Kinetics and morphologies of syndiotactic polystyrene crystallized isothermally over a wide temperature range

Time-resolved Fourier transform infrared (FTIR) spectroscopy was used to investigate the crystallization kinetics of syndiotactic polystyrene (sPS) for the first time, and the results were compared with those obtained with differential scanning calorimetry (DSC) and depolarized light scattering (DPLS). Isothermal crystallization either from the melt by cooling or from the glass by heating was used to determine the temperature (T_c) dependence of the crystallization rate (k). The derived values of k were in good agreement with the results obtained with other tools over the accessible T_c ranges 250−262 °C and 110−135 °C for melt and cold crystallization, respectively. Based on the derived k and the crystal growth rates obtained from DPLS and optical microscopy (OM), the density of primary nucleation was readily calculated. The magnitudes of the nucleation densities in the cold-crystallized samples were ~5−6 orders higher than those of the melt-crystallized samples despite the similar k values. The novelty of our work lies in revealing that the volume-filling spherulites of the cold-crystallized sPS had modulated structure, reminiscent of spinodal decomposition. Thus, the nucleation pathway for cold crystallization is relevant to spinodal-assisted nucleation, which significantly enhances the nucleation density.