Dipolar relaxation in thin films of supramolecular stacks of benzenecarboxamides and insights to enhance their ferroelectric characteristics

Abstract

The relationship between molecular structure and ferroelectric behaviour of thin films is explored in an all-organic supramolecular polymer material based on benzenecarboxamides, using atomistic molecular dynamics simulations. While increasing the number of amide groups around the phenyl core increases the dipole density of a molecule, increasing the length of the corresponding alkyl groups decreases the same. The interplay between these two contributions displays a rich behaviour on key material characteristics, in particular, the polarisation retention time. The latter is shown to be inversely proportional to the alkyl chain length, a consequence of weaker interactions between macrodipoles of stacks. Polarisation retention time was observed to be the highest in a molecule with five amide groups around the aromatic phenyl core which is explained as due to the large barrier for amide group rotation, which is one of the crucial channels for dipolar relaxation. Simulations also demonstrate that the barrier, however, does not affect the switchability of polarization, upon field reversal.