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

• Published in: Europhysics letters Vol. 71; no. 2; pp. 262 - 268
• Main Authors: Colmenero, J., Arbe, A., Alvarez, F., Narros, A., Monkenbusch, M., Richter, D.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.07.2005
• Subjects: 61.12.Ex; 64.70.Pf; 83.10.Rs
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/epl/i2005-10079-1

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.