treatment temperature with graphene was set to 300° C. in the following.

(15) 2) Method of Preparing Functionalized Graphene

(16) 0.5 g of graphene and 1.0 g of SS were mixed with 20 mL of water. The mixture was dried to remove water, and then heat-treated in a tube furnace at 300° C. for 10 minutes. The product was washed with water and then filtered to prepare a functionalized graphene.

(17) 3) Evaluation of Dispersion Stability

(18) For comparison, 1) a composition obtained by mixing 0.5 g of graphene and 1.0 g of SS, 2) a composition obtained by mixing 1.0 g of SS heat-treated at 300° C. for 10 minutes with 0.5 g of graphene, 3) a composition obtained by mixing 0.5 g of graphene and 1.0 g of PSS (polystyrenesulfonate; Mw: 75,000) were prepared.

(19) The functionalized graphene previously prepared and the compositions were added to water at a concentration of 2 mg/ml and redispersed, and the results are shown in FIG. 3.

(20) As shown in FIG. 3, the functionalized graphene prepared in Example 1 was excellent in water dispersibility, and the remainder all precipitated.

(21) 4) Evaluation of Dispersion Stability

(22) The functionalized graphenes previously prepared were added to water at 2 mg/ml, 4 mg/ml, 6 mg/ml, and 8 mg/ml, respectively, and whether or not to precipitate over time was confirmed. The results are shown in FIG. 4.

(23) As shown in FIG. 4, when observed with the naked eye, the dispersibility by concentration was similar and some precipitates were confirmed from 3 days later, but the dispersibility was remarkably maintained even after the lapse of 2 weeks.

(24) 5) Evaluation of Radical Activity of Double Bond According to Heat-Treatment Time

(25) Functionalized graphene was prepared in the same manner as in the above-mentioned ‘2) Method of preparing functionalized graphene’, except that the heat treatment was performed in a tube furnace at 300° C. for 2 hours.

(26) NMR (DMSO-d.sub.6, Bruker 700 MHz NMR) of the respective functionalized graphenes prepared was measured, and the results are shown in FIG. 5.

(27) As shown in FIG. 5, it was confirmed that as the heat treatment time was increased, the rate of conversion from monomer to polymer (or oligomer) was increased. This is due to an increase in the radical activity of the double bond present in SS when the heat treatment time is increased.

(28) 6) Evaluation of Degree of Binding Between Graphene and SS

(29) The degree of binding of SS to graphene in the functionalized graphene prepared above was evaluated. Specifically, a total of six samples of #1 (graphene alone), #2 (functionalized graphene prepared in the above-mentioned ‘2) Method of preparing functionalized graphene’), #3 (SS alone), #4 (heat treatment of SS alone at the same temperature and time as #2), #5 (a mixture of GNP and SS (no heat treatment)), and #6 (graphene prepared by omitting washing with water, in functionalized graphene prepared in ‘2) Method of preparing functionalized graphene’) were analyzed by TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry). The results are shown in FIG. 6.

(30) In TOF-SIMS, when the sample surface is beaten by a primary ion, a portion forming a relatively weak bond is detected at the detector. As shown in FIG. 6, C.sub.8H.sub.7SO.sub.3 present in #3 is detected in most of the samples, but in the case of #2, it can be confirmed that the amount detected is insignificant. Therefore, it can be confirmed that the functionalized graphene according to the present invention has a strong bond between graphene and SS.

Example 2: Functionalization of Graphene Using Sodium Acrylate

(31) 1) TGA and DSC Analysis of Sodium Acrylate

(32) In order to determine the heat treatment temperature of sodium acrylate (hereinafter referred to as ‘SA’), TGA and DSC data were measured when SA was heated from room temperature to 900° C. under a nitrogen atmosphere, and the results are shown in FIG. 7.

(33) As shown in FIG. 7, it was confirmed that an exothermic reaction occurred at about 300° C. Therefore, the heat treatment temperature with graphene was set to 300° C. in the following.

(34) 2) Preparation of Functionalized Graphene

(35) 0.25 g of graphene and 1.0 g of SA were mixed with 20 mL of water. The mixture was dried to remove water, and then heat-treated in a tube furnace at 150° C., 200° C., 250° C. and 300° C. for 10 minutes, respectively. The respective products were washed with water and then filtered to prepare a functionalized graphene.

(36) In addition, 0.5 g of graphene and 1.0 g of SA were mixed with 20 mL of water. The mixture was dried to remove water, and then heat-treated in a tube furnace at 150° C. (10 min), 200° C. (10 min), 250° C. (10 min), 300° C. (10 min) and 300° C. (2 hr). The respective products were washed with water and then filtered to prepare a functionalized graphene.

(37) 3) Evaluation of Dispersion Stability

(38) The functionalized graphenes prepared above were added respectively to water, ethanol and methanol at a concentration of 1.5 mg/ml and dispersed, and whether or not to precipitate over time was confirmed. The results are shown in FIG. 8.

(39) As shown in FIG. 8, precipitates hardly occurred even after the lapse of 2 weeks.

Example 3: Functionalization of Graphene Using Maleic Acid Sodium Salt

(40) 1) Preparation of Functionalized Graphene

(41) 0.5 g of graphene and 1.0 g of maleic acid sodium salt (hereinafter referred to as ‘MA’) were mixed with 20 mL of water. The mixture was dried to remove water, and then heat-treated in a tube furnace at 300° C. for 10 minutes. The product was washed with water and then filtered to prepare a functionalized graphene (A).

(42) In addition, 0.5 g of graphene and 1.0 g of MA were mixed with 20 mL of water. The mixture was dried to remove water, and then heat-treated in a tube furnace at 300° C. for 20 hours. The product was washed with water and then filtered to prepare a functionalized graphene (B).

(43) 2) Evaluation of Dispersion Stability

(44) The functionalized graphenes prepared above were added respectively to water at a concentration of 1.5 mg/ml and dispersed, and whether or not to precipitate over time was confirmed. The results are shown in FIG. 9.

(45) As shown in FIG. 9, in the case of (A), some precipitates occurred after 1 hour, but in the case of (B) with the longer heat treatment time, the dispersion stability was excellent, which means that the degree of reaction with graphene increases with the heat treatment time.

(46) In addition, the functionalized graphenes (B) prepared above were added respectively to ethanol, acetone, THF, NMP and toluene at a concentration of 1.5 mg/mL and dispersed, and whether or not to precipitate over time was confirmed. The results are shown in FIG. 10.

(47) As shown in FIG. 10, the dispersibility in most of the solvents was excellent, and particularly, the dispersibility in ethanol and NMP was excellent.