Using depolarized light intensity to study the crystallization and degradation behavior of poly(l-lactic acid) and its blends with poly(ethylene oxide)

The crystallization and degradation behaviors of poly(l-lactic acid) (PLLA) and its blends with poly(ethylene oxide) (PEO) were investigated by depolarized light intensity (DLI). It was found that DLI is sensitive to study the degree of order in polymer thin film samples. The growth rate of the PLLA spherulites was increased by blending up to 80 % PEO, as it increased the chain mobility in the blend melts. At larger PEO compositions (i.e., 90 % PEO), the dilution effect dominates and the PLLA growth rate was retarded. Three distinct blend groups with respect to the blend composition were proposed: (1) 10–20 wt% PEO in which the PEO is not able to form any ordered structure in the binary blend; (2) 30–50 wt% PEO in which the PEO is able to form some order but not enough to develop spherulitic crystals; (3) 60–90 wt% PEO in which the PEO forms a network of spherulites throughout the pre-crystallized PLLA.