Synthesis and characterization of stimuli-responsive poly(acrylic acid) grafted silica nanoparticles

Silica-poly(acrylic acid) (PAAc) core-shell nanoparticles (NPs) were successfully prepared via graft copolymerization of acrylic acid (AAc) onto vinyl-bond-modified silica NPs. Transmission electron microscopy (TEM) results indicated that the obtained micropheres have a core-shell morphology. Fourier transform infrared (FTIR) analysis and x-ray photoelectron spectroscopy (XPS) measurements confirmed that the surface of the nanoparticles was polymer-rich, consistent with the core-shell morphology. The influence of the synthetic conditions, such as reaction time and AAc concentration on the graft yield of PAAc grafted on the silica NPs was investigated. Dynamic light scattering (DLS) analysis showed that the silica-PAAc core-shell nanoparticles possessed excellent response to pH and ion strength. Because of their pH-responsive behavior and small feature size, nanostructure devices designed from the smart silica nanoparticles have potential applications including sensors and membranes.