AN ENHANCED ODD EVEN EFFECT OF LIQUID-CRYSTAL DIMERS ORIENTATIONAL ORDER IN THE ALPHA,OMEGA-BIS(4'-CYANOBIPHENYL-4-YL)ALKANES

The odd-even behaviour observed for liquid crystal dimers has been pre dicted to be a sensitive function of the geometry of the link joining the mesogenic groups to the flexible spacer. Here we report the synthe sis 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 orientation al order parameters of a solute molecule, anthracene-d10, using NMR sp ectroscopy. For comparison we have also determined the corresponding q uantities for the cyanobiphenyl dimers with ether links. The enhanced odd-even effect observed for the methylene linked dimers relative to t hose with ether links is in good accord with theory.