Evidence of Early Stage Precursors of Polymer Crystals by Dielectric Spectroscopy

Dielectric spectra of the polyester poly(propylene succinate) were measured upon crystallization. For this model aliphatic polyester the $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ relaxations appear simultaneously and are well resolved in the experimental frequency window. During isothermal crystallization, this fact allows one to use the $\ensuremath{\beta}$ relaxation to characterize the crystalline structural development while the $\ensuremath{\alpha}$ relaxation provides information about the evolution of the amorphous phase dynamics. In this way structure development and dynamics evolution can be characterized by a single experiment during the crystallization process. The unambiguous analysis of the dielectric loss clearly supports the existence of precursors of crystallization in the induction period.