An enhanced odd-even effect of liquid crystal dimers Orientational order in the α,ω-bis(4′-cyanobiphenyl-4-yl)alkanes

The odd-even behaviour observed for liquid crystal dimers has been predicted to be a sensitive function of the geometry of the link joining the mesogenic groups to the flexible spacer. Here we report the synthesis of two cyanobiphenyl dimers with methylene links, together with a determination of their transitional properties. In particular we have probed their orientational order via the major and biaxial orientational order parameters of a solute molecule, anthracene-d 10, using NMR spectroscopy. For comparison we have also determined the corresponding quantities for the cyanobiphenyl dimers with ether links. The enhanced odd-even effect observed for the methylene linked dimers relative to those with ether links is in good accord with theory.