Understanding nucleation efficiency of stereocomplex-crystallites on homochiral crystallization in poly (l-lactide)/poly (d-lactide) blends: Homogenization near crystal growth front

Abstract

Understanding the concurrent behavior of homochiral (HC) and stereocomplex (SC) crystallization in stereocomplex polylactide (SCPLA) is crucial for developing polymorphic SCPLA-based materials for a range of applications. This work explores the SC-nucleated HC crystallization behavior in symmetric, poly(ethylene glycol)-plasticized, and asymmetric SCPLA systems under non-isothermal and isothermal conditions. Different states of pre-existing SC crystals were created by annealing samples at various temperatures, and the nucleation efficiency (NE), Avrami exponents, and crystallization half-time of SC-nucleated HC crystallization were studied. Variations in the results observed can be linked to the concentration of 103 helices in local regions near the crystal growth front following SC crystallization. This work suggests that a dynamic equilibrium between thermal fluctuation, composition gradient-driven homogenization, and nucleation-driven aggregation processes control the concentration of these helices. While aggregation enriches local regions with 103 and 31 helices, promoting HC and SC nucleation but impeding random coil diffusion, homogenization dilutes this effect by driving these local segments to adapt to the matrix composition and conformation. This work offers new insights into the intricacies of SC-nucleated HC crystallization, which can benefit the design of polymorphic SCPLA-based materials.