Photo-isomerizable derivatives of phenylethanediol and cinnamic acid: Useful compounds for single-layer R, G, and B cholesteric color filters

This article describes the synthesis of derivatives of (R)-phenylethanediol and cinnamic acid. These molecules are photo-isomerizable and contain two acrylate groups that can form densely cross-linked cholesteric polymer films. The Z-isomers formed by irradiation of the E-isomeric cinnamic acid derivatives exhibit a much lower helical twisting power than that of the E-isomers. In this way, the reflection wavelength of cholesteric layers made with these molecules can be increased by irradiation. After polymerization, the cholesteric films are thermally stable and hence these molecules are suitable for use in cholesteric color filters that find application in liquid-crystalline displays.