Dielectric relaxation qualitative features

The behavior of the dielectric spectra for the two-rotational-degree-of-ffeedom (needle) model is similar but not identical to that for fixed-axis rotators (one-rotational-degree-of-fireedom model). Here, the two- and one-rotational-degree-of-freedom models (fractional or normal) can predict dielectric parameters, which may considerably differ from each other. The differences in the results predicted by these two models are summarized in Table I. It is apparent that the model of rotational Brownian motion of a fixed-axis rotator treated in Section IV.B only qualitatively reproduces the principal features (return to optical transparency, etc.) of dielectric relaxation of dipolar molecules in space for example, the dielectric relaxation time obtained in the context of these models differs by a factor 2. 

To explain these results, Moscicki proposed a qualitative model of the dielectric relaxation in lyotropic LCPs. A main feature of the model was the assumption that each rod can only undergo spatially restricted rotations (hopping between cages) around the nematic director. To rationalize this situation, the theory of small-step rotational diffusion in a was applied, i.e. it was assumed that the free space available... 

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