Fabrication of stereocomplex-type poly(lactic acid) nanocomposites based on the selective nucleation of poly(vinyl acetate) modified cellulose nanocrystals.

The incorporation of biomass fillers into poly(lactic acid) (PLA) enantiomeric blends offers a novel strategy to promote stereocomplex (SC) crystallization while preserving the biodegradability of PLA. In this study, poly(vinyl acetate)-modified cellulose nanocrystals (CNC-PVAc) were prepared through a one-pot reaction and employed as nanofillers for PLA. The results indicate that CNC-PVAc enhances the crystallization of stereocomplex crystallites (SCs) while inhibiting the formation of homocrystallites (HCs). The selective nucleation induced by CNC-PVAc is closely associated with the enrichment of PVAc chains at the interface between CNCs and the PLA matrix. Due to the good miscibility between PVAc and PLA, PVAc enhances chain segment motility and suppresses the homocrystallization of poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA), thereby facilitating the pairing and crystallization of PLA enantiomers into SCs. Furthermore, the nucleation and reinforcing effects of CNC-PVAc play a synergistic role in determining the properties of PLA based nanocomposites. The fabricated nanocomposites exhibit significant improvements in yield strength, Young's modulus, and heat distortion resistance, while maintaining the original biocompatibility and degradability of PLA. Overall, this study elucidates the nucleation mechanism of polymer-grafted CNCs on PLA SCs, and expanding the application potential of biobased fillers in biodegradable polymers.