Structure formation during isothermal crystallization of oriented isotactic polystyrene

Isothermal crystallization from the glassy state of oriented isotactic poly styrene (iPS) was studied using in situ Fourier transform infrared (FTIR) s pectroscopy and in situ wide-angle X-ray diffraction (WAXD) studies. The or iented amorphous films of iPS were prepared by rolling the amorphous iPS fi lm to a draw ratio of 3 or 4. In situ FTIR was used to investigate the orde ring process of polymer chains prior to crystallization by measuring the ch ange in the dichroic ratio with time, while in situ WAXD studies were used to investigate the development of the crystalline structure. The studies sh owed that the orientation process and the conformation change preceded crys tallization. This observation suggests that polystyrene chains undergo an o rdering process during the induction period of crystallization. The degree of orientation markedly increases with time in the induction period, sugges ting that heat treatment of oriented amorphous materials under constraint p rovides a useful method for processing highly oriented materials. (C) 2000 John Wiley & Sons, Inc.