Directed Synthesis of Silica Nanoparticles on Micropatterned Hydrogel Templates Tethered with Poly(ethyleneimine)

Abstract

Poly(ethyleneimine) (PEI) was covalently grafted to hydrogel films of poly(2-hydroxyethyl methacrylate-co-acrylic acid) (PHEMA-co-PAA) to direct the growth of silica nanoparticles from a sol−gel reaction at room temperature and pH 5. The deposition was found to be site-specific, and the thickness and morphology of the SiO2 nanoparticles was controlled by PEI molecular weight and exposure time to Si(OH)4. Our results suggest that PEI attacked the ethyl ester groups on PHEMA, resulting in complete penetration of PEI chains and deposition of silica nanoparticles throughout the film. After pyrolysis at 500 °C, a faithful SiO2 replica of the patterned polymer template was obtained. We believe that the synthetic route described here can be extended to the synthesis and patterning of a wide range of inorganic oxides, including TiO2, ZnO, and V2O5 with controlled hierarchical organization.