KR101232273B1 - Producing Method of Carbon Nanotube Grafted by Vinyl Polymer - Google Patents

Abstract

The present invention comprises the steps of (a) dispersing a carbon nanotube and a radical initiator in an organic solvent, followed by stirring to prepare a carbon nanotube grafted with a hydroxyl group or an amine group; (b) After dispersing by adding a photoinitiator to a mixture of carbon nanotubes and an organic solvent grafted hydroxyl group or amine group, the semi-pinacol (-CRR'OH) group is grafted by ultraviolet irradiation Preparing carbon nanotubes; And (c) adding a vinyl monomer to the semi-pinacol group-grafted carbon nanotube and an organic solvent mixture to disperse the same, and then applying energy to produce a carbon-nanografted carbon nanotube. It relates to a carbon nanotube manufacturing method grafted vinyl polymer. The carbon nanotubes grafted with the vinyl polymer may reduce the strong van der Waals attraction of the carbon nanotubes, thereby uniformly dispersing the carbon nanotubes in the organic solvent and the polymer.

Description

Producing Method of Carbon Nanotube Grafted by Vinyl Polymer

The present invention relates to a method for producing carbon nanotubes grafted with a vinyl polymer.

Carbon nanotubes (CNT, Carbon Nanotube) is a material in which the carbon atoms are bonded in a hexagonal honeycomb pattern to form a tube, resulting in a large anisotropy and various structures such as single wall, multiwall, and bundle. The diameter of the tube is nanometer (nm = 1 billionth of a meter), which is a material in the nanosphere. Carbon nanotubes have excellent mechanical properties, electrical selectivity, excellent field emission characteristics, and high efficiency hydrogen storage media.

Carbon nanotubes were first invented by Dr. Ijima of the Japan Electric Company (NEC) in 1991, and have attracted considerable attention from the scientific and industrial world as one of the most interesting new materials. In particular, polymer / carbon nanotube nanocomposites have superior mechanical, chemical, thermal, electrical, and optical properties compared to conventional materials, attracting worldwide attention in the development of such ideal materials. Polymer / carbon nanotube nanocomposites are much stronger composites than conventional materials, and have many potential engineering applications, including applications in a variety of advanced IT industries.

The shape of the carbon nanotubes can be obtained by chemical vapor deposition (CVD) growth, for example, using Ni, Co, Fe, or Pd catalysts. Other forms of elongated carbon observed during direct plasma or microwave plasma CVD growth comb at least partially instead of parallel graphite planes aligned along the nanotube axis as in the case of standard carbon nanotubes. Carbon nanofibers having a graphite plate with a pattern structure. In the case of carbon nanotubes synthesized by various methods such as direct current CVD, in order to maintain the excellent physical properties of carbon nanotubes to the maximum, removal of various types of impurities included in the synthesis (purification) and van der Waals forces It is required to optimize the process (dispersion) of removing the physical bonds between the carbon nanotubes that are bonded together. In the case of the former carbon nanotube purification, the removal of residual metallic catalysts such as Ni, Co, Cu, Fe or Pd, and amorphous carbon by acid treatment is a typical method. As a result, the shortening of the length or the oxidation of the surface causes a problem of deteriorating electrical and mechanical properties. In the case of carbon nanotube dispersion, carbon nanotube dispersion using various kinds of surfactants has been attempted, but it is rarely completely dispersed, and the dispersion amount is still small and it is difficult to remove in the case of ionic or covalent dispersion. This results in the loss of important functions by residual surfactants.

There are two major methods of modifying the surface of carbon nanotubes reported so far. One is to improve the dispersibility through physical reforming and to add a surfactant or to modify the surface of carbon nanotubes using polymer, and the other is to oxidize carbon nanotubes using acidic solution such as sulfuric acid or nitric acid. ) And a chemical group such as a carboxylic acid (-COOH) group or a hydroxy (-OH) group on a part of the sidewall, or by chemically combining various substances on the basis of the chemical functional group. The surface properties of the tubes were also modified (Chem. Rev. 2006, 106, 1105-1136).

The physical surface modification method of carbon nanotubes published so far is a reversible surface modification method using a surfactant or a polymer coating, so that the bonding strength between the dispersant and the carbon nanotubes varies depending on the dispersion conditions such as pH, temperature, and time, and thus dispersion stability in solvents. This has the disadvantage of easily changing. In contrast, the chemical surface modification method of carbon nanotubes is an irreversible surface modification method, and unlike physical surface modification methods, since the surface is permanently modified, there can be almost no change in dispersion stability in the solvent due to the stability of the dispersant.

The most important key technologies for producing polymer / carbon nanotube nanocomposites are firstly, uniformly dispersing carbon nanotubes without polymer aggregation in the polymer without impairing the aspect ratio of carbon nanotubes, and secondly, carbon nanotube matrix. It is to always increase the wettability and adhesion by increasing the interpersonal force of the interpolymer interface. In general, carbon nanotubes have a high van der Waals attractive force, and due to their large surface area and aspect ratio, their own agglomeration occurs, and thus the excellent properties of carbon nanotubes are not uniformly transmitted to the matrix.

In order to solve the above problem, Korean Patent No. 10-0893528 discloses a technique of improving dispersibility by attaching a single molecule to the surface of a carbon nanotube using a radical initiator, but does not disclose a polymer grafting method. No

As described above, in order to develop electric, electronic devices or nanocomposites without changing the excellent properties inherent to carbon nanotubes, it is required to develop new reforming and dispersion technologies that minimize chemical and structural defects of carbon nanotubes.

It is an object of the present invention to provide a new modification and dispersion technique that minimizes chemical and structural defects of carbon nanotubes without changing the excellent properties inherent to carbon nanotubes.

The present invention comprises the steps of (a) dispersing a carbon nanotube and a radical initiator in an organic solvent, followed by stirring to prepare a carbon nanotube grafted with a hydroxyl group or an amine group; (b) After dispersing by adding a photoinitiator to a mixture of carbon nanotubes and an organic solvent grafted hydroxyl group or amine group, the semi-pinacol (-CRR'OH) group is grafted by ultraviolet irradiation Preparing carbon nanotubes; And (c) adding a vinyl monomer to the semi-pinacol group-grafted carbon nanotube and an organic solvent mixture to disperse the same, and then applying energy to produce a carbon-nanografted carbon nanotube. It relates to a carbon nanotube manufacturing method grafted vinyl polymer. The carbon nanotubes grafted with the vinyl polymer may reduce the strong van der Waals attraction of the carbon nanotubes, thereby uniformly dispersing the carbon nanotubes in the organic solvent and the polymer.

Carbon nanotubes grafted with vinyl polymers can reduce the strong van der Waals attraction of carbon nanotubes to uniformly disperse carbon nanotubes in organic solvents and polymers.

1 is a schematic process of a manufacturing method of Example 1.
FIG. 2 shows Raman spectroscopy analysis of multi-walled carbon nanotubes and functionalized carbon nanotubes.
3 is a thermogravimetric analysis result of a multi-walled carbon nanotube (a) and a carbon nanotube (b) functionalized with a hydroxy group and a carbon nanotube (c) to which benzophenone, a photoinitiator, is bonded.
4 is an image of a scanning electron microscope (SEM) of multi-walled carbon nanotubes (a) and polystyrene-grafted carbon nanotubes (b) prepared in Example 1. FIG.
5 is a high-resolution transmission electron microscope (HR-TEM) image of the polystyrene-grafted carbon nanotubes prepared in Example 3. FIG.
FIG. 6 shows thermogravimetric analysis results of carbon nanotubes [(a) to (d)] and polystyrene polymers (e) grafted with vinyl styrene prepared in Examples 1 to 4. FIG.
FIG. 7 shows thermogravimetric analysis results of carbon nanotubes [(a) to (c)] grafted with vinyl polymers prepared in Examples 5 to 7. FIG.
8 is a result of dispersing a multi-walled carbon nanotube (a), a carbon nanotube (b) functionalized with a hydroxyl group, and a benzophenone-grafted carbon nanotube (c) in methanol.
9 is a result of dispersing polystyrene-grafted carbon nanotubes in methanol (a) and tetrahydrofuran (THF) (b).

The present invention comprises the steps of (a) dispersing a carbon nanotube and a radical initiator in an organic solvent, followed by stirring to prepare a carbon nanotube grafted with a hydroxyl group or an amine group; (b) After dispersing by adding a photoinitiator to a mixture of carbon nanotubes and an organic solvent grafted hydroxyl group or amine group, the semi-pinacol (-CRR'OH) group is grafted by ultraviolet irradiation Preparing carbon nanotubes; And (c) adding a vinyl monomer to the semi-pinacol group-grafted carbon nanotube and an organic solvent mixture to disperse the same, and then applying energy to produce a carbon-nanografted carbon nanotube. It relates to a carbon nanotube manufacturing method grafted vinyl polymer.

Although not particularly limited as an initiator attached to the radical initiator hydroxyl group or the amine group in the step (a), may be at least one compound selected from the group consisting of halogen compounds, azo compounds and peroxide compounds, 2,2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis {2-methyl-N- [1,1-bis (hydr) in the azo compound Hydroxymethyl) -2-hydroxyethylpropionamide}, or 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide].

In addition, it is preferable to mix 0.5 to 20 parts by weight of the radical initiator and 0.0001 to 10 parts by weight of carbon nanotubes with respect to 100 parts by weight of the organic solvent. If the radical initiator is less than 0.5 parts by weight, there may be a problem that the functionalization efficiency of the carbon nanotubes are lowered. If the radical initiator is more than 20 parts by weight, inefficient productivity and poor solubility of the initiator may occur. In addition, if the carbon nanotubes are less than 0.0001 parts by weight, the amount of carbon nanotubes obtained is insignificant, which may cause a problem in productivity. If the carbon nanotubes are more than 10 parts by weight, the dispersion effect of the carbon nanotubes may be deteriorated. The stirring may be stirred for 3 to 24 hours. Not only the mixing ratio but also the amount of material to be grafted can be adjusted by controlling the stirring time. If the stirring time is less than 3 hours may cause a problem that the functionalization is not made due to insufficient reaction time.

In the step (b), the photoinitiator may be a benzophenone-based or thioxatone derivative compound, and specific examples thereof may include benzophenone, benzyl (1,2 diketone), or isopropyl-thioxone. In addition, the photoinitiator is preferably added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the carbon nanotube and the organic solvent mixture in which the hydroxyl group or the amine group is grafted. When the photoinitiator is added less than 0.1 parts by weight, there may be a problem that the graft efficiency is lowered because the starting efficiency is low, when added in excess of 5 parts by weight benzophenone absorbs light, rather the graft efficiency is lowered and the presence of residual photoinitiator There may be a problem that the amount is large, which interferes with the graft reaction. In addition, the ultraviolet irradiation time is preferably 1 to 30 minutes. If the irradiation time is less than 1 minute may cause a problem that the starting efficiency is lowered, if it exceeds 30 minutes may be a problem that the pinnacol is formed due to the termination of the semi-pinacol between the radical formation difficult. In addition, the semi-pinacol group is preferably a semi-pinacol group including a phenyl group. That is, it is preferable that R and R 'in a semi-pinacol group (-CRR'OH) are a phenyl group.

The photoinitiator, which absorbed ultraviolet rays through the step (b), is excited in a triplet state and preferentially recaptures hydrogen from H-donor and then forms a semi-pinacol group (-CRR'OH) through radical bonding. By introducing a semi-pinacol group to the carbon nanotubes in the step (b), after the addition of energy, the semi-pinacol falls, radicals are generated, and the vinyl monomer is polymerized to the starting point, the graft proceeds.

The vinyl monomer in step (c) is styrene, divinylbenzene, alphamethylstyrene, fluorostyrene, vinylpyridine, acrylonitrile, methacrylonitrile, butyl acrylate, 2-ethylhexyl acrylate, butyl methacryl Rate, 2-ethylhexylethyl methacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1 With 6-hexanediacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate and 1,3-butylene glycol dimethacrylate It may be one or more selected from the group consisting of.

In addition, the amount of the vinyl monomer may be 5 to 20 parts by weight based on 100 parts by weight of the mixed solution. If the amount is less than 5 parts by weight, there may be a problem of low graft efficiency, and if it exceeds 20 parts by weight, there may be a problem that hinders the graft due to the production of homopolymer.

In addition, the method of applying the energy is not particularly limited, but may be a method of applying heat or ultraviolet rays. Grafting with heat is more productive and efficient. Heat can be added by the method of heating up a liquid mixture at 50-100 degreeC.

The energy can be applied for 3 to 24 hours. The amount of the material to be grafted can be adjusted not only by the addition amount but also by controlling the time.

It is also possible to proceed to the next step by purifying the material produced in each step in the production method, it is also possible to skip the purification process. In order to facilitate the reaction, it is preferable to proceed with the next step by purifying the material prepared in each step.

The organic solvent in the production method is not particularly limited, but may be at least one solvent selected from the group consisting of benzene, chloroform, hexane, methanol, cyclohexane, dimethyl sulfoxide (DMSO), and carbon nanotubes prepared for each step. It is also possible to use a separate organic solvent not purified in the previous step.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following examples are merely to illustrate the present invention, but it should be understood that the present invention is not limited thereto.

Example  One

0.1 g of multi-walled carbon nanotubes (Hanhwa Nanotech Co., Ltd.) and 0.05 g of 2,2'-azobis [2-methyl-N (2-hydroxyethyl) propionamide] (VA-086) as a radical initiator were dimethyl sulfoxide. (DMSO, Duksan Co., Ltd.) dissolved in 50 mL, degassed with nitrogen for 30 minutes, sonicated at 70 ° C. for 2 hours (100 W, 42 kHz), and then stirred at 85 ° C. for 24 hours to hydrate. The carbon nanotubes were functionalized with a hydroxy group.

The hydroxy group grafted carbon nanotubes were filtered with a 0.45 μm polytetrafluoroethylene membrane, and the filtered precipitate was washed several times with methanol to remove unreacted initiators, followed by drying in vacuo to remove hydroxy group grafted carbon. Nanotubes were obtained.

0.01 g of the hydroxy group grafted carbon nanotube and 0.05 g of benzophenone were dissolved in 10 mL of benzene and stirred with a photoinitiator. The gas was removed using nitrogen for 30 minutes, sonicated (100 W, 42 kHz) for 2 hours at 70 ° C., and then UV treated for 3 minutes with a 500 W mercury lamp (Ushio UI-501-C). The distance from the UV light source was adjusted to 10 cm, the temperature was reacted at about 25 ℃ to prepare a carbon nanotube grafted with benzophenone.

After the reaction, 1 g of styrene (Junsei Co.) was added and the temperature was raised to 80 ° C. while stirring, followed by maintaining for 3 hours to prepare polystyrene-grafted carbon nanotubes. The polystyrene grafted carbon nanotubes were filtered with a 0.45 μm polytetrafluoroethylene membrane and dried in vacuo to yield 0.015 g of polystyrene grafted carbon nanotubes. 1 shows a brief manufacturing process of Example 1.

On the other hand, in order to confirm that the preparation was made properly, the results were analyzed by analyzing the carbon nanotubes functionalized with hydroxyl groups and no multi-walled carbon nanotubes by Raman spectroscopy. As shown in FIG. 2, it was confirmed that the radical initiator having a hydroxyl group was chemically bonded to the surface of the carbon nanotubes.

In addition, in FIG. 3, the multi-walled carbon nanotubes (a) which have not been treated at all, the carbon nanotubes (b) functionalized with a hydroxyl group, and benzophenone, which is a photoinitiator, are bonded to carbon nanotubes having a photo-initiator of a semi-pinacol group. Thermogravimetric analysis of the tube (c) is shown. As shown in FIG. 3, a radical initiator having a hydroxyl group was successfully bonded to the surface of the carbon nanotubes, and then benzophenone was bonded thereto to increase the decomposition material that the photo initiator was successfully formed on the surface of the carbon nanotubes. It was confirmed from

In addition, FIG. 4 shows a comparison of the scanning electron microscope (SEM) images of the multi-walled carbon nanotubes (a) which are not treated with the polystyrene-grafted carbon nanotubes (b). As shown in Figure 4 it can be seen that the diameter of (b) is larger than that of (a), in the case of (a) agglomeration occurs due to the dispersion is not good, in the case of (b) agglomeration is not relatively severe You can check it.

In addition, Figure 5 shows a high-resolution transmission electron microscope (HR-TEM) image of the prepared polystyrene-grafted carbon nanotubes. The portion indicated by the arrow is a polystyrene layer, it can be confirmed that the thickness is about 4 ~ 5 nm.

Example  2

Prepared in the same manner as in Example 1, but instead of maintaining the carbon nanotube grafted with styrene and benzophenone for 3 hours was maintained for 6 hours.

Example  3

Prepared in the same manner as in Example 1, but instead of maintaining the carbon nanotube grafted with styrene and benzophenone for 3 hours was maintained for 15 hours

Example  4

Prepared in the same manner as in Example 1, but instead of maintaining the carbon nanotube grafted with styrene and benzophenone for 3 hours was maintained for 24 hours

Example  5

Prepared in the same manner as in Example 3, but using a butyl acrylate 1g instead of styrene as a vinyl monomer, a polybutyl acrylate-grafted carbon nanotubes were prepared.

Example  6

Prepared in the same manner as in Example 3, using methyl methacrylate 1g instead of styrene as a vinyl monomer, a polymethyl methacrylate-grafted carbon nanotubes were prepared.

Example  7

Prepared in the same manner as in Example 3, using 1 g of 2-hydroxy ethyl methacrylate instead of styrene as a vinyl monomer, poly hydroxyethyl methacrylate grafted carbon nanotubes were prepared.

Experimental Example  One

The thermogravimetric analysis results of the polystyrene-grafted carbon nanotubes [(a) to (d)] and the polystyrene polymer (e) prepared in Examples 1 to 4 are shown in FIG. 6. As shown in Figure 6, there was no change in weight to 465 ℃, there was a decrease of 32% by weight in the case of Example 1 at 600 ℃, Example 2 37% by weight, Example 3 46% by weight, Example 4 had a reduction of 55% by weight. In the case of carbon nanotubes, the pyrolysis is not performed at 660 ° C. or lower. As shown in FIG. 7, there is a weight loss due to pyrolysis, it can be seen that the polymer is grafted by the weight reduction. That is, as the reaction time increases, the amount of polystyrene grafted into the radical reaction increases.

Finally, the thermogravimetric analysis results of the carbon nanotubes [(a) to (c)] grafted with the vinyl polymer prepared in Examples 5 to 7 are shown in FIG. 7. The thermogravimetric analysis shows that the vinyl-based polymer is grafted by the decrease in weight.

Experimental Example  2

In Example 1, multi-walled carbon nanotubes without any treatment, carbon nanotubes functionalized with hydroxy groups, 5 mg of carbon nanotubes grafted with benzophenone, and 10 mL of methanol were added to a glass jar, followed by stirring. It was left for 2 months. As shown in FIG. 8, the multi-walled carbon nanotubes (a) which were not treated at all were hardly dispersed, but carbon nanotubes (b) and benzophenone-grafted carbon nanotubes (c) functionalized with a hydroxyl group were used. We can see that it is still distributed.

5 mg of each polystyrene-grafted carbon nanotube prepared in Example 1 was dispersed in 10 mL of methanol (a) and tetrahydrofuran (THF) (b), and then allowed to stand at room temperature for 2 months. As shown in FIG. 9, the carbon nanotubes grafted with polystyrene dispersed in methanol were hardly dispersed, but the carbon nanotubes grafted with polystyrene dispersed in tetrahydrofuran were well dispersed. This result is because polystyrene is not well dispersed in methanol, but is well dispersed in tetrahydrofuran, and it was confirmed that polystyrene was well grafted to carbon nanotubes.

Claims (14)

(a) dispersing a carbon nanotube and a radical initiator in an organic solvent, followed by stirring to prepare a carbon nanotube in which a hydroxyl group or an amine group is grafted;
(b) A photoinitiator selected from benzophenone and thioxatone derivative compounds is added and dispersed in a mixture of carbon nanotubes and an organic solvent grafted with a hydroxyl group or an amine group, and then irradiated with ultraviolet light to semi-pinacol (semi- preparing carbon nanotubes grafted with pinacol and -CRR'OH) groups; And
(c) adding a vinyl monomer to the semi-pinacol group-grafted carbon nanotube and an organic solvent mixture and dispersing the same, and then applying energy to prepare a carbon-nanografted carbon nanotube;
Vinyl-based polymer grafted carbon nanotube manufacturing method comprising a.
The method of claim 1, wherein the radical initiator is at least one compound selected from the group consisting of halogen compounds, azo compounds and peroxide compounds.
The compound according to claim 2, wherein the azo compound is 2,2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis {2-methyl-N- [1 , 1-bis (hydroxymethyl) -2-hydroxyethylpropionamide}, or 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] Carbon nanotube manufacturing method grafted polymer.
According to claim 1, wherein the vinyl-based polymer is grafted, characterized in that mixing in a ratio of 0.5 to 20 parts by weight of the radical initiator and 0.0001 to 10 parts by weight of carbon nanotubes with respect to 100 parts by weight of the organic solvent in the step (a) Carbon nanotube manufacturing method.
delete The method of claim 1, wherein the photoinitiator is benzophenone, benzyl (1,2 diketone) or isopropyl-thioxone.
The method of claim 1, wherein in the step (b) with respect to 100 parts by weight of the carbon nanotubes grafted with a vinyl-based polymer, characterized in that the addition of 0.1 to 5 parts by weight of the photoinitiator.
According to claim 1, wherein the ultraviolet irradiation time in the step (b) is a vinyl-based polymer grafted carbon nanotube manufacturing method, characterized in that 1 to 30 minutes.
[Claim 2] The method of claim 1, wherein the semi-pinacol group comprises a phenyl group.
According to claim 1, wherein the vinyl monomer is styrene, divinylbenzene, alphamethylstyrene, fluorostyrene, vinylpyridine, acrylonitrile, methacrylonitrile, butyl acrylate, 2-ethylhexyl acrylate, butyl meta Acrylate, 2-ethylhexylethyl methacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexanediacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate and 1,3-butylene glycol dimethacrylate Vinyl-based polymer grafted carbon nanotube manufacturing method, characterized in that at least one selected from the group consisting of.
The method of claim 1, wherein in the step (c), the vinyl-based polymer grafted carbon nanotube manufacturing method, characterized in that the addition of 5 to 20 parts by weight of the vinyl monomer with respect to 100 parts by weight of the mixed solution.
The method of claim 1, wherein in the step (c) the vinyl-based polymer grafted carbon nanotubes, characterized in that for 3 to 24 hours to apply energy.
According to claim 1, wherein the method of applying the energy in the step (c) is a vinyl-based polymer grafted carbon nanotube manufacturing method, characterized in that the addition of heat.
The method of claim 1, wherein the organic solvent is benzene, chloroform, hexane, methanol, cyclohexane and dimethyl sulfoxide (DMSO) is a vinyl-based polymer grafted carbon nanotubes, characterized in that the solvent is selected from the group Way.

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