title: Microheterogeneity in native and cation-exchanged Nafion membranes.
abstract: 2-(4'-Pyridyl)benzimidazole (4PBI) has been used to investigate the microheterogeneity of water nanochannels of Nafion membranes at two different hydration levels. Native as well as cation-exchanged Nafion membranes are found to protonate one of the two monoprotonated forms of 4PBI selectively. In native membranes and in those in which H(3)O(+) ions are replaced by (CH(3))(4)N(+) ions, the pyridyl nitrogen is protonated preferentially. In Na(+)-exchanged membranes, however, the benzimidazole nitrogen is protonated selectively. Unlike other fluorescent probes used in earlier studies, 4PBI can differentiate between the two different cation-exchanged membranes at lower as well as higher hydration levels.
authors: Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, India 400076.
authors: E Siva Subramaniam
authors: ES
authors: Iyer
authors: Anindya
authors: A
authors: Datta