Nanocomposite layered materials prepared by co-intercalation of an onium ion, preferably an alkoxylated onium ion and an ethylene vinyl alcohol oligomer or polymer between the planar layers of a swellable layered material, such as a phyllosilicate, preferably a smectite clay. The spacing of adjacent layers of the layered materials is expanded at least about 3 Å, preferably at least about 5 Å, usually preferably to a d-spacing of about 15-20 Å, e.g., 18 Å with the alkoxylated onium ion spacing/coupling agent. The intercalation of the ethylene vinyl alcohol polymer then increases the spacing of adjacent layers an additional at least 2 Å, e.g., to at least about 20 Å, preferably about 25 Å to about 30 Å, generally about 28 Å. Improved O
barrier properties are observed over a broad range of humidity conditions when intercalation is accomplished by both the solvent route and the direct compounding route. The intercalated and exfoliated layered materials are useful for barrier layers in multi-layer packaging and for coatings.