Cross-linked anion exchange membrane

Abstract

A cross-linked anion exchange membrane is provided. The cross-linked anion exchange membrane includes a crosslinking molecule and an organic polymer crosslinked with the crosslinking molecule. The crosslinking molecule has a specific bisimidazolium structure. Therefore, the cross-linked anion exchange membrane can have greater alkaline stability, dimensional stability and ionic conductivity, thereby increasing its applicability.

Description

Technical Field

[0001] This invention relates to a cross-linked anion exchange membrane, and more particularly to a cross-linked anion exchange membrane comprising cross-linked molecules having a bisimidazole onion structure. Prior Technology

[0002] Anion exchange membranes (AEMs) offer numerous advantages. For instance, they allow the use of non-precious metal catalysts instead of expensive platinum catalysts and lower-cost stainless steel bipolar plates, reducing the overall cost of the electrolyzer. Furthermore, the faster electrode reaction rates and lower permeability of AEMs make them more promising for applications in fuel cells and water electrolysis for hydrogen production.

[0003] However, conventional anion exchange membranes still have unresolved issues, particularly regarding alkaline stability, conductivity, and mechanical properties. Alkaline stability directly affects the lifespan of fuel cells and hydrogen production efficiency. The root cause of alkaline stability lies in the stability of the polymer structure and cation groups within the anion exchange membrane, which can lead to the deterioration of the membrane material in alkaline environments. Therefore, as the application of anion exchange membranes in alkaline environments gains increasing attention, improving their alkaline stability, conductivity, and mechanical properties has become a crucial research topic.

[0004] In view of this, there is an urgent need to provide an ion exchange membrane with better alkali stability, thereby improving its applicability. Summary of the Invention

[0005] One aspect of this invention is to provide an anion exchange membrane, which utilizes cross-linked molecules with specific structures to cross-link with organic polymers, thereby exhibiting high alkali stability and ion conductivity.

[0006] According to one aspect of the present invention, a cross-linked anion exchange membrane is provided, comprising cross-linked molecules and an organic polymer cross-linked with the cross-linked molecules. The cross-linked molecules include the structure shown in formula (I): (I).

[0007] In formula (I), the X series independently represents a bromine atom, a chlorine atom, or an iodine atom; the Y series independently represents an alkyl group with 1 to 8 carbon atoms, or a divalent organic group with 4 to 8 carbon atoms and an ether group; the Z series independently represents an alkyl group with 4 to 8 carbon atoms or a divalent organic group with an ether group; the R series independently represents a methyl group or an ethyl group; and n is any integer between 1 and 4.

[0008] According to one embodiment of the present invention, the above-mentioned cross-linked molecule comprises at least one of the following: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 , , , , , , , , , , , , , , , , .

[0009] According to one embodiment of the present invention, the above-mentioned organic polymer comprises polybenzimidazole, polybenzoxazole, polybenzothiazole, polyetherketone, polyphenylene ether, polyether pyrite, polypyrite, polyphenylene sulfide, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyphenylene chloride, branched polybenzimidazole, branched polybenzoxazole, branched polybenzothiazole, branched polyetherketone, branched polyphenylene ether, branched polyether pyrite, branched polypyrite, branched polyphenylene sulfide, or any combination thereof.

[0010] According to one embodiment of the present invention, the above-mentioned polybenzimidazole has the structure shown in formula (II): (II).

[0011] In formula (II), A represents a divalent organic group, and o represents any integer between 90 and 500.

[0012] According to one embodiment of the present invention, the above-mentioned branched polybenzimidazole has the structure shown in formula (III): (III).

[0013] In formula (III), A represents a divalent organic group, B represents -(CH2)2- or -CH2-O-CH2-, C represents a tertiary amino group, r represents any integer between 0 and 2, p represents any integer between 1 and 50, and q represents an integer of (100-p).

[0014] According to one embodiment of the present invention, the above-mentioned polystyrene comprises the structure shown in formula (IV): (IV).

[0015] In equation (IV), s represents any integer between 5 and 9, and t represents an integer of (10-s).

[0016] According to one embodiment of the present invention, the alkaline stability of the cross-linked anion exchange membrane is not less than 80%.

[0017] According to one embodiment of the present invention, the thickness of the cross-linked anion exchange membrane is 20 micrometers to 100 micrometers.

[0018] According to one embodiment of the present invention, the ion exchange capacity of the cross-linked anion exchange membrane is from 1.5 mmole / g to 2.2 mmol / g.

[0019] According to one embodiment of the present invention, the hydroxide ion conductivity of the above-mentioned anion exchange membrane at 30°C is not less than 0.030 S / cm, and the hydroxide ion conductivity at 80°C is not less than 0.072 S / cm.

[0020] The cross-linked anion exchange membrane of the present invention utilizes cross-linked molecules with a specific bisimidazole onion structure to cross-link with organic polymers, thereby giving the cross-linked anion exchange membrane higher alkali stability, dimensional stability and ionic conductivity, and thus improving its applicability. Simple Explanation of the Diagram

[0021] A better understanding of the features disclosed herein will be achieved by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, as is standard practice in the industry, many features are not drawn to scale. In fact, for clarity of discussion, the dimensions of many features may be arbitrarily scaled. Figures 1 and 2 are NMR spectra of cross-linked molecules according to some embodiments of the present invention. Implementation

[0022] The manufacture and use of embodiments of the present invention are discussed in detail below. However, it will be understood that the embodiments provide many applicable inventive concepts that can be implemented in a wide variety of specific contexts. The specific embodiments discussed are for illustrative purposes only and are not intended to limit the scope of the invention.

[0023] As used in this invention, "around," "about," "approximately," or "substantially" generally mean within 20 percent, 10 percent, or 5 percent of the stated value or range.

[0024] Crosslinking technology is an important method for improving the stability of proton exchange membranes (PEMs) or anion exchange membranes (AEMs), particularly in enhancing their ion exchange capacity and preventing water swelling. If the polymer of the exchange membrane is not crosslinked, it may exhibit extremely high swelling properties, leading to severe water absorption and dimensional deformation, thus affecting its mechanical properties. Therefore, to address these issues, during the crosslinking process, the cationic groups of the anion exchange membrane not only serve as anion conducting sites but also as crosslinking sites. This crosslinking method not only improves crosslinkability but also increases the number of hydrophilic cationic groups, thereby counteracting the effect of the crosslinked structure on reducing the membrane's water absorption. Furthermore, this crosslinking method can further reduce the hindrance of the crosslinked structure to ion migration, maintaining the ionic conductivity of the membrane and resulting in better stability during application.

[0025] As described above, the present invention provides a cross-linked anion exchange membrane, which utilizes cross-linked molecules with a specific bisimidazole onion structure to cross-link with organic polymers, thereby exhibiting high alkali stability, dimensional stability, and ionic conductivity, and thus improving its applicability.

[0026] The cross-linked anion exchange membrane of the present invention comprises cross-linked molecules and an organic polymer, wherein the cross-linked molecules are bonded to the side chains of the organic polymer to form a cross-linked structure.

[0027] In some embodiments, the cross-linked molecule includes the structure shown in formula (I): (I).

[0028] In formula (I), the X series independently represents a bromine atom, a chlorine atom, or an iodine atom; the Y series independently represents an alkyl group with 1 to 8 carbon atoms, or a divalent organic group with 4 to 8 carbon atoms and an ether group; the Z series independently represents an alkyl group with 4 to 8 carbon atoms or a divalent organic group with an ether group; the R series independently represents a methyl group or an ethyl group; and n is any integer between 1 and 4.

[0029] In some embodiments, Y in formula (I) represents an alkyl group (i.e., -(CH2)2-, -(CH2)4-, -(CH2)6-), -CH2(CH2OCH2)CH2- or -CH2(CH2OCH2)2CH2-) with 2, 4 or 6 carbon atoms.

[0030] In some embodiments, the cross-linked molecule may include at least one of the following: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 , , , , , , , , , , , , , , , , .

[0031] In some embodiments, the organic polymer includes, but is not limited to, polybenzimidazole, polybenzoxazole, polybenzothiazole, polyetherketone, polyphenylene ether, polyether pyrite, polypyrite, polyphenylene sulfide, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyphenylene chloride, branched polybenzimidazole, branched polybenzoxazole, branched polybenzothiazole, branched polyetherketone, branched polyphenylene ether, branched polyether pyrite, branched polypyrite, branched polyphenylene sulfide, or any combination thereof. The organic polymer may be used alone or in combination of two or more (e.g., three or four).

[0032] In some embodiments, the above-mentioned polybenzimidazole has the structure shown in formula (II): (II).

[0033] In formula (II), A represents a divalent organic group, and o represents any integer between 90 and 500.

[0034] In some specific examples, A can have the following structure: , , , , , , , , , , .

[0035] In some embodiments, the above-mentioned branched polybenzimidazole has the structure shown in formula (III): (III).

[0036] In formula (III), A represents a divalent organic group, B represents -(CH2)2- or -CH2-O-CH2-, C represents a tertiary amino group, r represents any integer between 0 and 2, p represents any integer between 1 and 50, and q represents an integer of (100-p).

[0037] It should be further noted that C is a tertiary amine group, so that the branched structure of formula (III) is a quaternary amine salt, thereby giving the main chain structure better hydrophilicity. In some embodiments, C may have the structure shown below, where "*" represents a bond: , , , , , , , , , , .

[0038] In some embodiments, the polystyrene described above comprises the structure shown in formula (IV): (IV).

[0039] In equation (IV), s represents any integer between 5 and 9, and t represents an integer of (10-s).

[0040] The method for manufacturing the aforementioned cross-linked anion exchange membrane includes coating a cross-linked anion exchange membrane precursor onto a substrate surface to form a coating film, wherein the cross-linked anion exchange membrane precursor comprises a colloidal mixture of the aforementioned organic polymer and cross-linked molecules in an organic solvent. In some embodiments, the aforementioned coating step may utilize common coating techniques such as blade coating, spin coating, or spray coating. Next, a heat treatment is performed to remove the organic solvent and to achieve the desired density of the cross-linked anion exchange membrane precursor. In some embodiments, the aforementioned heat treatment temperature is between 60°C and 250°C. In some specific examples, the heat treatment temperature may be, but is not limited to, 80°C, 100°C, 120°C, 150°C, 180°C, 210°C, or 230°C.

[0041] In some embodiments, the alkaline stability of the cross-linked anion exchange membrane is not less than 80%.

[0042] In some embodiments, the thickness of the cross-linked anion exchange membrane is from about 20 micrometers to about 100 micrometers. It should be understood that there is no particular limitation on the thickness of the cross-linked anion exchange membrane, which can be adjusted according to the application requirements.

[0043] In some embodiments, the ion exchange capacity (IEC) of the cross-linked anion exchange membrane is from 1.5 mmole / g to 2.2 mmol / g.

[0044] In some embodiments, the cross-linked anion exchange membrane has a hydroxide ion conductivity (σ) of not less than 0.030 S / cm at 30°C and a hydroxide ion conductivity (σ) of not less than 0.072 S / cm at 80°C.

[0045] The cross-linked anion exchange membrane provided by this invention is formed by cross-linking cross-linked molecules with bisimidazole onium groups with organic polymers. The cross-linked molecules with bisimidazole onium groups not only function as cross-linking agents but also contribute to the formation of comb-like ion conductors, thus effectively improving the conductivity of the cross-linked anion exchange membrane. The cross-linked anion exchange membrane of this invention exhibits properties significantly superior to conventional anion exchange membranes, while simultaneously possessing high conductivity and excellent dimensional stability. Furthermore, the cross-linked anion exchange membrane of this invention maintains high conductivity even under conditions of low ion exchange capacity and low hygroscopicity, indicating its stability (e.g., alkali stability) and performance under extreme environments. Therefore, the cross-linked anion exchange membrane of this invention can be applied to battery systems such as fuel cells, effectively improving its long-term operating efficiency and stability.

[0046] The following examples illustrate the application of the present invention, but they are not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention.

[0047] Preparation Example 1: Preparation of Polybenzimidazole

[0048] A 500 mL four-necked reaction flask was placed in a fume hood, and 230 g of polyphosphoric acid (PPA) (purchased from ARCOS) was added as a solvent. 3.2796 g of 3,3'-diaminobenzidine (purchased from TCI) and 6.0657 g of 2,2-bis(4-carboxyphenyl)-hexafluoropropane (purchased from TCI) were also added. Under nitrogen atmosphere, the reaction mixture was heated to 170°C to 220°C and mechanically stirred for 24 hours to carry out condensation polymerization. Before initiating the condensation polymerization reaction, a step-by-step heating method should be used to gradually increase the temperature to the desired range, while slow stirring to ensure that 3,3'-diaminobenzidine and 2,2-bis(4-carboxyphenyl)-hexafluoropropane are completely dissolved in polyphosphoric acid and react fully. This process should last approximately 12.5 hours. After synthesis, the resulting hexfluorine-containing polybenzimidazole (6FPBI) precursor polymer is precipitated from the solution. The precipitate is broken up and washed with a 2 wt% sodium hydroxide aqueous solution until the pH of the solution reaches 14. Subsequently, it is washed with a large amount of deionized water until neutral and then dried in a vacuum oven at 80°C to obtain a light brown coarse-grained powder.

[0049] Preparation Example 2: Preparation of Branched Polybenzimidazole

[0050] A 250 mL three-necked reaction flask was placed in a fume hood, and 1.068 g (0.002 mol) of 6FPBI was added and dissolved in dimethyl sulfoxide (DMSO). The reaction mixture was heated to 120°C and held at that temperature for 12 hours until the 6FPBI was completely dissolved. After the mixture cooled to room temperature, 0.128 g (0.0048 mol) of sodium hydride was added, and the mixture was allowed to turn dark black. The reaction mixture was then heated to 80°C and the reaction was continued for 24 hours to ensure complete reaction. Next, 22.8823 g (0.36 mol) of excess bis(2-chloroethyl) ether (purchased from Sigma-Aldrich Alfa) was added, and the mixture was stirred at 80°C under nitrogen atmosphere for 48 hours. After the reaction was complete, the polymer solution was transferred to acetone for precipitation, and the precipitate was dried at 70°C for 24 hours. Then, the precipitate was washed three times with deionized water and then placed in a vacuum oven and dried at 70°C for 24 hours to obtain the branched polybenzimidazole polymer.

[0051] Preparation Example 3: Preparation of Bisimilar Crosslinking Agent

[0052] A condenser was installed in a three-necked reaction flask. Under a nitrogen atmosphere and at room temperature, 0.02 mol of dried 2-methylimidazole was mixed with an appropriate amount of acetonitrile (ACN) solvent and stirred for 1 hour until the 2-methylimidazole (purchased from ARCOS) was completely dissolved. Then, a slightly excess of 0.04 mol of potassium hydroxide (KOH) was added to promote the dehydrogenation reaction of 2-methylimidazole, and stirring continued. When the reaction terminated and no more hydrogen bubbles were produced, the reaction temperature was maintained at room temperature, and 0.01 mol of 1,6-dibromohexane (purchased from TCI) was added dropwise, while stirring the reaction mixture for 24 hours. After the reaction was complete, the reaction mixture was extracted with chloroform and deionized water. The organic layer was separated and concentrated under reduced pressure to remove the solvent. Finally, the obtained product was placed in a vacuum oven and dried at 50°C for 24 hours to obtain the bisimidazole cross-linked molecule shown in the following formula: .

[0053] Preparation Example 4: Preparation of Poly(Styrene-Vinylphenyl Chloride-Dipolymer)

[0054] First, before the reaction, styrene (purchased from Alfa) and 4-vinylbenzyl chloride (purchased from Sigma-Aldrich) were passed three times separately through a column filled with basic alumina to remove inhibitors. Then, 10.963 g (0.105 mol) of styrene, 7.631 g (0.045 mol) of 4-vinylphenyl chloride, 0.082 g (0.0005 mol) of 2,2-azobis(2-methylpropionitrile) (AIBN), and 15 mL of toluene were sequentially added to a three-necked flask purged with dry nitrogen. The mixture was stirred at 60°C for 16 hours, then the temperature was increased to 70°C and the reaction continued for 2 hours, or until the stir bar could no longer be used. After the reaction was complete, the reaction solution was poured into a large amount of methanol for precipitation. The precipitate was broken up and washed three times with methanol, followed by vacuum filtration. Finally, the filtered product was placed in a vacuum oven and dried at 50°C overnight to obtain a white poly(styrene-vinylphenyl chloride-dipolymer) powder. The molar ratio of styrene to 4-vinylphenyl chloride in this copolymer was 7:3.

[0055] Example 1

[0056] 0.3 g of polystyrene polymer powder was dissolved in 15 mL of dimethylformamide (DMF) to form a 2 wt% polymer solution. Crosslinking molecules (as shown in Table 1) were then added at room temperature and mixed at a specific molar ratio (polystyrene:crosslinking molecule ratio 1:1). The mixture was stirred until completely dissolved, forming a colloidal mixture. This colloidal mixture was coated onto a glass substrate, forming a film with a thickness of 800 μm. A pre-crosslinking reaction was carried out overnight at 60 °C. The next day, the temperature was raised to 80 °C, and the solution was slowly extracted under vacuum. The temperature was then raised to 100 °C and left overnight. Finally, the glass substrate was added to deionized water for membrane removal, yielding a crosslinked anion exchange membrane with a thickness of 40 μm.

[0057] Examples 2 to 4

[0058] Examples 2 to 4 were prepared using the same method as in Example 1 to obtain cross-linked anion exchange membranes, the difference being the types of cross-linking molecules used. The cross-linking molecules used in Examples 2 to 4 are listed in Table 1 below.

[0059] Example 5

[0060] Using a mixer, 20 g of branched polybenzimidazole and 180 g of N-methylpyrrolidone were stirred at 120 °C and 1 atm for 24 hours until completely dissolved, forming a 10 wt% polymer solution. Crosslinking molecules (as shown in Table 1) were then added at room temperature and mixed at a specific molar ratio (polybenzimidazole:crosslinking molecule ratio 1:1). The mixture was stirred until completely dissolved, forming a colloidal mixture. This colloidal mixture was coated onto a glass substrate, forming a film with a thickness of 800 μm. The film was then heat-treated by drying at a temperature range of 60 °C to 125 °C for 60 minutes, followed by curing at 250 °C for 1 hour, yielding a crosslinked anion exchange membrane with a thickness of 40 μm.

[0061] Example 6

[0062] Example 6 uses the same method as Example 5 to prepare a cross-linked anion exchange membrane, the difference being the types of cross-linked molecules used. The cross-linked molecules used in Example 6 are listed in Table 1 below.

[0063] Comparative Examples 1 to 3

[0064] Comparative Examples 1 to 3 were all cross-linked anion exchange membranes prepared according to Korean Patent KR 101766577B1. The cross-linked molecules used in Comparative Examples 1 to 3 are listed in Table 1 below.

[0065] Evaluation method

[0066] Nuclear magnetic resonance (NMR) spectroscopy

[0067] The crosslinking agent molecules were dissolved in deuterated dimethyl sulfoxide-d6 (DMSO-d6) to prepare the sample for testing. The sample was then subjected to liquid-state NMR analysis using a nuclear magnetic resonance spectrometer (Brand: Bruker; Model: AVANCE 600 MHz).

[0068] Tensile strength (MPa), elongation at break (%) and Young's modulus

[0069] The test was conducted using a tensile testing machine (brand: Shimadzu; model: AG-SI). The film was cut into 5 cm pieces. 0.45 cm. At least five samples were taken from each group of specimens for testing. The film was fixed 1 cm above and below the top and bottom of the universal tensile testing machine, and then stretched at a rate of 2 mm / min until it broke. In the stress-strain curve obtained from the tensile test, the maximum stress value is the tensile strength, the strain value at fracture is the elongation at break, and the initial slope of the curve is defined as Young's modulus. The evaluation results of tensile strength, elongation at break, and Young's modulus are shown in Table 1.

[0070] Ion exchange capacity (IEC)

[0071] The measurement method used was the Mohr titration method. First, the membrane was immersed in a 1 M sodium chloride (NaCl) aqueous solution for at least 24 hours to ensure that the anions carried by the cation groups within the membrane were all Cl- ions. Next, the membrane was washed with deionized water to remove excess ions remaining on the surface, and then dried in a vacuum oven to remove moisture. The dry weight (Wdry) was then measured. Subsequently, the membrane was immersed in a 1 M sodium sulfate (Na2SO4) aqueous solution for at least 24 hours to allow SO42- ions to displace Cl- ions, transferring the Cl- ions into the aqueous solution. Finally, titration was performed using a 0.1 N silver nitrate (AgNO3) aqueous solution, and the ion exchange capacity was calculated using the following formula 1. The evaluation results of the ion exchange capacity are shown in Table 1.

[0072] Formula 1

[0073] In Formula 1, C is the concentration of the AgNO3 aqueous solution (in M), V is the volume of the AgNO3 aqueous solution (in mL), and Wdry is the membrane weight of the anion exchange membrane (in g).

[0074] Water Uptake

[0075] Cut a film of appropriate size, immerse it in deionized water, and soak it at room temperature for at least 24 hours. Then weigh the wet weight (Wwet). Subsequently, place the film in a vacuum oven to dry it and remove moisture, then weigh the dry weight (Wdry). Calculate the absorbency (WU) using the following formula 2. The evaluation results of absorbency are shown in Table 1.

[0076] Formula 2

[0077] Dimensional stability

[0078] The dried film was cut into 3 cm lengths, which is the dried length Ldry. Then, the film was placed in deionized water and soaked at room temperature for at least 24 hours, and its length Lwet after water absorption was measured. The swelling ratio (SR) was calculated using Formula 3 below; a smaller SR value indicates better dimensional stability. The evaluation results of dimensional stability are shown in Table 1.

[0079] Formula 3

[0080] Hydroxide ion conductivity

[0081] In the experiments using an impedance analyzer (Autolab; model: PGSTAT 30), platinum wire was used as electrodes, and the four-point probe method was employed to measure conductivity. The film was cut into 3cm x 1cm strips, placed in a fixture, and immersed in a deionized water bath after vacuum degassing to ensure the film maintained a 100% humidity environment and was unaffected by carbon dioxide. Measurements were performed every 10°C at 30°C until the temperature reached 80°C. Current was applied to the two outer electrodes, and the two middle electrodes were used for measurement. The scanning frequency range was from 0.1 Hz to 10 kHz, and data fitting was performed using FRA. The intercept of the real axis was obtained from the Nyquist plot, and the ohmic impedance value was calculated. Finally, the hydroxide ion conductivity was calculated using the following formula (Formula 4). The evaluation results of the hydroxide ion conductivity are shown in Table 1.

[0082] Formula 4

[0083] In Formula 4, l is the distance between the reference electrodes (in cm), A is the cross-sectional area of ​​the membrane sample (in cm2), and R is the resistance (in Ω).

[0084] Alkaline stability

[0085] Cut the film into 3 cm pieces. A 1 cm film was taken and immersed in a 1 M KOH aqueous solution at 60 °C for 192 hours. During this process, the film was taken out every 48 hours for conductivity measurement to assess the change in conductivity and thus analyze the alkali stability of the film. The evaluation results of alkali stability are shown in Table 1.

[0086] Table 1

[0087] Please refer to Figures 1 and 2, which are NMR spectra 100 and 200 of the cross-linked molecules used in Examples 2 and 4, respectively. As can be seen from Figures 1 and 2, the signals of the hydrogens attached to the imidazole group (structurally labeled d and e) appear at chemical shifts between 6.5 ppm and 7.5 ppm, while the signals of the hydrogens of the methyl group on the imidazole (structurally labeled f) appear at chemical shifts between 2.2 ppm and 2.5 ppm. Since the main difference between the cross-linked molecules of Examples 2 and 4 lies in the structure of the long carbon chain in the middle, the chemical shifts of the hydrogens on the long carbon chain (structurally labeled a, b, and c) will differ significantly. In particular, when the adjacent hydrogen atoms are different (structurally labeled a and b), the chemical shifts of hydrogens labeled a and b in Figure 1 are between 1 ppm and 2 ppm, while the chemical shifts of hydrogens labeled a and b in Figure 2 are between 3 ppm and 4 ppm.

[0088] Furthermore, as shown in Table 1 above, although the hydroxide ion conductivity of the cross-linked anion exchange membranes in Examples 1 to 6 was not significantly better than that in Comparative Examples 1 to 3, Examples 1 to 6 exhibited better alkali stability and dimensional stability. Because the cross-linked molecules used in Examples 1 to 6 have a methyl or ethyl structure at the C2 position of the imidazole group, this helps to reduce the degradation of the imidazole group, thus resulting in better alkali stability. Because the cross-linked molecules used in Examples 1 to 6 can effectively fix the structure of the film, they also exhibit better dimensional stability.

[0089] Furthermore, compared to Comparative Examples 1 to 3, Examples 1 to 6 exhibit higher ion exchange capacities by combining organic polymers with cross-linked molecules. Examples 1 to 6 also demonstrate superior water absorption due to the promotion of water channel formation by cross-linked molecules possessing bisimidazole onium groups. Moreover, the cross-linked molecules of Examples 3 to 6 further enhance water absorption by also possessing hydrophilic ether groups.

[0090] According to the above embodiments, the present invention provides a cross-linked anion exchange membrane, which utilizes cross-linked molecules with a specific bisimidazole onion structure to cross-link with organic polymers, thereby exhibiting high alkali stability, dimensional stability and ion conductivity, and thus improving its applicability.

[0091] Although the present invention has been disclosed above with reference to several embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which this invention pertains may make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this invention shall be determined by the appended claims.

[0092] 100, 200: NMR spectra

[0093] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A cross-linked anion exchange membrane, comprising: a cross-linked molecule, wherein the cross-linked molecule comprises the structure shown in formula (I): (I) In formula (I), X represents bromine, chlorine or iodine atom respectively; Y represents alkyl groups having 1 to 8 carbon atoms or divalent organic groups having 4 to 8 carbon atoms and having an ether group respectively; Z represents alkyl groups having 4 to 8 carbon atoms or divalent organic groups having an ether group respectively; R represents methyl or ethyl respectively; and n is any integer between 1 and 4; and an organic polymer, wherein the organic polymer is crosslinked with the crosslinked molecule, and the organic polymer comprises polybenzimidazole, polybenzoxazole, polybenzothiazole, polyetherketone, polyether sulfide, polyphenylene sulfide, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyphenylene chloride, branched polybenzimidazole, branched polybenzoxazole, branched polybenzothiazole, branched polyetherketone, branched polyether sulfide, branched polyphenylene sulfide or any combination thereof.

2. The cross-linked anion exchange membrane as claimed in claim 1, wherein the cross-linked molecules comprise at least one of the following: (The rest of the text appears to be a list of molecules and their components, which is not translated as it's not part of the main text.) 、 ...

3. The cross-linked anion exchange membrane as claimed in claim 1, wherein the polybenzimidazole has the structure shown in formula (II) as follows: (II) In formula (II), A represents a divalent organic group, and o represents any integer between 90 and 500.

4. The cross-linked anion exchange membrane as claimed in claim 1, wherein the branched polybenzimidazole has the structure shown in formula (III) as follows: (III) In formula (III), A represents a divalent organic group, B represents -(CH2)2- or -CH2-O-CH2-, C represents a tertiary amine group, r represents any integer between 0 and 2, p represents any integer between 1 and 50, and q represents an integer of (100-p).

5. The cross-linked anion exchange membrane as claimed in claim 1, wherein the polystyrene comprises the structure shown in formula (IV): (IV) In formula (IV), s represents any integer between 5 and 9, and t represents an integer of (10-s).

6. The cross-linked anion exchange membrane as described in claim 1, wherein the alkaline stability of the cross-linked anion exchange membrane is not less than 80%.

7. The cross-linked anion exchange membrane as claimed in claim 1, wherein the thickness of the cross-linked anion exchange membrane is from 20 micrometers to 100 micrometers.

8. The cross-linked anion exchange membrane as claimed in claim 1, wherein the ion exchange capacity of the cross-linked anion exchange membrane is from 1.5 mmole / g to 2.2 mmol / g.

9. The cross-linked anion exchange membrane as claimed in claim 1, wherein the cross-linked anion exchange membrane has a hydroxide ion conductivity of not less than 0.030 S / cm at 30°C and a hydroxide ion conductivity of not less than 0.072 S / cm at 80°C.

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