Edge grafting modified graphene as well as aqueous dispersion and preparation method thereof

Abstract

The invention belongs to the technical field of graphene preparation, and relates to edge grafting modified graphene as well as an aqueous dispersion and a preparation method thereof. The edge grafting modified graphene comprises graphene and a water-soluble high-molecular polymer grafted on the edge of the graphene, and the mass content of the water-soluble high-molecular polymer grafted in the edge grafting modified graphene is 1-30% based on the total mass of the edge grafting modified graphene. Compared with grinding processes such as ultrasonic, ball milling and sanding, the abrasive disk has a weak destructive effect on a graphite crystal structure, and relatively large lamellar graphene is easy to prepare. And the water-soluble high-molecular polymer can improve the viscosity of the solution and indirectly transfer the shearing force between the grinding discs to the graphite flake, so that the damage to graphite crystal lattices is further reduced, and the stripping effect of the graphite flake is improved. The water-soluble high-molecular polymer can be grafted to the graphene and has a stabilizing effect, so that a stable aqueous dispersion with the edge grafted with the modified graphene is formed.

Description

Edge-grafted modified graphene, aqueous dispersion thereof, and preparation method thereof Technical Field

[0001] The present invention belongs to the technical field of graphene preparation, and in particular relates to edge-grafted modified graphene, an aqueous dispersion of the edge-grafted modified graphene, and preparation methods thereof. Background Art

[0002] Graphene is a single layer of carbon atoms with a honeycomb structure, consisting of a single carbon atom bonded to three adjacent carbon atoms. As a novel material, graphene has attracted considerable attention for its high optical transmittance, electrical and thermal conductivity, high specific surface area, and excellent mechanical properties. Currently, graphene is in the exploratory stage of large-scale production and application. High-quality, low-cost preparation technologies for functionalized graphene are essential for future large-scale applications. Researchers have developed a range of preparation techniques, including mechanical exfoliation, redox methods, chemical vapor deposition, epitaxial growth, thermal expansion, and electrochemical methods. Both mechanical exfoliation and redox methods are based on graphite raw materials, prepared through mechanical or chemical exfoliation techniques. These methods offer abundant raw material resources, are easily controlled in cost, and are therefore more suitable for large-scale graphene production. Redox methods involve oxidizing natural graphite with a strong oxidant to introduce abundant polar groups onto its surface. Graphene oxide is then obtained through solvation or ultrasonic dispersion, and then reduced to remove the polar groups on the graphene oxide surface. However, the production process uses large amounts of strong acids and strong oxidants, such as concentrated sulfuric acid, fuming nitric acid, potassium permanganate, and perchloric acid, resulting in serious wastewater pollution. The prepared graphene has certain defects, such as topological defects such as five-membered and seven-membered rings left behind by polar groups removed by reduction, or structural defects such as hydroxyl groups. These defects will lead to the loss of some of the graphene's electrical properties, limiting its application. The national standard GB / T30544.13-2018, "Nanotechnology - Terminology Part 13: Graphene and Related Two-Dimensional Materials," separately defines graphene oxide and reduced graphene oxide to distinguish between graphene.

[0003] The surface of graphene obtained by oxidation contains abundant oxygen-containing groups, such as epoxy, hydroxyl and carboxyl groups, which can be covalently modified by chemical reactions. Salavagione HJ et al. (Salavagione HJ, G Martínez, MA Gómez. 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.) grafted PVA onto graphene oxide through an esterification reaction between the hydroxyl groups on PVA and the carboxyl groups on graphene oxide to obtain PVA-grafted graphene oxide. Wang Bo et al. (Wang Bo, He Shengfu, Zhang Fan, et al. Preparation of dendritic polyamide-amine grafted graphene oxide and its adsorption kinetics and thermodynamics 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 Cell Imaging of PEG-Grafted Graphene Oxide [J]. 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-Type Thermotropic Liquid Crystal Grafted Graphene Oxide [J]. Polymer Materials Science and Engineering, 2013, 29(007):17-20) studied biphenyl-type thermotropic liquid crystal grafted graphene oxide. Both of them used the abundant active groups on the surface of graphene oxide prepared by oxidation to prepare grafted graphene oxide. However, the grafting technology based on graphene oxide still has topological defects such as five-membered rings and seven-membered rings and residual oxygen-containing groups on the graphene surface. These technologies belong to PVA-grafted graphene oxide or PVA-grafted reduced graphene oxide.

[0004] Commonly used mechanical exfoliation methods include ball milling, sand milling, and ultrasonic methods. Although these methods can produce graphene on a large scale, due to the strong destructive effect of mechanical forces, graphene is severely damaged, and the graphene size is often small, even less than 100 nanometers. Therefore, a key technical point of mechanical exfoliation is to reduce destructiveness and produce larger-sized graphene. In addition, due to the strong mechanical forces, ball milling, sand milling, and ultrasonic methods may lead to a greater degree of surface grafting of graphene, and excessive surface grafting will negatively affect the excellent electrical and thermal conductivity of graphene itself. Therefore, another key technical point of mechanical exfoliation is to reduce surface grafting and produce edge-grafted graphene.

[0005] Stable aqueous graphene dispersions are widely used in the fields of chemical industry, electronics, energy, medicine, etc. However, there is still a need in the art for an efficient and low-cost method for obtaining aqueous graphene dispersions that are stable for a long period of time, such as one year or longer.

[0006] Therefore, one object of the present invention is to provide edge-grafted modified graphene of relatively large size, capable of forming a stable aqueous dispersion for a long period of time, and exhibiting desirable electrical and thermal conductivity. Another object of the present invention is to provide an efficient and cost-effective method for preparing such edge-grafted modified graphene and its stable aqueous dispersion.

[0007] Summary of the Invention

[0008] The present invention provides an edge-grafted modified graphene, a stable aqueous dispersion of the edge-grafted modified graphene, and a preparation method thereof.

[0009] The first aspect of the present invention provides an edge-grafted modified graphene, which includes graphene and a water-soluble polymer grafted on its edge. Based on the total mass of the edge-grafted modified graphene, the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 2-25%.

[0010] A second aspect of the present invention provides an aqueous dispersion of edge-grafted modified graphene, wherein the aqueous dispersion comprises water and edge-grafted modified graphene stably dispersed therein, wherein the edge-grafted modified graphene is the above-mentioned edge-grafted modified graphene.

[0011] A third aspect of the present invention provides a method for preparing the above-mentioned aqueous dispersion of edge-grafted modified graphene, comprising the following steps:

[0012] The water-soluble polymer, water and graphite are mixed evenly, and after the water-soluble polymer is completely dissolved, the mixture is ground in a grinding wheel kettle. After the grinding is completed, the mixture is allowed to stand and the precipitate is removed to obtain the aqueous dispersion of the edge-grafted modified graphene.

[0013] A fourth aspect of the present invention provides a method for preparing the above-mentioned edge-grafted modified graphene, comprising the following steps:

[0014] (1) preparing an aqueous dispersion of edge-grafted modified graphene according to the above method;

[0015] (2) filtering and drying the aqueous dispersion of the edge-grafted modified graphene obtained in step (1) to obtain the edge-grafted modified graphene.

[0016] The fifth aspect of the present invention provides the application of the above-mentioned edge-grafted modified graphene or the aqueous dispersion of the above-mentioned edge-grafted modified graphene in the fields of antistatic or conductive composite polymer materials, thermal conductive composite polymer materials, multi-layer composite barrier film barrier layer materials, adsorption materials, functional coatings, antistatic or conductive fiber materials, and sunlight or microwave absorbing materials.

[0017] The edge-grafted modified graphene and its aqueous dispersion of the present invention have the following advantages:

[0018] 1. Compared with ultrasonic, ball milling, sand milling and other grinding processes, the grinding wheel has a weaker destructive effect on the graphite crystal structure and is easy to prepare larger flake graphene.

[0019] 2. Water-soluble polymers can increase the viscosity of the solution and indirectly transfer the shear force between the grinding discs to the graphite sheets, further reducing the damage to the graphite lattice, better retaining the properties of graphene, and improving the exfoliation effect of the graphite sheets.

[0020] 3. The water-soluble polymer can be grafted to the edge of graphene and has a stabilizing effect, forming a stable aqueous dispersion of edge-grafted modified graphene.

[0021] 4. The stable edge-grafted modified graphene is easy to separate from the precipitated graphite sheets, so the preparation process of the modified graphene of the present invention is very simple.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0024] FIG1 is a schematic diagram of a device for preparing a grafted graphene aqueous dispersion according to one embodiment of the present invention;

[0025] FIG2 is a photograph of the stable aqueous dispersion of polyvinyl alcohol-grafted graphene prepared in Examples 1-5;

[0026] FIG3 is a scanning electron microscope photograph of polyvinyl alcohol-grafted graphene prepared in Example 1 and a two-dimensional energy spectrum diagram of carbon and oxygen elements;

[0027] Figure 4 is an infrared absorption spectrum of polyvinyl alcohol-grafted graphene, pure flake graphite, and pure PVA prepared in Example 1, where the upper curve represents flake graphite, the middle curve represents PVA, and the lower curve represents PVA-grafted graphene;

[0028] Figure 5 is a thermogravimetric analysis of polyvinyl alcohol-grafted graphene, pure flake graphite, and pure PVA prepared in Example 1, where the upper curve represents flake graphite, the middle curve represents PVA-grafted graphene, and the lower curve represents PVA;

[0029] FIG6 is a photograph of the stable aqueous dispersion of grafted graphene prepared in Examples 6-8;

[0030] FIG7 is a scanning electron microscope photograph of polyethylene glycol-grafted graphene prepared in Example 6;

[0031] Figure 8 is a thermogravimetric analysis curve of 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;

[0032] FIG9 is a scanning electron microscope photograph of sodium polyacrylate grafted graphene prepared in Example 7;

[0033] FIG10 is a scanning electron microscope photograph of xanthan gum grafted graphene prepared in Example 8;

[0034] Figure 11 is a thermogravimetric analysis curve of xanthan gum grafted graphene prepared in Example 8, the upper curve represents flake graphite, and the lower curve represents xanthan gum grafted graphene;

[0035] FIG12 is a scanning electron microscope photograph of polyacrylamide-grafted graphene prepared in Example 9;

[0036] FIG13 is a scanning electron micrograph of hydroxypropyl methylcellulose grafted graphene prepared in Example 10;

[0037] FIG14 is a scanning electron micrograph of the sodium maleate isobutylene copolymer grafted graphene prepared in Example 11;

[0038] FIG15 is a scanning electron microscope photograph of polyethyleneimine grafted graphene prepared in Example 13;

[0039] FIG16 is a schematic diagram of graphene edge grafting / functionalization and graphene surface grafting / functionalization;

[0040] FIG17 is a scanning electron microscope photograph of the grafted graphene prepared by ball milling in Comparative Example 4;

[0041] FIG18 is a Raman spectrum of graphene: (A) PVA edge-grafted graphene prepared in Example 5, (B) reduced graphene oxide (Nanjing Jicang Nanomaterial Technology Co., Ltd., model GCNM-1), (C) carboxyl-modified graphene prepared in Comparative Example 4;

[0042] Figure 19 shows the contact surface pattern of the grinding disc. DETAILED DESCRIPTION

[0043] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0044] The present invention provides an edge-grafted modified graphene, comprising graphene and a water-soluble polymer grafted onto the edge of the edge-grafted modified graphene. The weight content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 2-25%, based on the total weight of the edge-grafted modified graphene, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, and any range between any two of the above values.

[0045] The mass content of the water-soluble high molecular polymer grafted in the edge-grafted modified graphene has an impact on the dispersibility and physicals (such as thermal conductivity and conductivity) of modified graphene. If the mass content of the water-soluble high molecular polymer is too low, then the dispersibility of Graphene can not be improved effectively, causes and cannot form long-time stable aqueous dispersion. If the mass content of the water-soluble high molecular polymer is too high, then adversely affects the physicals of Graphene itself, causes the physicals (such as thermal conductivity and conductivity) of modified graphene to deteriorate. Therefore, the mass content of the water-soluble high molecular polymer should be in the appropriate scope, to obtain the balance of the dispersibility and physicals (such as thermal conductivity and conductivity) of modified graphene.

[0046] In the present invention, the mass content of the grafted water-soluble polymer portion of the edge-grafted modified graphene can be measured by thermogravimetric analysis. For example, under conditions of a sample nitrogen flow rate of 20.0 ml / min and a balance nitrogen flow rate of 40.0 ml / min, the sample is heated from 50.00°C to 800.00°C at a rate of 20.00°C / min. The mass loss of the sample is the mass content of the water-soluble polymer grafted to the graphene.

[0047] In the present invention, the term "edge" refers to the outer edge of a graphene sheet / graphene lattice. As shown in FIG16A , "edge grafting / functionalization" refers to the attachment of modified molecules to atoms at the edge of the graphene lattice via chemical bonds.

[0048] In the present invention, the term "surface" refers to the exposed locations of a graphene sheet / graphene lattice other than the edges. As shown in FIG16B , "surface grafting / functionalization" refers to the attachment of modified molecules to atoms on the surface of the graphene lattice via chemical bonds.

[0049] In the present invention, due to the combination of the disc grinding process and the water-soluble high molecular polymer, the graphite undergoes moderate shearing and exfoliation, generating reactive sites at the edges of the graphene lattice while substantially leaving the surface of the graphene lattice intact. The resulting graphene is edge-grafted modified graphene. The term "edge-grafted modified graphene" means that at least 90% by weight, preferably at least 95% by weight, at least 96% by weight, at least 97% by weight, at least 98% by weight, more preferably at least 99% by weight, and most preferably 100% by weight of the grafted polymer is chemically bonded to atoms at the edges of the graphene lattice.

[0050] In the present invention, the Raman spectrum of the edge-grafted modified graphene is D / I G The average value is 0.05-0.60, preferably 0.08-0.55, preferably 0.08-0.50. 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.

[0051] In the present invention, the edge-grafted modified graphene can form a stable aqueous dispersion in water, and the aqueous dispersion is stable at room temperature and normal pressure for more than 10 months, preferably more than 12 months, and preferably more than 15 months.

[0052] In the present invention, the term "water-soluble polymer" may refer to either a compound form or a group form. For example, the water-soluble polymer in "a water-soluble polymer grafted onto the edge thereof" refers to a group form, while the water-soluble polymer in the preparation method refers to a compound form. Those skilled in the art will be able to clearly distinguish the meanings according to different contexts.

[0053] During their research on preparing graphene by grinding wheel exfoliation of graphite / water slurry, 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. Moreover, surprisingly, the water-soluble polymer can be grafted onto the exfoliated graphene and can form a stable aqueous dispersion of grafted modified graphene.

[0054] The structure and properties of the edge-grafted modified graphene of the present invention are significantly different from those of the existing grafted graphene oxide or grafted reduced graphene oxide.

[0055] From a structural point of view, the national standard GB / T30544.13-2018 defines graphene oxide and reduced graphene oxide separately. Graphene oxide is a chemically modified graphene obtained by oxidizing and exfoliating graphite. Its surface has been strongly oxidized and modified, and its oxygen content is high. Reduced graphene oxide is graphene oxide with reduced oxygen content. In fact, some oxygen-containing functional groups still remain, and SP 3 Chemical bonds cannot be completely reduced to SP 2 Chemical bonds are formed, leaving many topological defects. Therefore, the structures of graphene oxide and reduced graphene oxide are quite different from those of graphene. The present invention utilizes graphene, not graphene oxide or reduced graphene oxide. In terms of properties, most polymer-modified graphene reported in the literature is based on the grafting reaction between oxygen-containing groups of graphene oxide and active groups of polymers, followed by reduction to prepare the polymer-grafted graphene.

[0056] According to the present invention, the water-soluble high molecular polymer may be at least one of a water-soluble natural high molecular polymer, a water-soluble semi-synthetic high molecular polymer and a water-soluble synthetic high molecular polymer.

[0057] According to a preferred embodiment of the present invention, the water-soluble natural high molecular polymer is at least one selected from guar gum, xanthan gum, gelatin and gum arabic.

[0058] According to a preferred embodiment of the present invention, the water-soluble semi-synthetic high molecular weight polymer is selected from at least one of modified starch and modified cellulose. Further, the modified cellulose is preferably at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose and methyl cellulose.

[0059] According to a preferred embodiment of the present invention, the water-soluble synthetic high molecular polymer is selected from at least one of the compounds represented by formula I, the compounds represented by formula II, the compounds represented by formula III, the compounds represented by formula IV and their salts (such as the sodium, potassium or ammonium salts corresponding to the co-polyanhydride units), the compounds represented by formula V and their salts (such as the sodium, potassium or ammonium salts corresponding to the co-polyanhydride units) and the compounds represented by formula VI;

[0060] In formula I, R1 is H or C1-C4 alkyl; m is an integer ≥ 400;

[0061] In formula II, n1 is an integer of 1-8; n2 is an integer ≥10;

[0062] In formula III, R2 is H or C1-C4 alkyl; M is OR3 or amine, R3 is H, alkali metal or NH4; p is an integer ≥500;

[0063] In formula IV, R4 is a C1-C3 alkyl group or a phenyl group, R5 is H or a methyl group, and a and b are each independently an integer ≥50;

[0064] In formula V, c and d are each independently an integer ≥ 50;

[0065] In Formula VI, z is an integer ≥50.

[0066] In the present invention, the C1-C4 alkyl group includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl; and the C1-C3 alkyl group includes methyl, ethyl, n-propyl, and isopropyl.

[0067] Furthermore, the compound represented by formula I is polyvinyl alcohol (PVA); the PVA selected in the present invention can be various types of water-soluble PVA available in various prior arts, and there is no particular limitation on the degree of alcoholysis, degree of polymerization, and copolymerization units.

[0068] Furthermore, the compound represented by formula II is polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentanediol, polyethylene glycol, polyheptanediol or polyoctanediol.

[0069] Furthermore, the compound represented by 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.

[0070] Furthermore, the compound represented by formula IV is a maleic anhydride 1-butene copolymer, a maleic anhydride isobutylene copolymer, a maleic anhydride styrene copolymer, a maleic anhydride α-methylstyrene copolymer, or a maleic anhydride 1-pentene copolymer, and the water-soluble synthetic polymer may also be the sodium, potassium or ammonium salt corresponding to the compound represented by formula IV above.

[0071] Furthermore, the compound represented by formula V is a maleic anhydride-vinyl acetate copolymer, and the water-soluble synthetic high molecular polymer may also be its corresponding sodium, potassium or ammonium salt.

[0072] Furthermore, the compound represented by formula VI is a water-soluble polymer polyethyleneimine.

[0073] The polymer compounds that can be used in the present invention can all be conventional commercially available polymers.

[0074] In one embodiment, the water-soluble synthetic polymer is selected from a water-soluble natural polymer, preferably xanthan gum, and the weight content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 1-15%, preferably 2-10%, and preferably 1-5%, based on the total weight 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 at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is shown in FIG. D / I G The average value is 0.05-0.60, preferably 0.06-0.50, and preferably 0.08-0.45.

[0075] In one embodiment, the water-soluble synthetic polymer is selected from a water-soluble semi-synthetic polymer, preferably hydroxypropyl methylcellulose. The mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 1-15%, preferably 2-10%, and preferably 1-5%, 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, and preferably more than 15 months at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is shown in FIG. D / I G The average value is 0.05-0.60, preferably 0.06-0.50, and preferably 0.08-0.45.

[0076] In one embodiment, the water-soluble synthetic polymer is selected from the compound shown in Formula I, preferably polyvinyl alcohol, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 3-25%, and preferably 5-16%, 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 preferably more than 15 months at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is shown in FIG. D / I G The average value is 0.05-0.60, preferably 0.08-0.50, and preferably 0.09-0.50.

[0077] In one embodiment, the water-soluble synthetic polymer is selected from the compound shown in Formula II, preferably polyethylene glycol, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 3-25%, and preferably 5-16%, 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 at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is shown in FIG. D / I G The average value is 0.05-0.60, preferably 0.08-0.50, and preferably 0.09-0.50.

[0078] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by formula III, preferably sodium polyacrylate or polyacrylamide, and the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 1-15%, and preferably 2-10%, 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, and preferably more than 15 months at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is shown in FIG. D / I G The average value is 0.05-0.60, preferably 0.06-0.50, and preferably 0.08-0.45.

[0079] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by formula IV, preferably maleic anhydride isobutylene copolymer, and the weight content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 3-25%, and preferably 5-16%, based on the total weight 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 at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is shown in FIG. D / I G The average value is 0.05-0.60, preferably 0.08-0.50, and preferably 0.09-0.50.

[0080] In one embodiment, the water-soluble synthetic polymer is selected from the compound shown in 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 1-30%, preferably 3-25%, and preferably 5-16%, 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 preferably more than 15 months at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is I D / I G The average value is 0.05-0.60, preferably 0.08-0.50, and preferably 0.09-0.50.

[0081] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by formula VI, preferably polyethyleneimine, and the weight content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 3-25%, and preferably 5-16%, based on the total weight 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 at room temperature and normal pressure. The Raman spectrum of the edge-grafted modified graphene is shown in FIG. D / I G The average value is 0.05-0.60, preferably 0.08-0.50, and preferably 0.09-0.50.

[0082] According to the present invention, the shearing and peeling effect of the grinding wheel is achieved by acting on graphite through the polymer solution, and the destructive effect on graphene is smaller than that of ball milling, sand milling and other methods. Therefore, the edge-grafted graphene sheets are relatively large. Specifically, the average sheet diameter of the edge-grafted modified graphene is 1-10 μm, preferably 2-5 μm.

[0083] The average sheet diameter of the edge-grafted modified graphene can be determined by randomly measuring the sizes of at least 10 graphene sheets after imaging using a scanning electron microscope (SEM) or atomic force microscope, and calculating the average. The size of a single graphene sheet can be measured by drawing three lines on the surface of the graphene sheet, with the lines extending as close as possible through the center of the sheet, with the angles between the lines being approximately 60°. The lengths of the graphene sheets are measured along these three lines, and the average value is calculated as the size of the graphene sheet.

[0084] The present invention also provides an aqueous dispersion of edge-grafted modified graphene, which comprises water and edge-grafted modified graphene stably dispersed therein, and the edge-grafted modified graphene is the edge-grafted modified graphene described above.

[0085] According to a preferred embodiment of the present invention, the mass fraction of the edge-grafted modified graphene in the aqueous dispersion is 2-40%, preferably 3-30%.

[0086] The aqueous dispersion of the present invention can be stable for more than 10 months at room temperature and normal pressure. The stable period of the present invention means that no visible precipitation occurs during this period, specifically, the amount of precipitation is less than 1%.

[0087] The present invention also provides a method for preparing the aqueous dispersion of the edge-grafted modified graphene, comprising the following steps:

[0088] The water-soluble polymer, water and graphite are mixed evenly, and after the water-soluble polymer is completely dissolved, the mixture is ground in a grinding wheel kettle. After the grinding is completed, the mixture is allowed to stand and the precipitate is removed to obtain the aqueous dispersion of the edge-grafted modified graphene.

[0089] Specifically, the method includes the following steps:

[0090] The water-soluble high molecular polymer is dissolved in deionized water, and then graphite is evenly mixed in the polymer solution, and ground in a grinding wheel kettle. After the grinding is completed, the graphite is allowed to stand and the precipitate is removed to obtain the water dispersion of the edge-grafted modified graphene.

[0091] The invention is based on the use of a water-soluble high molecular polymer aqueous solution to assist a grinding disc in exfoliating graphite and an in-situ grafting technology to prepare a stable aqueous dispersion of edge-grafted modified graphene.

[0092] According to a preferred embodiment of the present invention, the grinding process employs circulating grinding, using a mechanical stripping device consisting of a grinding disc and a circulating device. A schematic diagram of the structure is shown in Figure 1. The grinding disc portion includes a movable grinding disc, a fixed grinding disc, and a rotating device, while the circulating device includes a circulating pump, a slurry storage tank, and a stirring device. The grinding disc can be made of metal, ceramic, glass, plastic, etc., with metal being preferred.

[0093] During the exfoliation process, the moving and stationary grinding discs transmit shear forces to the graphite flakes between the discs through a polymer-thickened aqueous solution. Under the shear stress, the graphite flakes are first oriented in the direction of the discs' rotation, then slowly exfoliated into thinner sheets, ultimately forming graphene. During the exfoliation process, many new edges are generated. These highly reactive carbon atoms react with the active groups of the waterborne polymer in the aqueous solution to form edge-grafted graphene.

[0094] The raw materials of the present invention are primarily water-soluble polymers, deionized water, and graphite, which are environmentally friendly. Therefore, milling can be performed in an open system. This also means that the preparation process can be performed at room temperature and atmospheric pressure (e.g., circulating milling) and has no specific requirements for the system atmosphere. The milling of the present invention can also be performed in a closed system.

[0095] “Room temperature” generally refers to the preparation system being at room temperature, such as a temperature of about 20°C (18-25°C), and “normal pressure” generally refers to the preparation system being connected to the atmosphere, such as a pressure of -0.02MPa<p<0.1MPa.

[0096] The grinding conditions selected in the present invention may include: a rotation speed of 10-300 rpm, preferably 50-200 rpm; a time of 5-200 hours, preferably 10-150 hours, more preferably 30-120 hours.

[0097] The water-soluble high molecular weight polymer selected in the present invention has two functions: (1) increasing the viscosity of the dispersion system to improve the exfoliation effect of the grinding disc on the graphite sheet, and (2) grafting to the graphene and stabilizing the exfoliated graphene in the aqueous solution.

[0098] 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 flake graphite, block graphite, and cryptocrystalline graphite. The artificial graphite may be selected from one or more of pyrolytic graphite and highly oriented pyrolytic graphite. The graphite is preferably flake graphite. The graphite particle size may be 5-8000 mesh, preferably 35-3000 mesh, more preferably 50-1600 mesh, and more preferably 50-300 mesh.

[0099] According to a preferred embodiment of the present invention, a water-soluble polymer and water are first mixed, and then graphite is added. Based on the total mass of the water-soluble polymer and water, the mass percentage concentration of the water-soluble polymer can be 0.3-80%, preferably 0.5-50%, and more preferably 1-40%.

[0100] In the method of the present invention, the mass ratio of the water-soluble polymer to the graphite can be 1:0.05-80, preferably 1:0.1-50, and preferably 1:0.2-40.

[0101] In one embodiment, the water-soluble synthetic polymer is selected from a water-soluble natural polymer, preferably xanthan gum. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 0.3-20%, and more preferably 0.5-10%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.5-60, and more preferably 1:2-50.

[0102] In one embodiment, the water-soluble synthetic polymer is selected from a water-soluble semi-synthetic polymer, preferably hydroxypropyl methylcellulose. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 0.3-20%, and more preferably 0.5-10%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.5-60, and more preferably 1:2-50.

[0103] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by Formula I, preferably polyvinyl alcohol. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 2-50%, and more preferably 5-40%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.1-20, and more preferably 1:0.2-10.

[0104] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by Formula II, preferably polyethylene glycol. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 2-50%, and more preferably 5-40%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.1-20, and more preferably 1:0.2-10.

[0105] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by Formula III, preferably sodium polyacrylate or polyacrylamide. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 0.3-20%, and more preferably 0.5-10%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.5-60, and more preferably 1:2-50.

[0106] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by Formula IV, preferably maleic anhydride isobutylene copolymer. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 2-50%, and more preferably 5-40%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.1-20, and more preferably 1:0.2-10.

[0107] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by Formula V, preferably maleic anhydride-vinyl acetate copolymer. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 2-50%, and more preferably 5-40%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.1-20, and more preferably 1:0.2-10.

[0108] In one embodiment, the water-soluble synthetic polymer is selected from the compound represented by Formula VI, preferably polyethyleneimine. The mass percentage concentration of the water-soluble polymer, based on the total mass of the water-soluble polymer and water, may be 0.3-80%, preferably 2-50%, and more preferably 5-40%. The mass ratio of the water-soluble polymer to the graphite may be 1:0.05-80, preferably 1:0.1-20, and more preferably 1:0.2-10.

[0109] The present invention also provides a method for preparing the edge-grafted modified graphene or a method for purifying the edge-grafted modified graphene, comprising the following steps:

[0110] (1) preparing an aqueous dispersion of edge-grafted modified graphene according to the aforementioned method;

[0111] (2) filtering and drying the aqueous dispersion of the edge-grafted modified graphene obtained in step (1) to obtain the edge-grafted modified graphene.

[0112] The filtration can be carried out by various conventional methods. Preferably, the filtration is carried out by vacuum filtration using a microporous filtration membrane with a micropore size of 100-1000 nm, preferably 200-800 nm.

[0113] According to a preferred embodiment of the present invention, the filtering step further comprises diluting the aqueous dispersion of the edge-grafted modified graphene before filtering.

[0114] According to a preferred embodiment of the present invention, the filtration step further comprises filtering out free water-soluble polymers with (deionized) water after filtration to further purify the edge-grafted modified graphene.

[0115] The present invention also provides the use of the above-mentioned edge-grafted modified graphene or the aqueous dispersion of the above-mentioned edge-grafted modified graphene in the fields of antistatic or conductive composite polymer materials, thermal conductive composite polymer materials, multi-layer composite barrier film barrier layer materials, adsorption materials, functional coatings, antistatic or conductive fiber materials, and sunlight or microwave absorbing materials.

[0116] The present invention uses a disc milling process to disperse graphite in an aqueous solution of a water-soluble polymer. The process then undergoes a cyclic peeling process between the grinding discs. The shearing action between the fixed and movable grinding discs is transmitted to the graphite flakes via the thickened aqueous solution, preventing mechanical damage to the graphite flakes and enabling the peeling of graphite to produce graphene. Compared to methods such as ball milling, sand milling, and ultrasound, the disc milling process effectively utilizes the peeling force between the grinding discs, reducing the breakage of the graphite flakes. Especially after the water-soluble polymer is thickened, the shearing force between the grinding discs is more effectively transmitted to the graphite flakes, which can improve peeling efficiency and reduce destructive effects. Therefore, the graphene flakes produced by the disc milling process are larger, smoother, and less prone to agglomeration. More significantly, the water-soluble polymer can be grafted onto graphene, allowing the graphene to be stably dispersed in water. Therefore, the edge-modified graphene and its aqueous dispersion of the present invention have broad applications in the fields of antistatic or conductive composite polymer materials, thermal conductive composite polymer materials, multi-layer composite barrier film barrier layer materials, adsorption materials, functional coatings, antistatic or conductive fiber materials, sunlight or microwave absorbing materials, etc.

[0117] The present invention will be further described below with reference to the examples, but the scope of the present invention is not limited to these examples.

[0118] All experimental reagents in the following examples were commercially purchased unless marked as homemade.

[0119] The preparation apparatus used in the examples is shown in FIG1 . The grinding discs were homemade and made of 304 stainless steel. The contact surface of the grinding discs was machined with a 1.0 mm deep pattern (as shown in FIG19 ). The surface was nitrided and hardened. The grinding discs had a diameter of 28 cm. The upper grinding disc was a movable grinding disc, the lower grinding disc was a fixed grinding disc, and the feed port was located on the lower grinding disc. A diaphragm pump (LongerPump, model: BT600-2J) was used as a circulation pump to achieve slurry circulation grinding.

[0120] The infrared spectrometer used in the examples was a Thermo Fisher Scientific Nicolet IS5. Specifically, 3.0 mL of the polymer-grafted graphene aqueous dispersion was diluted with 50 mL of deionized water. The dispersion was then filtered under reduced pressure using a 0.54-μm pore size microporous filter membrane (Tianjin Jinteng). Free water-soluble polymer was then removed using 1500 mL of deionized water, resulting in a layer of modified graphene on the membrane surface. The infrared spectrum of the edge-grafted graphene was then measured using the germanium crystal reflectometry method.

[0121] In the embodiment, a scanning electron microscope (Hitachi, Japan, model S4800) was used to observe the microscopic morphology and electron energy spectrum of the edge-grafted graphene. Specifically, 0.5 ml of a polymer-grafted graphene aqueous dispersion was added to 50 mL of deionized water for dilution, and a polytetrafluoroethylene microporous filter membrane (Tianjin Jinteng) with a 0.45 micron pore size was used for decompression filtration. Then, 500 mL of deionized water was used to filter out free water-soluble polymers, and a layer of modified graphene was obtained on the filter membrane surface. After drying, the surface was sprayed with gold, and then the microscopic surface morphology and electron energy spectrum of the modified graphene were characterized by a scanning electron microscope.

[0122] In the examples, confocal micro-Raman spectroscopy (Renishaw, UK, model HR800) was used to characterize the crystal regularity of edge-grafted graphene. Specifically, 0.5 ml of polymer-grafted graphene aqueous dispersion was diluted with 50 mL of deionized water, filtered under reduced pressure using a microporous filter membrane with a pore size of 0.22 microns (Tianjin Jinteng), and then 500 mL of deionized water was used to filter out free water-soluble polymers. A layer of modified graphene was obtained on the surface of the filter membrane and dried. Then, a confocal micro-Raman spectrometer was used to characterize the Raman spectrum of the modified graphene, with a scanning range of 600-3000 cm -1 , laser wavelength 532nm, 50× eyepiece (Olympus BX41), spot diameter about 1.0μm. Take three points on the surface of a piece of graphene to measure the Raman spectrum, with a distance of 1.0μm between the points, and finally calculate its I D / I G The average value of I in Raman spectrum D / I G It is the ratio of the peak intensities of the D peak and the G peak, which can characterize the regularity of the graphene crystal. The lower the ratio, the more regular the prepared graphene is, and the larger the ratio, the more serious the graphene lattice damage is.

[0123] The thermal conductivity of graphene in the embodiment was tested using a German NETZSCH LFA467 instrument. The test method was based on the GB / T22588-2008 test standard. The thermal conductivity (K) of the test sample can be calculated using the following formula: K = α × C p ×ρ, where α is the thermal diffusion coefficient, C p The mechanism is that at a set temperature, a laser source instantaneously emits a light pulse, evenly irradiating the sample surface. The surface absorbs the light energy, causing the temperature to rise instantaneously. This surface acts as a hot end, transmitting the energy in both the plane and perpendicular directions via heat conduction. An infrared detector continuously measures the corresponding temperature rise at the center of the sample surface, generating a curve of the detector signal (temperature) versus time. This curve is then corrected using an appropriate mathematical model to produce a correction curve, from which the thermal diffusion coefficient is calculated.

[0124] The graphene surface resistivity test instrument in the embodiment is a multimeter (Keithley, 2400). The test method is as follows: 0.5 ml of the polymer-grafted graphene aqueous dispersion is diluted with 50 mL of deionized water, and the mixture is filtered under reduced pressure using a microporous filter membrane with a pore size of 0.22 μm (Tianjin Jinteng). The free water-soluble polymer is then filtered out with 500 mL of deionized water to obtain a layer of modified graphene on the surface of the filter membrane. After drying, two electrodes with a distance d of 1 mm and a length L of 5 mm are coated on the surface of the graphene membrane with conductive silver glue. The surface resistance R is measured using a multimeter. s , then the surface resistivity ρ s =R s L / d.

[0125] Example 1

[0126] 100.0 grams of polyvinyl alcohol (PVA) (Sinopec Sichuan Vinylon Plant, brand 1799, degree of polymerization 1700) were dissolved in 1000 mL of deionized water, and then 150 grams of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding wheel speed was set at 100 rpm. After 72 hours of circulation grinding, the graphene suspension processed by the grinding wheel was poured into a beaker and left standstill for 10 hours. The precipitation was then removed by filtration to obtain a stable aqueous dispersion of PVA-grafted graphene, wherein the mass fraction of the grafted graphene was 4.5%. The graphene yield was approximately 30% of the added flake graphite mass. Sample No. 1 in Figure 2 is a stable aqueous dispersion of PVA-grafted graphene left standstill for 15 months, with no precipitation.

[0127] 10 mL of the PVA-grafted graphene aqueous dispersion was added to 200 mL of deionized water for dilution, and then filtered under reduced pressure using a microporous filter membrane with a pore size of 0.22 μm. Finally, 2 L of deionized water was used to filter out free PVA, and the purified PVA-grafted graphene was obtained after drying.

[0128] Figure 3 is a scanning electron microscope photograph of the prepared PVA grafted graphene. The average size of its flakes is about 2.3 microns. From the two-dimensional energy spectrum of carbon and oxygen elements, it can be seen that the oxygen element is mainly near the edge of the graphene sheet, while the carbon element is distributed relatively evenly, indicating that grafting mainly occurs at the edge of the graphene.

[0129] Figure 4 shows the infrared spectra of pure flake graphite, pure PVA and PVA grafted graphene, where the infrared characteristic absorption peaks of PVA and PVA grafted graphene are consistent. The infrared spectra show that at the wave number 3288cm -1 The characteristic absorption peak is the stretching vibration of the -OH bond between or within the grafted PVA molecules in an associated form, with a wave number of 2935 cm -1 and 2904cm -1The characteristic absorption peak is the asymmetric stretching vibration of -CH3 and -CH2- bonds, with a wave number of 1093 cm -1 The characteristic absorption peak is the hydroxyl characteristic absorption peak caused by -CO- stretching vibration, with a wave number of 1142 cm -1 The characteristic absorption peak of the graphite flakes is the characteristic absorption peak of the hydroxyl group caused by the -C-C stretching vibration. This indicates that PVA is grafted onto the graphene. However, the infrared spectrum of the flake graphite shows neither the characteristic absorption peak of PVA nor the characteristic peaks of other active functional groups. This indicates that the surface of the flake graphite does not contain functional groups that can react with PVA. It is believed that during the grinding wheel exfoliation process, the graphite flakes are broken, and the newly generated graphite edges contain many highly active carbon radicals, which react with the PVA in the solution, ultimately obtaining PVA-edge-grafted graphene.

[0130] Figure 5 shows the thermogravimetric analysis curves of pure flake graphite, PVA-grafted graphene, and pure PVA. At 630°C, pure PVA loses nearly 100% of its weight, indicating that PVA has been almost completely decomposed into gas; flake graphite loses almost no weight; PVA edge-grafted graphene loses 14% of its weight at this temperature, indicating that the mass fraction of PVA grafted in the PVA-grafted graphene is 14%; the thermal conductivity of the PVA-grafted graphene is measured to be 276 W / m·K, the surface resistivity is 372Ω, and the Raman spectrum I D / I G The average value is 0.278.

[0131] Example 2

[0132] 100.0 gram polyvinyl alcohol (PVA) (Sinopec Group Sichuan Vinylon Plant, trade mark 1799, degree of polymerization 1700) is dissolved in 1000mL deionized water, then add 150 gram 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.), stir.The grinding disc speed is set at 80rpm, and after 120 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured in the beaker, and after leaving standstill 10 hours, filter and remove precipitation, obtain the stable aqueous dispersion of polyvinyl alcohol grafted graphene, wherein the mass fraction of grafted graphene is 6%.According to the method purifying of embodiment 1, obtain polyvinyl alcohol grafted graphene, its lamella average size is about 2.5 microns, and the PVA mass fraction of grafting is 15.6% in the modified graphene.The graphene productive rate is about 40% of the flake graphite quality added.Among Fig. 2, No. 2 sample is the stable aqueous dispersion of polyvinyl alcohol grafted graphene after leaving standstill 15 months, and has no precipitation. The thermal conductivity of the PVA grafted graphene was measured to be 247W / m·K, the surface resistivity was 678Ω, and the Raman spectrum I D / I G The average value is 0.412.

[0133] Example 3

[0134] 100.0 gram polyvinyl alcohol PVA (Kuraray Co., Ltd., trade mark CP1000) is dissolved in 1000mL deionized water, then add 150 gram 100 order flake graphites (Qingdao Santong Graphite Co., Ltd.), stir.The grinding disc speed is set at 100rpm, and after 100 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured in the beaker, and after leaving standstill 10 hours, filter and remove precipitation, obtain the stable aqueous dispersion liquid of polyvinyl alcohol grafted graphene, wherein the mass fraction of grafted graphene is 4.6%.According to the method purifying of embodiment 1, obtain polyvinyl alcohol grafted graphene, its lamella average size is about 4.8 microns, and in the grafted graphene, the PVA mass fraction is 13.1%.The graphene productive rate is about 31% of the flake graphite quality added.Among Fig. 2, No. 3 samples are the stable aqueous dispersion liquid of polyvinyl alcohol grafted graphene after leaving standstill 15 months, and have no precipitation. The thermal conductivity of the PVA grafted graphene was measured to be 260W / m·K, the surface resistivity was 324Ω, and the Raman spectrum I D / I G The average value is 0.207.

[0135] Example 4

[0136] 200.0 gram polyvinyl alcohol PVA (Kuraray Co., Ltd., trade mark CP1000) are dissolved in 1000mL deionized water, then add 150 gram 100 order flake graphites (Qingdao Santong Graphite Co., Ltd.), stir.The grinding disc speed is set at 100rpm, and after 72 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured in the beaker, and after leaving standstill 10 hours, filter and remove precipitation, obtain the stable aqueous dispersion liquid of PVA grafted graphene, wherein the mass fraction of grafted graphene is 5.3%.According to the method purifying of embodiment 1, obtain PVA grafted graphene, its lamella average size is about 4.2 microns, and in the grafted graphene, the PVA mass fraction is 12.8%.The graphene productive rate is about 35% of the flake graphite quality added.Among Fig. 2, No. 4 sample is the stable aqueous dispersion liquid of the polyvinyl alcohol grafted graphene after leaving standstill 15 months, has no precipitation. The thermal conductivity of the PVA grafted graphene was measured to be 235W / m·K, the surface resistivity was 276Ω, and the Raman spectrum I D / I G The average value is 0.175.

[0137] Example 5

[0138] 80.0 grams of polyvinyl alcohol (PVA) (Sinopec Group Sichuan Vinylon Plant, trade mark 1799, degree of polymerization 1700) are dissolved in 1000mL deionized water, then add 150 grams of 200 order flake graphites (Qingdao Santong Graphite Co., Ltd.), stir.The grinding disc speed is set at 150rpm, and after 48 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured in the beaker, and after leaving standstill 10 hours, filter and remove precipitation, obtain the stable aqueous dispersion of PVA edge grafted graphene, wherein the mass fraction of grafted graphene is 5.4%.According to the method purifying of embodiment 1, obtain polyvinyl alcohol grafted graphene, its lamella average size is about 3.2 microns, and in the grafted graphene, the PVA mass fraction is 9.8%.The graphene productive rate is about 36% of the flake graphite quality added.Among Fig. 2, No. 5 samples are the stable aqueous dispersions of the polyvinyl alcohol grafted graphene after leaving standstill 15 months, and have no precipitation. The thermal conductivity of the PVA grafted graphene was measured to be 289W / m·K, the surface resistivity was 198Ω, and the Raman spectrum I D / I G The average value is 0.102.

[0139] Example 6

[0140] 100.0 grams of polyethylene glycol (Xilong Science Co., Ltd., viscosity-average molecular weight 300,000) are dissolved in 1000mL deionized water, then 150 grams of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) are added, and stirring is carried out. The grinding disc speed is set at 100rpm, and after 72 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured into a beaker, and after standing for 10 hours, filtered and removed for precipitation, and the stable aqueous dispersion of polyethylene glycol-grafted graphene is obtained, wherein the mass fraction of grafted graphene is 4.8%. According to the method purification of embodiment 1, polyethylene glycol-grafted graphene is obtained, and its lamella average size is about 2.7 microns. The grafted modified graphene productive rate is about 32% of the flake graphite quality added. Among Fig. 6, No. 6 samples are the stable aqueous dispersions of polyethylene glycol-grafted graphene after standing for 10 months, and there is no precipitation. Fig. 7 is a scanning electron microscope photo of polyethylene glycol-grafted graphene. Figure 8 shows the thermogravimetric analysis curves of pure flake graphite, PEG-grafted graphene, and pure PEG. At 380°C, pure PEG loses nearly 100% of its weight, indicating complete decomposition into gas. Flake graphite loses almost no weight at all, while PEG-grafted graphene loses 7.8% of its weight at this temperature, indicating a 7.8% PEG-grafted graphene content.

[0141] The thermal conductivity of the polyvinyl alcohol grafted graphene was measured to be 416W / m·K, the surface resistivity was 12.0Ω, and the Raman spectrum I D / I G The average value is 0.095.

[0142] Example 7

[0143] 20.0 grams of sodium polyacrylate (Sinopharm Chemical Reagent Co., Ltd., with a weight-average molecular weight of approximately 450,000) were dissolved in 1000 mL of deionized water, and 150 grams of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding wheel speed was set at 100 rpm. After 72 hours of circulation grinding, the graphene suspension processed by the grinding wheel was poured into a beaker. After standing for 10 hours, the precipitation was removed by filtration to obtain a stable aqueous dispersion of sodium polyacrylate grafted graphene, wherein the mass fraction of the grafted graphene was 3.1%. Purification according to the method of Example 1 obtained sodium polyacrylate grafted graphene, with an average lamella size of approximately 2.8 microns and a sodium polyacrylate mass fraction of 6.9% in the grafted graphene. The graphene yield was approximately 21% of the added graphite mass. Sample No. 7 in Figure 6 is a stable aqueous dispersion of sodium polyacrylate grafted graphene after standing for 10 months, with no precipitation. Figure 9 is a scanning electron microscope photo of sodium polyacrylate grafted graphene.

[0144] The thermal conductivity of the polyacrylate grafted graphene was measured to be 288W / m·K, the surface resistivity was 31.2Ω, and the Raman spectrum I D / I G The average value is 0.127.

[0145] Example 8

[0146] 6.0 grams of xanthan gum (Meihua Biotechnology Group Co., Ltd., MHF-80R) are dissolved in 1000mL deionized water, and then 150 grams of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) are added and stirred. The grinding disc speed is set at 100rpm. After 72 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured into a beaker. After standing for 10 hours, the precipitation is removed by filtration to obtain a stable aqueous dispersion of xanthan gum edge-grafted graphene, wherein the mass fraction of grafted graphene is 2.8%. Purification according to the method of Example 1 obtains xanthan gum grafted graphene, and its lamella average size is about 2.9 microns. The graphene yield is about 20% of the added flake graphite quality. Among Figure 6, No. 8 sample is a stable aqueous dispersion of xanthan gum grafted graphene after preserving for 10 months, and no precipitation is seen. Figure 10 is a scanning electron microscope photo of xanthan gum grafted graphene. Figure 11 shows the thermogravimetric analysis curves of pure flake graphite and xanthan gum-grafted graphene. The flake graphite shows almost no weight loss; the xanthan gum-grafted graphene begins to decompose and lose weight at 280°C, and loses almost no weight at 330°C, with a weight loss of 3.2%, indicating a 3.2% weight content of graphene grafted with xanthan gum. The thermal conductivity of the xanthan gum-grafted graphene was measured to be 257 W / m·K, the surface resistivity was 281Ω, and the Raman spectrum was I D / I G The average value is 0.081.

[0147] Example 9

[0148] 5.0 grams of polyacrylamide (Sinopharm Chemical Reagent Co., Ltd., weight-average molecular weight 1,000,000) were dissolved in 1000 mL of deionized water, and 150 grams of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding wheel speed was set at 100 rpm. After 72 hours of circulation grinding, the graphene suspension processed by the grinding wheel was poured into a beaker. After standing for 10 hours, the precipitate was removed by filtration to obtain a stable aqueous dispersion of polyacrylamide-grafted graphene, wherein the mass fraction of the grafted graphene was 5.25%. Purification according to the method of Example 1 obtained polyacrylamide-grafted graphene, with an average lamella size of approximately 3.1 microns and a mass content of polyacrylamide in the grafted graphene of 2.3%. The graphene yield was approximately 23% of the mass of the added flake graphite. The prepared aqueous dispersion was stably stored for 15 months without precipitation. Figure 12 is a scanning electron microscope photo of polyacrylamide-grafted graphene. The thermal conductivity of the polyacrylamide grafted graphene was measured to be 273W / m·K, the surface resistivity was 279Ω, and the Raman spectrum I D / I G The average value is 0.097.

[0149] Example 10

[0150] 10 grams of hydroxypropyl methylcellulose (Shandong Chuangyao Biotechnology Co., Ltd., CY-50000 (S)) were dissolved in 1000mL of deionized water, and 150 grams of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding wheel speed was set to 100rpm. After 72 hours of circulation grinding, the graphene suspension processed by the grinding wheel was poured into a beaker. After standing for 10 hours, the precipitation was filtered to obtain a stable aqueous dispersion of hydroxypropyl methylcellulose grafted graphene, wherein the mass fraction of the grafted graphene was 3.75%. Purified according to the method of Example 1, hydroxypropyl methylcellulose grafted graphene was obtained, and its average sheet size was about 2.8 microns. The mass content of hydroxypropyl methylcellulose in the grafted graphene was 3.1%. The graphene yield was about 25% of the mass of the added flake graphite. The prepared aqueous dispersion can be stably stored for 15 months without precipitation. Figure 13 is a scanning electron microscope photo of hydroxypropyl methylcellulose grafted graphene. The thermal conductivity of the hydroxypropyl methylcellulose grafted graphene was measured to be 181W / m·K, the surface resistivity was 176Ω, and the Raman spectrum I D / I G The average value is 0.108.

[0151] Example 11

[0152] 150 grams of maleic anhydride isobutylene copolymers (Kuraray Co., Ltd., trade mark ISOBAM-18, number-average molecular weight 300,000-350,000) and 100g of sodium carbonate (Sinopharm Chemical Reagent Co., Ltd., analytically pure) are dissolved in 1000mL deionized water, then 150 grams of 100 mesh flake graphites (Qingdao Santong Graphite Co., Ltd.) are added, and stirring is carried out. The grinding disc speed is set at 100rpm, and after 72 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured into a beaker, and after standing for 10 hours, filtered and removed for precipitation, and a stable aqueous dispersion of sodium maleate isobutylene copolymer grafted graphene is obtained, wherein the mass fraction of grafted graphene is 4.7%. Purified according to the method for Example 1, sodium maleate isobutylene copolymer grafted graphene is obtained, and its lamella average size is about 2.7 microns, and in the grafted graphene, the mass fraction of sodium maleate isobutylene copolymer is 12.8%. The graphene yield is approximately 31% of the mass of the added flake graphite. Figure 14 is a scanning electron micrograph of sodium maleate isobutylene copolymer grafted graphene. The prepared aqueous dispersion can be stored stably for more than 10 months. The thermal conductivity of the sodium maleate isobutylene copolymer grafted graphene was measured to be 143 W / m·K, the surface resistivity was 657Ω, and the Raman spectrum I D / I G The average value is 0.314.

[0153] Example 12

[0154] 150 g of maleic anhydride / vinyl acetate copolymer (Beijing Research Institute of Chemical Industry, preparation method reference: Ru Yue, Discovery of Novel Fluorescent / Phosphorescent Polymers, Luminescence Mechanism and Application Research [D], Beijing University of Chemical Technology, 2015) and 100 g of sodium carbonate (Sinopharm Chemical Reagent Co., Ltd., analytical grade) were dissolved in 1000 mL of deionized water. 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added and stirred thoroughly. The grinding wheel was set at 100 rpm and the milled graphene suspension was poured into a beaker. After standing for 10 hours, the precipitate was removed by filtration to obtain a stable aqueous dispersion of sodium maleate / vinyl acetate copolymer grafted with graphene, with a mass fraction of grafted graphene of 2.7%. Purification according to the method of Example 1 yielded sodium maleate / vinyl acetate copolymer grafted graphene, the average flake size of which 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 was stable for more than 10 months. The thermal conductivity of the sodium maleate / vinyl acetate copolymer grafted graphene was measured to be 283 W / m·K, the surface resistivity was 357 Ω, and the Raman spectrum was 1. D / I G The average value is 0.154.

[0155] Example 13

[0156] In 1000 grams of a 40% aqueous solution of polyethyleneimine (Guohua reagent, weight-average molecular weight 70,000), 100 grams of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred evenly. The grinding wheel speed was set to 100 rpm. After 72 hours of circulating grinding, the graphene suspension processed by the grinding wheel was poured into a beaker. After standing for 10 hours, the precipitate was filtered to obtain a stable aqueous dispersion of polyethyleneimine-grafted graphene, wherein the mass fraction of the grafted graphene was 3.5%. Purification according to the method of Example 1 obtained polyethyleneimine-grafted graphene, whose average lamella size was about 2.5 microns, and the mass fraction of polyethyleneimine in the grafted graphene was 15.9%. The graphene yield was about 35% of the mass of the added flake graphite. Figure 15 is a scanning electron microscope photo of polyethyleneimine-grafted graphene. The prepared aqueous dispersion can be stably stored for more than 10 months. The thermal conductivity of the polyethyleneimine grafted graphene was measured to be 126W / m·K, the surface resistivity was 792Ω, and the Raman spectrum I D / I G The average value is 0.291.

[0157] Example 14

[0158] 13.0 g of PVA (Sinopec Sichuan Vinylon Plant, brand 1799, degree of polymerization 1700) was dissolved in 112.0 g of deionized water, and then 5.0 g of the PVA-grafted graphene solution prepared in Example 5 was added and mechanically stirred to prepare a solution containing 2% by mass of PVA-grafted graphene in PVA. The solution was poured into a glass dish and, after evaporation of the water at room temperature and pressure, a film with a thickness of 1.0 mm was obtained, and the surface resistivity was 2.09×10 7 Ω.

[0159] Comparative Example 1

[0160] 150 g of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) was added to 1000 ml of deionized water and stirred evenly. The grinding wheel was set to 100 rpm. After 100 hours of cyclic grinding, the graphene suspension processed by the grinding wheel was poured into a beaker, allowed to stand for 10 hours, and then filtered to remove the precipitate. Only a very small amount of graphene was obtained, less than 0.5% of the mass of the added flake graphite. The graphene suspension was only stable for a few days, after which a significant precipitation was observed, and after a week, almost all of the graphene had precipitated.

[0161] Comparative Example 2

[0162] 100.0 grams of polyvinyl alcohol (PVA) (Sichuan Vinylon Plant of Sinopec Group, trade mark 1799, degree of polymerization 1700) are dissolved in 1000mL deionized water, then 150 grams of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) are added and stirred. The grinding disc speed is set at 8rpm. After 120 hours of circulation grinding, the graphene suspension processed by the grinding disc is poured into a beaker. After standing for 10 hours, the precipitate is removed by filtration to obtain an aqueous dispersion, in which the mass fraction of grafted graphene is 0.13%. Purification according to the method of embodiment 1 obtains Graphene, and its lamella average size is about 0.7 micron, and the PVA mass fraction of grafting is 0.1%. Productive rate is about 1% of the flake graphite quality added. The visible obvious precipitation of the aqueous dispersion after standing for 1 month is measured. Measure its Raman spectrum I D / I G The average value is 0.035.

[0163] Comparative Example 3

[0164] 100.0 grams of polyvinyl alcohol (PVA) (Sichuan Vinylon Plant of Sinopec Group, brand 1799, degree of polymerization 1700) are dissolved in 1000mL deionized water, and then 150 grams of 100-mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) are added and stirred. The grinding wheel speed is set at 80rpm. After 4 hours of circulation grinding, the suspension processed by the grinding wheel is poured into a beaker. After standing for 10 hours, the precipitation is removed by filtration to obtain an aqueous dispersion, in which the mass fraction of grafted graphene is 0.3%. Purification according to the method of Example 1 obtains polyvinyl alcohol grafted graphene, with an average lamella size of about 0.6 micron, and the mass fraction of grafted PVA in the modified graphene is 0.34%. The productive rate is about 2.1% of the mass of the flake graphite added. The aqueous dispersion after standing for 1 month shows obvious precipitation. The thermal conductivity of the product is 27W / m·K, and the Raman spectrum is 1 D / I G The average value is 0.040.

[0165] Comparative Example 4

[0166] The stainless steel balls and 3.0 grams of 100 mesh flake graphites (Qingdao Santong Graphite Co., Ltd.) that 1000.0 grams of diameters are 5.0mm are added to a stainless steel ball mill (pressure-resistant 16.0MPa, volume 500mL). Under normal temperature, the ball mill is charged with carbon dioxide to a pressure of 7.5MPa by a gas filling device. Then, the ball mill is placed on a planetary ball mill (German Fritsch company, model Pulverisette 6) and milled 48 hours at a speed of 400 rev / min. After emptying carbon dioxide in the ball mill, sieve out steel balls with a sieve, obtain the graphite micro-sheet after the ball milling.

[0167] The ball-milled graphite flakes were dispersed in 500 ml of deionized water and stirred for 1 hour. Then, sodium hydroxide solution was added to adjust the pH value of the system to a weak alkaline state. The system was then allowed to stand for 24 hours. After filtering out the thicker graphite flakes that had precipitated, a sodium carboxylate-modified graphene solution was obtained. The sodium carboxylate-modified graphene solution was distilled and dried to obtain 2.4 g of black sodium carboxylate-modified graphene powder with a yield of 80%. The graphene flakes were less than 200 nm in size, and the mass grafting rate of carboxylic acid groups was 21.5%. The surface resistivity of the product was measured to be 4.5 × 10 3 Ω, thermal conductivity is 0.51W / m·K, Raman spectrum I D / I G The average value is 0.635.

[0168] Comparative Example 5

[0169] 9.80 g of PVA (Sinopec Sichuan Vinylon Plant, brand 1799, degree of polymerization 1700) was dissolved in 90.0 g of deionized water, and then 0.2 g of the graphene prepared in Comparative Example 4 was added and mechanically stirred to prepare a solution containing 2% by mass of graphene in PVA. The solution was poured into a glass dish and, after evaporation of the water at room temperature and pressure, a film with a thickness of 1.0 mm was obtained, and its surface resistivity was 8.7×10 9 Ω.

[0170] By comparing Example 1 with Comparative Examples 2 and 3, it can be seen that when the grinding wheel speed is too low or the grinding time is too short, the degree of graphene exfoliation is low, the water-soluble polymer cannot be effectively grafted onto the graphene, and thus a stable aqueous dispersion cannot be formed.

[0171] By comparing Examples 1, 2, and 5 with Comparative Examples 2 and 3, it can be seen that the content of the water-soluble polymer in the grafted graphene needs to reach a certain level in order to form a stable aqueous dispersion.

[0172] Figure 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), (C) carboxyl-modified graphene prepared in Comparative Example 4. Raman spectrum of PVA edge-grafted graphene of the present invention D / I G The average value is 0.102, which is much lower than the Raman spectrum of commercial reduced graphene oxide I D / I G Average value (0.883) and Raman spectrum of carboxyl-modified graphene prepared by ball milling I D / I G The average value (0.635) indicates that the edge-grafted graphene of the present invention is more regular and the graphene lattice is less damaged.

[0173] By comparing Example 14 with Comparative Example 5, it can be seen that the resistivity of the PVA-based composite film containing the PVA edge-grafted graphene of the present invention is about 2 orders of magnitude lower than that of the PVA-based composite film containing the carboxyl-modified graphene prepared by ball milling, indicating significantly better conductivity. This is mainly because (1) the PVA edge-grafted graphene can be stably dispersed in water. After mixing with the PVA aqueous solution, the graphene can be uniformly dispersed in the PVA, which is conducive to forming a conductive network, while the graphene prepared by ball milling is difficult to disperse in the PVA aqueous solution; (2) compared with the ball-milled graphene, the PVA edge-grafted graphene has a more complete internal structure and a larger graphene size, so its conductivity is better.

[0174] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0175] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. An edge-grafted modified graphene, characterized in that: The edge-grafted modified graphene includes graphene and a water-soluble polymer grafted on its edge. Based on the total mass of the edge-grafted modified graphene, the mass content of the grafted water-soluble polymer in the edge-grafted modified graphene is 1-30%, preferably 2-25%.

2. The edge-grafted modified graphene according to claim 1, wherein Raman spectrum of the edge-grafted modified graphene I D / I G The average value is 0.05-0.60, preferably 0.08-0.55, and / or 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, at room temperature and normal pressure.

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

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

5. The edge-grafted modified graphene according to claim 3, wherein: The water-soluble semi-synthetic high molecular 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. The edge-grafted modified graphene according to claim 3, wherein: The water-soluble synthetic high molecular polymer is selected from at least one of the compounds represented by formula I, the compounds represented by formula II, the compounds represented by formula III, the compounds represented by formula IV and salts thereof, the compounds represented by formula V and salts thereof, and the compounds represented by formula VI; In formula I, R1 is H or C1-C4 alkyl; m is an integer ≥ 400; In formula II, n1 is an integer of 1-8; n2 is an integer ≥10; In formula III, R2 is H or C1-C4 alkyl; M is OR3 or amine, R3 is H, alkali metal or NH4; p is an integer ≥500; In formula IV, R4 is a C1-C3 alkyl group or a phenyl group, R5 is H or a methyl group, and a and b are each independently an integer ≥50; In formula V, c and d are each independently an integer ≥ 50; In Formula VI, z is an integer ≥50.

7. The edge-grafted modified graphene according to claim 6, wherein: The compound represented by formula I is polyvinyl alcohol; and / or the compound represented by formula II is polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentylene glycol, polyethylene glycol, polyheptylene glycol or polyoctanediol; and / or the compound represented by 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 represented by 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 the salts thereof are the corresponding sodium, potassium or ammonium salts thereof; and / or the compound represented by formula V is maleic anhydride vinyl acetate copolymer, and the salts thereof are the corresponding sodium, potassium or ammonium salts thereof; and / or the compound represented by formula VI is polyethyleneimine.

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

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 grinding process. Preferably, the grinding conditions include: a rotation speed of 10-300 rpm, preferably 50-200 rpm; and a grinding time of 5-200 hours, preferably 10-150 hours.

10. An aqueous dispersion of edge-grafted modified graphene, characterized in that: The aqueous dispersion comprises water and edge-grafted modified graphene stably dispersed therein, and the edge-grafted modified graphene is the edge-grafted 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 2-40%, preferably 3-30%.

12. The aqueous dispersion according to claim 10 or 11, wherein The aqueous dispersion is stable at room temperature and normal pressure for more than 10 months, preferably more than 15 months.

13. A method for preparing an aqueous dispersion of edge-grafted modified graphene according to any one of claims 10 to 12, comprising the following steps: The water-soluble polymer, water and graphite are uniformly mixed, and after the water-soluble polymer is completely dissolved, the mixture is ground in a grinding wheel kettle. After the grinding is completed, the mixture is allowed to stand and the precipitate is removed to obtain the 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 cryptocrystalline graphite, the artificial graphite is selected from one or more of pyrolytic graphite and highly oriented pyrolytic graphite, and the graphite is preferably flake graphite; the particle size of the graphite is 5-8000 mesh, preferably 35-3000 mesh, more preferably 50-1600 mesh, and more preferably 50-300 mesh.

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

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

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

18. The preparation method according to claim 17, wherein The filtration is carried out by using a microporous filtration membrane under reduced pressure.

19. The preparation method according to claim 17, wherein The filtering also includes: diluting the aqueous dispersion of edge-grafted modified graphene before filtering; and / or, After filtration, free water-soluble polymers were removed by filtration with water.

20. Use 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, thermal conductive composite polymer materials, multi-layer composite barrier film barrier layer materials, adsorption materials, functional coatings, antistatic or conductive fiber materials, and sunlight or microwave absorbing materials.

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