Columnar mesomorphism of bent-rod mesogens containing 1,2,4-oxadiazole rings

In this study, the synthesis, characterization, and mesomorphic properties of ten new bent-rod compounds containing two units of 1,2,4-oxadiazoles are reported. In order to understand the relationship between the structure and the mesomorphic behavior, molecules containing a variety of polar substituents (i.e., I, NO2, NH2, OH) on the central rigid core were prepared. The hexagonal columnar mesomorphism was characterized by DSC and POM and the nature of the mesophases was established through XRD studies. The driving force for self-assembly can be explained by microsegregation between the aliphatic parts and the polar parts, producing a dimer, trimer, and tetramer inside a single disc.