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Photoinduced Molecular Re-orientation and Supramolecular Helical Structure Formation in Azobenzene Materials

ABSTRACT Photoinduced chirality in azobenzenes has been investigated. Even in low-molecular weight azobenzenes, photoinduced optical rotation could be observed and the characteristics were similar to that of ever reported in azobenzene side-chain-type polymer. Any relationship between molecular chirality and photoinduced chirality could not be observed in low-molecular weight azobenzenes. Further, very large optical rotation of 41 deg./μm could be observed in an azobenzene copolymer containing large birefringent unit. Dependence of optical rotation on intensity, wavelength and ellipticity of excitation beam were examined. The phenomenon was discussed based on the assumption that photoinduced helical structure was formed by elliptically polarized beam irradiation.