Nanoclays (NCs) impart highly effective barrier properties to polymers due to their platelet structure, provided that the NCs are exfoliated and form a parallel array relative to the product Surface. High barrier films with enhanced mechanical properties were developed and studied using blends of polyamide (PA) or ethylene vinyl alcohol (EVOH) with polyethylene (PE) and compatibilizing copolymer, and with incorporated NC. Permeability measurements indicated that by increasing the active polymers contcentration tip to 30%, however, reducing the barrier layer thickness comprising the active polymers (PA or EVOH), resulting ill reduction of the oxygeii transmission rate (OTR) by more than 7- to 8-folds. When NC was micorporated in the concentrated active polymer layer, the barrier to oxygen was further increased. This resulting in equal or even better barrier properties compared to the case where the active polymers are at 95% concentration. The increase in barrier properties was attributed to the laminar structure of the incompatible active polymer in addition to the orientation of the NC with its additional effects due to nucleation and enhancement of the amorphous phase barrier. The mechanical properties of the concentrated active layer (CAL) films were better or comparable with respect to the high barrier reference films. Furthermore, a micleatim effect, leading to increased crystallinity, was identified in the cases where PA compositions contained NC, whereas selective nucleation was obtained in the case where EVOH compositions contained NC. These observations, on oxygen barrier and mechanical properties, were further supported by the results obtained from thermal analysis (differential scanning calorimetry [DSC]), X-ray diffraction (XRD) measurements, and transmission electron microscopy (TEM) imaging studies carried Out On the hybrid films. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116:72-83,2010