STRUCTURAL ORGANIZATION OF SYNDIOTACTIC POLYSTYRENE FILMS CRYSTALLIZED IN THE BETA-FORM

Syndiotactic polystyrene (sPS) films were obtained either by casting or by melt crystallization in the beta-form. Different thermal treatments of the melt led to mixed alpha and beta-forms. The structural organization was investigated by x-rays, transport properties, and Fourier transform infrared analysis. The beta-form is characterized by chains in zigzag planar conformation. For samples prevalently in beta-form, the fraction of impermeable phase, derived from sorption measurements, was found coincident with the fraction of crystalline phase derived from x-rays. In samples with mixed alpha and beta-forms, however, a fraction of mesophase is also present. The beta-form of sPS is stable to dichloromethane, whereas the alpha-form is transformed into a crystalline form with the chains in helical conformation. Nevertheless, when the relative fraction of beta-form is lower than a critical value, it also dissolves in liquid dichloromethane, undergoing the conformational transition into the helical form.