Atomic force microscopy characterization and interpretation of thin-film poly(butylene adipate) spherulites with ring bands

Atomic force microscopy characterization has been conducted to reveal the morphological difference between single-ring bands in poly(butylene adipate) (PBA). Furthermore, morphological features of the ring-less Maltese-cross spherulites are compared to the ring-band spherulites. Periodic changes in height seem to be common for either the ring-band or ring-less (Maltese-cross) crystal domains; however, the steepness in height change is greater for the ring-band crystal, while height change in the ring-less crystal exhibits a terrace-like layer pattern. In the ring-band crystal region, the lamellar stalks, which taper off to pointed needle-like stalks, monotonously protrude out of the layers of softer materials, with no signs of twisting, bending, or turning. In contrast, all lamellae in the ring-less (Maltese-cross) crystal region are uniform platelets arranged like flower petals in a layered pattern.