| Abstract: | The influence of thermal history on the morphology of bulk-crystallized isotactic polystyrene was investigated. Results from x-ray diffraction (both wide- and small-angle), DSC experiments, and electron microscope observations, were combined to define the influence of thermal history on the fold surface free energy σe. lamellar thickness, and crystallite perfection. The increase of the melting point with crystallization temperature is not only the consequence of an increase in lamellar thickness, but also of marked decrease of σe. Annealing above the crystallization temperature results in a fast reorganization to a more stable structure, as reflected in an increase in melting point. This reorganization, depending on the crystallization temperature, involves an increase in lamellar thickness, a decrease of σe, and eventually an increase in crystallite perfection. |
