Imidazolium ionic liquid functionalized graphene and preparation method thereof

Abstract

The application discloses an imidazole ionic liquid functionalized graphene and a preparation method thereof, and belongs to the technical field of graphene new materials.The method comprises the following steps: firstly, adding a solvent into the imidazole ionic liquid, adding graphene into the mixed solution for ball milling to obtain a product; then, adding the obtained product into an organic solvent, performing centrifugal washing and drying, performing ultrasonic dispersion, and then performing freeze drying to obtain black powder-shaped imidazole ionic liquid functionalized graphene.The main raw material of the application is graphene, the cost is low, the ball milling process can be used for mass industrial production.The imidazole ionic liquid functionalized graphene prepared by the application has good reinforcing and toughening effects, and has potential application value in the fields of resin reinforcing, resin toughening and heat conduction.

Description

Technical Field

[0001] This invention belongs to the field of graphene new material technology, and specifically relates to an imidazole ionic liquid functionalized graphene and its preparation method. Background Technology

[0002] Graphene is a single-layer graphene sheet with a honeycomb structure composed of sp2 hybridization. The first paper on graphene was published in 2004, which for the first time prepared a two-dimensional material that is stable at room temperature, breaking the claim that two-dimensional materials cannot exist stably at room temperature. Its discoverers were awarded the 2010 Nobel Prize in Physics for this achievement. Due to its excellent mechanical and electrical properties, as well as its high light transmittance, graphene, as a new member of the carbon family, has attracted much attention. Many researchers are studying the preparation of large-area single-layer or few-layer graphene; similarly, many researchers are studying the preparation of graphene powder materials. Among these, the redox method is currently the most commonly used method for preparing graphene powder and also the most promising method for large-scale preparation of graphene powder. At the same time, many researchers are studying graphene derivatives and graphene hybrid materials, modifying graphene to better suit the needs of related fields.

[0003] Ionic liquids (ILs) consist of an organic cation and an inorganic or organic anion in their structure, and are typically liquid at room temperature. As a novel type of "green" solvent, ionic liquids possess many unique properties compared to traditional solvents. In the 1970s, ionic liquids attracted the attention of expert Wilkes, who, while attempting to develop better batteries for missiles and space probes, discovered a liquid electrolyte. Today, ionic liquids have been successfully applied in various fields, including solvent extraction, electrochemistry, separation and purification of substances, catalysts, and solvents.

[0004] Patent CN110963487A reports a method for preparing ionic liquid-modified graphene with microwave absorption properties. Although it has excellent microwave absorption properties and dispersibility, the raw material used is graphene, which is expensive and hard to obtain. In addition, the preparation method includes a grinding step, which makes it impossible to achieve mass production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes an imidazole-based ionic liquid functionalized graphene and its preparation method. This method involves ball milling to exfoliate and modify graphene, followed by ultrasonication and freeze-drying to obtain the imidazole-based ionic liquid functionalized graphene. The main raw material used in this invention is graphene, resulting in low cost. The ball milling process allows for large-scale industrial production. The imidazole-based ionic liquid functionalized graphene prepared by this invention exhibits excellent reinforcing and toughening effects, making it a potential application in resin reinforcement, toughening, and thermal conductivity.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing imidazole-based ionic liquid functionalized graphene includes the following steps:

[0008] Step (1): Add solvent to imidazole ionic liquid to obtain a mixture; add graphene to a ball mill jar containing grinding balls, and then add the above mixture to the ball mill jar for ball milling to obtain the product;

[0009] Step (2): Add the product obtained in step (1) to an organic solvent, then centrifuge, wash and dry it. After drying, the product is ultrasonically dispersed and finally dried to obtain black powdered imidazole ionic liquid functionalized graphene.

[0010] The above-mentioned method for preparing imidazole ionic liquid functionalized graphene includes:

[0011] The imidazole ionic liquid mentioned in step (1) is one of 1-methyl-3-butylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-octyl-3-methylimidazolium chloride;

[0012] The solvent mentioned in step (1) is a mixture of one of methanol, ethanol, THF, and DMF with water, wherein the mass concentration of the organic solvent in the mixture is 50%.

[0013] The ratio of imidazole ionic liquid to solvent in step (1) is (1-10)g:50mL;

[0014] The graphene is reduced graphene oxide; the mass ratio of the graphene to the imidazole ionic liquid is 1:(1-10);

[0015] The grinding jar and grinding balls are made of zirconium oxide; the ball-to-material ratio of the grinding balls to the graphene and mixture in the grinding jar is (4-6):1; the grinding time is 3-6 hours, and the grinding speed is 100-200 rpm.

[0016] The organic solvent mentioned in step (2) is one of methanol, ethanol, THF, and DMF; the centrifugation is performed at a speed of at least 10,000 rpm, and the centrifugation is stopped when all the product has gathered at the bottom of the centrifuge tube and the upper layer of the centrifuge tube is a clear liquid;

[0017] The washing and drying process described in step (2) involves washing the product with organic solvent and water alternately 2-3 times, and then drying it in an oven at 60-80℃ for 10-12 hours.

[0018] The ultrasonic dispersion described in step (2) is carried out by placing the sample in water for 5-10 hours, with the ultrasonic temperature not exceeding 30°C; the drying method after ultrasonic dispersion is freeze drying.

[0019] The structure of the ionic liquid functionalized graphene prepared by the above method is as follows:

[0020]

[0021] In the formula, R1 and R2 are each independently selected from methyl, butyl, and octyl;

[0022] The ionic liquid functionalized graphene described above has an imidazole group in the imidazole ionic liquid and a six-membered ring structure in graphene that are both conjugated structures. The two generate π-π stacking interactions, and the ionic liquid is adsorbed on the graphene surface in a non-covalent bond form.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. The method for preparing imidazole ionic liquid functionalized graphene provided by this invention is simple, requires low equipment, and uses readily available raw materials, and can be used for material modification.

[0025] 2. The preparation method provided by this invention is simple, the conditions are easy to control, and the post-processing is convenient.

[0026] 3. The imidazole ionic liquid functionalized graphene prepared by this invention has better subsequent utilization value and can be used to obtain polymers containing graphene.

[0027] 4. The imidazole-based ionic liquid functionalized graphene prepared by this invention is a black solid powder with good reinforcing and toughening effects. The preparation method is simple, the conditions are easy to control, and the post-processing is convenient. This invention aims to synthesize imidazole-based ionic liquid functionalized graphene, enabling it to have potential applications in resin reinforcement, toughening, or other fields. Attached Figure Description

[0028] Figure 1 a- Figure 1 b are scanning electron microscope images of graphene and ionic liquid functionalized graphene in Example 1 of this invention, respectively.

[0029] Figure 2 This is a scanning electron microscope image of the ionic liquid functionalized graphene in Example 3 of the present invention;

[0030] Depend on Figure 1 , Figure 2It can be seen that extending the ball milling time results in smaller functionalized graphene sheets and thinner layers. This is mainly because the graphene sheets break apart due to collisions between the balls during the ball milling process, and extending the ball milling time can help break and exfoliate the modified graphene. Detailed Implementation

[0031] The present invention will now be described in detail with reference to embodiments.

[0032] Example 1

[0033] A method for preparing imidazole ionic liquid functionalized graphene, with specific operational steps:

[0034] Step (1): Add 10g of graphene to the ball mill jar. Disperse 10g of 1-methyl-3-butylimidazolium chloride in 50ml of 50% ethanol aqueous solution and then add it to the ball mill jar. Add 300g of grinding balls to the ball mill jar. After the feeding is completed, install the ball mill jar on a planetary ball mill and ball mill at 150rpm for 3h.

[0035] Step (2): Disperse the ball-milled product in ethanol, then centrifuge, wash twice with ethanol and distilled water alternately, dry the product in an 80℃ oven, disperse the dried product in 100ml of water and sonicate for 6h, then freeze-dry to obtain a black powder, which is an imidazole ionic liquid functionalized graphene.

[0036] Step (3): 1.8g of ionic liquid modified graphene and 180g of ABS resin were melt-mixed at 160℃ and extruded to obtain ionic liquid modified graphene / ABS thermally conductive composite material. Figure 1 a- Figure 1 b are scanning electron microscope images of graphene and ionic liquid functionalized graphene from Example 1, respectively.

[0037] Example 2

[0038] Step (1): Same as in Example 1.

[0039] Step (2): Disperse the ball-milled product in methanol, then centrifuge, wash twice with methanol and distilled water alternately, dry the product in an 80℃ oven, disperse the dried product in 100ml of water and sonicate for 10h, then freeze-dry to obtain a black powder, which is an imidazole ionic liquid functionalized graphene.

[0040] Example 3

[0041] Step (1): Add 10g of graphene to the ball mill jar. After dispersing 1g of 1-octyl-3-methylimidazolium chloride in 50ml of 50% methanol aqueous solution, add it to the ball mill jar. Add 300g of grinding balls to the ball mill jar. After the feeding is completed, install the ball mill jar on a planetary ball mill and ball mill at 150rpm for 6h.

[0042] Step (2): Same as in Example 1.

[0043] Step (3): Same as in Example 1

[0044] Figure 2 This is a scanning electron microscope image of the ionic liquid functionalized graphene in Example 3.

[0045] Example 4

[0046] Step (1): Same as in Example 1.

[0047] Step (2): Disperse the ball-milled product in ethanol, then filter it, wash it twice with ethanol and distilled water alternately, dry the product in an 80℃ oven, disperse the dried product in 100ml of water and sonicate for 8h, then freeze-dry to obtain a black powder, which is an imidazole ionic liquid functionalized graphene.

[0048] Example 5

[0049] Step (1): Same as in Example 1.

[0050] Step (2): Disperse the product after ball milling into methanol, then filter it, wash it twice with methanol and distilled water alternately, dry the product in an 80℃ oven, disperse the dried product in 100ml of water and sonicate for 8h, then freeze dry to obtain a black powder, which is an imidazole ionic liquid functionalized graphene.

[0051] Comparative Example 1

[0052] 1.8g of graphene and 180g of ABS resin were melt-mixed at 160℃ and then extruded to obtain a graphene / ABS thermally conductive composite material.

[0053] Performance tests were conducted on samples from Examples 1, 3, and Comparative Example 1, respectively. Tensile strength was tested according to GB 1040-79 standard, flexural modulus according to GB / T 9341-2008 standard, impact strength according to GB / T 1843-2008 standard, and thermal conductivity according to GB / T 32064-2015. The test results are shown in Table 1.

[0054] Table 1 Performance testing of ionic liquid functionalized graphene / ABS thermally conductive composite materials

[0055] Tensile strength (MPa) Flexural modulus (MPa) <![CDATA[Impact strength (kJ / m 2 )]]> Thermal conductivity (W / m·K) Example 1 42.41 2367.19 18.22 0.2422 Example 3 44.54 2525.87 23.14 0.2658 Comparative Example 1 40.26 2068.13 17.32 0.2108

[0056] The imidazole-based ionic liquid functionalized graphene disclosed in this invention has significant effects on improving the mechanical and thermal conductivity properties of ABS composites. Among them, 1-octyl-3-methylimidazolium chloride-modified graphene, due to its longer ball milling time, has a more fragmented structure and thinner sheets, resulting in better dispersibility and compatibility in ABS resin compared to 1-methyl-3-butylimidazolium chloride-modified graphene. Therefore, 1-octyl-3-methylimidazolium chloride-modified graphene is more advantageous in improving the mechanical and thermal conductivity properties of ABS composites. Furthermore, the octyl segment is longer than the butyl segment, making 1-octyl-3-methylimidazolium chloride-modified graphene more advantageous in improving the impact resistance of ABS composites.

Claims

1. An imidazolium ionic liquid functionalized graphene, characterized in that, In the imidazole ionic liquid functionalized graphene, the imidazole ionic liquid is adsorbed on the surface of the graphene in a non-covalent bond form, and the non-covalent bond is a π-π stacking interaction between the imidazole group of the imidazole ionic liquid and the six-membered ring structure of the graphene, wherein the imidazole group and the six-membered ring structure are both conjugated structures. The imidazole ionic liquid is one of 1-methyl-3-butyl imidazole chloride, 1-butyl-3-methyl imidazole chloride, and 1-octyl-3-methyl imidazole chloride. The imidazole ionic liquid functionalized graphene is used to prepare a composite material by being compounded with a resin.

2. A method of preparing imidazolium ionic liquid functionalized graphene according to claim 1, characterized in that, The method comprises the following steps: Step (1): adding a solvent to the imidazole ionic liquid to obtain a mixed solution, the dosage ratio of the imidazole ionic liquid to the solvent being (1-10) g: 50 mL; adding graphene into a ball mill tank containing grinding balls, the mass ratio of the graphene to the imidazole ionic liquid being 1:(1-10), and then adding the mixed solution into the ball mill tank for ball milling to obtain a product, the material of the ball mill tank and the grinding balls being zirconia, the ball-to-material ratio of the grinding balls to the graphene and the mixed solution in the ball mill tank being (4-6):1, the ball milling time being 3-6 h, and the ball milling rotation speed being 100-200 rpm; Step (2): adding the product obtained in step (1) into an organic solvent, and then performing centrifugation, washing, and drying, and then performing ultrasonic dispersion on the dried product to obtain black powder-shaped imidazole ionic liquid functionalized graphene; when the product is completely gathered at the bottom of a centrifuge tube and the upper layer of the centrifuge tube is a clear liquid, the centrifugation is stopped; the ultrasonic dispersion is performed in water, the dispersion time being 5-10 h, and the ultrasonic temperature being not higher than 30°C; and the drying mode after the ultrasonic dispersion is freeze drying.

3. The method for preparing imidazole-based ionic liquid functionalized graphene according to claim 2, characterized in that, The solvent in step (1) is a mixture of one of methanol, ethanol, THF, and DMF and water, and the mass concentration of the organic solvent in the mixture is 50%.

4. The method for preparing imidazole-based ionic liquid functionalized graphene according to claim 2, characterized in that, The graphene in step (1) is reduced graphene oxide.

5. The method for preparing imidazole-based ionic liquid functionalized graphene according to claim 2, characterized in that, The organic solvent in step (2) is one of methanol, ethanol, THF, and DMF.

6. The method for preparing imidazole-based ionic liquid functionalized graphene according to claim 2, characterized in that, The washing and drying in step (2) are specifically that the product is washed with the organic solvent and water alternately for 2-3 times, and then the product is placed into an oven at 60-80°C for drying for 10-12 h.

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