TY - GEN
T1 - Alkaline stability and ion conductivity of polysulfone anion exchange membranes (AEMs) with different cation chemistries
AU - Arges, Christopher G.
AU - Ramani, Vijay
PY - 2013
Y1 - 2013
N2 - The use of several different NMR techniques (1H, 13C, 31P, 1H decoupled phosphorus, COSY, and 1H-X (X= 13C or 31P) HMQC) were employed to elucidate the chemical structure of degraded polysulfone (PSF) anion exchange membranes (AEMs) exposed to alkaline solutions. The NMR spectra revealed degradation products perpetrated by rearrangement reactions from ylide intermediates and direct nucleophilic attack for trimethylammonium (TMA+), 1,4-dimethylpiperazinium (DMP+), 1-methylimidazolium (1M+) and trimethylphosphonium (TMP+) cations. Stevens rearrangement was the only verified rearrangement reaction for the ammonium cations. Trimethylphosphonium PSF AEMs were observed to degrade through Somelet-Hauser rearrangement. The stability experiments demonstrated that the ylide mechanisms were more prevalent at lower concentrations of alkaline solutions (e.g. 1 M Na2CO3 and 1 M KOH) when compared to higher concentrations (e.g. 6 M KOH). Also, the NMR spectra provided evidence that the introduction of alkaline stable cation sites on PSF leads to ether hydrolysis of the backbone.
AB - The use of several different NMR techniques (1H, 13C, 31P, 1H decoupled phosphorus, COSY, and 1H-X (X= 13C or 31P) HMQC) were employed to elucidate the chemical structure of degraded polysulfone (PSF) anion exchange membranes (AEMs) exposed to alkaline solutions. The NMR spectra revealed degradation products perpetrated by rearrangement reactions from ylide intermediates and direct nucleophilic attack for trimethylammonium (TMA+), 1,4-dimethylpiperazinium (DMP+), 1-methylimidazolium (1M+) and trimethylphosphonium (TMP+) cations. Stevens rearrangement was the only verified rearrangement reaction for the ammonium cations. Trimethylphosphonium PSF AEMs were observed to degrade through Somelet-Hauser rearrangement. The stability experiments demonstrated that the ylide mechanisms were more prevalent at lower concentrations of alkaline solutions (e.g. 1 M Na2CO3 and 1 M KOH) when compared to higher concentrations (e.g. 6 M KOH). Also, the NMR spectra provided evidence that the introduction of alkaline stable cation sites on PSF leads to ether hydrolysis of the backbone.
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U2 - 10.1149/05002.2183ecst
DO - 10.1149/05002.2183ecst
M3 - Conference contribution
AN - SCOPUS:84885787410
SN - 9781607683506
T3 - ECS Transactions
SP - 2183
EP - 2197
BT - Polymer Electrolyte Fuel Cells 12, PEFC 2012
PB - Electrochemical Society Inc.
T2 - 12th Polymer Electrolyte Fuel Cell Symposium, PEFC 2012 - 222nd ECS Meeting
Y2 - 7 October 2012 through 12 October 2012
ER -