Nanocomposites of poly(l-lactide) and surface-grafted TiO2 nanoparticles: Synthesis and characterization

A new method of surface modification of TiO2 nanoparticles by surface-grafting l-lactic acid oligomer was developed. The surface-grafting reaction was evaluated by Fourier transformation infrared (FTIR) and thermal gravimetric analysis (TGA). The results showed that l-lactic acid oligomer could be easily grafted onto the TiO2 nanoparticles surface in the presence of stannous octanoate and the highest amount of grafted polymer was about 8.5% in weight. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results showed that grafted TiO2 (g-TiO2) in chloroform or PLLA matrix approximated to uniform, while unmodified TiO2 nanoparticles tended to aggregate. The tensile strength of this material was greatly improved by the addition of g-TiO2 nanoparticles in poly(l-lactide) (PLLA) matrix. The tensile strength of the g-TiO2/PLLA nanocomposite containing 5 wt.% of g-TiO2 was 72 MPa, which was 23.1% higher than that of pure PLLA. Even though the incorporation of the TiO2 nanoparticles into PLLA led to the deterioration of its elongation at break, the g-TiO2/PLLA nanocomposite also exhibited better ductility than that of TiO2/PLLA nanocomposite.