Photosensitive Bent-Core Liquid Crystals with Laterally Substituted Azobenzene Unit

Abstract

Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables fast (E)-to-(Z)-isomerization upon irradiation with UV-light and visible light, while the substitution facilitates the high stability of the photochemically formed (Z)-isomer. The effectiveness of the irradiation and the composition of photostationary states was determined by UV/Vis and 1H NMR spectroscopy. A nematic phase formed by the materials was characterized by differential scanning calorimetry and optical polarizing microscopy. We show that the materials easily change their relative configuration of the N=N double bond not only in solution, but also in the mesophase, which leads to fast isothermal phase transition from the nematic phase to isotropic liquid.

Transition from lamellar to nanostructure mesophases in azobenzene-based hockey-stick polycatenars

“…33 One class of photo switching LCs are azobenzene-based BCLCs, being interesting as a result of their fast photoisomerization. 34–41 One of the most promising bent core units is 4-cyanoresorcinol with low bend angle < 120°, and therefore induces LC phases at the cross-over between rod-like (calamitic) and bent-core molecules. 42–50…”

Photoswitching studies of new photochromic ionic liquids studied in real time by in situ irradiation

“…Molecular photoswitches have been successfully utilized as a powerful tool for developing new photoresponsive materials that have been used in several fields of chemistry, physics, and biology. Examples of these molecular devices are the multi-responsive drug release of azobenzene, 11 photosensitive liquid crystals, 12,13 photoresponsive block copolymers, 14 light-sensitive proteins for neuronal and cellular studies, 15–17 control of cellular mitosis, 18 photoisomerization-induced destabilization of b-DNA, 19 molecular information processing like molecular gates, 20,21 and more complex devices like adders/subtractors and 22,23 encoders/decoders. 24,25 Usually azobenzene derivatives are covalently attached to an ionic liquid to modify their molecular properties and their potential applications.…”