Synthesis, liquid crystal characterization and photo-switching studies on fluorine substituted azobenzene based esters

Abstract

A series of fluorinated azobenzene esters have been synthesized and studied by polarized optical microscopy (POM) and UV-Vis spectrophotometry. The –CO₂C₂H₅ group with monofluoro-substituted azobenzene exhibited nematic and smectic phases whereas difluoro-substituted azobenzene showed only the nematic phase. The addition of the electronegative fluorine atom plays an important role in photoisomerization of the azobenzene molecules. The monofluoro-substituted azobenzene gave strong photoisomerization in solution as compared with its diflouro counterparts. In these systems, trans–cis isomerization occurred after 4 minutes and cis–trans isomerization occurred after 22 hours which is much longer than expected for fluorine-substituted azobenzene systems. The presented results might have an influence on creating optical data storage devices.