Preparation and rheology of supercritical CO$_{2}$-based dispersed polymer-clay nanocomposites

Effective dispersion of the fillers in a polymer matrix has been a key challenge in the field of nanocomposites. Supercritical carbon dioxide (scCO$_{2})$ appears , PS/clay, The nanocomposites are characterized using WAXD, SEM, TEM, Rheology and DSC. The high degree of dispersion achieved through sc-CO$_{2}$ appears to result in an order of magnitude increase in the rheological properties of PS, associated with an increase in the T$_{g}$ of around 13\r{ }C, at 10{\%} clay loading. These moduli improvements are significant better than those obtained with conventional, chemically-modified intercalated clay nanocomposites. The degree of enhancement in the properties appears to be strongly dependant on the polymer-clay interactions, and how it is promoted by the supercritical fluid. In the case of PDMS nanocomposites, where the clay-polymer interactions were weak, the modulus increase at low frequencies (for sc-CO$_{2}$ processed system) was only a factor of 2. In the case of PVME- I30P clay nanocomposites, the modulus increase was substantial even at moderate loadings and dispersions, perhaps to be hydrogen-bonding interactions. Our results indicate that scCO2 can not only disperse nanoclays in polymers, it can also significantly enhance clay-polymer interactions.