Supramolecular Organic Ferroelectric Materials from Donor–Acceptor Systems

Abstract

Amongst different class of organic systems, donor(D)‐acceptor(A) charge‐transfer (CT)‐ complexes were recognized promising for ferroelectricity owing to their neutral‐to‐ionic phase transition at low temperature. This review presents an overview of different supramolecular D‐A systems, explored for ferroelectric (FE) phase transitions. Discussion begins with a general introduction of ferroelectricity and different associated parameters. Then it moves on to show early examples of CT‐cocrystals that showed FE properties in sub‐ambient temperature. Subsequently, recent development in the field on room temperature (rt) ferroelectricity, exhibited by H‐bond stabilized lock‐arm supramolecular‐ordering (LASO) in D‐A co‐crystals or other FE CT‐crystals devoid of neutral‐ionic phase transition are discussed. Then the discussion moves on to emerging reports on other D‐A soft‐materials such as gel and foldable polymers and finally it shows very recent development on ferroelectricity in supramolecular assemblies of single‐component dipolar or ambipolar π‐systems, exhibiting intra‐molecular charge transfer. Effect of structural nuances such as H‐bonding, balanced charge‐transfer and chirality on the observed ferroelectricity is described with available examples. Finally, piezoelectricity in recently reported ambipolar ADA‐ type systems are discussed to highlight the future potential of these soft materials in micropower energy harvesting.

Pathway-dependent supramolecular polymerization by planarity breaking

“…8,11 In this context, molecular design has become a powerful tool to tune (complex) energy landscapes in self-assembly, as evident by detailed analysis of a wide range of molecular building blocks. 12–38 While various studies have revealed that the intermolecular interactions encoded in the monomer design largely govern the self-assembly outcome, predicting these interactions by molecular design is far from easy. For example, we recently found that the functionalization of dye molecules with bulky substituents may unexpectedly stabilize H-type face-to-face stacking interactions despite the significant steric hindrance, contrary to conventional expectations based on literature.…”