R. Fernándeza, P. A. Oyangurenb, M. J. Galanteb, I. Mondragona
a'Materials + Technologies' Group. Dept. of Chemical & Environmental Engineering. Universidad País Vasco/Euskal Herriko Unibertsitatea, Pza. Europa 1, 20018 Donostia-San Sebastián, Spain.
bINTEMA Univ. Nac. de Mar del Plata-CONICET, JB Justo 4302 Mar del Plata, Argentina
Polymers containing azobenzene-type chromophores have received much attention because of their potential applications in optical information storage, optical switching devices, diffractive optical elements and other areas. In most of the reported works, anisotropy has been induced by illumination with linearly polarized 488 nm light from an Ar+ laser. Under this illumination, the orientation of azo units changes through trans-cis-trans isomerization processes. A preferential orientation of the trans molecules, with its axis perpendicular to the polarization direction of the exciting light, can be achived. As a result, the distribution of molecular orientation that was isotropic before photo-excitation becomes anisotropic. This anisotropic distribution gives rise to birefringence and dichroism in the azo-polymer film.
In this work series of epoxy-based polymers functionalized with azobenzene chromophores have been synthesized and characterized. The growth and decay processes of the optically induced anisotropy have been studied as function of the azobenzene compound concentration, the environment in which the azobenzene chromophore exists, the intensity of the Ar+ laser and the film thickness. The variation of UV-visible absorbances for light polarized perpendicular and parallel to the polarization direction of the exciting light has also been investigated.
This work is supported by a grant from University of the Basque Country and Nanotron project funded by the Basque Government.