Grating Harmony of Orderly-Banded Spherulites of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Tunable Structures

A detailed investigation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) blended with poly(vinyl phenol) (PVPh) at a 90/10 weight ratio reveals the significant impact of PVPh on crystallization and spherulite morphology. Because PVPh remains in a rigid, glassy state during PHBV crystallization, it restricts molecular movement, leading to a more controlled and organized morphology of the PHBV lamellae. Advanced microscopic analysis highlights the morphological sensitivity to crystallization conditions, with SEM images showing cracks and diverse lamellae orientations. Etching and fracturing expose the interior 3D lamellae architecture, revealing distinct ridge and valley regions where vertically oriented lamellae beneath ridges transition to horizontal lamellae in valleys, resulting in double ring-banded spherulites. Advanced synchrotron-radiation microbeam X-ray techniques provide additional insights into the polymorphic forms and self-assembly behavior of lamellae. The investigation also examines order-induced photonic phenomena by considering that the orderly-banded spherulites can exhibit iridescence. This comprehensive study enhances our understanding of PHBV crystal assembly, underscoring the sophistication of polymer self-assembly at the microscopic level.