Fourier transform infrared spectroscopic study of transitions above T g in atactic polystyrene

Fourier transform infrared spectroscopy (FT‐IR) has been applied to the study of the molecular mechanisms of transitions of atactic polystyrene above T g . Intensity measurements of vibrational modes as a function of temperature revealed two transitions above T g , which are designated as T u and T ′ u . T ′ u is independent of molecular weight as opposed to the molecular weight dependent T u whose behavior is similar to T g . Infrared measurements are more sensitive to T ′ u than T u . Conformationally sensitive bands show that T ′ u may be related to disruption of local order where there is a negligible barrier to conformational change.