The dynamical behavior of a small probe molecule dissolved in a nematic liquid crystal studied by NMR

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Abstract
The dynamical behavior of a small probe molecule CH3CN dissolved in a nematic liquid crystal is studied by NMR relaxation measurements on 1H, 1 3C, and 1 4N nuclei measured at six different field strengths. The results show a strong frequency dependent relaxation behavior that can be described by order director fluctuations in the nematic solvent. A major contribution from slowly relaxing local structures, as introduced by Polnaszek and Freed, is unlikely. Values for the rotational anisotropy, random local field contributions to the relaxation of the 1 3C and 1H nuclei, and order director fluctuation parameters are given. A comparison has been made with other studies of analogous systems and the necessity is demonstrated of extended frequency dependent measurements for a complete description of the dynamical processes involved.