Photo-responsive liquid crystals derived from azobenzene centered cholesterol-based tetramers

Abstract

This paper demonstrates the design and synthesis of azobenzene centred cholesterol based tetramers. A series of eight oligomeric compounds with varying flexible alkyl spacers (n = 1-8) is reported. These compounds displayed enantiotropic and monotropic chiral nematic (N∗) mesophases, which were characterized by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray scattering studies (SAXS/WAXS). We have also explored the photoisomerization behaviour of the compounds with n = 1 and n = 8. Although no photoisomerization effect was observed in the liquid crystalline (LC) state, it was, however, noticed in dilute solutions and monolayers, as depicted from UV-vis studies and Brewster angle microscopy (BAM), respectively