Anatomy into Interior Lamellar Assembly in Nuclei-Dependent Diversified Morphologies of Poly(L-lactic acid)

Sophisticated dissection into the interiors of the three different birefringent types of poly(l-lactic acid) (PLLA) spherulites via delicate fracturing across the thickness sections, coupled with proper etching techniques, was adopted to reveal the correlations between the diversified birefringence patterns and interior lamellae assembly. The three types of spherulites are circularly ringed spherulite (type 1), hexagon-shaped axialite (type 2), and circularly core-stripe dendrites (type 3). Such morphological diversification originates from different nuclei geometries. For all three different types (circularly ringed, hexagonal, and core-stripe) of PLLA aggregation into spherulites or dendrites/axialites, the dissected inner lamellar arrangement shares universal commonality of intersecting at a 60° angle in the intersection between different lamellar species, with distinct discontinuity in the grating structures being characteristic of all three types of aggregated PLLA spherulites. This kind of grating assembly of the interior lamellae appears to be universally justified among many ring-banded polymer spherulites.