This paper reports the performance of direct methanol fuel cells ͑DMFCs͒ using novel disulfonated poly͑arylene ether benzoni-trile͒ copolymers derived from hexafluoro-isopropylidene diphenol ͑6F͒, 2,6-dichlorobenzonitrile, and 3,3Ј-disulfonated 4,4Ј-dichloro diphenyl sulfone ͑SDCDPS͒. The membrane electrode assembly ͑MEA͒ which employed the sulfonated copolymer with 35 mol % of disulfonated comonomer as the proton exchange membrane had approximately 2-fold lower methanol crossover and slightly higher ͑about 10%͒ cell resistance than the MEA using the perfluorosulfonic acid Nafion membrane, resulting in an approximately 50% improvement in selectivity, regardless of membrane thickness. Accordingly, this MEA outperformed the Nafion MEA control in a DMFC single-cell test. For example, 200 mA/cm 2 was obtained ͑compared with 150 mA/cm 2 for the Nafion MEA͒ at 0.5 V at a temperature of 80°C and ambient air pressure. Similar experiments performed with nonfluorinecontaining biphenol-based sulfonated poly͑arylene ether sulfone͒ copolymers ͑BPSH͒ indicated that the compatibility of the polymer electrolyte with the electrodes likely has a critical role in initial DMFC performance.

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We study the eA'ects of Ni doping on the infrared reflectance of YBa2(Cu, "Ni )307 q Alms with up to 4% substitution of Cu by Ni. Normal-state spectra indicate that the primary eA'ect of Ni on the conduction carriers is to increase their elastic scattering rate. At 4 at. % Ni, the elastic-scattering rate is calculated to be large enough to generate a large absorption onset at the gap edge in the superconducting state, if a gap exists. The superconducting-state spectra show no evidence for such a feature. Comparisons with phenomenological models for the optical conductivity show that the conductivity, and hence the superconducting density of states, is very gapless.