The present invention is a blend of a thermoplastic engineering resin and an interpolymer of, on one embodiment, a C.sub.4 to C.sub.7 isomonoolefin, a para-methylstyrene and a para-(halomethylstyrene), the interpolymer having been pre-mixed with an exfoliated-clay, the entire blend forming a nanocomposite. The resin may or may not have a clay present prior to blending with the interpolymer. The interpolymer/clay mixture forms a distinct phase in the nanocomposite blend of the invention. The blend of the invention has improved air barrier properties and is suitable as an air barrier.