Anion exchange polymer comprising 4-x-quinuclidinium structure, method for preparing same, and anion exchange membrane comprising same

Abstract

An anion exchange polymer according to a preferred embodiment of the present invention includes a 4-X-quinuclidinium structure in which carbon corresponding to position 4 of a quinuclidinium ring is connected to a polymer main chain (X), and due to the absence of β-hydrogen placed in an anti-periplanar conformation with a nitrogen atom in the quinuclidinium ring, a Hoffmann elimination reaction does not occur. Therefore, there is the effect of having a chemically stable structure in a basic driving environment.

Description

Anion exchange polymer comprising a 4-X-quinuclidinium structure, a method for producing the same, and anion exchange membrane comprising the same

[0001] The present invention relates to an anion exchange membrane, and more particularly, to an anion exchange membrane comprising an anion exchange polymer having a 4-X-quinuclidinium structure with excellent alkaline stability, and a method for producing the same.

[0002] Anion Exchange Membrane (AEM) is a polymer membrane that acts as an electrolyte, and in an electrochemical system, it exchanges anions (mainly OH - , Cl - , Br - It plays a role in selectively transporting anions. This membrane functions to move anions within a positively charged polymer structure, and is utilized in various energy conversion devices such as anion exchange membrane fuel cell (AEMFC), anion exchange membrane water electrolysis system (AEMWE), redox flow battery (RFB), and reverse electrodialysis (RED) to selectively transport anions. The performance of AEM in these energy devices is largely determined by conductivity and stability, and for this, stability in alkaline conditions is essential.

[0003] Recently, there have been active efforts to develop polymers containing cationic functional groups with chemically stable structures in alkaline environments, and in the studies conducted to date, cationic functional groups such as piperidinium, imidazolium, and trimethyl ammonium (TMA) have been used as cationic functional groups for AEM applications. However, these structures are particularly prone to OH when exposed to basic environments. - They can be chemically decomposed by anion attack, and this chemical instability can act as a factor limiting the long-term performance of fuel cells and water electrolysis systems.

[0004] The present invention was conceived to solve the above-described problem, and provides an anion exchange polymer having a chemically stable structure in an alkaline operating environment, and in particular, having excellent alkaline stability due to the Hofmann elimination reaction by not forming an anti-periplanar conformation of β-hydrogen, and a method for producing the same.

[0005] The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0006] In order to achieve the above technical task, an anion exchange polymer according to a preferred example of the present invention may include a 4-X-quinuclidinium structure represented by the following chemical formula 1, in which a carbon atom corresponding to the 4th position of the quinuclidinium ring is connected to the polymer main chain (X);

[0007] [Chemical Formula 1]

[0008]

[0009] In the above chemical formula 1, X includes a repeating unit or an arylene compound represented by the following chemical formula 2, and R is hydrogen, a C1 to C20 alkyl group, a C1 to C20 aryl group, or a derivative thereof;

[0010] [Chemical Formula 2]

[0011]

[0012] In the above chemical formula 2, Ar includes an arylene compound, Y includes hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof, L includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof or a combination thereof, n is an integer of 1 or more, and x is an integer of 0 or more.

[0013] Additionally, in the chemical formula 2, X of the chemical formula 1 can be connected to the wave-marked position.

[0014] The above anion exchange polymer may include a repeating unit represented by the following chemical formula 3;

[0015] [Chemical Formula 3]

[0016]

[0017] In the above chemical formula 3, Ar1 includes an arylene compound, L1 includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof, or a combination thereof, R2 is hydrogen, a C1 to C10 alkyl group, a C1 to C10 alkoxy group, a C1 to C10 aryl group, or a derivative thereof, n is an integer greater than or equal to 1, and x is an integer greater than or equal to 0.

[0018] The above anion exchange polymer may include a repeating unit represented by the following chemical formula 4;

[0019] [Chemical Formula 4]

[0020]

[0021] In the above chemical formula 4, Ar2 includes an arylene compound, and n is an integer greater than or equal to 1.

[0022] The anion exchange polymer may include a poly(arylene-4-(N-methyl-quinuclidinium)) trifluoromethyl) repeating structure.

[0023] The above anion exchange polymer may be characterized by including a β-hydrogen that does not form an anti-periplanar conformation inside the quinuclidinium cage.

[0024] In order to achieve the above technical task, an anion exchange membrane according to a preferred example of the present invention may include the anion exchange polymer.

[0025] To achieve the above technical task, a membrane-electrode assembly according to a preferred example of the present invention may include the anion exchange polymer.

[0026] In order to achieve the above technical task, a water electrolysis system according to a preferred example of the present invention may include the anion exchange polymer.

[0027] In order to achieve the above technical task, a method for producing an anion exchange polymer according to a preferred example of the present invention may include a step (S01) of synthesizing a quinuclidine monomer by reacting a quinuclidine precursor, an organic acid, a catalyst, and a solvent; after step S01, a step (S02) of synthesizing a poly(arylene quinuclidine) polymer by performing a polycondensation reaction using the quinuclidine monomer, an arylene compound, and a superacid catalyst; and after step S02, a step (S03) of synthesizing a poly(arylene quinuclidinium) polymer by forming a quaternary ammonium salt using the quinuclidine polymer and an alkyl halide by a Menshutkin reaction.

[0028] According to the present invention as described above, the anion exchange polymer according to a preferred embodiment of the present invention has an effect of having a chemically stable structure in an alkaline driving environment because β-hydrogen does not form an anti-periplanar conformation and is resistant to Hofmann elimination reaction.

[0029] The effects of the present invention are not limited to those mentioned above, and also include other effects that are not explicitly mentioned, although they can be clearly understood by those skilled in the art from the description throughout the specification.

[0030] Figure 1 is a three-dimensional stereochemical structure for Quinuclidinium and Piperidinium according to one embodiment of the present invention (Source: L. Yin et al., Angew. Chem. Int. Ed., 63, e202400764-e202400773, 2024).

[0031] FIG. 2 is a chemical structure showing the binding position of β-hydrogen (indicated by a red arrow) in the 1-X-quinuclidinium (1-X-qui) and 4-X-quinuclidinium (4-X-qui) structures according to one embodiment of the present invention.

[0032] FIG. 3 is a flowchart showing the steps of synthesizing an anion exchange polymer comprising a 4-X-quinuclidinium structure according to one embodiment of the present invention.

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The advantages and features of the present invention, and methods for achieving them, will become clear with reference to the embodiments described in detail below together with the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0034] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise.

[0035] The terms "comprises" and / or "comprising" as used in the specification do not exclude the presence or addition of one or more other components, steps, operations and / or elements.

[0036]

[0037] Anion exchange polymer containing a 4-X-quinuclidinium structure

[0038] An anion exchange polymer according to one embodiment of the present invention may include a 4-X-quinuclidinium structure in which the 4-position of the quinuclidinium ring is connected to the polymer backbone (X).

[0039] [Chemical Formula 1]

[0040]

[0041] In the above chemical formula 1, X includes a repeating unit or an arylene compound represented by the following chemical formula 2, and R is hydrogen, a C1 to C20 alkyl group, a C1 to C20 aryl group, or a derivative thereof.

[0042] At this time, the anion is hydroxide ion (OH - ) may be used, and the notation may be omitted.

[0043] In the above chemical formula 1, quinuclidinium may be a cationic form of quinuclidine and may be a compound having a bicyclic structure. This structure may contain a nitrogen (N) atom shared by two rings and may have an ABCO (1-azabicyclo[2.2.2]octane) skeleton. In this quinuclidinium structure, the nitrogen atom is positively charged through quaternization and may contain various substituents (R1) bonded to the nitrogen atom site.

[0044] The above quinuclidinium may be included as a polymer side chain, and in particular, the carbon corresponding to the 4th position of the quinuclidinium ring may be connected to the polymer main chain (X). At this time, the carbon corresponding to the 4th position of the quinuclidinium ring may mean the third carbon atom from the nitrogen (N) atom. Specifically, the nitrogen (N) may correspond to the 1st position of the quinuclidinium ring, and the third carbon connected thereto may be the carbon corresponding to the 4th position of the quinuclidinium ring.

[0045] The carbon at position 4 of the quinuclidinium ring is sp 3 It can form a tetrahedral skeleton reflecting the hybridization state. Furthermore, these 4-carbon atoms maintain a bond angle of 109.5 degrees and can achieve high symmetry through a bicyclic structure. These structural characteristics create an overall balanced chemical structure, which can alleviate physical stress and minimize distortion that may occur during polymer formation. Consequently, the carbon atom at position 4 of the quinuclidinium ring can provide chemical stability and structural strength.

[0046] In particular, when a quinuclidine ring is included as a polymer side chain within the polymer structure, it has a bicyclic cage, which increases structural rigidity and reduces distortion, which can have the effect of increasing the chemical stability of the polymer. In addition, the quinuclidine structure within the polymer structure may be less susceptible to Hofmann elimination and may be relatively stable because the β-hydrogen does not form an anti-periplanar conformation. On the other hand, the piperidinium structure may have relatively low chemical stability compared to the quinuclidine structure because the β-hydrogen can be easily removed and decomposed in an alkaline environment.

[0047]

[0048] The above X may include a repeating unit or an arylene compound represented by the following chemical formula 2.

[0049] Specifically, the above X may include a repeating unit represented by the following chemical formula 2.

[0050] [Chemical Formula 2]

[0051]

[0052] In the above chemical formula 2, Ar includes an arylene compound, Y includes hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof, L includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof or a combination thereof, n is an integer of 1 or more, and x is an integer of 0 or more.

[0053] Additionally, in the chemical formula 2, X of the chemical formula 1 can be connected to the wave-marked position.

[0054] The above L is a spacer included in the polymer side chain, and may include a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof, or a combination thereof. Specifically, the L may include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a methoxy group, an ethoxy group, a phenyl group, a benzyl group, a phenylethyl group, a phenylpropyl group, a phenyloxy group, a methoxybenzene, a biphenyl, a triphenyl, a tetraphenyl, a derivative thereof, or a combination thereof.

[0055] Specifically, the Y may include hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof, and in one specific example, the Y may include a trifluoromethyl group (-CF3), but is not limited thereto. When the Y includes a trifluoromethyl group (-CF3), it may impart characteristics such as hydrophobicity, an electron withdrawing effect, enhanced thermal stability, and chemical resistance to the synthesized polymer.

[0056] The above spacer (L) serves to prevent distortion of the quinuclidinium cage. In particular, when the quinuclidinium structure is directly bonded to two phenyl groups included in the polymer main chain, structural instability of the quinuclidinium ring may be induced. Therefore, using an appropriate spacer (L) can alleviate such structural distortion and improve the chemical durability of the anion exchange polymer. The spacer (L) serves to secure a space between the quinuclidinium cage structure and the phenyl groups, thereby alleviating structural stress and maintaining flexible bonding within the polymer.

[0057] In addition, the spacer (L) has a characteristic that facilitates phase separation in which the hydrophobic polymer backbone (X) portion and the hydrophilic polymer side chain (4-X-quinuclidinium structure) portion are physically separated and positioned within the anion exchange polymer and the phases are distinguished from each other. Through this, the hydrophilic groups (4-X-quinuclidinium structure) can gather to effectively form anion transport channels within the anion exchange polymer, thereby improving ion conductivity.

[0058] The above arylene compound (Ar) is a polymer compound in which aromatic rings, such as aryl groups or arylene units, are repeatedly connected, and each arylene unit is generally derived from a benzene ring (C6H6) or another aromatic compound, and these can be connected to each other via carbon-carbon (CC), ether (O), or amine (N) bonds. For example, it can include a polymer structure formed by aryl groups being connected to each other via carbon-carbon bonds, ether bonds (-O-), or amine bonds (-NH-), such as polyphenylene (PP), polyphenylene ether (PPE), and polyphenylene amine. An arylene structure in which multiple aromatic rings are connected can exhibit the characteristics of high thermal stability, high mechanical strength, and excellent chemical resistance.

[0059] Specifically, the arylene compound (Ar) may include any one selected from compounds represented by the following structural formula or a derivative thereof;

[0060] , , , , , , , , , , , and ;

[0061] Here, the above R3 to R 11 Each of may independently include hydrogen, a C1 to C10 alkyl group, a C1 to C10 aryl group, or a derivative thereof, and a may be an integer of 1 or more.

[0062]

[0063] Meanwhile, the above X may not be an arylene compound (Ar) included in the repeating unit represented by the above chemical formula 2, but may be an arylene compound itself or an arylene compound to which a spacer (L) is connected to any part of the chemical structure. In this case, the R position of the arylene compound, for example, R3 to R 11 It may include the 4-X-quinuclidinium structure of the chemical formula 1 described above at the position of, or it may include the 4-X-quinuclidinium structure of the chemical formula 1 so as to be connected to a spacer (L) connected to any part in the chemical structure of the arylene compound.

[0064]

[0065] Specifically, the anion exchange polymer may include a repeating unit represented by the following chemical formula 3. More specifically, the anion exchange polymer may include a poly(arylene-4-(N-quinuclidinium)) trifluoromethyl) structure.

[0066] [Chemical Formula 3]

[0067]

[0068] In the above chemical formula 3, Ar1 includes an arylene compound, L1 includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof, or a combination thereof, R2 is hydrogen, a C1 to C10 alkyl group, a C1 to C10 alkoxy group, a C1 to C10 aryl group, or a derivative thereof, n is an integer greater than or equal to 1, and x is an integer greater than or equal to 0.

[0069]

[0070] More specifically, the anion exchange polymer may include a repeating unit represented by the following chemical formula 4. The anion exchange polymer may include poly(arylene-4-(N-methyl-quinuclidinium)) trifluoromethyl as a repeating unit.

[0071] [Chemical Formula 4]

[0072]

[0073] In the above chemical formula 4, Ar2 includes an arylene compound, and n is an integer greater than or equal to 1.

[0074]

[0075] Figure 1 is a three-dimensional stereochemical structure for Quinuclidinium and Piperidinium according to one embodiment of the present invention (Source: L. Yin et al., Angew. Chem. Int. Ed., 63, e202400764-e202400773, 2024).

[0076] Piperidinium has a hexacyclic structure without a hexagonal double bond, and this piperidinium-based structure continuously flips between boat and chair conformations. When this chair conformation is formed, the nitrogen atom is positioned in an anti-periplanar conformation with the axially located β-hydrogen, which can cause the Hofmann elimination (E2 elimination) reaction. As a result, the piperidinium ring is easily decomposed in alkaline environments, resulting in low chemical stability. In contrast, quinuclidine-based structures do not have a boat-and-chair conformation, and due to their unique bicyclic cage structure, there is no β-hydrogen positioned in an anti-periplanar conformation. Due to these structural features, quinuclidine-based structures are resistant to Hofmann elimination and are more chemically stable in basic environments.

[0077]

[0078] FIG. 2 is a chemical structure showing the binding position of β-hydrogen (indicated by a red arrow) in the 1-X-quinuclidinium (1-X-qui) and 4-X-quinuclidinium (4-X-qui) structures according to one embodiment of the present invention.

[0079] Referring to FIG. 2, in the case of the 1-X-qui structure, the N atom is directly connected to the alkyl chain, so the β-hydrogen exists outside the quinuclidinium cage, whereas in the case of the 4-X-qui structure, the β-hydrogen exists only inside the quinuclidinium cage. Specifically, in the 1-X-qui structure, there are six β-hydrogens (hydrogens bonded to the carbons marked as stable in 1-X-qui) inside the quinuclidinium cage, and there are two more β-hydrogens (hydrogens bonded to the carbons marked as unstable in 1-X-qui) on the alkyl chain outside the quinuclidinium cage. Here, the β-hydrogens inside the quinuclidinium cage do not form an anti-periplanar conformation and are therefore relatively stable, but the β-hydrogens located outside form an OH - It is in a vulnerable position that can be easily attacked by ions. This makes the 1-X-qui structure highly susceptible to decomposition in an alkaline environment.

[0080] In contrast, the 4-X-qui structure has a structure that can complement these vulnerabilities. Since the 4-X-qui structure has no β-hydrogens outside the quinuclidinium cage, it has high resistance to Hofmann elimination. In the 4-X-qui structure, all β-hydrogens exist only inside the quinuclidinium cage (hydrogens bonded to the carbons marked as stable in 4-X-qui), and they do not form an anti-periplanar conformation, making them stable even in basic environments. Therefore, the 4-X-qui structure provides much better stability in basic environments than 1-X-qui, and can serve as a more suitable structure in various applications requiring high temperature and basic conditions.

[0081] [Chemical Formula 5]

[0082]

[0083] Meanwhile, since the 3-X-quinuclidinium (3-X-qui) structure (chemical formula 5) is not a bilaterally symmetrical structure, the bond angle can easily be distorted when a bulky group exists nearby. If the bond angle is distorted, the excellent alkaline stability inherent in the quinuclidinium ring may be damaged, which may reduce the chemical resistance and durability of the polymer, and consequently, the performance of the polymer in an alkaline environment may be significantly reduced. On the other hand, the 4-X-quinuclidinium (4-X-qui) structure has a bilaterally symmetrical structure, which minimizes structural distortion of the polymer and can improve structural stability and ionic conductivity.

[0084]

[0085] Method for preparing an anion exchange polymer comprising a 4-X-quinuclidinium structure

[0086] FIG. 3 and the following reaction schemes 1 to 3 are a flow chart and reaction schemes showing the synthesis steps of an anion exchange polymer including a 4-X-quinuclidinium structure according to one embodiment of the present invention.

[0087] [Reaction Formula 1]

[0088]

[0089] [Reaction Formula 2]

[0090]

[0091] [Reaction Formula 3]

[0092]

[0093] In the above reaction formulas 1 to 3, Ar comprises an arylene compound, and R 12 is hydrogen, a C1 to C20 alkyl group, a C1 to C20 aryl group or a derivative thereof, Y2 comprises hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof, A is a C1 to C3 alkyl group, n is an integer of 1 or more, and X' is a halogen element.

[0094]

[0095] Referring to FIG. 3 and reaction schemes 1 to 3, a step (S01) of first reacting a quinuclidine precursor, an organic acid, a catalyst, and a solvent to synthesize a quinuclidine monomer can be performed.

[0096] The above quinuclidine precursor may include a quinuclidine compound containing a carboxylic moiety. Specifically, the quinuclidine precursor may be a compound containing a carboxylic moiety at the carbon atom corresponding to position 4 of the quinuclidine double ring.

[0097] Specifically, the quinuclidine precursor may include a compound represented by the following chemical formula 6, a salt thereof, or a hydrate thereof.

[0098] [Chemical Formula 6]

[0099]

[0100] In the above chemical formula 6, R 12 is hydrogen, a C1 to C20 alkyl group, a C1 to C20 aryl group, or a derivative thereof.

[0101] In one specific example, the quinuclidine precursor may include, but is not limited to, quinuclidine-4-carboxylic acid.

[0102] Additionally, the organic acid can react with the OH group of the carboxylic moiety of the quinuclidine precursor to introduce an acyl group (-COR). Specifically, the organic acid can include a non-fluorinated organic acid, a fluorinated organic acid, an anhydride thereof, or a combination thereof. For example, the organic acid can include a non-fluorinated organic acid including acetic anhydride, propionic anhydride, butyric anhydride, benzoic anhydride, or maleic anhydride; a fluorinated organic acid including trifluoroacetic anhydride (TFAA), pentafluoropropionic anhydride, or pentafluorobenzoic anhydride; or a combination thereof. More specifically, the organic acid may be a fluorinated organic acid, including, but not limited to, trifluoroacetic anhydride (TFAA) in one specific example.

[0103] The catalyst may be used as a catalyst and an organic solvent in the reaction of the above reaction scheme 1, and may include, for example, any one selected from among pyridine, 4-dimethylaminopyridine (DMAP), triethylamine (TEA), N,N-dimethylaniline, triisopropylamine (TIPA), and combinations thereof. In one specific example, the catalyst may include pyridine, but is not limited thereto.

[0104] The solvent may be a polar solvent, and may include, for example, any one selected from water, acetone, dimethylformamide (DMF), dichloromethane (DCM), tetrahydrofuran (THF), methanol, ethanol, ethyl acetate, and combinations thereof. In one specific example, the solvent may include, but is not limited to, water.

[0105] The above catalyst and the above solvent can induce or promote hydrolysis and decarboxylation reactions of the reactants.

[0106]

[0107] Next, a step (S02) of synthesizing a poly(arylene quinuclidine) polymer by polycondensation reaction using the above quinuclidine monomer, arylene compound, and superacid catalyst can be performed.

[0108] The synthesized quinuclidine monomer may include a compound represented by the following chemical formula 7, a salt thereof, or a hydrate thereof.

[0109] [Chemical Formula 7]

[0110]

[0111] In the above chemical formula 7, Y2 may include hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof.

[0112] Specifically, the quinuclidine monomer is quinuclidine-4-carboxaldehyde, quinuclidine-4-acetyl, quinuclidine-4-propionyl, quinuclidine-4-methoxycarbonyl, quinuclidine-4-ethoxycarbonyl, quinuclidine-4-benzoyl, quinuclidine-4-benzylcarbonyl, quinuclidine-4-trifluoroacetyl, Quinuclidine-4-trifluoromethoxycarbonyl, quinuclidine-4-hexafluoroethoxycarbonyl, or a derivative thereof may be included. In one specific example, the quinuclidine monomer may include, but is not limited to, quinuclidine-4-trifluoroacetyl.

[0113] The above arylene compound may include any one selected from compounds represented by the following structural formula or a derivative thereof;

[0114] , , , , , , , , , , , and ;

[0115] Here, the above R3 to R 11 Each of may independently include hydrogen, a C1 to C10 alkyl group, a C1 to C10 aryl group, or a derivative thereof, and a may be an integer of 1 or more.

[0116]

[0117] The above superacid catalyst may be a compound used in a polycondensation reaction because it has a very strong acidity and promotes the formation and bonding of polymer chains. Specifically, this polymerization may be a Friedel-Crafts type polycondensation reaction, which may be a polyhydroxyalkylation reaction using an acetic acid catalyst.

[0118] Specifically, the superacid catalyst may include any one selected from trifluoromethanesulfonic acid (TFSA), fluorosulfonic acid (FSO3H), pentafluoromethanesulfonic acid, methanesulfonic acid, and combinations thereof. In one specific example, the superacid catalyst may include, but is not limited to, trifluoromethanesulfonic acid (TFSA).

[0119] The polymer synthesized by the above polycondensation reaction may include a poly(arylene quinuclidine) polymer represented by the following chemical formula 8.

[0120] [Chemical Formula 8]

[0121]

[0122] In the above chemical formula 8, Ar3 includes an arylene compound, Y2 includes hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof, and n may be an integer of 1 or more.

[0123]

[0124] Next, after polymerization is completed, a step (S03) of synthesizing a poly(arylene quinuclidinium) polymer by forming a quaternary ammonium salt through a Menshutkin reaction using the quinuclidine polymer and an alkyl halide can be performed.

[0125] The Menshutkin reaction is a reaction in which a tertiary amine reacts with an alkyl halide (denoted as AX') to form a quaternary ammonium salt. It follows a nucleophilic substitution reaction (SN2 mechanism), and can refer to a reaction in which the nitrogen atom of the nucleophilic amine bonds to the alkyl group of the alkyl halide and drops a halogen atom. Specifically, when the Menshutkin reaction occurs in the quinuclidine double ring structure, the nitrogen (N) atom of quinuclidine, a tertiary amine containing an unshared electron pair, reacts with an alkyl halide, such as iodomethane (CH3I or MeI), so that the nitrogen becomes positively charged and a process of forming a quaternary ammonium compound can be performed. Quaternized quinuclidine may be denoted as quinuclidinium and may function as anion carrier in anion exchange polymers.

[0126] The anion exchange polymer including the poly(arylene quinuclidinium) polymer after the above quaternization is completed may include a polymer represented by the following chemical formula 9.

[0127] [Chemical Formula 9]

[0128]

[0129] In the above chemical formula 9, Ar3 includes an arylene compound, Y2 includes hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof, and n may be an integer of 1 or more.

[0130]

[0131]

[0132] Hereinafter, the present invention will be described in more detail using examples and comparative examples. However, the following examples and comparative examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0133]

[0134] Manufacturing Example 1: Synthesis of poly(arylene-4-(N-methyl-quinuclidinium)) trifluoromethyl) anion exchange polymer (4-X-qui)

[0135] The following reaction schemes 4 to 6 illustrate the synthesis steps of an anion exchange polymer based on poly(arylene-4-(N-methyl-quinuclidinium)) trifluoromethyl according to one embodiment of the present invention.

[0136] [Reaction Formula 4]

[0137]

[0138] [Reaction Formula 5]

[0139]

[0140] [Reaction Formula 6]

[0141]

[0142] In the above reaction formulas 4 to 6, Ar4 includes an arylene compound, and n is an integer greater than or equal to 1.

[0143] First, quinuclidine-4-carboxylic acid is dissolved in toluene and then reacted with trifluoroacetic anhydride (TFAA) to substitute the carboxylic moiety with a trifluoroacetyl group, thereby synthesizing the quinuclidine-4-trifluoroacetate monomer. During this process, pyridine and water (H2O) induce hydrolysis and decarboxylation of the reactant.

[0144] Afterwards, the synthesized monomer and arylene compound are dissolved in dichloromethane (DCM) and reacted with trifluoromethanesulfonic acid (TFSA) to polymerize a polymer through a Friedel-Crafts type polycondensation reaction, i.e., polyhydroxyalkylation using acetic acid as a catalyst.

[0145] After polymerization is complete, quaternization is performed through Menshutkin reaction by reacting with methyl iodide (MeI; Iodomethane). Ultimately, a poly(arylene quinuclidinium)-based anion exchange polymer is synthesized.

[0146]

[0147] Example 1: Anion exchange membrane (4-X-qui) comprising poly(arylene-4-(N-methyl-quinuclidinium)) trifluoromethyl

[0148] An anion exchange membrane was manufactured using the above Manufacturing Example 1 and the poly(arylene-4-(N-methyl-quinuclidinium)) trifluoromethyl) anion exchange polymer (4-X-qui) represented by the following chemical formula 10.

[0149] [Chemical Formula 10]

[0150]

[0151] In the above chemical formula 10, Ar4 includes an arylene compound, and n is an integer greater than or equal to 1.

[0152]

[0153] Comparative Example 1: Anion exchange membrane (1-X-qui) containing poly(arylene-1-(N-quinuclidinium)) trifluoromethyl

[0154] An anion exchange membrane was prepared using a poly(arylene-1-(N-quinuclidinium)) trifluoromethyl anion exchange polymer (1-X-qui) represented by the following chemical formula 11.

[0155] [Chemical Formula 11]

[0156]

[0157] In the above chemical formula 11, Ar5 includes an arylene compound, L2 includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof, or a combination thereof, n is an integer greater than or equal to 1, and x' is an integer greater than or equal to 0.

[0158]

[0159] When comparing the characteristics of the anion exchange membrane according to Example 1 and Comparative Example 1 of the present invention, in the case of the 1-X-qui structure (Comparative Example 1), the N atom of the quinuclidinium ring is directly connected to the polymer side chain, so that β-hydrogen exists outside the quinuclidinium cage. The β-hydrogens located outside are OH - ions. Therefore, the 1-X-qui structure (Comparative Example 1) is likely to be decomposed in an alkaline environment. On the other hand, in the case of the 4-X-qui structure (Example 1), since the β-hydrogen exists only inside the quinuclidinium cage, not all of the β-hydrogens form an anti-periplanar conformation with the nitrogen atom, making it relatively stable even in an alkaline environment. Therefore, the 4-X-qui structure (Example 1) provides much better stability in an alkaline environment than the 1-X-qui (Comparative Example 1), and can provide a structure suitable for various applications requiring high temperature and alkaline conditions.

[0160]

[0161] Comparative Example 2: Anion exchange membrane comprising polyarylene-3-(N-methyl-quinuclidinium) (3-Poly(arylene-N-methyl-quinuclidinium))

[0162] An anion exchange membrane was prepared using a polyarylene-3-(N-methyl-quinuclidinium) (3-Poly(arylene-3-(N-methyl-quinuclidinium)) anion exchange polymer represented by the following chemical formula 12.

[0163] [Chemical Formula 12]

[0164]

[0165] In the above chemical formula 12, Ar6 is an arylene compound, and n is an integer greater than or equal to 1.

[0166]

[0167] When comparing the characteristics of the anion exchange membranes according to Example 1 and Comparative Example 2 of the present invention, in the case of Comparative Example 2, since the quinuclidinium ring is directly connected to the aromatic ring of the polymer main chain on the side, there is a high possibility that distortion of the bicyclic ring will be induced, which may reduce the alkaline stability of the polymer. On the other hand, the 4-X-qui structure (Example 1) has a structural feature in which it is not directly connected to the phenyl ring of the polymer main chain and distortion may hardly occur due to the spacer. Therefore, the 4-X-qui structure (Example 1) can improve the alkaline stability compared to Comparative Example 2.

[0168]

[0169] Comparative Example 3: Anion exchange membrane containing poly(arylene-4-(N,N-dimethyl piperidinium)) trifluoromethyl

[0170] An anion exchange membrane was prepared using a poly(arylene-4-(N,N-dimethyl piperidinium)) trifluoromethyl anion exchange polymer represented by the following chemical formula 13.

[0171] [Chemical Formula 13]

[0172]

[0173] In the above chemical formula 13, Ar7 includes an arylene compound, L3 includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof, or a combination thereof, n is an integer of 1 or greater, and x" is an integer of 0 or greater.

[0174]

[0175] When comparing the characteristics of the anion exchange membranes according to Example 1 and Comparative Example 3 of the present invention, Comparative Example 3 is characterized by including a piperidinium ring structure in the polymer side chain, and this piperidinium-based structure continuously flips between boat and chair conformations in terms of its chemical structure. In this process, when the chair structure is formed, the nitrogen atom in the ring and the β-hydrogen located in the axial direction are positioned in an anti-periplanar position, which may promote the Hofmann elimination (E2 elimination) reaction. As a result, the piperidinium ring is easily decomposed in a basic environment, resulting in low chemical stability. On the other hand, in the case of the 4-X-qui structure (Example 1), due to the structural characteristic of not forming an anti-periplanar conformation due to the bicyclic cage form based on quinuclidine, it is resistant to the Hofmann elimination reaction and can be more chemically stable even in an alkaline environment.

[0176]

[0177] Comparative Example 4: Anion exchange membrane comprising poly(arylene-4-(N,N-dimethyl piperidinium))

[0178] An anion exchange membrane was prepared using a poly(arylene-4-(N,N-dimethyl piperidinium)) anion exchange polymer represented by the following chemical formula 14.

[0179] [Chemical Formula 14]

[0180]

[0181] In the above chemical formula 14, Ar8 is an arylene compound, and n is an integer greater than or equal to 1.

[0182]

[0183] When comparing the characteristics of the anion exchange membranes according to Example 1 and Comparative Example 4 of the present invention, in the case of Comparative Example 4, due to the structural characteristic that the carbon in the piperidinium ring is directly connected to the polymer backbone, distortion of the hexacyclic structure is induced, thereby increasing structural instability. On the other hand, in the case of the 4-X-qui structure (Example 1), not only is it not directly connected to the phenyl ring of the polymer backbone, but it also has a structural characteristic that the Hoffmann elimination reaction may not occur due to its unique bicyclic cage form.

[0184]

[0185] Although embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. In anion exchange polymers, An anion exchange polymer represented by the following chemical formula 1, comprising a 4-X-quinuclidinium structure in which the carbon corresponding to the 4th position of the quinuclidinium ring is connected to the polymer backbone (X); [Chemical Formula 1] In the above chemical formula 1, X includes a repeating unit or an arylene compound represented by the following chemical formula 2, and R1 is hydrogen, a C1 to C20 alkyl group, a C1 to C20 aryl group, or a derivative thereof; [Chemical Formula 2] In the above chemical formula 2, Ar includes an arylene compound, Y includes hydrogen, a methyl group (-CH3), an ethyl group (-C2H5), a methoxy group (-OCH3), an ethoxy group (-OC2H5), a phenyl group (-C6H5), a benzyl group (-CH2C6H5), a trifluoromethyl group (-CF3), a trifluoromethoxy group (-OCF3), a hexafluoroethoxy group (-OC2F6) or a derivative thereof, L includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof or a combination thereof, n is an integer of 1 or more, and x is an integer of 0 or more.

2. In paragraph 1, The above anion exchange polymer is an anion exchange polymer comprising a repeating unit represented by the following chemical formula 3; [Chemical Formula 3] In the above chemical formula 3, Ar1 includes an arylene compound, L1 includes a C1 to C10 alkyl group, a C1 to C10 aryl group, a derivative thereof, or a combination thereof, R2 is hydrogen, a C1 to C10 alkyl group, a C1 to C10 alkoxy group, a C1 to C10 aryl group, or a derivative thereof, n is an integer greater than or equal to 1, and x is an integer greater than or equal to 0.

3. In paragraph 1, The above anion exchange polymer is an anion exchange polymer comprising a repeating unit represented by the following chemical formula 4; [Chemical Formula 4] In the above chemical formula 4, Ar2 includes an arylene compound, and n is an integer greater than or equal to 1.

4. In paragraph 1, The above anion exchange polymer is an anion exchange polymer comprising a poly(arylene-4-(N-methyl-quinuclidinium)) trifluoromethyl) repeating structure.

5. In paragraph 1, An anion exchange polymer characterized in that the anion exchange polymer comprises a β-hydrogen that does not form an anti-periplanar conformation inside a quinuclidinium cage.

6. An anion exchange membrane comprising an anion exchange polymer according to any one of claims 1 to 5.

7. A membrane-electrode assembly comprising an anion exchange membrane according to paragraph 6.

8. A water electrolysis system comprising an anion exchange membrane according to Article 6.

9. Step (S01) of synthesizing a quinuclidine monomer by reacting a quinuclidine precursor, an organic acid, a catalyst, and a solvent; After step S01, a step (S02) of synthesizing a poly(arylene quinuclidine) polymer by polycondensation reaction using the quinuclidine monomer, arylene compound, and superacid catalyst; and A method for producing an anion exchange polymer, comprising a step (S03) of forming a quaternary ammonium salt by a Menshutkin reaction using the quinuclidine polymer and an alkyl halide after step S02 to synthesize a poly(arylene quinuclidinium) polymer.

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