LIGHT-SCATTERING-STUDIES OF HIGH-FREQUENCY RELAXATION PROCESSES IN ORGANIC GLASS FORMERS

We describe recent light scattering measurements performed on two smal l molecules, metatoluidine and salol, and one polymer, 1-4 cis-trans p olybutadiene, in their undercooled phase. For the small molecules, the alpha-relaxation times deduced from the isotropic and anisotropic spe ctra are different and we propose, through different experiments, that the latter spectra are related to the reorientation motion of the mol ecules, the dynamics of which follows some of the MCT predictions. For polybutadiene, a broad and rather flat spectrum dominates the anisotr opic spectrum, while the damping of the acoustic phonons is possibly d ue to their coupling to intrachain conformation motions.