Novel determination of the crystallinity of syndiotactic polystyrene using FTIR spectrum

The crystallinity and crystallization behavior of syndiotactic polystyrene (s-PS) α- and β-crystals have been thoroughly examined using the Fourier Transform Infrared (FTIR). It is shown that absorptivity ratio of respective absorbances of “α-crystal/amorphous, aα” and “β-crystal/amorphous, aβ” can be quantitatively determined using FTIR spectra ranging from 865 to 820 cm−1. Results from curve fitting show that both absorptivity ratios of aα and aβ are 0.178±0.005 and 0.272±0.005 for α- and β-crystal absorbances, respectively. The crystallization rate and crystallinity of α-crystal calculated from the absorptivity ratios are higher than that of β-crystal crystallized at 240°C for the same isothermal duration in thin film sample. The formation of β-crystal is thermodynamically more favorable while of α-crystal is kinetically more favorable from FTIR spectra.