Poly(phenylene oxide) functionalized with quaternary ammonium groups via flexible alkyl spacers for high-performance anion exchange membranes

Dang, Hai-Son; Weiber, Annika; Jannasch, Patric

doi:10.1039/c5ta00350d

Cited by 265 publications

(258 citation statements)

References 30 publications

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“…11,39 Our results are contrary to those reported. At this point, we do not have conclusive answers as to why this contradiction exists.…”

Section: 3contrasting

confidence: 57%

“…In this work, we decided to evaluate the alkaline stability of AEMs with IECs in the range 1.5-2.0 mmol/g, since these are typical values for AEMs employed in AEM fuel cells and solid-state alkaline water electrolyzers, 2,3,14,15 and because we suspect that in some of the previous works, the AEMs evaluated had lower IECs, which led to an incorrect assessment of the alkaline stability. 39 It is more difficult to accurately estimate changes in the IEC and ionic conductivity when the functionalization degree is low, because of the quantification limits of the analytical techniques. The second step in the synthesis involved the reduction of the ketone group in the pendant chain.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis and Alkaline Stability of Solubilized Anion Exchange Membrane Binders Based on Poly(phenylene oxide) Functionalized with Quaternary Ammonium Groups via a Hexyl Spacer

Parrondo

Jung

Wang

et al. 2015

J. Electrochem. Soc.

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Anion exchange membranes (AEMs) with hexyl pendant chains were synthesized by Friedel-Crafts acylation of 6-bromo-1-hexanoyl chloride on poly(phenylene oxide) (PPO), followed by the reduction of the ketone with triethylamine, and quaternization with a tertiary amine (trimethylamine, quinuclidine, or 1-methylimidazole). 1 H-NMR, 13 C-NMR, COSY and HMQC NMR spectroscopies were used to prove the formation of the brominated polymers and to assess the alkaline stability of the AEMs. The alkaline stability of trimethylamine (TMA) based AEMs was evaluated using two separate, complementary experiments. In the first experiment, the AEMs were dissolved in 1 M NaOD+DMSO-d6 and kept at 60 • C. 1 H NMR spectra revealed signs of AEM degradation (same qualitative result for all the cationic groups) after 2 days in alkaline solution. The ion exchange capacity of TMA-C6-PPO, as calculated by integration of the corresponding NMR peaks, decreased 39% after 30 days (from 1.8 ± 0.1 to 1.1 ± 0.1 mmol/g). In the second experiment, TMA-C6-PPO AEM was immersed in nitrogen degassed 1 M KOH at 60 • C for 30 days. The ion exchange capacity of this AEM decreased 33% confirming previous results. The finding that PPO-based AEMs with hexyl spacers degrade in alkali suggests the hypothesis that alkyl spacers can be used to increase the alkaline stability is not valid for all backbones and conditions. © The Author There is an increasing interest in alkaline stable anion exchange membranes (AEMs), and solubilized AEM binders for applications in alkaline membrane fuel cells (AMFCs) and solid-state alkaline water electrolyzers.1-3 Operating in alkaline conditions presents distinct and attractive advantages to AMFCs and solid-state alkaline water electrolyzers, in comparison to acidic proton-exchange membrane fuel cells and water electrolyzers. Under alkaline conditions, it is possible to achieve faster oxygen reduction kinetics, more efficient water management, there is greater flexibility in the choice of fuels, and more importantly, presents the possibility of using nonprecious-metal electrocatalysts.1,4 On the other hand, the hydrogen oxidation/evolution reaction is more sluggish in alkaline media. 5-10The majority of the AEMs evaluated and reported in the peer-reviewed literature comprise polymers functionalized with benzyl trimethylammonium groups or, similar cation groups attached to the benzyl carbon of polymer backbones like polyphenylene, 11,12 polyphenylene oxide, 13,14 polysulfone, 15-20 and polyetheretherketone. [21][22][23] The reasons for this structure are the preference for polyaromatic backbones (due to its better chemical stability when compared with aliphatic backbones) and the favored functionalization routes using bromination or chloromethylation. Several recent reports have shown that the benzyl substituted quaternary ammonium cation degrades significantly faster than other cations with alkyl groups under mild alkaline conditions. 24,25 Most of the quaternary ammonium salts evaluated experimentally by Marino and Kreuer 24 and ...

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“…11,39 Our results are contrary to those reported. At this point, we do not have conclusive answers as to why this contradiction exists.…”

Section: 3contrasting

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Synthesis and Alkaline Stability of Solubilized Anion Exchange Membrane Binders Based on Poly(phenylene oxide) Functionalized with Quaternary Ammonium Groups via a Hexyl Spacer

Parrondo

Jung

Wang

et al. 2015

J. Electrochem. Soc.

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“…Previously in our lab [18], one side chain type AEM with a flexible aliphatic spacer between ion conducting group and polymer main chain have been prepared and proved to possess enhanced hydroxide conductivity. Recently, a series of side chain type AEMs have been reported [19][20][21], all demonstrating that the flexibility of side chain, which decides the mobility of ion conducting group, also has profound influence on the nano-phase separation ability and the anion conductivity of AEM.…”

Section: Introductionmentioning

confidence: 99%

Dual-cation comb-shaped anion exchange membranes: Structure, morphology and properties

et al. 2016

Journal of Membrane Science

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“…Jannasch et al functionalized poly (phenylene oxide) with quaternary ammonium groups via flexible alkyl spacers (PPO-7Q). Significantly enhanced hydroxide ion conductivity and far superior alkaline stability in relation to corresponding polymers with quaternary ammonium (QA) groups placed in benzylic positions directly on the backbone(quaternized poly(phenylene oxide), denoted as QPPO) were observed 15 . It provided a straight forward synthetic strategy to separate the cation groups from polymer backbone.…”

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confidence: 99%

A strategy to construct alkali-stable anion exchange membranes bearing ammonium groups via flexible spacers

et al. 2015

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Poly(phenylene oxide) functionalized with quaternary ammonium groups via flexible alkyl spacers for high-performance anion exchange membranes

Abstract: COMMUNICATIONThis journal is

Cited by 265 publications

References 30 publications

Synthesis and Alkaline Stability of Solubilized Anion Exchange Membrane Binders Based on Poly(phenylene oxide) Functionalized with Quaternary Ammonium Groups via a Hexyl Spacer

Synthesis and Alkaline Stability of Solubilized Anion Exchange Membrane Binders Based on Poly(phenylene oxide) Functionalized with Quaternary Ammonium Groups via a Hexyl Spacer

Dual-cation comb-shaped anion exchange membranes: Structure, morphology and properties

A strategy to construct alkali-stable anion exchange membranes bearing ammonium groups via flexible spacers

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