Unusual electro-optical response of an oblique columnar phase formed by a bent-core mesogen

• Published in: Liquid crystals 2008-03, Vol.35 (3), p.325-331
• Main Authors: Schröder, Martin W., Brand, Kristin, PelzL, Gerhard, Baumeister, Ute, Diele, Siegmar, Weissflog, Wolfgang
• Format: Article
• Language: English
• Subjects: bent-core mesogens; columnar phase; electro-optical behaviour; polar switching; X-ray
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/02678290701871869

Mesophases formed by bent-core mesogens have attracted special attention because they can organise into fluid phases with polar order and supramolecular chirality. In this paper, a new five-ring bent-core mesogen is presented which forms a columnar mesophase. The structure is built up by layer fragments and possesses an oblique two-dimensional lattice with a layer group of the type p112/a. The columnar phase can be transformed into a ferroelectric SmCP phase (SmCP F ) by application of a sufficiently high electric field (25 V µm −1 ). This field-induced transition was found to be reversible. The mechanism of the polar switching depends on the frequency of the applied electric field. The switching takes place in the usual way by a collective rotation of the molecules around the tilt cone. At very low frequencies (0.1 Hz and lower), the polar switching is based on a collective rotation of the molecules around their long axes. In the latter case, the switching is accompanied by an inversion of the layer chirality.