Complex Impedance Studies of S-SEBS Block Polymer Proton-Conducting Membranes
Abstract
Water uptake, swelling, H pulsed gradient spin-echo nuclear magnetic resonance (NMR) and variable temperature and pressure complex impedance/electrical conductivity studies have been carried out on the sulfonated styrene/ethylene-butylene/styrene (S-SEBS) triblock polymer proton conducting membrane. All of the data show different characteristics above and below about 10 wt-% water. For example, the diffusion coefficients, D from NMR and D, calculated from conductivity data (which are the same to within experimental uncertainty), show different dependence on water above and below about 10 wt-% At high water content, the properties of S-SEBS are similar to those for Nafion 117, proton transport being similar to that in bulk water. For low water contents, however, the materials are different. For low water content S-SEBS, the variation of the conductivity with temperature is Arrhenius while that for Nafion 117 is not. The variation of the electrical conductivity with pressure gives rise to activation volumes on the order of 14 cu cm/mol while those for Nafion 117 are about four times larger. These results indicate that proton transport in low water content S-SEBS occurs via a thermally activated process (ion motion via energy barriers) which is consistent with the rigid side chains in that material.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2000
- Accession Number
- ADA379960
Entities
People
- C. A. Edmondson
- G. E. Wnek
- John J. Fontanella
- S. G. Greenbaum
- S. H. Chung
Organizations
- United States Naval Academy