Conductivity and Water Content in Asymmetrical Sulfonated Block Copolymers

ORAL

Abstract

We have determined the morphology, proton conductivity and water uptake of asymmetric sulfonated poly(styrene-$b$-methylbutylene) (PSS-PMB) membranes equilibrated with 98{\%} relative humidity (RH) air. To our surprise we found that the conductivity of low molecular weight PSS-PMB samples decreased slowly and irreversibly when the temperature of the membrane (and air) was increased. In contrast, high molecular weight PSS-PMB samples with the same asymmetry decreased more rapidly in response to a temperature change. In addition the factor by which the conductivity decreased was significantly higher in the case of the low molecular weight PSS-PMB. This puzzle was resolved by in-situ small angle neutron scattering which enabled determination of the morphological response of the samples to changes in temperature at RH=98{\%}. The morphology-conductivity relationship in the equilibrated state gives insight into factors that govern charge transport in these systems.

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Authors

  • Xin Wang

    • Environmental Energy Technologies Division, Materials Sciences Division, LBNL and Dept of Chemical Engineering, University of California, Berkeley

  • Nitash P. Balsara

    • Environmental Energy Technologies Division, Materials Sciences Division, LBNL and Dept of Chemical Engineering, University of California, Berkeley

  • Keith M. Beers

    • Environmental Energy Technologies Division, Materials Sciences Division, LBNL and Dept of Chemical Engineering, University of California, Berkeley

  • Moon J. Park

    • Environmental Energy Technologies Division, Materials Sciences Division, LBNL and Dept of Chemical Engineering, University of California, Berkeley