Synthesis and characterization of silica-polyvinyl imidazole core-shell nanoparticles via combination of RAFT polymerization and grafting-to method

The silica-polyvinyl imidazole core-shell nanoparticles (silica/PVI NPs) with controlled shell thickness and narrow distribution size were fabricated via grafting-to method. First, O-ethyl xanthate terminated PVI with various chain lengths was produced via the reversible addition-fragmentation chain transfer (RAFT) polymerization using O-ethyl-S-phenyl dithiocarbonate (EPDC) as RAFT agent. Next, three synthesized PVI of different molecular weights (3.4, 6.6, and 11kg/mol) were successfully grafted to the methacrylate modified silica NPs from solution by radical mediated grafting-to method. These core-shell NPs were then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrum measurements (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). Polyvinyl imidazole molecular weight, reaction time, polymer concentration, and reaction temperature were all used to control the grafting reaction for PVI grafting densities and shell thicknesses. The highest grafting density obtained was close to 1.2 chains/nm(2) and was achieved for 3.4kg/mol PVI at 80 degrees C. The prepared silica/PVINP displayed efficient antifouling properties and stability in concentrated sodium chloride aqueous solutions over a broad pH range for a period of at least 7days. Copyright (c) 2017 John Wiley & Sons, Ltd.