Dielectric relaxation studies membranes

Z.D. Deng and K.A. Mauritz, Dielectric relaxation studies of acid-containing short-side-chain perfluorosulfonate ionomer membranes, Macromolecules, 1992, 25, 2369-2380. 

As in other ionomers, the ion exchange sites in "Nafion" membranes are observed to aggregate and form clusters. Ionic clustering in "Nafion" membranes has been indicated by a variety of physical studies including dielectric relaxation (1), small angle x-ray scattering (1-4), neutron scattering (4), electron micro-... 

M.G. McLin, M.C. WintersgiU, J.J. FontaneUa, R.S. Chen, J.P. Jayakody, S.G. Greenhaum, High pressure studies of hydrated NAFION membranes dielectric relaxation and deuteron NMR, Sohd State Ionics 60 (1993) 137—140. 

A low-temperature y relaxation at ca. -160°C at a. 300 Hz has an activation energy of 17 kJ/mol as determined dielectrically. It is mechanically very weak (E"max Vj x 10 N/m, tan 6 vLCT ), but it is dielectrically most intense (e" 10 2). it is due to the -SCLF group and is probably caused by either the rotation about tne C-S bond or by a localized wagging motion of the SO2F group itself. This Y relaxation is not detected in the frequency-temperature range of the torsion pendulum studies and is not found in the dielectric studies of the ionized Nafion membranes. 

The dielectric properties of polystyrenesulfonic acid membranes in their H form have also been studied over the frequency range of 10 -10 Hz, with H O content and temperature as parameters. It was concluded that the presence of water in the membrane gives rise to a specific, water induced relaxation process which is characterized by high dielectric constant, loss, and dielectric increment, Ae . 

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