Preorganised effects of a tetramesogenic supermolecule on supramolecular assembly in the liquid crystalline phases

Abstract

After preparing a homologous series of tetrameric mesogenic compounds in which two U-shaped molecules were connected via a rigid benzene derivative or a flexible alkyl chain, we investigated their phase transition behaviour using optical microscopy, differential scanning calorimetry and X-ray diffraction analysis. The compounds possessing an alkyl spacer as the central group exhibited nematic and smectic A phases just as the corresponding U-shaped molecule did. The compound possessing a 1,2-benzene unit as the connecting group showed nematic and smectic A phases, although the compound possessing a 1,3-benzene unit exhibited only an anticlinic smectic C phase. Structure–property relations of the liquid crystalline tetramers are interpreted in terms of preorganised effects of the four mesogenic units.

Keywords:

• liquid crystals
• oligomer
• nematic phase
• phase transition
• smectic phase

Acknowledgements

We thank Professors Jun Yamamoto and Yoichi Takanishi for X-ray measurements. T.N. acknowledges Hirosaki University Research Fellowship for financial support. This work was partially supported by a Grant for Hirosaki University Institutional Research.