Eur. Phys. J. B 17, 661-666 (2000)
https://doi.org/10.1007/s100510070105

Very fast relaxation in polycarbonate glass

¹ Laboratoire de PhysicoChimie des Matériaux LuminescentsUMR-CNRS 5620, Université Lyon I, 69622 Villeurbanne Cedex, France
² Département de Physique des MatériauxUMR-CNRS 5586, Université Lyon I, 69622 Villeurbanne Cedex, France
³ Institut Laue-Langevin, 38042 Grenoble Cedex, France

Received: 29 February 2000
Revised: 13 June 2000
Published online: 15 October 2000

Abstract

Relaxations in amorphous bis-phenol A polycarbonate are studied by neutron scattering, as a function of temperature below the glass transition. Two different processes are observed. One is very fast, with a characteristic time (~ 0.3 ps), that is independent of temperature and momentum transfer. Conversely the other is slower, with a time which is dependent on temperature and momentum transfer. The very fast localized anharmonic motion is interpreted by the overdamping of low-frequency vibrational modes, by nearby dynamic holes. The slower relaxation is thermally activated and momentum transfer dependent. It corresponds to molecular group motions and possibly to the short-time regime of the segmental relaxation.