Orientational Properties of Banana-Shaped Molecules and their Sub-Units by Means of ²H NMR Spectroscopy

Abstract

Several ²H NMR studies have been performed on two deuterium labelled banana-shaped liquid crystals, the 1,3-phenylene bis{4-4′-(11-undecenyloxy) benzoyloxy} benzoate (Pbis11BB) and its 4-chloro homologue (ClPbis11BB), in the isotropic, nematic and B₂ phases.In this article, the state of the art of these studies is drawn and some new ²H NMR measurements on deuterated banana sub-units, namely the 3-(benzoyloxy)phenyl benzoate-d₁₀ (BOB-d₁₀) and its 4-chloro homologue (ClBOB-d₁₀), used as small probes dissolved in two banana-shaped liquid crystals in the nematic phase are reported.As a general result, the orientational ordering properties of these sub-units are discussed in the frame of recent results obtained on the same banana-shaped liquid crystals dissolved in calamitic nematic solvents as well as in the bulk.

Keywords:

• banana-shaped
• ²H NMR
• liquid crystals
• nematic
• orientational order
• probe
• solute

Acknowledgments

We thank the Italian MIUR for partial financial support (PRIN 2003 and PRIN 2005).