Crystallization Pathway of Poly (Lactic Acid) Racemates in various initial states

Chain entanglement and spatial arrangements in the initial state (prior to crystallization) are the important factors to govern crystallization of polymer chains. Poly (lactic acid) racemates form stereocomplex crystal (SCC) by arranging alternating packing of the enantiomers. In this work, we investigate spatially proximity of PLA racemate glass and crystal formed by freeze-drying (FD) and subsequent annealing by using selectively ¹³C-labeled PLLA/PDLA blends and NMR crystallography. FD glass shows spatial heterogeneity including intimate mixing of the racemate (22%) and homo domains (78%) on several nm scales. Annealing at the melt induces a completely mixed structure (100%) at the segmental scale. In this talk, we will demonstrate how different initial structures affect SCC formation of PLA racemate (crystallization pathway).