Branched comb-shaped poly(arylene ether sulfone)s containing flexible alkyl imidazolium side chains as anion exchange membranes

Liu, Dong; Xu, Muzi; Fang, Mingliang; Chen, Jiale; Wang, Lei

doi:10.1039/c8ta02115e

Cited by 89 publications

(61 citation statements)

References 58 publications

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“…However, AAEM conductivity is significantly influenced by hydrophobic-hydrophilic microphase separation, because a well-defined polymer morphology (e.g., bicontinuous hydrophobic-hydrophilic channels) facilitates water/hydroxide transportation in solid-state membranes (14). In previous reports, modifying polymer morphology with multiblock sequences (15)(16)(17)(18), long flexible side chains (18)(19)(20)(21), or microporous structures (22) has improved hydroxide conductivity. For instance, Watanabe and coworkers (15) observed that multiblock poly(arylene ether)s showed significantly higher hydroxide conductivity than their random copolymer analogs [σ (OH − , 60°C) = 126 mS/cm and 35 mS/cm for multiblock and random copolymers, respectively.…”

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confidence: 99%

Highly conductive and chemically stable alkaline anion exchange membranes via ROMP of trans -cyclooctene derivatives

You

Padgett

MacMillan

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

130

107

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Alkaline anion exchange membranes (AAEMs) are an important component of alkaline exchange membrane fuel cells (AEMFCs), which facilitate the efficient conversion of fuels to electricity using nonplatinum electrode catalysts. However, low hydroxide conductivity and poor long-term alkaline stability of AAEMs are the major limitations for the widespread application of AEMFCs. In this paper, we report the synthesis of highly conductive and chemically stable AAEMs from the living polymerization of trans-cyclooctenes. A trans-cyclooctene-fused imidazolium monomer was designed and synthesized on gram scale. Using these highly ring-strained monomers, we produced a range of block and random copolymers. Surprisingly, AAEMs made from the random copolymer exhibited much higher conductivities than their block copolymer analogs. Investigation by transmission electron microscopy showed that the block copolymers had a disordered microphase segregation which likely impeded ion conduction. A cross-linked random copolymer demonstrated a high level of hydroxide conductivity (134 mS/cm at 80°C). More importantly, the membranes exhibited excellent chemical stability due to the incorporation of highly alkaline-stable multisubstituted imidazolium cations. No chemical degradation was detected by 1 H NMR spectroscopy when the polymers were treated with 2 M KOH in CD 3 OH at 80°C for 30 d.alkaline anion exchange membrane | trans-cyclooctene | block and random copolymer | cross-linked polymer | transmission electron microscopy A lkaline anion exchange membranes (AAEMs) are a class of polymer electrolytes constructed from immobilized cations with hydroxide counteranions (1-3). AAEMs have been widely used for a variety of electrochemical applications, such as redox flow batteries, electrodialysis, and water electrolysis (4-7). One of the most important applications for AAEMs is their use as polyelectrolytes in alkaline exchange membrane fuel cells (AEMFCs). These devices can efficiently convert chemical energy in fuels (e.g., H 2 , hydrazine, and direct alcohols) into electricity. In comparison with proton exchange membrane fuel cells and aqueous alkaline fuel cells, AEMFCs are advantageous because they allow for rapid reduction of oxygen at the cathode, limit fuel cross-over, prevent the formation of carbonate precipitates, and are compatible with nonnoble electrocatalysts (8-12). Because of their essential role in AEMFCs, AAEMs have been extensively studied to optimize their performance and, in particular, to improve their hydroxide conductivity and alkaline stability.Hydroxide conductivity is one of the most important parameters used to evaluate AAEMs, because it is directly related to the ohmic resistance and power density of an AEMFC (9). There are several strategies to enhance the hydroxide conductivity of AAEMs. The most straightforward method is to increase the ion exchange capacity (IEC), such that more ions are present in AAEMs. However, a higher IEC typically results in higher water uptake. While the presence of water facilitates h...

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confidence: 99%

Highly conductive and chemically stable alkaline anion exchange membranes via ROMP of trans -cyclooctene derivatives

You

Padgett

MacMillan

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

130

107

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“…[14][15][16] Recently, our group reported a set of highly branched sulfonated poly(arylene ether) membranes, [16][17][18] and one of the branched membranes, poly(fluorenyl ether ketone sulfone)s (BSPFEKS), displayed the proton conductivity of 0.42 S cm −1 and oxidative stability of 327 minutes. 16 Branched structure imparts high free volume in the polymer matrix, 19 thus decreasing its methanol barrier ability and mechanical strength. Herein, we synthesized the highly branched partially fluorinated sulfonated poly(ether ketone sulfone) by changing the bisphenol monomer.…”

Section: Discussionmentioning

confidence: 99%

Highly branched poly(arylene ether)/surface functionalized fullerene‐based composite membrane electrolyte for DMFC applications

et al. 2019

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Summary Sulfonated branched polymer membranes have been gaining immense attention as the separator in energy‐related applications especially in fuel cells and flow batteries. Utilization of this branched polymer membranes in direct methanol fuel cell (DMFC) is limited because of large free volume and high methanol permeation. In the present work, sulfonated fullerene is used to improve the methanol barrier property of the highly branched sulfonated poly(ether ether ketone sulfone)s membrane without sacrificing its high proton conductivity. The existence of sulfonated fullerene with larger size and the usage of small quantity in the branched polymer matrix effectively prevent the methanol transportation channel across the membrane. The composite membrane with an optimized loading of sulfonated fullerene displays the highest proton conductivity of 0.332 S cm−1 at 80°C. Radical scavenging property of the fullerene improves the oxidative stability of the composite membrane. Composite membrane exhibits the peak power density of 74.38 mW cm−2 at 60°C, which is 30% larger than the commercial Nafion 212 membrane (51.78 mW cm−2) at the same condition. From these results, it clearly depicts that sulfonated fullerene‐incorporated branched polymer electrolyte membrane emerges as a promising candidate for DMFC applications.

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“…Xu group reported AEMs based on the hyperbranched polymer structures containing QA groups, which processed high ionic conductivity and prolonged stability under alkaline conditions . In addition, polymer backbones containing branched side chains with multiple cation groups are also considered as an effective approach to boosting ion conducting for it constructs inter‐connected ion conducting channels . Our group has developed branched comb‐shaped copolymers as AEMs, which exhibited high ionic conductivity and robust alkaline stability .…”

Section: Introductionmentioning

confidence: 99%

“…[31][32][33] Our group has developed branched comb-shaped copolymers as AEMs, which exhibited high ionic conductivity and robust alkaline stability. 32 However, introducing branched structures may result in a larger distance between molecular chains, thus deteriorated the mechanical strength of the membranes.…”

Section: Introductionmentioning

confidence: 99%

“…[33][34][35][36] Most cross-linkers used in AEMs contained one or more quaternary ammoniums to connect the polymer chains to increase the concentration of OH − , thus improving the ionic conductivity; however, ammoniums are easy to be attacked by OH − , resulting in decreased mechanical properties and alkaline stability. We have focused on developing proton/anion exchange membranes several years, 32,[37][38][39][40][41][42][43][44][45][46][47][48][49] herein, to improve the ionic conductivity of alkali-doped PBIs without scarifying mechanical robust and alkali stability. This paper introduced a novel kind of hyperbranched cross-linkers to PBI membranes ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Alkali‐doped hyperbranched cross‐linked polybenzimidazoles containing benzyltrimethyl ammoniums with improved ionic conductivity as alkaline direct methanol fuel cell membranes

Gao

Fang

et al. 2020

Int J Energy Res

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Summary Development of anion exchange membranes (AEMs) with good performance, such as high conductivity, good alkaline stability and mechanical strength, has been a hot topic for the fuel cell application. Here, a novel kind of hyperbranched cross‐linker decorated with quaternary ammonium groups was introduced to polybenzimidazole (PBI) membranes and QOPBI‐x membranes (where x is the weight ratio of the hyperbranched cross‐linker). Compared with the linear OPBI membrane (0.091 S cm−1), QOPBI‐x membranes displayed an improved ionic conductivity (up to 0.122 S cm−1) at 60°C after they were doped in 6 M KOH for 7 days. The KOH‐doped QOPBI‐x membranes also exhibited a high tensile strength (54.5‐61.7 MPa) and superior alkaline stability. There is almost no decline in the ionic conductivity after being immersed in a 6 M KOH solution for 30 days. In addition, the alkaline direct methanol fuel cell (ADMFC) performance based on the KOH‐doped OPBI and QOPBI‐x membranes is described. The QOPBI‐15 membrane displayed good performance (75.6 mW cm−2), which is 33.3% higher than the OPBI membrane (56.7 mW cm−2).

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Branched comb-shaped poly(arylene ether sulfone)s containing flexible alkyl imidazolium side chains as anion exchange membranes

Abstract: A novel strategy can enhance conductivity and stability of AEMs via the introduction of a branched structure in polymers.

Cited by 89 publications

References 58 publications

Highly conductive and chemically stable alkaline anion exchange membranes via ROMP of trans -cyclooctene derivatives

Highly conductive and chemically stable alkaline anion exchange membranes via ROMP of trans -cyclooctene derivatives

Highly branched poly(arylene ether)/surface functionalized fullerene‐based composite membrane electrolyte for DMFC applications

Alkali‐doped hyperbranched cross‐linked polybenzimidazoles containing benzyltrimethyl ammoniums with improved ionic conductivity as alkaline direct methanol fuel cell membranes

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