Ferroelectric low-voltage ON/OFF switching of chiral benzene-1,3,5-tricarboxamide derivative

The phase transition behaviour, molecular assemblies, and dielectric responses of an N,N′,N′′-trialkylbenzene-1,3,5-tricarboxamide derivative bearing chiral (S)-3,7-dimethyloctyl chains (S-3BC) were compared with those of an N,N′,N′′-trioctadecylbenzene-1,3,5-tricarboxamide derivative (3BC) bearing achiral -CONHC14H29 chains. Chiral S-3BC showed a similar phase transition behaviour to achiral 3BC, and ferroelectric polarization-electric field (P-E) hysteresis curves were observed in the discotic hexagonal columnar (Colh) liquid crystal phase. Interestingly, the magnitudes of Pr and Et values of S-3BC were 5.5-times larger and 13-times smaller than those of 3BC because of the introduction of the chiral alkyl chains, indicating a useful method to obtain low voltage ON/OFF ratios for the switching device. Much stronger N-H⋯O hydrogen-bonding interactions were observed in S-3BC than in 3BC because of much shorter π-stacking distance and blue-shift of the intermolecular asymmetrical N-H vibrational band in the former, which effectively decreased the potential energy barrier for the dipole inversion between N-H⋯O and O⋯H-N orientations and the Et value.