Photocontrol of Birefringence and In-Plane Molecular Orientation in Copolymer Liquid Crystal Films with 4-Methoxyazobenzene and Photo-Cross-Linkable Side Groups

✍ Scribed by Nobuhiro Kawatsuki; Emi Uchida; Tohei Yamamoto

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 139 KB
• Volume: 204
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200390025

✦ Synopsis

Abstract

Control of the in‐plane orientation direction in a polymethacrylate copolymer liquid crystal film substituted with 4‐methoxyazobenzene (4MAz) and 4‐methoxycinnamoyloxybiphenyl (4MCB) side groups, and control of the reversible birefringence of the resultant oriented film are described. High‐order in‐plane molecular orientation was generated by irradiating with linearly polarized (LP) 365 nm light and subsequent annealing. By adjusting the exposure dose, the reorientation direction was controlled parallel and perpendicular to the electric vector (E) of the LP light. Cooperative reversion of the orientation direction for both the 4MAz and 4MCB groups was observed, and the orientational order, S, varied from −0.79 to +0.75, without the side groups aggregating. The degree of the photoreaction and the distribution of the photoproducts from the 4MAz and 4MCB side groups through the axis‐selective photoreaction explain the reversion of the orientation direction. Optical recording, erasing, and birefringent control of the resultant oriented films were demonstrated by employing the photoisomerization of the 4MAz side groups using nonpolarised (NP) 405 nm light.

Order parameters of a P1 film after irradiating with LP 365 nm light (circles) and that following subsequent annealing (squares), as a function of exposure energy.

imageOrder parameters of a P1 film after irradiating with LP 365 nm light (circles) and that following subsequent annealing (squares), as a function of exposure energy.