Synthesis of well-defined structurally silica–nonlinear polymer core–shell nanoparticles via the surface-initiated atom transfer radical polymerization

We report on the synthesis of the well-defined structurally silica–nonlinear polymer core–shell nanoparticles via the surface-initiated atom transfer radical polymerization. At first, 3-(2-bromoisobutyramido)propyl(triethoxy)-silane (the ATRP initiator) was prepared by the reaction of 3-aminopropyltriethoxysilane with 2-bromoisobutyryl bromide. The ATRP initiator was covalently attached onto the nanosilica surface. The subsequent ATRP of HEMA from the initiator-attached SiO2 surface was carried out in order to afforded functional nanoparticles bearing a hydroxyl moiety at the chain end, SiO2-g-PHEMA-Br. The esterification reaction of pendent hydroxyl moieties of PHEMA segment with 2-bromoisobutyryl bromide afforded the SiO2-based multifunctional initiator, SiO2-g-PHEMA(-Br)-Br, bearing one bromine moiety on each monomer repeating unit within the PHEMA segment. Finally, the synthesis of SiO2-g-PHEMA(-g-PSt)-b-PSt was accomplished by the ATRP of St monomer using SiO2-g-PHEMA(-Br)-Br as multifunctional initiator. These organic/inorganic hybrid materials have been extensively characterized by FT-IR, XPS, TG, and TEM.