Controlled post-synthesis grafting of thermoresponsive poly(N-isopropylacrylamide) on mesoporous silica nanoparticles

Ordered mesoporous silica nanoparticles with pore diameter of 5 nm were synthesized by modification of the sol-gel synthesis method. Post-synthesis two-step grafting of thermoresponsive poly(N-isopropylacrylamide) inside the mesopores of the nanoparticles was carried out by distillation precipitation polymerization of the methacryloxy-functionalized mesoporous nanoparticles with N-isopropylacrylamide monomer. A precise control on the quantity of the grafted polymer was achieved by changing the ratio of monomer to methacryloxy–functionalized nanoparticles. The polymer-grafted hybrid nanoparticles obtained were fully characterized by infrared spectroscopy, X-ray diffraction, dynamic light scattering, transmission electron microscopy, thermal and gas-volumetric analyses, which clearly showed presence and thermoresponsive behavior of the polymer inside the mesopores with the preservation of the characteristic mesoporous structure of the nanoparticles.