Poly(L-lactic acid) (PLLA) is a biodegradable polymer that has attracted increasing attention due to its fantastic properties. Nevertheless, the disadvantages of PLLA, such as low crystallization rate and brittleness, limit its wide commercial applications. In the present work, electrospun stereocomplex PLA fibers (Sc-fibers) and PLLA grafted cellulose nanocrystals (g-CNCs) are prepared as nano-fillers and then blended with PLLA matrix to prepare different nanocomposites. Both of nano-fillers would accelerate the crystallization rate of PLLA, and as expected, g-CNCs have much stronger nucleation ability towards PLLA than Sc-fibers. Nevertheless, the crystallization of PLLA will decrease to some extent in the presence of both nano-fillers of g-CNCs and Scfibers due to the preferential formation of stereocomplex crystals on the surfaces of CNCs. Moreover, the presence of nano-fillers would enhance the mechanical properties of PLLA, such as the elongation at break can increase by four times after incorporating both g-CNCs and Sc-fibers. This work provides a new consideration for designing different nano-fillers, especially for polymer matrices with low crystallization ability and brittleness.

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