- A comparative study of side-chain-type poly(ether ether ketone) anion exchange membrane functionalized with different hetero-cycloaliphatic quaternary ammonium groups
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Anion exchange membranes based on side-chain-type quarternized poly(ether ether ketone)s (QPEEKs), containing different hetero-cycloaliphatic quaternary ammonium groups, were prepared via a multi-step procedure, including polycondensation with a monomer containing pendant methylphenyl groups, bromomethylation, and followed by quaternization with 1-methylpyrrolidine (MPY), 1-methylpiperidine (MPRD), 1-methylimidazole (MIDZ) and N-methyl morpholine (MMPH), respectively. The properties of these membranes were then compared with the properties of conventional quarternized poly(ether ether ketone)s containing benzyltrimethylammonium (QPEEK-TMA). Model compounds, QMPY, QMPRD, QMIDZ and QMMPH, were synthesized and used to quantitatively compare the alkaline stability of hetero-cycloaliphatic quaternary ammonium groups using 1H NMR. The results of this study indicated that the alkaline stability of all these model compounds is in the order of QMPY > QMPRD > QTMA > QMIDZ > QMMPH. These QPEEKs membranes display superior thermal, dimensional and mechanical stability. QPEEK-TMA, QPEEK-MPY and QPEEK-MPRD exhibit higher hydroxide conductivities and lower activation energies than QPEEK-MIDZ and QPEEK-MMPH. Furthermore, after exposure to 1 M NaOH at 60 °C for 24 days, QPEEK-MPY and QPEEK-MPRD demonstrated a loss in hydroxide conductivity of 28.5% and 33.4%, respectively. Both values were lower than that of QPEEK-TMA (37.7%). Therefore, among these side-chain-type QPEEKs membranes, QPEEK-MPY and QPEEK-MPRD, containing benzylmethylpyrrolidinium and benzylmethylpiperidinium as cation head-groups, are promising AEM materials for fuel cell construction.
- Yao, Dan,Wei, Tonghui,Shang, Lichao,Na, Hui,Zhao, Chengji
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p. 7975 - 7983
(2019/03/19)
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- Synthesis of aryl alkyl ethers by alkylation of phenols with quaternary ammonium salts
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Phenolic compounds can be efficiently O-methylated with tetramethylammonium chloride in diglyme or polyethyleneglycol (PEG) at temperatures of 150-160 °C and in the presence of either K2CO3 or NaOH. When applying benzyl-trimethylammonium chloride as a reagent, the benzylation and methylation of phenols occurs, with the benzylation product always predominating. With allyl-substituted phenols as substrates and using NaOH as a base it was possible to achieve both the alkylation and the double-bond isomerization of the allyl group to obtain (E/Z)-propenyl-substituted methyl and benzyl aryl ethers in a single preparative step.
- Maras, Nenad,Polanc, Slovenko,Kocevar, Marijan
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experimental part
p. 29 - 36
(2010/09/05)
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