Surface-Initiated Living Radical Polymerization from Narrowly Size-Distributed Silica Nanoparticles of Diameters Less Than 100 nm

Abstract

Surface-initiated atom transfer radical polymerizations (ATRP) from narrowly size-distributed silica nanoparticles (SiNPs) of diameters less than 100 nm were investigated. Two methods were used for the preparation of the SiNP cores: one was the reverse-micelle technique, which gave monodisperse SiNPs of average diameter 55 nm, and the other was the lysine-addition technique, which gave nearly monodisperse SiNPs of average diameter 15 nm. These nanoparticles were surface-modified with a triethoxysilane derivative containing an ATRP-initiating group. The surface-initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator-fixed SiNPs in the presence of a “sacrificial” free initiator. Well-defined poly(methyl methacrylate) (PMMA) brushes of a target molecular weight were successfully grafted with a surface density as high as 0.4−0.8 chains/nm 2 . These core−shell hybrid particles were highly dispersible, without any aggregation, in various solvents for PMMA. Because of the exceptionally high uniformity and perfect dispersibility, these hybrid particles formed two- and three-dimensional ordered arrays at the air−water interface and in suspension, respectively.