DSC and TEM investigations on multiple melting phenomena in isotactic polystyrene

The multiple melting behavior and morphologies of isotactic polystyrene (iP S) isothermally crystallized from the glassy state have been investigated b y differential scanning calorimetry (DSC) and transmission electron microsc opy (TEM). The combination of thermal analysis and morphological results in dicates that two lamellar populations are responsible for the so-called dou ble melting behavior in iPS. The low-temperature melting peak is attributed to the melting of less perfect (thinner or defect containing) subsidiary l amellae formed in the framework of the dominant (thicker or more perfect cr ystalline) lamellae upon isothermal crystallization. The high-temperature o ne is mainly due to the melting of the dominant thicker lamellae, and to so me less extent, the melting of a recrystallized population coming from the melted defect lamellae during the heating process in DSC. (C) 2000 Kluwer A cademic Publishers.