KR100572673B1 - Fat-soluble ferrofluids, preparation method and use thereof - Google Patents

Abstract

The present invention relates to a fat-soluble ferrofluid that is stably dispersed in an organic solvent without excessive surfactant by treating the surface of magnetic nanoparticles with an ionic organic compound. The fat-soluble ferrofluid can be adjusted to have various solubilities in various solvents by combining useful organic substituents on ionic organic compounds on the surface, and by using such a solubility, it is possible to mix with various substances, thus making the magnetic nanoparticles as general It can be used as a compound to prepare a mixture or hybrid complex with various kinds of materials. Furthermore, after inducing various chemical reactions through substituents on these surfaces, magnetic nanoparticles can be easily separated by an external magnetic field and used as a support for separating, purifying, recovering and reusing specific components. The polymer may be prepared using the ionic organic compound on the surface, and an organic / inorganic composite thin film may be prepared.

Magnetic nanoparticles, fat soluble ferrofluids, nano supports, separation, purification, recycling, thin films.

Description

Fat-Soluble Ferrofluids, Method of Producing and Use thereof {Organic-Soluble Ferrofluids, Method of Producing Theirof and Their Applications}

1 is XRD data of cobalt ferrite magnetic nanoparticles.

FIG. 2 is a transmission electron micrograph of cobalt ferrite magnetic nanoparticles surface treated with EDC. FIG.

3 is a comparison of amide bond production yield change with time of Boc-phe and dimethylaniline.

4 is a transmission electron micrograph (magnitude bar: 5 nm) of magnetic nanoparticles covered with polystyrene shell.

FIG. 5 is an electron microscope picture of a hybrid composite thin film prepared from magnetic nanoparticles and polystyrene (magnification 3,500 times, size bar: 500 nm).

6 is a summary diagram of treating the surface of the magnetic nanoparticles with various materials.

The present invention relates to a fat-soluble ferrofluid, a method and a use of the fat-soluble ferrofluid. Ferrofluid refers to a material that exhibits properties such as a liquid magnet having magnetic properties as well as fluid because magnetic nanoparticles are uniformly dispersed in a solvent.

Ferrofluid solves the problem that the magnetic properties are lost due to the disordered orientation of the single electrons that cause magnetism when the solid solid material is melted. As a result, the ferrofluid cannot be a liquid magnet. Aqueous ferrofluid solutions are widely used in applications such as high vacuum connections, magnetic valves that control the flow of fluids, and expensive speakers.

In the case of water-soluble ferrofluids, the magnetic nanoparticles do not clump and disperse in water because the electrostatic repulsion between many ionic charges occurring at the metal atoms on the surface of the nanoparticle that is not fully bonded is stronger than the magnetic attraction between the magnetic nanoparticles. It uses the principle that it can be.

However, the development of such liquid magnetic materials in organic solutions has not been successful. In order to dissolve in an organic solvent, a surfactant material having a long alkyl functional group such as stearic acid (or octadecanoic acid, CH ₃ (CH ₂ ) ₁₆ CO ₂ H) is usually treated with a carboxyl functional group by treating the surface of the magnetic nanoparticles. use a method for the reaction with the surface of the nanoparticles, and the long alkyl chain of the hydrophobic to be distributed to as many presence on the outside of the needle-like sticker serves as the non-polar organic solvent such as hexane ^- (-CO _2). That is, the carboxyl functional groups of the surfactant material, such as stearic acid (-CO ₂ ^-) are coupled to the surface of the nanoparticles, are dispersed in an organic solvent by a long alkyl chain. In this case, however, the presence of excess surfactant material is stable for a long time. Carboxyl functional group is a surfactant material having an ionic side outermost yirumyeonseo a so-called double layer (bilayer) structure in which the organic acid layer made of another on a floor by the van der Waals attraction between the excess present in the alkyl chain (-CO ₂ ^- ), G. Markvich, T. Fried, G. Shemer, Adv. Mater., 2001, 13 , 1158; L. shen, A. Stachowiak, TA Hatton , PE Laibinis, Langmuir 2000, 16, 9907] of ionic carboxyl functional groups (-CO ₂ ^-) magnetic attraction between the magnetic material of the nanoparticles by the electrostatic repulsion between the Offset to some extent and the magnetic nanoparticles are in aqueous or organic solution. It will exist in a stable state.

However, when the excess organic acid material is removed or the concentration is diminished and the double layer structure is broken, the ionic repulsive force disappears, and the magnetic nanoparticles aggregate together to form a precipitate. Therefore, there are few examples of the magnetic nanoparticle solution showing very long stability without an additive such as an excess of surfactant in the organic solvent.

On the other hand, the present inventors have conducted a nano-support research showing a recyclable catalytic action with excellent stability without excessive surfactant by immobilizing the ionic organometallic catalyst on the surface of the magnetic nanoparticles [Reference: T.-J . Yoon, W. Lee, Y.-S. Oh, J.-K. Lee New J. Chem., 2003, 27 , 227].

Accordingly, the present inventors have tried to provide a fat-soluble ferrofluid that is stably dispersed in an organic solvent without an excessive amount of surfactant and a method for preparing the fat-soluble ferrofluid that is stable in an organic solvent. As a result, the present invention was completed.

That is, a first object of the present invention is to provide a fat-soluble ferrofluid having a long-term stability regardless of the concentration even without an excess of surfactant, the second object of the present invention is to develop the use of the fat-soluble ferrofluid.

In order to achieve the above object, it was found that when the surface of the magnetic nanoparticles was treated with an ionic organic compound, a fat-soluble ferrofluid that was stably dispersed in an organic solvent for a long time without an excessive surfactant was prepared. In addition, the fat-soluble ferrofluid that is stable in the organic solvent can be utilized in various chemical reactions, particularly by appropriately selecting the type of ionic organic compound, which is a surface treatment material used in the preparation of the fat-soluble ferrofluid. Revealed.

Therefore, the present invention relates to a method for producing a fat-soluble ferrofluid that is stably dispersed in an organic solvent without an excessive surfactant by treating the surface of the magnetic nanoparticles with an ionic organic compound, the ionic organic compound is preferably ammonium cation It relates to a compound comprising, more preferably a method for producing a fat-soluble ferrofluid characterized in that the nitrilotriacetic acid derivative.

The present invention also relates to a fat-soluble ferrofluid obtained by treating the surface of nanoparticles with an ionic organic compound.

The invention also relates to the use of said fat soluble ferrofluid in chemical reactions. Particularly, in chemical reaction, magnetic nanoparticles of fat-soluble ferrofluid are used as a support, chemical reaction is performed using an ionic organic compound bound thereto, and the reaction by-product or product is separated and / or purified using an external magnetic force. It is about a method. It also relates to a process wherein the chemical reaction is an amide synthesis reaction and the ionic organic compound comprises a carbodiimide functional group.

The present invention also relates to a method for synthesizing polymers using fat-soluble ferrofluids treated with ionic organic compounds.

The present invention also relates to a method for producing an organic / inorganic hybrid composite thin film using a fat-soluble ferrofluid treated with an ionic organic compound.

Hereinafter, the present invention will be described in detail.

The present invention relates to a fat-soluble ferrofluid that is stably dispersed in an organic solvent without an excessive surfactant by treating the surface of the magnetic nanoparticles with an ionic organic compound. The magnetic nanoparticles are not particularly limited in kind. The metal ferrite of the general formula MFe ₂ O ₄ It can be used. These metal ferrites are inherently magnetic and therefore are suitable for use in the present invention. At this time, the metal (M) included in the metal ferrite is not particularly limited, but preferably one or two selected from the group consisting of Co, Mn, Fe, Ni, Cu, Zn, Mg, Cd, Ba, and Sr. It may be a metal or more. In addition, in consideration of the dispersibility in the solution, the size of the magnetic nanoparticles is preferably as small as 1-300nm.

The magnetic nanoparticles described above are generally produced by coprecipitation in a basic solution, and the cobalt ferrite magnetic nanoparticles used in the present invention were prepared by the methods described in the following references [D. Zins, V. Cabuil, R. Massart, J. Mol. Liq ., 1999, 83 , 217. The chemical composition of the synthesized cobalt ferrite magnetic nanoparticles was characterized by inductive coupled plasma atomic emission spectroscopy (ICP-AES, Shimazu / ICPS-1000IV) and surface composition analysis (Electron Probe Micro Analysis, EPMA, WDS mode). , JEOL / JXA-8900R) showed that it was a (CoFe ₂ O ₄ ) _core (Fe _0.19 O _x ) _shell . This nonstoichiometric composition is attributed to the inner core of MFe ₂ O ₄ , a typical spinel ferrite structure, and the stable amorphous ferric hydroxide (FeO (OH)) layer present on the surface. do. The crystallographic properties of the synthesized cobalt ferrite magnetic nanoparticles were also confirmed to be spinel structures through X-ray diffraction (X-ray diffraction, Phillips 3710). Represented by. In addition, in the magnetic properties investigation of the synthesized cobalt ferrite it was confirmed that the saturation magnetic force value at room temperature is about M _s = ~ 60 emu / g through VSM (Vibration Sample Magnetometer, Lake Shore Model 7304).

On the other hand to form when the composition of cobalt ferrite magnetic material nanoparticles, the surface of the synthetic ferro fluid is failing to fully bond FeO (OH) is present and which reacts with the acid FeO (OH ₂ ⁺⁾ or OFe ^+, in the present invention, this position A fat-soluble cobalt ferrite that is stable to an organic solvent by treating the surface of the water-soluble cobalt ferrite magnetic nanoparticles with an ionic organic compound of the following [Formula 1] containing a carboxyl group capable of binding to and having an ionic functional group, preferably an ammonium group at the other end thereof. Magnetic nanoparticles are synthesized.

[Formula 1] Ammonium molecule having carboxyl group and containing ionic functional group.

R ₁ = single bond, C _1-10 straight or branched chain alkylene, substituted C _1-10 straight or branched chain alkylene, arylene, substituted arylene

R ₂ , R ₃ = CH ₃ , CH ₂ CH ₃ , or R ₁ -CO ₂ H

R ₄ = functional groups through various chemical bonds

The solubility of the surface-treated cobalt ferrite magnetic nanoparticles while changing the type of R ₄ in the organic solvent is shown in Table 1 below.

TABLE 1 Various Dispersibility of Surface Treated Magnetic Nanoparticles

R ₄ Soluble solvent Insoluble solvent (CH ₂ ) ₁₁ CH ₃ (long alkyl chain substituent) Hexane Acetone, Tetrahydropurine (THF), Alcohol, Water CH ₂ C (O) C ₁₆ H ₉ (pyrene substituent) Benzene, toluene Acetone or higher polar solvent CH ₂ CH ₂ OH (Polar substituent) Water, alcohol Non-polar solvents such as acetone, tetrahydropurine, hexane, benzene

Hereinafter, the application of the surface-treated fat-soluble ferrofluid to the chemical reaction will be described.

There are many useful organic chemical reactions due to the difficulty in purifying the reaction byproducts produced together. Recently, the reaction products of such problematic reactions are immobilized on the surface of the solid support and reacted easily. Research is actively underway to remove byproducts from reaction products [Ref. FZ Dowald, Organic Synthesis on Solid Phase; Supports, Linkers, Recations, 2 ^nd Ed., Wiley-VCH, 2002].

A representative example is the amide bond reaction formed by the condensation reaction of an acid and an amine. The amide bond is a basic skeleton of a protein, which is the basis of living organisms, and is the most important bond in biochemical and organic chemistry. However, dicyclohexylcarbodiimide (DCC) or 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide (1- (3-) can be used to effectively form amide bonds directly through condensation reactions from organic acids and amines. Carbodiimide auxiliaries, such as dimethylaminopropyl) -3-ethylcarbodiimide (EDC), must be added at a chemical equivalent or higher, which leads to the difficulty of separation / purification because by-products such as urea are always formed in addition to amide-bonded products. [Scheme 1].

Carbodiimide which induces amide bond in reaction of acid and amine

In this regard, the Frindkin group proposed a method of removing the support by filtration after amide synthesis using a carbodiimide derivative supported on a polystyrene solid [M. Frindkin, A. Patchornik, E. Katchalski, Peptides, Proc. Eur. Symp., 10 ^th , 1969, 166; Argonaut Technologies, http://www.argotech.com], because the support is heterogeneously mixed in the reaction solvent from tens to hundreds of micrometers, and the organic reaction proceeds, the reaction rate is very slow. Many problems have been proposed, such as the complexity and the high price of synthetic materials for single use purposes.

In contrast, in the present invention, the magnetic nanoparticles are uniformly and stably dispersed in an organic solvent by using a fat-soluble ferrofluid containing an ionic organic compound containing a carbodiimide group represented by [Formula 2] on the surface of the magnetic nanoparticles. It can efficiently generate an organic reaction, and by using the magnetic properties of the magnetic nanoparticles are easily removed by-products after the reaction.

[Formula 2] Ionic Organic Compounds Including Carbodiimide

R ₁ = single bond, C _1-10 straight or branched chain alkylene, substituted C _1-10 straight or branched chain alkylene, arylene, substituted arylene

R ₂ , R ₃ = CH ₃ , CH ₂ CH ₃ , or R ₁ -CO ₂ H

In addition, the use of a fat-soluble ferrofluid surface-treated with the ionic organic compound of the present invention can efficiently produce a polymer.

Recently, attention has been focused on nanoparticles having a thin shell for various electrical and biomedical applications. As an example, studies have been made to form polymer shells on the surface of silica or gold nanoparticles [KJ Watson, J. Zhu, ST Nguyen, CA Mirkin, J. Am. Chem. Soc., 1999, 121, 462; T. Von Werne, TE Patten, J. Am. Chem. Soc., 1999, 121 , 7409]. In addition, research has been conducted to form polymer shells on the surface of magnetic nanoparticles, which is essential for magnetic targeting drug delivery or magnetic resonance images. However, the polymer-coated magnetic material formed by recent methods is limited to in vivo applications at the micrometer level.

In order to overcome this drawback, the synthesis of polystyrene shell-covered magnetic nanoparticles using atomic transfer radical polymerization (ATRP) has recently been made by Zhang Group [J. Am. Chem. Soc., 2002, 124, 14321]. However, this method also has its limitations. When reacting with the magnetic nanoparticles and the polymer monomer, the reaction proceeds in a non-uniform form to reduce the efficiency of forming the entire shell.

In the present invention, by introducing an ionic organic compound, preferably an organic compound containing an ionic ammonium group on the surface of the magnetic nanoparticles to be stably dispersed in an organic solvent, using this as an initiator, by adding a monomer ATRP The polymer was synthesized by

A schematic diagram of polystyrene polymer production using a styrene monomer is shown in [Scheme 2], and if the monomers are different, various polymers including polyethyleneglycol, polymethylmethacrylate and block copolymers thereof may be prepared. can do.

The polystyrene polymer is prepared from the surface of magnetic nanoparticles treated with an atomic transfer radical polymerization (ATRP) initiator.

In addition, using the surface-treated fat-soluble ferrofluid of the present invention it can be produced an organic / inorganic nanocomposite.

Existing water-soluble ferrofluids have been studied for their good stability and excellent magnetic properties, but organic solvents for magnetic data storage media, magnetic field shielding materials, biomedical applications, etc. Had to be dispersed, and in recent years, trials using surfactant molecules are ongoing. However, this method has a serious problem that it is difficult to quantitatively control the density of the magnetic nanoparticles because the excess organic surfactant material must be present as described above, and the film quality is degraded by the excess organic material.

In the present invention, it has been found that a method of stably dispersing in the organic solvent by treating the surface of the magnetic nanoparticles with an ionic organic compound, preferably an organic compound having ammonium ions, is useful for synthesizing such a composite.

 That is, magnetic nanoparticles whose surface is treated with ionic organic compounds including pyrene derivatives can be uniformly mixed with organic polymers such as polystyrene, and more particularly with spin-coating. Magnetic nanoparticles / polymer composite thin films can be easily produced. In addition, the magnetic density in the thin film can be changed by controlling the ratio of the magnetic nanoparticles and the polymer quantitatively.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are only for illustrating the present invention, the scope of the present invention is not limited to these examples.

EXAMPLE

Example 1-1 Preparation of Ferrofluid for Nonpolar Organic Solvents

Nitrilotriacetic acid (NTA, 0.76 g, 4.0 mmol) having three binding carboxyl functional groups was dissolved in 100 mL dimethylformamide (DMF) solvent, 1-bromododecance (CH ₃ ( CH ₂ ) ₁₀ CH ₂ Br, 1.44 mL, 6.0 mmol) to give (HO ₂ CCH ₂ ) ₃ (H ₃ C (H ₂ C) ₁₁ ) N ⁺ Br ⁻ (1.41 g, 80%). Cobalt ferrite magnetic material nanoparticles 0.3 g was dissolved in DMF 20 mL, and then an excess of _{(HO 2 CCH 2) 3 (} H 3 C (H 2 C) 11) N + Br - and then mixed with (1.41 g, 3.2 mmol) 3 sigan Stir well while. As the surface was treated, precipitation formed from the reaction vessel, which was allowed to settle by centrifugation and the excess organics were washed off with DMF. And hexane was taken and dispersed.

Example 1-2 Preparation of Ferrofluid for Polar Organic Solvents

NTA (0.382 g, 2.0 mmol) was reacted with 2-bromoethanol (BrCH ₂ CH ₂ OH, 0.18 mL, 2.5 mmol) in 50 mL DMF solvent to give (HO ₂ CCH ₂ ) ₃ (HOCH ₂ CH ₂ ) N ⁺ Br ^- was obtained (0.54 g, 90%). Cobalt ferrite magnetic material nanoparticles 0.1 g was dissolved in DMF 10 mL, and then an excess of _{(HO 2 CCH 2) 3 (} HOCH 2 CH 2) N + Br - and then a mixture of (0.54 g, 1.8 mmol) was stirred well for 3 h. Even if the reaction proceeds, the acetone (DMF: acetone = 1: 2, volume ratio) was added to precipitate in the centrifuge because it is dispersed in DMF. Excess organics were washed off with acetone and added with water or alcohol to take up the dispersion.

Example 1-3 Preparation of Ferrofluid for Nonpolar Aromatic Organic Solvents

NTA (0.382 g, 2.0 mmol) was reacted with 1-bromoacetylpyrene (BrCH ₂ C (O) C ₁₆ H ₉ , 0.97 g, 3.0 mmol) in 50 mL DMF solvent (HO _{2 CCH 2) 3 (C 16 H} 9 C (O) CH 2) N + Br - (0.89 g, yield 80%). The material thus formed is soluble in DMF or methylene chloride (MC) and insoluble in water and toluene. Cobalt ferrite magnetic material nanoparticles 0.2 g was dissolved in DMF 20 mL, and then an excess of _{(HO 2 CCH 2) 3 (} C 16 H 9 C (O) CH 2) N + Br - 3 were mixed to (0.89 g, 1.6 mmol) Stir well for hours. Since it does not sink even after surface treatment, methyl alcohol was added at a ratio of DMF / MeOH = 1/5 and settled using a centrifuge to remove excess organic matter. Toluene was added and dispersed. UV-Vis spectroscopic analysis confirmed 270-420 nm absorption peaks by pyrene and slow absorption peaks by -600 nm by magnetic nanoparticles.

Example 2-1 Preparation of Fat-Soluble Ferrofluid (MNP-EDC) Treated with an Ionic Organic Compound Containing EDC

In a 250 mL round bottom flask, 3-bromopropionic acid (15.3 g, 0.1 mol) was added, 100 mL of distilled water was dissolved, and 2 g of cobalt ferrite magnetic nanoparticles previously dispersed in 50 mL distilled water were stirred. Slowly added dropwise while stirring. The reaction proceeded for 3 hours, and the surface treated material began to precipitate. The precipitate was placed in a centrifuge tube and centrifuged at 3400 rpm. And washed with distilled water several times to remove excess material. 0.2 g of the submerged precipitate was dispersed in DMF unevenly and pre-purified dimethylaminopropylethylcarbodiimide {1- [3- (dimethylamino) propyl] -3-ethylcarbodiimide, EDC} (0.4 mL, 0.2 mmol) Injected. When the reaction proceeded while stirring for 5 hours, all were dispersed in the DMF solvent in a uniform state. Chloroform: DMF = 4: 1 When chloroform was added to the reaction vessel, precipitation was induced and recovered by centrifugation. This solution was also used to remove excess EDC. The final precipitate was obtained, the presence of EDC compound on the surface was confirmed by infrared spectroscopy and ICP-AES analysis, and the amount of EDC on the surface of the magnetic nanoparticle was quantified by TGA (EDC 2.8 mmol / 1.0 g). In addition, it was confirmed that the magnetic nanoparticles were spherical bodies having an average diameter of 9 nm through an electron transmission microscope [FIG. 2].

Example 2-2 EDC, EDC Attached to Polymer Support (P-EDC) Comparison of Reactivity between MNP-EDC and MNP

EDC (0.16 g, 1.0 mmol), MNP-EDC (0.36 g), and P-EDC (1 g) were added together with 10 mL DMF so that each container contained the same amount of EDC, Reaction was carried out after adding oxycarbonylphenylalanine (tert-butoxycarbonyl-phenylalanine, Boc-phe, 0.19 g, 0.7 mmol) and 3,5-dimethylaniline (3,5-dimethylaniline, 0.06 mL, 0.5 mmol). 0.1 mL of solution was taken from the reaction vessel every 12 hours at room temperature. MNP-EDC is separated by strong external magnet or centrifugation, P-EDC is removed by filtration, and gas-mass chromatography (GC-MS) analysis confirms the reaction progress and mass of the material. It was. The mass of the amide material formed by the condensation reaction was 329.6 (M ⁺ ) and was observed at 20.154 minutes. The yield comparison of the amide bond product over time is shown in FIG. 3.

Example 2-3 Condensation Reaction of Various Acids and Amines Using MNP-EDC

MNP-EDC (0.36 g / 10 mL DMF) was put in four different containers, 0.7 mmol of acids (benzoic acid, 3-iodobenzoic acid, 3,3-diphenylpropionic acid or Boc-phe) and amines (benzylamine, 3, 0.5 mmol of 3-diphenylpropylamine or 4-nitroaniline) was injected, followed by stirring at room temperature for 36 hours. After the reaction, by removing the magnetic nanoparticles bound by-products by using an external magnet or centrifuge, the reaction yield was confirmed by gas-mass chromatography analysis, and the mass was confirmed by mass analysis. The results for each reaction are shown in [Table 2].

[Table 2] Results of amide bond formation between various acids and amines by EDC compounds attached to the surface of magnetic nanoparticles

mountain Amine Amide bond Yield (%) Mass spectrometry (M ⁺ )

96 212.1

95 323.9

82 434.2

89 386.1

92 329.6

Example 3-1 Preparation of Ferrofluid Treated with Ionic Organic Compound Including ATRP Initiator

NTA (0.38 g, 2.0 mmol) was dissolved in 50 mL of DMF, 2-bromoethanol (0.31 g, 2.5 mmol) was added thereto, and the mixture was stirred for 3 hours. The DMF was removed via vacuum distillation and then extracted with MC / H ₂ O. The formed material was dissolved in 100 mL DMF again and cobalt ferrite (0.2 g, 20 mL DMF) solution was added dropwise slowly and stirred for 3 hours. Triethylamine (0.4 mL, 3.0 mmol) was added at 0 ^o C, and 2-bromoisobutyryl bromide (0.4 mL, 3.2 mmol) was added thereto at room temperature for 2 hours. After stirring, the solution became a dark red solution. A solution of DMF / THF = 1/5 volume ratio was added and a precipitate was obtained via centrifuge. The organics that may be present in excess were washed three times with the mixed solution. The formed surface treated magnetic nanoparticles were stably dispersed in an organic solvent such as DMF.

Example 3-2 Preparation of Polystyrene Polymer Using Ferrofluid Treated with Ionic Organic Compound Including ATRP Initiator

0.2 g of the magnetic nanoparticles with the initiator formed in Example 3-1 were dispersed in 10 mL DMF and placed in a reaction vessel. CuBr / PMDETA (copper bromide, 0.7 g, 5 mmol / N, N, N ', N', N ", N" -pentamethyldiethylene triamine, 0.87 g, 5.0 mmol) was carefully added. Nitrogen / vacuum circulation was performed three times to remove any oxygen that could be present in the reaction vessel. Purified styrene monomer (5.7 mL, 50 mmol) was added and the oxygen removal process was repeated. The mixture was maintained at 90 ^° C. for 24 hours using an oil bath. After the reaction, after cooling to room temperature, 20 mL of methyl alcohol is added quickly and a precipitate is obtained through a centrifuge. In order to remove excess Cu ⁺ catalyst and PMDETA, the mixture was washed several times with methyl alcohol, and recovered by taking only the dispersion in THF.

The UV-Vis spectrum of this material confirmed that the cobalt ferrite nucleus and the outer polystyrene shell existed at the same time, and the nucleus-shell structure was confirmed by electron transmission microscopy [FIG. 4]. Also Magnetic nanoparticles in the nucleus were dissolved by hydrochloric acid, and the polymer was grown by gel-permeation chromatography (GPC) analysis. The molecular weight and the molecular weight dispersion of the polystyrene were M _w = 37,000 and PDI = 1.88, respectively. .

Example 4-1 A method of manufacturing an organic / inorganic composite thin film using a ferrofluid treated with an ionic organic compound and a polymer

Surface treatment of the magnetic nanoparticles with nonpolar aromatic molecules is the same as in Example 1-3. A surface-treated ferrofluid (45 mg / toluene 10 ml) solution and a quantified polystyrene solution (0.1 g / toluene 10 ml) were used in the desired ratio (polystyrene: volume ratio of magnetic nanoparticles 0.2: 0.5 (# 1), 0.2: 0.25 ( # 2) and 0.4: 0.25 (# 3), respectively, 0.15 mL was placed on a clean surface-treated silicon wafer, and then rotated at 5000 rpm for 30 seconds with a rotary coater to form a thin film.

The magnetic nanoparticles surface-treated with the organic compound containing the non-polar aromatic molecules were irradiated by UV-Vis and infrared spectroscopy, and the thin film of the density of the magnetic nanoparticles was observed with an electron transmission microscope.

5 are photographs of the formed organic / inorganic thin film observed with an electron transmission microscope. In addition, as a result of performing magnetic inspection on each thin film sample with VSM (Vibrating Sample Magnetometer), the relative magnetization powers for samples of the same area were 7.8 x 10 ^-4 emu / volume (# 1) and 4.4 x 10 ^-4 emu /, respectively. Volume (# 2) and 3.0 x 10 ^-4 emu / volume (# 3) showed that the magnetization power gradually decreased as the density of the magnetic nanoparticles decreased.

As described above, the magnetic nanoparticles surface-treated with an ionic organic compound, preferably an organic compound containing ammonium ions, can be stably dispersed in an organic solvent even when an excessive amount of surfactant is not present.

Depending on the type of the ionic organic compound can be dispersed in various solvents, the fat-soluble ferrofluid treated with the ionic organic compound can be used in various chemical reactions [Fig. 6]. That is, when magnetic nanoparticles treated with an ionic organic compound are used as a support for a chemical reaction, reaction and product or by-products can be separated and / or purified after the reaction, and the surface of the ferrofluid is used as a reaction initiator. Can be synthesized. In addition, it can be applied to electromagnetic shielding and biomedical fields by synthesizing organic / inorganic hybrid thin films such as thin magnetic nanoparticles / organic polymers with easy density control.The surface treatment technology of magnetic nanoparticles can be applied to nanomaterials applications. Can be used.

Claims (22)

A method for producing a fat-soluble ferrofluid that is stably dispersed in an organic solvent without excessive surfactant by treating the surface of the magnetic nanoparticles with an ionic organic compound. The method of claim 1, wherein the ionic organic compound comprises an ammonium cation.  The process for producing a fat-soluble ferrofluid according to claim 2, wherein the ammonium cation is obtained from a nitrilotriacetic acid derivative. The method for producing a fat-soluble ferrofluid according to any one of claims 1 to 3, wherein the magnetic nanoparticles are metal ferrites (MFe ₂ O ₄ ). The metal (M) included in the metal ferrite is any one or two or more metals selected from the group consisting of Co, Mn, Fe, Ni, Cu, Zn, Mg, Cd, Ba, and Sr. The manufacturing method of fat-soluble ferrofluid to be. The method of claim 4, wherein the magnetic nanoparticles have a size of 1 to 300 nm. In the chemical reaction, magnetic nanoparticles of fat-soluble ferrofluid treated with ionic organic compounds on the surface of magnetic nanoparticles are used as a support, and chemical reactions are performed using the ionic organic compounds, followed by reaction using external magnetic force. A process for separating and / or purifying a product or byproduct. 8. The method of claim 7 wherein the ionic organic compound comprises an ammonium cation. The method of claim 8, wherein the chemical reaction is an amide bond formation reaction and the ionic organic compound also includes carbodiimide functional groups. 10. 10. The method of claim 7, wherein the magnetic nanoparticles are metal ferrites (MFe ₂ O ₄ ). 11. The method of claim 10, wherein the metal (M) included in the metal ferrite is any one or two or more metals from the group consisting of Co, Mn, Fe, Ni, Cu, Zn, Mg, Cd, Ba, and Sr. Method for separating and / or purifying the reaction product or by-products. The method of claim 10, wherein the magnetic nanoparticles have a size of 1 to 300 nm. It is characterized by using a fat-soluble ferrofluid treated the surface of the magnetic nanoparticles with an ionic organic compound, the organic compound reagent that can be separated by product by the external magnetic force and product purification by the external magnetic force because the organic compound is supported by the magnetic nanoparticles Manufacturing Method A method for producing a polymer by atomic transfer radical polymerization using a fat-soluble ferrofluid obtained by treating a surface of a magnetic nanoparticle with an ionic organic compound. The method of claim 14, wherein the polymer is polystyrene, polyethylene glycol, polymethylmethacrylate, or a block copolymer thereof. delete A method for producing an organic / inorganic hybrid composite thin film using a fat-soluble ferrofloid treated with a surface of a magnetic nanoparticle with an ionic organic compound. 18. The method of claim 17, wherein the ionic organic compound comprises a pyrene derivative. 19. The method of claim 18, wherein the organic / inorganic hybrid composite thin film is manufactured by a rotation coating method. Fat-soluble ferrofluid with the surface of magnetic nanoparticles treated with ionic organic compounds. 21. A fat-soluble ferrofluid treated with an ionic organic compound according to claim 20, wherein said ionic organic compound comprises an ammonium cation. 22. The fat-soluble ferrofluid treated with an ionic organic compound according to claim 20 or 21, wherein the magnetic nanoparticles are metal ferrites (MFe ₂ O ₄ ).

Images