Formation and stabilization of crystal nuclei in isotactic polybutene-1 aged below glass transition temperature

摘要

Aging of glassy isotactic polybutene-1 (iPB-1) below the glass transition temperature (T-g) leads to remarkable acceleration of the subsequent isothermal crystallization due to the promotion of crystal nuclei. The formation and development of crystal nuclei during aging below T-g and during heating to the crystallization temperature have been probed by fast scanning chip calorimetry. The size and stability of the crystal nuclei change with the aging time. A short aging below T-g can only induce nuclei with small sizes which can grow into bigger stable ones during the heating process above T-g if the heating rate is not high enough. With a prolonged aging time below T-g, bigger stable nuclei can also be developed, and its number increases till reaches a maximum value. These results suggest that noncooperative local motions rather than cooperative segmental motions in glassy iPB-1 are responsible for the formation of crystal nuclei during aging below T-g.