Benzotriazole D–A–D isomeric dichroic dyes application to guest–host liquid crystal adjustable optical glasses

Dichroic dyes are favored in the field of smart windows by virtue of their excellent dimming properties. D–A–D dichroic dye molecules not only have good dichroic properties and photostability but also have good solubility in the host LC. In this study, we synthesized a series of D–A–D dichroic dye molecules with benzotriazole as an acceptor, discussed the effect of the symmetry of the methyl position on the parent nucleus on the dye properties, the optical properties of the dyes were modulated by introducing different electron donors at both ends of the mother nucleus. In addition, preparation of a guest/host mixture by dissolving guest dyes in the host LC and filling them into a LC cell, then the relationship between the dye structure and the dichroic properties of the devices was systematically investigated. The results showed that the absorption and emission spectra of the dyes with the methyl group in the symmetric position were red-shifted to different degrees, and the dichroic properties and photostability were better. Among which the UV–vis absorption wavelength and fluorescence emission wavelength of D44BNT-1 were the largest at 482 nm and 575 nm, respectively, and the dichroic properties of D5OBNT-1 was the best, with a dichroic ratio of 6.40. Meanwhile the color difference after 10 h of illumination had a small change, and the best photostability. These findings are of great significance for the development of new dichroic dyes.