Photochemical behaviours of star-like liquid crystal with azobenzene terminal groups

The photochemical behaviours of a new star-like liquid crystal S6 with four hexyloxyazobenzene terminal groups were described in this paper. The molar absorption coefficient, quantum yield, photoisomerization, photo back-isomerization, thermal back-isomerization and activation energy of S6 in solution are studied by UV/Vis absorption spectra. The results indicate that the photochromism, photo and thermal back-isomerization of S6 in chloroform (CHCl3) and tetrahydrofuran (THF) solutions are in accordance with the first order kinetics. The photochromism rate constants of S6 are 10−1 s−1, it is 107 times larger than that of side-chain liquid crystalline polymers containing the same azobenzene moieties. These results indicate that the star structure does not significantly affect the photoisomerization activity of the azobenzene unit in its periphery. The kt/kc of S6 is less than that of azobenzene unit shows that the S6 has better photo-reversibility. So the star-like liquid crystal has many potential applications. C 2005 Springer Science + Business Media, Inc.