In this study, new biodegradable nanocomposites were prepared from poly(lactic acid) (PLA) or acrylic acid grafted poly(lactic acid) (PLA-g-AA), titanium tetraisopropylate, and starch by means of an in situ sol-gel process and the melt-blending method. The samples were characterized with X-ray diffractometry, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and an Instron mechanical tester. According to the results, a PLA-g-AA/TiO2 hybrid could improve the properties of a PLA/TiO2 hybrid because the carboxylic acid groups of acrylic acid should act as coordination sites for the titania phase to form the Ti-O-C chemical bond. It was also found that both the tensile strength and glass-transition temperature increased to a maximum. value and then decreased with increasing TiO2 because excess particles (e.g., greater than 10 wt % TiO2) could cause separation or segregation between the organic and inorganic phases. A PLA-g-AA/TiO2/starch hybrid could obviously enhance the mechanical properties of a PLA-g-AA/starch hybrid because the former could provide a smaller starch phase size and nanoscale dispersion of TiO2 in the polymer matrix. The biodegradable nanocomposites produced in our laboratory could provide a plateau tensile strength at break when the starch content was up to 50 wt %. (C) 2008 Wiley Periodicals, Inc.