Photoinduced refractive index changes of 3-phenyl-coumarin containing polymers for ophthalmic applications

A novel photorefractive polymer has been developed where 3-phenyl-coumarin (3PC) is attached via alkyl spacers to a methacrylate backbone. The 3PC is a fusion of the structural motives of coumarin and stilbene. In 3PC the E/Z-isomerization, known from stilbenes, is blocked and a more extended conjugated π-electron system than in coumarin is obtained. A methacrylate based polymeric material comprising 3PC in the side chain has been synthesized and its photorefractive properties have been studied. The initial refractive index is image = 1.613 and the maximal light-induced change of the refractive index was found to be Δn633 = −0.045 in spin-coated thin films as well as in bulk material. The glass transition temperature of about 37 °C and the high lightfastness of the polymer make it a candidate material for intraocular lenses with photo-tunable refractive index properties.