Early stages of polymer melt crystallization

The early stage of crystallization of isotactic polypropylene was investigated by high brilliance X-ray scattering methods. The unprecedented detectivity allowed us to observe the appearance of crystalline nuclei prior to the onset of mesoscopic order. This observation is consistent with the nucleation and growth picture and excludes previously proposed spinodal-assisted mechanism of polymer crystallization. The early stage growth kinetics deviates from the empirical Avrami type description as suggested by cluster distribution models.