Design and synthesis of photosensitive bent-core liquid crystals exhibiting polar smectic phases

Abstract

Bent-core liquid crystals represent a fascinating class of self-assembling materials. This is due their unique organized fluidic states – mesophases – that are widely studied for their electrooptical and optical responses. We designed and synthesized two series of mesogens based on laterally substituted 3-hydroxybenzoic acidand tuned their properties by changing the linkinggroup in both side-arms. Using polarizing optical microscopy, differential scanning calorimetry and x-ray diffraction, we have established the mesomorphic properties and found several types of smectic mesophases.For homologues comprising the photosensitive azo group, we have studied their switching ability in a solution as well as in mesophases employing external UV light irradiation. We have confirmed the ability of the materials to completely undergo the light-induced switching from a mesophase to isotropic liquid by on-lineillumination of an x-ray sample.Unlike previously studied compounds of related structure, the studied compounds exhibited thermally unstable nematic phases and stable enantiotropic antiferroelectric polar smectic C phases. A transition from a an apolar SmC to SmCAPA phase is also documented.