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 SmAPR phase transition and the B1RevTilted phase at lower temperatures. For compounds with one olefinic terminal chain, the temperature range of the SmAPR 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 SmAPR and B 1RevTilted phases and two different types of dynamical behaviour were observed. © 2009 The Royal Society of Chemistry.