Synthesis and characterization of azo-polymers presenting optical anisotropy

R. FERNÁNDEZ; P.M. REMIRO; M.J.GALANTE; P.A.OYANGUREN; I. MONDRAGÓN

San Sebastián (España)

Workshop; Workshop Nanofun 2006; 2006

Inasmet y Grupo Materiales + Tecnologías de la Escuela Universitaria Politécnica de San Sebastián

Polymers containing azobenzene-type chromophores have received much attention in the past few decades because of potential applications in optical information storage, optical switching devices, diffractive optical elements and other areas. Photoinduced optical anisotropy in azo-polymer films is among the most interesting effects found. In most of the reported works, anisotropy has been induced by illumination with linearly polarised 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 polarisation direction of the exciting light, can be achived. As a result, the distribution of molecular orientation that was isotropic before photoexcitation becomes anisotropic. This anisotropic distribution gives rise to birefringence and dichroism in the azo-polymer film.           On the other hand, the large polarity in azobenzene molecules with electron donor and acceptor substituents (push-pull type) leads to materials with large second-order nonlinear optical susceptibilities.           Series of epoxy-based polymers functionalized with azobenzene chromophores have been designed and synthesized. The polymers synthesized were characterized by spectroscopic and optical methods. The growth and decay processes of the optically induced anisotropy have been studied as function of azobenzene compound concentration and environment in which azobenzene chromophore exists.