Polymorphism of syndiotactic polystyrene. Morphology of the solvent-induced crystalline forms

The morphology of the delta and gamma forms of syndiotactic polystyrene (sPS) was investigated using scanning electron microscopy. The crystalline forms, delta and gamma, characterized by the chains in helical conformation, were obtained by solvent-induced crystallization from the amorphous glassy polymer. Dichloromethane and acetone were used to obtain the delta and the gamma form, respectively. The last form was obtained by thermal treatments of the delta form, too. The surface of the solvent-crystallized samples shows a texture characterized by oriented elements and cavities, whereas the internal part is microspherulitic in the case of the delta form and is more complex in the gamma form. At variance, the gamma form obtained by annealing the delta form shows a much more regular microspherulitic texture.