Photoisomerizable chiral compounds derived from isosorbide and cinnamic acid

The syntheses of derivatives of isosorbide and cinnamic acid are described. These chiral compounds are photoisomerizable. The Z-isomers could also be obtained after irradiation of these E-isomeric cinnamic derivatives. The Z-isomers were found to have a much lower helical twisting power than the E-isomers. These compounds are very suitable for use in cholesteric colour filters for liquid crystal displays. This was investigated by functionalizing the E-isomeric derivatives with two acrylate groups. The reflection wavelength of cholesteric layers made with these diacrylates can be tuned by means of UV irradiation because the pitch of the cholesteric layer increases on isomerization to the Z-isomer. Subsequent photopolymerization results in cholesteric films with excellent thermal stability.