A series of long-chain branched polylactide (LCB PLA)/poly(D-lactic acid) (PDLA) blends with different low amounts of PDLA were prepared by a solution blending method. The formation of stereocomplex (SC) crystallites in LCB PLA/PDLA blends during a quenching process was proved by differential scanning calorimetry (DSC) and dynamic rheological frequency sweep, and the content of SC crystallites increased as the PDLA composition increased. The morphological evolution of LCB PLA/PDLA blends during crystallization at 130°C was traced by polarized optical microscopy (POM), disclosing the separate growths of SC crystallites and PLA homocrystallites. The crystallization kinetics of LCB PLA/PDLA blends was investigated by rheometry, which was accelerated dramatically with increasing PDLA composition mainly due to the nucleation density enhancement. In particular, a two-stage crystallization process was found for LCB PLA/PDLA blends with PDLA compositions of 5 and 10 wt%, evidenced by the two plateaus in the storage modulus-time curves, which were apparently related to the existence of an LCB structure. The DSC result further confirmed that both SC crystallites and homocrystallites of PLA coexisted in LCB PLA/PDLA blends, with homocrystallites appearing much later as compared to SC crystallites, even after the complete crystallization of SC crystallites.

https://doi.org/10.1021/acs.iecr.1c00377