Photomanipulation of the Mechanical Properties in a Liquid Crystal with Azo-Containing Bent-Core Mesogens

摘要

We demonstrate the reversible photomanipulation of the bulk mechanical properties in the azobenzene-containing bent-core liquid crystal. The azobenzene groups in the mesogens exhibit reversible cis-trans photoisomerization abilities. An unprece- dentedly large reduction by the factor of more than 5 of the splay elastic constant in a cybotactic-type nematic phase was found under exposure to the UV. This opens up the possibility to manipulate the mechanical properties of liquid crystals using light. The liquid crystal material is also distinguished by the sign inversion of low-frequency temperature-dependent dielectric anisotropy. Such behavior can be related to the presence of smectic-like nanoclusters both in the isotropic phase near the clearing point and in the cybotactic nematic phase.