Polar and chiral mesophases formed by m-terphenyl derived bent-core molecules with lateral F-substituents

Abstract

A new series of bent-core molecules based on fluorinated terphenyl cores has been synthesized. The influence of the position of the polar fluorine substituent on the mesomorphic properties was studied. The mesophases under discussion were investigated by means of polarizing microscopy, differential scanning calorimetry, X-ray diffraction as well as electrooptical experiments. Depending on the position of the fluorine substituent, polar smectic or columnar mesophases were formed. Remarkable textures could be observed for the smectic phases. For some compounds regular arrays of dots can be found which are interpreted as layer deformation on a macroscopic scale. Of special interest is the coexistence of helical filaments and a dark conglomerate texture with domains of opposite handedness found for one of the polar smectic phases. The smectic phases under investigation show antiferroelectric switching behaviour, whereas the rectangular columnar phases do not show polar switching.