Supramolecular ferroelectric nematic materials

Abstract

The discovery of a new nematic phase variant with polar order and ferroelectricity, the NF phase, is a significant milestone in soft matter research. Herein we describe the preparation of hydrogen-bonded complexes between 4-(2,4-dimethoxybenzoyloxy)benzoic acid and either 4-nitropyridine or 3-fluoro-4-nitropyridine, these being analogous in structure to the archetypal NF material RM734. Complexes were isolated using a semi-automated process we term Machine Vision Aided Crystallisation. We find these complexes exhibit classical and polar (NF) nematic phases despite the large reduction in electric dipole moment that results from swapping a phenyl ring for 4-pyridyl. DFT calculations support the hypothesis that the onset of polar order is not simply a product of electric dipole magnitude, but rather results from more subtle interactions between regions of opposing electrostatic potential.