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Abstract

The out-of-plane photoreorientation in azo dye modified polymer thin films was investigated by surface plasmon resonance spectroscopy (SPR) and optical waveguide spectroscopy (WS). A styrene copolymer with covalently linked azo dye derivatives was used in order to measure changes in the molecular orientation during irradiation with polarized visible light. The covalent linkage of the azo moiety to polymer chain is found to be efficient in the reorientation process due to the suppression of the rotational diffusion. The measurement by four kinds of optical arrangement in SPR and WS results in the determination of the three independent refractive index components. Using this powerful technique for the evaluation of photoreorientation processes in polymer thin films, especially orientation normal to the film, we found that azo molecules preferentially align with the direction normal to the film plane.