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

Abstract

The dynamical behavior of a small probe molecule CH3CN dissolved in a nematic liquid crystal is studied by NMR relaxation measurements on 1H, 13C, and 14N 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 13C 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.