A Hierarchical (Macro)molecular Assembly Assisted by Donor–Acceptor Charge‐Transfer Interactions Exhibiting Room‐Temperature Ferroelectricity

Abstract

This communication reveals co-assembly of an electron-deficient naphthalene-diimide (NDI)-appended polyurethane (P1) and electron-rich pyrene (Py), forming an organogel with prominent room-temperature ferroelectricity. In a non-polar medium, intra-chain hydrogen-bonding among the urethane groups of P1 produces a folded structure with an array of the NDIs in the periphery, which intercalate Py by charge-transfer (CT)-interaction. Such CT-complexation enables slow crystallization of the peripheral hydrocarbons, causing gelation with nanotubular morphology, in which the wall consists of the alternating NDI-Py stack. Such D-A assembly exhibits ferroelectricity (saturation polarization P_s ≈0.8 μC cm^-2 and coercive field E_c ≈8 kV cm^-1 at 500 V and 10 Hz frequency) with Curie temperature (T_c ) of ≈350 K, which can be related to the disassembly of the CT-complex. In the absence of Py, P1 forms spherical aggregates, showing dielectric behaviour.