Due to the extremely wide crystallization temperature
range of
chemically jointed PA6 blocks, three types of spherulitic morphologies
were found in poly(ε-caprolactone)-b-polyamide
6-b-poly(ε-caprolactone) (PCL-b-PA6-b-PCL), including conventional ring-banded
spherulites, special spherulites with a curve-like morphology, and
composite spherulites with the above two characteristics. The formation
conditions, internal factors, and the lamellar orientation and assembly
of different spherulites have been studied in detail. It was found
that the PCL spherulites with a curve-like morphology can form only
when PCL and PA6 blocks crystallize simultaneously, whereas the ring-banded
spherulites can form regardless of whether PA6 is amorphous or crystallized.
The morphological results show that the ring-banded spherulites are
composed of lamellae with different orientations along the radial
direction, while spherulites with a curve-like morphology are composed
of different stacked lamellae (flat-on lamellae and tilted flat-on
lamellae) arranged alternately along the tangential direction. The
appearance of unusual spherulitic morphology may result from different
internal stress induced by chemically jointed PA6 blocks under diverse
crystallization conditions.