Polar switching in a crystalline modification of a five-ring bent-core compound

Abstract

A new five-ring banana-shaped compound is presented which does not exhibit a mesophase but a high-temperature crystalline phase with unexpected electro-optical properties. By application of a sufficiently high electric field (15 V µm−1) this solid modification can be clearly switched where the texture of the switched state is different for an opposite sign of the applied electric field. This switching is accompanied by a current response which indicates an antiferroelectric ground state. The switching polarisation was found to be 700 nC cm−2. It is interesting that the polar switching takes place only below a frequency of 5 Hz. The crystalline nature of the solid modification was proved by X-ray diffraction measurements on partially oriented samples. The mechanism of the polar switching is not yet clear. It can be assumed that the switchable modification has a structure with sufficient free volume which enables the collective rotation of at least parts of the molecules.