Europhys. Lett.
Volume 71, Number 2, July 2005
Page(s) 262 - 268
Section Condensed matter: structural, mechanical and thermal properties
Published online 10 June 2005
Europhys. Lett., 71 (2), pp. 262-268 (2005)
DOI: 10.1209/epl/i2005-10079-1

The decisive influence of local chain dynamics on the overall dynamic structure factor close to the glass transition

J. Colmenero1, 2, 3, A. Arbe1, F. Alvarez1, 2, A. Narros2, M. Monkenbusch4 and D. Richter4

1  Unidad Física de Materiales (CSIC-UPV/EHU) - Apartado 1072 E-20080 San Sebastián, Spain
2  Departamento de Física de Materiales (UPV/EHU) - Apartado 1072 E-20080 San Sebastián, Spain
3  Donostia International Physics Center - Apartado 1072 E-20080 San Sebastián, Spain
4  Institut für Festkörperforschung, Forschungszentrum Jülich GmbH D-52425 Jülich, Germany

received 11 April 2005; accepted 23 May 2005
published online 10 June 2005

We present molecular-dynamics simulations on 1,4-polybutadiene performed $\approx 20$$\un{K}$ above the glass transition Tg and relate them to measurements of the dynamic structure factor obtained by neutron spin echo spectroscopy. In real space the simulation data display two well-separated dynamical processes: anomalous diffusion and local hopping. A real-space analysis allows a unique identification of both processes. The obtained results lead to a rationalization of most of the various and very different experimental results reported so far in this system and facilitate a general understanding of why close to Tg the local dynamics may globally dominate the dynamic structure factor.

64.70.Pf - Glass transitions.
83.10.Rs - Computer simulation of molecular and particle dynamics.
61.12.Ex - Neutron scattering (including small-angle scattering).

© EDP Sciences 2005