A novel method of surface-initiate atom transfer radical polymerization of styrene from silica nanoparticles for preparation of monodispersed core-shell hybrid nanospheres

A new kind of initiator, 3-(2-bromo-2-methylacryloxy)propyltriethysiliane (MPTS-Br), was prepared with a simply hydrobrominated commercial silane coupling agent (3-methacryloxy-proplytriethysilane, MPTS). It has been one-step self-assemble onto the surface of silica nanoparticles, and by using this initiator-modified nanoparticle (SiO₂-MPTS-Br) as macroinitiator for atom transfer radical polymerization (ATRP). Structurally well-defined homopolymer polystyrene (PS) and block polymer poly(styrene-b-methyl methacrylate) (PS-b-PMMA) chains were grown from the nanoparticles surface to yield individual particles composed of silica core and thick-coated polymer shell. The graft parameters could be calculated from the elemental analysis (EA) results, and linear plots of percentage of grafting (PG%) and conversion of monomer (C%) versus polymerizing time were achieved, respectively. Narrow molecular weight distribution (M_w/M_n) for the graft polymer samples were characterized by the gel permeation chromatography (GPC). The graft polymerizations exhibited the characteristics of the controlled/“living” polymerization. The glass transition temperature (T_g) of SiO₂-g-PS after polymerizing time of 24 h was found about 133 °C which was different from the polymer not grafted on the silica at 102 °C by the differential scanning calorimetry (DSC) analysis. The products were also characterized by FT-IR, XPS and TEM. The robustness and simplicity of this method may make large-scale manufacture of these polymer-coated nanospheres possible.