Effect of Conformations of Trans- and Cis-Azobenzenes on Photoinduced Anchoring Transitions in a Nematic Liquid Crystal

• Published in: Japanese Journal of Applied Physics Vol. 39; no. 2A; p. L104
• Main Authors: Ruslim, Christian, Komitov, Lachezar, Matsuzawa, Yoko, Ichimura, Kunihiro
• Format: Journal Article
• Language: English
• Published: 01.02.2000
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.39.L104

Two azobenzenes with different positional substituents, 3,3 ′ -dihexyloxy-2,2 ′ -dimethylazobenzene (3,3 ′ -azo) and 4,4 ′ -dihexyloxy azobenzene (4,4 ′ -azo), were doped onto a nematic liquid crystal (LC) to form photoresponsive guest-host LC mixtures. The photoinduced anchoring transition of the LC, triggered by trans-cis photoisomerization of the two dyes subjected to linearly polarized UV light was found to be different. Whereas the photoisomerization of 3,3 ′ -azo only induced a transition from random planar (RP) to uniform planar (UP) (in-plane) alignment, that of 4,4 ′ -azo additionally induced a transition from uniform planar to homeotropic (H) (out-of-plane) alignment of the LC at a longer exposure time. The anchoring behavior of the two azobenzenes is discussed in terms of the conformations of their trans - and cis -isomers and the interactions of the isomers with the solid surface of the substrate.