Probing into the Selective Nucleation Mechanism of Poly(methyl methacrylate) Modified Cellulose Nanocrystals in Enantiomeric Poly(lactic acid) Blends

Despite the superior performance of stereocomplex crystallites (SCs) formed between poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA), achieving exclusive SC crystallization based on environmentally friendly strategies remains a challenge. This study systematically investigates the impact of poly(methyl methacrylate) (PMMA)-modified cellulose nanocrystals (CNCs-PMMA) on the crystallization behavior and phase evolution of enantiomeric PLA blends. Experiments demonstrate that CNCs-PMMA acts as an effective nucleating agent for SCs, increasing the nucleation density, crystallinity, and relative fraction of SCs. Exclusive formation of SCs is achieved with the addition of 3 wt % CNCs-PMMA. By comparing the crystallization behavior of PLLA/PDLA/PMMA triple blends, the selective nucleation mechanism of CNCs-PMMA is elucidated. First, the dilution effect of PMMA enriched at the CNCs/PLA matrix interface inhibits homocrystallization, thereby maximizing the thermodynamic advantages of SC crystallization and the inherent nucleating effect of CNCs. Second, the CNC filler network improves the compatibility between PLA enantiomers while also suppressing the phase separation between high-molecular-weight components. Overall, this work reveals the selective nucleation mechanism of polymer-grafted CNCs on SCs and expands the application scope of biomass nanoparticles as multifunctional nanofillers.