Single-component organic molecular ferroelectrics based on disk- or wheel-like rotation?

Journal of Materials Chemistry C Pub Date: 2021-09-21 DOI: 10.1039/D1TC03117A

Abstract

Large polarizations and their reversible switching, which are indispensable for many functional ferroelectric applications, are achieved in new single-component organic molecular ferroelectrics with rotating strongly dipolar molecules or substituents. In a pre-screening process using a crystal structural database, both local-molecular and whole-crystal symmetries are inspected for the existence of pseudosymmetry required for rotational ferroelectricity, revealing several candidates: disk-type rotation in 1,2,3,4,5-pentamethyl-6-nitrobenzene (PMNB) molecules and wheel (or rotary knob)-type rotations of the substituents of 2-(methylsulfonyl)malonamide (MSMA), tris(4-acetylphenyl)amine (TAPA), and 4-methylsulfonyl-2-nitrotoluene (MSNT) crystals. The theoretically computed polarizations successfully reproduce experimental values, demonstrating that the rotational processes reverse most of the observed macroscopic polarizations. The theoretically large polarizations (7–8 μC cm?2) being comparable to those of polymer ferroelectrics are attributed to the strongly electron-withdrawing nitro group in PMNB as well as the methylsulfonyl group of MSMA and MSNT being highly polarized in the radial direction.

Graphical abstract: Single-component organic molecular ferroelectrics based on disk- or wheel-like rotation
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