High refractive-index thin films prepared from trialkoxysilane-capped poly(methyl methacrylate)-titania materials

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 studied. The off-resonant refractive indices of the prepared hybrid thin films T10-T90 at 633 nm were in the range of 1.505-1.867 as the titania content linearly increased from 2.9 to 70.7 wt %. However, the Abbe number exhibits the reverse trend. The shift of the absorption maximum of the prepared hybrid thin films can be correlated with the titania content. The prepared hybrid films show potential applications in optical devices, which exhibit very high optical transparence in the visible region.