Core-Shell Silica/ Poly(Hydroxyethylmethacrylate) Nanoparticles Synthesized Via Distillation Precipitation Polymerization

Silica/poly(hydroxyethylmethacrylate) (SiO2/PHEMA) core-shell hybrid nanoparticles were prepared by a two-step reaction starting with vinyltriemethoxysilane (VTMS) or 3-(methacryloxy)propyltrimethoxysilane (MPS) grafted < 50 nm silica nano-particles as the core prepared through one-pot method. PHEMA, the shell, was then grafted onto VTMS- and MPS-modified silica cores by distillation precipitation polymerization of 2-hydroxyethylmethacrylate (HEMA) using 2,2′-azobisisobutyronitrile (AIBN) as the initiator in acetonitrile without any stabilizer or surfactant. The thickness of hydrogel layers could be conveniently controlled via precise adjusting conditions in successive polymerization steps. Here the polymerization repeated two times to increase the PHEMA thickness. Infrastructure, property and chemistry of the core-shell nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) in addition to water contact angle measurement. The results showed the successful vinyl and acrylate modified < 50 nm silica particles and further PHEMA grafting on them in two successive precipitation polymerization steps. The obtained core-shell SiO2/PHEMA nanoparticles could be used in any related application.