Atomic-force microscopy analyses on dislocation in extinction bands of poly(Dodecamethylene terephthalate) spherulites solely packed of single-crystal-like lamellae

This study, using atomic-force and polarized-optical light (AFM and POM) microscopies on the extinction banded spherulites of poly(dodecamethylene terephthalate) (P12T) at high T_c = 110^◦C with a film thickness kept at 1–3 µm, has verified that banded spherulites can be composed of stacks of entirely single-crystal-like lamellae free of any twisting, flipping, or bending, and no branching of lamellae. Defects in the crystal packing of extinction bands are present in both intra-band and inter-band regions. The intra-band defects originate from the miss-match in spiral-circling into circular bands while the inter-band defects are in the interfaces between successive bands where single crystals in the ridge are jammed to deformation, then suddenly precipitate prior to initiating another cycle of banding. The fish-scale lamellae, at the initiation of a cycle, are orderly packed as terrace-like single crystals; conversely, near or on the defected regions, they are highly jammed or squeezed and deformed to beyond recognition of their original single-crystal nature.