Optimization of the photochromic response of photoaddressable polymers with azobenzene-containing molecular glasses

Abstract

This paper reports on a new series of photochromic azobenzene-containing molecular glasses which are investigated as blending materials to improve the photochromic response of photoaddressable polymers. In order to identify potential candidates for blending, a variety of molecular glasses are synthesized and screened with respect to their photochromic response. Various end groups at the azobenzene chromophore and different core compounds are employed to obtain high thermal stability and good glass-forming properties as well as high sensitivity and refractive-index modulation. The best combination of structural variations is chosen to tailor a photoaddressable material with optimized physical and photophysical properties. By doping this photochromic molecular glass former into a photoaddressable polymer we are able to combine the high stability of polymer systems with the faster response of molecular glasses, thus creating a system which has the advantages of both material classes. With this approach we achieve an increase of the low photochromic sensitivity of the polymer, which is the biggest problem of these materials. In order to obtain a better understanding of the influence of the photochromic molecular glass former on the photochromic response in a polymer system we conduct holographic experiments on a concentration series of the glass former in an inert polymer matrix. By inscribing the holographic gratings at elevated temperatures we are able to increase the sensitivity of our molecular glass further.