Crosslinked polyfluorenyl anion exchange membrane and preparation method thereof

Abstract

The invention discloses a cross-linked polyfluorenyl anion exchange membrane and a preparation method thereof. The membrane comprises a polymer shown in a formula I, the membranes exhibit good equilibrium properties, including high ionic conductivity, low swelling rate, good tensile strength, good fuel cell performance, and excellent chemical stability. These properties are achieved by incorporating in their structure an optimal amount of cross-linking agent containing potential cationic groups. The disclosed anion exchange membranes are useful in alkaline fuel cells, water electrolysis devices, and other electrochemical applications.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a cross-linked polyfluorene anion exchange membrane and its preparation method. Background Technology

[0002] Anion exchange membrane fuel cells (AEMFCs) offer significant advantages over proton exchange membrane fuel cells due to their lower redox potential and faster electrode reaction kinetics. This allows them to operate using non-platinum group metal (n-PGM) catalysts such as silver, cobalt, and nickel. This characteristic makes AEMFCs more economically viable than PEMFCs, as PGM catalysts account for nearly 40% of the total cost of a fuel cell.

[0003] Unfortunately, most AEMs exhibit unbalanced properties, typically due to the use of numerous cationic groups in their structure to enhance ionic conductivity. However, this also leads to high swelling ratios (SR) and weak mechanical properties. Furthermore, achieving sufficient chemical stability is a challenge, as the cationic groups and the polymer backbone of AEMs degrade in high-temperature alkaline or oxidizing environments.

[0004] To address the stability issues related to basicity and oxidation, highly stable cationic groups, such as piperidine and ammonium cationic groups, and highly stable polymer backbones are required. Ether-free polyfluorenes have attracted considerable interest due to their excellent chemical stability and mechanical properties. These ether-free backbones exhibit minimal degradation through common degradation pathways such as Hoffmann deprotonation, nucleophilic substitution, and E1 elimination. Furthermore, effective methods for protecting cationic groups include steric hindrance through adjacent components and the use of long, flexible spacers for the cationic groups.

[0005] Achieving a balanced performance in AEMs requires developing practical strategies to enhance ionic conductivity without compromising dimensional stability and mechanical properties. These strategies should also provide acceptable thermal and chemical stability, ion exchange capacity (IEC), and molecular weight. Crosslinking is an effective method for achieving this. However, striking the appropriate trade-offs between different AEM properties using this strategy has proven challenging. For example, crosslinking can significantly reduce IEC and ionic conductivity due to the high molecular weight of the crosslinking agent. Excessive crosslinking can also render the AEM insoluble in common solvents. Therefore, determining suitable crosslinking agents and the appropriate degree of crosslinking in AEMs is crucial. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a cross-linked polyfluorene anion exchange membrane and a method for preparing the same.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a polymer of formula I:

[0008] Each of them The components are independently selected from biphenyl, p-terphenyl, p-tetraphenyl, m-terphenyl, diphenylmethane, bibenzyl, 1,3,5-triphenylbenzene, 9,9-dimethylfluorene, cis-1,2-diphenylethylene, trans-1,2-stilbene, or acenaphthene; for ; Each Independently selected , ; Q. Each L1 and L2 is independently selected from C2~C20 straight-chain alkyl groups; x = 0.4~0.8.

[0009] In this invention, the polymer of formula I consists of a polyfluorene-based polymer backbone and piperidine and ammonium cationic groups. A crosslinking agent containing potential cationic groups (i.e., introducing crosslinking group Q) is incorporated into the polymer structure. By adjusting the degree of crosslinking (CLD), a sharp decrease in IEC and ionic conductivity is prevented. By determining the optimal CLD in the polymer backbone of formula I, an AEM with highly balanced performance is achieved, exhibiting good ionic conductivity, IEC, swelling ratio, water absorption, mechanical properties, and chemical stability. These AEMs have potential applications in alkaline fuel cells, water electrolysis devices, and other electrochemical applications.

[0010] In some embodiments, the molar percentage of the sum of crosslinked L1 and uncrosslinked L1 and L2 in the polymer of Formula I is 0%-80% and not 0%; such as 0.01%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0011] In some implementations, x = 0.4 to 0.8, such as 0.4, 0.5, 0.6, 0.7, 0.8, etc.

[0012] In some embodiments, Q, each L1, and L2 are each independently selected from C3-C15 straight-chain alkyl groups, such as ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, etc.

[0013] In some implementations, each Independently selected , , , , , , , , , .

[0014] In some embodiments, the polymer of formula I is selected from the following polymers: (2) .

[0015] A second aspect of the present invention provides a method for preparing the polymer of formula I, comprising the following steps: S1: Monomer ,monomer With monomer A polymerization reaction was carried out to obtain the polymer of formula (1); (1)

[0016] S2: The polymer of formula (1) is crosslinked with N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine, and then quaternized with 1-methylpiperidine. After counterion exchange, the polymer of formula I is obtained. Among them, monomer for ; , , The definitions of L1, L2, and x are as described above; X is a halogen.

[0017] In some embodiments, n is the molar percentage of the alkyl side chain in the fluorenyl block crosslinked with N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine relative to the uncrosslinked alkyl side chain that reacts only with 1-methylpiperidine; n = 0%-80% and not 0%; such as 0.01%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0018] In some implementations, X is selected from F, Cl, Br, I, etc.

[0019] In some embodiments, the monomer Selected from , , .

[0020] In some embodiments, in S1, the reaction solvent for the polymerization reaction includes at least one of dichloromethane, chloroform, and tetrahydrofuran.

[0021] In some embodiments, in S1, the polymerization reaction is carried out in the presence of a catalyst; the catalyst includes trifluoroacetic acid and / or trifluoromethanesulfonic acid; the monomer The molar ratio with the catalyst is 1:(15-25), such as 1:(18-22), 1:20, etc.

[0022] In some embodiments, in S1, the reaction temperature of the polymerization reaction is 10-35°C; the reaction time is 30-80 min, such as 40-70 min.

[0023] In some embodiments, in S2, the molar ratio of the polymer of formula (1), N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine, and 1-methylpiperidine is 1:(0.01~1.0):(1.0~10), such as 1:(0.05~0.8):(1.0~8), 1:(0.05~0.6):(1.0~7), 1:(0.06~0.5):(1.0~6.0), etc. In this invention, the degree of crosslinking of the polymer of formula I can be adjusted by adjusting the molar ratio of N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine to 1-methylpiperidine.

[0024] In some embodiments, the N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine includes at least one of N,N,N',N'-tetramethylethylenediamine (TEMED), N,N,N',N'-tetramethylpropylenediamine (TMPDA), N,N,N',N'-tetramethyl-1,6-hexanediamine (TMHDA), N,N,N',N'-tetramethylheptanediamine, N,N,N',N'-tetramethyldodecanediamine, and N,N,N',N'-tetramethyleicosanediamine.

[0025] In some embodiments, in S2, the reaction temperature of the crosslinking reaction is 40-80°C, such as 50-70°C; and the reaction time is 2-4 hours.

[0026] In some embodiments, in S2, the reaction temperature of the quaternization reaction is 40-80°C, such as 50-70°C; and the reaction time is 8-20h, such as 10-15h.

[0027] In some embodiments, the counterion exchange is carried out by soaking in a strong alkaline solution; the concentration of the strong alkaline solution is 0.5~2.0 mol / L; and the soaking time is 12~48 h, such as 20~30 h.

[0028] A third aspect of the present invention provides a polymer film comprising the polymer of formula I.

[0029] In some embodiments, the average thickness of the polymer film is 5-50 μm, such as 10-30 μm.

[0030] In some embodiments, the polymer film contains 400-3500 mg / cm³ of polymer of formula I. 3 .

[0031] In a fourth aspect, the present invention provides a method for preparing the polymer film, comprising the following steps: coating a solution containing a polymer of formula I onto a substrate, curing and then peeling it off to obtain the polymer film.

[0032] In some embodiments, the curing temperature is 60-90℃, such as 70-80℃; and the curing time is 8-20h, such as 10-15h.

[0033] A fifth aspect of the present invention provides an anion exchange membrane comprising the polymer of Formula I or the polymer film thereof.

[0034] A sixth aspect of the present invention provides an anion exchange membrane having a fluorenyl block and a phenyl block polymer backbone and N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA) as a crosslinking agent, as represented by formulas (1) and (2): (1)

[0035] Aryl 1, Aryl 2, and Linker are respectively: Aryl 1: 9,9-bis(5-bromopentyl)fluorene, 9,9-bis(6-bromohexyl)fluorene or 9,9-Bis(7-bromoheptyl)fluorene; Aryl 2: p-triphenyl, m-Triphenyl, Diphenyl, 9,9-Dimethylfluorene or Bisbenzyla; Linker: 2,2,2-Trifluoroacetophenone or 1,1,1-Trifluoroacetone; x represents the molar ratio of the corresponding repeating unit, which can be between 0.4 and 0.8. (2)

[0037] n represents the molar ratio of the corresponding repeating units, which can be between 0.4 and 0.8; the degree of crosslinking can also be between 0% and 80%.

[0038] A seventh aspect of the present invention provides a method for preparing the aforementioned anion exchange membrane, comprising the following steps: (a) Reaction of the fluorenyl repeating unit and phenyl repeating unit and suitable linker as described in claim 1 in the presence of trifluoromethanesulfonic acid and dichloromethane; (b) Crosslinking was performed using TMHDA as a crosslinking agent, followed by quaternization using 1-methylpiperidine as a cationic group on the side chain of N-methyl-2-pyrrolidone; (c) Cast polymer to form a thin film.

[0039] An eighth aspect of the present invention provides an electrochemical device comprising the polymer of Formula I, the polymer film, or the anion exchange membrane.

[0040] In some embodiments, the electrochemical device includes an alkaline dye battery, an anion exchange membrane water electrolyzer, a metal-air battery, and a carbon dioxide reduction and energy storage system.

[0041] The beneficial effects of this invention are: The polymer films of this invention exhibit a good balance of properties, including high ionic conductivity, low swelling ratio, good tensile strength, good fuel cell performance, and excellent chemical stability. These properties are achieved by incorporating an optimal amount of crosslinking agent containing potential cationic groups into their structure. The disclosed anion exchange membrane can be used in alkaline fuel cells, water electrolysis devices, and other electrochemical applications. Attached Figure Description

[0042] Figure 1 Representative examples of anion-exchange polymers prior to crosslinking and quaternization disclosed in this invention are described.

[0043] Figure 2 A schematic diagram of the synthetic crosslinked and quaternized polyfluorene polymer used to form the anion exchange membrane of the present invention is shown.

[0044] Figure 3A and Figure 3B This shows the polyfluorene-based polymer before crosslinking and quaternization ( Figure 3A ) and quaternization (PFT60-x0) Figure 3B )of 1 H NMR spectrum.

[0045] Figure 4 Br was shown - FTIR results of PFT60-x0 – x80 AEM.

[0046] Figure 5 The tensile strength of PFT50-x0 – x80 and PFT60-x0 – x80 AEMs as a function of the degree of crosslinking is described.

[0047] Figure 6 The water absorption rate of PFT50-x0 – x80 and PFT60-x0 – x80 AEMs as a function of crosslinking degree is shown.

[0048] Figure 7 The swelling ratios of PFT50-x0 – x80 and PFT60-x0 – x80 AEMs are shown as a function of the degree of crosslinking.

[0049] Figure 8 The contact angle values ​​for PFT60-x0 – x80 AEM are displayed.

[0050] Figure 9 The AFM results and hydrophilic phase width quantification results of PFT60-x0 – x80 AEM are shown (small figure).

[0051] Figure 10A and Figure 10B It showed ( Figure 10A The hydroxide conductivity of PFT50-x0 – x80 and PFT60-x0 – x80 AEMs as a function of crosslinking degree; and ( Figure 10B The hydroxide conductivity of PFT60-x0 – x80 AEM as a function of temperature.

[0052] Figure 11 The ex-situ chemical stability test of PFT60-x0 AEM after immersion in 3M NaOH solution at 80°C for 1080 hours is shown. 1 1H NMR spectroscopy, and oxidative stability test after soaking in Fenton's reagent at 80°C for 120 hours.

[0053] Figure 12 The cell voltage and power density as a function of current density of a fuel cell operating at 80°C with H2O2 and a back pressure of 1 bar using an AEM prepared according to the present invention are demonstrated.

[0054] Figure 13 The AEM prepared according to the present invention is shown to be thawed at 0.5 A·cm at 70°C. -2 The in-situ durability results were measured after 72 h under a back pressure of 0.2 bar.

[0055] Figure 14 OH was displayed - FTIR results of PFT60-x40 AEM before and after in-situ durability testing. Detailed Implementation

[0056] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0057] In this article, "room temperature" refers to 25°C.

[0058] The terminology used herein is intended to describe particular implementations and should not be construed as limiting the invention. The term "and / or" as used herein covers any and all combinations of the listed items. The singular forms "a," "an," and "the" include both singular and plural forms unless the context clearly indicates otherwise. Furthermore, when used in this specification, the terms "comprising" and / or "including" indicate the presence of the stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of other features, steps, operations, elements, and / or groups thereof.

[0059] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the meanings commonly understood by one of ordinary skill in the art. Terms as defined in common dictionaries shall be interpreted in accordance with their meanings in the relevant field and in the context of this disclosure, and shall not be interpreted in an idealized or overly formal manner unless expressly defined herein.

[0060] In describing this invention, it should be understood that various techniques and steps are disclosed herein. Each of these techniques has its own advantages and can be used in combination with one or more other disclosed techniques. To avoid unnecessary repetition, this specification does not explicitly state every possible combination of the steps. However, it should be understood that such combinations fall within the scope of this invention and the claims. The specification and claims should be interpreted as including such combinations.

[0061] This article discusses a cross-linked fluorene-based anion exchange membrane. Numerous specific details are included in the following description to provide a full understanding of the invention. However, those skilled in the art will recognize that the invention can be practiced without these specific details.

[0062] This disclosure is an illustrative example of the invention and is not intended to limit the invention to the specific embodiments shown in the drawings or described below.

[0063] The invention will now be described with reference to the accompanying drawings, which illustrate exemplary embodiments. The invention provides anion exchange polymers in which fluorene blocks having alkyl side chains and phenyl blocks form the polymer backbone. Figure 1 Representative examples of anion exchange polymers before crosslinking and quaternization are shown. Fluorenyl blocks with alkyl side chains incorporating a potential cationic group (Aryl 1) can be selected from repeating units of 9,9-bis(5-bromopentyl)fluorene, 9,9-bis(6-bromohexyl)fluorene, and 9,9-bis(7-bromoheptyl)fluorene. Phenyl blocks (Aryl 2) can be selected from repeating units of p-triphenyl, m-triphenyl, diphenyl, dibenzyl, and 9,9-diphenylfluorene. The connectors between these repeating units can be selected from 2,2,2-trifluoroacetophenone or 1,1,1-trifluoroacetone. The preferred value of x represents... Figure 1 The molar ratio of the fluorene-based block is between 0.4 and 0.8. A molar ratio (x) less than 0.4 may reduce ionic conductivity and IEC. An x value greater than 0.8 may significantly increase the swelling ratio. Therefore, it is more preferable to limit the x ratio to 0.5-0.7, with the most preferred value being 0.6.

[0064] The polymer backbone described in this invention contains no ether groups in its structure, which enhances its chemical stability against alkaline and oxidizing environments at high temperatures. This ensures good long-term stability in electrochemical applications such as alkaline fuel cells and water electrolysis devices.

[0065] Figure 2 A synthetic process using a preferred embodiment of the method is shown, employing p-triphenyl as the phenyl block, 9,9-bis(6-bromohexyl)fluorene as the fluorenyl block, and 2,2,2-trifluoroacetophenone as the linker. The molar ratio of the fluorenyl blocks, denoted by "n", is preferably 0.5 or 0.6. The presence of piperidinyl and ammonium cationic groups in the AEM structure ensures good chemical stability of the cationic groups at high temperatures. To further improve the chemical stability of the cationic groups, the present invention provides steric hindrance through adjacent repeating units and flexible alkyl side chains. Furthermore, the present invention reduces the inductive effect between the cationic groups and the polyfluorene backbone by introducing long-chain alkyl side chains onto the polyfluorene blocks.

[0066] Introducing crosslinking into AEMs is a practical method to improve properties such as mechanical strength, water absorption, and swelling ratio. However, it often leads to a decrease in ionic conductivity, IEC, and even makes the prepared polymer insoluble in commonly used solvents for film casting. By utilizing TMHDA with potential cationic groups, ionic conductivity can be improved while maintaining dimensional stability and mechanical properties. To take advantage of the TMHDA crosslinking agent, the polymer backbone with appropriate repeating units and the optimal molar percentage of each repeating unit must be rationally designed. This invention provides a preferred embodiment for achieving this objective. By utilizing appropriate polymer backbone, cationic groups, and crosslinking agents, a balance can be achieved between the desired properties of AEMs, resulting in high ionic conductivity, high IEC, low water absorption and swelling ratio, excellent thermal and chemical stability, and high molecular weight.

[0067] This invention achieves a good balance of properties in AEM by adjusting the molar ratio of fluorene and phenyl blocks in the AEM structure and controlling the degree of crosslinking of TMDHA. The degree of crosslinking is defined as the molar percentage of the bromine-containing alkyl side chain in the fluorene block crosslinked with TMDHA relative to the uncrosslinked alkyl side chain that reacts only with 1-methylpiperidine.

[0068] In a preferred embodiment, AEM is composed of 0.6 molar ratio of 9,9-bis(6-bromohexyl)fluorene (BBF) and 0.4 molar ratio of p-terphenyl as repeating units, with a crosslinking degree ranging from 20% to 60%, more preferably 40%.

[0069] The superior performance of the AEM of the present invention includes a balanced combination of high ionic conductivity, moderate IEC, low water absorption and swelling rate, acceptable mechanical properties, good fuel cell performance, and excellent chemical stability. In some embodiments, the AEM of the present invention exhibits 144 mS·cm -1 hydroxide conductivity, 2 mmol·g -1 The IEC rating, 78% WU, 15% SR, tensile strength of 27 MPa, and 1.03 W·cm -2 The peak power density (PPD) of the fuel cell is achieved. These balanced characteristics are achieved by introducing an optimal amount of crosslinking agent (TMHDA) with potential cationic groups into its structure.

[0070] Another significant advantage of the AEM in this invention is its excellent alkaline and oxidative stability. The chemical stability of some embodiments surpasses that of state-of-the-art AEMs, representing one of the best chemical stability results reported to date. Some embodiments of this invention, after immersion in 3M NaOH solution at 80°C for 1080 hours, retained 93% of their hydroxide conductivity, 95% of their IEC, and 96% of their tensile strength, and showed only a 4.7 wt.% weight loss after immersion in Fenton solution at 80°C for 120 hours, demonstrating excellent chemical stability.

[0071] Therefore, the AEM proposed in this invention can be used in a wide range of applications, including alkaline fuel cells, water electrolysis devices, CO2 reduction, flow batteries and other electrochemical devices.

[0072] The present invention is further illustrated by the following non-limiting embodiments, which are provided for illustrative purposes.

[0073] Example 1 PFT60-x0 AEM A poly(terphenyl co-BBF) AEM was prepared with a BBF molar ratio of 0.6 and a crosslinking degree of 0%. A mixture of BBF (1.86 g, 3.78 mmol), p-terphenyl (TP, 0.58 g, 2.52 mmol), 2,2,2-trifluoroacetophenone (970 μL, 6.93 mmol), and dichloromethane (5.8 mL) was added to a 100 mL flask, and the temperature was lowered to 0 °C. Trifluoroacetic acid (TFA, 800 μL) and trifluoromethanesulfonic acid (TFSA, 5.8 mL) were then added dropwise to the solution, and the mixture was stirred at this temperature for 10 minutes. The reaction was then maintained at room temperature for 50 minutes. The high-viscosity solution was then diluted with 15 mL of dichloromethane and poured into 150 mL of ethanol. The resulting solid was washed three times with ethanol and deionized water, and then thoroughly dried under vacuum at 65 °C to give a white solid (PFT-0.6) in 95% yield. 1 The H NMR results are as follows Figure 3A (As shown).

[0074] To synthesize the crosslinked and quaternized polymer, PFT-0.6 was reacted with TMHDA and 1-methylpiperidine. PFT-0.6 (0.8 g, 1.47 mmol) was dissolved in NMP (20 mL) at 60°C. Subsequently, 1-methylpiperidine (1070 μL, 8.82 mmol) was added, and the mixture was stirred at 60°C for 12 hours. A schematic diagram of the membrane synthesis process is shown below. 1 The H NMR results are as follows: Figure 2 and Figure 3A As shown.

[0075] The resulting solution obtained in the previous step was filtered and then poured (11 mL) into a 20 × 10 cm⁻¹ container. 2 A film was prepared on a glass plate. Subsequently, the casting solution was heated at 75°C for 12 hours in a vacuum oven. The resulting Br... - The Br film was carefully peeled off from the glass plate and then immersed in 1 M NaOH solution at room temperature for 24 hours to achieve Br - and OH - The membrane underwent counterion exchange. It was then washed with deionized water and stored in deionized water for further use. The membrane thickness was approximately 20 ± 5 μm.

[0076] Example 2 PFT60-x20 AEM A poly(terphenyl co-BBF) AEM was prepared with a BBF molar ratio of 0.6 and a CLD of 20%. PFT60-x20 was prepared according to the same process described in Example 1, with the following changes in the crosslinking and quaternization steps. Before adding 1-methylpiperidine, TMHDA (37.7 μL, 0.18 mmol) was added to the solution, and the mixture was stirred at 60°C for 3 hours. Subsequently, 1-methylpiperidine (858 μL, 7.06 mmol) was added, and the mixture was further stirred at the same temperature for 12 hours. Furthermore, to adjust the concentration of the final solution before the film casting step, excess 4 mL of NMP was added to the solution, and film casting was performed using 13 mL of the solution in the same manner as in Example 1.

[0077] Example 3 PFT60-x40 AEM A poly(terphenyl co-BBF) AEM was prepared with a BBF molar ratio of 0.6 and a CLD of 40%. PFT60-x40 was synthesized using the same process described in Example 2, but with the following modifications: the amounts of TMHDA and 1-methylpiperidine were adjusted to (75.4 μL, 0.35 mmol) and (643 μL, 5.29 mmol), respectively. Furthermore, an excess of 6 mL of NMP was added to the solution to achieve the desired concentration of the final solution before membrane casting. The membrane casting process was performed using 14 mL of the solution in the same manner as in Example 1.

[0078] Example 4 PFT60-x60 AEM A poly(terphenyl co-BBF) AEM was prepared with a BBF ratio of 0.6 molar and a CLD of 60%. PFT60-x60 was synthesized using the same process described in Example 2, but with the following modifications: the amounts of TMHDA and 1-methylpiperidine were adjusted to (113.1 μL, 0.53 mmol) and (429 μL, 3.53 mmol), respectively. Furthermore, an excess of 8.5 mL of NMP was added to the solution to achieve the desired concentration of the final solution before membrane casting. The membrane casting process was performed using 15 mL of the solution in the same manner as in Example 1.

[0079] Example 5 PFT60-x80 AEM A poly(terphenyl co-BBF) AEM was prepared with a BBF molar ratio of 0.6 and a CLD of 80%. PFT60-x80 was synthesized according to the same process described in Example 2, but with the following modifications: the amounts of TMDHA and 1-methylpiperidine were adjusted to (150.8 μL, 0.71 mmol) and (214 μL, 1.76 mmol), respectively. Furthermore, to achieve the desired concentration of the final solution before membrane casting, an excess of 11 mL of NMP was added to the solution. The membrane casting process was performed using 16 mL of the solution in the same manner as in Example 1. FTIR results are as follows: Figure 4 As shown.

[0080] Comparative Example 1: PFT50-x0 AEM Prepare poly(terphenyl co-BBF) AEM with a BBF ratio of 0.5 molar ratio and a CLD of 0%. PFT50-x0 was synthesized according to the same process described in Example 1, but with the following modifications: In the first step, 1.55 g (3.15 mmol) of BBF and 0.72 g (3.15 mmol) of TP were used. In addition, in the crosslinking and quaternization steps, the amount of 1-methylpiperidine was changed to 893 μL (7.35 mmol).

[0081] Comparative Example 2: PFT50-x20 AEM Prepare poly(terphenyl co-BBF) AEM with a BBF ratio of 0.5 molar ratio and a CLD of 20%. PFT50-x20 was synthesized using the same process described in Example 2, but with the following modifications: In the first step, 1.55 g (3.15 mmol) of BBF and 0.72 g (3.15 mmol) of TP were used. Furthermore, in the crosslinking and quaternization steps, the amounts of TMDHA and 1-methylpiperidine were changed to 31.4 μL (0.15 mmol) and 715 μL (5.88 mmol), respectively.

[0082] Comparative Example 3: PFT50-x40 AEM A poly(terphenyl co-BBF) AEM was prepared with a BBF ratio of 0.5 molar and a CLD of 40%. PFT50-x40 was synthesized using the same process described in Example 3, but with the following modifications: In the first step, 1.55 g (3.15 mmol) of BBF and 0.72 g (3.15 mmol) of TP were used. Furthermore, in the crosslinking and quaternization steps, the amounts of TMDHA and 1-methylpiperidine were changed to 62.9 μL (0.29 mmol) and 536 μL (4.41 mmol), respectively.

[0083] Comparative Example 4: PFT50-x60 AEM Prepare poly(terphenyl co-BBF) AEM with a BBF ratio of 0.5 molar ratio and a CLD of 60%. PFT50-x60 was synthesized using the same process described in Example 2, but with the following modifications: In the first step, 1.55 g (3.15 mmol) of BBF and 0.72 g (3.15 mmol) of TP were used. Furthermore, in the crosslinking and quaternization steps, the amounts of TMHDA and 1-methylpiperidine were changed to 94.3 μL (0.44 mmol) and 357 μL (2.94 mmol), respectively.

[0084] Comparative Example 5: PFT50-x80 AEM Prepare poly(terphenyl co-BBF) AEM with a BBF ratio of 0.5 molar ratio and a CLD of 80%. PFT50-x80 was synthesized using the same process described in Example 2, but with the following modifications: In the first step, 1.55 g (3.15 mmol) of BBF and 0.72 g (3.15 mmol) of TP were used. Furthermore, in the crosslinking and quaternization steps, the amounts of TMDHA and 1-methylpiperidine were changed to 125.7 μL (0.59 mmol) and 179 μL (1.47 mmol), respectively.

[0085] Test case The instrumental analysis and experimental methods are described below: Acquired using a Bruker Advance 400 spectrometer 1 1H NMR nuclear magnetic resonance spectroscopy. PFT-n copolymer (before crosslinking and quaternization) was dissolved in CDCl3, while AEM was dissolved in DMSO-d6 containing 5 v% TFA, which altered the water peak and thus revealed piperidine and quaternary ammonium peaks.

[0086] The IEC of AEM was determined using the Mohr titration method. Initially, Br... - The AEM of type M was dried in a vacuum oven, and the resulting weight was recorded as M. drySubsequently, AEM was soaked in 0.5 M NaNO3 solution at 60 °C for 48 h to release Br. - Ions. The resulting solution was then titrated with 0.01 M AgNO3 solution, using K2CrO4 as an indicator. OH - The IEC of type AEM can be calculated according to formulas (1) and (2): (1) (2) VAgNO3 is the silver nitrite solution consumed during the titration process, with 0.0629g coming from Br. - Ions and OH - The weight difference of ions.

[0087] Methods for determining WU and SR: OH - Type AEMs were immersed in deionized water at a specified temperature for 3 hours, and then the wet weight (W) of the membrane was recorded after removing excess surface moisture. wet ) and length (L) wet WU and SR can be calculated using formulas (3) and (4) respectively: (3) (4) in and OH in dry state - Weight and length of type AEM.

[0088] The hydroxide conductivity of an AEM with a thickness of 20 ± 5 μm was determined using a dual-electrode electrochemical workstation (Gamry Instruments Reference 3000). Measurements were performed using a membrane conductivity fixture equipped with a platinum electrode. The fixture was immersed in degassed deionized water at a specified temperature, and impedance measurements were performed using an AC current amplitude of 100 μA within a frequency range of 10 Hz to 1 MHz. The Nyquist plot was fitted using ZView 4 software, and the hydroxide conductivity (σ) was calculated using formula (5): (5) Where W, T, and R represent the width, thickness, and impedance of the film, respectively, and L represents the distance between the electrodes.

[0089] Br was tested using a Biolin Theta contact angle tester. - Hydrophobicity of the dry AEM. The contact angle of each membrane sample was measured three times, and the average value is used as the representative value.

[0090] Researching Br using Bruker Dimension Icon AFM in tap mode - Microphase separation was performed using a dry AEM. To improve the visualization of microphase separation, adjustments were made to the data scale, contrast, offset, and noise level using the "Bruker NanoScope Analysis" software.

[0091] Br was measured at room temperature using a rheometer (ARES 3, TA Instruments). - Mechanical properties of type AEM. The wet film was cut into dumbbell-shaped samples with an effective area of ​​3.5 × 11 mm, and measured at 1 mm·min⁻¹. -1 Stretch rate.

[0092] The alkaline stability of AEMs was investigated by immersing the membranes in 3 M NaOH solution at 80°C for 1080 h and monitoring changes in chemical structure, IEC, tensile strength, and hydroxide conductivity.

[0093] Battery performance was measured using a single-cell fuel cell (Fuel Cell Technologies Inc., USA). A 5 cm² substrate was prepared using a catalyst-coated substrate (CCS) method. 2 Membrane electrode assembly (MEA). Anode and cathode slurries were sprayed onto both sides of a gas diffusion layer (GDL, Toray 060) using a spray gun. The slurries were prepared using a solution of Pt-Ru / C (40 wt% Pt, 20 wt% Ru, TKK corp.) for the anode, Pt / C (47 wt% Pt, TKK corp.) for the cathode, and PiperION-A5 ionomer (5 wt.%, I / C = 0.6, Versogen, USA) in deionized water and isopropanol (1:12.5). The noble metal loadings of the anode and cathode were approximately 0.2 mg·cm³. -2 The catalyst slurry was ultrasonically treated at 0 °C for 1 h, and then sprayed. Then, MEA was soaked in 1 M NaOH for 24 h to promote ion exchange to OH-. - The MEA was then assembled with a torque of 5.1 N·m, using a 150 μm thick PTFE sheet as the battery pad. The battery was evaluated in a fuel cell system at 80 °C, 1 bar back pressure, and 80% and 100% relative humidity at the anode and cathode, respectively. The battery was first activated at a constant voltage of 0.5 V until a stable current was reached, and then the polarization curves were recorded.

[0094] The in-situ durability of the fuel cell was measured at a constant current density of 70°C, 0.2 bar back pressure, and 95% and 100% relative humidity at the anode and cathode, respectively. The MEA preparation for the durability test was the same as that for the polarization curve recording.

[0095] Experimental Example 1. AEM Attribute Analysis The gel fractions shown in Table 1 confirm successful crosslinking of AEM. Higher degrees of crosslinking result in higher gel fraction values, attributed to the polymer chain interconnections promoted by TMDHA as a crosslinking agent. This evaluation was conducted using NMP as a solvent at 80 °C for 24 h. Furthermore, the crosslinking process enhanced tensile strength, such as… Figure 5 As shown. It is worth noting that, Figures 6-8 This indicates that an increase in CLD leads to a significant decrease in WU and SR. This result can be attributed to the limiting effect of crosslinking on water absorption and swelling, as well as the presence of hydrophobic alkyl chains in the crosslinking agent structure.

[0096] Table 1

[0097] Figure 9 The AFM results shown provide insight into AEMs with different CLDs (Examples 1 to 5). In the AFM images, dark areas correspond to the hydrophilic phase containing cationic groups, while bright areas represent the hydrophobic phase containing both the main chain and alkyl chains. It was observed that increasing the CLD leads to an increase in the width of the hydrophilic phase when the CLD is below 40%. However, the width of the hydrophilic phase decreases when the CLD reaches 60% and 80%. Meanwhile, connected ion-conducting channels were observed in all PFT60-x0, PFT60-x20, and PFT60-x40 samples. The weaker and thinner ion-conducting channels are only apparent at higher CLDs, which can be attributed to the limited mobility of the cationic groups containing alkyl chains in these AEM structures. Figure 10A and 10B The effects of CLD and temperature on hydroxide conductivity were explained. Results showed that increasing the CLD not only improved WU, SR, and tensile strength, but also increased hydroxide conductivity, provided the CLD remained below 40%. This enhancement can be attributed to improved microphase separation in the AEM. However, when the CLD exceeded 40-50%, hydroxide conductivity decreased sharply. This reduction can be attributed to a significant decrease in water absorption and limited mobility of cationic groups containing alkyl chains. Therefore, a CLD of 40-50% is considered optimal for achieving a balanced set of properties. Thus, the preferred AEM was designated PFT60-x40 (Example 3). Table 2 provides a summary of the properties for all examples.

[0098] Table 2

[0099] Table 3 presents the residual tensile strength, IEC, and hydroxide conductivity of PFT60-x0 (Example 1) and PFT60-x60 (Example 4) AEMs after immersion in 3M NaOH solution at 80°C for 1080 hours. The results show that all the above properties exhibit a retention rate of over 93%, with both crosslinked (PFT60-x60) and uncrosslinked (PFT60-x0) AEMs exhibiting excellent alkali stability. This exceptional behavior can be attributed to the utilization of the ether-free polyaromatic backbone and the stable cationic groups shielded by long and flexible alkyl chains. The chemical stability shows superior performance compared to state-of-the-art AEMs, representing one of the most significant chemical stability results reported to date. Furthermore, the oxidative stability of the AEMs was assessed by immersion in Fenton solution (2 wt.% aqueous H2O2, 4 ppm FeSO4) at 80°C for 120 hours. The weight loss of PFT60-x0 was only 8.2%, while that of the PFT60-x60 AEM was 4.7%. These results demonstrate the excellent stability of AEM in high-temperature oxidizing environments. Following the above stability tests, the stability of AEM... 1 HNMR results further confirmed this finding. Typically, the cationic groups used in this invention can undergo Hoffmann elimination at the β-hydrogen or nucleophilic substitution at the α-carbon. However, in the examination... 1 Following the H NMR results, no new peaks indicating this degradation were observed in the range of 3.5–6.5 ppm.

[0100] Table 3

[0101] Experimental Example 2: Fuel Cell Performance Analysis by AEM In the preparation of MEAs, both the PFT60-x40 (Example 3) and PFT50-x40 (Comparative Example 3) AEMs were prepared with a thickness of approximately 20 μm. See also Figure 12 The resulting membrane exhibited a significant open-circuit voltage exceeding 1.05 V, indicating excellent gas barrier properties and a defect-free state. At a current density of 2.5 A·cm⁻¹... -2 At a back pressure of 1 bar, a peak power density of 1.03 W·cm⁻¹ was achieved using the PFT60-x40 membrane. -2 It should be noted that fuel cell performance is affected not only by AEM performance but also by other factors, including MEA fabrication, catalyst loading, ionomer carbon ratio (I / C ratio), and various other relevant parameters. Therefore, further optimization of fuel cell testing parameters could potentially improve fuel cell performance based on the already good performance demonstrated by the PFT60-x40 AEM. Figure 13The PFT60-x40 (Example 3) AEM was also shown at 70°C and 0.5 A·cm. -2 In-situ durability after 200 hours at current density. As shown in the figure, the voltage decay rate is approximately 0.62 mV·h. -1 .also, Figure 14 This indicates that no chemical degradation occurred in the AEM structure during the in-situ stability test, and the voltage decay may be related to other parameters such as catalyst aggregation, carbonation, and weak water management.

[0102] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A polymer of formula I: ； in, Each The components are independently selected from biphenyl, p-terphenyl, p-tetraphenyl, m-terphenyl, diphenylmethane, bibenzyl, 1,3,5-triphenylbenzene, 9,9-dimethylfluorene, cis-1,2-diphenylethylene, trans-1,2-stilbene, or acenaphthene; for ; Each Independently selected , ; Q. Each L1 and L2 is independently selected from C2~C20 straight-chain alkyl groups; x=0.4~0.8。 2. The polymer of formula I according to claim 1, characterized in that: In the polymer of Formula I, the molar percentage of the sum of L1 crosslinked by the crosslinking group Q and the uncrosslinked L1 and L2 is 0%-80% and not 0%.

3. The polymer of formula I according to claim 1, characterized in that: Q. Each L1 and L2 is independently selected from C3~C15 straight-chain alkyl groups.

4. The polymer of formula I according to claim 1, characterized in that: The polymer of Formula I is selected from the following polymers: （2） 。 5. A method for preparing the polymer of formula I according to any one of claims 1-4, characterized in that: Includes the following steps: S1: Monomer ,monomer With monomer A polymerization reaction was carried out to obtain the polymer of formula (1); （1） S2: The polymer of formula (1) is crosslinked with N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine, and then quaternized with 1-methylpiperidine. After counterion exchange, the polymer of formula I is obtained. Among them, monomer for ; , , The definitions of L1, L2, and x are as defined in any one of claims 1-4; X is a halogen.

6. The method for preparing the polymer of formula I according to claim 5, characterized in that: n is the molar percentage of the alkyl side chain in the fluorenyl block crosslinked with N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine relative to the uncrosslinked alkyl side chain that reacts only with 1-methylpiperidine; n = 0%-80% and is not 0%.

7. The method for preparing the polymer of formula I according to claim 5, characterized in that: The monomer Selected from , , .

8. The method for preparing the polymer of formula I according to claim 5, characterized in that: In S2, the molar ratio of the polymer of formula (1), N,N,N',N'-tetramethyl-C2~C20 straight-chain alkyl diamine and 1-methylpiperidine is 1:(0.01~1.0):(1.0~10).

9. A polymer film, characterized in that: Includes the polymer of formula I as described in any one of claims 1-4.

10. The polymer film according to claim 9, characterized in that: The average thickness of the polymer film is 5-50 µm; and / or, the content of the polymer of formula I in the polymer film is 400-3500 mg / cm³. 3 .

11. An anion exchange membrane, characterized in that: Includes the polymer of formula I as described in any one of claims 1-4 or the polymer film as described in claim 9 or 10.

12. An anion exchange membrane, characterized in that: Using fluorenyl and phenyl blocks as the polymer backbone and N,N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA) as the crosslinking agent, it is represented by formulas (1) and (2): （1） Aryl 1, Aryl 2, and Linker are respectively: Aryl 1: , or ; Aryl 2: , , , or ; Linker: 2,2,2-Trifluoroacetophenone or 1,1,1-Trifluoroacetone; x represents the molar ratio of the corresponding repeating unit, which can be between 0.4 and 0.

8. (2) n represents the molar ratio of the corresponding repeating units, which can be between 0.4 and 0.8; the degree of crosslinking can also be between 0% and 80%.

13. A method for preparing the anion exchange membrane according to claim 12, characterized in that: Includes the following steps: (a) Reaction of the fluorenyl repeating unit and phenyl repeating unit and suitable linker as described in claim 1 in the presence of trifluoromethanesulfonic acid and dichloromethane; (b) Crosslinking was performed using TMHDA as a crosslinking agent, followed by quaternization using 1-methylpiperidine as a cationic group on the side chain of N-methyl-2-pyrrolidone; (c) Cast polymer to form a thin film.

14. An electrochemical device, characterized in that: Includes the polymer of formula I as described in any one of claims 1-4, the polymer film as described in claim 9 or 10, or the anion exchange membrane as described in claim 11 or 12.

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