Organic Enantiomeric Ferroelectrics with High Piezoelectric Performance: Imidazolium l- and d‑Camphorsulfonate

Ferroelectric materials have been widely used in daily life and
industrial production, as memories, transducers, capacitors, sensors,
and so forth. Recently, great interest in molecular ferroelectrics
has emerged because of their structural flexibility, tunability, and
homochirality. Chemical design has opened up a new era for molecular
ferroelectrics, where we can realize the targeted design and performance
optimization of molecular ferroelectrics upon several well-developed
phenomenological theories. Herein, through the chemical design strategies
of lowering the molecular symmetry and introducing homochirality upon
the nonferroelectric imidazolium methanesulfonate (ImMS), we designed
a pair of high-temperature organic enantiomeric ferroelectrics, imidazolium l-camphorsulfonate (l-ImCS) and imidazolium d-camphorsulfonate (d-ImCS). The enantiomers undergo a 222F2-type
ferroelectric phase transition at 367 K (Tc(l)) and 370 K (Tc(d)), respectively. It should be highlighted that l- and d-ImCS show a relatively high piezoelectric response of 19 and
20 pC N–1, reaching the level of triglycine sulfate.
To our knowledge, this is the first time that homochiral small-molecule
ferroelectrics possess such a large piezoelectric response as well
as good biocompatibility. This finding provides a new and feasible
strategy for precisely designing high-performance homochiral molecular
ferroelectrics.