Enhancement of PLLA Properties Through the Introduction of Stereocomplex Crystallites: A Comparative Study of Stereocomplex Formation Methods

ABSTRACT Stereocomplex poly(lactic acid) crystallites (SC‐PLA) has been demonstrated to be an effective modifier for enhancing the crystallization behavior and mechanical properties of PLA. This study systematically compares two SC‐PLA formation methods, namely external addition of pre‐formed SC‐PLA versus in situ melt‐induced formation of SC‐PLA, with respect to their effects on the microstructure and properties of PLLA. It is observed that pre‐formed SC‐PLA are uniformly dispersed in the PLLA matrix in an irregular shape when its content below 20 wt%, exhibiting relatively weak interfacial interactions. The SC‐PLA formed in situ via melt blending with Poly(D‐lactic acid) (PDLA) are dispersed in the PLLA matrix as spherical particles, and their surfaces begin to adhere each other as PDLA content increases to 10 wt%, eventually forming a stereocomplex crystallite network structure with enhanced interfacial adhesion. A reversal in crystallinity of SC‐PLA is observed between the L/SC‐20 and L/D‐10 samples, which corresponds to an inversion in viscoelastic behavior. Comparative analysis reveals that the blends prepared through in situ formation SC‐PLA exhibit superior heat resistance and mechanical performance compared with those fabricated by the external addition of pre‐formed SC‐PLA. These findings provide practical insights for the design and development of high‐performance PLA‐based materials.