Study of reorientational dynamics during real-time crystallization of absorbable poly(p-dioxanone) by dielectric relaxation spectroscopy

Abstract

The real-time crystallization of absorbable poly(p-dioxanone) (PDS) was studied by dielectric relaxation spectroscopy. The dipole dynamic changes in the diminishing amorphous phase were investigated over a wide range of crystallization conditions. The location, shape, and magnitude of the a relaxation and the apparent activation energy were monitored and compared before and after the onset of crystallization. We observed no correlation between the degree of crystallinity and the location (hence, the most probable relaxation time, τ) of the a relaxation from just after the initiation up to the latest stages of the isothermal crystallization. However, an abrupt change in the intensity of the a process and the apparent activation energy allowed for the precise detection of the onset of crystallization. This was probably caused by a reorganization of dipole units occurring a few moments before the crystallization began. As crystallization proceeded, an asymmetric broadening of the a peak was observed that was directly influenced by the appearance of a new lower frequency process that originated in the highly confined amorphous portion located inside the spherulites. Finally, PDS crystallization kinetics determined from the changes of the relaxed permittivity with time are discussed and compared with calorimetric and optical microscopy data.