High-refractive-index trialkoxysilane-capped PMMA−titania hybrid optical thin films were prepared by an in situ sol−gel process, followed by spin-coating and multistep baking. The acrylic monomers used were methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (MSMA). Titanium(IV) n-butoxide was used for the preparation of the titania network. By using catalyst-free polymerization and adjusting the solvent THF amount for polymerization, the titania content in the hybrid thin films can be as high as 70.7 wt %. The FTIR and DSC results indicate the successful bonding between the organic and inorganic moieties and the good dispersion of the PMMA segment in the titania network. The AFM study demonstrates that the prepared hybrid thin films have excellent planarization. The FE-SEM results suggest that the titania moieties in the prepared hybrid materials T10−T80 are on the nanosize scale. The dispersion of the refractive index and extinction coefficient in the wavelength range of 190−900 nm was ...