Synthesis and characterization of trialkoxysilane-capped poly(methyl methacrylate)-titania hybrid optical thin films

A series of trialkoxysilane-capped PMMA-titania hybrid optical thin films has been prepared by an in situ sol-gel process combined with spin coating and multi-step baking. The used acrylic monomers were methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (MSMA). Titanium(IV) n-butoxide was used for the preparation of the titania network. FTIR results indicate successful bonding between the organic and inorganic moieties. A DSC study suggests a good dispersion of the PMMA segment in the titania network while an AFM study suggests that the prepared hybrid thin films have superior smoothness in comparison to the parent titania thin film. The dispersion of the refractive index and extinction coefficient in the wavelength range 190-900 nm was studied. Variation of the titania content not only tunes the refractive index but also the position of absorption maximum. Off-resonant refractive indices of the prepared hybrid thin films were in the range 1.505-1.553, which linearly increased with the titania content. Furthermore, the hybrid polymer films have abbe numbers (nu) all > 30. The shift of the absorption maximum of the prepared hybrid thin films can be correlated with the titania content. The prepared hybrid films show very high optical transparency in the visible region. These results suggest that such hybrid films have potential applications for optical devices.