The present invention is a process to produce a nanocomposite of a elastomer and organic clay, e.g. an exfoliated clay, suitable for use as an air barrier. The process can include the steps of: (a) contacting a solution (10) of butyl rubber in an organic solvent with a halogen (12) to form a halogenated butyl rubber solution (16); (b) neutralizing the halogenated butyl rubber solution; (c) functionalizing at least a portion (18) of the halogenated butyl rubber; (d) mixing a dispersion (22) of clay with the functionalized butyl rubber (18) to form a masterbatch (26) comprising a polymer-clay nanocomposite; (e) combining the masterbatch (26) with the rest of the halogenated butyl rubber solution (20) to form a second mixture (28); (e) recovering the nanocomposite from the second mixture (28). The nanocomposite so formed has improved air barrier properties and is suitable for use as a tire innerliner or innertube.