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.