Camphor and nopinone derivatives as new photosensitive chiral dopants

E-Z photoisomerizable chiral dopants are a class of materials that can be used to prepare birefringent optical components with patterned optical properties. Two new photoisomerizable chiral dopants have been synthesized and analysed. The materials were derived from nopinone and camphor. The properties of these compounds were compared with the properties of the methone derivative described in earlier publications. The E-isomers of the nopinone and camphor derivatives had helical twisting powers of 2.7 and 1.7 μm^-1, respectively. This is a factor of about 10 lower than the value obtained for the menthone derivative (-19 μm^-1). Due to the high absorption of the Z-isomers relative to the E-isomers of the nopinone and camphor derivatives, isomerization during 365 nm UV exposure proceeded to a much lesser extent than the isomerization of the menthone derivative. At shorter wavelengths, the absorption of the Z-isomer is much lower than that of the E-isomer and much higher degrees of conversion could be achieved.