Epoxy-based hybrids using TiO₂ nanoparticles prepared via a non-hydrolytic sol-gel route

TiO₂ nanoparticles with an average diameter of less than 10 nm were prepared via a non-hydrolytic sol-gel route in a TiCl₄- diisopropyl ether-CH₂Cl₂ system. After modification with n-octylphosphonic acid (OPA) to increase their organophilic character, the TiO₂ nanoparticles were used for preparation of TiO₂/epoxy hybrid films. Characterization by FT-IR, solid-state ¹³C cross-polarization/magic angle spinning (CP/MAS) and ³¹P MAS NMR techniques showed the preservation of the n-octyl groups and the presence of TiOP bonds on the surface of TiO ₂ nanoparticles. Hybrid films with various TiO₂ contents were prepared via a wet process and casting using CH₂Cl₂ as a solvent. The resulting films were highly transparent. The refractive indices of TiO₂/epoxy hybrid films at 633 nm increased monotonously from 1.51 for the pure polymer to 1.66 for the hybrid containing 62.4 mass% of TiO₂ nanoparticles.