Photochromism of liquid crystalline dendrimer with azobenzene terminal groups in solution

The photochromism of a liquid crystalline dendrimer (LCD) with 36 hexyloxyazobenzene terminal groups in solution was described in this paper. The molar absorption coefficient, quantum yield, photoisomerization, photo back-isomerization, thermal back-isomerization and activation energy of LCD in solution are studied by UV/Vis absorption spectra. The results indicate that the photochromism, photo and thermal back-isomerization of LCD in chloroform (CHCl3) and tetrahydrofuran (THF) solutions are in accordance with the first order kinetics. The photochromism rate constants of LCD are 10−1 s−1, it is 107 times larger than that of side-chain liquid crystalline polymers (LCP) containing the same azobenzene moieties. These results indicate that the dendritic structure does not significantly affect the photoisomerization activity of the azobenzene unit in its periphery. The kt/kc of LCD is less than that of azobenzene unit shows that the LCD has better photo-reversibility. So the liquid crystalline dendrimer has potential applications.