Achieving clay dispersion and improving clay-polymer interactions are keys to producing superior nanocomposites. A supercritical CO2 (scCO(2)) Processing method was utilized to prepare high molecular weight polystyrene (PS)/Cloisite 10A nanocomposites with significant dispersion and theological enhancement. The effects Of scCO(2) processing, presence of cosolvent, and clay weight fraction on clay dispersion and polymer-clay interactions in nanocomposites were investigated. Rheology, WAXD, and TEM of the nanocomposites indicate that substantial improvements in the theological properties Of scCO(2) nanocomposites are the result of increased dispersion and polymer-clay interactions. At low frequencies, the elastic plateau modulus of the scCO(2)-processing nanocomposites (5 wt % clay loading) is more than 40-fold higher than benchmark solution-blended samples. Our results suggest that the substantial contacting with scCO(2), followed by rapid depressurization, produces a combination of disorder and dispersion of this "as-received" clay, and the presence of the cosolvent enables more intimate contact of the high molecular weight PS and clay.