The low-frequency Raman-spectrum of lithium phenyl stearate and its relevance to polystyrene

The low frequency Raman spectrum of a surfactant molecule, lithium phenyl stearate, in a reversed hexagonal phase is reported. A broad peak, centred around 59 cm-1, is observed and shows similarities in both position and width with a peak in the spectrum of amorphous polystyrene. It is concluded that the origins of these peaks are similar, involving a phenyl group torsion. This similarity has important implications, in view of alternative models previously applied to polystyrene: it is suggested that 'structural' models, such as the elastic sphere and fracton models, can be dismissed as possible explanations of this particular Raman peak. One is left with the possibility that tunnelling in two-level systems is responsible for the Raman peak in both materials and for low temperature thermodynamic behaviour of polystyrene.