Reversible Reflection Color‐Control in Smectic Liquid Crystal Switched by Photo‐Isomerization of Azobenzene

Abstract

Through the looking glass: A reflection color transition is demonstrated in a smectic liquid crystal doped with a photochromic azobenzene and a chiral agent with high helical twisting power. The reflection color can be switched reversibly due to the isomerization of azobenzene upon UV/visible irradiation.

Photoresponsive Cholesteric Liquid Crystals

“…The phase transitions starting from the smectic phase were also observed in several doped systems [57][58][59][60]. The smectic LC host 8CB, doped with chiral molecules and azobenzene compounds, showed the phase transition from smectic to cholesteric due to the photo-induced isomerization of azobenzene molecules, and the prolonged irradiation drove the phase transition further to the isotropic phase.…”

A Photosensitive Liquid Crystal Studied by 14N NMR, 2H NMR, and DFT Calculations

“…This can be built by computing the chemical shielding s ref of the reference. [64,65] In particular, 14 N chemical shifts were determined by using NH 4 Cl as internal reference (s ref = À337.8 ppm), whose nuclear tensors were calculated at the same level of theory as the 1AB molecule.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] For instance, the formation of organized structures, such as ordered mesophases typical of liquid crystals, can be triggered by illumination with UV/Vis light. [1][2][3][4][5] Moreover, the photoresponse can be combined with other macroscopic properties, that is, optical ones observed in liquid crystals and/or mechanical ones in elastomers [1,2,[6][7][8] and polymers [9][10][11] containing photosensitive moieties. As shown by the increasing number of papers on the topic, great efforts are also put into the understanding of the molecular processes related to cis-trans isomerisation and trans-cis back isomerisation, [11] which bear a strong potential for technological applications.…”

Photocontrolled Phase Transitions and Reflection Behaviors of Smectic Liquid Crystals by a Chiral Azobenzene

“…A reversible reflection color-control in the LC cell LC-A-B 3 with 5 wt % DBN switched by the photoisomerization of azobenzene was realized. [42] Initially, a vibrant yellow reflection was observed before UV irradiation, and then the reflection color could be tuned from yellow to green and then to clear upon UV irradiation, whereas a reversible tuning was achieved upon visible irradiation (see the Supporting Information). The reflection color-control in smectic LCs by the photoisomerization of azobenzene may provide a new strategy for a full-color addressable pixel, potentially useful in future-generation LC displays.…”

“…[41] In a recent communication, we reported briefly the reflection wavelength tuning through the visible region in a chiral-azobenzenedoped smectic LC. [42] Herein, we systematically investigate the photoresponsive behaviors of the smectic LC, 4-octyl-4'-cyanobiphenyl (8CB), controlled by a chiral azobenzene chromophore in the absence and presence of different chiral compounds. The effect of azobenzene photoisomerization with different concentrations of the chiral compounds on the phase transitions and reflection behaviors of the smectic LC is comprehensively explored.…”