Interior dissection on domain-dependent birefringence types of poly(3-hydroxybutyrate) spherulites in blends

The mechanisms and correlations between the rotation of Maltese cross axis, optical birefringence types, and lamellar reassembly induced by phase-separation domains, in poly(3-hydroxybutyrate) (PHB)/poly(1,4-butylene adipate) (PBA). In this work, a novel approach via interior dissection into spherulites in correlations with the top-surface morphology of the PHB/PBA (50/50) blend crystallized at a series of Tc's with various domain sizes. The PHB/PBA blend is used as the model system in comparison to alternative blends of PHB with other polyesters of various extents of phase-separated domains. Domains of optimal sizes were found to be essential in lamellar reassembly, which strongly affects the birefringence types of spherulites. Via the proven approaches, this work expounds how domain sizes and lamellar reorientation in partially miscible blends cause changes in the birefringence types of PHB spherulites, while, in contrast, complete miscibility or extreme phase separation with large domains does not.