Novel bent-shaped liquid crystalline compounds: IV. Dimesogenic compounds containing 2-hydroxy-1,3-dioxypropylene and azobenzene mesogens

Three bent-shaped dimesogenic liquid crystalline compounds having odd-numbered terminal alkyloxy chains (n = 5, 7, 9) with a 2-hydroxy-1,3-dioxypropylene as central linking unit and two identical azobenzene mesogens were synthesized. Their mesomorphic properties were then characterized by polarized light microscopy and differential scanning calorimeter. The terminal alkoxy chain length was the key factor to provide the liquid crystallinity in this series. The compound of n = 7 showed a monotropic SmC phase, and that of n = 9 displayed an enantiotropic SmC phase. The compound of n = 5, however, did not show liquid crystal phase. The thermal stability of the smectic phases also increased with the terminal alkoxy length.