Dynamic Properties near the Nematic-Isotropic Transition of a Liquid Crystal

We have measured the temperature dependence of the flow birefringence in the isotropic phase of $p$-methoxybenzylidene $p-n$-butylaniline. We have observed a divergence as the phase transition is approached. We have determined the steady shear viscosity ${\eta }_0$ and the coupling coefficient $\mu$ between velocity shear and the order parameter as a function of temperature. We have also measured the real part of the shear impedance and compared the results with light-scattering data. Our results are well described by de Gennes's theory.