Photoinduced condensation of sol-gel hybrid glass films doped with benzildimethylketal

Sol-gel hybrid glass films doped with benzildimethylketal (BDK) were prepared from [(methacryloxy)propyl]trimethoxysilane, methacrylic acid, and zirconium n-propoxide. Polymerization of methacryl groups and polycondensation of alkoxides by UV illumination and baking were observed using Fourier-transformed infrared spectroscopy. Polymerization kinetics and refractive index increase depend on UV illumination time. The refractive index increase is sensitive to BDK concentration and agrees well with photodecomposition of BDK. Thus, it is found that the refractive index increase is made by incorporation of the radicals produced by photodecomposition of BDK in the network as well as polymerization of methacryl groups.