Microstructural Periodic Arrays in Poly(Butylene Adipate) Featured with Photonic Crystal Aggregates

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. PBA interior lamellar assembly in 3D frames in packing to periodic patterns is shown. This work clearly demonstrates that the periodic bands possess structured orders in top‐surface topology and successive interior crystal layers, with the radial lamellae growing as rib‐branches from the “strut” ones, which are capable of interfering with photo light to produce some levels of iridescence. Micro‐ and nano‐structural arrays in 3D periodic gratings lead to photonic properties.