Degradable graphene dispersant, preparation method and application thereof

Abstract

The present application relates to a kind of degradable graphene dispersant and its preparation method and application.The degradable graphene dispersant is composed of conjugated center and hydrophilic group with graphene by π-π interaction;The conjugated center is selected from benzene, naphthalene, anthracene, phenanthrene, pyrene or thiophene plane conjugated structure;The hydrophilic group is selected from hydroxyl, amino, polyethylene polyamine, polyether, sulfonic acid group or carboxyl;Two parts are connected by imine bond C=N structure.The graphene dispersant provided by the present application is stable in neutral and weak acid or alkali environment, and can be decomposed in strong acid or alkali.The dispersant can disperse graphene well, and can be removed from the surface of graphene by simple acid-base treatment after use, reducing the negative effects caused by dispersant molecular residue.Based on this, high-conductive carbon-based film can be further prepared, and has wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of carbon material dispersants, in particular to a degradable graphene dispersant and a preparation method and application thereof. BACKGROUND

[0002] Graphene (GR) is a carbon allotrope, whose carbon atoms are arranged in a honeycomb lattice by sp 2 hybridization, and is a single-layer two-dimensional planar conjugated structure material. GR has high π electron cloud density, good thermal and electrical conductivity, and mechanical strength. The conjugated structure of the large plane of GR brings many excellent properties, but at the same time, it also makes the sheet layers have strong van der Waals force and π-π interaction, and is easy to stack and agglomerate, resulting in poor dispersion effect and inability to be uniformly doped and compounded with other materials. To solve this problem, the dispersion ability of GR in solvents can be enhanced by chemical grafting modification, but this process will destroy its planar conjugated structure, resulting in a decrease in intrinsic properties. In contrast, the method of non-covalent functionalization can achieve uniform dispersion of GR through intermolecular π-π interaction without changing its electron cloud structure. It can maintain the inherent properties of GR while achieving good doping in composite materials.

[0003] Molecules with surface activity can be adsorbed on the surface of GR through non-covalent interaction, so as to produce electrostatic repulsion and steric hindrance between the sheet layers, thereby achieving the purpose of GR dispersion. Common surfactants, such as sodium dodecyl sulfate (SDS), didecyldiethylammonium bromide (DDAB), and sodium cholate (SC), can be used as graphene dispersants, but they have problems such as insufficient dispersion capacity and large use amount. New dispersants with aromatic conjugated fused ring structure, such as pyrene, perylene, and naphthalene hydrophilic group grafting derivatives, have improved dispersion capacity for graphene, but still have problems such as single function and residue in composite materials after use. Since the presence of dispersant molecules will affect the performance of GR composite materials in terms of electrical conductivity, thermal conductivity, etc., it is of great significance to prepare high-conductive graphene composite films by removing the dispersant through appropriate methods.

[0004] The dispersant adsorbed on the surface of graphene can be partially removed by certain physical means, such as annealing method, vacuum filtration method and spray drying method, etc. However, the efficiency is low, the dispersant cannot be completely removed, and the method is basically not suitable for practical application. At present, there is no effective and practical method. Therefore, starting from another angle, if a graphene dispersant with degradable properties can be designed and synthesized, the dispersant can be removed from the composite film after use by simple acid or alkali treatment, and then a high-conductive graphene composite film is obtained. The method is based on the design and synthesis of the dispersant, which is completely different from the traditional physical means, and provides a new solution to the residual problem of the dispersant in the final composite material, which has important significance for the practical application of GR materials. Using the dispersant, graphene can be efficiently applied to the preparation of high-conductive films, heat-conductive films, graphene-doped nano-catalytic materials, sensing materials and the like, greatly improving the final performance of the materials, and playing an important role in promoting the development of graphene in related fields. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a graphene dispersant which can highly disperse GR in water and be removed by degradation. The dispersant is combined with GR through π-π interaction between aromatic structures, and the central structure and hydrophilic group are connected through C=N double bond, so that good dispersion of graphene in water can be achieved. C=N can be hydrolyzed by acid treatment, so that the dispersant can be decomposed and removed from the composite material system after use.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows: a degradable graphene dispersant composed of a conjugated center combined with graphene through π-π interaction and a hydrophilic group; the conjugated center is selected from benzene, naphthalene, anthracene, phenanthrene, pyrene or thiophene planar conjugated structure; the hydrophilic group is selected from hydroxyl, amino, polyethylene polyamine, polyether, sulfonic acid group or carboxyl; the two parts are connected by imine bond C=N structure.

[0007] Preferably, the degradable graphene dispersant described above, the conjugated center is selected from benzene planar conjugated structure; the hydrophilic group is selected from hydroxyl; the two parts are connected by imine bond C=N structure, forming a degradable graphene dispersant QSiPT, which has the chemical structure formula as shown below:

[0008]

[0009] Preferably, the degradable graphene dispersant described above, the conjugated center is selected from thiophene planar conjugated structure; the hydrophilic group is selected from hydroxyl; the two parts are connected by imine bond C=N structure, forming a degradable graphene dispersant DSiTE, which has the chemical structure formula as shown below:

[0010]

[0011] A preparation method of a degradable graphene dispersant comprises the following steps:

[0012] 1) Dissolve 1,4-benzene dicarboxaldehyde and excess ethylenediamine in a reaction solvent, reflux at 60 DEG C for 12h, remove impurities by rotary evaporation to obtain intermediate I, which is PTED;

[0013] 2) Add PTED and 3-glycidyloxypropyl trimethoxysilane into a reaction solvent, reflux at 60 DEG C for 24h, remove the solvent by rotary evaporation to obtain intermediate II, which is QSiPT dispersant precursor;

[0014] 3) Add a certain amount of QSiPT dispersant precursor into a formic acid solution, hydrolyze at 60 DEG C for 72h, remove impurities by suction filtration to obtain the target product, which is the dispersant QSiPT aqueous solution.

[0015] Preferably, in the preparation method, the molar ratio of 1,4-benzene dicarboxaldehyde: ethylenediamine is 1:10; and the molar ratio of PTED: 3-glycidyloxypropyl trimethoxysilane is 1:4.

[0016] A preparation method of a degradable graphene dispersant comprises the following steps:

[0017] 1) Dissolve thiophene-2-carboxaldehyde and excess ethylenediamine in a reaction solvent, pass nitrogen, reflux at 60 DEG C for 6h, remove impurities by rotary evaporation to obtain intermediate I, which is TPCA;

[0018] 2) Add TPCA and 3-glycidyloxypropyl trimethoxysilane into a reaction solvent, pass nitrogen, reflux at 60 DEG C for 24h, remove the solvent by rotary evaporation to obtain intermediate II, which is DSiTE dispersant precursor;

[0019] 3) Add a certain amount of DSiTE dispersant precursor into a formic acid solution, pass nitrogen, hydrolyze at 60 DEG C for 72h, remove impurities by suction filtration to obtain the target product, which is the dispersant DSiTE aqueous solution.

[0020] Preferably, in the preparation method, the molar ratio of thiophene-2-carboxaldehyde: ethylenediamine is 1:5; and the molar ratio of TPCA: 3-glycidyloxypropyl trimethoxysilane is 1:2.

[0021] Preferably, in the preparation method, the reaction solvent is methanol or ethanol.

[0022] The application provides application of the degradable graphene dispersant in preparation of graphene dispersion, carbon nanotube dispersion and carbon black dispersion.

[0023] The application provides application of the degradable graphene dispersant in preparation of high-conductivity carbon-based film.

[0024] The present application has the following advantages:

[0025] 1. The graphene dispersant provided by the present application has excellent dispersing capacity for GR, and the GR dispersion liquid can remain stable for a long time in a static state.

[0026] 2. The graphene dispersant provided by the present application can be self-crosslinked through the silicon hydroxyl groups at the molecular terminals, and can play a role of structural reinforcement when used in a composite material.

[0027] 3. The graphene dispersant provided by the present application can be removed after use by hydrolyzing the C=N bond in the molecule through acid treatment, and can be used to prepare a high-conductive graphene composite film.

[0028] 4. The graphene dispersant provided by the present application is stable in a neutral or weak acid or alkali environment, and can be decomposed in a strong acid or alkali. The dispersant can well disperse graphene, and can be removed from the surface of graphene after use through simple acid or alkali treatment, reducing the negative effects caused by the residual dispersant molecules. On this basis, a high-conductive carbon-based film can be further prepared, which has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The infrared spectra of PTA, GPTMS, intermediate PTED and dispersant QSiPT precursors in Example 1 of the present application.

[0030] Figure 2 The zeta potential graph of the graphene water dispersion liquid without adding dispersant in Example 3 of the present application. -1 The zeta potential graph of the graphene water dispersion liquid without adding dispersant in Example 3 of the present application.

[0031] Figure 3 The zeta potential graph of the graphene water dispersion liquid without adding dispersant in Example 3 of the present application. -1 The zeta potential graph of the graphene water dispersion liquid without adding dispersant in Example 3 of the present application.

[0032] Figure 4 The zeta potential graph of the graphene water dispersion liquid without adding dispersant in Example 3 of the present application. -1 The particle size distribution graph of the graphene water dispersion liquid after oscillation dilution in Example 3 of the present application.

[0033] Figure 5 The photo of the high-conductive carbon-based film in Example 4 of the present application.

[0034] Figure 6 The resistance value of the blank control group is measured by placing a multimeter probe on the surface of the high-conductive carbon-based film in Example 4 of the present application.

[0035] Figure 7The image of the small light bulb being turned on by replacing the conductive carbon-based film for the wire in the circuit in Embodiment 4 of the present application. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be described more fully below with reference to specific embodiments. The described embodiments are part of, but not all of the embodiments of the present application, and the present application can be implemented in other different forms. The following embodiments do not limit the present application in any way.

[0037] The preparation method of the degradable graphene dispersant (I) with benzene ring as the conjugate center in Embodiment 1 includes the following steps:

[0038] Step 1: Preparation of intermediate I

[0039] In a 100 mL round-bottom flask, 1,4-benzenedimethanol (0.2682 g, 2 mmol) was added, and then 50 mL of anhydrous methanol was added. Excessive ethylenediamine (1.202 g, 20 mmol) was slowly added while stirring. The reaction was refluxed at 60°C for 12 h. After the reaction was stopped and cooled to room temperature, the solvent methanol and excessive ethylenediamine were removed by rotary evaporation at 80°C. The rotary evaporation was performed more than three times to obtain a light yellow powder, which was intermediate I, i.e., PTED.

[0040] The reaction equation is as follows:

[0041]

[0042] Step 2: Preparation of intermediate II

[0043] In a 100 mL round-bottom flask, intermediate PTED (0.2180 g, 1 mmol) obtained in step 1 was added, and then 50 mL of anhydrous methanol was added. 3-glycidyloxypropyltrimethoxysilane (0.9600 g, 4 mmol) was slowly added while stirring. A drying tube filled with anhydrous calcium chloride was placed above the condenser, and the reaction was refluxed at 60°C for 24 h. After the reaction was stopped and cooled to room temperature, it was placed in a rotary evaporator, and the solvent methanol was removed at 45°C to obtain a light yellow viscous liquid, which was intermediate II, i.e., QSiPT dispersant precursor.

[0044] The reaction equation is as follows:

[0045]

[0046] Step 3: Preparation of aqueous dispersant QSiPT solution

[0047] A certain amount of QSiPT dispersant precursor was taken and added to 0.1 mol·L -1hydrolysis at 60 °C for 72 h. A yellow suspension was obtained, which was filtered to remove the impurities and a bright yellow solution, i.e. the aqueous dispersion of QSiPT, was obtained.

[0048] The reaction equation is as follows:

[0049]

[0050] (B) Characterization

[0051] Figure 1 The infrared spectra of the intermediate PTED and the precursor of the dispersant QSiPT prepared in steps 1 and 2 are shown in FIG. 1. Figure 1 As can be seen from FIG. 1, the 1,4-benzene dicarboxaldehyde (PTA) has an absorption peak at 1695 cm -1 , which corresponds to the C=0 bond stretching vibration peak. The characteristic absorption peak disappears in the intermediate PTED and the precursor of the dispersant QSiPT, and a C=N bond characteristic peak at 1635 cm -1 appears, indicating that the amine aldehyde condensation reaction occurs, proving the successful generation of the Schiff base structure. The 3-glycidyloxypropyl trimethoxysilane (GPTMS) has an epoxy absorption peak at 910 cm -1 , which disappears in the precursor of the dispersant QSiPT, and a hydroxyl characteristic peak at 3401 cm -1 appears, indicating that the epoxy group ring-opening reaction occurs, and a Si-O characteristic peak at 1096 cm -1 appears, proving the successful synthesis of the product.

[0052] Example 2 Degradable graphene dispersant with thiophene as the conjugated center

[0053] The preparation method comprises the following steps:

[0054] Step 1: Preparation of intermediate I

[0055] In a 50 mL three-necked flask, thiophene-2-carboxaldehyde (0.2243 g, 2 mmol) was added, and then 20 mL of anhydrous methanol was added, and an excess of ethylenediamine (0.6011 g, 10 mmol) was slowly added while stirring. Nitrogen was introduced for 15 min, and the reaction was refluxed at 60 °C for 6 h. After the reaction was stopped and cooled to room temperature, the solvent methanol and the excess ethylenediamine were removed by rotary evaporation at 80 °C, which was performed for more than three times to obtain a light yellow solid, which was intermediate I, i.e. TPCA.

[0056] The reaction equation is as follows:

[0057]

[0058] Step 2: Preparation of intermediate II

[0059] In a 50 mL round bottom flask, add TPCA (0.2180 g, 2 mmol) obtained in step 1, then add 20 mL of anhydrous methanol, slowly add 3-glycidyloxypropyltrimethoxysilane (0.9600 g, 4 mmol) while stirring. Nitrogen is introduced for 15 min, and the reaction is refluxed at 60°C for 24 h. The reaction is stopped and cooled to room temperature, and it is placed in a rotary evaporator to remove the solvent methanol at 45°C to obtain a yellow viscous liquid, which is intermediate II, i.e. the precursor of the dispersant DSiTE.

[0060] The equation of the reaction is as follows:

[0061]

[0062] Step 3: Preparation of an aqueous solution of the dispersant DSiTE

[0063] A certain amount of the precursor of the dispersant DSiTE is added to 0.1 mol·L -1 of an aqueous formic acid solution. Nitrogen is introduced for 15 min, and hydrolysis is carried out at 60°C for 72 h to obtain a yellow solution, which is an aqueous solution of the dispersant DSiTE.

[0064] The equation of the reaction is as follows:

[0065]

[0066] Application of the degradable graphene dispersant of Example 3

[0067] The aqueous solution of the dispersant QSiPT prepared in Example 1 is taken with a dispersant to GR mass ratio of 1:1, and a certain amount of deionized water and GR powder is added respectively. After shaking, water bath ultrasonic is used for 5 min, and then ice water bath ultrasonic is used by using an ultrasonic cell crusher with a set power of 350 W. Each ultrasonic is stopped for 3 s after 3 s, and graphene aqueous dispersion is obtained after 30 min.

[0068] Referring to Figure 2 , Figure 2 is the zeta potential of the graphene aqueous dispersion without adding the dispersant with a GR concentration of 1 mg·mL -1 , and the potential value is stable around -14.6 mV.

[0069] Referring to Figure 3 , Figure 3 is the zeta potential of the graphene aqueous dispersion after adding QSiPT with a GR concentration of 1 mg·mL -1 , and the potential value is around +6 mV, which is positive compared with the former.

[0070] Referring to Figure 4 , Figure 4 is the zeta potential of the graphene aqueous dispersion without adding the dispersant with a GR concentration of 1 mg·mL -1The particle size distribution of the graphene water dispersion liquid after oscillation and dilution after the addition of QSiPT. Only one single peak appears in the figure, indicating that the GR has been uniformly dispersed in water.

[0071] Preparation and application of high-conductive carbon-based film

[0072] Step 1: Select an organic filter membrane with a diameter of 50 mm and a pore size of 0.2 μm, and add a graphene water dispersion liquid with a GR concentration of 1 mg·mL -1 to the sand core funnel, vacuum filter, and place it in a 60℃ oven for drying for 20 min to obtain a high-conductive carbon-based film.

[0073] Referring to Figure 5 , Figure 5 , the high-conductive carbon-based film.

[0074] Step 2: Select an organic filter membrane with a diameter of 50 mm and a pore size of 0.2 μm, and add a graphene water dispersion liquid with a GR concentration of 1 mg·mL -1 to the sand core funnel, vacuum filter, and place it in a 60℃ oven for drying for 20 min to obtain a high-conductive carbon-based film.

[0075] Referring to Figure 6 , Figure 6 , the high-conductive carbon-based film.

[0076] Referring to Figure 7 , Figure 7 , the high-conductive carbon-based film.

[0077] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. The protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A degradable graphene dispersant, characterized by, The degradable graphene dispersant consists of a conjugated center and a hydrophilic group through π-π interaction with graphene; the conjugated center is selected from a benzene plane conjugated structure; the hydrophilic group is selected from a hydroxyl group; the two parts are connected through an imine bond C=N structure to form a degradable graphene dispersant QSiPT, which has a chemical structure as shown below: ； or the conjugated center is selected from a thiophene plane conjugated structure; the hydrophilic group is selected from a hydroxyl group; the two parts are connected through an imine bond C=N structure to form a degradable graphene dispersant DSiTE, which has a chemical structure as shown below: 。 2. The degradable graphene dispersant of claim 1, wherein, The preparation method of the graphene dispersant QSiPT comprises the following steps: 1) Dissolve 1,4-benzene dicarboxaldehyde and excess ethylenediamine in a reaction solvent, reflux at 60°C for 12h, remove impurities by rotary evaporation, and obtain intermediate I, which is PTED; 2) Add PTED and 3-glycidyloxypropyl trimethoxysilane to a reaction solvent, reflux at 60°C for 24h, remove the solvent by rotary evaporation, and obtain intermediate II, which is a QSiPT dispersant precursor; 3) Add a certain amount of QSiPT dispersant precursor to a formic acid solution, hydrolyze at 60°C for 72h, remove impurities by suction filtration, and obtain the target product, which is a QSiPT aqueous solution.

3. The degradable graphene dispersant of claim 2, wherein, The molar ratio of 1,4-benzene dicarboxaldehyde:ethylenediamine is 1:10; the molar ratio of PTED:3-glycidyloxypropyl trimethoxysilane is 1:

4.

4. The degradable graphene dispersant of claim 1, wherein, The preparation method of the graphene dispersant DSiTE comprises the following steps: 1) Dissolve thiophene-2-carboxaldehyde and excess ethylenediamine in a reaction solvent, pass nitrogen, reflux at 60°C for 6h, remove impurities by rotary evaporation, and obtain intermediate I, which is TPCA; 2) Add TPCA and 3-glycidyloxypropyl trimethoxysilane to a reaction solvent, pass nitrogen, reflux at 60°C for 24h, remove the solvent by rotary evaporation, and obtain intermediate II, which is a DSiTE dispersant precursor; 3) Add a certain amount of DSiTE dispersant precursor to a formic acid solution, pass nitrogen, hydrolyze at 60°C for 72h, remove impurities by suction filtration, and obtain the target product, which is a DSiTE aqueous solution.

5. The degradable graphene dispersant of claim 4, wherein, The molar ratio of thiophene-2-carboxaldehyde:ethylenediamine is 1:5; the molar ratio of TPCA:3-glycidyloxypropyl trimethoxysilane is 1:

2.

6. The degradable graphene dispersant according to claim 3 or 5, wherein, The reaction solvent is methanol or ethanol.

7. The use of a degradable graphene dispersant according to claim 1 in the preparation of graphene dispersion, carbon nanotube dispersion and carbon black dispersion.

8. The use of a degradable graphene dispersant according to claim 1 in the preparation of a high-conductivity carbon-based film.

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