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 TiOP bonds on the surface of TiO2 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. Copyright © 2013 John Wiley & Sons, Ltd.