Poly(lactic acid) (PLA) chains are directly grafted onto a silicon surface by in situ amidation and PLA/PLA-grafted SiO2 nanocomposites are compounded using a Haake torque rheometer. To have a better understanding of the interaction between grafted polymer chains and PLA matrix, thermal, and rheological properties of PLA/PLA-grafted SiO2 nanocomposites are explored. DSC analysis shows that PLA-grafted-SiO2 can accelerate the cold crystallization rate and increase the degree of crystallinity of PLA. Shear rheology testing indicates that PLA/PLA-grafted-SiO2 nanocomposites still exhibits the typical homopolymer-like terminal behavior at low frequency range even at a content of PLA-grafted-SiO2 of 5 wt %, compared to PLA/SiO2, it is also found that the nanocomposites show stronger shear-thinning behaviors in the high frequency region after grafting. In addition, elongation viscosity testing shows the entanglement between grafted chains and matrix that is needed to improve the melt strength of PLA. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013