We report on careful line shape studies of slow motional and orientation dependent ESR spectra of a deuterated liquid-crystal-like spin probe dissolved in a benzilidene-derivative (40,6) and in cyanobiphenyl derivative (S2 and 5CB) liquid crystals. The simulation of the ESR spectra is based on the Lanczos algorithm recently applied by Moro and Freed in a general and efficient formulation of slow motional and ordering effects on ESR line shapes. With 40,6 which exhibits monolayer smectic phases, we find that the main change in the spin relaxation upon passing from the nematic to the smectic A phase consists of changes occuring in ordering attributable to packing forces on functional groups. Such ordering effects appear to be further enhanced in the SB phase with consequent alterations in dynamics. With S2, which exhibits an interpenetrating bilayer smectic A phase, we find unusual ESR spectra in that phase which may be simulated on the basis of a model of cooperative distortions static on the ESR time scale, and superimposed on individual molecular reorientation. This mode is interpreted as a collective chain distortion which affects the orientational distribution of the piperidine ring of the spin probe. A similar phenomenon is observed in the supercooled nematic phase of 5CB, which is aligned by an electric field, and evidence is also found that the reorientational dynamics of this ring are affected by interaction with local cooperative modes in the liquid crystal (i.e., a SRLS mechanism previously proposed by Freed and co-workers). Some microscopic characteristics of liquid crystals revealed by this and previous ESR spin probe studies are discussed.

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Deuterium NMR measurements have been performed on mixtures of n-octyla-D-glucopyranoside (aOG) and n-octyl-B-D-glucopyranoside (BOG) with deuteriated water or benzene. The phase diagrams, at high crOG concentrations (lamellar phases), are similar to those reported previously for the B anomer.Deuterium NMR measurements of D,O in mixtures with aOG or BOG at lower concentrations show the existence of additional hexagonal and isotropic (including possibly cubic) phases. Some differences were noted between the phase diagrams of u and BOG at these concentrations. The sign of the diamagnetic anisotropy, Ax, of the S, lamellar phase of aOG/D,O and aOG/C,D, was found to be negative. Slow exchange between the sugar hydroxyl deuterons and water in aOG enabled us to measure their quadrupolar splittings at different temperatures. Using a simple model, where rotation of the polar head as a rigid unit around a single axis is assumed, we have calculated the direction of this axis relative to a molecular axis. The results show that this axis is approximately parallel to the C,-C, axis.

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