J. Halim et al., CHARACTERIZATION OF PERFLUOROSULFONIC ACID MEMBRANES BY CONDUCTIVITY MEASUREMENTS AND SMALL-ANGLE X-RAY-SCATTERING, Electrochimica acta, 39(8-9), 1994, pp. 1303-1307
Three perfluorosulfonic acid membranes, Nafion 120, Nafion 117 and Dow
, pretreated in water at 100-degrees-C were characterized by conductiv
ity measurements in the temperature range of 20-90-degrees-C and by Sm
all-Angle X-Ray Scattering (SAXS) at room temperature. The results dem
onstrate that conductivity is determined by the apparent proton equiva
lent conductivity and not the proton volume concentration. The apparen
t equivalent conductivities increase in the sequence Nafion 120 < Nafi
on 117 < Dow. SAXS reveals the same average cluster size of 5.3 nm for
all three membranes but different cluster densities increasing in the
sequence: Nafion 120 < Nafion 117 < Dow. Therefore, the proton equiva
lent conductivity is determined by the cluster density with the polyme
r network.