Optothermal Switching of Cholesteric Liquid Crystals: A Study of Azobenzene Derivatives and Laser Wavelengths

• Main Authors: Tai-Chieh Huang, Yen-Yu Chen, Chih-Chien Chu, Vincent K. S. Hsiao
• Format: Article
• Language: English
• Published: MDPI AG 2015-09-01
• Series: Materials
• Subjects: optothermal; azobenzene; anthraquinone dye; cholesteric liquid crystal
• Online Access: http://www.mdpi.com/1996-1944/8/9/5293

The laser-initiated thermal (optothermal) switching of cholesteric liquid crystals (CLCs) is characterized by using different azobenzene (Azo) derivatives and laser wavelengths. Under 405-nm laser irradiation, Azo-doped CLCs undergo phase transition from cholesteric to isotropic. No cis-to-trans photoisomerization occurs when the 405-nm laser irradiation is blocked because only a single laser is used. The fast response of Azo-doped CLCs under the on–off switching of the 405-nm laser occurs because of the optothermal effect of the system. The 660-nm laser, which cannot be used as irradiation to generate the trans–cis photoisomerization of Azo, is used in Anthraquinone (AQ)-Azo-doped CLCs to examine the optothermal effect of doped Azo. The results show that the LC-like Azo derivative bearing two methyl groups ortho to the Azo moiety (A4) can greatly lower the clearing temperature and generate large amount of heat in AQ-A4-doped CLCs.