Effect of Poly(Ethylene Glycol)-Poly(d-Lactide) Block Copolymers on the Microstructure and Performances of Poly(l-Lactide)/Rubber Blends

In this article, poly(ethylene glycol)-poly( d -lactide) (PEG-PDLA) block copolymers with different PEG chain lengths were synthesized and melt-mixed with poly( l -lactide) (PLLA) and rubber nanoparticles. The role of PEG-PDLA block copolymers in tailoring the microstructures and performances of PLLA/rubber blend were investigated in detail. It was found that high contents of stereocomplex (SC) crystals were generated in PLLA/rubber/PEG-PDLA copolymer blends, which induced rubber nanoparticles to agglomerate and form network-like structures. The size of rubber aggregates and continuity of rubber network-like structures first increased and then declined significantly as the PEG chain length increased. Resultingly, the impact toughness of PLLA/rubber/PEG-PDLA copolymer blends first remarkably increased to 74.1 kJ/m 2 and then decreased to 30.6 kJ/m 2 . Meanwhile, the elongation at break increased with increasing PEG chain length and little loss of tensile strength happened, revealing good stiffness-toughness balance performances of PLLA/rubber/PEG-PDLA copolymer blends. Moreover, the matrix crystallization rate of PLLA/rubber/PEG-PDLA copolymer blends could be greatly increased by increasing PEG chain length and the PLLA/rubber/PEG-PDLA copolymer blends exhibited much higher Vicat softening temperatures than PLLA/rubber blend, which confirmed the excellent heat resistance of PLLA/rubber/PEG-PDLA copolymer blends. These interesting findings suggested that PEG-PDLA block copolymers were highly conducive to prepare PLLA materials with outstanding comprehensive performances.