Crystallization behavior of syndiotactic polypropylene: Effect of solvent of varying molecular size

Syndiotactic polypropylenes (s-PPs) were freeze-extracted from alkyl solvents of varying molar volume. Higher degree of crystallinity was found for s-PP recovered from hexadecane than that from octane by wide-angle X-ray diffraction. DSC analysis indicated that s-PP freeze-extracted from alkyl solvents of larger molar volume crystallized at a faster rate. FT-Raman spectra were used to characterize s-PP gels in octane and in hexadecane. It is found that interaction existed between the segments of s-PP chains and octane, while no interaction was found between s-PP and hexadecane, which may account for the faster crystallization rate and high degree of crystallinity.