DIELECTRIC-RELAXATION AND CONDUCTIVITY STUDY OF POLYTETRAFLUORENE-ETHYL IONOMERS

Dielectric relaxation measurement was performed on the H2O containing ionomer from Dow Chemical with polytetrafluoro-ethylene (PTFE) backbones. The temperature Cole-Cole plot of the complex permittivity was employed to separate the dielectric relaxation of the polar groups from the conducting ions at low temperatures. The resulting conductivities reached 10(-2) S/cm at 295 K, comparable to that of Nafion(R). The temperature dependence of the dc resistance was found to be non-Arrhenius and fitted by the Vogel Tamman-Fulcher expression T1/2 exp (Q(c)/(T - T(o))), yielding a T(o) of 90 K and Q(c) of 0.12 eV. The difference between this T(o) and the T(g) is much larger (over 250 K) than that of PEO (almost-equal-to 50 K). The polar-group relaxation extracted at temperatures between 90-160 K produced an activation energy of 0.075 eV. This relaxation is attributed to the restricted water molecules and pendant groups of PTFE affecting the ion transport.