Hybrid nanoparticles with hyperbranched polymer shells via self-condensing atom transfer radical polymerization from silica surfaces

We present the synthesis of hyperbranched polymer-silica hybrid nanoparticles by self-condensing vinyl polymerization (SCVP) via atom transfer radical polymerization (ATRP) from silica surfaces. ATRP initiators were covalently linked to the surface of silica particles, followed by SCVP of an initiator-monomer (inimer) which has both a polymerizable acrylic group and an initiating group in the same molecule. Well-defined polymer chains were grown from the surface to yield hybrid nanoparticles comprised of silica cores and hyperbranched polymer shells having multifunctional bromoester end groups, as confirmed by elemental analyses and Fourier transform infrared measurements. Characterization of soluble polymers obtained in solution by gel permeation chromatography (GPC), GPC/viscosity, and NMR suggests the formation of highly branched polymers, Correlation of molecular parameters of the soluble polymers with the polymers grafted on the surface is discussed in view of theoretical considerations. Hydrolysis of the ester functionality of branched poly(tert-butyl acrylate), which was obtained by copolymerization of the inimer and tert-butyl acrylate, created branched poly(acrylic acid)-silica hybrid nanoparticles. The hybrid nanoparticles were characterized using transmission electron microscopy, field emission scanning electron microscopy, scanning force microscopy, and dynamic light scattering.