Edge-grafted graphene, aqueous dispersion thereof, and method for preparing same

Abstract

The present invention relates to edge-grafted graphene, its aqueous dispersion, and a method for preparing the same. The edge-grafted graphene comprises graphene and a water-soluble polymer grafted to the graphene edge. Based on the total mass of the edge-grafted graphene, the mass content of the water-soluble polymer grafted to the edge-grafted graphene is 1-30%. Compared to milling techniques such as ultrasonic milling, ball milling, and sand milling, milling disks have a weaker effect on the crystalline structure of graphite, making it easier to prepare large layered graphene. Furthermore, the water-soluble high-molecular-weight polymer can increase the viscosity of the solution, thereby indirectly transmitting the shear force between the milling disks to the graphite flakes, further reducing damage to the graphite crystalline lattice and improving the exfoliation effect of the graphite flakes. Furthermore, the water-soluble high-molecular-weight polymer can be grafted to graphene, providing a stabilizing effect, thereby forming a stable aqueous dispersion of edge-grafted graphene.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to the technical field of graphene preparation, and in particular to edge-grafted modified graphene, aqueous dispersions of edge-grafted modified graphene, and methods for preparing the same.

[0002] [Background technology] Graphene is a monolayer of carbon atoms with a honeycomb structure formed by bonding one carbon atom to three surrounding carbon atoms. Graphene has attracted attention as a new material with high optical transparency, high electrical conductivity, high thermal conductivity, a large specific surface area, and excellent mechanical properties. Currently, graphene is in the exploratory stage for large-scale preparation and application. The development of high-quality, low-cost preparation techniques for functionalized graphene will be fundamental for future large-scale applications. Engineers have developed a series of preparation techniques, including mechanical exfoliation, redox, chemical vapor deposition, epitaxial growth, thermal expansion, and electrochemical methods. Among these, the mechanical exfoliation and redox methods are based on graphite raw materials prepared by mechanical or chemical exfoliation techniques. These methods are characterized by abundant raw material sources and easy cost control. These methods are more suitable for large-scale graphene production. The redox method involves oxidizing natural graphite with a strong oxidizing agent, introducing abundant polar groups onto the surface, and then obtaining graphene oxide by solvation or ultrasonic dispersion. This process, however, involves the use of large amounts of strong acids and oxidizing agents, such as concentrated sulfuric acid, fuming nitric acid, potassium permanganate, and perchloric acid, resulting in significant wastewater pollution. The resulting graphene contains certain defects, such as topological defects (e.g., five-membered and seven-membered rings) or structural defects (e.g., hydroxyl groups) left behind by the polar groups removed by reduction. These defects cause partial loss of graphene's electrical properties, limiting its application. The national standard GB / T 30544.13-2018, "Nanotechnology Glossary Part 13: Graphene and Related Two-Dimensional Materials," provides separate definitions for graphene oxide and reduced graphene oxide to distinguish them from each other.

[0003] Graphene obtained by oxidation contains abundant oxygen-containing groups, such as epoxy, hydroxyl, and carboxyl groups, on its surface, which can be covalently modified by chemical reactions. Salavagine HJ et al. (Salavagione HJ, G Martinez, MA Gomez. Synthesis of poly(vinyl alcohol) / reduced graphite oxide nanocomposites with improved thermal and electrical properties[J]. Journal of Materials Chemistry, 2009, 19(28):5027-5032) studied the grafting of PVA to graphene oxide via esterification between the hydroxyl groups on PVA and the carboxyl groups on graphene oxide, yielding PVA-grafted graphene oxide. Wang Bo et al. (Wang Bo, He Shengfu, Zhang Fan et al., Preparation of Graphene Oxide Modified by Dendritic Polyamide-Amine Grafted and Its Adsorption Thermodynamics and Kinetics for Cu(II) [J], Fine Chemicals, 2014, 31(8):8) studied polyamide-amine grafted graphene oxide. Xu Guoqiang et al. (Xu Guoqiang, Xu Pengwu, Shi Dongjian et al., Preparation and Cellular Imaging of PEG grafted Graphene Oxide [J], Chinese Journal of Inorganic Chemistry, 2014, 30(009):1994-1999) studied PEG grafted graphene oxide.Li Shanrong et al. (Li Shanrong, Lu Shaorong, Qi Bo et al., Synthesis and Application of Biphenyl Liquid Crystal with Epoxy Groups Grafted Graphene Oxide [J], Polymer Material Science and Engineering, 2013, 29(007):17-20) studied biphenyl thermotropic liquid crystal grafted graphene oxide. They all prepared grafted graphene oxide by utilizing the abundant active groups on the surface of graphene oxide prepared by oxidation. However, these graphene oxide-based grafting techniques still have topological defects such as five-membered rings and seven-membered rings, as well as residual oxygen-containing groups on the graphene surface. These techniques involve PVA-grafted graphene oxide or PVA-grafted reduced graphene oxide.

[0004] Commonly used mechanical exfoliation methods include ball milling, sand milling, and ultrasonic exfoliation. While these methods can be used to produce large-scale graphene, the destructive effect of the mechanical forces is significant, causing severe damage to the graphene, resulting in graphene typically smaller than 100 nm. Therefore, one of the key technical aspects of mechanical exfoliation is to reduce the destructive force and prepare larger-sized graphene. Furthermore, due to the relatively strong mechanical forces, ball milling, sand milling, and ultrasonic exfoliation methods can result in a greater degree of surface grafting of graphene. Excessive surface grafting would adversely affect the excellent electrical conductivity, thermal conductivity, and other properties of graphene itself. Therefore, another key technical aspect of mechanical exfoliation is to reduce surface grafting and prepare edge-grafted graphene.

[0005] Stable aqueous dispersions of graphene are widely used in chemical, electronic, energy, medical, and other fields. There remains a need in the art for an efficient and low-cost method for forming aqueous dispersions of graphene that are stable for extended periods, e.g., one year or more.

[0006] Therefore, it is an object of the present invention to provide edge-grafted graphene having large size, capable of forming stable aqueous dispersions for long periods of time, and having desirable electrical and thermal conductivity. Another object of the present invention is to provide an efficient and low-cost method for preparing such edge-grafted graphene and stable aqueous dispersions.

[0007] [Contents of the invention] The present invention provides edge-grafted modified graphene, stable aqueous dispersions of edge-grafted modified graphene, and methods for preparing the same.

[0008] A first aspect of the present invention provides an edge-grafted modified graphene comprising graphene and a water-soluble polymer grafted to an edge of the graphene, wherein the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1 to 30%, preferably 2 to 25%, based on the total mass of the edge-grafted modified graphene.

[0009] A second aspect of the present invention provides an aqueous dispersion of edge-grafted graphene comprising water and stably dispersed therein edge-grafted graphene, wherein the edge-grafted graphene is the edge-grafted graphene described above.

[0010] A third aspect of the present invention provides a method for preparing an aqueous dispersion of the edge-grafted modified graphene described above, comprising the steps of: The method comprises the steps of uniformly mixing a water-soluble polymer, water, and graphite, completely dissolving the water-soluble polymer and then milling the mixture in a milling disc kettle, allowing the mixture to stand after milling, and removing the precipitate to obtain an aqueous dispersion of the edge-grafted modified graphene.

[0011] A fourth aspect of the present invention provides a method for preparing edge-grafted modified graphene, comprising the steps of: (1) preparing an aqueous dispersion of edge-grafted graphene according to the method described above; (2) A step of filtering the aqueous dispersion of edge-grafted graphene obtained in (1) and drying it to obtain edge-grafted graphene.

[0012] A fifth aspect of the present invention provides applications of edge-grafted modified graphene or aqueous dispersions of edge-grafted modified graphene in the fields of antistatic or conductive composite polymer materials, thermally conductive composite polymer materials, multilayer composite barrier films, barrier layer materials, adsorption materials, functional coatings, antistatic or conductive fiber materials, and solar or microwave absorbing materials.

[0013] The edge-grafted modified graphene and its aqueous dispersion have the following advantages: 1. Compared with ultrasonic, ball milling, sand milling and other milling processes, the milling disk has a weaker disruptive effect on the graphite crystal structure, making it easier to prepare larger graphene flakes.

[0014] 2. The water-soluble polymer can increase the viscosity of the solution and indirectly transfer the shear force between the milling discs to the graphite flakes, thereby further reducing the damage to the graphite crystal lattice, better maintaining the performance of graphene, and improving the exfoliation effect of graphite flakes.

[0015] 3. Water-soluble polymers can be grafted onto the edges of graphene, which has a stabilizing effect, leading to the formation of stable aqueous dispersions of edge-grafted modified graphene.

[0016] 4. The stable edge-grafted modified graphene is easy to separate from the precipitated graphite flakes, so the preparation process of the modified graphene of the present invention is very simple and convenient.

[0017] Additional features and advantages of the present invention are described in detail in the specific embodiments set forth below.

[0018] [Drawing Description] Exemplary embodiments of the present invention will now be described in more detail in conjunction with the drawings.

[0019] FIG. 1 shows a schematic diagram of an apparatus for preparing an aqueous dispersion of grafted graphene according to an embodiment of the present invention; Figure 2 shows photographs of the stable aqueous dispersions of polyvinyl alcohol-grafted graphene prepared in Examples 1 to 5; Figure 3 shows the scanning electron microscope image of the polyvinyl alcohol-grafted graphene prepared in Example 1, as well as the two-dimensional energy spectrum of carbon and oxygen elements; FIG. 4 shows the infrared absorption spectra of the polyvinyl alcohol-grafted graphene prepared in Example 1, as well as pure flake graphite and pure PVA, where the upper curve represents flake graphite, the middle curve represents PVA, and the lower curve represents PVA-grafted graphene; FIG. 5 shows the thermogravimetric analysis diagrams of the polyvinyl alcohol-grafted graphene prepared in Example 1, as well as pure flake graphite and pure PVA, in which the upper curve represents the flake graphite, the middle curve represents the PVA-grafted graphene, and the lower curve represents PVA; Figure 6 shows photographs of stable aqueous dispersions of grafted graphene prepared in Examples 6-8; Figure 7 shows a scanning electron microscope image of the polyethylene glycol grafted graphene prepared in Example 6; Figure 8 shows the thermogravimetric analysis diagram of the polyethylene glycol grafted graphene prepared in Example 6, where the upper curve represents flake graphite, the middle curve represents PEG grafted graphene, and the lower curve represents PEG; Figure 9 shows a scanning electron microscope image of sodium polyacrylate-grafted graphene prepared in Example 7; FIG. 10 shows a scanning electron microscope image of the xanthan gum-grafted graphene prepared in Example 8; FIG. 11 shows the thermogravimetric analysis diagram of the xanthan gum-grafted graphene prepared in Example 8, in which the upper curve represents flake graphite and the lower curve represents xanthan gum-grafted graphene; FIG. 12 shows a scanning electron microscope image of polyacrylamide-grafted graphene prepared in Example 9; FIG. 13 shows a scanning electron microscope image of the hydroxypropylmethylcellulose-grafted graphene prepared in Example 10; FIG. 14 shows a scanning electron microscope image of the sodium maleate isobutylene copolymer grafted graphene prepared in Example 11; FIG. 15 shows a scanning electron microscope image of polyethyleneimine-grafted graphene prepared in Example 13; Figure 16 shows a schematic diagram of edge grafting / functionalization of graphene and surface grafting / functionalization of graphene; FIG. 17 shows a scanning electron microscope image of the grafted graphene prepared by the ball milling process in Comparative Example 4; FIG. 18 shows Raman spectra of graphene: (A) PVA edge-grafted graphene prepared in Example 5, (B) reduced graphene oxide (Nanjing Ji Cang Nano Tech Co., Ltd., model GCNM-1), (C) carboxyl-modified graphene prepared in Comparative Example 4; FIG. 19 shows the pattern of the contact surface of the milling disc.

[0020] Detailed Description of Specific Embodiments Specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are intended to be exemplary and explanatory only and are not intended to limit the invention.

[0021] The present invention provides an edge-grafted modified graphene comprising graphene and a water-soluble polymer grafted to an edge of the graphene, wherein the mass content of the grafted water-soluble polymer is 1 to 30%, preferably 2 to 25%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, based on the total mass of the edge-grafted modified graphene, and encompasses ranges between any two of the aforementioned values.

[0022] The mass content of the water-soluble polymer grafted onto the edge-grafted modified graphene affects the dispersibility and physical properties (such as thermal conductivity and electrical conductivity) of the modified graphene. If the mass content of the water-soluble polymer is too low, the dispersibility of graphene cannot be effectively improved, and a long-term stable aqueous dispersion cannot be formed. If the mass content of the water-soluble polymer is too high, the physical properties of the graphene itself are adversely affected, resulting in a decrease in the physical properties (such as thermal conductivity and electrical conductivity) of the modified graphene. Therefore, the mass content of the water-soluble polymer should be set within an appropriate range that balances the dispersibility and physical properties (such as thermal conductivity and electrical conductivity) of the modified graphene.

[0023] In the present invention, the mass content of the water-soluble polymer grafted to the edge-grafted graphene can be measured by thermogravimetric analysis. For example, the mass loss of a sample measured from 50.00°C to 800.00°C at a heating rate of 20.00°C / min under conditions of a nitrogen flow rate of 20.0 ml / min and an equilibrium nitrogen flow rate of 40.0 ml / min is the mass content of the water-soluble polymer grafted to the graphene.

[0024] In the present invention, the term "edge" refers to the outer edge of the graphene sheet / graphene lattice. As shown in Figure 16A, "edge grafting / functionalization" means that modifying molecules are attached to the edge atoms of the graphene lattice through chemical bonds.

[0025] In the present invention, the term "surface" refers to the exposed portion of the graphene sheet / graphene lattice, excluding the outer edge. As shown in Figure 16B, "surface grafting / functionalization" means that modifying molecules are bonded to the surface atoms of the graphene lattice through chemical bonds.

[0026] In the present invention, the milling disk process and the water-soluble polymer are used in combination to subject the graphite to suitable shearing and exfoliation effects, generating reactive sites at the edges of the graphene lattice while essentially not destroying the surface of the graphene lattice, resulting in edge-grafted graphene. The term "edge-grafted graphene" means that at least 90 wt%, preferably at least 95 wt%, at least 96 wt%, at least 97 wt%, at least 98 wt%, more preferably at least 99 wt%, and most preferably 100 wt% of the grafted polymer is chemically bonded to the atoms at the edges of the graphene lattice.

[0027] In the present invention, I in the Raman spectrum of the edge-grafted graphene D / I G The average value of is 0.05 to 0.60, preferably 0.08 to 0.55, and more preferably 0.08 to 0.50, for example, from a lower limit of 0.05, 0.06, 0.07, 0.08, 0.09, or 0.10 to an upper limit of 0.40, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.55, or 0.60.

[0028] In the present invention, the edge-grafted modified graphene can form a stable aqueous dispersion in water, and this aqueous dispersion is stable for more than 10 months, preferably more than 12 months, and preferably more than 15 months under room temperature and atmospheric pressure conditions.

[0029] In the present invention, the term "water-soluble polymer" may mean either a compound form or a group form, for example, the water-soluble polymer in "a water-soluble polymer grafted to its edge" is a group form, and the water-soluble polymer in the preparation method is a compound form. Those skilled in the art can clearly distinguish the meanings referred to herein according to different contexts.

[0030] During research into the preparation of graphene by exfoliating a graphite / water slurry through a milling disk, the inventors of the present invention discovered that adding a water-soluble polymer to the system to increase the viscosity of the system can improve the graphite exfoliation effect, and unexpectedly found that the water-soluble polymer can be grafted onto the exfoliated graphene, forming a stable aqueous dispersion of the grafted graphene.

[0031] The structure and properties of the edge-grafted modified graphene of the present invention are significantly different from existing grafted graphene oxide or grafted reduced graphene oxide.

[0032] From the viewpoint of structure, the national standard GB / T30544.13-2018 distinguishes between graphene oxide and reduced graphene oxide. Graphene oxide is a chemically modified graphene obtained by oxidizing and exfoliating graphite, and its surface is highly oxidized and modified with a high oxygen content. Reduced graphene oxide is graphene oxide after the oxygen content has been reduced, and some oxygen-containing functional groups still remain, resulting in SP. 3 Chemical bond SP 2Because the graphene oxide cannot be completely reduced to chemical bonds, many topological defects remain. Therefore, the structures of graphene oxide and reduced graphene oxide are different from those of graphene. In the present invention, graphene is employed, but graphene oxide and reduced graphene oxide are not. From the viewpoint of physical properties, most of the polymer-modified graphene reported in the literature is based on a grafting reaction between oxygen-containing groups of graphene oxide and active groups of a polymer, followed by a reduction reaction to obtain polymer-grafted graphene.

[0033] According to the present invention, the water-soluble polymer may be at least one of a water-soluble natural polymer, a water-soluble semi-synthetic polymer, and a water-soluble synthetic polymer.

[0034] According to a preferred embodiment of the present invention, the water-soluble natural polymer is selected from at least one of guar gum, xanthan gum, gelatin and gum arabic.

[0035] According to a preferred embodiment of the present invention, the water-soluble semi-synthetic polymer is selected from at least one of modified starch and modified cellulose, and the modified cellulose is preferably at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and methyl cellulose.

[0036] According to a preferred embodiment of the present invention, the water-soluble synthetic polymer is selected from at least one of compounds of formula I, compounds of formula II, compounds of formula III, compounds of formula IV and salts thereof (such as sodium, potassium or ammonium salts of the corresponding copolymerized anhydride units), compounds of formula V and salts thereof (such as sodium, potassium or ammonium salts of the corresponding copolymerized anhydride units), and compounds of formula VI;

[0037] [ka]

[0038] In Formula I, R1 is H or C1-C4 alkyl, and m is an integer ≥ 400;

[0039] [ka]

[0040] In Formula II, n1 is an integer from 1 to 8, and n2 is an integer ≥ 10;

[0041] [ka]

[0042] In formula III, R2 is H or C1-C4 alkyl, M is OR3 or amino, R3 is H, an alkali metal or NH4; p is an integer ≧500;

[0043] [ka]

[0044] In formula IV, R4 is C1-C3 alkyl or phenyl, R5 is H or methyl, and a and b are each independently an integer of ≧50;

[0045] [ka]

[0046] In formula V, c and d are each independently an integer of ≥ 50;

[0047] [ka]

[0048] In Formula VI, z is an integer ≧50.

[0049] In the present invention, C1 to C4 alkyl includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl, and C1 to C3 alkyl includes methyl, ethyl, n-propyl, and isopropyl.

[0050] Furthermore, the compound of formula I is polyvinyl alcohol (PVA), and the PVA used in the present invention may be any of various types of water-soluble PVA available in the prior art, and there is no particular limitation on the degree of alcoholysis, degree of polymerization, or copolymerization units.

[0051] Furthermore, the compound of formula II is polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentylene glycol, polyhexylene glycol, polyheptylene glycol, or polyoctylene glycol.

[0052] Furthermore, the compound of formula III is polyacrylic acid, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, lithium polyacrylate, polymethacrylic acid, sodium polymethacrylate, potassium polymethacrylate, ammonium polymethacrylate, lithium polymethacrylate, or polyacrylamide.

[0053] Furthermore, the compound of formula IV can be maleic anhydride 1-butene copolymer, maleic anhydride isobutylene copolymer, maleic anhydride styrene copolymer, maleic anhydride α-methylstyrene copolymer, maleic anhydride 1-pentene copolymer, and the water-soluble synthetic polymer can be the corresponding sodium, potassium, or ammonium salt of the compound of formula IV.

[0054] Additionally, the compound of formula V is a maleic anhydride vinyl acetate copolymer, and the water-soluble synthetic polymer can also be the corresponding sodium, potassium, or ammonium salt.

[0055] Additionally, the compound of formula VI is the water-soluble polymer polyethyleneimine.

[0056] The high molecular weight compounds useful in the present invention may be conventional commercially available polymers as described above.

[0057] In one embodiment, the water-soluble synthetic polymer is selected from water-soluble natural polymers, preferably xanthan gum, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1 to 30%, preferably 1 to 15%, preferably 2 to 10%, preferably 1 to 5%, based on the total mass of the edge-grafted modified graphene. The edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted modified graphene D / I G The average value of is 0.05 to 0.60, preferably 0.06 to 0.50, and more preferably 0.08 to 0.45.

[0058] In one embodiment, the water-soluble synthetic polymer is selected from water-soluble semi-synthetic polymers, preferably hydroxypropylmethylcellulose, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1 to 30%, preferably 1 to 15%, preferably 2 to 10%, preferably 1 to 5%, based on the total mass of the edge-grafted modified graphene. The edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, more preferably more than 15 months under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted modified graphene D / I G The average value of is 0.05 to 0.60, preferably 0.06 to 0.50, and more preferably 0.08 to 0.45.

[0059] In one embodiment, the water-soluble synthetic polymer is selected from compounds of formula I, preferably polyvinyl alcohol, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1 to 30%, preferably 3 to 25%, preferably 5 to 16%, based on the total mass of the edge-grafted modified graphene. The edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, preferably more than 15 months under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted modified graphene D / I G The average value of is 0.05 to 0.60, preferably 0.08 to 0.50, and more preferably 0.09 to 0.50.

[0060] In one embodiment, the water-soluble synthetic polymer is selected from compounds of formula II, preferably polyethylene glycol, and the mass content of the grafted water-soluble polymer in the edge-grafted graphene is 1 to 30%, preferably 3 to 25%, and preferably 5 to 16%, based on the total mass of the edge-grafted graphene. The edge-grafted graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted graphene D / I G The average value of is 0.05 to 0.60, preferably 0.08 to 0.50, and more preferably 0.09 to 0.50.

[0061] In one embodiment, the water-soluble synthetic polymer is a compound of formula III, preferably selected from sodium polyacrylate or polyacrylamide, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1 to 30%, preferably 1 to 15%, preferably 2 to 10%, based on the total mass of the edge-grafted modified graphene. The edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, preferably more than 15 months under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted modified graphene D / I G The average value of is 0.05 to 0.60, preferably 0.06 to 0.50, and more preferably 0.08 to 0.45.

[0062] In one embodiment, the water-soluble synthetic polymer is selected from compounds of formula IV, preferably maleic anhydride isobutylene copolymer, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1 to 30%, preferably 3 to 25%, preferably 5 to 16%, based on the total mass of the edge-grafted modified graphene. The edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted modified graphene D / I G The average value of is 0.05 to 0.60, preferably 0.08 to 0.50, and more preferably 0.09 to 0.50.

[0063] In one embodiment, the water-soluble synthetic polymer is selected from compounds of formula V, preferably maleic anhydride vinyl acetate copolymer, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1 to 30%, preferably 3 to 25%, and preferably 5 to 16%, based on the total mass of the edge-grafted modified graphene. The edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, and more preferably more than 15 months under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted modified graphene D / I G The average value of is 0.05 to 0.60, preferably 0.08 to 0.50, and more preferably 0.09 to 0.50.

[0064] In one embodiment, the water-soluble synthetic polymer is selected from compounds of formula VI, preferably polyethyleneimine, and the mass content of the grafted water-soluble polymer in the edge-grafted graphene is 1 to 30%, preferably 3 to 25%, and preferably 5 to 16%, based on the total mass of the edge-grafted graphene. The edge-grafted graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 12 months, under room temperature and atmospheric pressure conditions. I in the Raman spectrum of the edge-grafted graphene D / I G The average value of is 0.05 to 0.60, preferably 0.08 to 0.50, and more preferably 0.09 to 0.50.

[0065] According to the present invention, the shearing and exfoliation effect of the milling disk on graphite is exerted via the polymer solution, which has a smaller destructive effect on graphene than ball milling, sand milling, etc. Therefore, the edge-grafted graphene sheets are relatively large. Specifically, the average lateral size of the edge-grafted graphene is 1 to 10 μm, preferably 2 to 5 μm.

[0066] The average lateral size of the edge-grafted graphene can be determined by randomly measuring the sizes of more than 10 graphene sheets after imaging with a scanning electron microscope (SEM) or atomic force microscope and calculating the average. The size of a single graphene sheet is measured by drawing three lines on the surface of the graphene sheet, passing as close to the center of the sheet as possible, with the angle between the lines being approximately 60°. The lengths of the graphene sheet are measured along the three lines, and the average is calculated as the size of the graphene sheet.

[0067] The present invention also provides an aqueous dispersion of edge-grafted graphene, comprising water and stably dispersed therein an edge-grafted modified graphene, the edge-grafted modified graphene being the edge-grafted modified graphene described above.

[0068] According to a preferred embodiment of the present invention, the mass fraction of the edge-grafted graphene in the aqueous dispersion is 2 to 40%, preferably 3 to 30%.

[0069] The stability period of the aqueous dispersion of the present invention under room temperature and atmospheric pressure conditions can exceed 10 months. In this context, the stability period means that no precipitation visible to the naked eye occurs during this period, specifically, the amount of precipitation is less than 1%.

[0070] The present invention also provides a method for preparing an aqueous dispersion of the above-mentioned edge-grafted modified graphene, the method comprising the steps of: The method comprises the steps of uniformly mixing a water-soluble polymer, water, and graphite, completely dissolving the water-soluble polymer and then milling the mixture in a milling disc kettle, allowing the mixture to stand after milling, and removing the precipitate to obtain an aqueous dispersion of the edge-grafted modified graphene.

[0071] Specifically, the method comprises the steps of: The process includes dissolving a water-soluble polymer in deionized water, uniformly mixing graphite into the polymer solution, milling the mixture in a milling disk kettle, allowing the mixture to stand after milling, and removing the precipitate to obtain an aqueous dispersion of the edge-grafted modified graphene.

[0072] According to the present invention, stable aqueous dispersions of edge-grafted modified graphene are prepared based on the technique of exfoliating and in situ grafting graphite by a milling disk with the aid of an aqueous solution of a water-soluble polymer.

[0073] In a preferred embodiment of the present invention, the milling is circulation milling, and the mechanical peeling device used consists of a milling disc section and a circulation section, the structure of which is shown in Figure 1. The milling disc section includes a movable milling disc, a fixed milling disc, and a rotating device, while the circulation section includes a circulation pump, a slurry storage tank, and an agitator. The material of the milling disc can be selected from metal, ceramic, glass, plastic, etc., with metal being preferred.

[0074] In the exfoliation process using milling disks, a moving / stationary milling disk transmits shear force to the graphite flakes between the milling disks through a sticky polymer aqueous solution. The graphite flakes are initially oriented along the rotational direction of the milling disks due to the action of shear stress, then slowly exfoliate into thinner graphite flakes and finally into graphene. During the exfoliation process, multiple new edges are generated, and the carbon atoms of the new edges have high activity and can react with the active groups of the water-soluble polymer in the aqueous solution to produce edge-grafted graphene.

[0075] The raw materials of the present invention mainly comprise water-soluble polymers, deionized water, and graphite, and are environmentally friendly, so milling can be carried out in an open system. Furthermore, the preparation process (e.g., circulation milling) can be operated at room temperature and atmospheric pressure. Furthermore, there are no special requirements for the atmosphere of the system. The milling of the present invention can also be carried out in a closed system.

[0076] "Room temperature" generally means that the preparation system is at an indoor temperature, for example, a temperature of about 20 °C (18 - 25 °C), and "atmospheric pressure" generally means that the preparation system is in communication with the atmosphere, for example, a pressure of -0.02 MPa < p < 0.1 MPa.

[0077] The milling conditions selected in the present invention may include the conditions that the rotation speed is 10 - 300 rpm, preferably 50 - 200 rpm, and the time is 5 - 200 hours, preferably 10 - 150 hours, more preferably 30 - 120 hours.

[0078] The water-soluble polymer selected in the present invention has two effects: (1) increasing the viscosity of the dispersion system, thereby improving the peeling effect of the milling disk on graphite flakes, and (2) grafting onto graphene to stabilize the graphene exfoliated in the aqueous solution.

[0079] In the method of the present invention, the graphite may be natural graphite and / or artificial graphite. The natural graphite may be selected from one or more of flaky graphite, block graphite, and non-crystalline graphite, and the artificial graphite may be selected from one or more of pyrolytic graphite and highly oriented pyrolytic graphite. The graphite is preferably flaky graphite. The particle size of the graphite is 5 - 8000 mesh, preferably 35 - 3000 mesh, more preferably 50 - 1600 mesh, and even more preferably 50 - 300 mesh.

[0080] According to a preferred embodiment of the present invention, first, the water-soluble polymer is mixed with water, and then graphite is added. Here, the concentration of the water-soluble polymer may be 0.3 - 80% by mass, preferably 0.5 - 50% by mass, more preferably 1 - 40% by mass, based on the total mass of the water-soluble polymer and water.

[0081] In the method of the present invention, the mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.1-50, and preferably 1:0.2-40.

[0082] In one embodiment, the water-soluble synthetic polymer is selected from water-soluble natural polymers, preferably xanthan gum, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 0.3 to 20% by mass, and preferably 0.5 to 10% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.5 to 60, and preferably 1:2 to 50.

[0083] In one embodiment, the water-soluble synthetic polymer is selected from water-soluble semi-synthetic polymers, preferably hydroxypropyl methylcellulose, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 0.3 to 20% by mass, and preferably 0.5 to 10% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.5 to 60, and preferably 1:2 to 50.

[0084] In one embodiment, the water-soluble synthetic polymer is selected from compounds of Formula I, preferably polyvinyl alcohol, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 2 to 50% by mass, and preferably 5 to 40% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.1 to 20, and preferably 1:0.2 to 10.

[0085] In one embodiment, the water-soluble synthetic polymer is selected from compounds of Formula II, preferably polyethylene glycol, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 2 to 50% by mass, and preferably 5 to 40% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.1 to 20, and preferably 1:0.2 to 10.

[0086] In one embodiment, the water-soluble synthetic polymer is a compound of Formula III, preferably selected from sodium polyacrylate or polyacrylamide, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 0.3 to 20% by mass, and preferably 0.5 to 10% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.5 to 60, and preferably 1:2 to 50.

[0087] In one embodiment, the water-soluble synthetic polymer is selected from compounds of Formula IV, preferably maleic anhydride isobutylene copolymer, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 2 to 50% by mass, more preferably 5 to 40% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.1 to 20, preferably 1:0.2 to 10.

[0088] In one embodiment, the water-soluble synthetic polymer is selected from compounds of formula V, preferably maleic anhydride vinyl acetate copolymer, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 2 to 50% by mass, preferably 5 to 40% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.1 to 20, preferably 1:0.2 to 10.

[0089] In one embodiment, the water-soluble synthetic polymer is selected from compounds of formula VI, preferably polyethyleneimine, and the concentration of the water-soluble polymer may be 0.3 to 80% by mass, preferably 2 to 50% by mass, and preferably 5 to 40% by mass, based on the total mass of the water-soluble polymer and water. The mass ratio of the water-soluble polymer to graphite may be 1:0.05 to 80, preferably 1:0.1 to 20, and preferably 1:0.2 to 10.

[0090] The present invention also provides a method for preparing the edge-grafted modified graphene or a method for purifying the edge-grafted modified graphene, the method comprising the steps of: (1) preparing an aqueous dispersion of edge-grafted graphene according to the method described above; (2) A step of filtering and drying the aqueous dispersion of edge-grafted graphene obtained in step (1) to obtain edge-grafted graphene.

[0091] The filtration can be carried out using various conventionally known methods, and is preferably carried out under reduced pressure using a microporous filtration membrane, the size of the micropores of which is 100 to 1000 nm, preferably 200 to 800 nm.

[0092] According to a preferred embodiment of the present invention, the filtering step further comprises the step of diluting the aqueous dispersion of the edge-grafted modified graphene before filtering.

[0093] According to a preferred embodiment of the present invention, the filtering step further comprises, after filtration, filtering off the liberated water-soluble polymer using (deionized) water to further purify the edge-grafted modified graphene.

[0094] The present invention also provides applications of the above-mentioned edge-grafted modified graphene or aqueous dispersion of edge-grafted modified graphene in the fields of antistatic or conductive composite polymer materials, thermally conductive composite polymer materials, multilayer composite barrier films, barrier layer materials, adsorption materials, functional coatings, antistatic or conductive fiber materials, and solar or microwave absorption materials.

[0095] According to the present invention, the milling disk process is used. Graphite dispersed in an aqueous solution of a water-soluble polymer undergoes cyclic exfoliation between milling disks. The shear force between the stationary and moving milling disks is transmitted to the graphite flakes via the tackified aqueous solution, thereby avoiding mechanical damage to the graphite sheets and achieving graphene exfoliation. Compared with ball milling, sand milling, ultrasonication, and other methods, the milling disk process effectively utilizes the exfoliation force between the milling disks and reduces damage to the graphite flakes. In particular, after tackification with a water-soluble polymer, the shear force between the milling disks is more effectively transmitted to the graphite flakes, improving exfoliation efficiency and reducing the breakage effect. Therefore, the graphene sheets prepared by the milling disk method are large, flat, and less prone to agglomeration. More importantly, the water-soluble polymer can be grafted onto the graphene, resulting in stable dispersion of the graphene in water. Therefore, the edge-modified graphene and its aqueous dispersion can be widely applied in fields such as antistatic or conductive composite polymer materials, thermally conductive composite polymer materials, multilayer composite barrier films, barrier layer materials, adsorption materials, functional coatings, antistatic or conductive fiber materials, and solar or microwave absorption materials.

[0096] The present invention will be further described with reference to the following examples, but the scope of the present invention is not limited to these examples.

[0097] All experimental reagents in the following examples were purchased commercially, except for those indicated as homemade.

[0098] The preparation equipment used in the examples is shown in Figure 1. The milling discs were homemade and made of 304 stainless steel. The milling discs had a 1.0 mm deep pattern on their contact surfaces (as shown in Figure 19) and were nitrided. The milling discs had a diameter of 28 cm, with the upper milling disc being movable and the lower milling disc being fixed. A supply hole was located in the lower milling disc. A diaphragm pump (LongerPump, model BT600-2J) was used as the circulation pump to achieve slurry circulation milling.

[0099] The infrared spectrometer used in the examples was a Nicolet IS5 (Thermo Fisher Scientific, USA). Specifically, 3.0 mL of the aqueous dispersion of polymer-grafted graphene was added to 50 mL of deionized water for dilution, and the mixture was filtered under reduced pressure using a microporous filter membrane (Tianjin Jinteng) with a pore size of 0.54 μm. The free water-soluble polymer was then filtered off using 1500 mL of deionized water. As a result, a layer of modified graphene was obtained on the surface of the filter membrane. Next, the infrared spectrum of the edge-grafted graphene was measured using the germanium crystal reflection method.

[0100] In the examples, the microscopic morphology and electron spectroscopic properties of edge-grafted graphene were observed using a scanning electron microscope (Hitachi, Japan, Model S4800). Specifically, 0.5 mL of an aqueous dispersion of polymer-grafted graphene was added to 50 mL of deionized water for dilution, and the mixture was filtered under reduced pressure using a 0.45 μm pore size polytetrafluoroethylene microporous filter membrane (Tianjin Jinteng). The free water-soluble polymer was then filtered off using 500 mL of deionized water. As a result, a layer of modified graphene was obtained on the surface of the filter membrane. After drying, the surface of the modified graphene was subjected to a gold spray treatment, and the microscopic morphology and electron spectroscopic properties of the modified graphene were then evaluated using a scanning electron microscope.

[0101] In the examples, the crystalline order of edge-grafted graphene was evaluated using a confocal Raman microscope (Renishaw, UK, Model HR 800). Specifically, 0.5 mL of the aqueous dispersion of polymer-grafted graphene was added to 50 mL of deionized water for dilution, and the mixture was filtered under reduced pressure using a microporous filter membrane (Tianjin Jinteng) with a pore size of 0.22 μm. The free water-soluble polymer was then filtered off using 500 mL of deionized water. As a result, a layer of modified graphene was obtained on the surface of the filter membrane, which was then dried. The layer was then measured using a confocal Raman microscope spectrometer (scanning range: 600-3000 cm). -1 The Raman spectrum of the modified graphene was evaluated using a laser wavelength of 532 nm, an eyepiece of 50x magnification (Olympus BX 41), and a spot diameter of approximately 1.0 μm. The Raman spectrum was measured at three points on the surface of the graphene sheet, separated by 1.0 μm. Finally, the Raman spectrum was measured at I D / I G The average value of I in the Raman spectrum was calculated. D / I G is the ratio of the intensities of the D and G peaks and represents the crystalline order of graphene. A smaller ratio indicates higher order in the prepared graphene, while a larger ratio indicates more severe damage to the graphene lattice.

[0102] The test equipment for the thermal conductivity of graphene in the examples was a German Netzsch LFA467. For the test method, please refer to the test standard GB / T22588-2008. The thermal conductivity (K) of the test sample can be calculated according to the following formula: K = α × C p ×ρ, where α is the thermal diffusivity coefficient, C pis the specific heat capacity, and ρ is the bulk density. The mechanism is that a beam of light pulses is instantaneously emitted from a laser light source at a certain set temperature, uniformly irradiating the sample surface, causing the surface temperature to rise instantaneously after absorbing the light energy, and then the surface acts as a hot edge, propagating energy in the form of heat conduction in two directions: horizontal and vertical. The corresponding temperature rise process at the center of the sample surface is continuously measured using an infrared detector, and the relationship curve of the detector signal (temperature) versus time is obtained. A correction curve is obtained by correcting using an appropriate mathematical model, and the thermal diffusion coefficient is calculated.

[0103] The surface resistivity of graphene in the examples was measured using a multimeter (Keithley, 2400) and the test method was as follows: 0.5 mL of the aqueous dispersion of polymer-grafted graphene was added to 50 mL of dilution deionized water, and filtered under reduced pressure using a microporous filtration membrane (Tianjin Jinteng) with a pore size of 0.22 μm. The free water-soluble polymer was then filtered off using 500 mL of deionized water. As a result, a layer of modified graphene was obtained on the surface of the filtration membrane. After drying, two electrodes with a distance d of 1 mm and a length L of 5 mm were coated on the surface of the graphene film using conductive silver adhesive. The surface resistance R s was measured using a multimeter, and the surface resistivity was then calculated as ρ s =R s The ratio was set to L / d.

[0104] Example 1 100.0 g of polyvinyl alcohol (PVA) (Sinopec Sichuan Vinylon Factory, brand 1799, degree of polymerization 1700) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was removed by filtration to yield a stable aqueous dispersion of PVA-grafted graphene with a grafted graphene mass fraction of 4.5%. The graphene yield was approximately 30% of the mass of the added flake graphite. Sample 1 in Figure 2 shows the stable aqueous dispersion of PVA-grafted graphene after standing for 15 months, with no visible precipitate.

[0105] 10 mL of the aqueous dispersion of PVA-grafted graphene was diluted with 200 mL of deionized water and filtered under reduced pressure through a microporous membrane with a pore size of 0.22 μm. Finally, the free PVA was removed by filtration using 2 L of deionized water, and the mixture was then dried to obtain purified PVA-grafted graphene.

[0106] Figure 3 shows a scanning electron microscope image of the prepared PVA-grafted graphene, showing that the average sheet size is approximately 2.3 μm. The two-dimensional energy spectrum of carbon and oxygen elements indicates that oxygen elements are mainly present near the edges of the graphene sheets, while carbon elements are relatively uniformly distributed, indicating that grafting occurs mainly at the edges of the graphene.

[0107] Figure 4 shows the infrared absorption spectra of pure flake graphite, pure PVA, and PVA-grafted graphene. The characteristic infrared absorption peaks of PVA and PVA-grafted graphene are identical. The infrared spectra show the same peaks at wavenumber 3288 cm. -1 The characteristic absorption peak at 2935 cm is due to the stretching vibration of the intermolecular or intramolecular –OH bond present in the aggregated form of grafted PVA molecules. -1and 2904 cm -1 The characteristic absorption peak is due to the asymmetric stretching vibration of the -CH3 and -CH2- bonds, and is at a wavenumber of 1093 cm -1 The characteristic absorption peak of the hydroxyl group due to the -CO- stretching vibration is at a wavenumber of 1142 cm. -1 The characteristic absorption peak of the graphene is due to the -C-C stretching vibration of hydroxyl groups. This indicates that PVA has been grafted onto the graphene. However, the infrared spectrum of the flake graphite does not show any characteristic absorption peaks of PVA or other active functional groups. This indicates that there are no functional groups on the surface of the flake graphite that can react with PVA. The exfoliation process using the milling disk destroys the graphite sheets, and the newly generated graphite edges contain many highly active carbon radicals. These react with PVA in the solution to finally produce PVA-edge-grafted graphene.

[0108] Figure 5 shows the thermogravimetric analysis curves of pure flake graphite, PVA-grafted graphene, and pure PVA. At 630 °C, the weight loss of pure PVA is close to 100%, indicating that the PVA has basically and completely decomposed into gas. The weight loss of flake graphite is almost zero. The weight loss of PVA-edge-grafted graphene is 14% at this temperature, indicating that the mass fraction of grafted PVA in the PVA-grafted graphene is 14%. The measured thermal conductivity coefficient of PVA-grafted graphene is 276 W / mK, the surface resistivity is 372 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.278.

[0109] Example 2 100.0 g of polyvinyl alcohol (PVA) (Sinopec Sichuan Vinylon Factory, brand 1799, degree of polymerization 1700) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 80 rpm, and the mixture was circulated and milled for 120 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of PVA-grafted graphene with a grafted graphene mass fraction of 6%. After purification according to the method in Example 1, PVA-grafted graphene was obtained. The average sheet size was approximately 2.5 μm, and the mass fraction of grafted PVA in the modified graphene was 15.6%. The graphene yield was approximately 40% of the mass of the added flake graphite. Sample 2 in Figure 2 is a stable aqueous dispersion of PVA-grafted graphene after 15 months of standing, with no visible precipitate. The measured thermal conductivity of PVA-grafted graphene is 247 W / mK, the surface resistivity is 678 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.412.

[0110] Example 3 100.0 g of polyvinyl alcohol (PVA) (Kuraray Co., Ltd., brand CP1000) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 100 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of PVA-grafted graphene with a grafted graphene mass fraction of 4.6%. After purification according to the method in Example 1, PVA-grafted graphene was obtained. The average sheet size was approximately 4.8 μm, and the PVA mass fraction in the grafted graphene was 13.1%. The graphene yield was approximately 31% of the mass of the added flake graphite. Sample 3 in Figure 2 is a stable aqueous dispersion of PVA-grafted graphene after 15 months of standing, with no visible precipitate. The measured thermal conductivity of PVA-grafted graphene is 260 W / mK, the surface resistivity is 324 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.207.

[0111] Example 4 200.0 g of polyvinyl alcohol (PVA) (Kuraray Co., Ltd., brand CP1000) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of PVA-grafted graphene with a grafted graphene mass fraction of 5.3%. After purification according to the method in Example 1, PVA-grafted graphene was obtained. The average sheet size was approximately 4.2 μm, and the PVA mass fraction in the grafted graphene was 12.8%. The graphene yield was approximately 35% of the mass of the added flake graphite. Sample 4 in Figure 2 is a stable aqueous dispersion of PVA-grafted graphene after 15 months of standing, with no visible precipitate. The measured thermal conductivity of PVA-grafted graphene is 235 W / mK, the surface resistivity is 276 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.175.

[0112] Example 5 80.0 g of polyvinyl alcohol (PVA) (Sinopec Sichuan Vinylon Factory, brand 1799, degree of polymerization 1700) was dissolved in 1000 mL of deionized water, to which 150 g of 200-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 150 rpm, and the mixture was circulated and milled for 48 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of PVA-grafted graphene with a grafted graphene mass fraction of 5.4%. After purification according to the method in Example 1, PVA-grafted graphene was obtained. The average sheet size was approximately 3.2 μm, and the PVA mass fraction in the grafted graphene was 9.8%. The graphene yield was approximately 36% of the mass of the added flake graphite. Sample 5 in Figure 2 is a stable aqueous dispersion of PVA-grafted graphene after 15 months of standing, with no visible precipitate. The measured thermal conductivity of PVA-grafted graphene is 289 W / mK, the surface resistivity is 198 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.102.

[0113] Example 6 100.0 g of polyethylene glycol (Xilong Scientific Co., Ltd., viscosity-average molecular weight 300,000) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of polyethylene glycol-grafted graphene with a grafted graphene mass fraction of 4.8%. After purification according to the method in Example 1, polyethylene glycol-grafted graphene was obtained. The average sheet size was approximately 2.7 μm, and the yield of grafted graphene was approximately 32% of the mass of the added flake graphite. Sample 6 in Figure 6 is a stable aqueous dispersion of polyethylene glycol-grafted graphene after standing for 10 months, with no visible precipitate. Figure 7 shows a scanning electron microscope image of polyethylene glycol-grafted graphene. Figure 8 shows the thermogravimetric analysis curves of pure flake graphite, polyethylene glycol-grafted graphene, and pure polyethylene glycol. At 380°C, the weight loss of pure polyethylene glycol is nearly 100%, indicating complete decomposition of the polyethylene glycol into gas. The weight loss of flake graphite is almost zero. The weight loss of polyethylene glycol-grafted graphene is 7.8% at that temperature, indicating a mass fraction of grafted polyethylene glycol in the graphene of 7.8%.

[0114] The measured thermal conductivity of polyethylene glycol-grafted graphene was 416 W / mK, the surface resistivity was 12.0 Ω, and the I D / I G The average value is 0.095.

[0115] Example 7 20.0 g of sodium polyacrylate (Sinopharm Chemical Reagent Co., Ltd., weight-average molecular weight approximately 450,000) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of sodium polyacrylate-grafted graphene with a grafted graphene mass fraction of 3.1%. After purification according to the method in Example 1, sodium polyacrylate-grafted graphene was obtained. The average sheet size was approximately 2.8 μm, and the mass fraction of sodium polyacrylate in the grafted graphene was 6.9%. The graphene yield was approximately 21% of the added graphite mass. Sample 7 in Figure 6 is a stable aqueous dispersion of sodium polyacrylate-grafted graphene after standing for 10 months, with no visible precipitate. Figure 9 shows a scanning electron microscope image of sodium polyacrylate-grafted graphene.

[0116] The measured thermal conductivity of sodium polyacrylate-grafted graphene was 288 W / mK, the surface resistivity was 31.2 Ω, and the I D / I G The average value is 0.127.

[0117] Example 8 6.0 g of xanthan gum (Meihua Holdings Group Co., Ltd., MHF-80R) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then removed by filtration, yielding a stable aqueous dispersion of xanthan gum edge-grafted graphene with a grafted graphene mass fraction of 2.8%. After purification according to the method in Example 1, xanthan gum-grafted graphene was obtained. The average sheet size was approximately 2.9 μm. The graphene yield was approximately 20% of the mass of the added flake graphite. Sample 8 in Figure 6 is a stable aqueous dispersion of xanthan gum-grafted graphene after standing for 10 months, with no visible precipitate. Figure 10 shows a scanning electron microscope image of the xanthan gum-grafted graphene. Figure 11 shows the thermogravimetric analysis curves of pure flake graphite and xanthan gum-grafted graphene. The flake graphene shows almost no weight loss. Xanthan gum-grafted graphene begins to decompose and lose weight at 280°C, but loses very little weight by 330°C, at which point the weight loss is 3.2%, indicating that the mass fraction of grafted xanthan gum in the graphene is 3.2%. The measured thermal conductivity of xanthan gum-grafted graphene is 257 W / mK, the surface resistivity is 281 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.081.

[0118] Example 9 5.0 g of polyacrylamide (Sinopharm Chemical Reagent Co., Ltd., weight-average molecular weight approximately 1,000,000) was dissolved in 1,000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of polyacrylamide-grafted graphene with a grafted graphene mass fraction of 5.25%. After purification according to the method in Example 1, polyacrylamide-grafted graphene was obtained. The average sheet size was approximately 3.1 μm, and the polyacrylamide mass fraction in the grafted graphene was 2.3%. The graphene yield was approximately 23% of the mass of the added flake graphite. The prepared aqueous dispersion can be stably stored for 15 months without precipitation. Figure 12 shows a scanning electron microscope image of polyacrylamide-grafted graphene. The measured thermal conductivity of polyacrylamide-grafted graphene is 273 W / mK, the surface resistivity is 279 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.097.

[0119] Example 10 10 g of hydroxypropyl methylcellulose (Shandong Chuangyao Biotechnology Co., Ltd., CY-50000(S)) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of hydroxypropyl methylcellulose-grafted graphene with a grafted graphene mass fraction of 3.75%. After purification according to the method in Example 1, hydroxypropyl methylcellulose-grafted graphene was obtained. The average sheet size was approximately 2.8 μm, and the hydroxypropyl methylcellulose mass fraction in the grafted graphene was 3.1%. The yield of graphene is approximately 25% of the mass of the added flake graphite. The prepared aqueous dispersion can be stored stably for 15 months without precipitation. Figure 13 shows a scanning electron microscope image of hydroxypropylmethylcellulose-grafted graphene. The measured thermal conductivity of hydroxypropylmethylcellulose-grafted graphene is 181 W / mK, the surface resistivity is 176 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.108.

[0120] Example 11 150 g of maleic anhydride isobutylene copolymer (Kuraray Co., Ltd., brand ISOBAM-18, number average molecular weight 300,000-350,000) and 100 g of sodium carbonate (Sinopharm Chemical Reagent Co., Ltd., AP) were dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then removed by filtration to yield a stable aqueous dispersion of sodium maleate-isobutylene copolymer-grafted graphene with a grafted graphene mass fraction of 4.7%. After purification according to the method in Example 1, sodium maleate-isobutylene copolymer-grafted graphene was obtained. Here, the average sheet size is approximately 2.7 μm, and the mass fraction of sodium maleate-isobutylene copolymer in the grafted graphene is 12.8%. The graphene yield is approximately 31% of the mass of the added flake graphite. Figure 14 shows a scanning electron microscope image of sodium maleate-isobutylene copolymer-grafted graphene. The prepared aqueous dispersion can be stably stored for more than 10 months. The measured thermal conductivity coefficient of sodium maleate-isobutylene copolymer-grafted graphene is 143 W / mK, the surface resistivity is 657 Ω, and the I in the Raman spectrum. D / I G The average value is 0.314.

[0121] Example 12 150 g of maleic anhydride vinyl acetate copolymer (Beijing Chemical Industry Research Institute, preparation reference: Ru Yue, Discovery, Properties and Application of A New Fluorescence / Phosphorescence Polymer Family [D], Beijing University of Chemical Technology, 2015) and 100 g of sodium carbonate (Sinopharm Chemical Reagent Co., Ltd., ap) were dissolved in 1000 mL of deionized water. 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added and the mixture was stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the mixture was circularly milled for 80 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was removed by filtration to obtain a stable aqueous dispersion of sodium maleate vinyl acetate copolymer-grafted graphene with a mass fraction of 2.7% grafted graphene. After purification according to the method of Example 1, sodium maleate-vinyl acetate copolymer-grafted graphene was obtained. The average sheet size was approximately 3.2 μm, and the mass fraction of sodium maleate-vinyl acetate copolymer in the grafted graphene was 6.8%. The graphene yield was approximately 18% of the mass of the added flake graphite. The prepared aqueous dispersion could be stably stored for more than 10 months. The measured thermal conductivity coefficient of the sodium maleate-vinyl acetate copolymer-grafted graphene was 283 W / mK, the surface resistivity was 357 Ω, and the I in the Raman spectrum was 0.01. D / I G The average value is 0.154.

[0122] Example 13 To 1000 g of an aqueous dispersion of 40% polyethyleneimine (Guohua Reagent, weight-average molecular weight 70,000), 100 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added, followed by uniform stirring. The milling disk rotation speed was set to 100 rpm, and the mixture was circulated and milled for 72 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding a stable aqueous dispersion of polyethyleneimine-grafted graphene with a grafted graphene mass fraction of 3.5%. After purification according to the method in Example 1, polyethyleneimine-grafted graphene was obtained. The average sheet size was approximately 2.5 μm, and the polyethyleneimine mass fraction in the grafted graphene was 15.9%. The graphene yield was approximately 35% of the mass of the added flake graphite. Figure 15 shows a scanning electron microscope image of polyethyleneimine-grafted graphene. The prepared aqueous dispersion can be stably stored for more than 10 months. The measured thermal conductivity of polyethyleneimine-grafted graphene is 126 W / mK, the surface resistivity is 792 Ω, and the I in the Raman spectrum is 0.01. D / I G The average value is 0.291.

[0123] Example 14 13.0 g of PVA (Sinopec Sichuan Vinylon Factory, brand 1799, degree of polymerization 1700) was dissolved in 112.0 g of deionized water, to which 5.0 g of the PVA-grafted graphene solution prepared in Example 5 was added. The mixture was then mechanically stirred to homogenize, yielding a solution containing 2% PVA-grafted graphene by mass. The solution was poured into a glass dish, and the water was evaporated at room temperature and pressure to prepare a 1.0 mm thick film. The surface resistivity of the film was 2.09 x 10 7 It is Omega.

[0124] Comparative Example 1 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added to 1000 mL of deionized water and stirred uniformly. The milling disk rotation speed was set to 100 rpm, and the resulting slurry was circulated and milled for 100 hours. The resulting graphene suspension was poured into a beaker and then allowed to stand for 10 hours. The precipitate was then removed by filtration. Only a small amount of graphene was obtained, less than 0.5% of the mass of the added flake graphite. The graphene suspension was stable for only a few days, with obvious precipitation observed after a few days. After one week, almost all of the graphene had precipitated.

[0125] Comparative Example 2 100.0 g of polyvinyl alcohol (PVA) (Sinopec Sichuan Vinylon Factory, brand 1799, degree of polymerization 1700) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 8 rpm, and the mixture was circulated and milled for 120 hours. The resulting graphene suspension was poured into a beaker and then allowed to stand for 10 hours. The precipitate was removed by filtration to yield an aqueous dispersion with a grafted graphene mass fraction of 0.13%. After purification according to the method in Example 1, graphene was obtained. The average sheet size was approximately 0.7 μm, and the grafted PVA mass fraction was 0.1%. The yield was approximately 1% of the mass of the added flake graphite. After standing for one month, obvious precipitation was observed in the aqueous dispersion. I in the measured Raman spectrum of the product D / I G The average value is 0.035.

[0126] Comparative Example 3 100.0 g of polyvinyl alcohol (PVA) (Sinopec Sichuan Vinylon Factory, brand 1799, degree of polymerization 1700) was dissolved in 1000 mL of deionized water, to which 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added. The mixture was then stirred uniformly. The milling disk rotation speed was set to 80 rpm, and the mixture was circulated and milled for 4 hours. The resulting graphene suspension was poured into a beaker and allowed to stand for 10 hours. The precipitate was then filtered off, yielding an aqueous dispersion with a grafted graphene mass fraction of 0.3%. After purification according to the method in Example 1, PVA-grafted graphene was obtained. The average sheet size was approximately 0.6 μm, and the mass fraction of grafted PVA in the modified graphene was 0.34%. The yield was approximately 2.1% of the mass of the added flake graphite. After standing for one month, the aqueous dispersion showed clear precipitation. The measured thermal conductivity was 27 W / mK, and the I D / I G The average value is 0.040.

[0127] Comparative Example 4 A stainless steel ball mill tank (pressure resistance 16.0 MPa, volume 500 mL) was filled with 1000.0 g of 5.0 mm diameter stainless steel balls and 3.0 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.). At room temperature, carbon dioxide was charged into the ball mill tank using a gas charging device until a pressure of 7.5 MPa was reached. The ball mill tank was placed on a planetary ball mill (Fritsch, Germany, Model Pulverisette 6), and ball milling was carried out at a rotation speed of 400 rpm for 48 hours. After the carbon dioxide was emptied from the ball mill tank, the steel balls were sieved out using a sieve to obtain ball-milled graphite microsheets.

[0128] The ball-milled graphite microsheets were dispersed in 500 ml of deionized water and stirred for 1 hour. Sodium hydroxide solution was added to adjust the pH of the system to a slightly alkaline level. The suspension was then left to stand for 24 hours and filtered to remove the thick precipitated graphite flakes, yielding a sodium carboxylate-modified graphene solution. This sodium carboxylate-modified graphene solution was then distilled and dried, yielding 2.4 g of black sodium carboxylate-modified graphene powder with an 80% yield. The graphene sheet size was less than 200 nm, and the grafting rate of carboxyl groups was 21.5% by mass. The measured surface resistivity of the product was 4.5 x 10 3 Ω, thermal conductivity is 0.51 W / mK, and I in the Raman spectrum D / I G The average value is 0.635.

[0129] Comparative Example 5 9.80 g of PVA (Sinopec Sichuan Vinylon Factory, brand 1799, degree of polymerization 1700) was dissolved in 90.0 g of deionized water, to which 0.2 g of the graphene prepared in Comparative Example 4 was added. The mixture was then mechanically stirred to homogenize, yielding a solution containing 2% graphene by mass in PVA. This solution was poured into a glass dish, and the water was evaporated at room temperature and pressure to prepare a 1.0 mm thick film. The surface resistivity of the film was 8.7 x 10 9 It is Omega.

[0130] As can be seen from the comparison between Example 1 and Comparative Examples 2 and 3, if the rotation speed of the milling disc is too low or the milling time is too short, the degree of exfoliation of graphene is low, the water-soluble polymer cannot be effectively grafted to graphene, and a stable aqueous dispersion cannot be formed.

[0131] As can be seen from the comparison between Examples 1, 2 and 5 and Comparative Examples 2 and 3, the content of the water-soluble polymer in the grafted graphene needs to reach a certain level to form a stable aqueous dispersion.

[0132] 18 shows the Raman spectra of graphene: (A) PVA edge-grafted graphene prepared in Example 5, (B) reduced graphene oxide (Nanjing Jicang Nanomaterial Technology Co., Ltd., model GCNM-1), and (C) carboxyl-modified graphene prepared in Comparative Example 4. I in the Raman spectrum of the PVA edge-grafted graphene of the present invention. D / I G The average value of I in the Raman spectrum of commercially available reduced graphene oxide is 0.102. D / I G The average value of (0.883) and I in the Raman spectrum of carboxyl-modified graphene prepared by ball milling method D / I G This is much lower than the average value of (0.635) indicating that the edge-grafted graphene of the present invention is more ordered and the graphene lattice is less disrupted.

[0133] A comparison of Example 14 and Comparative Example 5 shows that the PVA-based composite film containing PVA-edge-grafted graphene of the present invention has a resistivity approximately two orders of magnitude lower than that of the PVA-based composite film containing carboxyl-modified graphene prepared by ball milling, demonstrating significantly better conductivity. The main reasons for this are as follows: (1) PVA-edge-grafted graphene can be stably dispersed in water. After mixing with aqueous PVA, the graphene can be uniformly dispersed in the PVA, forming a conductive network and achieving conductivity. On the other hand, graphene prepared by ball milling is difficult to disperse in aqueous PVA; (2) compared to ball-milled graphene, PVA-edge-grafted graphene has a more complete internal structure and larger graphene size, resulting in improved conductivity.

[0134] While the present invention has been described with reference to exemplary embodiments, this description is by way of example only and is not exhaustive, and the present invention is not limited to the embodiments disclosed herein. Many modifications and variations will be apparent to those skilled in the art that do not depart from the scope and spirit of the embodiments described herein.

[0135] The range endpoints and any values ​​disclosed in this application document are not intended to be limited to the exact ranges or values, and these ranges or values ​​should be understood to encompass values ​​close to these ranges or values. For numerical ranges, the range endpoints, the range endpoints and individual point values, or the individual point values ​​can be combined with each other to create one or more new numerical ranges, which should be considered to be specifically disclosed herein. [Brief explanation of the drawings]

[0136] [Figure 1] FIG. 1 shows a schematic diagram of an apparatus for preparing an aqueous dispersion of grafted graphene according to an embodiment of the present invention. [Figure 2] Photographs of stable aqueous dispersions of polyvinyl alcohol-grafted graphene prepared in Examples 1 to 5 are shown. [Figure 3] 1 shows a scanning electron microscope image of the polyvinyl alcohol-grafted graphene prepared in Example 1, as well as two-dimensional energy spectra of carbon and oxygen elements. [Figure 4] Figure 1 shows the infrared absorption spectra of the polyvinyl alcohol-grafted graphene prepared in Example 1, as well as pure flake graphite and pure PVA. The upper curve represents flake graphite, the middle curve represents PVA, and the lower curve represents PVA-grafted graphene. [Figure 5] Figure 1 shows the thermogravimetric analysis diagrams of the polyvinyl alcohol-grafted graphene prepared in Example 1, as well as pure flake graphite and pure PVA. The upper curve represents flake graphite, the middle curve represents PVA-grafted graphene, and the lower curve represents PVA. [Figure 6]Photographs of stable aqueous dispersions of graphene prepared in Examples 6 to 8 are shown. [Figure 7] 1 shows a scanning electron microscope image of polyethylene glycol-grafted graphene prepared in Example 6. [Figure 8] Figure 6 shows the thermogravimetric analysis diagram of the polyethylene glycol-grafted graphene prepared in Example 6, where the upper curve represents flake graphite, the middle curve represents PEG-grafted graphene, and the lower curve represents PEG. [Figure 9] 1 shows a scanning electron microscope image of sodium polyacrylate-grafted graphene prepared in Example 7. [Figure 10] FIG. 1 shows a scanning electron microscope image of xanthan gum-grafted graphene prepared in Example 8. [Figure 11] 1 shows the thermogravimetric analysis diagram of the xanthan gum-grafted graphene prepared in Example 8, in which the upper curve represents flake graphite and the lower curve represents xanthan gum-grafted graphene. [Figure 12] FIG. 1 shows a scanning electron microscope image of polyacrylamide-grafted graphene prepared in Example 9. [Figure 13] FIG. 1 shows a scanning electron microscope image of hydroxypropyl methylcellulose-grafted graphene prepared in Example 10. [Figure 14] FIG. 1 shows a scanning electron microscope image of sodium maleate-isobutylene copolymer-grafted graphene prepared in Example 11. [Figure 15] FIG. 1 shows a scanning electron microscope image of polyethyleneimine-grafted graphene prepared in Example 13. [Figure 16] Schematic diagrams of edge grafting / functionalization of graphene and surface grafting / functionalization of graphene are shown. [Figure 17] 1 shows a scanning electron microscope image of grafted graphene prepared by a ball milling process in Comparative Example 4. [Figure 18]Figure 1 shows Raman spectra of graphene: (A) PVA edge-grafted graphene prepared in Example 5, (B) reduced graphene oxide (Nanjing Ji Cang Nano Tech Co., Ltd., model GCNM-1), and (C) carboxyl-modified graphene prepared in Comparative Example 4. [Figure 19] 1 shows the pattern of the contact surface of the milling disc.

Claims

1. 1. An edge-graft modified graphene comprising graphene and a water-soluble polymer grafted to an edge of the graphene, wherein the mass content of the grafted water-soluble polymer in the edge-graft modified graphene is 1 to 30%, preferably 2 to 25%, based on the total mass of the edge-graft modified graphene.

2. I in the Raman spectrum of the edge-grafted graphene Ｄ / I Ｇ and / or the average value of is 0.05 to 0.60, preferably 0.08 to 0.55; 2. The edge-grafted modified graphene of claim 1, wherein the edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable for more than 10 months, preferably more than 15 months, under room temperature and atmospheric pressure conditions.

3. 2. The edge-grafted modified graphene of claim 1, wherein the water-soluble polymer is at least one of a water-soluble natural polymer, a water-soluble semi-synthetic polymer, and a water-soluble synthetic polymer.

4. 4. The edge-grafted modified graphene of claim 3, wherein the water-soluble natural polymer is selected from at least one of guar gum, xanthan gum, gelatin, and gum arabic.

5. 4. The edge-grafted modified graphene of claim 3, wherein the water-soluble semi-synthetic polymer is selected from at least one of modified starch and modified cellulose, and the modified cellulose is preferably at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose and methyl cellulose.

6. 4. The edge-grafted modified graphene of claim 3, wherein the water-soluble synthetic polymer is selected from at least one of compounds of formula I, compounds of formula II, compounds of formula III, compounds of formula IV and salts thereof, compounds of formula V and salts thereof, and compounds of formula VI; 【Chemistry 1】 In Formula I, R １ is H or C １ ~C ４ alkyl, and m is an integer ≧400; 【Chemistry 2】 In Formula II, n １ is an integer from 1 to 8, and n ２ is an integer ≧10; 【Transformation 3】 In Formula III, R ２ is H or C １ ~C ４ alkyl and M is OR ３ or amino, and R ３ is H, an alkali metal, or NH ４ and p is an integer ≧500; 【Chemistry 4】 In Formula IV, R ４ is C １ ~C ３ alkyl or phenyl, and R ５ is H or methyl, and a and b are each independently an integer of ≥ 50; 【Transformation 5】 In formula V, c and d each independently represent an integer of ≥ 50; 【Transformation 6】 In Formula VI, z is an integer ≧50.

7. the compound of formula I is polyvinyl alcohol, and / or The compound of formula II is polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentylene glycol, polyhexylene glycol, polyheptylene glycol or polyoctylene glycol, and / or the compound of formula III is polyacrylic acid, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, lithium polyacrylate, polymethacrylic acid, sodium polymethacrylate, potassium polymethacrylate, ammonium polymethacrylate, lithium polymethacrylate, or polyacrylamide; and / or The compound of formula IV is maleic anhydride 1-butene copolymer, maleic anhydride isobutylene copolymer, maleic anhydride styrene copolymer, maleic anhydride α-methylstyrene copolymer, maleic anhydride 1-pentene copolymer, and its salts are the corresponding sodium, potassium or ammonium salts; and / or the compound of formula V is a maleic anhydride vinyl acetate copolymer, the salt of which is the corresponding sodium, potassium or ammonium salt; and / or 7. The edge-grafted graphene of claim 6, wherein the compound of formula VI is polyethyleneimine.

8. The edge-grafted modified graphene of any one of claims 1 to 7, wherein the average lateral size of the edge-grafted modified graphene is 1 to 10 μm, preferably 2 to 5 μm.

9. 9. The edge-grafted modified graphene according to any one of claims 1 to 8, wherein the edge-grafted modified graphene is prepared by a milling disk process, preferably the milling conditions include a rotation speed of 10 to 300 rpm, preferably 50 to 200 rpm, and a time of 5 to 200 hours, preferably 10 to 150 hours.

10. 10. An aqueous dispersion of edge-graft modified graphene, the aqueous dispersion comprising water and edge-graft modified graphene stably dispersed therein, wherein the edge-graft modified graphene is the edge-graft modified graphene according to any one of claims 1 to 9.

11. The aqueous dispersion according to claim 10, wherein the mass fraction of the edge-grafted modified graphene in the aqueous dispersion is 2 to 40%, preferably 3 to 30%.

12. 12. The aqueous dispersion according to claim 10 or 11, wherein the aqueous dispersion is stable under room temperature and atmospheric conditions for more than 10 months, preferably more than 15 months.

13. A method for preparing an aqueous dispersion of edge-grafted graphene according to any one of claims 10 to 12, comprising the steps of: The method comprises the steps of uniformly mixing a water-soluble polymer, water, and graphite, completely dissolving the water-soluble polymer and then milling the mixture in a milling disc kettle, allowing the mixture to stand after milling, and removing the precipitate to obtain an aqueous dispersion of the edge-grafted modified graphene.

14. The preparation method according to claim 13, wherein the graphite is natural graphite and / or artificial graphite, the natural graphite is selected from one or more of flake graphite, block graphite and amorphous graphite, the artificial graphite is selected from one or more of pyrolytic graphite and highly oriented pyrolytic graphite, the graphite is preferably flake graphite, and the particle size of the graphite is 5 to 8000 mesh, preferably 35 to 3000 mesh, more preferably 50 to 1600 mesh, and even more preferably 50 to 300 mesh.

15. The preparation method according to claim 13, wherein the milling is carried out in an open or closed system, preferably in a circulating manner at room temperature and atmospheric pressure, and the milling conditions include a rotation speed of 10 to 300 rpm, preferably 50 to 200 rpm, and a time of 5 to 200 hours, preferably 10 to 150 hours, more preferably 30 to 120 hours.

16. The preparation method according to claim 13, wherein the concentration of the water-soluble polymer is 0.3 to 80% by weight, preferably 0.5 to 50% by weight, more preferably 1 to 40% by weight, based on the total weight of the water-soluble polymer and water.

17. A method for preparing edge-grafted modified graphene according to any one of claims 1 to 9, comprising the steps of: (1) preparing an aqueous dispersion of edge-grafted graphene according to the method of any one of claims 13 to 16; (2) A step of filtering and drying the aqueous dispersion of the edge-graft-modified graphene obtained in (1) to obtain the edge-graft-modified graphene.

18. 18. The method according to claim 17, wherein the filtration is performed under reduced pressure using a microporous filtration membrane.

19. 18. The method of claim 17, wherein the filtration further comprises the steps of: diluting the aqueous dispersion of the edge-grafted graphene before filtering; and / or After filtration, filtering off the free water-soluble polymer with water.

20. Applications of the edge-grafted modified graphene according to any one of claims 1 to 9 or the aqueous dispersion of the edge-grafted modified graphene according to any one of claims 10 to 12 in the fields of antistatic or conductive composite polymer materials, thermally conductive composite polymer materials, multilayer composite barrier films, barrier layer materials, adsorption materials, functional coatings, antistatic or conductive textile materials, solar or microwave absorbing materials.

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