Light scattering studies of high-frequency relaxation processes in organic glass formers

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