The present invention includes blends of a halogenated elastomer such as a butyl rubber or 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 exfoliating compound and clay, the entire blend forming a nanocomposite in one embodiment. The clay may or may not have undergone an additional exfoliating treatment prior to blending with the halogenated elastomer. 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.