KR20070016766A - Modification of carbon nanotubee by pyrene derivatives and its application to preparation of polymer/carbon nanotube nanocomposite of high dielectric constant - Google Patents

Abstract

The present invention relates to carbon nanotubes and polymer / carbon nanotube composites in which self-aggregation is modified by adsorbing pyrene derivatives to carbon nanotubes, and a method of manufacturing the same. The use of carbon nanotubes adsorbed with pyrene derivatives has dramatically improved the dispersion efficiency in polymers, and thus polymer / carbon nanotube composites having high dielectric constant and refractive index can be prepared.

Carbon nanotube, polymer / carbon nanotube composite, pyrene, dielectric, dielectric constant

Description

Modified carbon nanotubes using pyrene derivatives, highly dielectric polymer / carbon nanotube composites using the same, and methods for preparing the same }

1 is a graph showing the change in dielectric constant of the polymer / carbon nanotube composite using only carbon nanotubes treated with acid.

2 is a transmission electron microscope (TEM) image of purified carbon nanotubes after acid treatment, which is a first embodiment of the present invention.

3 is an atomic force microscope (AFM) image of a carbon nanotube to which a pyrene derivative, which is a second embodiment of the present invention, is adsorbed.

Figure 4 is a graph showing the change in dielectric constant of the polymer / carbon nanotube composite of a third embodiment of the present invention.

Figure 5 is a photograph showing the transparency test results of the polymer / carbon nanotube composite of the third embodiment of the present invention.

The present invention relates to carbon nanotubes adsorbing pyrene derivatives and polymer / carbon nanotube composites using the same, and a method for preparing the same, wherein carbon nanotubes adsorbing the pyrene derivatives are self-aggregated with carbon nanotubes. It is a carbon nanotube modified the phenomenon, the composite of the carbon nanotube and the polymer is excellent in dispersion stability and the dielectric constant is increased dramatically to achieve a high dielectric constant.

Advances and commercialization of advanced technologies are based on the development of the material industry, and with the advent of new technologies, there is an urgent need for high functionalization of materials and their environmentally friendly production. As traditional, relatively simple materials already exhibit many problems and limitations in their performance and function, one of the effective ways to overcome them is to provide a variety of different thermodynamic and rheological properties, such as organic-inorganic hybrid materials. Efforts are being made to achieve synergies in functionality and performance by integrating components by physical or chemical methods.

In particular, there is a growing interest in integrated passive or embedded passive devices that integrate a single layer of a multilayered substrate for lighter, shorter and higher electrical performance of electronic products. It is a polymer composite.

Polymer composites are one of the candidate materials for embedded passive devices, and many researches are currently being conducted on the possibility that the use of a polymer and a high dielectric filler together can realize the advantages of excellent processability of the polymer and a high dielectric constant of the high dielectric filler. have. Polymer composites have a low process temperature and low manufacturing cost, and have excellent dielectric properties, processability, and room temperature storage.

Currently, high dielectric fillers include SrTiO ₃ (STO), (Ba, Sr) TiO ₃ (Barium Strontium Titanate; hereinafter referred to as BST), (Pb, La) TiO ₃ (PLT), and the like. In order to obtain a high dielectric constant, a high amount of high dielectric filler must be blended, but there is a limit in terms of increasing the filler content due to the very low compatibility of the polymer and the inorganic filler, which causes a serious deterioration of physical properties such as mechanical strength and heat resistance.

Therefore, the nanocomposite, which has a significantly reduced size of the dispersed phase and is maintained at 100 nm or less as compared with the conventional complex having a relatively macroscopic dispersion, has recently attracted attention as a new type of material expressing high performance. .

In particular, a method of dispersing carbon nanotubes in existing materials has been proposed as an alternative to significantly improve the properties of existing materials. Carbon nanotubes are generally extremely fine cylindrical materials having an aspect ratio ranging from tens to thousands, with diameters of several nm to several tens of nm and lengths of several to several hundred micrometers. Its thermal conductivity is nearly twice that of diamond and 1,000 times higher than that of copper, resulting in excellent properties such as nanoscale electrical, electronic devices, nanosensors, optoelectronic devices and high-performance composites. The possibility is very high. Therefore, many countries around the world are investing heavily in researching nanocomposite materials in which carbon nanotubes are dispersed in existing materials such as metals, ceramics, or polymers.

However, impurities such as metal catalyst particles, amorphous carbon, graphite, spheroidal fullerenes, etc. are present in the carbon nanotubes. When combined with a polymer, the carbon nanotubes not only deteriorate dispersing properties but also degrade mechanical and electrical properties. .

In addition, the development of nanocomposite materials has been delayed because the existing process cannot solve the problem of heterogeneous dispersion and mixing of carbon nanotubes in existing materials due to the strong cohesion of carbon nanotubes.

Conventional attempts have been made to improve the nanotube dispersibility during the polymer compounding process by removing the carbon, catalyst, and impurities and introducing functional groups on the surface of nanotubes, but have not yet succeeded in obtaining stable and improved electrical properties. Therefore, there is an urgent need for new nanocomposite materials having the desired mechanical, physical and electrical properties.

As a result of our efforts to develop new materials, the present inventors have solved the dispersion and mixing problems that have been the biggest obstacles in the production of nanocomposites using carbon nanotubes, and have excellent strength, thermal and electrical conductivity of carbon nanotubes, A new nanocomposite material was developed using field emission characteristics.

It is a first object of the present invention to provide a carbon nanotube and a method for producing the same, wherein the pyrene derivative is adsorbed on the carbon nanotube to modify the self-aggregation phenomenon of the carbon nanotube.

It is a second object of the present invention to provide a polymer / carbon nanotube composite having a high dielectric constant and high refractive index, which is uniformly dispersed in a polymer containing carbon nanotubes on which pyrene is adsorbed, and a method of manufacturing the same. .

The present invention synthesizes a pyrene derivative by substituting an aliphatic branch of a hydrogen atom of pyrene, mixing the pyrene derivative and carbon nanotubes with a solvent, and adsorbing a pyrene derivative to carbon nanotubes. It relates to a method for producing nanotubes and carbon nanotubes prepared by the above method. The surface of carbon nanotubes is modified to suppress self-aggregation.

The present invention also comprises the steps of dispersing the carbon nanotubes adsorbed the pyrene derivative in a solvent; Mixing a polymer resin into a solution in which the carbon nanotubes are dispersed; It relates to a method for producing a polymer / carbon nanotube composite and a polymer / carbon nanotube composite prepared by the method comprising the step of film-casting the mixture and removing the solvent and then heating for a predetermined time. The polymer / carbon nanotube composite of the present invention has excellent dispersion efficiency, and thus has high dielectric constant and high refractive index.

Referring to the present invention in more detail as follows.

The smaller the material, the stronger the ability to aggregate with the surrounding material. Carbon nanotubes are also highly cohesive, which makes it difficult to disperse and mix homogeneously in polymers. However, the carbon nanotubes of the present invention have modified the surface by adsorbing pyrene derivatives, thereby making it possible to remarkably improve self-cohesiveness.

The pyrene derivative according to the present invention is produced by replacing various aliphatic branches with pyrene. Aliphatic branches include butyroyl chloride, CH _3- (CH ₂ ) ₂ -COOCl, and hexanoyl chloride (CH _3- (CH ₂ ) ₄ -COOCl), octanoyl chloride with similar structures. (octanoyl chloride, CH _3- (CH ₂ ) ₆ -COOCl), decanoyl chloride, CH _3- (CH ₂ ) ₈ -COOCl, dodecanoyl chloride, CH _3- (CH ₂ ) ₁₀ -COOCl), tetradecanoyl chloride (CH _3- (CH ₂ ) ₁₂ -COOCl), hexadecanoyl chloride (CH _3- (CH2) ₁₄ -COOCl), octadecanoyl chloride chloride, CH _3- (CH2) ₁₆ -COOCl). The following formula (1) shows the structural formula of butyroyl chloride.

[Formula 1]

In order to modify the surface of the carbon nanotubes according to the present invention, the carbon nanotubes are mixed in a solution containing the pyrene derivative. Pyrene is adsorbed on the surface of carbon nanotubes by π-π interaction. In other words, surface modification is achieved by adsorption of pyrene derivatives to carbon nanotubes in solution. The solvent used in the present invention is preferably dimethylformamide (hereinafter referred to as 'DMF').

3 is an AFM image of a carbon nanotube on which a pyrene derivative is adsorbed, and a bundle-type single-walled carbon nanotube aggregate is separated into individual carbon nanotubes through a section analysis. Confirmed. From this, a small amount of carbon nanotubes can be used to form a network when complexed to a polymer, and a very small amount of carbon nanotubes having a percolation state of the nanotubes in which an electron transfer network is constructed between the nanotubes is formed. It can be seen that even using.

The present invention also comprises a polymer comprising the step of dispersing the carbon nanotubes adsorbed by the pyrene derivative in a solvent, mixing the polymer resin in the dispersion, film casting the mixed solution, removing the solvent, and curing by heating for a predetermined time. It is composed of a method for producing a carbon nanotube composite and the resulting polymer / carbon nanotube composite.

The polymer resin used in the present invention may be used as both the thermosetting resin and the thermoplastic resin as a compound of the composite. In detail, epoxy, which is a thermosetting resin, may be used.

Although it is preferable to use DMF as a reaction solvent used for this invention, it is not necessarily limited to this.

Carbon nanotubes used in the present invention may be used single-walled, double-walled, multi-walled carbon nanotubes, bundle type carbon nanotubes or mixtures thereof, the size of which can be used in various ways depending on the use of the composite have. In addition, considering the ease of mass production, workability, economical efficiency, ease of production, characteristics of the composite and ease of purchase, it is preferable to have a length of 100 nm to 100 μm and a diameter of 0.5 nm to 50 nm. .

As a method of dispersing carbon nanotubes in the polymer resin, all of the stirring methods used to uniformly mix the solid particles in the polymer solution may be applied, as well as a suitable dispersant. In particular, when dispersing nano-sized carbon nanotubes, it is preferable to use an ultrasonic dispersion method for uniform dispersion.

As shown in FIG. 2, the polymer / carbon nanotube composite of the present invention suppresses self-aggregation of carbon nanotubes and has excellent dispersion efficiency.

1 is a graph showing a change in dielectric constant of a polymer / carbon nanotube composite prepared by using carbon nanotubes in which impurities are removed and surface modification is performed through acid treatment. It was not long enough. However, referring to FIG. 4, which shows a change in the dielectric constant of the present invention, it can be seen that the dielectric constant is significantly increased compared to FIG. 1.

In addition, as shown in FIG. 5, it was possible to provide an excellent polymer film that has been supplemented with transparency and mechanical properties. When the dielectric is manufactured from a high dielectric film having excellent transparency and mechanical properties, it can be directly applied to manufacturing a built-in passive device for flexible electronics or a supercapacitor with transparency.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

Example

Example 1 Purification Method of Carbon Nanotubes

After refluxing 0.5 g of carbon nanotubes in 100 ml of nitric acid solution (5M HNO ₃ ) for 6 hours, the fine solid was filtered and neutralized with distilled water. After repeating this process again, the carbon nanotubes were purified by freeze drying for 48 hours.

Figure 2 is a transmission electron microscope (TEM) image of the carbon nanotubes purified by the above method, it was confirmed that the impurities were removed through this.

Example 2 Surface Modification Method of Carbon Nanotubes

According to the present invention, carbon nanotubes adsorbed with a pyrene derivative in order to modify the surface of the carbon nanotubes were synthesized as follows. Pyrene derivatives with various aliphatic branches were synthesized. The pyrene used was 1-aminopyrene of formula (2), and as the aliphatic branch, butyroyl chloride (CH _3- (CH ₂ ) of formula (1) ₂ -COOCl) was used.

[Formula 2]

Example 3 Preparation of Polymer / Carbon Nanotube Composites

Epoxy / carbon nanotube composites were prepared in the following manner using an epoxy resin as a polymer resin.

1 mg of carbon nanotubes were mixed in 10 mL of a 10 mM pyrene derivative / DMF solution, and the carbon nanotubes were dispersed by sonication. 2 mL of the dispersion solution was taken and mixed into an unreacted epoxy resin and hardener mixture. In the case of dielectric production, the concentration condition before percolation is preferable, and the carbon nanotube content of the matrix component was determined at 0.04 wt% in order to obtain a dielectric constant result under a small amount of carbon nanotube conditions. At this time, as a control, 1 mg of carbon nanotubes treated only with acid were dispersed in 10 mL DMF by ultrasonic dispersion, and 2 mL of the solution was taken and mixed with the epoxy resin and the curing agent mixture. At this time, the concentration of carbon nanotubes was also 0.04 wt% compared to epoxy. Next, the mixtures were film casted, the solvent was removed, and then cured by heating for a predetermined time to prepare an epoxy / carbon nanotube composite.

As a result of measuring the dielectric constant in the range of 100 Hz to 100 KHz for each of the prepared composite films, a dielectric constant of 10 or less was obtained when acid-treated carbon nanotubes were used in the composite (FIG. 1). Since the dielectric constant of the epoxy resin constituting the matrix of the composite is about 6 or 7, when the carbon nanotubes acid-treated at 0.04 wt% concentration are present in the composite, the change of dielectric constant was not large. However, when carbon nanotubes modified with pyrene derivatives were used in the composite at the same concentration, a very high dielectric constant of 500 or more was obtained (FIG. 4).

This large increase in dielectric constant resulted in a much better dispersion of carbon nanotubes due to the presence of pyrene derivatives on the surface of carbon nanotubes, and thus the interfacial polarization phenomenon due to the increased interface area between carbon nanotubes and epoxy. polarization) is the result.

The carbon nanotubes adsorbed with the pyrene derivative of the present invention prevents entanglement of carbon nanotubes and solves the problem of heterogeneous dispersion and mixing of existing carbon nanotubes. In addition, the polymer / carbon nanotubes of the present invention is significantly improved dispersibility, has a high dielectric constant and high refractive index, excellent transparency, mechanical properties and the like. High refractive nano composite materials can be used not only for the production of high-performance optical lenses and optical fibers, but also for various optical recording media. Conductive thermoplastic resins are effectively applied to electrostatic coating processes due to the dramatic improvement in paintability. Not only can it accelerate the metal replacement of metals, but it can also be used as a material for electromagnetic shielding materials and embedded passive devices.

Claims (9)

A carbon nanotube characterized in that a pyrene derivative in which a hydrogen atom of pyrene is substituted with an aliphatic branch is adsorbed on the surface of the carbon nanotube. The method of claim 1, wherein the pyrene is characterized in that 1-aminopyrene according to the formula

Carbon nanotubes. The method of claim 1, wherein the aliphatic branch is butyroyl chloride (CH _3- (CH ₂ ) ₂ -COOCl), hexanoyl chloride (CH _3- (CH ₂ ) ₄ -COOCl), Octanoyl chloride (octanoyl chloride, CH _3- (CH ₂ ) ₆ -COOCl), decanoyl chloride, CH _3- (CH ₂ ) ₈ -COOCl, dodecanoyl chloride, CH _3- (CH ₂ ) _10- COOCl), tetradecanoyl chloride (CH _3- (CH ₂ ) ₁₂ -COOCl), hexadecanoyl chloride (CH _3- (CH2) ₁₄ -COOCl), octadecanoyl chloride chloride, CH _3- (CH2) ₁₆ -COOCl). A method for producing carbon nanotubes, comprising adsorbing a pyrene derivative to carbon nanotubes by mixing the carbon nanotubes of claim 1 with a solvent. The method of claim 4, wherein the solvent is dimethylformamide. Dispersing the carbon nanotubes adsorbed with the pyrene derivative of claim 5 in a solvent; Mixing a polymer resin into a solution in which the carbon nanotubes are dispersed; Film-casting the mixed solution, removing the solvent, and curing the mixture by heating for a predetermined time. Method for producing a polymer / carbon nanotube composite, comprising a. The method of claim 6, wherein the polymer resin is an epoxy resin. The method of claim 6, wherein the solvent is dimethylformamide. A polymer / carbon nanotube composite comprising carbon nanotubes on which the pyrene derivative of claim 1 is adsorbed.

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