Structural Evolution Process in Solvent‐Induced Crystallization Phenomenon of Syndiotactic Polystyrene

Abstract

AbstractStructural change has been traced in the solvent‐induced crystallization phenomenon of syndiotactic polystyrene through the time‐resolved measurements of infrared and Raman spectra and X‐ray diffraction. Immediately after the solvent is supplied to the glassy sample, the random coils start a micro‐Brownian motion and locally change to short regular helical segments after some induction time. These segments grow longer and gather together to form the crystal lattice. This crystallization occurs even at room temperature far below the original glass transition temperature (Tg = ca. 100°C), because Tg is shifted to ca. −90°C (in the case of chloroform) due to the plasticizing effect, as revealed by the temperature‐dependent infrared spectral measurement and the molecular dynamics calculation. The thus‐created sPS‐solvent complex was found to show a fast and reversible solvent exchange phenomenon between the originally‐existing solvent (toluene, for example) and the newly‐supplied different type of solvent (chloroform, for example). The time‐dependent measurement of wide‐angle and small‐angle X‐ray scatterings using a synchrotron radiation source revealed that the solvent exchange occurs with keeping both the columnar structure of the crystal and the stacked lamellar structure, and that the solvent exchange rate is in the order of chloroform > benzene > toluene, reflecting the difference in diffusion rate of solvent molecules and polymer‐solvent interaction.