BOSON PEAK, NANOSTRUCTURE AND RELAXATION OF GLASSES

In previous papers the low-energy vibrational density of states (boson peak) observed in poly(methyl methacrylate) glass by inelastic neutro n scattering is interpreted by the existence of more cohesive nanodoma ins separated by softer interfacial zones. The log-normal size distrib ution of nanodomains, that fits the experiment, is justified by the pr ocess leading to glass-transition. The fast relaxation in the glass ob served by the quasielastic light and neutron scatterings, and the slow one revealed by the dynamic hole volume as deduced from positron anni hilation lifetime spectroscopy, are closely related. A model for the i nterdependence of both relaxations is proposed. The consequences of th e relaxational dynamics on viscosity and glass transition are discusse d. (C) 1998 Elsevier Science B.V. All rights reserved.