KR102019887B1 - Ionic block copolymer and preparation method thereof - Google Patents

Abstract

The present invention relates to a block copolymer having a cationic or anionic property and a method for preparing the same, wherein an ionic block copolymer having both hydrophilicity and hydrophobicity with improved ion conductivity is prepared by the ARGET ATRP method. Application is possible, and it can be applied to electrodialysis membranes, secondary batteries, supercapacitors, fuel cells, redox flow batteries, and the like by thinning them.

Description

Ionic block copolymer and preparation method thereof

The present invention relates to a block copolymer having a cationic or anionic property and a method for preparing the same.

Block copolymers collectively refer to polymers obtained in such a way that one monomer polymerizes to form a polymer and the end group of the polymer followed by another monomer polymerizes to form a block. Unlike other random copolymers such as random copolymers and alternating copolymers, these block copolymers form a block because hydrophilic monomers and hydrophobic monomers form a block, but are covalently linked to each other. Due to their limited degree, they form nanostructures with a lamella structure. Because block copolymers can maximize the domain size of these lamellar structures than other polymers, the size of the domain can be adjusted according to the application environment, resulting in optimized performance.

The block copolymer may be prepared in a thin film form and applied to a redox flow battery, and the efficiency of the redox flow battery is determined by the ion conductivity of the thin film. Commercial membranes currently used in redox flow batteries include Daramic's AMV membrane, Selemion's APS membrane, and DuPont's Nafion membrane. There is this decreasing problem.

As an example of a technique for solving such a problem, Patent Publication No. 10-2015-0060394 discloses a polymer composite membrane having improved ion conductivity and permeability characteristics and a redox flow battery including the same, and specifically, hydrogen ion A polymer mixture containing 95 to 99% by weight of the sulfonated hydrocarbon-based first polymer having conductivity and 1 to 5% by weight of the fluorine-based hydrophobic second polymer; and 1 to 10 sulfonated silica based on 100 parts by weight of the polymer mixture. Disclosed is a polymer electrolyte composite membrane comprising a weight part and 0.01 to 20 weight part of an amphiphilic surfactant.

로부터 유래된 단위를 포함하며, 상기 소수성 블록은 양이온성기 및 할로겐기를 포함하는 것을 특징으로 하는 블록 중합체 및 이를 포함하는 고분자 전해질막에 대해 개시되어 있다.In addition, Patent Publication No. 10-2017-0113157 discloses a hydrophobic block; And a hydrophilic block, wherein the hydrophilic block is

It includes a unit derived from, the hydrophobic block is disclosed for a block polymer and a polymer electrolyte membrane comprising the same, characterized in that it comprises a cationic group and a halogen group.

However, in the above-described technique, a metal-based catalyst is generally required when polymerizing a polymer, and since the metal-based catalyst is ionic, it is difficult to purify because it is adsorbed on the hydrophilic portion of the block copolymer. . In addition, aqueous redox flow cells can damage electrodes and ion exchange membranes by using sulfuric acid as a supporting electrolyte, have a limited potential window, and limit battery operation at a wide range of temperatures. there is a problem.

In order to solve the above problems, the present invention can be used in a non-aqueous redox flow battery, has a high ion conductivity, a method of producing an ionic block copolymer that can use a minimum metal catalyst. Devised.

It is an object of the present invention to further provide a reducing agent for reducing metal, to provide an ionic block copolymer having a minimum metal catalyst, having excellent ionic conductivity, and usable in a non-aqueous system and a method for producing the same.

In order to achieve the above object, the present invention

A) synthesizing a polymer represented by Formula 2 below;

B) introducing a hydrophilic monomer;

C) obtaining a polymer represented by the following Chemical Formula 3-1 or Chemical Formula 3-2;

It provides a method for producing an ionic block copolymer comprising a.

{In Formulas 2, 3-1 and 3-2, X is halogen, A is an alkali metal, and n and m are each independently an integer of 1 to 100,000.}

In the step B), the hydrophilic monomer is preferably Formula 1 or sodium 4-styrene sulfonate.

In another aspect, the present invention provides an ionic block copolymer represented by Formula 3-1 or Formula 3-2 and an ion exchange membrane including the same. The ion exchange membrane thickness is preferably 10 to 100 µm, more preferably 10 to 50 µm.

The ion exchange membrane of the present invention can be used for a non-aqueous electrolyte, and the ion exchange membrane according to the present invention can be used for a secondary battery. That is, the ion exchange membrane which concerns on this invention can be used for the secondary battery whose electrolyte solution is a non-aqueous electrolyte solution.

Anionic block copolymers or cationic block copolymers according to embodiments of the present invention have optimized chemical and physical stability in non-aqueous, organic systems, and are useful as surfactants for dispersing insoluble solvents in compounds. It is possible. In addition, by thinning the ionic block copolymer, it can be applied to electrodialysis membranes, secondary batteries, supercapacitors, fuel cells, redox flow batteries and the like.

1 is (a) Proton Nuclear Magnetic Resonance spectroscopy ( ¹ H-NMR) data of Chemical Formulas 3-1 and (b) Chemical Formula 3-2.
FIG. 2 shows Fourier Transfer Infrared Spectroscopy (FT-IR) data of (a) Formula 2, (b) Formula 3-2, and (c) Formula 3-1.
3 is a membrane photograph of (a) a thin film of the formula (3-1), (b) formula (3-2).
FIG. 4 is a scanning electron microscope (SEM) image of a membrane obtained by thinning (a) Chemical Formula 3-1 and (b) Chemical Formula 3-2.
FIG. 5 is a TGA (Thermogravimetric analysis) curve for evaluating thermal characteristics of a membrane obtained by thinning (a) Chemical Formulas 3-1 and (b) Chemical Formula 3-2.
6 is a charge / discharge curve tested for charging and discharging of a redox flow battery of a membrane obtained by thinning (a) Chemical Formulas 3-1 and (b) Chemical Formula 3-2.

Hereinafter, with reference to the embodiment of the present invention will be described in detail. In describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

The present invention comprises the steps of synthesizing a hydrophilic monomer as in Scheme 1; Polymerizing polystyrene represented by Scheme 2 below; It provides a method for producing an ionic block copolymer comprising the step of synthesizing a cationic block copolymer or anionic block copolymer represented by the formula (3-1) or (3-2) as shown in Scheme 3.

<Scheme 1>

<Scheme 2>

<Scheme 3>

More specifically, for example, as shown in Scheme 1, 4-vinyl pyridine and iodoethane are subjected to quaternary amination reaction to form a cationic hydrophilic monomer represented by Formula 1 below. Provided is a method for synthesizing 4-vinylethylpyridinium iodide.

Scheme 1 is characterized in that 4-vinyl pyridine and iodoethane in a molar ratio of 1: 1 to react in acetonitrile, the reaction temperature is 60 ℃ is appropriate, the temperature that can be refluxed from room temperature The reaction can be elicited at a wide range of temperatures. In addition, the monomer produced by Scheme 1 may be obtained as a precipitate without being dissolved in acetonitrile when the reaction is completed to remove impurities.

As another specific example, Reaction Scheme 2 is a step of polymerizing polystyrene, wherein a distilled styrene monomer is used as an initiator with 1-propargyl bromide as an initiator in an anisole solvent. ARGET ATRP using copper (II) bromide / n, n, n ', n ″, n ″ -pentamethyldiethylenetriamine and tin (II) 2-ethylhexanoate, a copper catalyst reducing agent It provides a method for synthesizing polystyrene represented by the following formula (2) using the method.

Scheme 2 uses anisole (anisole) as a solvent, the reaction temperature is preferably 90 ℃ and characterized in that for 48 hours. Since external oxygen interferes with the reaction in the reaction vessel, it is important to ensure that the reaction vessel does not come into contact with the outside air.

As another specific example, Reaction Scheme 3 further polymerizes a hydrophilic monomer in a polystyrene end group, using sodium 4-styrene sulfonate or Chemical Formula 1 as an initiator. ARGET using copper (II) bromide / n, n, n ', n ″, n ″ -pentamethyldiethylenetriamine and tin (II) 2-ethylhexanoate, a copper catalyst reducing agent Provides a method for synthesizing polystyrene-block-poly (4-styrene sulfonate) represented by the following Chemical Formula 3-1 or polystyrene-block-poly (4-vinylethylpyridinium iodide) represented by the following Chemical Formula 3-2 using the ATRP method do.

{In Chemical Formula 3-1, X is halogen,

In Chemical Formula 3-2, A is an alkali metal,

n and m are each independently an integer from 1 to 100,000.}

Scheme 3 is N, N- dimethylformamide (N, N- dimethylformamide) as a solvent, the reaction temperature is preferably 90 ℃ and characterized in that for 48 hours. It is important to ensure that the reaction vessel does not come into contact with the outside air because external oxygen interferes with the reaction in the reaction vessel.

The anionic block copolymer and cationic block copolymer provided as described above can be used as a surfactant for dispersing a compound that does not dissolve in a specific solvent since both the hydrophilic portion and the hydrophobic portion are present in one polymer. Without being limited thereto, the film may be thinned and applied to an electrodialysis membrane, a secondary battery, a supercapacitor, a fuel cell, a redox flow battery, and the like.

Hereinafter, the synthesis examples of the compounds represented by Formula 1, Formula 2, Formula 3-1, and Formula 3-2 and thin film preparation examples using the same will be described in detail with reference to Examples, but the present invention is limited to the following Examples. It doesn't happen.

Synthesis Example

Synthesis Example 1 Synthesis of Chemical Formula 1

4-vinyl pyridine (4.2 g, 0.04 mmol), iodoethane (6.2 g, 0.04 mol) and acetonitrile (100 mL) were added to a two-neck round bottomed flask and stirred at 60 ° C. for 6 hours under a nitrogen purge. The resulting yellow powder was filtered under reduced pressure, washed well with methyl acetate and diethylether and dried.

Synthesis Example 2 Synthesis of Chemical Formula 2

Initiate propargyl bromide (8.12 μL) with styrene (6.64 mL), anisole (4.22 mL), CuBr _{2 in a} two-neck round bottomed flask (0.0037 g), PMDETA (58 μL), Sn (EH) ₂ Tin (II) 2-ethylhexanoate (89.5 uL) was added, immersed in liquid nitrogen, frozen, and vacuumed inside the flask using a vacuum pump. . The procedure was repeated three times and then stirred at 90 ° C. for 48 hours. The reaction solution is poured into methanol to obtain a white precipitate. The precipitate is filtered under reduced pressure, washed thoroughly with distilled water and dried.

Synthesis Example 3 Synthesis of Chemical Formulas 3-1 and 3-2

1) Synthesis of Chemical Formula 3-1

The molar ratio of Formula 2 and Formula 1 was adjusted to 1: 1.5, 1: 2, 1: 2.5 and CuBr ₂ in a two-neck round bottomed flask. (0.0037 g), PMDETA (58 μL), Sn (EH) ₂ (89.5 uL) and dimethylformamide (20 mL) were added together, immersed in liquid nitrogen, frozen, and vacuumed inside the flask using a vacuum pump. The procedure was repeated three times and then stirred at 90 ° C. for 48 hours. Formula 2 requires a melting time, so it proceeds after complete melting. The reaction solution was poured into methanol to obtain a brown precipitate, washed sufficiently with distilled water to remove the ion exchange group remaining unreacted, and dried to obtain the formula 3-1.

2) Synthesis of Chemical Formula 3-2

Sodium 4-styrene sulfonate is added instead of Formula 1, and the molar ratio of Formula 2 to sodium 4-styrene sulfonate is 1: 0.25, 1: 0.5, 1: 0.75, 1: 1, 1: 1.25 Chemical formula 3-2 was obtained using the synthesis method of -1.

Synthesis Example 4 Thin Film Preparation

1) Cationic Thin Film Preparation

10 wt% of the compound of Formula 3-1 synthesized by varying the molar ratio of the compound of Formula 3 (Chemical Formula 2: Chemical Formula 1 = 1: 1.5, 1: 2, 1: 2.5) in N-methyl-2-pyrrolidone solvent Completely dissolved in%, poured into a flat circular glass plate 10 cm in diameter, and the solution was evaporated for 24 hours at 80 ° C. in a vacuum oven. Water was poured on a glass plate to obtain a cationic thin film M1 (1: 1.5), M2 (1: 2), and M3 (1: 2.5) according to the molar ratio (Formula 2: Formula 1).

2) Anionic Thin Film Manufacturing

Formula 3-2 prepared by varying the molar ratio (Scheme 2: Sodium 4-styrene sulfonate = 1: 0.25, 1: 0.5, 1: 0.75, 1: 1, 1: 1.25) in Synthesis Example 3 is the cation Anionic thin film M4 (1: 0.25), M5 (1: 0.5), M6 (1: 0.75), M7 (1: 1) according to the molar ratio (Formula 2: sodium 4-styrene sulfonate) using a thin film manufacturing method 1), M8 (1: 1.25) was obtained.

Ionic block Copolymer  Characteristic evaluation

Example 1. ¹ H-NMR Analysis

Formula 3-1 and Formula 3-2 were analyzed by Proton Nuclear Magnetic Resonance spectroscopy ( ¹ H-NMR) to confirm the synthesis, which is shown in FIG. 1. As in FIG. 1, all peaks were observed, confirming successful synthesis.

Example 2. FT-IR Analysis

Formulas 3-1 and 3-2 were analyzed by Fourier-transform infrared spectroscopy (FT-IR), which is shown in FIG. 2. In Figure 2 (b) S = O peak was observed, in (c) it was confirmed that the synthesis was successful as -N ₃ peak is observed.

Example 3 Thin Film Characterization of Ionic Block Copolymers

1) visual analysis

A thin film photograph prepared using the above Chemical Formula 3-1 and Chemical Formula 3-2 is shown in FIG. 3. 3 (a) and 3 (b) are thin film photographs of Chemical Formulas 3-1 and 3-2, respectively, and are not hard, flexible, and may be bent and have yellow translucent properties.

2) SEM analysis

The prepared thin film was analyzed by Scanning Electron Microscope (SEM), which is shown in FIG. As shown in Figure 4, both the cationic and anionic thin film was found no cracks or holes on the surface, it was confirmed that the thin film was formed very dense.

3) TGA Analysis

Thermogravimetric analysis (TGA) was performed on the prepared thin films, which are shown in FIG. 5. As a result of confirming the TGA curve, it was confirmed that the ion exchange groups were pyrolyzed from around 400 ° C to 450 ° C in both the cationic and anionic block copolymer thin films.

4) physical evaluation

The ion exchange capacity, ion conductivity, electrolyte adsorption rate and swelling rate of the prepared cationic and anionic thin films were measured.

Ion exchange capacity ( IEC )

The ion exchange capacity of the prepared thin film was determined by a back titration method. The cationic and anionic thin films were completely dried at 80 ° C. for 24 hours, and then stirred for 24 hours in 1 M NaOH solution to convert the thin films to OH ⁻ form. The cationic and anionic thin films were completely dried at 80 ° C. for 24 hours, then stirred for 48 hours in 0.1 M HCl solution, and the remaining solution was titrated with 0.01 M NaOH solution using phenolphthalein indicator. The ion exchange capacity was calculated by the following formula.

(M _HCl : number of moles of HCl, M _NaOH : number of moles of NaOH added to titrate to the end point, M _dry : mass of completely dried thin film (g))

Ion conductivity

BF ₄ ⁻ ion conductivity and Et ₄ N ⁺ of the cationic thin film were measured by the four-electrode AC impedance spectroscopy method. Prior to the measurement, the cationic thin film and the anionic thin film were stirred for 5 days in a 1 M acetonitrile solution (1 M Et ₄ NBF ₄ ^- in acetonitrile) in which tetraethylammonium Tetrafluoroborate was dissolved, respectively. BF ₄ ^- were converted into a form. After 5 days, the cationic thin film and the anionic thin film were taken out and washed with a clean acetonitrile solution. Then, the anion exchange membrane was mounted in a Bekktech cell, the cell was soaked in acetonitrile solution, and then the frequency was between 1 Hz and 2 MHz. Ion conductivity was measured at an amplitude of 0.01 μA to obtain the resistance of the thin film. The BF ₄ ⁻ and Et ₄ N ⁺ ion conductivity were calculated by the following equation, and as a result, it was confirmed that it has a high ion conductivity of 2.77 mS / cm.

(L: distance between electrodes (cm), R: resistance of thin film measured through impedance (ohm), T: thickness of thin film (cm), W: length parallel to electrode of thin film (cm))

Electrolyte uptake ( EU ) and swelling ratio

Electrolyte uptake (EU) and swelling ratio of cationic and anionic thin films were measured in distilled water. First, the cationic and anionic thin films were dried at 80 ° C. for 24 hours, immersed in distilled water for 48 hours, and then the electrolyte adsorption rate and swelling rate were measured and calculated by the following equation.

(m _wet : weight of thin film soaked in distilled water, m _dry : weight of thin film completely dried)

(S _wet : length of membrane wetted with distilled water, S _dry : length of thin film completely dried)

To Table 1 shows the ion exchange capacity, resistance, ion conductivity, water adsorption rate, swelling rate of the cationic and anionic thin film prepared. The longer the hydrophilic portion of the polymer, the higher the ion exchange capacity of the cationic and anionic thin films. The ion resistance was measured, and the ion conductivity was proportional to the ion exchange capacity. Cationic thin films showed the highest ionic conductivity at M3 and anionic thin films at M7. The water adsorption rate did not differ significantly according to the intrinsic properties of the block copolymer, and it was confirmed that the swelling rate also did not differ significantly in the same context.

Membrane IEC (meq / g) Resistance (Ω / cm ² )  IC (mS / cm) Water uptake (%) Swelling ratio (%) M1 0.95 10780 0.011 13 6.0 M2 1.47 7584 0.016 6.8 5.6 M3 1.89 6347 0.035 7 14.4 M4 0.253 12017 0.017 7.7 8.0 M5 1.230 7792 0.016 16 4.0 M6 2.130 5485 0.022 7.1 3.3 M7 2.670 4943 0.040 6.2 6.7 M8 2.330 6505 0.036 7.1 6.7

5) Charge / discharge test

The cationic and anionic thin films thus prepared were applied to a redox flow battery to perform a galvanostatic charge / discharge test, which is shown in FIG. 6.

In the case of cationic thin films, vanadium (III) acetylacetonate (0.01 M) and tetraethylammonium tetrafluoroborate (0.5 M) were used as the acetonitrile organic electrolyte, and the potential was 1.7 V to 2.5 V, and 0.1 mA / A charge and discharge test was conducted under a cm ² charge and discharge constant current.

For anionic thin vanadyl (IV) sulfate (1.5 M) and sulfuric acid (3.0 M) a was used as a water-soluble electrolyte, the potential is 0.3 V ~ 1.4 and a V, the charge-discharge test under 20 mA / cm ² chungbang constant Proceeded.

The charge and discharge curves of FIG. 6 indicate that charge and discharge proceed smoothly in the redox flow battery in both the cationic and the anionic thin film. It was confirmed that the charging and discharging cycles did not occur as the charge and discharge cycles increased over time, and the chemical stability of the ionic block copolymer forming the thin film was excellent.

The above description is merely illustrative of the present invention, and those skilled in the art will appreciate that various modifications can be made without departing from the essential features of the present invention. Accordingly, the embodiments disclosed herein are not intended to limit the present invention but to describe the present invention, and the spirit and scope of the present invention are not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all the technologies within the equivalent scope should be construed as being included in the scope of the present invention.

Claims (9)

A) synthesizing a polymer represented by Formula 2 below;

B) introducing a hydrophilic monomer;
C) obtaining a polymer represented by the following Chemical Formula 3-1 or Chemical Formula 3-2;

Method for producing an ionic block copolymer comprising a
{In Formulas 2, 3-1 and 3-2, X is halogen, A is an alkali metal, and n and m are each independently an integer of 100 to 100,000.}
The method of claim 1, wherein the hydrophilic monomer in step B) is characterized in that the formula (1)

The method of claim 1, wherein the hydrophilic monomer in step B) is characterized in that sodium 4-styrene sulfonate (sodium 4-styrene sulfonate)
Ionic block copolymer represented by the following formula (3-1)

{In Formula 3-1, X is halogen, n and m are each independently an integer of 100 to 100,000.}
An ion exchange membrane comprising an ionic block copolymer represented by the following formula 3-1 or 3-2

{In Formulas 3-1 and 3-2, X is halogen, A is an alkali metal, and n and m are each independently an integer of 100 to 100,000.}
The ion exchange membrane of Claim 5 used for a non-aqueous electrolyte solution.
6. The ion exchange membrane as claimed in claim 5, wherein the exchange membrane has a thickness of 10 to 50 m.
A secondary battery comprising the ion exchange membrane according to any one of claims 5 to 7.
The secondary battery of claim 8, wherein the ion exchange membrane is used for a non-aqueous electrolyte.

Images