KR101812536B1 - Wet spinningMethod for preparing GO-CNT composite fibers, GO-Graphene composite fibers, GO-Grephene-CNT composite fibers - Google Patents

Abstract

The present invention provides a method for preparing a graphene oxide / carbon nanotube dispersion, comprising the steps of: a) preparing a graphene oxide / carbon nanotube dispersion, a graphene oxide / graphene dispersion or a graphene oxide / graphene / carbon nanotube dispersion; b) CTAB to the dispersion liquid, chitosan, CaCl _2, NaOH, at least one member selected from the group consisting of KOH first coagulation components, and polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyethylene imine (PEI ), Polyvinylpyrrolidone (PVP), and polyethylene oxide (PEO), to produce a gel fiber; And c) drying the gel fiber to provide a graphene oxide / carbon nanotube conjugated fiber, a graphene oxide / graphene conjugated fiber or a graphene oxide / graphene / carbon nanotube conjugated fiber do.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing graphene oxide / carbon nanotube conjugated fiber, graphene oxide / graphene conjugated fiber or graphene oxide / graphene / carbon nanotube conjugated fiber using a wet spinning process, GO-Graphene composite fibers, GO-Grephene-CNT composite fibers}

The present invention relates to a method for producing graphene oxide / carbon nanotube composite fibers, graphene oxide / graphene composite fibers or graphene oxide / graphene / carbon nanotube composite fibers using a wet spinning process.

Nano-carbon materials such as Graphene and Carbon-Nanotube (CNT) have excellent electrical properties, thermal properties, flexibility, and mechanical strength, so that they can be used as next generation electronic materials, It is a high-tech material attracting attention as a material.

Graphene is a carbon isotope with a two-dimensional planar structure in which carbon atoms form a hexagonal honeycomb structure by sp ² hybridization. The thickness of the single-layer graphene is 0.2 to 0.3 nm, which is one carbon atom thick. Hereinafter, the laminated graphene structure of about two or three layers is also within the general graphene category.

As a method of producing graphene, there are known chemical vapor deposition (CVD), epitaxial growth, nonoxidative exfoliation, and chemical exfoliation. Among them, the chemical vapor deposition method, the epitaxial growth method, and the non-oxidative peeling method are advantageous in that they can obtain high quality pure graphene. However, since the graphene yield is low, mass production is difficult and the manufacturing cost is high. There is a big restriction on.

As shown in FIG. 1, the chemical peeling method is a method in which graphene oxide (Graphene Oxide) is formed by oxidizing graphite with a strong acid (nitric acid, sulfuric acid or the like) and peeling by mechanical (ultrasonic pulverization or homogenizer pulverization) 'GO') [Fig. 1 (a)] and then removing the oxygen functionality through a series of chemical reduction [Fig. 1 (b)] and / or thermal reduction process [Fig. 1 (c) (Reduced GO, 'rGO') 'to distinguish it from pure graphene, as a method for producing a pin [FIG. 1 (d)]. In the 'reduced graphene oxide (rGO)', a few carbon defects are generated on the surface of the graphene during the oxidation and reduction of graphene, and it is difficult to completely remove the oxygen functional groups, Is widely used at present because it has a low electrical conductivity, but can be mass-produced, has a low manufacturing cost, and has no significant difference in electric conductivity and thermal conductivity compared to pure graphene.

Graphene oxide (rGO) has electrical properties that are quite different from graphene due to the oxygen functional groups generated during the oxidation process. Graphene itself is a non-polar, hydrophobic, and 100-fold higher electrical conductivity than copper at room temperature, since it is a carbon isotope, whereas graphene oxide is formed by the oxygen functional groups (epoxy, hydroxy, carboxy, etc.) Polarity, and hydrophilic, and has an insulator or extremely low electrical conductivity and thermal conductivity.

Although graphene oxide (GO) belongs to the intermediate of reduced graphene oxide (rGO), surface modification is facilitated owing to the oxygen functional groups formed in the graphene oxide, and functional materials can be bonded, As a promising material. For example, a biomolecule or a polymer such as a nucleic acid, a DNA (single chain), an RNA, an extramamer, a peptide, a protein, an antibody, a growth factor, Quenching).

Carbon nanotubes (CNTs) are carbon nanotubes of hexagonal honeycomb structure with carbon atoms sp ² hybridized. Single-walled carbon nanotubes (SWNTs) , Double-walled carbon nanotubes (DWNTs), and multi-walled carbon nanotubes (MWNTs).

The carbon nanotube manufacturing method is known as a chemical vapor deposition method, an arc discharge method, a laser evaporation method, a plasma torch method, and an ion impact method. Among them, the chemical vapor deposition method has an advantage of mass production and growth control of carbon nanotubes.

Since graphene and carbon nanotubes have high electrical conductivity and specific surface area, electrodes (electrode active material) for use in supercapacitors, sensors, batteries and actuators, touch panels, flexible displays, high efficiency solar cells, heat dissipation films, coating materials, Filters, electrodes for secondary batteries, ultra-fast chargers, and the like.

Recently, the existence of graphene, graphene oxide, carbon nanotubes and their physical properties have been known, and various studies have been made to fabricate them as fibers or composite fibers. Particularly, researches using wet spinning processes are being actively carried out.

Fig. 2 is a schematic diagram showing a wet spinning process (a) of graphene oxide and a process (b) in which graphene oxide (or graphene, nanocarbon tube) is aligned in a wet spinning process.

Referring to FIG. 2, the graphene oxide spinning solution is discharged into a coagulation bath through a spinneret (discharge nozzle) and agglomerates. The graphene oxide aligning process is performed by using a graphene oxide (I) of the nozzle by shear stress between the fluids as they move along the spinneret of the fine inner diameter, and the graphene oxide aligned after being discharged into the coagulation bath is subjected to sovent change Gel fiber is formed by self-assembly through a process (II), and the gel fiber is formed into a graphene oxide fiber through a series of drawing, washing and drying processes. The prepared graphene oxide fibers are subjected to an additional process for thermal or chemical reduction treatment of the graphene oxide fibers for electrical properties. The wet spinning process of graphene and carbon nanotubes is not significantly different from the graphene oxide spinning process described above. However, as described later, the coagulating bath characteristics are completely different. Conventionally known wet spinning processes include graphene oxide / Or graphene oxide / carbon nanotube composite fibers is practically impossible.

In the wet spinning process, it is very important to select the type and characteristics of the spinning solution and the suitable coagulation bath composition and composition. Graphene and carbon nanotubes are nonpolar, Polarity and water-solubility, it has a coagulating bath property completely different from graphene and carbon nanotubes.

Coagulation bath characteristics of graphene, carbon nanotube

Since graphene and carbon nanotubes are nonpolar and hydrophobic and aggregate with each other due to the interlayer van der Waals force, they do not dissolve in water at all, and they do not dissolve well in most organic solvents. Therefore, graphene and carbon nanotube dispersions are prepared through surfactant and ultrasonic treatment and used as spinning solution.

Examples of coagulation components of graphene and carbon nanotubes include polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyethyleneimine (PEI), polyvinylpyrrolidone (PVP), polyethylene oxide (PEO) Are known as water-soluble polymers. When the graphene spinning solution or the carbon nanotube spinning solution is radiated to the coagulating bath through the nozzle, the water-soluble polymer penetrates the spinning fiber to replace the surfactant to form a polymer matrix on the fiber, , More precisely, graphene / polymer composite fibers, carbon nanotube / polymer composite fibers are produced.

Korean Patent Laid-Open Publication No. 10-2012-0105179 discloses a method for producing a dispersion comprising: a) dispersing graphene (reduced graphene or reduced graphene oxide) together with a surfactant in a solvent to prepare a dispersion; And b) wet-spinning the dispersion with a polymer (PVA) solution, followed by drying to prepare a fiber. Also disclosed is a method for producing a graphene / PVA composite fiber,

Korean Patent Laid-Open No. 10-2012-0107026 discloses a method for producing graphene fibers by further treating a graphene / PVA conjugate fiber produced in the above patent with heat treatment or treatment with strong acid to remove PVA polymer.

Korean Patent Registration No. 10-1182380 discloses a method of producing a graphene / carbon nanotube / PVA conjugate fiber by spinning a graphene / carbon nanotube dispersion liquid into a PVA coagulating bath, wherein the graphene graphene oxide (RGO) or a chemically modified reduced graphene oxide (RCCG), rather than a graphene oxide (GO).

The wet spinning process of carbon nanotube fibers is disclosed in various documents as follows.

Vigolo et al. Prepared a 0.35 wt% SWNT dispersion using a surfactant (1.0 wt% sodium dodecylsulfonate (SDS)) and then spinning it in a 5 wt% polyvinyl alcohol (PVA) / distilled water coagulating bath to first produce carbon nanotube fibers (Vigolo, B. et al., Macroscopic fibers and ribbons of oriented carbon nanotubes, Science 290, 1331-1334 (2000)).

Munoz et al. Prepared SWNT dispersions using cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), and lithium dodecylsulfonate (LDS) surfactants and then dissolved in a polyethyleneimine (PEI) / distilled water coagulation bath (SWNT / PEI) fibers were prepared by spinning ( Adv. Mater . 2005, 17, No. 8, April 18). It was confirmed that the prepared SWNT / PEI fiber had a 100 times increase in electrical conductivity compared to the SWNT / PVA composite fiber.

Winey et al. (Winey et al., Macromolecules , 2004, 37, 9048) disclose a method for producing a CNT composite film using polymethyl methacrylate (PMMA) as a coagulating agent.

Smalley et al. Disclosed a method for producing a CNT composite film using PVA / PVP as a coagulating agent.

Coagulation bath characteristics of graphene oxide

Unlike the graphene and carbon nanotubes described above, CTAB, chitosan, CaCl ₂ , NaOH, KOH and the like are known as coagulation baths of graphene oxide, and CTAB is mainly used among them.

The coagulation process of graphene oxides is based on non-solvent precipitation using positively charged molecules such as CTAB, dispersion destabilization using NaOH ( Nat. Comm. 2011, 2, 571.) , Ionic cross-linking with divalent ions (Ca ²⁺ ) using CaCl ₂ ( Adv. Mater. 2013, 25, 188.), and polyelectrolyte complexation using chitosan ) ( Adv. Func. Mater . 2013, 23, 5345.) are known.

It should be noted that graphene oxide and graphene / carbon nanotubes have different coagulating bath characteristics, and thus, in the conventional wet spinning process, graphene oxide / carbon nanotube conjugated fiber, graphene oxide / It is impossible to manufacture a pin oxide / (graphene + carbon nanotube) conjugated fiber.

For example, CTAB, which is a coagulant of graphene oxide, acts as an anti-dispersant in carbon nanotubes, so when the graphene oxide / carbon nanotube dispersion is spun into a CTAB coagulation bath, the graphene oxide solidifies but the carbon nanotubes do not solidify (Gelling) of graphene oxide / carbon nanotube having a quantitative ratio is not generated. On the other hand, since PVA acts as a coagulant for carbon nanotubes and graphenes, but acts as a dispersant for graphene oxide, when the graphene oxide / carbon nanotube dispersion is spun into a PVA coagulation bath, carbon nanotubes and graphene But the graphene oxide is not solidified and no gelling occurs.

As described above, graphene and carbon nanotubes are excellent in electrical conductivity and thermal conductivity, and fibers produced thereby are also excellent in electrical conductivity and thermal conductivity. Conversely, graphene oxide has low electrical conductivity and low thermal conductivity, so that fibers produced are also insulators, have low electrical conductivity and thermal conductivity.

Therefore, the composite fiber composed of graphene oxide and carbon nanotube (or graphene) can control the electrical conductivity and thermal conductivity according to the content ratio of GO and CNT, and can control the mechanical properties such as tensile strength, elasticity and elongation Can be maximized. In contrast, rGO and CNT inevitably cause defect and particle size reduction during ultrasonic treatment, whereas the GO used in the wet process has excellent mechanical properties because GO having a mean particle size of several tens of μm is used, Excellent conductivity.

In addition, graphene oxide can introduce various functional materials such as biomolecules (nucleic acids, platamers, enzymes, etc.) and polymers in comparison with graphene and carbon nanotubes, while additional electrical / chemical thermal / The functional substance is decomposed or destroyed by the reduction process and the post-process, so that the function is attenuated or lost. Therefore, it is required to develop fibers having high electrical conductivity without the above-mentioned reduction step and post-treatment step.

The present invention relates to a graphene oxide / carbon nanotube composite fiber having a predetermined electrical conductivity, thermal conductivity and mechanical properties by using a wet spinning method, a graphene oxide / graphene composite fiber or a graphene oxide / graphene / carbon nanotube composite And to provide a method for producing fibers.

According to an aspect of the present invention,

a) preparing a graphene oxide / carbon nanotube dispersion, a graphene oxide / graphene dispersion or a graphene oxide / graphene / carbon nanotube dispersion; b) CTAB to the dispersion liquid, chitosan, CaCl _2, NaOH, at least one member selected from the group consisting of KOH first coagulation components, and polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyethylene imine (PEI ), Polyvinylpyrrolidone (PVP), and polyethylene oxide (PEO), to produce a gel fiber; And c) drying the gel fiber to provide a graphene oxide / carbon nanotube conjugated fiber, a graphene oxide / graphene conjugated fiber or a graphene oxide / graphene / carbon nanotube conjugated fiber do.

The content (wt%) ratio of graphene oxide: carbon nanotube in the dispersion is not limited, but is preferably 1: 4 to 4: 1.

The content (wt%) of graphene oxide: graphene in the dispersion is not limited, but is preferably 1: 4 to 4: 1.

The ratio of graphene oxide (graphene + carbon nanotubes) in the dispersion is 1: 4 to 4: 1, although the ratio of graphene to carbon nanotubes is not limited. The graphene: carbon nanotube content (wt% But it is preferably 1: 4 to 4: 1.

In the spinning solution, the total concentration of graphene oxide, graphene, and carbon nanotubes is preferably 0.1 to 2 wt%.

Preferably, the concentration of CTAB in the coagulating bath is 0.03 to 0.1 wt%, the concentration of CaCl ₂ , NaOH, KOH is 3 to 10 wt%, and the concentration of PVA, PMMA, PEI, PVP and PEO is 2 to 40 wt%.

The graphene oxide may be a graphene oxide into which a functional material capable of detecting a target substance is introduced. The functional material may be a nucleic acid, a DNA, an RNA, an extramamer, a peptide, a protein, an antibody, a growth factor, an enzyme, a fluorescent substance, or a minerals.

The surface active agent for dispersing the graphene or carbon nanotube is selected from the group consisting of sodium dodecylbenzenesulfonate (SDBS), sodium dodecylsulfonate (SDS), sodium lignosulfonate (SLS), sodium laurethesulfonate (SLES) An anionic surfactant having a hydrophilic sulfonic acid group (SO ₃ ^- ) of sodium lauryl ether sulfonate (SLES), sodium myreth sulfate, lithium dodecylsulfonate (LDS), or an anionic surfactant having cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), cetylpyridinium chloride (CPC), dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), tetratrimethylammonium bromide (TMB), dioctadecyldimethylammonium (DODAB), dimethyl dioctadecylammonium chloride (DODMAC) cationic surfactants, or Tween 20, 40, 60, 80, Triton X-100, glycerol alkyl esters, Recessed GW a lauryl ester (Glyceryl laurate esters), polyethylene glycol sorbitan alkyl ester nonionic surfactant (Polyoxyethylene glycol sorbitan alkyl esters), polyethylene glycol octadecyl ether may be used.

The dried composite fiber may further include chemical or thermal reduction.

The graphene oxide / carbon nanotube composite fiber, the graphene oxide / graphene composite fiber, or the graphene oxide / graphene / carbon nanotube composite fiber prepared according to the present invention can be used for the electrical conductivity, thermal conductivity And the electrical conductivity and thermal conductivity characteristics of the composite fiber produced according to the content of the graphene oxide and the carbon nanotube (or graphene) exhibit a linear increase curve. Therefore, the desired electrical conductivity, thermal conductivity It is possible to produce a conjugate fiber having a degree of crystallinity.

In addition, the graphene oxide of the present invention is capable of attaching various functional materials such as biomolecules (nucleic acids, platamers, enzymes, etc.) and polymers as compared with graphene and carbon nanotubes, It is possible to manufacture a composite fiber having high electrical conductivity without breaking.

1 is a schematic diagram of a graphene structure showing a process of producing a 'reduced graphene oxide (rGO)' from a graphene oxide (GO) according to a chemical stripping method.
FIG. 2 is a schematic diagram showing wet spinning of graphene oxide (FIG. 2A) and a process of aligning graphene oxide (or graphene, nanocarbon tube) in a wet spinning process (FIG. 2B).
3 is a scanning electron micrograph (SEM) photograph of the graphene oxide / carbon nanotube composite fiber produced according to Example 2 of the present invention, wherein (a) is a cross-sectional photograph and (b) is an enlarged photograph thereof.
FIG. 4 is a graph showing the results of measurement of graphene oxide / carbon nanotube composite fibers prepared according to Examples 1 to 4 of the present invention and graphene oxide fibers prepared according to Comparative Example 3, It is a graph measuring the conductivity.

The present inventors studied wet spinning processes using graphene oxide, graphene, and carbon nanotube dispersions as spinning solutions, and found that the coagulation property of graphene oxide (first coagulation component) and the coagulation property of carbon nanotubes and graphene (Second coagulation component), surprisingly, fibrosis (gelation) is generated to form graphene oxide / carbon nanotube composite fiber, graphene oxide / graphene composite fiber or graphene oxide / graphene / Carbon nanotube conjugated fiber can be effectively produced, thereby completing the present invention.

The method for producing a graft oxide / carbon nanotube conjugated fiber, graphene oxide / graft conjugated fiber, or graphene oxide / graphene / carbon nanotube conjugated fiber according to the present invention comprises:

a) preparing a graphene oxide / carbon nanotube dispersion, a graphene oxide / graphene dispersion or a graphene oxide / graphene / carbon nanotube dispersion; b) mixing the dispersion with at least one first coagulation component selected from the group consisting of CTAB, chitosan, CaCl ₂ , NaOH, KOH and polyvinyl alcohol (PVA), polymethylmethacrylate (PMMA), polyethyleneimine (PEI) Preparing a gel fiber by wet spinning in a coagulation bath containing a second coagulation component selected from the group consisting of polyvinylpyrrolidone (PVP) and polyethylene oxide (PEO); And c) drying the gel fibers.

Graphene oxide (GO)

In the present invention, graphene oxide (GO) is produced by a chemical stripping method.

The graphene oxide is produced by oxidizing graphite using a strong acid to make expanded graphite with oxygen functional groups introduced between the graphene layers and ultrasonic pulverizing or rapid heating in solution.

Staudenmaier and Hamdi disclose a method for producing graphite oxide using a sulfuric acid / nitric acid mixture, but most of the graphene oxides presently are oxidized graphite using a mixture of sodium nitrate / potassium chlorate with fuming sulfuric acid Or by using a Hummers method or a modified method thereof.

The graphene oxide has a structure in which various oxygen functional group groups such as an epoxy group, a hydroxyl group, and a terminal carboxyl group or carbonyl group are formed on the surface or / and the terminal of graphene.

The graphene oxide has an insulator and has low conductivity depending on the degree of oxidation and characteristics, but is extremely small compared to graphene or carbon nanotubes.

The graphene oxide according to the present invention includes graphene oxide to which a functional material is attached. The functional material is, for example, various sensing materials used for the detection of a target substance in the biosensor field. The functional material may be a nucleic acid, a DNA, an RNA, an extramamer, a peptide, a protein, an antibody, a growth factor, an enzyme, a fluorescent substance, a minerals substance, a biomolecule, and a functional polymer. The functional material may be formed by bonding with the functional group of the graphene oxide. When the sensing material binds to or reacts with a target material, it is possible to successfully detect important biomolecules such as specific nucleic acids, proteins, and growth factors by observing an electrical signal or fluorescence (or extinction). The electrical signal according to the functional material is transmitted through the electroconductive material of the composite fiber according to the present invention through the graphene and carbon nanotubes, so that it can provide a high detection power despite the low electrical signal.

Meanwhile, the graphene oxide according to the present invention may include chemically modified graphene oxide. Chemical modification of the graphene oxide can be produced, for example, by reacting organic monomers with an oxygen functional group (epoxy group, hydroxyl group, carboxyl group, etc.) of the graphene oxide. The organic single molecule having an amine group reacts with the epoxy group of the graphene oxide as shown in the following reaction formula to introduce an organic monomolecule into the graphene oxide ( Polymer (Korea), Vol. 35, No. 3, pp 265-271, 2011).

It is reported that graphene oxide functionalized with isocyanate greatly improves the dispersibility in polar solvents (S. Stankovich, R. D. Piner, S. T. Nguyen, and R. S. Ruoff, Carbon, 44, 3342 (2006)).

Since the graphene oxide is polar and hydrophilic due to the oxygen functional group, it is well dispersed in a polar solvent such as water, organic solvent or water / organic solvent.

Examples of the solvent of the graphene oxide include distilled water, dimethylformamide, methanol, ethanol, ethylene glycol, n-butanol, tert -butyl alcohol, isopropyl alcohol, n-propanol, ethyl acetate, dimethyl sulfoxide and tetrahydrofuran Among them, distilled water or distilled water / organic solvent is preferable.

The graphene oxide concentration is preferably 1 to 20 mg / mL (0.1 to 2 wt%) based on the spray solution, but is not limited thereto. In the spinning solution of the present invention, the total concentration of graphene oxide, graphene, and carbon nanotubes is preferably 0.1 to 2 wt%.

Graphene (including rGO)

The graphene according to the present invention can be produced by a mechanical stripping method, a chemical vapor deposition (CVD) method, an epitaxial growth method or a nonoxidative exfoliation method. However, Or a reduced graphene oxide (rGO) produced by chemical reduction is preferably used. As the graphene according to the present invention, chemically converted graphene (CCG) or chemically modified reduction graphene (rCCG) may be used. More preferably, the graphene according to the present invention is a reduced graphene oxide (rGO).

Various methods of heat treatment and chemical reduction treatment in the reduction step are already known. Representative reducing agents of graphene oxide include hydrazine compounds such as hydrazine, sodium hydrazine and hydrazine hydrate, hydroquinone, sodium borohydride (NaBH ₄ ), ascorbic acid, glucose, But the present invention is not limited thereto.

Since graphene (or reduced graphene oxide) has a non-polar or very weak polarity and hydrophobicity, it is dispersed in a solvent using a surfactant. Examples of the surfactant include sodium dodecylbenzenesulfonate (SDBS), sodium dodecylsulfonate (SDS), sodium lignosulfonate (SLS), sodium laureth sulfate (SLES), sodium lauryl ether sulfonate (SLES) (CTAB), cetyltrimethylammonium chloride (CTAC), anionic surfactants having a hydrophilic sulfonic acid group (SO ₃ ^- ) of dodecylsulfonyl lithium (LDS), or anionic surfactants such as cetyltrimethylammonium bromide (CPC), dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), tetratrimethylammonium bromide (TMB), dioctadecyldimethylammonium bromide (DODAB), dimethyl dioctadecylammonium Triton X-100, Glycerol alkyl esters, Glyceryl laurate esters, < RTI ID = 0.0 > Li a glycol sorbitan alkyl ester nonionic surfactant (Polyoxyethylene glycol sorbitan alkyl esters), polyethylene glycol octadecyl ether may be used. Although not limited in the present invention, it is preferable to disperse water by using an anionic surfactant having a hydrophilic sulfonic acid group (SO ₃ ^- ). Ultrasonic processing may be added to effectively disperse the graphene according to the present invention.

The graphene or graphene oxide is present in the form of a sheet, which may be referred to as "graphene flake", "graphene sheet", "graphene crystal". The average diameter of the graphene flakes according to the present invention is preferably several micrometers or more, and the number of graphene or graphene oxide layers is preferably three or less.

The concentration of graphene is preferably 1 to 20 mg / mL (0.1 to 2 wt%), but is not limited thereto. In the spinning solution of the present invention, the total concentration of graphene oxide, graphene, and carbon nanotubes is preferably 0.1 to 2 wt%.

Carbon Nanotube (CNT)

In the present invention, the carbon nanotubes (CNTs) may be single walled carbon nanotubes (SWNTs), double walled carbon nanotubes (DWNTs), multi-walled carbon nanotubes (MWNTs) CNT) is possible, but SWNT is more preferable considering electrical conductivity and mechanical characteristics. CNTs can be produced by a known method such as chemical vapor deposition (CVD), arc discharge, or laser evaporation.

Carbon nanotubes are non-polar and have strong van der Waals forces on CNT sidewalls, so they are not well dissolved or dispersed in polar and organic solvents such as water. Therefore, it is preferable to disperse the CNTs using a surfactant and ultrasonic waves for effective dispersion of the CNTs.

Surfactants for dispersing graphene may be used as the surfactant.

The surfactant concentration is important for CNT dispersion. The lower the concentration of the surfactant, the lower the dispersion stability. If too high, the osmotic pressure causes depletion-induced aggregation. The weight ratio of CNT to surfactant in the dispersion is preferably 1: 2 to 1: 3, but may vary depending on the kind of the surfactant.

The concentration of CNT is preferably from 1 to 30 mg / mL (0.1 to 3 wt%) based on the flushing solution, but not limited thereto. The CNT concentration is more preferably 3 to 20 mg / mL (0.1 to 2 wt%), and most preferably 5 to 10 mg / mL (0.5 to 1.0 wt%). In the spinning solution of the present invention, the total concentration of graphene oxide, graphene, and carbon nanotubes is preferably 0.1 to 2 wt%.

The solvent for the CNT dispersion may be water (distilled water) or water / organic mixture.

The graphene oxide / graphene dispersion, graphene oxide / graphene / carbon nanotube dispersion according to the present invention can be prepared by dispersing the desired graphene oxide, graphene, carbon nanotubes and surfactant in water Or a water / organic solvent and simultaneously dispersing and ultrasonically treating the dispersion. Alternatively, the graphene oxide dispersion, the graphene dispersion, and the carbon nanotube dispersion may be prepared and then mixed with each other.

The graphene / carbon nanotube dispersion may be prepared by dispersing graphene and carbon nanotubes in water or a water / organic solvent using the surfactants described above, and then mixing the graphene / carbon nanotube dispersion with a graphene oxide dispersion .

The dispersion is used as a spinning solution. The concentration of the spinning solution may be made by appropriately diluting the dispersion.

The ratio of graft oxide (GO) to carbon nanotube (CNT) in the graphene oxide / carbon nanotube dispersion is 4: 1 to 1: 4, preferably 3: 2 to 2: 3, more preferably 1: : 1. These component ratios can be calculated by preparing each dispersion for each component and then adjusting the amount of the dispersion to be mixed.

The ratio of graphene oxide (GO) to graphene (rGO) in the graphene oxide / graphene dispersion is in the range of 4: 1 to 1: 4, preferably 3: 2 to 2: 3, more preferably 1: to be.

The ratio of graphene oxide: (carbon nanotube + graphene) in the graphene oxide / graphene / carbon nanotube dispersion is 4: 1 to 1: 4, preferably 3: 2 to 2: 3, Is 1: 1, and the ratio of graphene: carbon nanotubes is 4: 1 to 1: 4, preferably 3: 2 to 2: 3, more preferably 1: 1.

The coagulation bath according to the present invention may comprise at least one first coagulation component selected from the group consisting of CTAB, chitosan, CaCl ₂ , NaOH, KOH, and at least one first solidification component selected from the group consisting of polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA) (PEI), polyvinyl pyrrolidone (PVP), and polyethylene oxide (PEO) at the same time as a coagulating agent.

The first solidification component is known as a coagulation medium of graphene oxide and the second solidification component is known as a coagulation medium of graphene or carbon nanotube. However, in the case where a mixture of the first solidification component and the second solidification component is tried with a coagulation bath There is no.

Among the first coagulation components, CTAB is most widely known as a coagulant of cationic surfactant or graphene oxide. CaCl ₂ is known to be agglomerated by graphene oxides crosslinked by divalent ions (Ca ²⁺ ) ( Adv. Mater. 2013, 25, 188.). NaOH and KOH are known to cause aggregation through reduction of graphene oxide as a reducing agent ( Nat. Comm. 2011, 2, 571.). Chitosan is known to aggregate graphene oxide by polyelectrolyte complexation ( Adv. Func. Mater . 2013, 23, 5345.)

The nano carbon tubes of the second solidification component, the coagulation bath of graphene, are known in various literatures. Vigolo et al. Prepared a 0.35 wt% SWNT dispersion using a surfactant (1.0 wt% sodium dodecylsulfonate (SDS)) and then spinning it in a 5 wt% polyvinyl alcohol (PVA) / distilled water coagulating bath to first produce carbon nanotube fibers (Vigolo, B. et al., Macroscopic fibers and ribbons of oriented carbon nanotubes, Science 290, 1331-1334 (2000)).

Munoz et al. Prepared SWNT dispersions using cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), and lithium dodecylsulfonate (LDS) surfactants and then dissolved in a polyethyleneimine (PEI) / distilled water coagulation bath (SWNT / PEI) fibers were prepared by spinning ( Adv. Mater . 2005, 17, No. 8, April 18). It was confirmed that the prepared SWNT / PEI fiber had a 100 times increase in electrical conductivity compared to the SWNT / PVA composite fiber.

Winey et al. (Winey et al., Macromolecules , 2004, 37, 9048) disclose a method for producing a CNT composite film using polymethyl methacrylate (PMMA) as a coagulating agent.

Smalley et al. Disclosed a method for producing a CNT composite film using PVA / PVP as a coagulating agent.

The first solidifying component and the second solidifying component are water-soluble, and the solidifying bath of the present invention can be produced by dissolving the first solidifying component and the second solidifying component in distilled water. Examples of the solvent for the coagulating bath include organic solvents such as dimethylformamide, methanol, ethanol, ethylene glycol, n-butanol, tert-butyl alcohol, isopropyl alcohol, n-propanol, ethyl acetate, dimethyl sulfoxide and tetrahydrofuran Can be used. In the present invention, distilled water is preferably used as an emulsifying solvent, but the present invention is not limited thereto.

The coagulating liquid concentration of the first coagulation component and the second coagulation component may be used at a known coagulation bath concentration (content wt%) in a conventional wet spinning process of graphene oxide, graphene, and carbon nanotubes.

For example, the concentration of CTAB in the coagulating bath is 0.03 to 0.1 wt%, preferably 0.05 wt% (0.5 mg / mL), and CaCl ₂ , NaOH, KOH are 3 to 10 wt%, PVA, PMMA, PEI, PVP, PEO is 2 to 40 wt%, preferably 5 to 10 wt%, but is not limited thereto.

The content of the first solidification component and the second solidification component of the coagulation bath may vary depending on the ratio of the graphene oxide, graphene and carbon nanotubes in the spinning solution. If the content of graphene oxide in the spinning solution is high, the content of the first solidification component in the coagulation bath may increase, and if the content of graphene and carbon nanotubes is high, the content of the second coagulation component in the coagulation bath is preferably increased.

Wherein the graphene oxide / carbon nanotube dispersion, the graphene oxide / graphene dispersion, and the graphene oxide / graphene / carbon nanotube dispersion are mixed in a coagulation bath containing only the first coagulation component, Fibrosis (gelling) does not occur and fibers are not formed, whereas fibrosis occurs in the coagulation bath containing the first and second coagulation components.

According to the present invention, the content of graphene oxide / carbon nanotube conjugated fiber, graphene oxide / graphene conjugated fiber, graphene oxide / graphene / carbon nanotube conjugate fiber content of graphene oxide: (graphene + carbon nanotube) It was confirmed that the electric conductivity of the composite fibers varies greatly according to the ratio. In the present invention, the higher the content of graphene oxide, the lower the electrical conductivity of the composite fibers. The lower the content of graphene oxide, the higher the electrical conductivity of the composite fibers.

The composite fiber according to the present invention has electric conduction characteristics without a separate graphene oxide reduction process. Therefore, when a graphene oxide into which a functional material such as nucleic acid, DNA, RNA, or aptamer is introduced is used, these functional materials are not destroyed or decomposed by a chemical or thermal reduction process, do.

However, when the graphene oxide of the present invention does not contain a functional material, the composite fiber of the present invention may undergo a further reduction process through a known thermal or chemical reduction method. The thermal reduction method is not limited, but may be performed at a temperature of 200 to 1000 ° C at a room temperature and at a rate of 0.1 to 10 ° C / minute. The chemical reduction method may be carried out by using a known reducing agent such as hydrazine, hydroiodic acid, hydrobromic acid, sodium borohydride, lithium aluminum hydride and sulfuric acid. .

Hereinafter, a method for producing a graft oxide / carbon nanotube conjugated fiber, a grafted oxide / graft conjugated fiber or a grafted oxide / graft / carbon nanotube conjugated fiber according to the present invention will be described in detail with reference to the following examples.

Material preparation

Preparation of graphene oxide (GO) dispersion

2.4 g of graphite flake was placed in 10 mL of sulfuric acid dissolved in 2.0 g of potassium persulfate and 2.0 g of phosphorus pentoxide and reacted at 80 DEG C for 72 hours. The graphite was diluted and then obtained by vacuum filtration, and then expanded at room temperature in vacuum for 24 hours to obtain expanded graphite. The obtained expanded graphite was dispersed in 92 mL of sulfuric acid. Then, 12.0 g of potassium permanganate was dissolved and reacted at 35 DEG C for 2 hours and 30 minutes. Then, 1.0 L of distilled water was added for 30 minutes so that the temperature of the total dispersion did not exceed 45 DEG C, The reaction was terminated by adding 20 mL of 30% aqueous hydrogen peroxide. The reaction mixture was centrifuged at a speed of 10,000 rpm for 10 minutes and then centrifuged at a rate of 13,000 rpm for 40 minutes. Times, and dried to obtain a graphene oxide. 1 g of the obtained graphene oxide was dissolved in 200 mL of distilled water and dissolved to obtain a 0.5 wt% GO water dispersion.

Preparation of graphene (rGO) dispersions

The graphene oxide aqueous dispersion was prepared as described above, and an excessive amount of hydrazine was added thereto, followed by reduction at 80 DEG C for 2 hours to obtain agglomerated graphene. Concentrated sulfuric acid was added to the coagulated graphene, which was reacted at 180 ° C for 12 hours to reduce, washed, and dried to obtain reduced graphene oxide (rGO). 0.5 g of the obtained rGO and 0.25 g of sodium dodecylbenzenesulfonate (SDBS) were added to 100 mL of distilled water and ultrasonicated for 30 minutes to prepare a 0.5 wt% rGO aqueous dispersion.

Manufacture of carbon nanotube (SWNT) dispersion

0.5 g of SWNT and 0.25 g of surfactant SDBS were added to 100 ml of distilled water and ultrasonicated for 30 minutes to prepare a 0.5 wt% SWNT water dispersion.

Coagulation preparation

The CTAB coagulating solution, the PVA coagulating solution and the CaCl ₂ coagulating solution were respectively prepared and then mixed to prepare a mixed coagulating solution of CTAB / PVA and CaCl ₂ / PVA. In consideration of the fact that the content of distilled water increases as the amount of distilled water decreases, 0.10wt% CTAB, 10wt% PVA and 10wt% CaCl ₂ content were prepared and mixed in a coagulating bath.

2 g of CTAB was added to 2 L of distilled water and dissolved to prepare a 0.10 wt% CTAB coagulated solution.

222 g of PVA was added to 2 L of distilled water and dissolved to prepare a 10 wt% PVA coagulation solution.

222 g of CaCl ₂ was added to ₂ L of distilled water and dissolved to prepare a 10 wt% CaCl ₂ coagulated solution.

Examples 1 to 4: Preparation of graphene oxide / carbon nanotube conjugate fiber using CTAB / PVA coagulating bath

As shown in the following Table 1, the prepared 0.5 wt% GO water dispersion and 0.5 wt% SWNT water dispersion were mixed with GO: SWNT = 4: 1, 3: 2, 2: / SWNT water dispersion was prepared and used as spinning solution.

As shown in the following Table 1, a CTAB / PVA coagulating bath was prepared by mixing the prepared 0.10 wt% CTAB coagulating solution and 10 wt% PVA coagulating solution.

Each of the prepared GO / SWNT dispersions was put into a 5 mL syringe and rotated or linearly sprayed onto the prepared CTAB / PVA coagulation bath while maintaining a spinning rate of 1 mL / min or less through a 0.3 mm diameter spinneret To prepare a gel-like fiber. Thirty minutes after the spinning solution injection, the gel-type fibers were temporarily moved to distilled water to remove the remaining coagulation bath and dried at room temperature for 24 hours to prepare a graphene oxide / carbon nanotube composite fiber.

The dispersion component (in water) Coagulation bath component (in water) fiber 0.5wt% GO 0.5 wt% SWNT 0.10 wt% CTAB 10 wt% PVA Example 1 8 mL 2 mL 600 mL 400 mL ○ Example 2 6 mL 4 mL 600 mL 400 mL ○ Example 3 4 mL 6 mL 400 mL 600 mL ○ Example 4 2 mL 8 mL 400 mL 600 mL ○

Comparative Examples 1 to 4: Preparation of graphene oxide fibers and carbon nanotube fibers

The GO / SWNT water dispersion was prepared by mixing the prepared 0.5 wt% GO water dispersion and 0.5 wt% SWNT water dispersion at a ratio of 1: 1 as shown in the following Table 2, and then the CTAB coagulation bath (Comparative Example 1) PVA coagulation bath (Comparative Example 2). As a result of the spinning, fibrosis (gelation) was not generated in the coagulation bath, so that it could not be made into fibers.

A fiber dispersion was prepared by spinning a 0.5 wt% GO water dispersion as a control, a CTAB coagulating bath (Comparative Example 3), and a 0.5 wt% SWNT aqueous dispersion to a PVA coagulation bath (Comparative Example 4).

The dispersion component (in water) Coagulation bath component (in water) fiber 0.5wt% GO 0.5 wt% SWNT 0.10 wt% CTAB 10 wt% PVA Comparative Example 1 5 mL 5 mL 1000 mL - ㅧ Comparative Example 2 5 mL 5 mL - 1000 mL ㅧ Comparative Example 3 10 mL - 1000 mL - ○ (GO fibers) Comparative Example 4 - 10 mL - 1000 mL ○ (SWNT fibers)

Examples 5 to 8: CaCl 2 ₂ / Preparation of graphene oxide / graphene conjugate fiber by PVA coagulation bath

As shown in the following Table 3, the prepared 0.5 wt% GO aqueous dispersion and 0.5 wt% rGO aqueous dispersion were mixed with GO: rGO = 4: 1, 3: 2, 2: / rGO aqueous dispersion was prepared and used as spinning solution.

As shown in the following Table 3, each CaCl ₂ / PVA coagulating bath was prepared by mixing the 10 wt% CaCl ₂ coagulating solution and the 10 wt% PVA coagulating solution prepared above.

Wet spinning was carried out in the same manner as in Example 1 to prepare a graphene oxide / graphene conjugated fiber.

The dispersion component (in water) Coagulation bath component (in water) fiber 0.5wt% GO 0.5 wt% rGO 10 wt% CaCl ₂ 10 wt% PVA Example 5 8 mL 2 mL 600 mL 400 mL ○ Example 6 6 mL 4 mL 600 mL 400 mL ○ Example 7 4 mL 6 mL 400 mL 600 mL ○ Example 8 2 mL 8 mL 400 mL 600 mL ○

Comparative Examples 5 to 8: Preparation of graphene oxide fibers and carbon nanotube fibers

As shown in the following Table 4, the GO / rGO aqueous dispersion was prepared by mixing the prepared 0.5 wt% aqueous GO dispersion and 0.5 wt% rGO aqueous dispersion at a ratio of 1: 1, and then the CaCl ₂ coagulation bath (Comparative Example 5 ), And a PVA coagulation bath (Comparative Example 6). As a result of the spinning, fibrosis (gelation) was not generated in the coagulation bath, so that it could not be made into fibers.

As a control, a 0.5 wt% GO water dispersion was spun into a CaCl ₂ coagulation bath (Comparative Example 3) and a 0.5 wt% SWNT aqueous dispersion to a PVA coagulation bath (Comparative Example 4) to prepare fibers.

The dispersion component (in water) Coagulation bath component (in water) fiber 0.5wt% GO 0.5 wt% rGO 10 wt% CaCl ₂ 10 wt% PVA Comparative Example 5 5 mL 5 mL 1000 mL - ㅧ Comparative Example 6 5 mL 5 mL - 1000 mL ㅧ Comparative Example 7 10 mL - 1000 mL - ○ (GO fibers) Comparative Example 8 - 10 mL - 1000 mL ○ (rGO fibers)

Examples 9 to 12: Preparation of graphene oxide / graphene / carbon nanotube conjugate fiber

As shown in the following Table 5, the prepared 0.5 wt% GO water dispersion, 0.5 wt% rGO aqueous dispersion and 0.5 wt% SWNT aqueous dispersion were mixed with GO: rGO: SWNT = 8: 1: 1, 6: 2: 2 , 4: 3: 3, and 2: 4: 4, respectively, to prepare GO / rGO / SWNT water dispersion.

Each of the CTAB / PVA coagulating baths was prepared by mixing the prepared 0.10 wt% CTAB coagulation bath and the 5 wt% PVA coagulation bath as shown in Table 5 below.

Wet spinning was carried out in the same manner as in Example 1 to prepare a graphene oxide / graphene / carbon nanotube composite fiber.

The dispersion component (in water) Coagulation bath component (in water) fiber 0.5wt% GO 0.5 wt% SWNT 0.5 wt% rGO 0.10 wt% CTAB 10 wt% PVA Example 9 8 mL 1 mL 1 mL 600 mL 400 mL ○ Example 10 6 mL 2 mL 2 mL 600 mL 400 mL ○ Example 11 4 mL 3 mL 3 mL 400 mL 600 mL ○ Example 12 2 mL 4 mL 4 mL 400 mL 600 mL ○

Experimental Example 1: Morphology of graphene oxide / carbon nanotube composite fiber

The graphene oxide / carbon nanotube fibers prepared according to Example 2 were photographed by scanning electron microscope (SEM) and the results are shown in FIG.

3 (a) is a cross-sectional photograph of the graphene oxide / carbon nanotube fiber, and Fig. 3 (b) is an enlarged photograph thereof.

As shown in FIG. 3 (b), it can be confirmed that the graphene oxide and the carbon nanotube are uniformly bonded to each other without causing agglomeration.

Experimental Example 2: Electrical Conductivity Analysis of Graphene Oxide / Carbon Nanotube Composite Fiber

The electrical conductivity characteristics of the graphene oxide / carbon nanotube composite fiber prepared according to Examples 1 to 4 and the carbon nanotube fiber prepared according to Comparative Example 3 and the graphene oxide fiber prepared according to Comparative Example 4 were measured 4.

As shown in FIG. 4, the graphene oxide fibers of Comparative Example 3 exhibited electric conductivities close to that of an insulator of ~ 10 ^-3 S / m due to the insulating properties of graphene oxide, while the composite fibers of Example 1 The composite fiber of Example 2 (graphene oxide: carbon nanotube = 3: 2) was about 10 S / m, and the composite fiber of Example 3 (carbon nanotube = 4: graphene oxide: CNT = 3: 2) and 10 ² composite fiber of the S / m, example 4 (graphene oxide: CNT = 1: 4) 10 ⁴ CNT in S / m It was confirmed that the electrical conductivity was also significantly increased with the increase of the content.

Claims (10)

a) preparing a graphene oxide / carbon nanotube dispersion, a graphene oxide / graphene dispersion or a graphene oxide / graphene / carbon nanotube dispersion;
b) CTAB to the dispersion liquid, chitosan, CaCl _2, NaOH, at least one member selected from the group consisting of KOH first coagulation components, and polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyethylene imine (PEI ), Polyvinylpyrrolidone (PVP), and polyethylene oxide (PEO), to produce a gel fiber; And
c) drying said gel fibers.
A method for producing graphene oxide composite fibers.
The method according to claim 1,
Wherein the content of graphene oxide: carbon nanotubes (wt%) in the dispersion is 1: 4 to 4: 1.
A method for producing graphene oxide composite fibers.
The method according to claim 1,
Characterized in that the content (wt%) of graphene oxide: graphene in the dispersion is 1: 4 to 4: 1.
A method for producing graphene oxide composite fibers.
The method according to claim 1,
The ratio of graphene oxide: (graphene + carbon nanotubes) in the dispersion is 1: 4 to 4: 1, and the content of graphene: carbon nanotubes is 1: 4 to 4: 4: 1. ≪ RTI ID = 0.0 >
A method for producing graphene oxide composite fibers.
The method according to claim 1,
The total concentration of graphene oxide / carbon nanotubes in the graphene oxide / carbon nanotube dispersion is 0.1 to 2 wt%, the total concentration of graphene oxide / graphene in the graphene oxide / graphene dispersion is 0.1 to 2 wt% / Graphene / the total concentration of graphene oxide / graphene / carbon nanotube in the carbon nanotube dispersion is 0.1 to 2 wt%
A method for producing graphene oxide composite fibers.
The method according to claim 1,
Wherein the CTAB concentration in the coagulation bath is 0.03 to 0.1 wt%, the concentration of CaCl ₂ , NaOH, and KOH is 3 to 10 wt%, and the concentration of PVA, PMMA, PEI, PVP, and PEO is 2 to 40 wt%
A method for producing graphene oxide composite fibers.
The method according to claim 1,
Wherein the graphene oxide is a graphene oxide into which a functional material capable of detecting a target substance is introduced.
A method for producing graphene oxide composite fibers.
8. The method of claim 7,
Wherein the functional material is selected from the group consisting of a nucleic acid, DNA, RNA, an extramamer, a peptide, a protein, an antibody, a growth factor, an enzyme, a fluorescent substance,
A method for producing graphene oxide composite fibers.
The method according to claim 1,
The surface active agent for dispersing the graphene or carbon nanotube is selected from the group consisting of sodium dodecylbenzenesulfonate (SDBS), sodium dodecylsulfonate (SDS), sodium lignosulfonate (SLS), sodium laurethesulfonate (SLES) An anionic surfactant having a hydrophilic sulfonic acid group (SO ₃ ^- ) of sodium lauryl ether sulfonate (SLES), sodium myreth sulfate, lithium dodecylsulfonate (LDS), or an anionic surfactant having cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), cetylpyridinium chloride (CPC), dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), tetratrimethylammonium bromide (TMB), dioctadecyldimethylammonium (DODAB), dimethyl dioctadecylammonium chloride (DODMAC) cationic surfactants, or Tween 20, 40, 60, 80, Triton X-100, glycerol alkyl esters, The recess GW will lauryl ester (Glyceryl laurate esters), polyethylene glycol sorbitan alkyl ester (Polyoxyethylene glycol sorbitan alkyl esters), polyethylene glycol is selected from the group consisting of non-ionic surfactants of octadecyl ether,
A method for producing graphene oxide composite fibers.
The method according to claim 1,
Further comprising the step of chemically or thermally reducing the dried composite fiber.
A method for producing graphene oxide composite fibers.

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