COLD CRYSTALLIZATION OF ISOTACTIC POLYSTYRENE

Thermal crystallization from the glassy state was investigated for iso tactic polystyrene (iPS) at three temperatures (140 degrees C, 170 deg rees C, and 200 degrees C) for different times. The crystallized sampl es were analyzed by x-ray diffraction, differential scanning calorimet ry (DSC), and transport properties of dichloromethane vapor. X-rays an d DSC give very similar values of crystallinity. At variance, sorption measurements indicate a fraction of amorphous phase much lower than t he previous. The presence of a mesophase, impermeable to the vapors at low activity, was hypothesized. Its value is constant for annealing a t 140 degrees C, whereas it decreases with time at 170 degrees C and 2 00 degrees C, in correspondence with an increase of the crystalline fr action.