Synthesis of core-shell poly (N-isopropylacrylamide) grafted silica nanoparticles by distillation precipitation polymerization

Poly(N-isopropylacrylamide) PNIPAAm is among the smart hydrogels widely used in novel drug delivery systems. In this work, silica/poly(N-isopropylacrylamide) (SiO2/PNIPAAm) core-shell hybrid nanoparticles were prepared by a two-step reaction, starting with acrylate modified silica nanoparticles (ASNPs) prepared by one-pot synthesis/modification method. The PNIPAAm was grafted onto ASNPs by distillation precipitation polymerization of N-isopropylacrylamide (NIPAAm) in acetonitrile and, in the presence of 2,2´-azobisisobutyronitrile (AIBN) as the initiator without using any stabilizer or surfactant. The core-shell particles were obtained with average diameter of about 90 nm still having the possibility to increase the thickness of PNIPAAm shell by successive polymerization reactions. The infrastructure, property and chemistry of the core-shell nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), thermal gravimetric analysis (TGA) in addition to surface characterization by water contact angle measurement.