Effect of density fluctuating supercritical carbon dioxide on polymer interfaces

We investigated an effect of CO ₂ sorption on the compatibility of immiscible polystyrene (PS) and polybutadiene (PB) bilayers by using in situ neutron reflectivity. By labeling either polymer with deuterium, we found that the excess CO ₂ molecules were adsorbed to both top PS and bottom PB layers when the bilayers were exposed to CO ₂ at the narrow T and P regime near the critical point of pure CO ₂. Furthermore, we clarified that this excess sorption of CO ₂ molecules increased the interfacial width between the layers up to 100 Å even near room temperature, while the interfacial width without CO ₂ exposure has been reported to be at most 40 A even at the highest temperature (T ≅ 175°C).