One-Pot Synthesis of Hairy Nanoparticles by Emulsion ATRP

An efficient one-pot synthesis of hairy nanoparticles was developed by applying ATRP to a two-step sequential emulsion copolymerization. The first step was a microemulsion ATRP of methyl methacrylate (MMA) monomer and ethylene glycol dimethacrylate (EGDMA) cross-linker, leading to uniform nanogels with hydrodynamic diameter D-h = 31 nm, determined by dynamic light scattering measurement. Addition of a second monomer, n-butyl acrylate (nBA), to the microemulsion successfully converted the system into an emulsion polymerization, and linear PnBA arms grew from the retained initiating sites in the nanogels, forming hairy nanoparticles in situ. The use of an emulsion medium allowed the preparation of hairy nanoparticles with uniform size (coefficient of variation <0.3), and the particle size increased from D-h = 38 to 100 mn with the increasing nBA conversion. Based on the GPC analyses of the cleaved products of nanogel cores and hairy nanoparticles containing degradable disulfide cross-link, the number of grafted polymer chains per hairy nanoparticle was estimated to be N-hair similar to 2.3 x 10(3), corresponding to a maximum grafting density of 0.75 chains/nm(2) on the surface of nanogel. Direct visualization of the hairy nanoparticles by atomic force microscopy provided additional evidence for the successful synthesis of uniform-sized particles.