Intra- and inter-molecular dynamics in glass-forming liquids

Abstract

The intra- and inter-molecular interactions of salol and polystyrene, as low molecular weight and polymeric glass-forming model systems, are studied by Fourier-transform infrared (FTIR) spectroscopy and Broadband Dielectric Spectroscopy (BDS). By analysing the temperature dependencies of specific IR absorption bands it is demonstrated that each molecular moiety in the glass-formers has its own signature in the course of the dynamic glass transition: while some do not show any change at the calorimetric glass transition temperature others exhibit a pronounced kink. The effects cannot be attributed solely to microscopic thermal expansion, but instead indicate gradual conformational changes. The ease of application of this approach to a variety of systems in different geometries and external conditions can assist the modelling of glasses and the understanding of the coupling between the glass transition and molecular-level dynamics.