A high polymer-based dispersant, a preparation method thereof and application thereof in preparing a carbon nanotube dispersion

Abstract

A kind of polymer-based dispersant and its preparation method and application in preparing carbon nanotube dispersion liquid.The present application belongs to the field of carbon nanotube dispersion liquid.The present application solves the problems of carbon nanotube self-entanglement, agglomeration and inability to ensure long-term stable and uniform dispersion effect. The polymer-based dispersant of the present application is a polyethylene glycol modified with an aromatic group. Mixing the dispersant, N-methylpyrrolidone, multi-walled carbon nanotubes and alcohol under ultrasonication yields a uniform and stable carbon nanotube dispersion liquid. The carbon nanotube dispersion liquid of the present application ensures that carbon nanotubes do not agglomerate in the solvent, is conducive to the application in the field of polymer materials, and also effectively prolongs the storage time of the carbon nanotube dispersion liquid, which is conducive to industrial production.

Description

Technical Field

[0001] This invention belongs to the field of carbon nanotube dispersions, specifically relating to a polymer-based dispersant, its preparation method, and its application in the preparation of carbon nanotube dispersions. Background Technology

[0002] Carbon nanotubes are one-dimensional nanomaterials composed of carbon atoms arranged into a tubular structure using specific methods. They possess advantages such as light weight, perfect hexagonal structure connection, high electrical conductivity, high thermal conductivity, and chemical stability. In recent years, with the deepening research on carbon nanotubes and nanomaterials, their broad application prospects have been continuously demonstrated, showing extensive application potential in fields such as energy storage, electronic devices, biomedicine, and materials reinforcement.

[0003] Carbon nanotubes can be viewed as graphene sheets rolled up. Based on the number of graphene layers, they can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. Single-walled carbon nanotubes have a chemically inert surface and a relatively simple chemical structure. However, as the number of nanotube wall layers increases, the surface chemical structure of the carbon nanotubes becomes more complex. The chemical structure of the inner carbon atoms is relatively simple, while the chemical composition of the outer carbon atoms is more complex. Moreover, a large amount of amorphous carbon is often deposited on the outer carbon atoms, creating inhomogeneity in both physical and chemical structures. The numerous surface carbon atoms within the carbon nanotubes have different surface microenvironments. Combined with the large aspect ratio of carbon nanotubes, strong intermolecular forces exist between them, resulting in poor surface activity and hydrophobicity. This makes them prone to entanglement and aggregation, making uniform dispersion difficult in practical applications. Therefore, to better facilitate practical applications, it is necessary to prepare stable carbon nanotube dispersions for use.

[0004] Dispersion methods are generally divided into physical dispersion and chemical dispersion. Physical dispersion uses mechanical force to weaken the van der Waals forces between carbon nanotubes, dispersing the aggregated carbon nanotubes in an aqueous solution. It is simple to operate, but the dispersion effect is not ideal. It is generally used in conjunction with chemical dispersion. Chemical dispersion requires the addition of additives such as dispersants, surfactants, and stabilizers to the dispersion. However, the introduction of these additives often causes a certain degree of attenuation of the conductivity of the carbon nanotube dispersion and cannot maintain uniform and stable dispersion for a long time. Therefore, in order to prolong the stability time of the dispersion, some polymers need to be added.

[0005] In chemical dispersion methods, covalent functionalization of carbon nanotubes can effectively enhance their dispersibility and solubility. However, the conjugated structure of carbon nanotubes is also disrupted during functionalization, affecting their electronic properties. Furthermore, the complex preparation steps of chemical dispersion methods limit the application of carbon nanotube dispersions. Currently, commercially available carbon nanotube dispersions use N-methylpyrrolidone as a solvent and polyvinylpyrrolidone as a dispersant, but the dispersion effect is limited, and carbon nanotubes tend to aggregate to some extent with changes in temperature and time, which is detrimental to long-term storage.

[0006] Non-covalent modification can improve the dispersibility of carbon nanotubes without disrupting their molecular structure. π-π interactions are non-covalent interactions that exist in the π-electron cloud system between aromatic rings containing conjugated structures. Introducing π-π interactions can disrupt the aggregation of carbon nanotubes through mutual attraction and repulsion. This interaction leads to mutual attraction and repulsion between the dispersant and carbon nanotubes, effectively preventing the formation of clusters and thus helping them to be uniformly dispersed in the solvent. However, π-π interactions are weak, and simply introducing them has limited dispersing effects. Therefore, a certain amount of polymeric dispersants is needed to help maintain stable dispersion. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of carbon nanotubes' own entanglement, agglomeration, and inability to guarantee stable and uniform dispersion over a long period of time. This invention provides a polymer-based dispersant, its preparation method, and its application in the preparation of carbon nanotube dispersions. By adding the polymer-based dispersant, the π-π interaction is enhanced, which helps carbon nanotubes to be more uniformly and stably dispersed in solvents and preserved for a long time.

[0008] The technical solution of the present invention is as follows:

[0009] One objective of this invention is to provide a polymer-based dispersant for dispersing carbon nanotubes, wherein the dispersant is synthesized by reacting a carboxylic acid derivative with polyethylene glycol.

[0010] Further specifying, the carboxylic acid derivative is synthesized by reacting an aromatic compound that donates π electrons, an aromatic anhydride, and a catalyst.

[0011] Further specifying, the molar ratio of the π-electron-donating aromatic compound, aromatic anhydride, and catalyst is 0.05-1:0.1-3:0.001-0.005.

[0012] Further specifying, the π-electron-donating aromatic compounds are 2-aminofluorene, diether fluorene, bisphenol fluorene, 9,9-bis(6-hydroxy-2-naphthol)fluorene, bis(9,9-dimethylfluorene)amine, 2-(fluorenemethoxycarbonyl-amino)ethanol, (9H-fluorene-9-yl)methyl(R)-(2-hydroxy-1-phenylethyl)carbamate, 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene diglycidyl ether, 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene, or 9,9-bis(4-glycidyloxyphenyl)fluorene diacrylate.

[0013] Further specifying, the aromatic anhydride is pyromellitic anhydride, phthalic anhydride, biphenyl dianhydride, or 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

[0014] Further specifying, the catalyst is 1-methylimidazole.

[0015] A second objective of this invention is to provide a method for preparing a polymer-based dispersant for dispersing carbon nanotubes, wherein the method includes:

[0016] Step 1: Under an inert gas atmosphere, an aromatic compound and an aromatic anhydride with a π-electron donation system are dissolved in an organic solvent, a catalyst is added, and the reaction is carried out at high temperature to obtain a carboxylic acid derivative.

[0017] Step 2: Dissolve the carboxylic acid derivative, polyethylene glycol and esterification catalyst in an organic solvent, react at room temperature, and then let the product settle and dry to obtain a dispersant.

[0018] Further specifying, the first step reaction temperature is 65-70℃, and the reaction time is 6-9h.

[0019] Further specifying, the reaction time for the second step is 12-24 hours.

[0020] Further specifying, the mass ratio of the carboxylic acid derivative, polyethylene glycol, and esterification catalyst in the second step is 0.2-10:0.5-2:0.001-0.01.

[0021] Further specifying, the esterification catalysts are dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP).

[0022] A third objective of this invention is to provide an application of the polymer-based dispersant for dispersing carbon nanotubes prepared according to the above method in a carbon nanotube dispersion.

[0023] The fourth objective of this invention is to provide a uniform and stable carbon nanotube dispersion, which is prepared from the above-mentioned polymer-based dispersant for carbon nanotube dispersion, N-methylpyrrolidone, multi-walled carbon nanotubes and alcohol solvents.

[0024] The fifth objective of this invention is to provide a method for preparing the above-mentioned carbon nanotube dispersion, wherein the method includes:

[0025] The carbon nanotubes prepared above were dispersed in N-methylpyrrolidone using a polymer-based dispersant, then multi-walled carbon nanotubes were added and ultrasonically dispersed, and finally an alcohol solvent was added.

[0026] Further, the ultrasound time is specified as 2-6 hours.

[0027] The sixth objective of this invention is to provide an application of the carbon nanotube dispersion prepared above in polymer materials.

[0028] Compared with existing technologies, the advantages of this invention are as follows: Through a two-step esterification reaction, firstly, the aromatic anhydride reacts with the amino, hydroxyl, or epoxy groups on the aromatic compound containing a π-electron-donating system. Then, it undergoes esterification with polyethylene glycol to modify the polyethylene glycol, resulting in an aromatic-modified polyethylene glycol dispersant. This allows the polar polyethylene glycol segments to contain a π-electron-rich system, which, through the insertion of π-π interactions, releases the strong binding forces between carbon nanotubes, achieving dispersion. Simultaneously, the polar groups in the molecular chain interact with the solvent, further stabilizing the dispersion of carbon nanotubes. Specific advantages are as follows:

[0029] (1) The product prepared by the two-step esterification reaction can strengthen the π-π interaction in the molecular chain. The insertion of the π-π interaction can effectively promote the dispersion of carbon nanotubes, greatly reduce the use of other additives, save costs, and is simple to operate.

[0030] (2) The product molecular chain prepared by the present invention can also provide polar groups and polymer segments that play a stabilizing role. These two groups and segments are not only conducive to the uniform and stable dispersion of carbon nanotubes, but also can effectively extend the storage time of carbon nanotube dispersion, avoid the waste caused by repeated preparation, and are more conducive to industrial production.

[0031] (3) The dispersants or solvents involved in this invention are highly volatile and can be easily removed as needed in practical applications, thereby obtaining a uniform, highly conductive carbon nanotube slurry for subsequent use. Furthermore, the product obtained by this invention can be directly dissolved in N-methylpyrrolidone, a benign dispersant for carbon nanotubes, without the need to add other solvents. Attached Figure Description

[0032] Figure 1 This is a diagram of the reaction mechanism involved in this invention.

[0033] Figure 2 The infrared spectra of the raw materials and products of Example 1 of the present invention are shown.

[0034] Figure 3 This shows the dissolution of the polymer-based dispersant obtained in Example 1 of this invention in N-methylpyrrolidone.

[0035] Figure 4 The dispersion of carbon nanotube dispersions in Example 1 and Comparative Example 1 after standing for 7 days is shown. Detailed Implementation

[0036] This invention provides a method for preparing a uniform and stable carbon nanotube dispersion, which is achieved through the following steps:

[0037] (1) First, dissolve 0.05-1.0 mol of the π-electron-donating aromatic compound and 0.1-3 mol of the aromatic anhydride in N,N-dimethylformamide (DMF) solvent, add 0.001-0.005 mol of 1-methylimidazole, and place the reaction at 65-70℃ for 6-9 h. The reaction process requires nitrogen protection. Preferably, the π-electron-donating aromatic compound is 0.5-0.6 mol, and the aromatic anhydride is 0.1-0.25 mol.

[0038] The product obtained from the above reaction was then subjected to rotary evaporation at a temperature of 100-130°C until it became viscous and adhered to the walls of the container. The product was then washed three to five times with ethanol and dried in an oven at 120°C to obtain the intermediate product, i.e., the carboxylic acid derivative.

[0039] (2) First, weigh 0.2-10 parts by weight of the above carboxylic acid derivative, preferably 0.2-1 parts by weight of the above product, add 0.5-2 parts of polyethylene glycol, and add 0.001-0.01 parts of DCC and DMAP as esterification catalysts. Add the above reactants to DMF solvent and stir at room temperature for 12-24 hours.

[0040] Then, the obtained product is added to diethyl ether for precipitation treatment. The precipitated product is washed with water, and then the product is dried in an oven at 120°C to obtain the target product, polymer-based dispersant.

[0041] (3) First, weigh the following raw materials according to the weight parts: 0.1-5 parts of the above polymer-based dispersant are dissolved in 10-30 parts of N-methylpyrrolidone, 0.15-3 parts of multi-walled carbon nanotubes are added, and the mixture is placed in an ultrasonic machine for preliminary dispersion. The ultrasonic time is 2-6 hours.

[0042] Then, add 5-20 parts methanol and 60-80 parts ethanol in batches and continue ultrasonic dispersion, with each dispersion time being 3-5 minutes, and perform the dispersion operation 3-5 times to finally obtain a uniformly dispersed black viscous carbon nanotube dispersion. Store the obtained dispersion in a sealed container.

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0045] Example 1:

[0046] (1) Dissolve 0.5 mol of π-electron-donating aromatic compound 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene and 0.12 mol of aromatic acid anhydride pyromellitic anhydride in 30 ml of DMF solvent, add 0.005 mol of 1-methylimidazole, and place the reaction at 70 °C for 9 h. The reaction process requires nitrogen protection.

[0047] The product obtained from the above reaction was then subjected to rotary evaporation at 100°C until it became viscous and adhered to the walls of the evaporator. The product was washed three times with ethanol and then dried in an oven at 120°C to obtain the intermediate product, i.e., the carboxylic acid derivative.

[0048] (2) Weigh 0.2g of the above carboxylic acid derivative, 2g of polyethylene glycol, and 0.001g of DCC and 0.0001g of DMAP as esterification catalysts, dissolve them in 30ml of DMF solvent, stir at room temperature, and react for 24h.

[0049] The obtained product was then subjected to precipitation treatment in diethyl ether, washed with water, and then dried in an oven at 120°C to obtain the target product, a polymer-based dispersant.

[0050] (3) Weigh the following raw materials according to the following weight parts: 0.5 parts of the above polymer-based dispersant are dissolved in 30 parts of N-methylpyrrolidone, 0.5 parts of multi-walled carbon nanotubes are added, and the mixture is placed in an ultrasonic machine for preliminary dispersion for 2 hours.

[0051] Then prepare 9 parts methanol and 60 parts ethanol, and divide them into three equal batches. Add one batch of methanol and ethanol to the above mixture, and then place it in an ultrasonic cell disruptor for dispersion for 5 minutes. Repeat the operation 3 times to finally obtain a uniformly dispersed black viscous carbon nanotube dispersion. Store the obtained dispersion in a sealed container.

[0052] Example 2:

[0053] (1) Dissolve 0.5 mol of π-electron-donating aromatic compound 9,9-bis[(4-hydroxyethoxy)phenyl]fluorene and 0.12 mol of aromatic acid anhydride pyromellitic anhydride in 30 ml of DMF solvent, add 0.005 mol of 1-methylimidazole, and place the reaction at 70 °C for 9 h. The reaction process requires nitrogen protection.

[0054] The product obtained from the above reaction was then subjected to rotary evaporation at 100°C until it became viscous and adhered to the walls of the evaporator. The product was washed three times with ethanol and then dried in an oven at 120°C to obtain the intermediate product, i.e., the carboxylic acid derivative.

[0055] (2) Weigh 0.2g of the above carboxylic acid derivative, 1g of polyethylene glycol, and 0.001g of esterification reaction catalyst DCC and 0.0001g of DMAP, dissolve them in 30ml of DMF solvent, stir at room temperature, and the reaction time is 24h.

[0056] The obtained product was then subjected to precipitation treatment in diethyl ether, washed with water, and then dried in an oven at 120°C to obtain the target product, a polymer-based dispersant.

[0057] (3) Weigh the following raw materials according to the following weight parts: 0.5 parts of the above polymer-based dispersant are dissolved in 30 parts of N-methylpyrrolidone, 0.5 parts of multi-walled carbon nanotubes are added, and the mixture is placed in an ultrasonic machine for preliminary dispersion for 2 hours.

[0058] Then prepare 9 parts methanol and 60 parts ethanol, and divide them into three equal batches. Add one batch of methanol and ethanol to the above mixture, and then place it in an ultrasonic cell disruptor for dispersion for 5 minutes. Repeat the operation 3 times to finally obtain a uniformly dispersed black viscous carbon nanotube dispersion. Store the obtained dispersion in a sealed container.

[0059] Example 3:

[0060] (1) Dissolve 0.1 mol of π-electron-donating aromatic compound 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene and 0.2 mol of aromatic acid anhydride pyromellitic anhydride in 30 ml of DMF solvent, add 0.005 mol of 1-methylimidazole, and place the reaction at 70 °C for 9 h. The reaction process requires nitrogen protection.

[0061] The product obtained from the above reaction was then subjected to rotary evaporation at 100°C until it became viscous and adhered to the walls of the evaporator. The product was washed three times with ethanol and then dried in an oven at 120°C to obtain the intermediate product, i.e., the carboxylic acid derivative.

[0062] (2) Weigh 0.2g of the above carboxylic acid derivative, 1g of polyethylene glycol, and 0.001g of esterification reaction catalyst DCC and 0.0001g of DMAP, dissolve them in 30ml of DMF solvent, stir at room temperature, and the reaction time is 24h.

[0063] The obtained product was then subjected to precipitation treatment in diethyl ether, washed with water, and then dried in an oven at 120°C to obtain the target product, a polymer-based dispersant.

[0064] (3) Weigh the following raw materials according to the following weight parts: 0.5 parts of the above polymer-based dispersant are dissolved in 30 parts of N-methylpyrrolidone, 0.5 parts of multi-walled carbon nanotubes are added, and the mixture is placed in an ultrasonic machine for preliminary dispersion for 2 hours.

[0065] Then prepare 9 parts methanol and 60 parts ethanol, and divide them into three equal batches. Add one batch of methanol and ethanol to the above mixture, and then place it in an ultrasonic cell disruptor for dispersion for 5 minutes. Repeat the operation 3 times to finally obtain a uniformly dispersed black viscous carbon nanotube dispersion. Store the obtained dispersion in a sealed container.

[0066] Comparative Example 1:

[0067] 1. Weigh 0.5 parts of carbon nanotubes and add 30 parts of N-methylpyrrolidone, 9.5 parts of methanol, and 60 parts of ethanol. Then place the mixture in an ultrasonic machine and sonicate for 2 hours. Seal and store the well dispersed carbon nanotube dispersion.

[0068] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A polymer-based dispersant for dispersing carbon nanotubes, characterized in that, The dispersant is synthesized by reaction of a carboxylic acid derivative and polyethylene glycol; The carboxylic acid derivative is synthesized by reaction of a π-electron system aromatic compound, an aromatic anhydride and a catalyst; The π-electron system aromatic compound is 2-amino fluorene, bisether fluorene, bisphenol fluorene, 9,9-bis(6-hydroxy-2-naphthol) fluorene, bis(9,9-dimethyl fluorene) amine, 2-(fluorenylmethoxycarbonyl-amino) ethanol, (9H-fluoren-9-yl) methyl (R)-(2-hydroxy-1-phenylethyl) carbamate, 9,9-bis[(4-hydroxyethoxy) phenyl] fluorene, 9,9-bis(4-hydroxy-3-methylphenyl) fluorene diglycidyl ether, 9,9-bis[(2,3-epoxypropoxy) phenyl] fluorene or 9,9-bis(4-glycidyloxyphenyl) fluorene dipropenoic acid ester; the aromatic anhydride is pyromellitic anhydride, phthalic anhydride, biphenyl tetracarboxylic dianhydride or 3,3'4,4'-benzophenone tetracarboxylic dianhydride; and the catalyst is 1-methyl imidazole.

2. The dispersant of claim 1, wherein The molar ratio of the π-electron system aromatic compound, the aromatic anhydride and the catalyst is 0.05-1:0.1-3:0.001-0.

005.

3. Process for the preparation of a dispersant as claimed in claim 1 or 2, characterized in that, The method comprises: In the first step, the π-electron system aromatic compound and the aromatic anhydride are dissolved in an organic solvent under inert gas, the catalyst is added, and the reaction is carried out at high temperature to obtain the carboxylic acid derivative; In the second step, the carboxylic acid derivative, the polyethylene glycol and the esterification catalyst are dissolved in an organic solvent, and the reaction is carried out at room temperature, then the product is settled and dried to obtain the dispersant.

4. The method of claim 3, wherein, The reaction temperature in the first step is 65-70℃, and the mass ratio of the carboxylic acid derivative, the polyethylene glycol and the esterification catalyst in the second step is 0.2-10:0.5-2:0.001-0.01, and the esterification catalyst is DCC and DMAP.

5. The dispersant of claim 1 or 2 is applied in carbon nanotube dispersion.

6. A uniform, stable carbon nanotube dispersion, characterized in that, The carbon nanotube dispersion is prepared by the dispersant of claim 1 or 2, N-methyl pyrrolidone, multi-walled carbon nanotube and alcohol solvent.

7. The method for producing a carbon nanotube dispersion liquid according to claim 6, characterized by, The method comprises: The dispersant of claim 1 or 2 is dissolved in N-methyl pyrrolidone, then the multi-walled carbon nanotube is ultrasonically dispersed, and finally the alcohol solvent is added.

8. The carbon nanotube dispersion of claim 6 is applied in preparation of high molecular material.

Images