High-efficient crystallization promotion and melt reinforcement effect of diblock PDLA-b-PLLA copolymer on PLLA

Abstract

In this work, a diblock PDLA-b-PLLA copolymer (BCP) was synthesized and employed to modify commercial poly l-lactide (PLLA) subsequently. The morphology and performance of BCP/PLLA blends were investigated using the traditional poly d-lactide (PDLA)/PLLA blends as controls. The morphology of BCP/PLLA is more uniform than that of PDLA/PLLA, demonstrating the compatibility and interaction between stereocomplex (SC) crystals and PLLA matrix are optimized by the PLLA blocks in BCP. Under the same amount of PDLA (5 wt%), BCP/PLLA shows dramatically improved crystallization behavior and rheological properties compared with PDLA/PLLA. Especially the maximum relaxation time of the optimal BCP/PLLA is markedly extended to 39.24 s (which is 0.018 s for pure PLLA). These results reveal that the PLLA blocks in BCP play a significant role in the superior performance of BCP/PLLA. Therefore, this work may have important meaning for designing high-efficient modifiers of PLA.