An anion exchange polymer comprising a 4-x-quinuclidinium structure, a method for preparing the same, and an anion exchange membrane comprising the same

Abstract

The anion exchange polymer according to the preferred embodiment of the present application includes a 4-X-quinuclidinium structure in which carbon of No. 4 position of a quinuclidinium ring is connected to a main chain (X) of a polymer, and β-hydrogen in the quinuclidinium ring is not in an anti-periplanar conformation with a nitrogen atom, so that a Hofmann elimination reaction does not occur. Thus, it has an effect of having a stable chemical structure in an alkaline driving environment.

Description

Technical Field

[0001] This invention relates to an anion exchange membrane, specifically, to an anion exchange membrane comprising an anion exchange polymer having an excellent alkali stability of 4-X-quinuclidinium and a method for preparing the same. Background Technology

[0002] Anion exchange membranes (AEMs) are polymeric membranes that function as electrolytes, selectively transferring anions (primarily OH-) in electrochemical systems. - Cl - ,Br - The membrane, which allows anions to move within a positively charged polymer structure, plays a crucial role in energy conversion. It is used in various energy conversion devices, including AEM fuel cells (AEMFC), water electrolysis systems (AEMWE), redox flow batteries (RFB), and reverse electrodialysis (RED), selectively transferring anions. In such energy devices, the performance of the AEM largely depends on its conductivity and stability; therefore, stability under alkaline conditions is essential.

[0003] In recent years, research has been actively underway to develop chemically stable polymers containing cationic functional groups that are chemically stable under alkaline conditions. To date, studies have utilized cationic functional groups such as piperidinium, imidazolium, and trimethylammonium (TMA) for application in alkaline environments. However, these structures, especially when exposed to alkaline environments, may be susceptible to OH-. - Chemical decomposition occurs due to attack by anions, and this chemical instability can be a factor limiting the long-term performance of fuel cells and water electrolysis systems. Summary of the Invention

[0004] The problem that the invention aims to solve This invention addresses the aforementioned problems by providing an anion exchange polymer with a stable chemical structure under alkaline conditions and its preparation method. In particular, it provides an anion exchange polymer with excellent alkaline stability due to the strong resistance to Hofmann elimination reactions caused by the non-formation of anti-periplanar conformation of β-hydrogen.

[0005] The technical problems of this invention are not limited to those mentioned above. Those skilled in the art can clearly understand other technical problems not mentioned through the following description.

[0006] means for solving problems In order to achieve the above-mentioned technical problem, the anion exchange polymer according to a preferred embodiment of the present invention may contain a 4-X-quinuclidinium structure, as shown in the following chemical formula 1, in which the carbon at the 4th position of the quinuclidinium ring is connected to the polymer backbone (X). [Chemical Formula 1]

[0007] In the chemical formula 1, X comprises a repeating unit or aryl compound as shown in 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; [Chemical Formula 2]

[0008] In the chemical formula 2, Ar contains aryl compounds, Y contains hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6) or derivatives thereof, L contains C1 to C10 alkyl, C1 to C10 aryl, derivatives thereof or combinations thereof, n is an integer greater than or equal to 1, and x is an integer greater than or equal to 0.

[0009] Furthermore, in chemical formula 2, the position indicated by the wavy line can be connected to the X in chemical formula 1.

[0010] The anion exchange polymer may contain repeating units as shown in Chemical Formula 3 below; [Chemical Formula 3]

[0011] In the chemical formula 3, Ar1 contains an aryl compound, L1 contains 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.

[0012] The anion exchange polymer may contain repeating units as shown in Chemical Formula 4 below; [Chemical Formula 4]

[0013] In the chemical formula 4, Ar2 contains aryl compounds, and n is an integer greater than or equal to 1.

[0014] The anion exchange polymer may contain a repeating poly(arylene-4-(N-methyl-quinuclidinium))trifluoromethyl structure.

[0015] The anion exchange polymer is characterized by containing β-hydrogens that do not form an anti-periplanar conformation within the quinuclidinium cage.

[0016] To address the aforementioned technical issues, an anion exchange membrane according to a preferred embodiment of the present invention may comprise the anion exchange polymer.

[0017] To address the aforementioned technical issues, a membrane electrode assembly according to a preferred embodiment of the present invention may include the anion exchange polymer.

[0018] To address the aforementioned technical issues, a water electrolysis system according to a preferred embodiment of the present invention may include the anion exchange polymer.

[0019] To address the aforementioned technical problems, a preferred embodiment of the method for preparing anion exchange polymer according to the present invention may include the following steps: reacting a quinine ring precursor, an organic acid, a catalyst, and a solvent to synthesize a quinine ring monomer (S01); after step S01, using the quinine ring monomer, an arylene compound, and a superacid catalyst to perform a polycondensation reaction to synthesize a poly(arylene quinuclidine) polymer (S02); and after step S02, using the quinine ring polymer and an alkyl halide, forming a quaternary ammonium salt via a Menshutkin reaction to synthesize a poly(arylene quinuclidine) polymer (S03).

[0020] Invention Effects According to the present invention as described above, the following effects are achieved: In the anion exchange polymer of the preferred embodiment of the present invention, since β-hydrogen does not form an anti-periplanar conformation, it has strong resistance to the Hofmann elimination reaction, and therefore has a stable chemical structure under alkaline driving environment.

[0021] The effects of the present invention are not limited to those mentioned above, but also include other effects that are clearly understood by those skilled in the art based on the entire description but are not explicitly mentioned. Attached Figure Description

[0022] Figure 1 This relates to the structure of quinuclidinium and the three-dimensional chemical structure of piperidinium according to an embodiment of the present invention (Source: L. Yin et al., Angew. Chem. Int. Ed., 63, e202400764-e202400773, 2024).

[0023] Figure 2 The chemical structure of 1-X-quinuclidinium (1-X-qui) and 4-X-quinuclidinium (4-X-qui) according to an embodiment of the present invention indicates the binding position of β-hydrogen (marked by a red arrow).

[0024] Figure 3This is a flowchart illustrating the synthesis steps of an anion exchange polymer containing a 4-X-quinuclidinium structure according to an embodiment of the present invention. Detailed Implementation

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The advantages, features, and methods of achieving the present invention will become apparent from the accompanying drawings and the detailed embodiments described below. However, the present invention is not limited to the embodiments disclosed below and can be implemented in different ways. These embodiments are provided merely to complete the disclosure of the present invention and to fully inform those skilled in the art of the scope of the invention, which is defined only by the scope of the claims. Throughout this specification, the same reference numerals refer to the same components.

[0026] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) are to be used in the sense commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, terms already defined in commonly used dictionaries should not be idealized or over-interpreted unless explicitly and specifically defined. The terminology used in this specification is for illustrative purposes only and is not intended to limit the invention. In this specification, the singular form also includes the plural form unless specifically mentioned in the context.

[0027] The use of “comprises” and / or “comprising” in this specification does not exclude the presence or addition of more than one other component, step, action and / or element besides those mentioned.

[0028] Anion exchange polymers containing the 4-X-quinuclidinium structure An anion exchange polymer according to one embodiment of the present invention may contain a 4-X-quinuclidinium structure in which the 4-position of the quinuclidinium ring is connected to the polymer backbone (X).

[0029] [Chemical Formula 1]

[0030] In the chemical formula 1, X comprises a repeating unit or aryl compound as shown in 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.

[0031] At this time, the anion can be hydroxide ion (OH-). - (The mark can be omitted.)

[0032] In the chemical formula 1, quinuclidinium is the cationic form of quinuclidine and can be a compound with a bicyclic structure. This structure contains a nitrogen (N) atom shared by both rings and can have an ABCO (1-azabicyclo[2.2.2]octane) skeleton. In such a quinuclidinium structure, the nitrogen atom is positively charged through quaternization and can contain various substituents (R1) bonded to the nitrogen atom position.

[0033] The quinuclidinium can be contained as a polymeric side chain, particularly the carbon atom at position 4 of the quinuclidinium ring, which can be connected to the polymer backbone (X). In this case, the carbon atom at position 4 of the quinuclidinium ring can refer to the third carbon atom from the nitrogen (N) atom. Specifically, nitrogen (N) corresponds to position 1 of the quinuclidinium ring, and the carbon atom thereon can be the third carbon atom connected to that position, i.e., the carbon atom at position 4 of the quinuclidinium ring.

[0034] The carbon at position 4 of the quinuclidinium ring can form a reaction sp. 3 The hybrid tetrahedral framework, with carbons at position 4 maintaining a bond angle of 109.5 degrees and exhibiting high symmetry through a bicyclic structure, contributes to an overall balanced chemical structure. This structure mitigates physical stresses that may arise during polymer formation and minimizes distortion. Consequently, the carbon at position 4 of the quinuclidinium ring provides both chemical stability and structural strength.

[0035] In particular, when the quinuclidine ring is contained in the polymer structure as a polymeric side chain, it forms a bicyclic cage, resulting in higher structural rigidity and less distortion, which can improve the chemical stability of the polymer. Furthermore, in the quinuclidine structure of the polymer structure, the β-hydrogen does not form an anti-periplanar conformation, thus exhibiting lower sensitivity to Hofmann elimination reactions and relative stability. Conversely, the piperidinium structure is easily decomposed under alkaline conditions due to the elimination of β-hydrogen; therefore, compared to the quinuclidine structure, piperidinium may have relatively lower chemical stability.

[0036] X may contain repeating units or aryl compounds as shown in Chemical Formula 2 below.

[0037] Specifically, X may include repeating units as shown in Chemical Formula 2 below.

[0038] [Chemical Formula 2]

[0039] In the chemical formula 2, Ar contains aryl compounds, Y contains hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6) or derivatives thereof, L contains C1 to C10 alkyl, C1 to C10 aryl, derivatives thereof or combinations thereof, n is an integer greater than or equal to 1, and x is an integer greater than or equal to 0.

[0040] Furthermore, in chemical formula 2, the position indicated by the wavy line can be connected to the X in chemical formula 1.

[0041] The L is a spacer group contained in the polymer side chain, which may include C1 to C10 alkyl groups, C1 to C10 aryl groups, their derivatives, or combinations thereof. Specifically, the L may include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, methoxy, ethoxy, phenyl, benzyl, phenethyl, phenylpropyl, phenoxy, methoxybenzene, biphenyl, triphenyl, tetraphenyl, their derivatives, or combinations thereof.

[0042] Specifically, Y may contain hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6), or derivatives thereof. In one specific example, Y may contain trifluoromethyl (-CF3), but is not limited thereto. When Y contains trifluoromethyl (-CF3), the synthesized polymer can be endowed with characteristics such as hydrophobicity, electron withdrawing effect, enhanced thermal stability, and chemical resistance.

[0043] The spacer group (L) serves to prevent distortion of the quinuclidinium cage. In particular, when the quinuclidinium structure is directly linked to two phenyl groups within the polymer backbone, structural instability of the quinuclidinium ring may occur. Therefore, using a suitable spacer group (L) can alleviate this structural distortion and improve the chemical durability of the anion exchange polymer. The spacer group (L) functions by ensuring space between the quinuclidinium cage structure and the phenyl groups to relieve structural stress and maintain the binding flexibility within the polymer.

[0044] Furthermore, the spacer group (L) facilitates phase saparation, whereby within the anion exchange polymer, the hydrophobic polymer backbone (X) portion is physically separated from the hydrophilic polymer side chain (4-X-quinuclidinium structure) portion, and the phases are distinguished and separated from each other. This allows the hydrophilic groups (4-X-quinuclidinium structure) to aggregate, effectively forming anion mobility channels within the anion exchange polymer, thereby improving ionic conductivity.

[0045] The arylene compound (Ar) is a polymeric compound composed of repeating aromatic rings, such as aryl groups or arylene units. Each arylene unit typically originates from a benzene ring (C6H6) or other aromatic compounds, and they can be interconnected via carbon-carbon (CC) bonds, ether (O) bonds, or amine (N) bonds. For example, it can include polymeric structures formed by aryl groups interconnected via carbon-carbon bonds, ether bonds (-O-), or amine bonds (-NH-), such as polyphenylene (PP), polyphenylene ether (PPE), and polyphenylene amine. Arylene structures composed of multiple aromatic rings can exhibit properties such as high thermal stability, high mechanical strength, and excellent chemical resistance.

[0046] Specifically, the aryl compound (Ar) may comprise any one of the compounds or derivatives thereof selected from the compounds shown in the following structural formulas:

[0047]

[0048] Among them, R3 to R 11 Each can independently contain hydrogen, C1 to C10 alkyl groups, C1 to C10 aryl groups, or their derivatives, and a can be an integer greater than 1.

[0049] Furthermore, X may not be the arylene compound (Ar) contained in the repeating unit shown in Formula 2, but rather the arylene compound itself, or an arylene compound whose chemical structure contains a spacer group (L). In this case, the X may be located at the R site of the arylene compound, for example, R3 to R... 11 The site contains the 4-X-quinuclidinium structure of Formula 1, or it may contain the 4-X-quinuclidinium structure of Formula 1 in a manner attached to a spacer group (L) connected to a portion of the chemical structure of the aryl compound.

[0050] Specifically, the anion exchange polymer may contain repeating units as shown in Formula 3 below. More specifically, the anion exchange polymer may contain a poly(arylene-4-(N-quinuclidinium))trifluoromethyl structure.

[0051] [Chemical Formula 3]

[0052] In the chemical formula 3, Ar1 contains an aryl compound, L1 contains 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.

[0053] More specifically, the anion exchange polymer may contain repeating units represented by Chemical Formula 4 below. The anion exchange polymer may contain poly(arylene-4-(N-methyl-quinuclidinium))trifluoromethyl as repeating units.

[0054] [Chemical Formula 4]

[0055] In the chemical formula 4, Ar2 contains aryl compounds, and n is an integer greater than or equal to 1.

[0056] Figure 1 This relates to the structure of quinuclidinium and the three-dimensional chemical structure of piperidinium according to an embodiment of the present invention (Source: L. Yin et al., Angew. Chem. Int. Ed., 63, e202400764-e202400773, 2024).

[0057] Piperidinium has a hexagonal, double-bonded, six-membered ring structure. Based on this structure, its chemical structure continuously undergoes flipping between boat and chair conformations. In the chair conformation, the nitrogen atom and the β-hydrogen atom in the axial position are in anti-periplanar conformation, potentially leading to Hofmann elimination (E2 elimination). As a result, the piperidinium ring readily decomposes in alkaline environments, reducing its chemical stability. Conversely, structures based on the quinuclidine ring do not exhibit boat and chair conformations and, due to their unique bicyclic cage morphology, lack the β-hydrogen atom in anti-periplanar conformation. Thanks to this structural feature, the quinuclidine-based structure is resistant to Hofmann elimination and exhibits greater chemical stability in alkaline environments.

[0058] Figure 2 The chemical structures of 1-X-quinuclidinium (1-X-qui) and 4-X-quinuclidinium (4-X-qui) according to an embodiment of the present invention are shown with the binding positions of β-hydrogen (marked by red arrows).

[0059] Reference Figure 2It can be confirmed that in the 1-X-qui structure, the nitrogen atom is directly bonded to the alkyl chain, therefore the β-hydrogen atoms exist outside the quinuclidinium cage. Conversely, in the 4-X-qui structure, the β-hydrogen atoms exist only inside the quinuclidinium cage. Specifically, in the 1-X-qui structure, there are 6 β-hydrogen atoms inside the quinuclidinium cage (hydrogen atoms bonded to the carbon atoms marked as stable in the 1-X-qui structure), and 2 additional β-hydrogen atoms (hydrogen atoms bonded to the carbon atoms marked as unstable in the 1-X-qui structure) exist on the alkyl chain outside the quinuclidinium cage. The β-hydrogen atoms inside the quinuclidinium cage do not form an anti-periplanar conformation and are relatively stable, while the β-hydrogen atoms on the outside are susceptible to OH radicals. - The 1-X-qui structure is vulnerable to ion attack. Therefore, it is highly likely to decompose in an alkaline environment.

[0060] In contrast, the 4-X-qui structure possesses a structure that compensates for this vulnerability. The 4-X-qui structure exhibits enhanced resistance to Hoffmann elimination reactions due to the absence of β-hydrogens outside the quinuclidinium cage. In the 4-X-qui structure, all β-hydrogens exist only inside the quinuclidinium cage (hydrogens bonded to the carbons labeled as stable in 4-X-qui), and they do not form anti-periplanar conformations, thus maintaining stability even under alkaline conditions. Therefore, the 4-X-qui structure offers significantly superior stability under alkaline conditions compared to 1-X-qui, enabling it to function more effectively in various applications requiring both high temperatures and alkaline conditions.

[0061] [Chemical Formula 5]

[0062] Furthermore, the 3-X-quinuclidinium (3-X-qui) structure (chemical formula 5) is not bilaterally symmetrical, making its bond angles prone to distortion in the presence of bulky groups nearby. This distortion can impair the excellent alkali stability inherent in the quinuclidinium ring, reducing the polymer's chemical resistance and durability, and potentially leading to a significant decrease in its performance under alkaline conditions. Conversely, the 4-X-quinuclidinium (4-X-qui) structure is bilaterally symmetrical, minimizing structural distortion and improving structural stability and ionic conductivity.

[0063] Preparation method of anion exchange polymer containing 4-X-quinuclidinium structure Figure 3 The following reaction formulas 1 to 3 are flowcharts and reaction formulas representing the synthesis steps of an anion exchange polymer containing a 4-X-quinuclidinium structure according to an embodiment of the present invention.

[0064] [Reaction Formula 1]

[0065] [Reaction 2]

[0066] [Reaction 3]

[0067] In the above reactions 1 to 3, Ar contains aryl compounds, and R 12 Y2 is hydrogen, a C1 to C20 alkyl group, a C1 to C20 aryl group, or a derivative thereof; Y2 contains hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6), or a derivative thereof; A is a C1 to C3 alkyl group; n is an integer greater than or equal to 1; and X' is a halogen element.

[0068] Reference Figure 3 In addition to reactions 1 to 3, the following steps (S01) can be performed first: react the quinine ring precursor, organic acid, catalyst and solvent to synthesize the quinine ring monomer.

[0069] The quinuclidine ring precursor may comprise a quinuclidine compound containing a carboxylic moiety. Specifically, the quinuclidine ring precursor may be a compound containing a carboxylic moiety at the 4-position carbon of the quinuclidine bicyclic ring.

[0070] Specifically, the quinine ring precursor may comprise a compound represented by the following chemical formula 6, its salt, or its hydrate.

[0071] [Chemical Formula 6]

[0072] In the above chemical formula 6, R 12 It is hydrogen, a C1 to C20 alkyl group, a C1 to C20 aryl group, or a derivative thereof.

[0073] In one specific example, the quinine ring precursor may comprise quinuclidine-4-carboxylic acid, but is not limited thereto.

[0074] Furthermore, the organic acid can react with the OH group in the carboxylic moiety of the quinine ring precursor to introduce an acyl group (-COR). Specifically, the organic acid may include non-fluorinated organic acids, fluorinated organic acids, their anhydrides, or combinations thereof. For example, it may include: non-fluorinated organic acids comprising acetic anhydride, propionic anhydride, butyric anhydride, benzoic anhydride, and maleic anhydride; fluorinated organic acids comprising trifluoroacetic anhydride (TFAA), pentafluoropropionic anhydride, and pentafluorobenzoic anhydride; or combinations thereof. More specifically, the organic acid may be a fluorinated organic acid, and in one specific example, may include trifluoroacetic anhydride (TFAA), but is not limited thereto.

[0075] The catalyst can be used as both a catalyst and an organic solvent in the reaction of Formula 1. For example, the catalyst may comprise any one selected from pyridine, 4-dimethylaminopyridine (DMAP), triethylamine (TEA), N,N-dimethylaniline, triisopropylamine (TIPA), and combinations thereof. In one specific example, the catalyst may comprise pyridine, but is not limited thereto.

[0076] The solvent may be a polar solvent, for example, it may contain 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 contain water, but is not limited thereto.

[0077] The catalyst and the solvent can induce or promote the hydrolysis and decarboxylation reactions of the reactants.

[0078] Next, the following step (S02) can be performed: a polycondensation reaction is carried out using the quinine ring monomer, the arylene compound and the superacid catalyst to synthesize a poly(arylenequinuclidine) polymer.

[0079] The synthesized quinine ring monomer may contain compounds represented by the following chemical formula 7, their salts, or their hydrates.

[0080] [Chemical Formula 7]

[0081] In the chemical formula 7, Y2 may contain hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6), or derivatives thereof.

[0082] Specifically, the quinine ring monomer may comprise quinuclidine-4-carboxaldehyde, quinuclidine-4-acetyl, quinuclidine-4-propionyl, quinuclidine-4-methoxycarbonyl, quinuclidine-4-ethoxycarbonyl, and quinuclidine-4-benzoyl. The monomer may contain nuclidine-4-benzoyl, quinuclidine-4-benzylcarbonyl, quinuclidine-4-trifluoroacetyl, quinuclidine-4-trifluoromethoxycarbonyl, quinuclidine-4-hexafluoroethoxycarbonyl, or derivatives thereof. In one specific example, the quinine ring monomer may contain, but is not limited to, quinuclidine-4-trifluoroacetyl.

[0083] The aryl compound may comprise any one of the compounds or their derivatives selected from the compounds shown in the following structural formulas:

[0084]

[0085] Among them, R3 to R 11 Each can independently contain hydrogen, C1 to C10 alkyl groups, C1 to C10 aryl groups, or their derivatives, and a can be an integer greater than 1.

[0086] The superacid catalyst, due to its extremely strong acidity, promotes the formation and bonding of polymer chains and can be a compound used in a polycondensation reaction. Specifically, the polymerization reaction is a Friedel-Crafts polycondensation reaction, which can be a polyhydroxyalkylation reaction using an acetic acid catalyst.

[0087] Specifically, the superacid catalyst may comprise 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 comprise trifluoromethanesulfonic acid (TFSA), but is not limited thereto.

[0088] The polymer synthesized by the polycondensation reaction may contain a poly(arylene quinuclidine) polymer as shown in Formula 8 below.

[0089] [Chemical Formula 8]

[0090] In the chemical formula 8, Ar3 contains aryl compounds, Y2 contains hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6) or derivatives thereof, and n can be an integer greater than or equal to 1.

[0091] Next, after the polymerization is completed, the following step (S03) can be performed: using the quinine cyclic polymer and alkyl halide, a quaternary ammonium salt is formed through the Menshutkin reaction, thereby synthesizing a poly(arylene quinuclidinium) polymer.

[0092] 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 can refer to a reaction following a nucleophilic substitution reaction (SN2 mechanism), where the nitrogen atom of the nucleophilic amine combines with the alkyl group of the alkyl halide, simultaneously losing a halogen atom. Specifically, when the Menshutkin reaction occurs on the bicyclic structure of quinuclidine, the following process occurs: the nitrogen (N) atom of the tertiary amine containing a lone pair of electrons, i.e., the quinuclidine ring, reacts with an alkyl halide, such as methyl iodoforme (CH3I or MeI), acquiring a positive charge and forming a quaternary ammonium compound. The quaternized quinuclidine ring, represented as quinuclidinium, acts as an anion transporter in anion exchange polymers.

[0093] Anion exchange polymers comprising the poly(arylenequinuclidinium) polymer after quaternization may comprise polymers shown in Formula 9 below.

[0094] [Chemical Formula 9]

[0095] In the chemical formula 9, Ar3 contains aryl compounds, Y2 contains hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6) or derivatives thereof, and n can be an integer greater than or equal to 1.

[0096] The present invention will now be described in more detail through examples and comparative examples. However, the following examples and comparative examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

[0097] Preparation Example 1: Polyarylene-4-(N-methyl-quininecyclohexane)trifluoromethyl (Poly(arylene-4-(N-) Synthesis of methyl-quinuclidinium (trifluoromethyl) anion exchange polymer (4-X-qui) The following reactions 4 to 6 illustrate the synthesis steps of an anion exchange polymer based on poly(arylene-4-(N-methyl-quinuclidinium))trifluoromethyl according to an embodiment of the present invention.

[0098] [Reaction 4]

[0099] [Reaction 5]

[0100] [Reaction Formula 6]

[0101] In reactions 4 to 6, Ar4 contains aryl compounds and n is an integer greater than or equal to 1.

[0102] First, quinuclidine-4-carboxylic acid is dissolved in toluene and then reacted with trifluoroacetic anhydride (TFAA) to synthesize the monomer quinuclidine-4-trifluoroacetate by replacing the carboxylic moiety with a trifluoroacetyl group. During this process, pyridine and water (H₂O) induce hydrolysis and decarboxylation of the reactants.

[0103] Subsequently, the synthesized monomers and aryl compounds were dissolved in dichloromethane (DCM) and then reacted with trifluoromethanesulfonic acid (TFSA) to polymerize the polymer through a Friedel-Crafts polycondensation reaction, i.e., a polyhydroxyalkylation reaction using acetic acid catalyst.

[0104] After polymerization, the polymer is reacted with iodomethane (MeI) to undergo quaternization via the Menshutkin reaction. This ultimately synthesizes anion-exchange polymer based on poly(arylene quinuclidinium).

[0105] Example 1: Containing polyarylene-4-(N-methyl-quininecyclohexane)trifluoromethyl (Poly(arylene-4-(N-) Anion exchange membrane (4-X-qui) containing methyl-quinuclidinium and trifluoromethyl. Anion exchange membranes were prepared using the poly(arylene-4-(N-methyl-quinuclidinium))trifluoromethyl anion exchange polymer (4-X-qui) of chemical formula 10 obtained from Preparation Example 1.

[0106] [Chemical Formula 10]

[0107] In the chemical formula 10, Ar4 contains aryl compounds, and n is an integer greater than or equal to 1.

[0108] Comparative Example 1: Containing polyarylene-1-(N-quininecyclohexane)trifluoromethyl (Poly(arylene-1-(N-) Anion exchange membrane of quinuclidinium (trifluoromethyl) (1-X-qui) Anion exchange membranes were prepared using the poly(arylene-1-(N-quinuclidinium))trifluoromethyl anion exchange polymer (1-X-qui) shown in Formula 11 below.

[0109] [Chemical Formula 11]

[0110] In the chemical formula 11, Ar5 contains aryl compounds, L2 contains C1 to C10 alkyl groups, C1 to C10 aryl groups, their derivatives, or combinations thereof, n is an integer greater than or equal to 1, and x' is an integer greater than or equal to 0.

[0111] When comparing the properties of the anion exchange membranes of Example 1 and Comparative Example 1 according to the present invention, in the case of the 1-X-qui structure (Comparative Example 1), the N atom of the quinuclidinium ring is directly attached to the polymer side chain, resulting in β-hydrogen atoms existing outside the quinuclidinium cage. The externally located β-hydrogen atoms may be susceptible to OH-. - The 1-X-qui structure (Comparative Example 1) is vulnerable to ion attack, making it more likely to decompose in alkaline environments. Conversely, in the case of the 4-X-qui structure (Example 1), the β-hydrogen atoms exist only within the quinuclidinium cage, thus all β-hydrogen atoms do not form anti-periplanar conformations with nitrogen atoms, resulting in relative stability even in alkaline environments. Therefore, the 4-X-qui structure (Example 1) provides significantly better stability in alkaline environments than the 1-X-qui structure (Comparative Example 1), and offers a structure more suitable for various applications requiring high temperatures and alkaline conditions.

[0112] Comparative Example 2: Containing polyarylene-3-(N-methyl-quininecyclohexane)(3-Poly(arylene-3-(N-methyl- anion exchange membrane of quinuclidinium Anion exchange membranes were prepared using the polyarylene-3-(N-methyl-quinuclidinium) anion exchange polymer shown in Formula 12 below.

[0113] [Chemical Formula 12]

[0114] In the chemical formula 12, Ar6 is an aryl compound, and n is an integer greater than or equal to 1.

[0115] When comparing the properties of the anion exchange membranes of Example 1 and Comparative Example 2 according to the present invention, in the case of Comparative Example 2, due to the structural characteristic that the flanks of the quinuclidinium ring are directly connected to the aromatic rings of the polymer backbone, the possibility of bicyclic distortion is higher, which may reduce the alkali stability of the polymer. Conversely, in the case of the 4-X-qui structure (Example 1), there is a structural characteristic that it is not directly connected to the phenyl ring of the polymer backbone, but rather through spacer groups, and thus does not undergo distortion substantially. Therefore, compared to Comparative Example 2, the 4-X-qui structure (Example 1) can improve alkali stability.

[0116] Comparative Example 3: Contains polyarylene-4-(N,N-dimethylpiperidinium)trifluoromethyl (Poly(arylene-4-(N,N-dimethylpiperidinium)trifluoromethyl) N-dimethyl piperidinium) trifluoromethyl) anion exchange membrane Anion exchange membranes were prepared using the poly(arylene-4-(N,N-dimethylpiperidinium))trifluoromethyl anion exchange polymer shown in Formula 13 below.

[0117] [Chemical Formula 13]

[0118] In the chemical formula 13, Ar7 contains aryl compounds, L3 contains C1 to C10 alkyl groups, C1 to C10 aryl groups, their derivatives, or combinations thereof, n is an integer greater than or equal to 1, and x" is an integer greater than or equal to 0.

[0119] When comparing the properties of the anion exchange membranes of Example 1 and Comparative Example 3 according to the present invention, Comparative Example 3 is characterized by the presence of a piperidinium ring structure in the polymer side chain. This piperidinium-based structure continuously flips between boat and chair conformations in its chemical structure. During this process, when the chair conformation is formed, the nitrogen atom in the ring is in an anti-periplanar position with the axially located β-hydrogen, thereby promoting the Hofmann elimination (E2 elimination) reaction. As a result, the piperidinium ring is easily decomposed under alkaline conditions, and its chemical stability decreases. Conversely, in the case of the 4-X-qui structure (Example 1), it has the structural characteristic of not forming an anti-periplanar conformation due to the bicyclic cage morphology based on the quinuclidine ring, and therefore is resistant to the Hofmann elimination reaction and has higher chemical stability even in alkaline environments.

[0120] Comparative Example 4: Containing poly(arylene-4-(N,N-dimethylpiperidinium)) dimethyl piperidinium anion exchange membrane Anion exchange membranes were prepared using the poly(arylene-4-(N,N-dimethylpiperidinium)) anion exchange polymer shown in Formula 14 below.

[0121] [Chemical Formula 14]

[0122] In the chemical formula 14, Ar8 is an aryl compound, and n is an integer greater than or equal to 1.

[0123] When comparing the properties of the anion exchange membranes of Example 1 and Comparative Example 4 according to the present invention, in the case of Comparative Example 4, the carbon in the piperidinium ring is directly connected to the polymer backbone. This structural characteristic causes distortion of the hexacyclic structure, increasing structural instability. Conversely, in the case of the 4-X-qui structure (Example 1), it has the structural characteristic that not only is it not directly connected to the phenyl ring of the polymer backbone, but also, due to its inherent bicyclic cage morphology, it avoids the Hoffmann elimination reaction.

[0124] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, those skilled in the art will understand that the invention can be implemented in other specific ways without changing the technical concept or essential features of the invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims

1. An anion exchange polymer, wherein, The anion exchange polymer comprises a 4-X-quinuclidinium structure, as shown in Formula 1 below, in which the carbon at position 4 of the quinuclidinium ring is connected to the polymer backbone (X). [Chemical Formula 1] In the chemical formula 1, X comprises a repeating unit or aryl compound as shown in 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 chemical formula 2, Ar contains aryl compounds, Y contains hydrogen, methyl (-CH3), ethyl (-C2H5), methoxy (-OCH3), ethoxy (-OC2H5), phenyl (-C6H5), benzyl (-CH2C6H5), trifluoromethyl (-CF3), trifluoromethoxy (-OCF3), hexafluoroethoxy (-OC2F6) or derivatives thereof, L contains C1 to C10 alkyl, C1 to C10 aryl, derivatives thereof or combinations thereof, n is an integer greater than or equal to 1, and x is an integer greater than or equal to 0.

2. The anion exchange polymer according to claim 1, wherein, The anion exchange polymer comprises repeating units as shown in Chemical Formula 3 below; [Chemical Formula 3] In the chemical formula 3, Ar1 contains an aryl compound, L1 contains a C1 to C10 alkyl, a C1 to C10 aryl, a derivative thereof, or a combination thereof, R2 is hydrogen, a C1 to C10 alkyl, a C1 to C10 alkoxy, a C1 to C10 aryl, 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. The anion exchange polymer according to claim 1, wherein, The anion exchange polymer comprises repeating units as shown in Chemical Formula 4 below; [Chemical Formula 4] In the chemical formula 4, Ar2 contains aryl compounds, and n is an integer greater than or equal to 1.

4. The anion exchange polymer according to claim 1, wherein, The anion exchange polymer contains a repeating poly(arylene-4-(N-methyl-quinuclidinium))trifluoromethyl structure.

5. The anion exchange polymer according to claim 1, wherein, The anion exchange polymer contains β-hydrogens that do not form an anti-periplanar conformation within the quinuclidinium cage.

6. An anion exchange membrane, wherein, The anion exchange membrane comprises the anion exchange polymer according to any one of claims 1 to 5.

7. A membrane electrode assembly, wherein, The membrane electrode assembly comprises the anion exchange membrane as described in claim 6.

8. A water electrolysis system, wherein, The water electrolysis system includes the anion exchange membrane as described in claim 6.

9. A method for preparing anion exchange polymer, wherein, The preparation method of the anion exchange polymer includes the following steps: The quinine ring precursor, organic acid, catalyst and solvent are reacted to synthesize the quinine ring monomer (SO1). Following step S01, a polycondensation reaction is carried out using the quinine ring monomer, the arylene compound, and a superacid catalyst to synthesize a poly(arylene quinuclidine) polymer (S02); and Following step S02, the quinine cyclopolymer and alkyl halide are used to form a quaternary ammonium salt via the Menshutkin reaction, thereby synthesizing a poly(arylenequinuclidinium) polymer (S03).

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