Supercritical Carbon Dioxide-Processed Dispersed Polystyrene−Clay Nanocomposites

Achieving clay dispersion and improving clay−polymer interactions are keys to producing superior nanocomposites. A supercritical CO 2 (scCO 2 ) processing method was utilized to prepare high molecular weight polystyrene (PS)/Cloisite 10A nanocomposites with significant dispersion and rheological 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 rheological 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.