The crystallization conditions for the preparation of different modifications of the orthorhombic form (fl form) of syndiotactic polystyrene (s-PS) are described. Crystallizing from the melt produces the fl' or form depending on the cooling rate. Crystallization by casting a film from o-dichlorobenzene solutions produces clathrate structures (6 form) at low temperatures (T < 130°C) and ordered fl" modifications at higher temperatures. In particular, modification very close to the fl" limiting one are obtained in the temperature range 130-140°C. Recrystallization of the fl form has been detected by differential scanning calorimetry and studied by X-ray diffraction analysis of the annealed samples. These studies indicate that the recrystallization of the fl' form in the melting region does not involve a fl' to fl" transition, but only morphological changes. Models for the chain packing of the limiting modifications of the fl form are suggested, by quantitative comparisons of the X-ray diffraction intensities and calculated structure factors.
Посилання на статтю:
On the crystal structure of the orthorhombic form of syndiotactic polystyrene / C. De Rosa, M. Rapacciuolo, G. Guerra, V. Petracconeand P. Corradini // Polymer. – 1992. – Vol 33. – P. 1423-1428.