Polarization Switching Induced by Slowing the Dynamic Swinglike Motion in a Flexible Organic Dielectric

Molecular motions with large amplitude in close-packed crystals accompany large distortions of the molecular configuration, which generally generate orientational structural transitions between diverse states and enable the tuning of their bulk physical properties. We present a flexible organic dielectric, di-<i>n</i>-butylammonium chlorodifluoroacetate (<b>1</b>), which exhibits a reversible temperature-induced spontaneous polarization switching at 243 K (<i>T</i>_c). Ferroelectric hysteresis loop measurements and second harmonic generation experiments reveal its excellent polarization switching capacity with spontaneous polarization of 3.9 μC cm^–2. Temperature-dependent solid-state nuclear magnetic resonance measurements clearly elucidate the dynamical mechanism of polarization switching of <b>1</b>. Above <i>T</i>_c, an active swinglike motion in long-chain di-<i>n</i>-butylammonium (DBA) cation is confirmed, resulting in complete obliteration of the dipole moments. When the temperature decreases below <i>T</i>_c, the swinglike motions are frozen and the whole DBA cation becomes considerably more rigid, corresponding to polar order, which greatly contributes to polarization switching. It is believed that this finding opens up a potential strategy for the design of new polar materials as switchable electric devices