Change in the polarizability of MBBA molecules upon the nematic-isotropic liquid transition and physical consequences

The Lorentz tensor components $L_j$ and the polarizability tensor components $\gamma_j$ of 4-methoxyben-zylidene-4'-butylaniline (MBBA) liquid crystal molecules in nematic and isotropic phases have been determined experimentally. The quadratic dependences of the mean value $\bar{\gamma}(S)$ and anisotropy $\Delta\gamma(S)$ of the polarizability in the nematic phase on the orientational order parameter $S$ of molecules have been established. Within the phenomenological approach, the dependences $\bar{\gamma}(S)$ and $\Delta\gamma(S)$ have been derived, and their features for MBBA and other known objects have been interpreted. The relation of the dependences $\bar{\gamma}(S)$ and $\Delta\gamma(S)$ to the features of the nematic-isotropic liquid phase transition has been found.