Differences are seen in the mechanism of lamellar assembly of two alternating banded regions (valley and ridge) of phthalic acid spherulites solvent-evaporation crystallized at either higher (80 °C) or ambient (28 °C) temperature.

Poly(butylene adipate) (PBA) self‐aggregation into unique periodicity correlating to its interfacial photonic properties is probed in detail. Investigations on the unique periodic morphology and top‐surface and interior architectures in specifically crystallized PBA are focused on its novel photonic patterns with periodic gratings. Detailed analysis of the interior lamellae from ringless to periodically ordered aggregates (crystallized at 33–35 °C vs. Tc = 30 °C) serves as ideal comparisons. Each interior arc‐shape shell is composed of tangential and radial lamellae mutually intersecting at 90o angle. The interior layer thickness in SEM‐revealed arc‐shape shish‐kebab shell is exactly equal to the optical inter‐band spacing (≈6 µm). A 3D assembly mechanism of periodically banded PBA crystals is proposed, where the orderly arrays on top surfaces as well as the interior microstructures of strut‐rib alternate‐layered assembly resemble nature's photonic crystals and collectively account for the interfacial photonic properties in the ring‐banded PBA crystal that is novel and has potential applications in future.

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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.