The morphology and growth of PLA stereocomplex in PLLA/PDLA blends with low molecular weights

The linear poly(L-lactide) and poly(D-lactide) (PLLA, PDLA) with relative lower molecular weights were synthesized, and PLLA/PDLA blends at various content of PDLA were prepared by solution casting. The morphology and growth of poly(lactide) stereocomplex (PLA SC) were investigated by polarized optical microscope. Results revealed that the morphology of SC in the blends strongly depended on the content of PDLA and the annealing temperature. Dendritic and irregular SC with looser structure developed in the specimens with lower content of PDLA, and regular SC spherulites with birefringent and compact structure produced in the specimens with higher content of PDLA. The growth rate (G) of SC increased gradually as the content of PDLA enhanced in the blends. As the annealing temperature enhanced, the SC with brighter and more compact structure appeared. The G value increased at first before declining as the annealing temperature elevated from the 130 to 190°C. And the nonlinear behavior of the growth of SC in the dissimilar specimens was analyzed.