Polar Switching of Dipolar Molecules Induced by Solid Dispersion-to-organogel Phase Transition

A lipophilic l-glutamate-derived gelator having multiple amide linkages is dissolved in liquid 1-methoxy-4-nitrobenzene (MNB) by heating. Upon cooling this solution below ca. 337 K, a sol-to-gel transition occurs and the liquid MNB molecules are confined in the self-assembled gel networks. This organogel shows significant enhancement of dipolar polarization and hysteresis is observed in the polarization (P)-electric field (E) curves. The cooling of the gel to ambient temperature affords a solid dispersion phase, which does not show such enhanced dipolar polarization nor the P-E hysteresis. The electric field-induced macroscopic polarization of MNB molecules thus occurs only when they are in the liquid phase and confined in the interstitial domains of the MNB gel.