Dielectric relaxation in nematics and Doolittle's law

Doolittle's law relates a kinetic property such as viscosity or dielectric relaxation to the free volume. In nematogens the volume expansion is discontinuous at the nematic-isotropic transition temperature $T_c$ and nonlinear at $(T_c-20\mathrm{} \mathrm{K})\lesssim T<~T_c$. This makes a test of Doolittle's law possible.