Design of High-Density Helical Polymer Brush on Silica Nanoparticles for the Size Recognition of Fullerene Molecules

High-density syndiotactic poly(methyl methacrylate) (st-PMMA) brushes form a helical structure and encapsulate fullerene molecules in their helical cavities, leading to a PMMA brush/fullerene inclusion complex. The brushes recognize the size of guest molecules and spontaneously adapt their helical diameter to the guest molecules. Both polymer brush/C₆₀ and polymer brush/C₇₀ inclusion complex on the flat substrate were characterized on the basis of grazing incidence wide-angle X-ray diffraction (GIWAXD) measurements, and it is revealed that the main chains oriented perpendicular to the substrate. Moreover, high-density st-PMMA brushes grafted onto nanoparticles efficiently separate C₇₀ molecules from the mixture of C₆₀ and C₇₀ solution. Even after 5× repeating process, the selectivity for C₇₀ molecules remains at 99%.