Journal Article

PreJuSER-31136

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Experimental evidence by neutron scattering of a crossover from Gaussian to non-Gaussian behavior in the alpha-relaxation of polyisoprene

Arbe, A. ; Colmenero, J. ; Alvarez, F. ; Monkenbusch, M.FZJ* ; Richter, D.FZJ* ; Farago, B. ; Frick, K. H.

2003
APS College Park, Md.

This record in other databases:    

Please use a persistent id in citations: http://hdl.handle.net/2128/1284  doi:10.1103/PhysRevE.67.051802

Abstract: We report incoherent quasielastic neutron scattering experiments exploring the alpha-relaxation range in polyisoprene over an unprecedented range in momentum transfer Q. The data corroborate and validate earlier molecular dynamics simulations and reveal the existence of a crossover from Gaussian to non-Gaussian character of the main chain protons self-correlation function in the alpha-relaxation regime. The real challenge of the experiment was to push the neutron techniques to cover a Q range as wide as possible. By combining two neutron spin echo spectrometers and a backscattering instrument, we have been able to study the dynamics in a Q range of 0.1less than or equal toQless than or equal to4.7 A(-1). In the low-Q regime the shape of the relaxation function was found to be related to the dispersion of the relaxation times as predicted by the Gaussian assumption. At short distances or large Q, this relationship is strongly violated indicating a non-Gaussian regime. We have performed a detailed comparison between the experiments and simulations at different temperatures and found, apart from a temperature shift, complete agreement. Combining experiments and simulations led to a consistent interpretation in terms of a distribution of jumps underlying the diffusive motion of protons in the alpha process. This model leads to a time-dependent non-Gaussianity parameter that agrees nearly quantitatively with the simulations and exhibits all features resolved so far from various simulations.

Keyword(s): J

Note: Record converted from VDB: 12.11.2012

---

Contributing Institute(s):

1. Neutronenstreuung (IFF-NST)

Research Program(s):

1. Kondensierte Materie (M02)

Appears in the scientific report 2003
Notes: This version is available at the following Publisher URL: http://pre.aps.org

---

Database coverage:

---