Dielectric Relaxation Studies of Water-Containing Short Side Chain Perfluorosulfonic Acid Membranes

Document Type

Article

Publication Date

5-11-1992

Department

Polymers and High Performance Materials

Abstract

The storage and loss components of the complex dielectric permittivities of short side chain perfluorosulfonic acid membranes were determined as a function of water content, temperature, and membrane equivalent weight. As in our previous studies of electrolyte-containing long and short side chain perfluorosulfonate ionomers, a low-frequency graphical feature on isothermal loss spectra was identified that is suggested to be reflective of, and that crudely quantifies the tortuousity of, long-range (intercluster) proton-conductive pathways. When the long-range ion transport contribution was subtracted from the loss spectra, a distinct bimodal relaxation was uncovered. It is suggested that these two relaxation peaks are a manifestation of two distinct types of hydrated polar clusters. At least one of the peaks is assumed to arise from a cluster/TFE interfacial polarization that fluctuates with a characteristic frequency as indicated by the maximum loss factor. Finally, preliminary studies suggest that the Cole-Cole distribution of relaxation times parameter for nominally dry membranes may be an index of distribution of cluster size or of cluster structure.

Publication Title

Macromolecules

Volume

25

Issue

10

First Page

2739

Last Page

2745

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