No abstract

Three sulfonated aromatic polymers with different sequence lengths were studied in order to better understand the relationship between molecular structure, morphology, and properties of proton exchange membranes as a function of relative humidity. A random copolymer with a statistical distribution of sulfonic acid groups had very small domain sizes, whereas an alternating polymer with sulfonic acid groups spaced evenly along the polymer chain was found to have larger, but quite isolated, domains. The multiblock copolymer studied herein showed highly phase-separated hydrophilic and hydrophobic domains, with good long-range connectivity. Scanning force microscopy as a function of relative humidity was used to observe water absorption and swelling of the hydrophilic domains in each of the three membranes. The conductivity, water sorption kinetics, and fuel cell performance, especially at low relative humidity, were found to be highly dependent upon the morphology. The multiblock copolymer outperformed both the random and alternating systems at 100°C and 40% RH fuel cell operating conditions and showed similar performance to Nafion.

A 15-b 1-Msamplels digitally self-calibrated pipeline analog-to-digital converter (ADC) is presented. A radix 1.93, 1 b per stage design is employed. The digital self-calibration accounts for capacitor mismatch, comparator offset, charge injection, finite op-amp gain, and capacitor nonlinearity contributing to DNL. A THD of -90 dB was measured with a 9.8756-kHz sine-wave input. The DNL was measured to be within 2~0.25 LSB at 15 b, and the INL was measured to be within f1.25 LSB at 15 b. The die area is 9.3 mm x 8.3 mm and operates on f4-V power supply with 1.8-W power dissipation. The ADC is fabricated in an 11-V, 4-GHz, 2.4-pm BiCMOS process.