Fabrication of monolithic refractive optical lenses with organic-inorganic nanocomposites : relations between composition and mechanical and optical properties

Abstract

Sol-gel derived organic-inorganic hybrid materials and their potential for the production of refractive optical elements are presented. The main components of the investigated compositions are precondensed silanes with polymerizable double bonds (e.g. methacryloxypropyltrimethoxysilane (MPTS)) and co-condensates thereof. Dimethacrylates like tetraethyleneglycoldimethacrylate (TEGDMA) were employed as organic monomers. Molar ratios of silanes to organic monomers between 10:90 and 90:10 were investigated. Nanoscaled titania was incorporated in the homogeneous mixture of silanes and organic monomers. The combination of different molecular hybrid matrices and inorganic nanoparticles allows the adjustment of material properties, for example: impact strength between 2 and 15 kJ/m2, Youngs moduli between 0.8 and 3.7 GPa and universal hardness in the range from 40 to 170 N/mm2. Phase separation could be kept in the nanometer range to minimize optical losses due to scattering effects. Depending on composition, ne could be varied between 1.50 and 1.54, whereby the corresponding Abbe numbers ranged from 57 to 45. Ophthalmic lenses were prepared in less than 10 hours by simple mould techniques and by applying a combination of photochemical and thermal curing processes.