Different organophilic layered silicates and a modified hydrotalcite were used as functional nanofillers for thermoplastic and thermosetting polymers. Polyamide 6 (PA6) and poly(butylene terephthalate) silicate nanocomposites were prepared by melt compounding using a twin-screw extruder. The morphology of the materials was investigated by transmission electron microscopy and small-angle X-ray scattering, and was found to be characterized by homogeneous dispersion of high aspect ratio silicate layers in the polymer matrix. The PA6 nanocomposite displayed excellent thermo-mechanical properties at low filler loadings and improved barrier properties. Epoxy nanocomposites have also been prepared and characterized with regard to their morphology and their water vapor permeability.