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

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

Corresponding author: f5xrb@fy.chalmers.se

Received: 28 February 2003
Accepted: 16 September 2003

Abstract

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 (β) relaxation, the confinement induces a relative enhancement (compared to the main α relaxation) of the effective dielectric strength of the β process. In bulk systems without a well-separated β 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 α relaxation. The results hence provide an explanation for the much debated excess wing often observed in the dielectric response of glass-formers.