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Influence of cross-linking on the segmental dynamics in model polymer networks

AuthorsYu Kramarenko, V.; Ezquerra, Tiberio A. ; Sics, Igors; Baltá Calleja, Francisco José ; Privalko, V. P.
Issue Date1-Jul-2000
PublisherAmerican Institute of Physics
CitationJournal of Chemical Physics 113(1): 447 (2000)
AbstractIn an attempt to study the specific influence of cross-linking on the (alfa) relaxation in polymer networks, a series of model heterocyclic polymer networks (HPN) with well-defined cross-link densities and constant concentration of dipolar units were studied. Model HPN systems were prepared by simultaneous trimerization of 1,6-hexamethylene diisocyanate (HMDI) and hexyl isocyanate (HI). These HPN systems were characterized by dielectric relaxation spectroscopy in the 10–1 Hz<F<105 Hz frequency range and in the 123 K<T<493 K temperature interval. The (alfa) relaxation in these systems depends on network density and shifts toward higher temperatures as the cross-link density increases for high HMDI/HI ratios. Discussion of the (alfa)-relaxation shape in light of recent models indicates that segmental motions above the glass transition systematically experience a growing hindrance with increasing degree of cross-linking. Description of the temperature dependence of relaxation times according to the strong–fragile scheme clearly shows that fragility increases as polymer network develops.
Description6 pages, 6 figures, 3 tables.
Publisher version (URL)http://dx.doi.org/10.1063/1.481809
Appears in Collections:(CFMAC-IEM) Artículos
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