A spectroscopic study of phase-transition kinetics in syndiotactic polystyrene

The degree and kinetics of a solid--solid phase transition in solution-cast syndiotactic polystyrene films have been measured with infrared spectroscopy. The transformation of crystallites containing a helical chain conformation into those containing an all-trans chain conformation is monitored by measuring the intensity of infrared bands assigned to each phase. The amount of phase transformation above the transition temperature is highly dependent upon sample morphology and therefore their thermal history. Imperfections in films cast from solution cannot be removed by annealing at low temperatures. Extensive phase transformation was observed to occur very rapidly above a critical temperature of 192 deg C for cast films annealed at 150 deg C. Films annealed at 170 deg C display a weak endotherm in differential scanning calorimetric measurements that is associated with the helical to all-trans crystal phase transition, while just above this temperature an exotherm related to the crystallization of amorphous material is found. Increases in the trans content vary linearly with the logarithm of time. Spectra, Graphs. 26 ref.--AA