Supercritical carbon dioxide-processed dispersed polystyrene-clay nanocomposites

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 scCO₂ 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 SCCO₂ nanocomposites are the result of increased dispersion and polymer-clay interactions. At low frequencies, the elastic plateau modulus of the scCO₂-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 scCO₂, 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.