NORMAL VIBRATIONS AND THEIR DISPERSION IN SYNDIOTACTIC POLYSTYRENE

Normal modes and their dispersion are obtained for syndiotactic polyst yrene (sPS) in the planar zigzag and s(2/1)2 helical conformations. Co mparison is made with the spectra of isotactic polystyrene (iPS) to id entify the conformation-sensitive modes; for example, the 1221 cm-1 mo de is identified as a skeletal mode sensitive to chain structure and i t also shows maximum dispersion. Bunching of dispersion curves and the ir intersection are among the characteristic features which are discus sed. A check on the dispersion curves below 400 cm-1 is made from the spectra of polystyrene oligomers.