Nanostructures of Stereocomplex Polylactide in Poly(l-lactide) Doped with Poly(d-lactide)

Nanostructures of stereocomplex polylactide (sc-PLA) are obtained and studied in poly(l-lactide) (PLLA) doped with a low amount of poly(d-lactide) (PDLA) during successive melt-quenching, extrusion, spinning, and drawing processes corresponding to quiescent, shear flow, elongational flow, and tensioned annealing conditions, respectively. Nanogranules of predominantly sc-PLA are initially formed with rapid quenching in quiescent and shear flow, which developed into microspheres with slow quenching and uniform nanofibrils in elongational flow. While only amorphous or the -form PLLA is formed with the quenched melts and macroscopic fibers, the embedded nanogranules and nanofibrils are highly crystallized with the coexistence of sc-PLA and the -crystals. A 1D coalescence of nascent sc-nuclei into nanofibrils in elongational flow is preliminarily proposed to explain the structure evolution and the minor reinforcement of the nanofibrils on the macroscopic fibers.