Europhys. Lett.
Volume 64, Number 5, December 2003
Page(s) 675 - 681
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00615-y
Europhys. Lett., 64 (5) , pp. 675-681 (2003)

Confinement effects on the excess wing in the dielectric loss of glass-formers

R. Bergman, J. Mattsson, C. Svanberg, G. A. Schwartz and J. Swenson

Department of Applied Physics, Chalmers University of Technology SE-412 96 Göteborg, Sweden

(Received 28 February 2003; accepted in final form 16 September 2003)

We present results from dielectric spectroscopy on four molecular glass-formers, both in bulk and in confined geometry. For systems exhibiting a well-resolved secondary ( $\beta$) relaxation, the confinement induces a relative enhancement (compared to the main $\alpha$ relaxation) of the effective dielectric strength of the $\beta$ process. In bulk systems without a well-separated $\beta$ process a similar relative enhancement is found also for the contribution to the dielectric loss identified as the excess wing. The latter effect results in a bimodal loss, which suggests that the excess wing should be attributed to a relaxation process separate from, and thus not a feature of, the $\alpha$ relaxation. The results hence provide an explanation for the much debated excess wing often observed in the dielectric response of glass-formers.

64.70.Pf - Glass transitions.
77.22.Gm - Dielectric loss and relaxation.

© EDP Sciences 2003