The effects of thermal treatments on the phase organization in some po
lymorphic forms of syndiotactic polystyrene have been investigated. in
particular the thermal stability of the delta form was studied using
x-ray diffraction and infrared spectroscopy as analytical techniques.
The obtained results show that this form, characterized by chains in h
elix conformation, is affected by nonequilibrium phenomena. Moreover,
the transition from the delta to the gamma form occurs through an inte
rmediate form which maintains the helix chain conformation but partial
ly loses the crystalline order.