New photoswitchable mesogenic polyurethanes with gelation ability

We report a new series of thermotropic side-chain liquid crystalline polyurethanes comprising photosensitive three ring chiral mesogen and a flexible methylene spacer. All compounds, polymers, as well as monomeric precursors, display the smectic-type phases. Because of the presence of the azo group in molecular structure, the materials exhibit reversible photoisomerization process. It was also found that the polyurethanes show the gelation ability for several organic solvents, and the obtained gels are thermo- and photo-reversible.