Impact of terminal group on azobenzene liquid crystal dimers for photo-responsive optical storage devices

Three new series of photo responsive dimers bearing different terminal functional groups (-CN, -COOEt, -OMe) and variable aliphatic spacers have been synthesized and investigated in detail. The molecular structures of the new materials were proved using different spectroscopic techniques and their liquid crystal self-assembly was characterized using differential scanning calorimetry (DSC), polarized light microscope (POM) and X-ray diffraction (XRD). Moreover, their photo switching behaviour was investigated in details in solution. The results revealed that, almost all members of the dimeric materials are mesomorphic exhibit either nematic or both smectic A and nematic phases. Under UV illumination the materials show interesting photo-switching properties, reaching a photo-stationary state in 40 s and a thermal back-relaxation time of approximately 35 h in solution. Finally, a fabricated device authenticates the potential of the reported materials for optical storage devices.