title: Water uptake profile in a model ion-exchange membrane: conditions for water-rich channels.
abstract: Ionic conductivity in a polymeric fuel cell requires water uptake. Previous theoretical studies of water uptake used idealized parameters. We report a parameter-free prediction of the water-swelling behavior of a model fuel cell membrane. The model polymers, poly(methyl-butylene)-block-poly(vinylbenzyl-trimethylamine), form lamellar domains that absorb water in humid air. We use the Scheutjens-Fleer methodology to predict the resulting change in lamellar structure and compare with x-ray scattering. The results suggest locally uniform water distributions. However, under conditions where a PVBTMA and water mixture phase-separate, the two phases arrange into stripes with a dilute stripe sandwiched between two concentrated stripes. A small amount of water enhances conductivity most when it is partitioned into such channels, improving fuel-cell performance.
authors: James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA.
authors: Daniel C
authors: DC
authors: Herbst
authors: James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA.
authors: Thomas A
authors: TA
authors: Witten
authors: Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors: Tsung-Han
authors: TH
authors: Tsai
authors: Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors: E
authors: E
authors: Bryan Coughlin
authors: Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA.
authors: Ashley M
authors: AM
authors: Maes
authors: Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA.
authors: Andrew M
authors: AM
authors: Herring