Synthesis and characterization of liquid crystalline azobenzene chromophores with fluorobenzene terminal

• Four novel fluorine-substituted azobenzene chromophores were synthesized and characterized.
• These rod-shaped molecules exhibit strong photoisomerization behaviour in solutions.
• The photo-switching properties of compounds shows trans to cis isomerization ranging 10–11 s, whereas reverse process take place around 125 min in solutions.
• Presented studies may lead to the creation of optical storage devices due to their impressive thermal back relaxation time.

Two series of fluorine-substituted benzoate ester type rod-shaped liquid crystals incorporating the azobenzene as side arm linked with terminal double bonds as polymerizable functional groups were synthesized and characterized by polarized-light optical microscopy (POM), differential scanning calorimetry (DSC) and UV–visible spectroscopy investigations. Thus, rod-shaped monomers, namely 4a and 4b having odd and even number of carbon in the terminal group exhibited nematic phase and SmA type phase was found at lower temperature. Compound 5 showed nematic phase whereas compound 6 showed SmA phase. These rod-shaped molecules exhibit strong photoisomerization behaviour in solution. The photoswitching properties of the compounds showed trans to cis isomerization in about 10 s, whereas the reverse process takes place about 120 min in solutions. Proposed materials may have potential to use it in optical storage devices.

Experimental investigations on the new fluorine-substituted azobenzene chromophores given fast switching from trans to cis about 10 s and reverse transformation around 7200 s which can be adopted for optical storage devices.Figure optionsDownload as PowerPoint slide