Molecular Order versus Conformation Changes in the Liquid-Crystal Phases

Deuteron magnetic resonance splittings and their temperature dependence from deuterated liquid-crystal compounds are analyzed in terms of molecular conformation and orientational order. Three order parameters are found to be necessary to explain the smectic-C (SC) spectra whereas only two are required for the nematic (N), SA and SB phases. The data are consistent with the concept that the preferred conformation of the molecule remains unchanged at the N-SC, N-SA, and SA-SB phase transitions as well as throughout the temperature range of these phases.