How Far Can We Push the Rigid Oligomers/Polymers toward Ferroelectric Nematic Liquid Crystals?

Abstract

The emerging ferroelectric nematic (<b>N</b>_<b>F</b>) liquid crystal is a novel 3D-ordered liquid exhibiting macroscopic electric polarization. The combination of the ultrahigh dielectric constant, strong nonlinear optical signal, and high sensitivity to the electric field makes <b>N</b>_<b>F</b> materials promising for the development of advanced liquid crystal electroopic devices. Previously, all studies focused on the rod-shaped small molecules with limited length (<i>l</i>) range and dipole moment (μ) values. Here, through the precision synthesis, we extend the aromatic rod-shaped mesogen to oligomer/polymer (repeat unit up to 12 with monodisperse molecular-weight dispersion) and increase the μ value over 30 Debye (D). The <b>N</b>_<b>F</b> phase has a widespread existence far beyond our expectation and could be observed in all the oligomer/polymer length range. Notably, the <b>N</b>_<b>F</b> phase experiences a nontrivial evolution pathway with the traditional apolar nematic phase completely suppressed, i.e., the <b>N</b>_<b>F</b> phase nucleates directly from the isotropic liquid phase. The discovery of thte ferroelectric packing of oligomer/polymer rods not only offers the concept of extending the <b>N</b>_<b>F</b> state to oligomers/polymers but also provides some previously overlooked insights in oxybenzoate-based liquid crystal polymer materials.