Reversible photoinduced anisotropy of azoxybenzenes in nematic liquid crystal phase and in solid polymer solutionsa
Kinetic peculiarities of the induced phase transition "nematic-isotropic liquid" in the layers of ZhK-440D, based on a mixture of liquid crystal (LC) azoxybenzenes have been investigated. Different cases of the absorption of polarized or unpolarized radiation were realized. Spectral changes of ZhK-440D, as well as the influence of activating radiation wavelength (365 and 405 nm) on the change in the transmission of the LC cell (10 μm thick) with rubbed polymer layers as orientants have been measured. At the same time the kinetics of changes in the intensity of light scattering in the transparency region (λ = 632.8 nm) formed by the spatial anisotropy of the diffraction pattern in the cross section of the probe beam was measured. It was showed that the holograms recorded in layers of the solid molecular solutions of the ZhK-440D mixture (12 wt. %) in polymetyl metacrylate with the help of He-Cd laser (λ = 325 nm) were stored for a few hours, whereas in the pure ZhK-440D they disappeared in a few minutes.