Effect of isothermal crystallization on the amorphous phase mobility of polycarbonate/poly(ε-caprolactone) blends

Polycarbonate/poly(ε-caprolatone), PC/PCL, amorphous miscible blends with 90/10 and 80/20 composition in weight, have been studied by X-ray diffraction and broad-band dielectric spectroscopy. The molecular dynamics for the high Tg component segmental mobility have been followed by analyzing the isothermal dielectric losses as a function of frequency with Havriliak-Negami distributions. The PCL plasticization effect is observed as a lowering of the Vogel-Tammann-Fulcher terminal temperature without any significant change in the other relaxation parameters. The isothermal crystallization process of the 90/10 PC/PCL blend has been studied in real time both by following the decrease of mobile amorphous material from the variation of the dielectric losses, and by wide angle X-ray scattering to follow the crystal growth. Quantitative comparisons show the disappearance of much higher amounts of mobile amorphous chains than those that are transferred to the crystallites. The existence of a rigid amorphous phase in the blend is established in non-negligible amounts as the isothermal crystallization of PC develops. The remaining mobile amorphous phase has unchanged dynamics.