Syntheses and characterization of novel asymmetric bent-core mesogens exhibiting polar smectic phases

Abstract

Three series of asymmetric bent-core compounds were synthesized and their mesomorphic properties were studied. All the compounds possess 2-methylresorcinol as a central unit and a stilbene bridge as a main element in the structure. Molecules of series I and series II possess only saturated terminal chains while those of series III have one or both unsaturated chain/s. The mesophases were characterized by using optical polarizing microscopy, differential scanning calorimetry, X-ray diffraction, electrooptic and dielectric measurements, and miscibility studies. All the compounds exhibit the isotropic to SmAP_R phase transition and the B_1RevTilted phase at lower temperatures. For compounds with one olefinic terminal chain, the temperature range of the SmAP_R phase was found to be narrower in comparison to compounds with both saturated terminal chains. A detailed dielectric investigation was carried out on both the SmAP_R and B_1RevTilted phases and two different types of dynamical behaviour were observed.