Counterion motions and thermal ordering effects in perfluorosulfonate ionomers probed by solid-state NMR

✍ Scribed by Jong Keun Park; Justin Spano; Robert B. Moore; Sungsool Wi

• Book ID: 104088072
• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 594 KB
• Volume: 50
• Category: Article
• ISSN: 0032-3861
• DOI: 10.1016/j.polymer.2009.10.016

✦ Synopsis

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a b s t r a c t Perfluorosulfonate ionomers (PFSIs) neutralized by tetraalkylammonium ions have been investigated using variable temperature 1 H and 13 C solid-state NMR (ssNMR) spectroscopy to probe the thermally induced properties of tetraalkylammonium ions at temperatures near the a-relaxations. Tetramethylammonium

ions have been incorporated in our study for the systematic control of ionic interactions within PFSIs according to the chain-length of ammonium ions. 13 C static ssNMR results show that bulkier TPA þ and TBA þ ions undergo molecular tumbling motions near or above the a-relaxation temperature of the corresponding PFSI ionomers, with jumping rates of k z 1 kHz. Moreover, the results of 1 H spin-lattice (T 1 ) relaxation time measurements suggest that smaller TMA þ ions in the PFSI exhibit a thermally induced ordering effect as the sample temperature approaches the a-relaxation temperature of TMA þ -PFSI. This ordering phenomenon is also supported by the results from small-angle X-ray scattering.