Morphology of the basal lamellar crystal and overgrown lamellae of poly (ε-caprolactone) / poly (vinyl methyl ether) blends isothermally crystallized at high temperatures

The morphology of the basal and overgrown lamellar crystals of PCL/PVME blends in ultrathin films are studied in detail. The blends were prepared from dilute solution with 60/40 composition ratios onto Si-substrate using the spin-coating method, melted above the equilibrium melt temperature, and subsequently crystallized at high temperatures. A truncated lozenge-shaped morphology of the crystals with stacks of lamellae layers (basal and overgrown lamellae) are observed by real-time atomic force microscopy. Depending on the crystallization conditions, the overgrown lamellae are found on-center and/or off-center on the basal lamellar crystal, correlated with the primary- or self-induced nucleation processes. During the crystallization process, the growth rate in the longitudinal direction is found double to the lateral direction. Electron diffraction (ED) pattern reveals these lamellae have very high crystallographic order; a characteristic similar to the single crystals. The overgrown lamellae have similar characteristics to the main basal lamellar crystal. Real-time AFM observation assisted with electron diffraction patterns shows a clear correlation the morphology and the nucleation process of the basal lamellar crystal and the overgrown lamellae of the blends.