Direct ESR detection and spin trapping of radicals generated by reaction of oxygen radicals with sulfonated poly(ether ether ketone) (SPEEK) membranes

作者：Pinteala Mariana^*; Schlick Shulamith

来源：Polymer Degradation and Stability, 2009, 94(10): 1779-1787.

DOI：10.1016/j.polymdegradstab.2009.06.009

• Sulfonated poly(ether ether ketone) (SPEEK)
• Electron spin resonance (ESR)
• 5,5-Dimethyl-1-pyrroline-1-oxide (DMPO)
• Spin trapping
• Free radicals

The stability of membranes under the strong oxidizing conditions in fuel cells is one of the major challenges in the development of fuel cells based on proton exchange membranes (PEMs). This study is centered on the determination of the susceptibility to degradation of SPEEK membranes exposed to (center dot)OH radicals, using both direct ESR and spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). In order to achieve a complete picture on SPEEK degradation, two types of experiments were performed: 1. UV irradiation at 77 K of SPEEK membranes swollen by aqueous solutions of H(2)O(2); 2. UV irradiation of SPEEK membranes swollen by aqueous solutions of H(2)O(2) in the presence of DMPO as a spin trap. UV irradiation without oxygen of SPEEK at 77 K in acid or basic form in the presence of H(2)O(2)/H(2)O produced phenoxyl radicals as the predominant radicals detected by direct ESR or spin trapping methods. At pH 4, the oxygen radicals produced phenyl radicals as the predominant species detected by spin trapping methods. The hydroperoxyl radical, as DMPO/OOH adduct, was detected only when the DMPO/OH adduct was absent. The appearance of phenyl and phenoxyl radicals provides the evidence that (center dot)OH radicals react with the aromatic ring of SPEEK or leading to the scission of its ether bridge.

• 出版日期2009-10