Fabrication of doubly responsive polymer functionalized silica nanoparticles via a simple thiol-ene click chemistry

Temperature and pH responsive silica nanoparticles were easily prepared by a simple thiol-ene click chemistry. Well-defined poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) and poly(N-isopropylacrylamide) (PNIPAAm) were first synthesized by a reversible addition-fragmentation chain transfer (RAFT) process. The polymers were then reduced to generate a thiol group at the chain end to react with vinyl groups on the surface of silica nanoparticles via a simple 'click' reaction. The ratio of the PDEAEMA and PNIPAAm segments on the silica nanoparticles surface was controlled by adjusting the feed weight ratios of the polymers in the reaction solution. The surface coated silica nanoparticles were characterized by a range of techniques such as thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The functionalized silica nanoparticles showed both pH and temperature responsive behavior and the solution properties were dependent on the ratio of the two polymers on the surface.