Advanced memory effects in the aging of a polymer glass
École Normale Supérieure de Lyon, Laboratoire de Physique (CNRS UMR5672) , 46, Allée d'Italie, 69364 Lyon Cedex 07, France
Corresponding author: a Sergio.Ciliberto@ens-lyon.fr
Revised: 20 November 2001
Published online: 15 January 2002
A new kind of memory effect on low frequency dielectric measurements on plexiglass (PMMA) is described. These measurements show that cooling and heating the sample at constant rate give an hysteretic dependence on temperature of the dielectric constant ϵ. A temporary stop of cooling produces a downward relaxation of ϵ. Two main features are observed (i) when cooling is resumed ϵ goes back to the values obtained without the cooling stop (i.e. the low temperature state is independent of the cooling history) (ii) upon reheating ϵ keeps the memory of all the cooling stops (Advanced memory). The dependence of this effect on frequency and on the cooling rate is analyzed. The memory deletion is studied too. Finally the results are compared with those of similar experiments done in spin glasses and with the famous experiments of Kovacs.
PACS: 75.10.Nr – Spin-glass and other random models / 77.22.Gm – Dielectric loss and relaxation / 64.70.Pf – Glass transitions / 05.20.-y – Classical statistical mechanics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002