Nanocomposites with enhanced biodegradability and reduced oxygen permeability were fabricated via melt hybridization of organomodified clay and poly (lactic acid) (PLA) as well as a PLA/polycaprolactone (PCL) blend. The nanocomposite microstructure was engineered via interfacial compatibilization with maleated polypropylene (PP-g-MA). Effects of the compatibilizer structural parameters and feeding route on the dispersion state of the nanolayers and their partitioning between the PLA and PCL phases were evaluated with X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Although highly functionalized PP-g-MA with a low molecular weight was shown to be much more effective in the intercalation of PLA and the PLA/PCL blend into the clay gallery spaces, composite samples compatibilized by high-molecular-weight PP-g-MA with a lower degree of maleation exhibited lower oxygen permeability as well as a higher rate of biodegradation, which indicated the accelerating role of the dispersed nanolayers and their interfaces in the enzymatic degradation of PLA and PLA/PCL matrices. This evidenced a correlation between the nanocomposite structure and rate of biodegradation. The size of the PCL. droplets in the PLA matrix was reduced by nanoclay incorporation, and this revealed that the nanolayers were preferentially wetted by PCL in the blend. However, PCL appeared as fine and elongated particles in the microstructure of the PLA/PCL/organoclay hybrids compatibilized by higher molecular weight and less functionalized PP-MA. All the PLA/organoclay and PLA/PCL/orgnoclay hybrids compatibilized with high-molecular-weight PP-g-MA displayed a higher dynamic melt viscosity with more pseudo solid-like melt rheological responses, and this indicated the formation of a strong network structue by the dispersed clay layers.(c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1954-143, 2009