WO2008114910A1

WO2008114910A1 - Dispersion composite of nanotube for a process for preparing the same

Info

Publication number: WO2008114910A1
Application number: PCT/KR2007/003492
Authority: WO
Inventors: Sang Ouk Kim; Sun Hwa Lee
Original assignee: Korea Advanced Institute Of Science And Technology
Priority date: 2007-03-16
Filing date: 2007-07-19
Publication date: 2008-09-25
Also published as: KR100852386B1

Abstract

The present invention relates to a nanotube-dispersed composite, a process for preparing the same and a nanotube-dispersed composite produced by such process. Said nanotube-dispersed composite comprises nanotubes or nanotubes with functional groups introduced thereto and a polymer having functional groups, and it can solve the problems of aggregation among the nanotubes and the difficulty in the dissolution of the nanotubes in organic solvent or polymer matrix by dispersing the nanotubes using the bonding between the functional groups of the polymer and the functional groups of the nanotubes as being stronger than van der Waals force among the nanotubes.

Description

DISPERSION COMPOSITE OF NANOTUBE FOR A PROCESS FOR PREPARING

THE SAME [Technical Field] The object of the present invention is to provide a nanotube-dispersed composite that can be homogeneously dispersed by forming a functional group on nanotube and inducing an intermolecular bond between said functional group and a functionalized polymer, in order to solve the problems of aggregation due to van der Waals force among nanotubes and disadvantages of conventional crosslinking method.

Furthermore, it is another object of the present invention to provide a process of preparing nanotube-dispersed composite in which functional groups are formed on the nanotube or functional groups of the polymer bind to the nanotube itself.

Still furthermore, it is another object of the present invention to provide a nanotube-dispersed composite in which said nanotube-dispersed composite is homogeneously dispersed.

[Background Art]

The present invention relates to a nanotube-dispersed composite, a process for preparing the same and a nanotube- dispersed composite produced by such process. Nanotube-dispersed composite of the present invention is advantageous in that it can solve the problems of prior art wherein individual tubes are aggregated to each other due to van der Waals force among the nanotubes during a synthetic process which uses nanotubes prepared by arc discharge method or thermal chemical vapor phase deposition method, thus prohibiting the dispersion of the nanotubes in solvent or polymer matrix and the formation of a three-dimensional network structure so that the mechanical strength and electrical property of the nanotube composite are impaired.

At present, arc discharge method and thermal chemical vapor phase deposition method produce carbon nanotubes in the form of bundle due to a strong van der Waals bond at initial state. As such, it has remained difficult to mix thus-obtained nanotubes in an organic solvent or a polymer matrix.

For a method of dispersing nanotubes in a polymer matrix, there are solution process, molten mix process, and in-situ polymerization process, etc.

According to a solution process, a nanotube composite is prepared via three steps including dispersing nanotubes in solvent, mixing the dispersion with polymer and evaporating the solvent to form a composite. During said steps, an ultrasonic treatment with high power is carried out or surfactants are added to aid the dispersion of the nanotubes . However, when an ultrasonic treatment with high power is carried out, surface of the nanotubes becomes damaged and length of the nanotubes becomes shortened. Adding surfactants also has a disadvantage of making it difficult to remove all the impurities, which can cause degradation in quality of nanotube products like film, etc. that are sensitive to transparency of their surface.

Molten mix process has a problem that the melting characteristic is changed during the step of dispersing nanotubes in polymer or the polymer can be degraded under high shear rate. Furthermore, in-situ polymerization process, that is the most widely used method for preparing an epoxy nano- composite and in which nanotubes are dispersed in a resin and the resulting resin is solidified by addition of a solidifying agent, uses a resin with very high viscosity, which can cause many problems during cross-linking step.

[Disclosure of Invention] [Technical Subject] Accordingly, the object of the present invention is to provide a nanotube-dispersed composite that can be homogeneously dispersed by forming a functional group on nanotube and inducing an intermolecular bond between said functional group and a functionalized polymer, in order to solve the problems of aggregation due to van der Waals force among nanotubes and disadvantages of conventional crosslinking method.

[Technical Solution]

The present invention relates to a nanotube-dispersed composite, a process for preparing the same and a nanotube- dispersed composite produced by such process.

Nanotube-dispersed composite according to the present invention comprises nanotubes and a polymer having functional groups. The composite is characterized in that, by inducing an intermolecular bond between nanotubes or nanotubes to which functional groups are introduced and a polymer, a dispersed composite wherein the nanotubes are more homogeneously dispersed can be obtained. Said nanotubes are characterized in that they are selected from a group consisting of carbon nanotube, hetero type nanotube, a metal composite comprising such nanotubes and nanoparticles coated with such nanotubes. Carbon nanotube includes single-wall carbon nanotube and multi-wall carbon nanotube. Metal composite comprising carbon nanotube includes a composite in which a metal substrate is coated with nanotubes and nanotubes comprising metal.

The nanotubes according to the present invention are either carbon nanotubes or carbon nanotubes with functional groups . Such functional groups carried by carbon nanotubes include hydroxyl group, carboxylic acid group, and a group derivatized from carboxylic acid. Functional groups carried by polymer include amine group, hydroxyl group, and carboxylic acid group comprising atoms with high electronegativity that can form a bond with functional groups of carbon nanotubes stronger than van der Waals force among the carbon nanotubes themselves .

The above-described process for preparing nanotube- dispersed composite of the present invention is characterized in that it comprises steps of preparing a polymer solution by adding a polymer having functional groups to a solvent, adding nanotubes or nanotubes having the functional groups to said polymer solution, and then stirring or treating the resulting mixture with ultrasonification.

Moreover, the carbon nanotube-dispersed composite of the present invention includes those prepared using said carbon nanotube-dispersed composite such as a film, bulk type having a three-dimensional shape, and those comprising a substrate that is coated with the nanotube-dispersed composite. Hereinafter, the present invention is described in more detail. The nanotube-dispersed composite according to the present invention comprises carbon nanotubes or carbon nanotubes with functional groups introduced thereto and a polymer having functional groups. The functional groups of said nanotubes are not specifically limited, as long as they are capable of binding to the polymer to produce a carbon nanotube-dispersed composite. However, they are preferably the functional group selected from hydroxyl group, carboxylic acid group, or a group derivatized from carboxylic acid, which can be easily introduced into the carbon nanotubes. Said group derivatized from carboxylic acid is preferably an amine group or an ester group.

The above-described carbon nanotubes to which functional groups are introduced is preferably prepared by subjecting the carbon nanotubes to acid treatment and heat treatment for introducing the functional groups. Said acid treatment is not specifically limited, as long as it is a treatment with aqueous solution of at least one inorganic acid that is selected from sulfuric acid, nitric acid, or hydrochloric acid, A mixture of sulfuric acid and nitric acid can be exemplified and an aqueous solution of inorganic acids in which sulfuric acid and nitric acid are mixed in a weight ratio of 3:1 is preferred. It is a characteristic of the present invention that the carbon nanotubes are added to said aqueous solution of inorganic acid and then an ultrasonic treatment is carried out .

Temperature for an ultrasonic treatment is not specifically limited. However, it is preferred to maintain the temperature between 50 °C and 100 ^°C More preferably, the temperature is maintained between 60 and 70 °C Time duration of the ultrasonic treatment can be appropriately adjusted depending on the type of functional groups being introduced and the concentration of reactants, etc. It is preferably between 5 to 15 hours. More preferably, it is between 8 to 12 hours. When the ultrasonic treatment is carried out for less than 5 hours or at the temperature below 50 ^°Q the resulting carbon nanotubes may not be easily cut. On the other hand, when the ultrasonic treatment is carried out for longer than 15 hours or at the temperature above 100 ^°Q the surface of resulting carbon nanotubes can be damaged or the length of the nanotubes can be shortened.

During the above-described acid treatment step, impurities such as metal catalysts included in carbon nanotubes are removed. In addition, the carbon nanotubes are cut into several hundreds of nanometer to several micrometer size pieces and then functional groups are introduced to each piece of the carbon nanotubes . In the step of preparing the carbon nanotubes to which functional groups that are selected according to the present invention are introduced, it is preferred to carry out the heat treatment after the acid treatment. For the heat treatment, the temperature is preferably between 300 ^°C and 500 ^°C More preferably, the temperature is in the range of between 380 °C and 420 ^°C The heat treatment is carried out for 10 min to 2 hours. More preferably, it is carried out for 35 to 45 min so that residual non-crystalline carbon nanotubes and the aqueous solution of inorganic acid can be removed. When the heat treatment is carried out for less than 10 min or at the temperature below 300 ^°C the effect of removing impurities is negligible. On the other hand, when the heat treatment is carried out for longer than 2 hours or at the temperature above 500 "Q the carbon nanotubes themselves can be burnt out, and therefore lowering yield for purification.

The functional groups of the polymer according to the present invention are characterized in that they are able to induce the bonding to hydrogen atoms or the functional groups of the carbon nanotubes as being stronger than van der Waals force among the nanotubes . It is characterized in that such bonding is a non-covalent bond between hydrogen atoms of the carbon nanotube and the functional groups of the polymer or between two functional groups . The functional group of the polymer can be either a terminal group or a side chain group of the polymer.

The polymer having the above-mentioned functional groups is characterized in that it is at least one selected from a group consisting of polyamide polymer such as Nylon 6 and Nylon 6,6, etc.; polyester polymer such as polyethylene terephthalate, polynaphthalene terephthalate, polylactic acid, and polymalic acid, etc.; polycarbonate polymer such as polyethylene carbonate, etc.; polyacetal polymer,- polymer comprising polyphenylene ether; polymer comprising polyphenylene sulfide; polyurethane polymer; epoxy polymer,- polyoxyalkylene polymer such as polyethylene oxide and polypropylene oxide, etc.; polyolefinic polymer such as high density polyethylene, low density polyethylene, ethylene vinyl acetate copolymer, ethylene-acrylic acid copolymer, polypropylene and cyclic olefin copolymer, etc,- styrene polymer such as polystyrene, styrene-acrylonitrile copolymer, styrene-methacrylic ester copolymer and ABS resin, etc.,- halogen-containing polymer such as vinyl chloride polymer and vinylidene chloride polymer, etc.; acrylate polymer derivatized from (meth) acrylic acid or (meth) acrylic acid ester; vinylacetate-containing polymer, vinylpyrrolidine- containing polymer or polyvinyl alcohols, and it comprises functional groups at terminal or side chain group of the polymer.

The functional groups of the polymer that bind to the functional groups of said carbon nanotubes comprise nitrogen, oxygen, phosphorous, sulphur, selenium, fluorine, chlorine, bromine or iodine having electronegativity higher than that of hydrogen atom of the carbon nanotubes, but are not limited thereto. The polymer having said functional groups comprises at least one polymer that is selected from a group consisting of thermoplastic and thermosetting polymers. Preferred examples include polyethylene and polystyrene. More preferably, it is polystyrene. The functional groups of the polymer comprising said atoms are not specifically limited as long as they can induce a non-covalent bond with the functional groups of the carbon nanotubes. Non- limiting example includes amine group, hydroxyl group, carboxylic acid group, ester group and sulphonic acid group. The functional groups of said polymer are linked to a hydroxyl group (-O-H) included in the functional group of carbon nanotube, in which an atom having electronegativity higher than that of the hydrogen atoms comprised in the functional groups of the polymer is comprised, thus generating an intermolecular bond other than a covalent bond. Strength of such bond is proportional to dipole moment of the functional groups that are introduced into the carbon nanotubes and the number of unpaired electron pairs of the atoms that are included in the functional groups of said polymer. As such, when such atoms correspond to nitrogen, oxygen or fluorine, said bond will be stronger than van der Waals force among the carbon nanotubes. For such reason, functional groups of the polymer preferably comprise nitrogen, oxygen or fluorine. Nitrogen atom having the highest hydrogen bond energy is more preferred. For a functional group comprising nitrogen atom among said functional groups, an amine group can be exemplified.

The polymer having the above-described functional groups is characterized in that it corresponds to the polymer with either chemical formula 1 or chemical formula 2 illustrated below.

[Chemical formula 1]

[Chemical formula 2 ]

(Wherein said chemical formulae,

Ri and R₄ are independently to each other a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, an alkoxy group, a carboxylic acid group, a primary amine, a secondary amine or a tertiary amine,

R₂ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms,

R₃ and R₅ are independently to each other a carboxylic acid group, a primary amine, a secondary amine or a tertiary amine, m is a number between 2 to 4 , and n is a number between 10 to 100,000.)

To mix the carbon nanotubes with functional groups that are introduced thereto according to the present invention and the polymer having functional groups, a solvent is used for the polymer having functional groups . Such solvent is not specifically limited as long as it can solubilize both of the carbon nanotubes and the polymer. An aprotic nonpolar solvent is preferred. An aromatic solvent and a lower hydrocarbon solvent are more preferred. For example, benzene and toluene, etc. can be used.

The process for preparing the carbon nanotube-dispersed composite according to the present invention is characterized in that it comprises the following steps of; a) preparing a polymer solution by adding a polymer having functional groups to a solvent, and b) adding nanotubes or nanotubes having the functional groups to said polymer solution, and then stirring or treating the resulting mixture with ultrasonification.

Said process for preparing the nanotube-dispersed composite according to the present invention is characterized in that, by mixing carbon nanotubes or nanotubes to which the functional groups are introduced and the polymer having functional groups by acid treatment and heat treatment, a non- covalent bond that is stronger than van der Waals force among the carbon nanotubes is formed between hydrogen atoms of the carbon nanotubes or the functional groups of the carbon nanotubes and the functional groups of the polymer.

When said carbon nanotubes or nanotubes to which the functional groups are introduced are admixed with the polymer having the functional groups, stirring or an ultrasonic treatment can be carried out, if desired. Without being specifically limited, such stirring or ultrasonic treatment should not break any polymer chain or impair any surface of the carbon nanotubes . The mixture is preferably stirred for 1 to 20 hours. More preferably, it is stirred for 5 to 10 hours. In case of an ultrasonic treatment, it is favorable to proceed with under the condition of the ultrasonic treatment for acid treatment that can promote the incorporation of the functional groups to the carbon nanotubes. Still, it is better to carry out the ultrasonic treatment for less than 10 hours, not to break any of the polymer chains .

The present invention includes a nanotube composite prepared using a composition of the above-described nanotube- dispersed composite. Such nanotube composite can be prepared as a film by coating the composition of the nanotube-dispersed composite onto a substrate and setting the coated substrate or as a pellet or bulk having a three-dimensional shape by adding a substrate and carrying out a solution process or a melt process .

[Brief Description of Drawings]

Figure 1 shows the experimental results of Examples 1 to 3 and Comparative Example 1 and 2. Figure Ia), Ib) and Ic) indicate the results obtained before stirring, after one hour of stirring, and after 24 hours of stirring, respectively.

Figure 2 shows a scanning electron microscopy image of the carbon nanotube-dispersed composite prepared according to Example 1.

Figure 3 shows a transmission electron microscopy image of the carbon nanotube-dispersed composite prepared according to Example 1.

Figure 4 shows the experimental results of Example 4.

Figure 5 shows the experimental results of Example 5. Figure 6 shows the experimental results of Example 6.

Figure 7 shows the experimental results of Comparative Example 3.

Figure 8 shows an example of the carbon nanotube- dispersed composite film prepared according to Example 7. Specifically, Figure 8a) , 8b) and 8c) indicate the results for polystyrene, carboxylic acid group terminated polystyrene, and amine group terminated polystyrene, respectively.

Figure 9 shows the transmission of the carbon nanotube- dispersed composite film prepared according to Example 7. Figure 10 shows the transmission of the carbon nanotube- dispersed composite film prepared according to Example 8.

Figure 11 is a graph showing Young's modulus of the films according to nanotube-dispersed composite of Examples 9 and 10 and Comparative Example 4. Figure 12 is a graph showing hardness of the films according to nanotube-dispersed composite of Examples 9 and 10 and Comparative Example 4.

Figure 13 shows the results of Examples 11 to 16 and Comparative Example 5. [Best Mode for Carrying out the Invention]

[Preparation Example] Method of preparing carbon nanotubes with functional groups

MuIti-wall carbon nanotubes (MWNTs) that are used in the present invention are the nanotubes produced by Hj in Nanotech Company using arc discharge method. The nanotubes are purified by acid treatment and heat treatment. To an acidic solution in which sulphuric acid and nitric acid are admixed with each other in 3:1 weight ratio carbon nanotubes are added and an ultrasonic treatment is carried out for 10 hours, while maintaining the temperature at 65 ^°C Later, heat treatment is carried out at 400 ^°C for 40 min.

By said acid treatment and heat treatment, the carbon nanotubes are cut into pieces, and carboxylic acid groups are found on the cutting surface and the walls of the carbon nanotubes .

[Example 1] Mixing the carbon nanotubes to which carboxylic acid groups are introduced and amine group terminated polystyrene-benzene mixture solution To the carbon nanotubes to which carboxylic acid groups are introduced according to Preparation Example, water is added. After an ultrasonic treatment, a polymer mixture solution is added thereto. The polymer mixture solution that is used in this example is benzene and amine group terminated polystyrene. Benzene, which is used as a solvent for said polymer mixture solution, is GR grade and purchased from Merk Company. Amine group terminated polystyrene has a weight average molecular weight of 3,000 g/mol and is purchased from Polymer Source, Inc.

For the above-described mixture solution, phase separation occurs resulting that the carbon nanotubes are precipitated at the bottom of water while at the top of water the mixture comprising benzene and the low density amine group terminated polystyrene floats. The mixture is stirred for 24 hours. The progress and the results of this process are given in Figure 1. Specifically, the results correspond to PS-NH₂ experimental tubes shown in Figure Ia) , Ib) and Ic) , which indicate the results obtained before stirring, after one hour of stirring, and after 24 hours of stirring, respectively.

In accordance with stirring, the carboxylic acid group of the carbon nanotubes, which were precipitated at the bottom of the aqueous solution, become to form a hydrogen bond with the amine group of the polystyrene comprised in the benzene layer at the top of water, and therefore migrates into the benzene layer. As a result, as it is shown in PS-NH₂ experimental tube of Figure Ic) , the precipitates at the bottom of the aqueous solution are getting disappeared while the color of benzene at the top water is changed, indicating the migration of the carbon nanotubes.

Figure 2 shows a Scanning Electron Microscopy (SEM) image of the carbon nanotube-dispersed composite prepared according to Example 1. Scanning electron microscope manufactured by HITACHI (S4800) is employed. Before using the carbon nanotube- dispersed composite of Example 1, its surface is brought to contact with acetone for wet-etching. It is found that the carbon nanotubes are dispersed.

Figure 3 shows a Transmission Electron Microscopy (TEM) image of the carbon nanotube-dispersed composite prepared according to Example 1. Transmission electron microscope manufactured by Philips (F20) is employed. A test strip for transmission electron microscopy is prepared using an ultramicrotome of PowerTome X, manufactured by Boeckeler Instruments, Inc. For carrying out the image analysis of transmission electron microscopy, a composite film is molded onto an epoxy resin, the resulting resin is cut into thin slices having 50nm thickness, and the test strips floating on top of water are taken and placed on a copper grid that is coated with carbon. Thus obtained test strips are used for transmission electron microscopy. It is confirmed that the carbon nanotubes are finely cut and dispersed.

[Example 2] Mixing the carbon nanotubes to which carboxylic acid groups are introduced and amine group terminated polystyrene mixture solution-benzene mixture solution, wherein said polystyrene mixture solution is a mixture comprising polystyrene with different weight average molecular weight

Procedures that are the same as those described in Example 1 are carried out, except that the polymer solution of Example 1 is replaced with a blend polymer mixture solution in which benzene (GR grade; Merk Company) is used as a solvent and amine group terminated polystyrene (weight average molecular weight of 3,000 g/mol; Polymer Source, Inc.) and polystyrene (weight average molecular weight of 50,000 g/mol; Polyscience, Inc.) are mixed in 1:9 weight ratio. The results are given in Figure 1. Specifically, the results correspond to PS-NH₂+PS experimental tubes shown in Figure Ia) , Ib) and Ic) , which indicate the results obtained before stirring, after one hour of stirring, and after 24 hours of stirring, respectively.

In accordance with stirring, the carboxylic acid group of the carbon nanotubes, which were precipitated at the bottom of the aqueous solution, become to form a hydrogen bond with the amine group of the polystyrene comprised in the mixture solution of the polystyrene and benzene at the top of water, and therefore migrates into the benzene layer. As a result, as it is shown in PS-NH₂+PS experimental tube of Figure Ic) , the precipitates at the bottom of the aqueous solution decrease while the color of benzene at the top water is changed, indicating the migration of the carbon nanotubes.

[Example 3] Mixing the carbon nanotubes to which carboxylic acids are introduced and carboxylic acid group terminated polystyrene-benzene mixture

Procedures that are the same as those described in Example 1 are carried out, except that the polymer solution of Example 1 is replaced with a polymer mixture solution in which carboxylic acid group terminated polystyrene (PS-COOH; weight average molecular weight of 3,000 g/mol; Polymer Source, Inc.) and benzene (GR grade; Merk Company) as a solvent are admixed with each other. The results are given in Figure 1. Specifically, the results correspond to PS-COOH experimental tubes shown in Figure Ia) , Ib) and Ic) , which indicate the results obtained before stirring, after one hour of stirring, and after 24 hours of stirring, respectively. In accordance with stirring, the carboxylic acid group of the carbon nanotubes, which were precipitated at the bottom of the aqueous solution, becomes to form a hydrogen bond with the carboxylic acid group of the polystyrene comprised in benzene at the top of water. As a result, as it is shown in PS-COOH experimental tube of Figure Ic) , the boundary between the aqueous solution and the benzene mixture solution becomes slightly cloudy, compared to the one shown for the corresponding tube in Figure Ia) .

[Comparative Example 1] Mixing the carbon nanotubes to which carboxylic acid groups are introduced and benzene as a solvent

Procedures that are the same as those described in Example 1 are carried out, except that the polymer mixture solution of Example 1 is not added and only benzene (GR grade,-

Merk Company) is used as a solvent. The results are given in

Figure 1. Specifically, the results correspond to benzene experimental tubes shown in Figure Ia) , Ib) and Ic) , which indicate the results obtained before stirring, after one hour of stirring, and after 24 hours of stirring, respectively.

The carbon nanotubes as prepared in the above-described Preparation Example are added to water and an ultrasonic treatment is carried out for the resulting mixture. After that, benzene (GR grade; Merk Company) is added to the mixture and stirred for 24 hours. The results are given in Figure 1. Specifically, the results correspond to benzene experimental tubes shown in Figure Ia) , Ib) and Ic) , which indicate the results obtained before stirring, after one hour of stirring, and after 24 hours of stirring, respectively.

Figure 1 indicates that compared to the benzene experimental tube shown in Figure Ia) the benzene experimental tube shown in Figure Ic) did not show any difference inside the tube.

[Comparative Example 2] Mixing the carbon nanotubes to which carboxylic acid groups are introduced and the polystyrene- benzene mixture solution

Procedures that are the same as those described in Example 1 are carried out, except that the polymer mixture solution of Example 1 is replaced with a polymer mixture solution in which polystyrene having no terminal functional group (PS: weight average molecular weight 3,000g/mol, Polymer Source, Inc.) and benzene (GR grade; Merk Company) as a solvent are admixed with each other. The results are given in Figure 1. Specifically, the results correspond to PS experimental tubes shown in Figure Ia) , Ib) and Ic) , which indicate the results obtained before stirring, after one hour of stirring, and after 24 hours of stirring, respectively.

Figure 1 indicates that compared to the PS experimental tube shown in Figure Ia) the PS experimental tube shown in Figure Ic) did not show any difference inside the tube.

[Example 4]

A constant amount of carbon nanotubes to which carboxylic acid groups are introduced (C_MWNT_S; O.lmg) are added to the mixture of amine group terminated polystyrene (weight average molecular weight 3,000g/mol, Polymer Source, Inc.) and benzene

(GR grade; Merk Company) as a solvent. Specifically, the amine group terminated polystyrene is added to benzene to have the polymer concentration of 0.1 wt%, 0.25 wt%, 0.5 wt%, 1 wt%, 2 wt%, and 4 wt%, respectively. Due to said different concentration of the polystyrene, the relative concentration of the carbon nanotubes is also changed; i.e., it is from 0.25 wt% to 10 wt% as summarized in following Table 1. Six experimental tubes as prepared as above are subjected to an ultrasonic treatment for five hours .

[Table 1]

Change in relative concentration of the carboxylic acid group introduced carbon nanotubes in accordance with a different amount of the polymer having functional groups that is dissolved in benzene solution

In spite of the difference in relative concentration of the carbon nanotubes, as it is shown in Figure 4, the bonding between the amine groups of the polystyrene and the carboxylic acid groups of the carbon nanotubes yielded a color change of the benzene solution and a decrease in the amount of the precipitates over the entire concentration range. These results support that the carbon nanotube composite is dispersed in the benzene.

[Example 5]

Carboxylic acid group terminated polystyrene (weight average molecular weight 3,000g/mol, Polymer Source, Inc.) is added to the experimental tubes having the polymer solution with different relative concentration of the carbon nanotubes to which carboxylic acid groups are introduced, as summarized in the above-described Table 1. Then, the experimental tubes are subjected to an ultrasonic treatment for five hours. Figure 5 indicates that even in a relative concentration range of the carbon nanotubes as low as 1%, the carbon nanotubes were dispersed (see experimental tubes of Figure 5) , showing the darkening of the benzene layer that is similar to the results of Example 4 as given in Figure 4. However, for the experimental tube ©of Figure 5, of which the relative concentration of the carbon nanotubes is 2%, precipitation occurred due to a change in the level of bonding between terminal carboxylic acid groups of the polystyrene and the carboxylic acid groups of the carbon nanotubes.

[Example 6]

Amine group terminated polyethylene oxide (weight average molecular weight 2,000g/mol, Scientific Polymer Products Inc.) is added to the experimental tubes having the polymer solution with different relative concentration of the carbon nanotubes to which carboxylic acid groups are introduced, as summarized in the above-described Table 1. Then, the experimental tubes are subjected to an ultrasonic treatment for five hours.

Figure 6 indicates that there are some experimental tubes showing the darkening of the benzene solution, similar to the experimental tubes of Figure 4 to which the amine group terminated polystyrene is added. As such, it is believed that the functional group of polyethylene oxide, i.e., an amine group, binds to the carboxylic acid group of the carbon nanotubes, consequently generating a carbon nanotube-dispersed composite .

[Comparative Example 3]

Polystyrene (weight average molecular weight 3,000g/mol, Polyscience Inc.) is added to the experimental tubes having the polymer solution with different relative concentration of the carbon nanotubes to which carboxylic acid groups are introduced, as summarized in the above-described Table 1. Then, the experimental tubes are subjected to an ultrasonic treatment for five hours. Figure 7 indicates that over the entire concentration range the precipitation remained for the experimental tubes to which the polystyrene was added. Further, color change was not observed. Thus, it is found that the carbon nanotube-dispersed composite was not formed.

[Example 7] Film preparation using carbon nanotube-dispersed composite

The carbon nanotubes to which carboxylic acid groups are introduced in accordance with Preparation Example was added to 2% polystyrene to obtain a nanotube concentration of 10 wt%. Polystyrene (weight average molecular weight 50,000g/mol, Polyscience Inc.), carboxylic acid group terminated polystyrene (weight average molecular weight 50,000g/mol, Polymer Source Inc.), a blend polymer solution in which amine group terminated polystyrene (weight average molecular weight 3,000g/mol, Polymer Source Inc.) and polystyrene (weight average molecular weight 50,000g/mol, Polyscience Inc.) are admixed with each other in weight ratio of 1:9, are mixed and prepared, respectively. Following an ultrasonic treatment for five hours, each of said mixture is spin-coated on top of a glass plate having 2cm x 2cm x 120nm (width x length x thickness) dimensions. The results are depicted in Figure 8. Specifically, Figure 8 (a) corresponds to the film made from the carbon nanotube-dispersed composite comprising polystyrene (PS) , Figure 8 (b) corresponds to the film made from the carbon nanotube-dispersed composite comprising carboxylic acid group terminated polystyrene (PS-COOH), and Figure 8 (c) corresponds to the film made from the carbon nanotube-dispersed composite comprising the polymer blend in which amine group terminated polystyrene and polystyrene are blended in 1:9 ratio (PS- NH₂+PS) . Comparing the surface of each film, it is found that a huge aggregation occurred for (a) , while (b) and (c) show significantly lower aggregation. Especially (c) is more preferred as it shows the most reduced aggregation.

Transmission of each film described above was measured and the results are summarized in Figure 9. Specifically, transmission of each film was measured using a UV/VIS spectrophotometer (SHIMADZU UV-3101PC) within a visible wavelength range of 400nm to 800nm. Polystyrene film (PS) shows the highest transmission while the film comprising polystyrene with amine group (PS-NH₂+PS) has the lowest transmission. These results indicate that, when the nanotubes are poorly dispersed light penetrates into the aggregation of the carbon nanotubes, yielding high transmission. On the other hand, as the dispersion of the nanotubes is being improved, transmission becomes lower.

[Example 8]

The carbon nanotubes to which carboxylic acid groups are introduced in accordance with Preparation Example was added to

2 wt% the polymer solution (PS-NH₂+PS) comprising the amine group terminated polystyrene (PS-NH₂: weight average molecular weight 3,000g/mol, Polymer Source Inc.) and polystyrene

(weight average molecular weight 50,000g/mol, Polyscience Inc.) in mixing ratio of 1:9, to have the nanotube concentration of 0.25 wt%, 0.5 wt%, 1 wt%, 2 wt%, 4 wt% and 10 wt%, relative to the polymer. The resulting mixture is subjected to an ultrasonic treatment for 5 hours. Thus- obtained carbon nanotube-dispersed composite is spin-coated on top of a glass plate having 2cm x 2cm x 120nm (width x length x thickness) dimensions to give a film. Transmission of each prepared film was measured using a UV/VIS spectrophotometer

(SHIMADZU UV-3101PC) within a visible wavelength range of 400nm to 800nm. The results are shown in Figure 10.

The above-described experiment is to determine the dispersion level of the carbon nanotube-dispersed composite based on intermolecular bonding between the amine groups of the polystyrene and the carboxylic acid groups of the carbon nanotubes . As it is shown in Figure 10, films in which the carbon nanotubes having carboxylic acid groups are comprised in concentrations of from 0.25 wt% to 0.5 wt% have almost the same transmission value of between 97% and 98%. However, for the films comprising the carbon nanotubes at a concentration of 1 wt% or higher, the transmission value rapidly decreased and it was just between 73% and 83% for the film comprising 10 wt% of the carbon nanotubes. Thus, it is found that as the dispersion level of the carbon nanotubes is improved the transmission becomes lower. Still, even for the film comprising the carbon nanotubes at a concentration of 10 wt%, good transmission value of at least 70% was observed.

[Example 9]

The carbon nanotubes to which carboxylic acid groups are introduced in accordance with Preparation Example was added to 5 wt% the polymer solution (PS-NH₂+PS) comprising the amine group terminated polystyrene (PS-NH₂: weight average molecular weight 3,000g/mol, Polymer Source Inc.) and polystyrene (PS: weight average molecular weight 50,000g/mol, Polyscience Inc.) in mixing ratio of 1:9, to obtain the nanotube concentration of 0.25 wt%, 0.5 wt%, 1 wt%, 2 wt%, 4 wt% and 10 wt%, relative to the polymer. The resulting mixture is subjected to an ultrasonic treatment for 5 hours. Using a thin film of thus- obtained carbon nanotube-dispersed composite, hardness and Young's modulus were measured for the composite. Specifically, Young's modulus was determined with a nano indenter which measures the force needed to make a small indentation on a thin film.

Said Young's modulus and hardness data are illustrated in Figure 11 and Figure 12, respectively. Figure 11 indicates that Young's modulus for the carbon nanotube-dispersed composite comprising the amine group terminated polystyrene (PS-NH₂) significantly increases until the weight ratio of the carbon nanotubes as prepared in Preparation Example becomes as high as 1 wt%. For the composite with the weight ratio higher than that, rather a gentle increase was observed. Having the highest modulus value at the same concentration, the composite comprising the amine group terminated polystyrene (PS-NH₂) is found to have better mechanical properties compared to others.

Figure 12 indicates that hardness is also better for the composite comprising PS-NH₂. Meanwhile, Figure 12 also suggests that the mechanical properties can be impaired when too much carbon nanotubes are comprised in the composite.

[Example 10]

The carbon nanotubes to which carboxylic acid groups are introduced in accordance with Preparation Example was added to the polymer solution in which the carboxylic acid group terminated polystyrene (PS-COOH: weight average molecular weight 50,000g/mol, Scientific Polymer Products Inc.) is dissolved to 5 wt% concentration, to obtain the nanotube concentration of 0.25 wt%, 0.5 wt%, 1 wt%, 2 wt%, 4 wt% and 10 wt%, relative to the polymer. The resulting mixture is subjected to an ultrasonic treatment for 5 hours. Using a thin film of thus-obtained carbon nanotube-dispersed composite, hardness and Young's modulus were measured for the composite. Specifically, Young's modulus was determined with a nano indenter which measures the force needed to make a small indentation on a thin film. Said Young's modulus and hardness data are illustrated in Figure 11 and Figure 12, respectively. Figure 11 indicates that Young's modulus for the carbon nanotube-dispersed composite comprising the carboxylic acid group terminated polystyrene (PS-COOH) significantly increases until the weight ratio of the carbon nanotubes as prepared in Preparation Example becomes as high as 1 wt%. For the composite with the weight ratio higher than that, rather a gentle increase was observed. At the same concentration, it appears that Young's modulus for PS-COOH is slightly smaller than that for PS-NH₂. Such result indicates a difference in bonding ability among the terminal groups of the polystyrene. That is, compared to an oxygen comprised in the carboxylic acid group, a nitrogen comprised in the amine groups binds more strongly to the functional groups of the nanotubes. Meanwhile, the composite comprising the polystyrene with carboxylic acid groups shows higher modulus then the composite comprising the polystyrene without any terminal groups. This result supports the dispersing effect by the functional groups. Figure 12 indicates that hardness of the composite comprising PS-COOH is higher than that of PS but lower than that of PS-NH₂, and it is generally consistent with the results shown in the Young's modulus graph. Meanwhile, Figure 12 also suggests that the mechanical properties can be impaired when too much carbon nanotubes are comprised in the composite.

[Comparative Example 4]

The carbon nanotubes to which carboxylic acid groups are introduced in accordance with Preparation Example was added to the polymer solution in which the polystyrene (PS: weight average molecular weight 50,000g/mol, Polyscience Inc.) is dissolved to 5 wt% concentration, to obtain the nanotube concentration of 0.25 wt%, 0.5 wt%, 1 wt%, 2 wt%, 4 wt% and 10 wt%, relative to the polymer. The resulting mixture is subjected to an ultrasonic treatment for 5 hours. Using a thin film of thus-obtained carbon nanotube-dispersed composite, hardness and Young's modulus were measured for the composite.

Specifically, Young's modulus was determined with a nano indenter which measures the force needed to make a small indentation on a thin film.

Said Young's modulus and hardness data are illustrated in Figure 11 and Figure 12, respectively. Figure 11 indicates that Young' s modulus for the composite comprising the polystyrene (PS) significantly increases until the weight ratio of the carbon nanotubes as prepared in Preparation Example becomes as high as 1 wt%. For the composite with the weight ratio higher than that, rather a gentle increase was observed and the modulus was smaller than that of PS-NH₂ in Example 9. Especially when the weight ratio of the functionalized carbon nanotubes is 10 wt%, the modulus for PS is only 8 GPa, compared to 13 GPa for PS-NH₂. Meanwhile, Figure 12 indicates that the hardness of the composite comprising polystyrene also significantly increases until the weight ratio of the carbon nanotubes to which carboxylic acid groups are introduced according to Preparation Example becomes as high as 1 wt%. For the composite with the weight ratio higher than that, rather a gentle increase was observed. It is clear that the hardness of the composite film comprising PS only is significantly weaker than that of the composite film comprising either PS-NH₂ or PS-COOH. In addition, Figure 12 suggests that the mechanical properties can be impaired when too much carbon nanotubes are comprised in the composite.

[Example 11] Amine group terminated polystyrene/carbon nanotube-dispersed composite which is dispersed in different kinds of solvent To obtain the mixture solution with total amount of Ig, 0.01 wt% of the amine group terminated polystyrene (PS-NH₂: weight average molecular weight 3,000g/mol, Polymer Source Inc.), 2 wt% of the carbon nanotubes to which carboxylic acid groups are introduced in accordance with Preparation Example, and a solvent were admixed with each other. The solvents used are 1) benzene, 2) butanone, 3) acetone, 4) tetrahydrofuran (THF) and 5) dimethylformamide (DMF) . The resulting mixture was subjected to an ultrasonic treatment for 5 hours. The results are summarized in Figure 13.

This experiment is to determine the solvent effect on the dispersion level of the carbon nanotube-dispersed composite when different kinds of solvent are used for the same polymer. Figure 13 shows that color of the solvent changed for the tubes tested. Because the changed color is similar to that of Figure 4 in which result of Example 4 is shown for the solution comprising the amine group terminated polystyrene and the carbon nanotubes with various relative concentration admixed with each other, it is believed that the carbon nanotube-dispersed composite was dispersed well in the solvent.

[Example 12] Carboxylic acid group terminated polystyrene/carbon nanotube-dispersed composite which is dispersed in different kinds of solvent Experiment was carried out the same as Example 11 except that the polymer of Example 11 was replaced with the carboxylic acid group terminated polystyrene (PS-COOH: weight average molecular weight 3,000g/mol, Poly Source Inc.) . The results are summarized in Figure 13.

This experiment is to determine the solvent effect on the dispersion level of the carbon nanotube-dispersed composite when different kinds of solvent are used for the same polymer. It is found that when tetrahydrofuran was used as a solvent (i.e., solvent 4) in Figure 13) the test tube was different from others in terms of occurrence of the precipitation and color change of the solvent. Because the result is similar to Figure 7 in which result of Comparative Example 3 is shown for the mixture comprising the non-functionalized polystyrene and the carbon nanotubes prepared according to Preparation Example, it is believed that the carbon nanotube-dispersed composite was not formed in this experiment.

[Example 13] Hydroxyl group terminated polymethyl (meth) acrylate/carbon nanotube-dispersed composite which is dispersed in different kinds of solvent

Experiment was carried out the same as Example 11 except that the polymer of Example 11 was replaced with the hydroxyl group terminated polymethyl (meth) acrylate (PMMA-OH: weight average molecular weight 6,000g/mol, Poly Source Inc.) . The results are summarized in Figure 13. This experiment is to determine the solvent effect on the dispersion level of the carbon nanotube-dispersed composite when different kinds of solvent are used for the same polymer. It is found that when benzene or tetrahydrofuran was used as a solvent (i.e., 1) and 4) in Figure 13) the test tubes were different from others in terms of occurrence of the precipitation and color change of the solvent. Because this result is similar to Figure 7 in which result of Comparative Example 3 is shown for the mixture comprising the non- functionalized polystyrene and the carbon nanotubes prepared according to Preparation Example and the tube 4) using tetrahydrofuran as a solvent in the above-described Example 12, it is believed that the carbon nanotube-dispersed composite was not formed in this experiment.

[Example 14] Amine group terminated polyethylene oxide/carbon nanotube-dispersed composite which is dispersed in different kinds of solvent

Experiment was carried out the same as Example 11 except that the polymer of Example 11 was replaced with the amine group terminated polyethylene oxide (PEO-NH₂: weight average molecular weight 2,000g/mol, Scientific Polymer Products Inc.). The results are summarized in Figure 13. This experiment is to determine the solvent effect on the dispersion level of the carbon nanotube-dispersed composite when different kinds of solvent are used for the same polymer. In general, thanks to the bonding between the amine groups of polyethylene oxide and the carboxylic acid groups of the carbon nanotubes, precipitation amount was not significant. However, color change in the test tubes for which benzene and acetone were respectively employed as a solvent (i.e., 1) and 3) in Figure 13) indicates that the dispersion level has dropped.

[Example 15] Amine group terminated nylon/carbon nanotube- dispersed composite which is dispersed in different kinds of solvent

Experiment was carried out the same as Example 11 except that the polymer of Example 11 was replaced with amine group terminated nylon (Nylon-NH₂: Nylon 6, pellet, Tg: 62.5, Tm-. 228.5, Aldrich) . The results are summarized in Figure 13.

This experiment is to determine the solvent effect on the dispersion level of the carbon nanotube-dispersed composite when different kinds of solvent are used for the same polymer. In general, thanks to the bonding between the amine groups of nylon and the carboxylic acid groups of the carbon nanotubes, precipitation amount was not significant. In addition, because the obtained result is similar to that of Figure 4 in which result of Example 4 is shown for the solution comprising the amine group terminated polystyrene and the carbon nanotubes with various relative concentrations admixed with each other, it is believed that the carbon nanotube-dispersed composite was dispersed well in this case.

[Example 16] Amine group terminated polydimethylsiloxane/carbon nanotube-dispersed composite which is dispersed in different kinds of solvent

Experiment was carried out the same as Example 11 except that the polymer of Example 11 was replaced with amine group terminated polydimethylsiloxane (PDMS-NH₂: 2,500 g/mol, Aldrich) . The results are summarized in Figure 13.

This experiment is to determine the solvent effect on the dispersion level of the carbon nanotube-dispersed composite when different kinds of solvent are used for the same polymer. It is found that when benzene was used as a solvent (i.e., solvent 1) Figure 13) the test tube was different from others in terms of occurrence of the precipitation and color change of the solvent. According to the occurrence of precipitation and different color of the solvent, it is believed that the carbon nanotube-dispersed composite was not formed in this experiment .

[Comparative Example 5]

Experiment was carried out the same as Example 11 except that the polymer was not added. The results are summarized in Figure 13.

This experiment is to determine the solvent effect on the dispersion level of the carbon nanotube-dispersed composite when different kinds of solvent are used. It is found that solvent 1) benzene cannot disperse the carbon nanotubes at all, and Figure 13 shows the precipitation of the nanotubes when benzene was used. On the other hand, other solvents including 2) butanone, 3) acetone, 4) tetrahydrofuran (THF) , and 5) dimethylformamide (DMF) can disperse the carbon nanotubes prepared according to Preparation Example. It is supported by the color change of each solvent .

[industrial Applicability]

As it is described in the above, the carbon nanotube- dispersed composite according to the present invention can be effectively used to provide a nanotube composite such as film, etc. having a high electric conductivity and an excellent mechanical property, as the functional groups of a polymer and the nanotubes bind to each other to help homogeneous dispersion of the nanotubes within the polymer.

Claims

[CLAIMS]

[Claim l]

Nanotube-dispersed composite comprising a nanotube and a polymer having functional group.

[Claim 2]

The nanotube-dispersed composite of claim 1, wherein said nanotube is selected from a group consisting of carbon nanotube, hetero type nanotube, metal composite comprising said nanotube and nanoparticle coated with said nanotube.

[Claim 3]

The nanotube-dispersed composite of claim 1, wherein said nanotube comprises a single-wall or multi-wall carbon nanotube.

[Claim 4]

The nanotube-dispersed composite of claim 1, wherein said nanotube is linked with any one functional group selected from hydroxyl group, carboxylic acid group or functional group derivatized from carboxylic acid.

[Claim 5]

The nanotube-dispersed composite of claim 4, wherein said functional group is formed through heat treatment after acid treatment .

[Claim 6]

The nanotube-dispersed composite of claim 5, wherein the acid treatment is carried out in aqueous solution of at least one inorganic acid selected from sulfuric acid, nitric acid or hydrochloric acid.

[Claim 7] The nanotube-dispersed composite of claim 6, wherein said aqueous solution of inorganic acid is treated with ultrasonification at the temperature between 50^°C and 100^°C .

[Claim δj The nanotube-dispersed composite of claim 5, wherein said heat treatment is carried out by heating the carbon nanotube at the temperature between 300^°C and 500^°C for 10 min to 2 hours after acid treatment.

[Claim 9]

The nanotube-dispersed composite of claim 1, wherein said polymer having functional group is at least one polymer selected from thermoplastic or thermosetting polymer. [Claim lθ]

The nanotube-dispersed composite of claim 9, wherein the polymer having functional group is at least one polymer selected from a group consisting of polyamide polymer such as Nylon 6 and Nylon 6,6, etc.; polyester polymer such as polyethylene terephthalate, polynaphthalene terephthalate, polylactic acid, and polymalic acid, etc.; polycarbonate polymer such as polyethylene carbonate, etc.; polyacetal polymer; polymer comprising polyphenylene ether; polymer comprising polyphenylene sulfide; polyurethane polymer; epoxy polymer; polyoxyalkylene polymer such as polyethylene oxide and polypropylene oxide, etc.; polyolefinic polymer such as high density polyethylene, low density polyethylene, ethylene vinyl acetate copolymer, ethylene-acrylic acid copolymer, polypropylene and cyclic olefin copolymer, etc,- styrene polymer such as polystyrene, styrene-acrylonitrile copolymer, styrene-methacrylic ester copolymer and ABS resin, etc.; halogen-containing polymer such as vinyl chloride polymer and vinylidene chloride polymer, etc.; acrylate polymer derivatized from (meth) acrylic acid or (meth) acrylic acid ester; vinylacetate-containing polymer, vinylpyrrolidine- containing polymer or polyvinyl alcohols, and it comprises functional group at terminal or side chain group of the polymer. [Claim ll]

The nanotube-dispersed composite of claim 9, wherein the functional group of polymer is a terminal group or side chain group of the polymer.

[Claim 12]

The nanotube-dispersed composite of claim 11, wherein said functional group of polymer comprises an atom having electronegativity higher than that of the hydrogen of the nanotube or the hydrogen of the functional group of the nanotube .

[Claim 13] The nanotube-dispersed composite of claim 12, wherein said functional group of polymer comprises at least one atom selected from nitrogen, oxygen, phosphorous, sulphur, selenium, fluorine, chlorine, bromine and iodine.

[Claim 14]

The nanotube-dispersed composite of claim 13, wherein said functional group of polymer is at least one group selected from a group consisting of amine group, hydroxy1 group or carboxylic acid group, ester group and sulphonic acid group. [Claim 15]

The nanotube-dispersed composite of claim 13, wherein said polymer having functional group is the polymer with either chemical formula 1 or chemical formula 2 illustrated below.

[Chemical formula 1]

[Chemical formula 2 ]

(Wherein said chemical formula,

R₂ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms ,

R₃ and R₅ are independently to each other a carboxylic acid group, a primary amine, a secondary amine or a tertiary amine, m is a number between 2 to 4, and n is a number between 10 to 100,000.)

[Claim 16]

Process for preparing the nanotube-dispersed composite comprising the following steps of; a) preparing a polymer solution by adding a polymer having functional groups to a solvent, and b) adding nanotubes or nanotubes having the functional groups to said polymer solution, and then stirring or treating the resulting mixture with ultrasonification.

[Claim 17]

The process for preparing the nanotube-dispersed composite of claim 16, wherein said nanotube is selected from a group consisting of carbon nanotube, hetero type nanotube, metal composite comprising said nanotube and nanoparticle coated with said nanotube .

[Claim 18] The process for preparing the nanotube-dispersed composite of claim 16, wherein said nanotube comprises a single-wall or multi-wall carbon nanotube.

[Claim 19] The process for preparing the nanotube-dispersed composite of claim 17, wherein said functional group formed on the nanotube is hydroxy1 group, carboxylic acid group or functional group derivatized from carboxylic acid.

[Claim 20]

The process for preparing the nanotube-dispersed composite of claim 16, wherein the polymer having functional group is at least one polymer selected from a group consisting of polyamide polymer such as Nylon 6 and Nylon 6,6, etc . ; polyester polymer such as polyethylene terephthalate, polynaphthalene terephthalate, polylactic acid, and polymalic acid, etc.; polycarbonate polymer such as polyethylene carbonate, etc.; polyacetal polymer; polymer comprising polyphenylene ether; polymer comprising polyphenylene sulfide; polyurethane polymer,- epoxy polymer; polyoxyalkylene polymer such as polyethylene oxide and polypropylene oxide, etc.; polyolefinic polymer such as high density polyethylene, low density polyethylene, ethylene vinyl acetate copolymer, ethylene-acrylic acid copolymer, polypropylene and cyclic olefin copolymer, etc; styrene polymer such as polystyrene, styrene-acrylonitrile copolymer, styrene-methacrylic ester copolymer and ABS resin, etc.; halogen-containing polymer such as vinyl chloride polymer and vinylidene chloride polymer, etc.; acrylate polymer derivatized from (meth) acrylic acid or

(meth) acrylic acid ester; vinylacetate-containing polymer, vinylpyrrolidine-containing polymer or polyvinyl alcohols, and it comprises functional group at terminal or side chain group of the polymer.

[Claim 2l]

The process for preparing the nanotube-dispersed composite of claim 16, wherein the functional group of polymer is a terminal group or side chain group of the polymer.

[Claim 22]

The process for preparing the nanotube-dispersed composite of claim 21, wherein said functional group of polymer comprises an atom having electronegativity higher than that of the hydrogen of the nanotube or the hydrogen of the functional group of the nanotube .

[Claim 23] The process for preparing the nanotube-dispersed composite of claim 22, wherein said functional group of polymer is at least one group selected from a group consisting of amine group, hydroxyl group, carboxylic acid group, ester group and sulphonic acid group. [Claim 24]

The process for preparing the nanotube-dispersed composite of claim 16, wherein said polymer having functional group is the polymer with either chemical formula 1 or chemical formula 2 illustrated below.

[Chemical formula 1]

[Chemical formula 2]

(Wherein said chemical formula,

R₁ and R₄ are independently to each other a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, an alkoxy group, a carboxylic acid group, a primary amine, a secondary amine or a tertiary amine,

[Claim 25] Composition comprising the substrate polymer and the nanotube- dispersed composite of any one of claims 1 to 15.

[Claim 26]

The nanotube-dispersed composite of claims 1 to 15, wherein said nanotube-dispersed composite is selected from a film, a pellet and a bulk having a three-dimensional shape.