Stereocomplexed PLA nanocomposites: from in situ polymerization to materials properties The main issue about PLA however concerns its low crystallization ability/degree, significantly hampering its industrial implementation particularly in long-lasting applications like automotive, electronics and food packaging. Nevertheless, from the ecofriendly point of view, biodegradable polylactide (PLA) is considered as one of the best biobased polymers for many applications. In this work, we attempt to synergistically combine two of the main strategies often used to overcome the drawback of the PLA, namely adding nanofillers such as nanoclays and PLA stereocomplexation in order to enhance the thermal, mechanical and gas-barrier properties of polyester matrix. To improve the dispersion of nanoclays, the “grafting from” approach was employed via metal-free ring-opening and in situ intercalative polymerization of L-lactide and D-lactide from the surface of an hydroxyl-functionalized organomodified montmorrilonite, i.e., the commercially available Cloisite 30B. These nanohybrids were subsequently melt-blended with commercial PLA, in order to obtain stereocomplexed (or not) PLA-based nanocomposites, upon the stereochemistry. Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Thermal Analysis (DMTA) were carried out to assess the thermo-mechanical performances of the nanocomposites. The morphology and dispersion of the resulting materials were examined by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Moreover, their oxygen-barrier properties were also evaluated. Stereocomplexes, obtained by direct melt-blending PLA and the D-isomer based nanohybrid, presents a melting temperature above 40 °C than that of commercial PLA. The nanocomposites obtained show a significant improvement in mechanical and oxygen-barrier properties. All the results indicate a synergical effect provided by organomodified nanoclays and stereocomplexation. In addition, the “grafting from” approach enables to design fully stereocomplexed materials in the absence of any solvent that has been reported only in very few cases.