Mesogenic dimers composed of a calamitic and a bent-core mesogenic unit.

Tamba, Maria Gabriela; Kosata, Bedrich; Pelz, Karsten; Diele, Siegmar; Pelzl, Gerhard; Vakhovskaya, Zinaida; Kresse, Horst; Weissflog, Wolfgang · Soft Matter · 2006

basic_science · Level V

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Abstract

Three mesogenic dimers have been synthesized in which a five-ring bent-core moiety is connected with different calamitic units flexible spacers. The mesophase behavior of the dimers have been investigated by polarizing microscopy, differential scanning calorimetry, X-ray diffraction on oriented samples and by dielectric and electro-optical measurements. We found that two dimers exhibit a dimorphism columnar-nematic whereas the third one forms a columnar phase only. On the basis of the X-ray data a possible structure model of one of the columnar phases is proposed. The nematic phase exhibits unusual properties. A smectic-like texture can be induced by applying an electric field, which is unknown for nematic phases formed by rod-like mesogens.