Anion exchange membrane having excellent ion conductivity and alkali durability and preparation method thereof

Abstract

According to an embodiment of the present invention, provided is an anion exchange membrane having excellent ion conductivity and alkali durability, the anion exchange membrane comprising a copolymer prepared by Friedel-Crafts polymerization between an arylene-based monomer and two different carbonyl monomers, wherein the two different carbonyl monomers have Isatin and a fluoro functional group (-CF3), respectively.

Description

Anion exchange membrane with excellent ion conductivity and alkali resistance and method for manufacturing the same

[0001] This specification claims the benefit of the filing date of Korean Patent Application No. 10-2024-0175664 filed with the Korean Intellectual Property Office on November 29, 2024, the entire contents of which are incorporated into the present invention.

[0002] The present invention relates to an anion exchange membrane having excellent ion conductivity and alkali resistance, and a method for manufacturing the same.

[0003] The excessive use of fossil fuels is accelerating environmental pollution, leading to a global shift away from fossil fuel-based energy and the development of sustainable energy technologies. In particular, hydrogen possesses high energy density, and fuel cells, which generate electricity using hydrogen as fuel, offer superior power generation efficiency compared to internal combustion engines; consequently, there is a growing movement to utilize hydrogen as a primary energy source. However, since hydrogen is currently primarily obtained through natural gas reforming, it presents the problem of associated carbon emissions. Consequently, there is a growing need to produce green hydrogen using water electrolysis, which generates no CO2, in order to transition to a hydrogen economy.

[0004] Among various water electrolysis methods, anion exchange membrane (AEM)-based water electrolysis (AEMWE) utilizes hydroxyl ions (hydroxide, OH) generated from redox reactions -Hydrogen production occurs as ) is transferred from the cathode to the anode through the AEM. It is identical to PEMWE (proton exchange membrane-based water electrolysis) in that hydrogen is produced by transferring ions to the opposite electrode through a polymer electrolyte membrane, but during the reaction process, H + not OH - There is a difference in that it is conducted.

[0005] Furthermore, unlike PEMWE which operates under acidic conditions, AEMWE operates under alkaline conditions, so there is no risk of corrosion of components such as catalysts, gas diffusion layers (GDL), and bipolar plates. In addition, AEMWE has a standard reduction potential (E) of the anode where the oxidation evolution reaction (OER) occurs. o anode ) is 0.40 V, which is significantly lower than PEMWE's 1.23 V (i.e., electrochemically more favorable).

[0006] Accordingly, unlike PEMWE, which requires the use of platinum group metal (PGM) series precious metal catalysts, AEMWE allows the use of not only precious metal-based catalysts such as Pt, Ru, and Ir but also non-precious metal-based catalysts such as Ni, Mo, and Fe. Therefore, it offers advantages in terms of production costs compared to PEMWE, and because it uses an anion exchange membrane (AEM) as the electrolyte, it is free from leakage problems associated with the use of liquid electrolytes, thus offering excellent safety.

[0007] Accordingly, active research on AEMWE has recently been conducted, which includes studies on the development of non-precious metal catalysts as well as research on the development of AEM materials that possess high conductivity comparable to perfluorocarbon-based PEMs, such as Nafion, and excellent physical, chemical, and electrochemical stability.

[0008] Generally, hydroxy ions (OH - ) is a hydrogen cation (proton, H + Anion exchange membranes (AEMs) have a relatively lower diffusion coefficient compared to cation exchange membranes (PEMs), so they have lower ionic conductivity.

[0009] In addition, because it operates under high pH, ​​i.e., alkaline conditions, the highly reactive OH - There is a problem with chemical stability due to the degradation of the polymer backbone and conducting groups. Therefore, to improve the performance and durability of AEMWE, it is essential to develop anion exchange membranes with high ion conductivity and excellent chemical stability.

[0010] Generally, to achieve high ion conductivity, methods to increase the ion exchange capacity (IEC) of the membrane are used. However, excessively high IEC can lead to increased water uptake and weakened dimensional stability due to membrane swelling. For this reason, various methods are being investigated to design and synthesize ion-conducting polymers to achieve high ion conductivity at an appropriate IEC. In particular, research results have reported that the formation of microphase separation between hydrophilic and hydrophobic regions influences the improvement of ion conductivity in AEMs derived from such ion-conducting polymers.

[0011] In other words, the microphase separation between hydrophilic and hydrophobic is OH - It achieves high ionic conductivity by forming ion conduction channels that facilitate conduction. Furthermore, the enhanced hydrophobic unit leads to improved dimensional stability and mechanical stability.

[0012] AEM is made of ion-conducting polymers, which are divided into a polymer backbone that governs mechanical properties and ion-conducting head groups that contribute to ion conduction.

[0013] Polymer backbones are broadly classified into aryl ether-type and non-aryl ether-type polymer structures, with the former primarily utilizing poly(ether ketone), poly(ether sulfone), and poly(ethylene oxide). These polymers have the advantage of allowing for easy control of microphase separation, as multi-block copolymers can be obtained relatively easily by synthesizing hydrophilic and hydrophobic oligomers of a fixed length and then polymerizing them. However, these aryl ether-type polymers have a vulnerability to backbone degradation caused by hydroxyl ions.

[0014] On the other hand, non-aryl ether-type polymer-based AEMs exhibit high stability against hydroxide ions because the polymer backbone consists only of carbon, and such polymers include polystyrene, polyethylene, polynorbornene, poly(arylene alkylene), and SEBS (poly(styrene-b-ethylene-co-butylene-b-styrene)).

[0015] In particular, polyarylene-type AEMs exhibit excellent mechanical and thermal stability in addition to alkali stability, and unlike most polymers that introduce ion-conducting head groups mainly into the side chains, they have the advantage of having high IEC and consequent ion conductivity because the ion-conducting head groups are included in the polymer backbone. These polyarylene-type AEMs are obtained by using Friedel-Crafts polymerization between arylene-based monomers and carbonyl compounds containing head group units under a super-acid catalyst. Polymers such as polyterphenylene, polybiphenylene, and polyfluorene belong to this category, and it has been reported that water electrolysis (WE) using these polymer-based AEMs exhibits excellent cell performance comparable to or surpassing PEMWE.

[0016] However, it is known that some polyarylene-type AEMs exhibit excessive water absorption (WU) due to high IEC values, which leads to an increase in swelling rate (SR) and an excessive increase in hydrophilic regions, thereby inhibiting microphase separation and causing a deterioration in the mechanical properties and overall performance of the polymer membrane.

[0017] Therefore, there is a need for research on polyarylene-type anion exchange membranes that achieve high ion conductivity while suppressing excessive water content and have excellent alkali resistance.

[0018] The present invention relates to an anion exchange membrane having excellent ion conductivity and alkali resistance, and a method for manufacturing the same.

[0019] The objectives of the present invention are not limited to those mentioned above. The objectives of the present invention will become more apparent from the following description and will be realized by the means and combinations thereof described in the claims.

[0020] To solve the above problems, the present invention provides an anion exchange membrane having high alkali durability and ion conductivity and a method for manufacturing the same.

[0021] Specifically, according to one embodiment of the present invention, the copolymer having the structure of Formula 1 below is prepared by Friedel-Crafts polymerization between an arylene-based monomer and two different carbonyl monomers, and

[0022] (Chemical Formula 1)

[0023]

[0024] The above two different carbonyl monomers each have isatin and a fluoro functional group (-CF3), providing an anion exchange membrane with excellent ion conductivity and alkali resistance.

[0025] The above arylene-based monomer is characterized by having one or more selected from compounds represented by the structural formula of Chemical Formula 2 below.

[0026] (Chemical Formula 2)

[0027] .

[0028] The above-mentioned isatin is characterized by having an N-methylpiperidinium connected to a side chain represented by the structural formula of Chemical Formula 3 below.

[0029] (Chemical Formula 3)

[0030] .

[0031] The carbonyl monomer having the above-mentioned fluoro functional group (-CF3) is characterized as being 1,1,1-trifluoroacetone (1,1,1-trifluoroacetone, TFA).

[0032] The above n is characterized as being 0.75 to 0.975.

[0033] The above is characterized in that when n is 0.9, the ion conductivity of the anion exchange membrane is maximum, and thereafter, as n decreases, the ion conductivity decreases.

[0034] As n decreases, the hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) of the anion exchange membrane increase, and the water content and swelling rate decrease.

[0035] According to another embodiment of the present invention, a method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance is provided, comprising the steps of: mixing an arylene-based monomer, isatin, a carbonyl monomer having a fluoro functional group (-CF3), and N-methyl-4-piperidone; and performing a Friedel-Crafts polymerization reaction on the monomers to prepare a copolymer having the structure of Formula 1 below.

[0036] (Chemical Formula 1)

[0037] .

[0038] The above arylene-based monomer is characterized by having one or more selected from compounds represented by the structural formula of Chemical Formula 2 below.

[0039] (Chemical Formula 2)

[0040] .

[0041] The above-mentioned isatin is characterized by having an N-methylpiperidinium connected to a side chain represented by the structural formula of Chemical Formula 3 below.

[0042] (Chemical Formula 3)

[0043] .

[0044] The carbonyl monomer having the above-mentioned fluoro functional group (-CF3) is characterized as being 1,1,1-trifluoroacetone (1,1,1-trifluoroacetone, TFA).

[0045] In the present invention, a monomer-based polyarylene series anion exchange membrane having an arylene-based monomer and two different carbonyl monomers, isatin and a fluoro functional group (-CF3) was developed.

[0046] According to one embodiment of the present invention, additional conductive groups are formed in isatin connected to the polymer main chain, and due to these structural features, the anion exchange membrane of the present invention can form superior ion conduction channels compared to reported conventional linear polymer-based anion exchange membranes, and thereby improve ion conductivity.

[0047] In addition, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention can control hydrophobicity, specific surface area, and fractional free volume (FFV) due to a structure comprising a segment having additional conductive groups formed on isatin connected to a polymer main chain and a segment having fluoro functional groups (-CF3) connected to a polymer main chain, and can obtain the effect of improved ion conductivity by enhancing phase separation.

[0048] That is, by controlling the content of the monomer having the above-mentioned fluoro functional group (-CF3), hydrophobicity, specific surface area, and fractional free volume (FFV) can be controlled, and an enhanced phase separation effect can be obtained.

[0049] For example, in an anion exchange membrane having excellent ion conductivity and alkali resistance according to one embodiment of the present invention, as the content of the monomer having a fluoro functional group (-CF3) increases, the hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) of the anion exchange membrane increase, and the water content and swelling rate decrease.

[0050] In addition, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention can exhibit excellent alkali stability in KOH and NaOH solutions of 3M or higher with excellent phase separation characteristics while possessing high ion conductivity by introducing additional conductive groups to isatin connected to the polymer main chain.

[0051] When compared to an actual commercial anion exchange membrane (piperiON), it showed excellent alkali stability, indicating that chemical stability was improved through the introduction of isatin and fluoro functional group (-CF3) structures, thereby improving phase separation.

[0052] Specifically, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention showed a high ion conductivity of 46.14 mS / cm at room temperature and an ion exchange capacity (IEC) of 1.72 meq / g, thereby securing the target ion conductivity and ion exchange capacity.

[0053] FIG. 1 is a (pTP-Isa-Pip) according to a comparative example of the present invention x -(BP-Isa-Pip) 1-x(pTP:BP= 25:75) copolymer 1 This is the H NMR spectrum.

[0054] FIG. 2 is an (Aromatic-Isa-Pip) according to Example 1 of the present invention n -(Aromatic-TFA) 1-n copolymer(co(0.90:0.10)) 1 This is the H NMR spectrum.

[0055] FIG. 3 is an (Aromatic-Isa-Pip) according to Example 2 of the present invention n -(Aromatic-TFA) 1-n of copolymer (co(0.80:0.20)) 1 This is the H NMR spectrum.

[0056] FIG. 4 is a stress-strain curve of an anion exchange membrane according to Examples 1 and 2 and a comparative example of the present invention.

[0057] Figure 5 is a TGA curve of an anion exchange membrane according to Examples 1 and 2 and a comparative example of the present invention.

[0058] Figure 6 is a graph of the ion conductivity retention rate at 20°C of anion exchange membranes according to Examples 1 and 2 and a comparative example of the present invention.

[0059] The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments associated with the accompanying materials. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and that the spirit of the invention is sufficiently conveyed to a person skilled in the art.

[0060] In this specification, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0061] Unless otherwise specified, all numbers, values, and / or expressions representing ingredients and reaction conditions used herein shall be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among others. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including the maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to the maximum value including the maximum value, unless otherwise indicated.

[0062] According to one embodiment of the present invention, the copolymer having the structure of Formula 1 below is prepared by Friedel-Crafts polymerization between an arylene-based monomer and two different carbonyl monomers, and

[0063] (Chemical Formula 1)

[0064]

[0065] The above two different carbonyl monomers each have isatin and a fluoro functional group (-CF3), providing an anion exchange membrane with excellent ion conductivity and alkali resistance.

[0066] The above two different carbonyl monomers each have isatin and a fluoro functional group (-CF3), providing an anion exchange membrane with excellent ion conductivity and alkali resistance.

[0067] The above arylene-based monomer is characterized by having one or more selected from compounds represented by the structural formula of Chemical Formula 2 below.

[0068] (Chemical Formula 2)

[0069] .

[0070] The above-mentioned isatin is characterized by having an N-methylpiperidinium connected to a side chain represented by the structural formula of Chemical Formula 3 below.

[0071] (Chemical Formula 3)

[0072] .

[0073] The carbonyl monomer having the above-mentioned fluoro functional group (-CF3) is characterized as being 1,1,1-trifluoroacetone (1,1,1-trifluoroacetone, TFA).

[0074] The above n is characterized as being 0.75 to 0.975. Preferably, the above n may be 0.8 to 0.97, or 0.85 to 0.95, or 0.9 to 0.95, and more preferably, the above n may be 0.8 to 0.9.

[0075] The above is characterized in that when n is 0.9, the ion conductivity of the anion exchange membrane is maximum, and thereafter, as n decreases, the ion conductivity decreases.

[0076] When n increases, the content of the segment in which additional conductive groups are formed in the isatin connected to the polymer main chain increases, and in this case, the ion conductivity of the anion exchange membrane increases.

[0077] The additional conductive group formed in the above-mentioned isatin may be N-methylpiperidinium, specifically, 1-(6-bromohexyl)-1-methylpiperidinium as shown in Chemical Formula 4 below.

[0078] (Chemical Formula 4)

[0079]

[0080] When n increases, the ionic conductivity of the anion exchange membrane increases because the content of the additional conductor, N-methylpiperidinium, increases.

[0081] In addition, the anion exchange membrane according to one embodiment of the present invention can exhibit high ion conductivity by introducing additional conductive groups to isatin connected to the polymer main chain, while also exhibiting excellent alkali stability in KOH and NaOH solutions of 3M or higher due to excellent phase separation characteristics.

[0082] Meanwhile, as n decreases, the hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) of the anion exchange membrane increase, and the water content and swelling rate decrease.

[0083] When n is reduced, the content of the segment having a fluoro functional group (-CF3) connected to the polymer main chain increases, and in this case, the hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) of the anion exchange membrane increase, and the water content and swelling rate decrease.

[0084] That is, according to one embodiment of the present invention, the hydrophobicity of the anion exchange membrane can be controlled by adding a monomer having a fluoro functional group (-CF3) having hydrophobic properties to complement the hydrophilic properties of a segment having an additional conductive group formed in Isatin connected to a polymer main chain, and by including a segment having a fluoro functional group (-CF3) connected to a polymer main chain. As a result, the anion exchange membrane can possess high ion conductivity and exhibit excellent alkali stability in KOH and NaOH solutions of 3M or higher with excellent phase separation properties.

[0085] In addition, the specific surface area can be increased because the anion exchange membrane includes a segment having a fluoro functional group (-CF3).

[0086] In addition, since the anion exchange membrane contains a segment having a fluoro functional group (-CF3), the three F atoms increase the fractional free volume (FFV), thereby preventing effective packing of the corresponding polymer chain.

[0087] According to one embodiment of the present invention, additional conductive groups are formed in isatin connected to the polymer main chain, and due to these structural features, the anion exchange membrane of the present invention can form superior ion conduction channels compared to reported conventional linear polymer-based anion exchange membranes, and thereby improve ion conductivity.

[0088] In addition, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention has a structure comprising a segment having additional conductive groups formed on isatin connected to a polymer main chain and a segment having fluoro functional groups (-CF3) connected to a polymer main chain, which allows for the control of hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV), and can obtain the effect of improved ion conductivity by enhancing phase separation.

[0089] That is, by controlling the content of the monomer having the above-mentioned fluoro functional group (-CF3), hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) can be controlled, and a phase separation enhancement effect can be obtained.

[0090] For example, an anion exchange membrane having excellent ion conductivity and alkali resistance according to one embodiment of the present invention can achieve the effect of increasing hydrophobicity, specific surface area, and fractional free volume (FFV) as the content of the monomer having a fluoro functional group (-CF3) increases.

[0091] In addition, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention can achieve excellent mechanical properties as the maximum stress, elongation at break, and Young's modulus increase as the content of the monomer having a fluoro functional group (-CF3) increases.

[0092] In addition, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention can exhibit excellent alkali stability in KOH and NaOH solutions of 3M or higher with excellent phase separation characteristics while possessing high ion conductivity by introducing additional conductive groups to isatin connected to the polymer main chain.

[0093] It was shown that the phase separation was improved through the introduction of the isatin and fluoro functional group (-CF3) structures, as it exhibited excellent alkali stability when compared to the actual commercial anion exchange membrane (piperiON).

[0094] Through this, it can be seen that by offsetting the limitations of each segment (i.e., the low free volume of isatin and the low mechanical performance of the segment containing the fluoro functional group (-CF3)) against each other, an anion exchange membrane can be provided that has excellent mechanical properties, possesses high ion conductivity, and exhibits excellent alkali stability with excellent phase separation properties.

[0095]

[0096] According to another embodiment of the present invention, a method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance is provided, comprising the steps of: mixing an arylene-based monomer, isatin, a carbonyl monomer having a fluoro functional group (-CF3), and N-methyl-4-piperidone; and performing a Friedel-Crafts polymerization reaction on the monomers to prepare a copolymer having the structure of Formula 1 below.

[0097] (Chemical Formula 1)

[0098] .

[0099] The above arylene-based monomer is characterized by having one or more selected from compounds represented by the structural formula of Chemical Formula 2 below.

[0100] (Chemical Formula 2)

[0101] .

[0102] The above-mentioned isatin is characterized by having an N-methylpiperidinium connected to a side chain represented by the structural formula of Chemical Formula 3 below.

[0103] (Chemical Formula 3)

[0104] .

[0105] The carbonyl monomer having the above-mentioned fluoro functional group (-CF3) is characterized as being 1,1,1-trifluoroacetone (1,1,1-trifluoroacetone, TFA).

[0106] As a specific example, when the arylene-based monomers are biphenyl and p-terphenyl (para-terphenyl), respectively, a method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance according to another embodiment of the present invention comprises: a step of mixing biphenyl, p-terphenyl (para-terphenyl), isatin, a carbonyl monomer having a fluoro functional group (-CF3), and an N-methyl-4-piperidone monomer; and a step of performing a polymerization reaction on the monomers to prepare a copolymer.

[0107] The step of mixing the above-mentioned biphenyl, p-terphenyl (para-terphenyl), isatin, carbonyl monomer having a fluoro functional group (-CF3), and N-methyl-4-piperidone monomer, and then performing a polymerization reaction on the monomers, can be carried out through a Friedel-Crafts polymerization reaction.

[0108] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0109] experiment

[0110] substance

[0111] p-terphenyl (99%) and trifluoromethane sulfonic acid were purchased from TCI (Tokyo, Japan). Biphenyl (99%) and 1,1,1-trifluoroacetone (98+%) were purchased from Thermo Fisher Scientific (Waltham, Massachusetts, USA). 1,6-dibromohexane (96%) and isatin were purchased from α-aesar (Hevril, Massachusetts, USA). N-methylpiperidine was obtained from Sigma-Aldrich (St. Louis, Missouri, USA). Trifluoroacetic acid, methanol, ethyl acetate, dichloromethane, N-methyl-2-pyrrolidone, dimethyl sulfoxide, potassium hydroxide, and potassium carbonate were purchased from Daejeong Chemical Metal (Siheung, Korea). Other chemicals not specifically mentioned were procured from alternative commercial suppliers. Membrane treatment and characterization were performed using deionized water (distilled water) during the study period.

[0112]

[0113] Terphenyl-Biphenyl-Isatin-Piperidinium[(pTP-Isa-Pip) x -(BP-Isa-Pip) 1-x ] Synthesis of copolymer (Comparative example)

[0114] Copolymer (pTP-Isa) x -(BP-Isa) 1-xA mixture of p-terphenyl (0.3734 g, 1.6212 mmol), biphenyl (0.75 g, 4.8635 mmol), isatin (0.9541 g, 6.4847 mmol), and dichloromethane (5 mL) was placed into a 100 mL flask equipped with a mechanical stirrer and an N2 balloon. The reaction mixture was cooled to 0 °C and stirred for 10 minutes. Trifluoroacetic acid (0.7443 mL, 9.7270 mmol) and trifluoromethane sulfonic acid (2.8624 mL, 32.4233 mmol) were slowly added to the mixture and stirred; subsequently, the reaction temperature was increased from room temperature and the reaction was continued for 4 hours. The resulting reddish-brown homogeneous solution was poured into methanol. The precipitated polymer was filtered, dissolved in DMSO, and reprecipitated in methanol. Afterward, it was washed in methanol, and the resulting white copolymer was obtained. (pTP-Isa) x -(BP-Isa) 1-x (0.5 g, 1.6537 mmol), (1-(6-Bromohexyl)-1-methylpiperidinium) (1.7024 g, 4.9610 mmol), K2CO3 (0.4571 g, 3.3074 mmol), and NMP (10 ml) were placed in a vial and stirred while heating at 60 °C. The mixture was precipitated in EA:MeOH,H2O (200 ml:10 ml:10 ml) and washed in the same solvent. The resulting white [(pTP-Isa-Pip) x -(BP-Isa-Pip) 1-x A copolymer was obtained. The copolymer according to the above comparative example was prepared according to Schematic Figure 1 below.

[0115] (Schematic Diagram 1)

[0116]

[0117] In this comparative example, the molar ratio of pTP to BP (pTP:BP) was prepared as 25:75. The above (pTP-Isa-Pip) x -(BP-Isa-Pip) 1-xRegarding copolymers 1 The H NMR spectrum is shown in Figure 1.

[0118]

[0119] Terphenyl-Biphenyl-Isatin-Trifluoroaceton[(Aromatic-Isa-Pip) with different compositions n -(Aromatic-TFA) 1-n ] Synthesis of (pTP:BP= 25:75) copolymer (Example)

[0120] Random type copolymer with two different compositions (Aromatic-Isa-Pip) n -(Aromatic-TFA) 1-n was synthesized.

[0121] (Aromatic-Isa) n -(Aromatic-TFA) 1-n The copolymer was prepared by adding a mixture of p-terphenyl (0.3734 g, 1.6212 mmol), biphenyl (0.75 g, 4.8635 mmol), isatin (0.8587 g, 5.8362 mmol), 1,1,1-trifluoroacetone (0.0581 ml, 0.6492 mmol), and dichloromethane (3 mL) into a 100 mL flask equipped with a mechanical stirrer and an N2 balloon. The reaction mixture was cooled to 0 °C and stirred for 10 minutes. Trifluoromethane sulfonic acid (5.7245 mL, 64.8466 mmol) was slowly added to the mixture and stirred; subsequently, the reaction temperature was increased from room temperature and the reaction was continued for 36 hours. The resulting reddish-brown homogeneous solution was poured into methanol. The precipitated polymer was filtered, dissolved in DMSO, and reprecipitated in methanol. Afterward, it was washed in methanol, and the resulting white copolymer was obtained. (pTP-Isa) x -(BP-Isa) 1-x(0.5 g, 1.6731 mmol), (1-(6-Bromohexyl)-1-methylpiperidinium) (1.5501 g, 4.5174 mmol), K2CO3 (0.4162 g, 3.0116 mmol), and NMP (10 ml) were placed in a vial and stirred while heating at 60 °C. The mixture was precipitated in EA:MeOH,H2O (200 ml:10 ml:10 ml) and washed in the same solvent. The resulting white (Aromatic-Isa) n -(Aromatic-TFA) 1-n A copolymer was obtained. Copolymers and homopolymers of different compositions were synthesized according to the same method mentioned above.

[0122] The copolymers synthesized according to the above method were prepared to have compositions of co(0.90:0.10) (Example 1) and co(0.80:0.20) (Example 2), respectively, as shown in schematic figures 2 and 3 below.

[0123] (Schematic Diagram 2) (Example 1)

[0124]

[0125] (Schematic Diagram 3) (Example 2)

[0126]

[0127] In the above Examples 1 and 2, the molar ratio of pTP to BP (pTP:BP) was prepared based on 25:75.

[0128] (Aromatic-Isa-Pip) according to Example 1 above n -(Aromatic-TFA) 1-n For the copolymer (co(0.90:0.10)) 1 The H NMR spectrum is shown in Fig. 2. And, according to Example 2 above (Aromatic-Isa-Pip) n -(Aromatic-TFA) 1-n For the copolymer (co(0.80:0.20)) 1 The H NMR spectrum is shown in Figure 3.

[0129]

[0130] Anion exchange membrane manufacturing

[0131] All anion exchange membranes were prepared by casting from a solution (approx. 3 wt% in DMSO) in a flat-bottomed glass dish. The solvent was then allowed to evaporate slowly under vacuum at 48 °C. The corresponding polymer 1 was dissolved in DMSO (approx. 3 wt%), stirred overnight at room temperature, and then filtered through a cotton plug. In each case, the solution was carefully poured into a glass dish, covered with aluminum foil with small holes, and subjected to slow solvent evaporation in a vacuum oven at 48 °C. The solvent evaporation process was completed in 5 hours. After complete drying, the prepared membranes were cooled to room temperature, removed from the glass dish, dried further in an oven at 80 °C for 24 hours, and finally stored at ambient temperature. The membrane thickness was controlled to a range of 35–45 μm.

[0132]

[0133] Characteristics and Measurement

[0134] Structure and physical properties are 1 It was analyzed by H NMR. Thickness was measured using a micrometer. Thermal properties were determined by thermogravimetric analysis (TGA), and tensile properties were measured using a universal testing machine (UTM).

[0135]

[0136] Structural characteristics

[0137] The chemical structures of the synthesized monomers and polymers are 1 It was confirmed via ¹H NMR spectroscopy. Using DMSO as a reference, a 400 MHz NMR instrument (Agilent 400-MR) was used 1 The H NMR spectrum was obtained.

[0138]

[0139] Hydroxide ion conductivity

[0140] The hydroxide ion conductivity (σ) of each membrane (size: 10 mm X 40 mm) was calculated using the following equation:

[0141]

[0142] Here, L is the distance between reference electrodes and A is the cross-sectional length of the membrane. Ohmic resistance measurements (R) were performed using AC two-point probe impedance spectroscopy. The electrode system was connected via an SI-1287 electrochemical interface and an SI-1260 overhead impedance / gain phase analyzer at frequencies ranging from 100 MHz to 2 MHz. Conductivity measurements were performed in 20°C increments from 20°C to 80°C. For these conductivity measurements, the cell was immersed in deionized water. Conductivity values ​​were averaged over at least five tests during the same period.

[0143]

[0144] Ion exchange capacity (IEC)

[0145] OH - The experimental ion exchange capacity (IEC) values ​​of each membrane of the OH type were determined by acid-base back titration. - After washing the sample of the form several times with deionized water, immerse it in 10 mL of 0.01 M HCl standard aqueous solution for at least 24 hours and OH - The ions were neutralized. Then, the membrane was removed and dried in a vacuum oven at 40°C for 24 hours. The remaining HCl solution was titrated with a 0.01 M NaOH standard aqueous solution using phenolphthalein indicator. The following equation was used to determine the experimental IEC (meq / g):

[0146]

[0147] Here, V0 and C0 are the volume and concentration of the standard aqueous HCl solution, and V KOH and C KOH is the volume and concentration of the KOH standard aqueous solution used in the back titration, and W dry is the weight of the film after drying in a 40℃ oven for 24 hours.

[0148]

[0149] Water content (WU) and swelling rate (SR)

[0150] The water content (WU, %) and swelling rate (SR, %) of each membrane were calculated by immersing the circular membrane in water at 20°C. After immersing the membrane in deionized water for at least 24 hours and wiping the membrane surface with a tissue, the weight of the sample was rapidly measured (W wet ), length(l wet ) and thickness(t wet ) was measured. After vacuum drying the membrane for 24 hours, the weight of the dried membrane (W dry ), length(l dry ), thickness(t dry ) was measured. The following equation was used to determine WU(%) and SR(%):

[0151]

[0152]

[0153]

[0154] Mechanical properties and thermal stability

[0155] The mechanical properties of the membrane were measured using a benchtop tensile testing machine (Shimadzu EZ-TEST E2-L) at 25°C under 50% relative humidity at a crosshead speed of 1 mm / min. The engineering stress was determined using the cross-sectional area of ​​the sample in its initial state. Young's modulus (E) was calculated using the initial slope of the stress-strain curve. For this test, the membrane sample was prepared in a dumbbell shape with a total area of ​​40 mm x 10 mm and a test area of ​​20 mm x 10 mm.

[0156] The thermal stability of the membrane was investigated by thermogravimetric analysis (TGA) using a scinco TGA N-1000 instrument. TGA was operated under a nitrogen atmosphere from 30 to 800°C at a heating rate of 10°C.

[0157]

[0158] Alkali stability

[0159] OH - The membranes were immersed in a 5M KOH solution at 60°C for 720 hours to evaluate chemical stability by measuring changes in IEC and conductivity. Before measurement, each membrane was immersed in a freshly prepared 1M KOH solution at 40°C for at least 24 hours. After this period, the hydroxide ion conductivity of each membrane was measured in deionized water at 20°C.

[0160]

[0161] Experimental results

[0162] Random type copolymer with two different compositions (pTP-Isa-Pip) n -(BP-TFA) 1-n The method for synthesizing (co(0.90:0.10) (Example 1) and co(0.80:0.20) (Example 2)) involved mixing the biphenyl, p-terphenyl (para-terphenyl), isatin, carbonyl monomer having a fluoro functional group (-CF3), and N-methyl-4-piperidone monomer, and then performing a polymerization reaction on the monomers, wherein the polymerization reaction step was carried out through a Friedel-Crafts polymerization reaction.

[0163]

[0164] Ion exchange capacity (IEC), water absorption, swelling rate, ion conductivity

[0165] Table 1 below shows the results of comparing the ion exchange capacity (IEC), ion conductivity, water uptake (WU), and swelling ratio (SR) between anion exchange membranes according to one embodiment of the present invention (co(0.90:0.10) (Example 1) and co(0.80:0.20) (Example 2)) and anion exchange membranes according to a comparative example.

[0166]

[0167] Referring to [Table 1] above, the anion exchange membrane used according to one embodiment of the present invention is compared with the (pTP-Isa-Pip) according to the comparative example x -(BP-Isa-Pip) 1-x It showed excellent ionic conductivity compared to the (pTP:BP= 25:75) copolymer, indicating that phase separation was improved through the introduction of isatin and fluoro functional group (-CF3) structures.

[0168] Specifically, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention showed high ion conductivity of 46.14 mS / cm (Example 1) and 51.67 mS / cm (Example 2) at room temperature, and ion exchange capacity (IEC) of 1.72 meq / g (Example 1) and 1.43 meq / g (Example 2), indicating that the target ion conductivity (> 40 mS / cm) and ion exchange capacity (> 1.40 meq / g) can be secured.

[0169] Meanwhile, in the anion exchange membrane, water OH - It plays an important role as a medium for conducting ions, thereby improving ion conductivity. However, excessive moisture absorption can worsen, rather than improve, the mechanical properties of the membrane due to excessive expansion. In this regard, the AEM's IEC must be optimized to ensure the desired mechanical properties.

[0170] Water content and swelling rate were also measured for each membrane at 20°C. The anion exchange membrane according to one embodiment of the present invention, which has excellent ion conductivity and alkali resistance, showed reduced water absorption and expansion rates compared to the anion exchange membrane according to the comparative example (Table 1).

[0171] In addition, it can be seen that as the content of the carbonyl monomer having a fluoro functional group (-CF3) increases, the water content and swelling rate of the anion exchange membrane decrease.

[0172] In the present invention, the ion conductivity of anion exchange membranes according to one embodiment of the present invention (co(0.90:0.10) (Example 1) and co(0.80:0.20) (Example 2)) and anion exchange membranes according to a comparative example was measured in a temperature range of 20 to 80°C. The ion conductivity ranges of the anion exchange membranes according to one embodiment of the present invention (co(0.90:0.10) (Example 1) and co(0.80:0.20) (Example 2)) were 46.14-117.30 mS / cm and 51.67-115.41 mS / cm, respectively. On the other hand, the anion exchange membrane according to the comparative example was 47.11-104.00 mS / cm (Table 1).

[0173]

[0174] Mechanical and thermal properties

[0175] The anion exchange membrane is OH - In addition to transporting ions to the electrolyte, it must act as a physical separator between the oxidation and reduction electrodes to separate O2 and H2, which are the products of the water electrolysis operation. Consequently, the overall performance and durability of the water electrolysis operation can be critically affected by the thermal and mechanical stability of the anion exchange membrane.

[0176] The mechanical performance of the anion exchange membrane developed in the present invention was evaluated using tensile strength and strain index, and the results were presented as stress-strain curves for comparison. As the content of the monomer having a fluoro functional group (-CF3) increased, the hydrophobicity, maximum stress, elongation at break, and Young's modulus of the anion exchange membrane increased (Fig. 4).

[0177] Next, the thermal stability of each anion exchange membrane was evaluated using thermogravimetric analysis (TGA). As a result, three stages of membrane degradation were identified in the TGA curves. In the temperature range of 30–200°C, moisture inside the membrane evaporated, causing weight loss. The first weight loss led to a second weight loss in the range of 200–380°C. This second weight loss occurred due to the degradation of QA conductive groups grafted onto the side chains of isatin. At 400°C, the final weight loss began due to the degradation of the polymer backbone. The three cross-linked membranes exhibited similar thermal stability. Each was proven suitable for water electrolysis operations (Fig. 5).

[0178]

[0179] Alkali stability

[0180] The alkali stability of the embodiments and comparative examples of the present invention was evaluated as follows. Each anion exchange membrane was immersed in a 5M KOH solution at 60°C, and the decrease in ion conductivity was measured at regular intervals over 720 hours. The anion exchange membranes according to one embodiment of the present invention (co(0.90:0.10) (Example 1) and co(0.80:0.20) (Example 2)) both showed a certain decrease in ion conductivity during the 720-hour test period but maintained their characteristics almost. On the other hand, no ion conductivity was measured for the anion exchange membrane according to the comparative example during the 720-hour test (Table 2 and Fig. 6).

[0181]

[0182]

[0183] In the present invention, a monomer-based polyarylene series anion exchange membrane having an arylene-based monomer and two different carbonyl monomers, isatin and a fluoro functional group (-CF3) was developed.

[0184] According to one embodiment of the present invention, additional conductive groups are formed in isatin connected to the polymer main chain, and due to these structural features, the anion exchange membrane of the present invention can form superior ion conduction channels compared to reported conventional linear polymer-based anion exchange membranes, and thereby improve ion conductivity.

[0185] In addition, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention can control hydrophobicity, specific surface area, and fractional free volume (FFV) due to a structure comprising a segment having additional conductive groups formed on isatin connected to a polymer main chain and a segment having fluoro functional groups (-CF3) connected to a polymer main chain, and can obtain the effect of improved ion conductivity by enhancing phase separation.

[0186] That is, by controlling the content of the monomer having the above-mentioned fluoro functional group (-CF3), hydrophobicity, specific surface area, and fractional free volume (FFV) can be controlled, and an enhanced phase separation effect can be obtained.

[0187] For example, in an anion exchange membrane having excellent ion conductivity and alkali resistance according to one embodiment of the present invention, as the content of the monomer having a fluoro functional group (-CF3) increases, the hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) of the anion exchange membrane increase, and the water content and swelling rate decrease.

[0188] In addition, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention can exhibit excellent alkali stability in KOH and NaOH solutions of 3M or higher with excellent phase separation characteristics while possessing high ion conductivity by introducing additional conductive groups to isatin connected to the polymer main chain.

[0189] It was shown that the phase separation was improved through the introduction of the isatin and fluoro functional group (-CF3) structures, as it exhibited excellent alkali stability when compared to the actual commercial anion exchange membrane (piperiON).

[0190] Specifically, an anion exchange membrane with excellent ion conductivity and alkali resistance according to one embodiment of the present invention showed a high ion conductivity of 46.14 mS / cm at room temperature and an ion exchange capacity (IEC) of 1.72 meq / g, thereby securing the target ion conductivity and ion exchange capacity.

[0191]

[0192] The present invention described above is not limited to the aforementioned embodiments, as various substitutions and modifications are possible within the scope of the technical concept of the present invention without departing from the technical spirit of the present invention for those skilled in the art to which the present invention belongs.

Claims

1. A copolymer having the structure of Formula 1 below, prepared by Friedel-Crafts polymerization between an arylene-based monomer and two different carbonyl monomers, comprising (Chemical Formula 1) An anion exchange membrane with excellent ion conductivity and alkali resistance, characterized in that the two different carbonyl monomers above each have isatin and a fluoro functional group (-CF3).

2. In Paragraph 1, An anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that the above arylene-based monomer has one or more selected from compounds represented by the structural formula of Chemical Formula 2 below. (Chemical Formula 2) .

3. In Paragraph 1, The above-mentioned isatin is an anion exchange membrane having excellent ion conductivity and alkali resistance, characterized by having an N-methylpiperidinium group connected to a side chain represented by the structural formula of Chemical Formula 3 below. (Chemical Formula 3) .

4. In Paragraph 1, An anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that the carbonyl monomer having the above-mentioned fluoro functional group (-CF3) is 1,1,1-trifluoroacetone (1,1,1-trifluoroacetone, TFA).

5. In Paragraph 1, An anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that n is 0.75 to 0.

975.

6. In Paragraph 1, An anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that when n is 0.9, the ion conductivity of the anion exchange membrane is maximum, and thereafter, as n decreases, the ion conductivity decreases.

7. In Paragraph 1, An anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that as n decreases, the hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) of the anion exchange membrane increase, and the water content and swelling rate decrease.

8. A step of mixing an arylene-based monomer, isatin, a carbonyl monomer having a fluorofunctional group (-CF3), and N-methyl-4-piperidone; and A method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance, comprising the step of performing a Friedel-Crafts polymerization reaction on the above monomers to prepare a copolymer having the structure of Formula 1 below. (Chemical Formula 1) .

9. In Paragraph 8, A method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that the above arylene-based monomer comprises one or more selected from compounds represented by the structural formula of Chemical Formula 2 below. (Chemical Formula 2) .

10. In Paragraph 8, A method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that the above-mentioned isatin has N-methylpiperidinium connected to a side chain represented by the structural formula of Chemical Formula 3 below. (Chemical Formula 3) .

11. In Paragraph 8, A method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that the carbonyl monomer having the above-mentioned fluoro functional group (-CF3) is 1,1,1-trifluoroacetone (1,1,1-trifluoroacetone, TFA).

12. In Paragraph 8, A method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance using a radial polymer, characterized in that n is 0.75 to 0.

975.

13. In Paragraph 8, A method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that when n is 0.9, the ion conductivity of the anion exchange membrane is maximum, and thereafter, as n decreases, the ion conductivity decreases.

14. In Paragraph 8, A method for manufacturing an anion exchange membrane having excellent ion conductivity and alkali resistance, characterized in that as n decreases, the hydrophobicity, maximum stress, elongation at break, Young's modulus, specific surface area, and fractional free volume (FFV) of the anion exchange membrane increase, and the water content and swelling rate decrease.

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