Photosensitive polymers bearing fully aromatic esters for multilayer data storage devices

The modulation of the refractive index in polymeric films by means of UV-light is of importance for modern optical applications such as wave guiding and optical data storage. In this contribution, we report on the synthesis of novel photoreactive polymers bearing fully aromatic esters which undergo the so-called photo-Fries rearrangement to aromatic hydroxy ketones. Poly(4-vinylphenyl benzoate) (poly-1) and poly(4-vinylphenyl 1-naphthoate) (poly-2) were prepared by a polymer analogous reaction using poly(4-vinylphenol) as starting compound and the corresponding aromatic carboxylic acid chlorides. The photo-Fries rearrangement in these polymeric materials results in a significant change in the refractive index by Δn600 = +0.036 for poly-1 and by Δn600 = +0.011 for poly-2. The additional change in chemical reactivity can be used for the immobilization of fluorescent dyes in the illuminated areas. In combination with photolithographic techniques, fluorescent patterns can be obtained. Due to the fact that both synthesized polymers exhibit different light absorption behaviours novel approaches of bitwise volumetric recording could be demonstrated. In a sandwich assembly of both polymer films it is possible to achieve a selective writing in each layer using UV-light of different wavelengths, without the demand of two-photon excitation.