Physical aging of molecular glasses studied by a device allowing for rapid thermal equilibration |
| |
Authors: | Hecksher Tina Olsen Niels Boye Niss Kristine Dyre Jeppe C |
| |
Affiliation: | Department of Sciences, DNRF Centre Glass and Time, IMFUFA, Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark. tihe@ruc.dk |
| |
Abstract: | Aging to the equilibrium liquid state of organic glasses is studied. The glasses were prepared by cooling the liquid to temperatures just below the glass transition. Aging following a temperature jump was studied by measuring the dielectric loss at a fixed frequency using a microregulator in which temperature is controlled by means of a Peltier element. Compared to conventional equipment, the new device adds almost two orders of magnitude to the span of observable aging times. Data for the following five glass-forming liquids are presented: dibutyl phthalate, diethyl phthalate, 2,3-epoxy propyl-phenyl-ether, 5-polyphenyl-ether, and triphenyl phosphite. The aging data were analyzed using the Tool-Narayanaswamy formalism. The following features are found for all five liquids: (1) The liquid has an "internal clock," a fact that is established by showing that aging is controlled by the same material time that controls the dielectric properties. (2) There are no so-called expansion gaps between the long-time limits of the relaxation rates following up and down jumps to the same temperature. (3) At long times, the structural relaxation appears to follow a simple exponential decay. (4) For small temperature steps, the rate of the long-time exponential structural relaxation is identical to that of the long-time decay of the dipole autocorrelation function. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|