NAMS 2002 Workshop - ICOM 2008

investigated at first. As a result, it was suggested that these polymers are stable
at both of oxidative and reductive conditions. Then, we synthesized sulfonated
PDAs by soaking a membrane of PDA with trimethylsilyl groups in sulfuric
acid/ethyl acetate solution. The physical properties such as gas permeability
coefficients, ion-exchange capacity and tensile strength were investigated with
these membranes. As a result, membranes of the sulfonated PDAs exhibited
lower gas permeability compared with those of non-sulfonated PDAs, and
oxygen gas permeability coefficient of the sulfonated PDA membranes were
around 1.0 x 10 -8 barrer. This gas permeability coefficient was as same as that of
Nafion 115. This result indicated that the introduction of the sulfonic acid groups
reduced the gas permeability. The sulfonated membranes showed good proton
conductivity, 1.0 x 10 -2 S/cm at 363 K, 90 % RH. Then, single cell performance
was measured at 353 K, 90 %RH, and almost same performance was obtained
compared with that of Nafion 115. The degradation ratio of the cell voltage was
also estimated by holding at OCV condition for several hundred hours as the
accelerating durability test. The average degradation ratio was about -150 uV/h.
From these results, this novel proton exchange membrane comprising the PDAs
will be candidate for the membrane to actualize high temperature operating of
PEMFCs.