Bionanocomposites from biopolymers and inorganic nanoparticles are of great interest for packaging materials due to their enhanced physical, thermal, mechanical, and processing characteristics. In this study, poly(lactic acid) (PIA) nanocomposites with covalent bonding between TiO2 nanowire surface and PEA chains were synthesized through in situ melt polycondensation. Molecular weight, structure, morphology, and thermal properties were characterized. Fourier transform infrared spectroscopy confirmed that PIA chains were covalently grafted onto TiO2 nanowire surface. Transmission electron microscopy images also revealed clearly a third phase presence on the nanowires after the grafting process. Those grafted PIA chains exhibited significantly increased glass transition temperature and thermal stability, compared with pure PEA. The weight-average molecular weight of PEA/2% TiO2 nanowire bulk nanocomposites increased by 66% compared with that of pure PIA. The electron microscopy results showed that strong interfacial interaction and homogeneous distribution were achieved between inorganic nanowires and organic PIA matrix in the bulk nanocomposites. The PEA matrix in bulk nanocomposites exhibited elevated glass transition temperature and decreased crystallization ability as the TiO2 nanowire concentrations were increased from 0 to 2%. (C) 2011 Elsevier Ltd. All rights reserved.