Photoresponsive behaviors of smectic liquid crystals tuned by an azobenzene chromophore

Abstract

The photoresponsive behaviors of a smectic liquid crystal, 8CB, tuned by an azobenzene chromophore have been systematically investigated. For the smectic 8CB doped with the azobenzene chromophore, 4-n-hexyl-4′-(1-bromopropyloxy)azobenzene (AB), the smectic phase could be switched to nematic and then to isotropic phase induced by the trans-to-cisphotoisomerization of AB upon UV irradiation. For the smectic 8CB doped with AB and the chiral molecule, (S)-(−)-1, 1′-binaphthyl-2, 2′-diol (BD), the smectic phase could be switched to the cholesteric phase and then to the isotropic phase. The initial phase could be recovered when the cis isomer changed to the trans isomer upon visible irradiation. The switching of the position of reflection band of the liquid crystal mixtures could be also realized by photoisomerization. The photoresponsive behaviors are dependent on the composition ratios and the temperature performed in the study.