Self-assembled gels of liquid crystals: hydrogen-bonded aggregates formed in various liquid crystalline textures

Abstract

An azobenzene-containing gelator can gel the nematic liquid crystal BL006 through self-assembly of hydrogen-bonded aggregates. Due to the high nematic–isotropic transition temperature of BL006, the gelation occurs either in the isotropic or the nematic phase depending on the concentration of the gelator. Prior to the aggregation in the nematic phase upon cooling, the gelator can act as a chiral dopant and induce a chiral nematic phase for BL006 over a range of temperatures. This finding has been used to investigate the influence of the liquid crystal environment on the aggregation of the gelator. Making use of rubbed surfaces, electric field and different concentrations of the gelator, various liquid crystalline orientation states, referred to as planar, fingerprint, homeotropic and homogeneous textures, were obtained, and the aggregation of the gelator was allowed to proceed in these environments. It was found that a variety of fibrous and elongated aggregates, differing in morphology and alignment, could be formed, and that the self-assembled liquid crystalline gels with different aggregates could exhibit different electrooptic effects.