Unusual mesomorphic behaviour of new bent‐core mesogens derived from 4‐cyanoresorcinol

Abstract

New five‐ring bent‐core mesogens derived from 4‐cyanoresorcinol as the central core have been synthesized. The mesophases were assigned by polarizing microscopy, X‐ray diffraction and electro‐optical measurements. It was found that the mesophase behaviour clearly depends on the direction of the carboxyl linking groups between the aromatic rings. If the outer and inner ester linking groups of a wing are in the same direction then nematic phases and, for long chain members, SmC and SmCP_A phases are observed. If the outer and inner linking groups are in opposing directions a dimorphism, SmA–SmAP_A, is observed and the clearing temperatures are increased by about 55 K. It is remarkable that in the SmCP_A phases of the first series, polar switching preferably takes place through a collective rotation of the molecules around their long axes which is accompanied by the inversion of the chirality of the smectic layers.

Acknowledgement

This work was supported by the Deutsche Forschungsgemeinschaft (DFG, Graduiertenkolleg 894).