Synchrotron X‐Ray Analysis and Morphology Evidence for Stereo‐Assemblies of Periodic Aggregates in Poly(3‐hydroxybutyrate) with Unusual Photonic Iridescence

3D morphology of poly(3‐hydroxybutyrate) (PHB), crystallized in the presence of diluents of poly(1,3‐trimethylene adipate) and poly(ethylene oxide), is probed using a novel approach coupled with selective etching. For interpreting the mechanisms of crystal periodic aggregation, various microscopic techniques and synchrotron microbeam X‐ray analysis are used to observe the top surface in connection with the 3D crystal assemblies. Periodic grating architectures, with the cross‐bar pitch exactly matching with the optical band spacing, are proved in banded PHB. The crystals under the ridge branch out to spawn finer crystals orienting/bending horizontally underneath the valley band, repeating till species drainage or impingement. The grating structure in the banded PHB resembles many nature's iridescence crystals and is further proved by photonic reflection results as a critical breakthrough novel finding. Detailed 3D assembly is proved by synchrotron X‐ray analysis and is supported by direct morphology dissection evidence, and the grating architecture of the periodic poly(3‐hydroxybutyrate) (PHB) aggregates possess novel properties of photonic‐crystal iridescence, never reported or discovered before for such polymeric crystals.