Real-time crystallization study of poly(ϵ-caprolactone) by hot-stage atomic force microscopy

Abstract

The morphological development and lamellar growth kinetics of poly(ϵ-caprolactone) (PCL) were investigated in real-time by hot-stage atomic force microscopy (AFM). The morphology of PCL crystals grown in the melt was studied to obtain insight into the mechanism, which controls the lateral shape of the lamellae in this polymer. Melt-grown PCL crystals showed a truncated lozenge lateral shape, with curved or chair-like three-dimensional morphology. Similar lamellar morphologies were observed in larger crystal aggregates, i.e. hedrites, grown at lower crystallization temperatures in the melt. The individual lamellae in these crystal aggregates also showed an elongated truncated lozenge shape. The AFM examination of the hedritic morphologies revealed the dynamics of the dominant/subsidiary crystallization process. The use of a hot-stage allowed us to perform real-time observation of growth faces in different crystallographic directions. The results support previous evidence, which suggested that the elongated lamellar habit is related to growth rate anisotropy. Morphological observations suggest a mechanism including {110} growth faces. In addition, visualization of the lamellar morphology indicates that the PCL crystals are obtained under regime II crystallization conditions.