KR100887283B1 - Compatabilizer for polymer/carbonnanotube nanocomposite and polymer/carbonnanotube nanocomposite comprising the same - Google Patents

Abstract

The present invention relates to a dispersant capable of effectively dispersing carbon nanotubes in a polymer matrix and a polymer / carbon nanotube composite using the same. More specifically, the polythiophene main chain has strong π-π interaction with the carbon nanotubes. The present invention relates to a PMMA graft copolymer having a compatibility with various polymer matrices, and a polymer / carbon nanotube composite including the same as a dispersant.

Carbon nanotubes, dispersants, PMMA, polythiophenes, nanocomposites

Description

Dispersant for Polymer / Carbon Nanotube Nanocomposites and Polymer / Carbon Nanotube Composites Comprising the Same

The present invention relates to a dispersant capable of effectively dispersing carbon nanotubes in a polymer matrix and a polymer / carbon nanotube composite using the same. More specifically, the polythiophene main chain has strong π-π interaction with the carbon nanotubes. The present invention relates to a PMMA graft copolymer having a compatibility with various polymer matrices, and a polymer / carbon nanotube composite including the same as a dispersant.

Carbon nanotube (CNT) is a material in which one carbon is combined with other carbon atoms in a hexagonal honeycomb pattern to form a tube. The diameter of the tube is in the range of 1 to 100 nm, the length is up to several mm, and the anisotropy is very high. Big. Carbon nanotubes are single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and multiple carbon nanotubes depending on the number of walls. (rope carbon nanotube), carbon nanotubes show high electrical conductivity similar to that of metal by overlapping π electrons in the outer wall.

Multifunctional nanocomposites have been developed using the above excellent mechanical properties and electrical conductivity of carbon nanotubes. By adding carbon nanotubes to the polymer matrix instead of the existing inorganic reinforcing agents, it is possible to develop multifunctional nanocomposites with improved mechanical properties, thermal properties, and electrical conductivity at the same time. In addition, in order for the existing inorganic reinforcing material to show the effect properly, more than 15 wt% must be added, whereas in the case of carbon nanotubes, a small amount of less than 1 wt% can lead to the desired increase in physical properties.

In order to use carbon nanotubes as a reinforcing material of a polymer material, a technique of dispersing carbon nanotubes in a polymer matrix is important. Carbon nanotubes are agglomerated by van der Waals between the carbon nanotubes during the synthesis process.These agglomerated carbon nanotubes are not dissolved in water or organic solvents, so they are uniform in the polymer matrix. Hard to disperse Carbon nanotubes present in an aggregated state in the polymer matrix act as a weak point rather than as a reinforcing agent in the composite material, and thus do not sufficiently perform the role as a reinforcing material. Therefore, dispersing carbon nanotubes into individual objects in the polymer matrix is an important process in the development of successful polymer nanocomposites.

In order to solve these problems, physical modification methods using surfactants, polymer lapping, and the like, chemical modification methods for introducing functional groups on the surface of carbon nanotubes, and methods using dispersants or ultrasonication have been developed.

In Korean Patent Publication No. 2007-0013755 "Dispersant for a high concentration carbon nanotube solution and a composition comprising the same", a single molecule or a polymer in which the head is composed of hydrophobic chains and all the carbons in the head part of the head are substituted with fluorine Is used as a dispersant.

In Korean Patent Publication No. 2007-0016766 “Carbon Nanotubes Modified Using Pyrene Derivatives and Highly Dielectric Polymer / Carbon Nanotube Composites Using the Same and Methods for Manufacturing the Same” are prepared by mixing pyrene derivatives and carbon nanotubes with a solvent. Adsorption of pyrene derivatives to carbon nanotubes modifies the self-aggregation of carbon nanotubes.

In the present invention, in order to improve the interfacial adhesion between the carbon nanotubes and the polymer matrix, a dispersant capable of effectively dispersing the carbon nanotubes in the polymer matrix was developed, and a polymer / carbon nanotube composite prepared by using the same was developed.

An object of the present invention is to provide a dispersant capable of effectively dispersing carbon nanotubes in a polymer matrix, and to provide a polymer / carbon nanotube composite using a dispersant.

The present invention relates to a dispersant capable of effectively dispersing carbon nanotubes in a polymer matrix and a polymer / carbon nanotube composite using the same, and more particularly, to a polythiophene main chain having strong π-π interaction with carbon nanotubes; The present invention relates to a PMMA graft copolymer comprising a polymethyl methacrylate (hereinafter referred to as PMMA) brush having compatibility with various polymer matrices. The present invention also relates to a polymer / carbon nanotube composite including the PMMA graft copolymer as a dispersant.

The PMMA graft copolymer according to the present invention effectively disperses carbon nanotubes in the polymer matrix because the polythiophene backbone has strong π-π interaction with the carbon nanotubes and the PMMA brush exhibits compatibility with various polymer matrices. It can be usefully used as a dispersant. In addition, it is possible to provide a polymer / MWCNT nanocomposite in which carbon nanotubes are uniformly dispersed using the dispersant according to the present invention.

According to a suitable embodiment of the present invention, PMMA graft copolymer represented by the following structural formula (1) is provided.

[Formula 1]

(Where m = 3n, n is 1 to 30, k is an integer of 1 to 30)

According to another suitable embodiment of the present invention, there is provided a polymer / carbon nanotube composite including the PMMA graft copolymer as a dispersant, wherein the polymer is a vinyl copolymer.

According to another suitable embodiment of the invention, the vinyl copolymer is a monomer mixture of styrene, o-, m-, p-ethylstyrene, o-, m-, p-methylstyrene and methacrylic acid methyl ester It is characterized in that the compound prepared by copolymerizing one selected from the group consisting of one selected from the group consisting of acrylonitrile, methacrylonitrile and ethacrylonitrile.

According to another suitable embodiment of the present invention, the vinyl copolymer is a compound prepared by copolymerizing styrene and acrylonitrile.

According to another suitable embodiment of the present invention, by reacting 3-thiophenethanol and 2-bromoisobutyryl bromide, Compound I (2-bromo-2-methyl-propionic acid 2-thiophene-) Preparing 3-yl-ethyl ester, BMPT), reacting Compound I with 3-hexylthiophene, preparing Compound II of Formula 3 below, and using the compound II as a macroinitiator, methylmethacrylate. It provides a method for producing a polymethyl methacrylate graft copolymer comprising the step of atomic transfer radical polymerization.

[Formula 2]

[Formula 3]

(Where m = 3n and n is an integer from 1 to 30)

Hereinafter, the present invention will be described in detail.

PMMA graft copolymer (P (BMPT- co -HT) -g- PMMA), which is a dispersant according to the present invention, is reacted with 3-thiophene-ethanol, 2-bromoisobutyryl bromide and 3-hexylthiophene. After preparing a P (BMPT-co-HT) copolymer, methyl methacrylate is prepared by atomic transfer radical polymerization using the copolymer as a macro initiator.

[1] preparation of polythiophene backbone

As shown in Scheme 1 below, 3-thiopheneethanol and 2-bromoisobutyryl bromide were reacted at 25 ° C. to 35 ° C. for 24 hours in the presence of triethylamine. The reaction is carried out while stirring to synthesize 2-bromo-2-methyl-propionic acid 2-thiophen-3-yl-ethyl ester (2-Bromo-2-methylpropionic acid 2-thiophene 3-ylethyl ester, BMPT). . The molar ratio of 3-thiophene-ethanol and 2-bromoisobutyryl bromide may be 1: 1 to 2, preferably 1: 1.2. If the proportion of 2-bromoisobutyryl bromide is relatively high, unreacted 2-bromoisobutyryl bromide should be removed after the reaction, and if the ratio of 2-bromoisobutyryl bromide is lower than this, the reaction yield will be lowered. do.

Next, as shown in Scheme 2, 3-hexylthiophene was added to Compound I (BMPT), and reacted with stirring at 25 ° C. to 35 ° C. for 24 hours to give P (BMPT- co). -HT) copolymer. By changing the monomer composition ratio in the process of copolymerizing the BMPT and 3-hexylthiophene, the graft density of the polythiophene main chain can be controlled and the degree of polymerization of the PMMA can be controlled in various ways. Theoretically, there is no limitation on the molar ratio of the BMPT monomer and the 3-hexylthiophene monomer, but the graft density of the final carbon nanotube dispersant is determined by the molar ratio of the two monomers. If the graft density is too high, the interaction between the PMMA grafts weakens the efficiency of the dispersant. Therefore, the molar ratio of the BMPT monomer and the 3-hexylthiophene monomer is preferably 1: 1 to 1: 5.

Scheme 1

Scheme 2

(m = 3n, n is an integer from 1 to 30)

[2] polymerization of PMMA graft copolymer

As shown in Scheme 3 below, methyl methacrylate (Atmic Transfer Radical Polymerization, ATRP) was prepared using P (BMPT- co- HT) copolymer of compound II as a macroinitiator. ) PMMA graft copolymer P (BMPT- co -HT backed by the polythiophene by a) synthesizing an -PMMA g. At this time, irreversible termination reaction may occur in ATRP of MMA. To avoid this, a small amount of CuCl is added as a catalyst during the reaction. Inerts such as CuCl and CuBr ₂ are added to prevent irreversible termination in ATRP.

Scheme 3

(m = 3n, n is an integer from 1 to 30, k is an integer from 1 to 30)

The PMMA graft copolymer thus synthesized has strong π-π interaction with the polythiophene backbone and carbon nanotubes, and since the PMMA brush has compatibility with various polymer matrices, it is possible to effectively disperse the carbon nanotubes in the polymer matrix. Can be.

A method of preparing a polymer / carbon nanotube nanocomposite using the PMMA graft copolymer as a dispersant will be described below.

As the polymer according to the present invention, a vinyl copolymer may be used.

Vinyl copolymers that can be suitably used in the present invention are styrene, o-, m-, p-ethylstyrene, o-, m-, p-methylstyrene, halogen or alkyl substituted styrene, C1-C8 alkyl methacrylate 1 type selected from the group consisting of esters, C1-C8 acrylic acid alkyl esters or mixtures thereof, acrylonitrile, methacrylonitrile, ethacrylonitrile, C1-C8 methacrylic acid alkyl esters, C1-C8 acrylic acid It may be a copolymer of one selected from the group consisting of methyl esters, maleic anhydride, C1-C4 alkyl or phenyl N-substituted maleimides or mixtures thereof.

The C1-C8 methacrylic acid alkyl esters or C1-C8 acrylic acid alkyl esters are esters obtained from monohydryl alcohols containing 1 to 8 carbon atoms as alkyl esters of methacrylic acid or acrylic acid, respectively. Specific examples of these include methacrylic acid methyl ester, methacrylic acid ethyl ester, acrylic acid ethyl ester, acrylic acid methyl ester or methacrylic acid propyl ester.

Preferred vinyl copolymers of the present invention include acryl and one selected from the group consisting of monomer mixtures of styrene, o-, m-, p-ethylstyrene, o-, m-, p-methylstyrene and methacrylic acid methyl ester. The thing manufactured by copolymerizing 1 type chosen from the group which consists of ronitrile, methacrylonitrile, and ethacrylonitrile is mentioned.

The vinyl copolymer may be prepared by emulsion polymerization, suspension polymerization, solution polymerization or bulk polymerization, and it is preferable to use a weight average molecular weight of 15,000 to 600,000.

Other vinyl copolymers that may be suitably used in the present invention include those prepared from monomer mixtures of methyl methacrylate monomers and optionally acrylic acid methyl esters or acrylic acid ethyl esters. The methacrylic acid methyl ester polymer may be prepared by emulsion polymerization, suspension polymerization, solution polymerization or bulk polymerization, and a weight average molecular weight of 20,000 to 250,000 is preferably used.

In addition, another vinyl copolymer that may be suitably used in the present invention is a copolymer of styrene and maleic anhydride, and may be prepared using a continuous bulk polymerization method and a solution polymerization method. The composition ratio of the two monomer components can be varied in a wide range. Preferably, the content of maleic anhydride is 5 to 60% by weight, and the weight average molecular weight of the styrene / maleic anhydride copolymer is preferably 20,000 to 200,000. Do.

Hereinafter, a nanocomposite using poly (styren-co-acrylonitrile) (SAN) which is a copolymer prepared from styrene and acrylonitrile in the vinyl copolymer will be described.

Carbon nanotubes according to the present invention is a single-walled carbon nanotube (single-walled carbon nanotube), double-walled carbon nanotube (double-walled carbon nanotube), multi-walled carbon nanotube (hereinafter referred to as "MWCNT") ), Including bundle carbon nanotubes, and preferably multi-walled carbon nanotubes. It is commercially advantageous to use multi-walled carbon nanotubes, which are expensive and have high purity, compared to single-walled carbon nanotubes, which are expensive and have a relatively high impurity content.

<Production of SAN / MWCNT Nanocomposites>

SAN / MWCNT nanocomposites are prepared by solution mixing. After dissolving PMMA graft copolymer ((BMPT- co -HT) -g- PMMA) and MWCNT prepared in the above method in chloroform, it is sonicated for 1 to 2 hours. Thereafter, the SAN solution is added to the dispersion solution and then ultrasonicated for 10 to 20 minutes to prepare SAN / P (BMPT- co -HT) -g- PMMA / MWCNT nanocomposite. Nanocomposites prepared according to the present invention are characterized by containing 0.01% by weight to 1% by weight of MWCNTs relative to SAN. In addition, the PMMA graft copolymer and MWCNT added as a dispersant are preferably added in a ratio of 1: 1 (weight ratio).

Hereinafter, the present invention will be described in more detail with reference to Examples, but embodiments according to the present invention can be modified in many different forms, and the scope of the present invention is construed as being limited to the embodiments described below. Can not be done.

Example

Example 1 (Preparation of PMMA Graft Copolymer)

4 mL (0.036 mol) of 3-thiophenethanol (0.036 mol), 5.5 mL (0.040 mol) of triethylamine, and 40 mL of methylene chloride were added to a flask under a nitrogen atmosphere and then cooled at 0 ° C. Thereafter, 5.3 mL (0.043 mol) of 2-bromoisobutyl bromide dissolved in 10 mL of methylene chloride was slowly added dropwise to the reaction vessel under a nitrogen atmosphere. After addition, the reaction mixture was stirred at 30 ° C. for 24 hours. After filtering the white precipitate of triethylamine hydrochloride from the reaction mixture, the filtrate was diluted with 300 mL of diethyl ether, washed with 1% HCL, 5% Na ₂ CO ₃ and diluted with water. The residue condensed by evaporation of diethyl ether from the crude product of the diethyl ether layer was purified by silica column chromatography using a mixed solvent of ethyl acetate and n -hexane (5: 95 / v: v) to obtain BMPT. 8.9 g (0.032 mol, 89%) was obtained.

Next, 2.3 g (0.014 mol) of FeCl ₃ is added to the flask and purged with nitrogen gas. Thereafter, 20 mL of chloroform was added to the flask, and a solution of 1 g (0.0036 mol) of BMPT and 0.65 mL (0.0036 mol) of 3-hexylthiophene was added to the reaction flask under nitrogen atmosphere in 5 mL of chloroform. Thereafter, the reaction mixture was stirred at 30 ° C. for 24 hours, precipitated with 800 mL of methanol, filtered and washed to obtain 0.67 g of P (BMPT- co- HT).

Next, 10 mg (0.075 mmol) of CuBr and 1.4 mg (0.015 mmol) of CuCl were added to the reaction flask, and gas removal and filling were repeated three times with argon gas. 10 mL of degassed toluene was added to the flask in three freeze-and-thaw cycles, and then 0.8 mL (7.5 mmol) of MMA was added, followed by 30 mg of P (BMPT- co- HT) and 5 mL of toluene. . Finally, 0.03 mL (0.15 mmol) of PMDETA was added. After three freeze / melt cycles, the reaction mixture was stirred at 90 ° C. for 1 hour, diluted with 50 mL of chloroform to dissolve the polymer, filtered and washed and dried to obtain PMMA graft copolymer (P (BMPT- co- HT)). g- PMMA) 0.1 g was obtained.

Example 2 (SAN / P (BMPT- co -HT) -g- PMMA / MWCNT Nanocomposite Film Preparation)

1 mg of PMMA graft copolymer (P (BMPT- co -HT) -g -PMMA) and 1 mg of MWCNT (0.05 wt% of SAN) were added to 20 mL of chloroform, sonicated for 1 hour, and the dispersion solution contained 2 g of SAN. Into 20 mL chloroform solution. The mixture was sonicated for another 10 minutes and precipitated with excess methanol. The precipitate was filtered off, washed with methanol and dried to give a SAN / P (BMPT- co -HT) -g- PMMA / MWCNT solution.

The method for producing a nanocomposite film using the nanocomposite solution obtained by the above method is as follows. The nanocomposite solution is poured onto a glass plate and then a solution film is prepared using a doctor blade. Thereafter, the solvent was slowly evaporated at room temperature for 6 hours and completely dried in vacuum at 30 ° C. for 24 hours to prepare SAN / P (BMPT- co -HT) -g- PMMA / MWCNT nanocomposite film.

Example 3

The same procedure as in Example 2 was carried out except that 0.3 mg of PMMA graft copolymer (P (BMPT- co -HT) -g- PMMA), 0.3 mg of MWCNT (1% by weight of SAN), and 30 mg of SAN were used. The resulting SAN / MWCNT nanocomposite was dissolved in 20 mL of chloroform, and then fluorescence emission spectra were measured using fluorescence spectroscopy. In addition, FE-SEM (Field Emission Scanning Electron Microscope) image is shown in Figure 3a.

Comparative Example 1 (Manufacture of SAN / MWCNT Nanocomposite Film)

SAN / MWCNT composites were prepared by dispersing 1 mg (0.05 wt%) of carbon nanotubes using chloroform in 2 g of SAN. FE-SEM (Field Emission Scanning Electron Microscope) image of the prepared nanocomposite film is shown in Figure 3b.

FIG. 2 shows the π-π interaction between polythiophene and MWCNT of PMMA graft copolymer as a dispersant, measured by fluorescence spectroscopy. Referring to Figure 2, when the dispersant according to the present invention is observed at 420nm strong fluorescence emission is observed, in the case of the SNA / MWCNT nanocomposite containing the dispersant it can be observed that the fluorescence emission disappears. This disappearance results from efficient energy transfer as a π-π interaction between MWCNTs and the polythiophene of the dispersant. Therefore, this fluorescence emission spectra is evidence that π-π interaction occurs between MWCNT and polythiophene of dispersant.

FIG. 3A shows the FE-SEM image of the SAN / MWCNT composite film including the dispersant of Example 3, and FIG. 3B shows the FE-SEM image of the SAN / MWCNT composite film without the dispersant of Comparative Example 1, respectively. It is shown. In FIG. 3A we can see the MWCNTs (bright spots) uniformly distributed in the SAN matrix. On the other hand, in FIG. 3B, it can be observed that MWCNTs are aggregated in the SAN matrix.

Figure 4 shows the π-π interaction between the polythiophene and MWCNTs of the dispersant in Raman spectroscopy. MWCNTs exhibit characteristic peaks at 1350 cm ^{- 1} and 1570 cm ^{- 1} , respectively, called D-band and G-band. When the MWCNT interacts with the material introduced from outside, the position of the G-band is shifted to the right (this is called upshift). 4, it can be seen that the G-band of the SAN / MWCNT (c) containing the dispersant has moved to the right side as compared to the MWCNT (a) and the SAN / MWCNT (b). This is evidence that MWCNTs have a π-π interaction with the dispersant according to the invention.

By dispersing the carbon nanotubes uniformly in the polymer matrix using the dispersant according to the present invention, the carbon nanotubes can be used as a reinforcing material of the polymer material.

Figure 1 schematically shows a synthetic route of the dispersant for carbon nanotubes according to the present invention.

Figure 2 shows the fluorescence emission spectra of the carbon nanotube dispersant according to the present invention and the polymer / carbon nanotube composite using the same.

Figure 3a is a FE-SEM image of the SAN / MWCNT nanocomposite using the polymethyl methacrylate graft copolymer according to the present invention, Figure 3b is a FE-SEM image of the SAN / MWCNT nanocomposite without the dispersant to be.

4 shows Raman spectroscopy for MWCNT (a), SAN / MWCNT (b) and SAN / polymethylmethacrylate graft copolymer / MWCNT (c).

Claims (6)

Polymethyl methacrylate graft copolymer represented by the following structural formula 1. [Formula 1]

(Where m = 3n, n is an integer from 1 to 30, k is an integer from 1 to 30) A polymer / carbon nanotube composite comprising the polymethyl methacrylate graft copolymer of claim 1 as a dispersant. The polymer / carbon nanotube composite according to claim 2, wherein the polymer is a vinyl copolymer. 4. The vinyl copolymer of claim 3, wherein the vinyl copolymer is selected from the group consisting of monomer mixtures of styrene, o-, m-, p-ethylstyrene, o-, m-, p-methylstyrene and methacrylic acid methyl ester. Polymer / carbon nanotube composite, characterized in that the compound prepared by copolymerizing one species selected from the group consisting of acrylonitrile, methacrylonitrile and ethacrylonitrile. The polymer / carbon nanotube composite according to claim 3, wherein the vinyl copolymer is a compound prepared by copolymerizing styrene and acrylonitrile. Reaction of 3-thiopheneethanol with 2-bromoisobutyryl bromide to prepare Compound I (2-bromo-2-methyl-propionic acid 2-thiophen-3-yl-ethyl ester, BMPT) Making; Reacting Compound I with 3-hexylthiophene to prepare Compound II of Formula 3; And A method for producing a polymethyl methacrylate graft copolymer comprising the step of atomic transfer radical polymerization of methyl methacrylate using the compound II as a macro initiator. [Formula 2]

[Formula 3]

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