Title: ON BIAXIALITY OF PHOTOINDUCED STRUCTURES IN AZOPOLYMER FILMS
Author(s): A.Kiselev (Chernigiv Technological University, 95 Shevchenko Str., 14027 Chernigiv, Ukraine), O.Yaroshchuk, Yu.Zakrevskyy, A.Tereshchenko (Institute of Physics of the National Academy of Sciences of Ukraine, 46 Nauki Ave., 03028 Kyiv, Ukraine)

Spatial orientational structures in the layers of liquid crystalline polymalonates are investigated using UV absorption method and the results of the null ellipsometry technique. Preferential in-plane alignment of azobenzene fragments and in-plane reorientation under irradiation with polarized UV light are established. The components of the order parameter tensor of azobenzene fragments are estimated for the initial state and after different doses of irradiation. The uniaxial as well as biaxial order of the azobenzene chromophores are detected. The biaxiality is observed in the intermediate stages of irradiation, whereas the uniaxial order is realized in the saturated state. The proposed theory takes into account biaxiality of the induced structures and describes well the experimental dependencies of the order parameter components on the time of irradiation.

Key words: azopolymer, photo-induced anisotropy, spatial orientation
PACS: 61.30.Gd, 42.65.-k, 78.66.Qn