An unprecedented azobenzene-based organic single-component ferroelectric.

Organic single-component ferroelectrics, as an important class of metal-free ferroelectrics, are highly desirable because of their easy processing, mechanical flexibility, and biocompatibility. However, although nearly 50 years have passed since the discovery of photochromism in azobenzene-doped cholesteric liquid crystals, ferroelectricity has never been found in azobenzene-based crystals. Here, we use an amino group to substitute a fluorine atom of 2,2',4,4',6,6'-hexafluoroazobenzene, which successfully introduces ferroelectricity into 2-amino-2',4,4',6,6'-pentafluoroazobenzene (APFA).