Water sorption and dielectric relaxation spectroscopy studies in hydrated Nafion (R) (-SO3K) membranes

Tsonos, C; Apekis, L; Pissis, P

dc.contributor.author	Tsonos, C	en
dc.contributor.author	Apekis, L	en
dc.contributor.author	Pissis, P	en
dc.date.accessioned	2014-03-01T01:15:58Z
dc.date.available	2014-03-01T01:15:58Z
dc.date.issued	2000	en
dc.identifier.issn	0022-2461	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/13856
dc.subject	Dielectric Relaxation	en
dc.subject	Diffusion Coefficient	en
dc.subject	Diffusion Process	en
dc.subject	High Frequency	en
dc.subject	Potassium	en
dc.subject	Sorption Isotherm	en
dc.subject	Low Frequency	en
dc.subject	Water Content	en
dc.subject.classification	Materials Science, Multidisciplinary	en
dc.subject.other	PERFLUOROSULFONATE IONOMERS	en
dc.subject.other	POLYMERS	en
dc.subject.other	DIFFUSION	en
dc.subject.other	MORPHOLOGY	en
dc.subject.other	ISOTHERMS	en
dc.subject.other	ACRYLATE	en
dc.subject.other	SYSTEMS	en
dc.title	Water sorption and dielectric relaxation spectroscopy studies in hydrated Nafion (R) (-SO3K) membranes	en
heal.type	journalArticle	en
heal.identifier.primary	10.1023/A:1026782509106	en
heal.identifier.secondary	http://dx.doi.org/10.1023/A:1026782509106	en
heal.language	English	en
heal.publicationDate	2000	en
heal.abstract	Dynamic and equilibrium sorption isotherm measurements were carried out on hydrated perfluorosulfonate polymer membranes in potassium salt form (Nafion(R)-SO3K, 1190 EW), at 22 and 40 degreesC respectively. Despite the glassy state of the membrane the diffusion process is Fickian with an average diffusion coefficient D in the range 2.8-30 x 10(-9) cm(2)/s. The equilibrium sorption isotherms may be quantitatively analyzed according to the GAB equation for multilayer sorption processes up to the activity value of alpha = 0.79, which corresponds to 1.0 site-bound water molecules per (-SO3K) group. The analysis of the equilibrium sorption isotherm, using the method of Zimm and Lundberg, suggests clustering of the water molecules for activities alpha greater than or equal to 0.79. The apparent polymer-water interaction parameter chi.(Flory parameter), was found to have a maximum at alpha = 0.79 (1.07 < chi less than or equal to 1.95). Also, dielectric relaxation studies of the same hydrated Nafion(R) membranes have been carried out in the frequency range of 10(-2) - 5 x 10(6) Hz and in the temperature range of 223-295 K. Two relaxation mechanisms were observed which both sift to higher frequencies by increasing the water content. The low frequency relaxation mechanism is due to interfacial polarization which takes place in the hydrated ionic regions. The high frequency relaxation mechanism, is a dipolar mechanism which may be attributed to the rotation of (-SO3-) group-water complexes at the end of the side chains. (C) 2000 Kluwer Academic Publishers.	en
heal.publisher	KLUWER ACADEMIC PUBL	en
heal.journalName	JOURNAL OF MATERIALS SCIENCE	en
dc.identifier.doi	10.1023/A:1026782509106	en
dc.identifier.isi	ISI:000166294100025	en
dc.identifier.volume	35	en
dc.identifier.issue	23	en
dc.identifier.spage	5957	en
dc.identifier.epage	5965	en