Molecular dynamics of poly(glycolide) and poly(glycolide-co-L-lactide) during isothermal cold crystallization

An investigation was carried out on the molecular dynamics of poly(glycolide) and poly(glycolide-co-L-lactide) copolymer in their wholly amorphous state and during cold crystallization at 70 and 80 °C. Experimental results were generated over a wide range of temperature and frequency by broad-band dielectric relaxation spectroscopy. The variation of the average relaxation time (related to the frequency at maximum loss for the main α-relaxation) has been studied during cold crystallization. This variation has been found to be dependant on the crystallization temperature and type of polymer, suggesting different progress of the spherulitic morphology in each case. The temperature dependence of the average relaxation time for wholly amorphous samples has been analyzed. This behavior has been modelled by Havriliak–Negami and Vogel–Fulcher equations obtaining the most important parameters. Supporting evidence about the thermal behavior of the polymers has been obtained with differential scanning calorimetry. Complementarily, the evolution of the morphologies obtained during crystallization processes has been followed by optical microscopy.