In this study, very small (2–5 nm) TiO2 nanoparticles were synthesized in an aprotic solvent, N,N-dimethylacetamide, via hydrolysis and condensation of titanium alkoxide at room temperature. The synthesized TiO2 sol showed 30 days of storage stability and could be used to prepare high-refractive-index TiO2-polyimide hybrid thin films by an ex-situ method that involved a spin coating and multistep baking process. The field emission scanning electron microscope image showed a flat and uniform morphology of the hybrid thin film. TiO2 domains were in the nanometer range, thus avoiding light scattering. The refractive index at 633 nm of the hybrid thin film reached 2.05, which suggested potential applications of the film to anti-reflective coatings and optical waveguides.
Journal of Sol-Gel Science and Technology 71(1), pp.129-135