Volume 80, Number 3, November 2007
|Number of page(s)||5|
|Section||Interdisciplinary Physics and Related Areas of Science and Technology|
|Published online||25 September 2007|
On the momentum transfer dependence of the atomic motions in the -relaxation range. Polymers vs. lowmolecular-weight glass-forming systems
Donostia International Physics Center - Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain
2 Departamento de Física de Materiales (UPV/EHU) - Apartado 1072, 20080 San Sebastián, Spain
3 Unidad de Física de Materiales (CSIC-UPV/EHU) - Apartado 1072, 20080 San Sebastián, Spain
Accepted: 3 September 2007
By means of molecular dynamics simulations we have studied the momentum transfer dependence of the intermediate scattering function of the lowmolecular-weight counterpart of a glass-forming polymer. At Q ≥ 0.3 Å-1 we found a similar Q-dependence to that previously reported for many polymers. The relaxation time scales like , where β < 1 is the parameter corresponding to a stretched exponential description of the slow decay of Fs(Q, t). Moreover, at Q higher than about 1 Å-1 a crossover towards an approximate Q-2 scaling is observed. Thereby this behavior is not a consequence of the connectivity of polymer chains but a general feature of glass forming systems. Differences among polymers and low molecular glass-forming systems emerge at lower Q's, where the connectivity of the macromolecules prevents normal diffusion.
PACS: 83.10.Rs – Computer simulations of molecular and particle dynamics / 61.41.+e – Polymers, elastomers, and plastics / 61.12.Ex – Neutron scattering (including small-angle scattering)
© Europhysics Letters Association, 2007
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