DENSITIES OF STATE OF THE VIBRATIONAL LOW-FREQUENCY MODES FOR POLY(P-PHENYLENE VINYLENE) - A STUDY BY INELASTIC NEUTRON-SCATTERING

We report the phonon density of states in crystalline poly-(p-phenylen e vinylene). The results were obtained by incoherent inelastic neutron scattering methods using the time-of-night and the filter-analyser te chniques. By using stretch-oriented highly crystalline films the infor mation about the polarization of the modes has also been obtained. In the low-frequency range we observe a weak 56 cm(-1) feature that we as sign to phenyl-ring librational mode, and strong bands at 120 cm(-1) ( an intrachain torsional mode) and at 200 cm(-1), the latter possibly d ue to the whole-chain libration.