Pronounced Chirality Effect on the Ferroelectricity of Hydrogen-Bonded Supramolecular Assemblies of Ambipolar Chromophoric Systems

Chirality effects are well documented in different biological functions, but examples in soft materials physics are lesser known. This paper reports a significant chirality effect on modulating ferroelectricity in hydrogen-bonded supramolecular assemblies of two acceptor (A)–donor (D)–acceptor (A)-type conjugated molecules, namely, AD2A-C and AD2A. Both molecules contain the same naphthalimide–bithiophene–naphthalimide conjugated chromophore, symmetrically functionalized with two substituted benzamide wedges with either a chiral (AD2A-C) or achiral (AD2A) peripheral alkyl chain. They exhibit self-assembly in a hydrocarbon solvent methylcyclohexane (MCH), driven by H-bonding among the amide groups and aromatic stacking of the conjugated chromophore. Despite showing similar entangled fibrillar morphology, ultraviolet–visible (UV–vis) and Fourier transform infrared spectroscopy (FT-IR) spectra of the aggregated samples indicate a significant difference in the internal order of the self-assembled AD2A-C and AD2A. The CD spectra and microscopy images confirm helical assembly for the chiral derivative. In the mixed samples of AD2A-C + AD2A, chirality induction followed a "sergeant and soldiers" principle. The chiral AD2A-C exhibits stable ferroelectricity with a Curie temperature of 361 K and a saturation polarization of ∼2 μC cm–2, while the achiral AD2A lacks any notable ferroelectricity. The retained ferroelectricity in the mixed samples and the polarization tunability through chirality induction support their direct correlation and are key observations for predicting the future soft ferroelectric low-power electronic systems.