ИСТИНА

The present contribution is devoted to the elaboration of a novel mechanism of photo-orientation of LC materials. It assumes that photo-orientation occurs via photochemically induced growth and diminishing of LC domains. This mechanism has recently been shown valid for photo-orientation of an azobenzene-containing LC polymer [1]. In the present paper the evidence is provided that the rearrangement of domain structure plays major role in photoinduced orientation of a number of azobenzene-containing substances, both polymer and low molecular weight. The domain rearrangement is visually observed by means of polarization optical microscopy. Light irradiation leads to diminishing of domains aligned parallel to the electric field vector of irradiating light, and the growth of perpendicularly aligned domains. The experimental observations are quantitatively analyzed in the framework of a statistical kinetic model developed in [1] to describe photo-orientation via the proposed mechanism. The influence of domain size distribution, irradiating light intensity and wavelength on the kinetics of photo-orientation is theoretically and experimentally investigated. The proposed mechanism quantitatively agrees with experimentally observed kinetics of photo-orientation. [1] A. V. Bogdanov, A. Kh. Vorobiev, J. Phys. Chem. B., 2013, 117, 13936. The authors acknowledge the financial support from RFBR (grants nos. 14-02-31882, 14-03-00323).