Orientational ordering in the nematic phase of 4-alkyl-4 '-cyanobicyclohexanes

The orientational ordering of three liquid crystals (trans,trans-4-n-alkyl- 4'-cyanobicyclohexanes) has been investigated using C-13 NMR. 2D proton-enc oded local field spectroscopy was used to determine the C-13-H-1 dipolar co upling constants, from which the order parameters were calculated. Semi-emp irical linear relations between the obtained order parameters and anisotrop ic C-13 chemical shifts were established. It was found that the order param eters of the major axis of the cyclohexane rings are smaller than those of liquid crystals with phenyl rings. and the order parameters of the C-H bond s in the aliphatic chains also behave differently.