High-frequency dynamics of glass-forming polybutadiene

D. Fioretto, U. Buchenau, L. Comez, A. Sokolov, C. Masciovecchio, A. Mermet, G. Ruocco, F. Sette, L. Willner

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Abstract

Inelastic x-ray measurements of polybutadiene are reported, performed over a wide temperature range covering both the glass and the liquid phase. At each temperature, the frequency position [Formula Presented] and the width [Formula Presented] of the inelastic peaks of the spectra have been obtained for different values of the scattering vector [Formula Presented]. A linear behavior of [Formula Presented] for [Formula Presented] has been revealed, allowing the determination of the unrelaxed sound velocity [Formula Presented] Consistently with the results obtained in different glass-forming systems, the Q dependence of [Formula Presented] is well represented by a [Formula Presented] law. For [Formula Presented] the values of [Formula Presented] overtake those of [Formula Presented] and the acousticlike excitations progressively loose their propagative nature. In the glass, [Formula Presented] compares well with previous Brillouin Light Scattering (BLS) determinations, while in the liquid the BLS sound velocity shows a steeper temperature dependence related to the structural relaxation. The temperature behavior of the nonergodicity factor has been derived both from [Formula Presented] and [Formula Presented] (in the liquid phase) and from the ratio between elastic and inelastic intensities of inelastic x-ray scattering spectra (in the whole investigated temperature range). Both temperature and Q behavior of this quantity might be consistently interpreted in the framework of the mode coupling theory.

Original languageEnglish
Pages (from-to)4470-4475
Number of pages6
JournalPhysical Review E - Statistical, Nonlinear, and Soft Matter Physics
Volume59
Issue number4
DOIs
StatePublished - 1999
Externally publishedYes

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