Spherulitic Morphology and Radial Growth Kinetics of PHBV Grafted with PVP

摘要

The spherulitic morphology and radial growth rate of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) grafted with poly (N-vinylpyrrolidone) (PVP) were investigated by polarized optical microscopy (POM). All spherulites exhibit a typical black cross with a banded structure and absence of cracks: The band spacing decreased with decreasing isothermal crystallization temperature (T<,c>) for all samples. At the same T<,c>, the PVP groups decreased the spherulitic band spacing and radial growth rate (G) with increasing the graft ratio (GR%) of samples, indicating that the crystallization capability of grafted PHBV was weakened due to the steric hindrance of PVP side groups. Analysis of isothermal crystallization kinetics according to nucleation theories showed that both the surface free energy (σe) and the work of chain folding per molecular fold (q) of grafted PHBV increased with increasing GR% of samples.