A nanocomposite of a halogenated elastomer and an inorganic, exfoliated clay, suitable for use as an air barrier, is disclosed. The halogenated elastomer can be a polymer comprising C.sub.4 to C.sub.7 isoolefin derived units, para-methylstyrene derived units, and para(halomethylstyrene) derived units, or can be a butyl-type rubber. The nanocomposite can be formed by contacting an aqueous slurry of inorganic clay with a polymer cement while agitating vigorously to form emulsions or micro-emulsions to intimately mix the inorganic clay and the elastomer. The nanocomposite so formed has improved air barrier properties and is suitable for use as an innerliner or innertube.