Grafting PMMA Brushes from α-Alumina Nanoparticles via SI-ATRP

Alumina nanoparticles are widely used as nano fillers for polymer nanocomposites. Among several different polymorphs of alumina, alpha-alumina has the most desirable combination of physical properties. Hence, the attachment of polymer chains to alpha-alumina to enhance compatibility in polymeric matrixes is an important goal. However, the chemical inertness and low concentration of surface hydroxyl groups have rendered polymer modification of alpha-alumina a long-standing challenge. Herein, we report that activation of a-alumina in concentrated or molten NaOH as well as in molten K2S2O7 increased polymer graft density up to 50%, thereby facilitating the synthesis of alpha-alumina brush particles with uniform grafting density of 0.05 nm(-2) that are readily miscible or dispersible in organic solvents or in chemically compatible polymeric hosts.