Phase behaviour of poly(l-lactic acid) (PLLA) and its blends with poly(ethylene oxide) (PEO)

Abstract

A combination of polarized light optical microscopy (PLOM), scanning electron microscopy (SEM), and total depolarized light intensity (DLI) investigations were performed to understand the phase behaviour and micro-level morphology of melt-crystallized poly(l-lactic acid) (PLLA) and its blend with poly(ethylene oxide) (PEO) before and after enzymatic degradation. Three distinct blend groups with respect to the blend composition have been identified: (i) 10--20 wt% PEO in which the PEO is not able to form any ordered structure in the binary blend; (ii) 30--50 wt% PEO in which the PEO is able to form some order but not enough to develop spherulitic crystals; (iii) 60--90 wt% PEO in which the PEO forms a network of spherulites throughout the pre-crystallized PLLA. The predominant lamellar structure of the PLLA component is concluded to be edge-on and flat-on in group (ii) and (iii), respectively.