Dynamic change of molecular conformation generating a variation of liquid crystalline phases for triphenylene mesogens with peripheral alkoxyazobenzenes

A triphenylene mesogen which possesses six dodecyloxyazobenzene units at the periphery linked by propylene-ether chain (2-C12-3) was synthesised and its mesomorphic phase transition behaviour was investigated. It was found that 2-C12-3 exhibits six mesophases including one monotropic phase. The calamitic-discotic bi-mesomorphic phase transition was also observed. As cooling the compound at the temperature of iso phase, SmA phase comes up and further cooling gives Colob phase. In comparison to the corresponding ester-linked derivative (1-C12-3), which shows only two mesophases (SmA and Colr), the linkage part connecting triphenylene unit and the peripheral alkoxyazobenzenes significantly affect the molecular ordering in mesophase, though the bi-mesomorphic property is maintained in the case of dedecyloxy chains.