Synthesis and properties of Photo-responsive liquid crystalline polyacetylene derivatives

New crystalline conjugated polymer, poly(mono-substituted acetylene) was synthesized by introducing an azobenzene moiety as a mesogen core into side chain. Polymerization of the liquid crystal-substituted acetylene monomer was carried out using a Rh-based or Fe-based catalyst. Polarizing microscope studies demonstrated that the monomer exhibits a“droplets” texture characteristic of a nematic phase, and the polymer a polygonal texture assignable to a smectic phase. Photo-induced reversible cis-trans isomerization of the azobenzene moiety as well as thermal irreversible isomerization from cis totrans form of the polymer backbone were elucidated.