Lamellar assembly and orientation-induced internal micro-voids by cross-sectional dissection of poly(ethylene oxide)/poly(L-lactic acid) blend

Micro-lamellar patterns and orientation-induced micro-voids (cracks) in spherulites are probed in step-crystallized blends of two crystalline polymers: poly(ethylene oxide) (PEO) and low-molecular-weight poly(L-lactic acid) (PLLA) in different weight fractions, using polarizing light optical microscopy (POM), and scanning electron microscopy (SEM) with water-etching technique. It is revealed that blend composition led to entirely different PLLA lamellar regularities and void patterns. Water-etching into interiors of PEO/PLLA blends show 3D assembly of PLLA lamellae patterns. It is an important datum for structure modeling of banded polymer spherulites in bulk state. The mechanisms for the void/crack patterns and lamellar orientation are exemplified via dissecting into interior spherulites of bulk-form samples.