The nature of microphase separation in perfluorinated ionomers
LccQD 382 I45 R63 1994
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AbstractThe microstructural environment of the perfluorinated ionomers produced by Dow and Dupont have been investigated by the use of fluorescent probe techniques. The polarity of the interfacial region in these polymers was found to be more polar for the sulphonate than the carboxylate form, and with increasing ion content. The locations of cesium ion, iodide ion and copper (II) ion were all found to be different, and to change with ion content and the identity of exchange group. This is quantitatively explained in terms of a three phase model which is consistent with previous spectroscopic studies of perfluorinated ionomers. Pretreatment was found to have an effect on the microstructural and bulk properties of these polymers. The polarity of the interfacial region studied using fluorescent probes was found to change after swelling in ethanol and boiling in water. The interface appears to become more polar after swelling in ethanol and less polar after boiling in water. The sorbed water in the polymers was studied using near infrared spectroscopy. Its character was also found to change with pretreatment. The most significant effect of ethanol swelling was a subsequent increase in the relative amount of non-hydrogen bonded OH groups. For the boiling pretreatment, the main effect was to increase the average hydrogen bond strength of sorbed water. This is explained in terms of a structural rearrangement with ethanol swelling and an expansion in cluster size with boiling. The insulator-to-conductor percolative threshold for these polymers was found to occur at lower water contents than predicted for randomly distributed conducting sites. This is explained in terms of the connectivity among the clustering entities in the polymers. The threshold moves to even lower water contents for both ethanol and boiling pretreatments. This is again explained in terms of morphological rearrangements in the polymer structure.
Bibliography: p. 147-158.
CitationRobertson, M. A. (1994). The nature of microphase separation in perfluorinated ionomers (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/16320
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