Orientational order in the nematic phase of the α,ω-bis(4,4′-cyanobiphenyloxy) alkanes

The deuterium N.M.R. spectra of three members from the series of α,ω-bis(4,4′-cyanobiphenyloxy) alkanes, deuteriated in both chain and ring, have been recorded in their nematic liquid-crystalline phases. The quadrupolar splittings, , and dipolar couplings , obtained from these spectra show that the alkyl chain must adopt more than one conformation. The segmental orientational order parameters derived from both and are compared with the predictions of a theory for the orientational order of flexible mesogens. The agreement between the observed and calculated order parameters is good but not perfect, and reasons for this discrepancy are discussed.