DEPOLARIZED LIGHT-SCATTERING STUDIES OF THE NEMATOGEN PENTYL CYANOBIPHENYL

Depolarized light scattering was used to study the nematogen pentyl cyanobiphenyl (5 CB) both in the pure state and in solution in cyclohexane. The results show three distinct concentration ranges. For dilute solutions, the molecular parameters have been determined. For intermediate concentrations, it has been possible to determine the relative contribution to the scattering of the isotropic and anisotropic components. For pure 5 CB and the concentrated solutions, an isotropic-nematic phase transition was obseved, and the pretransitional behaviour has been analysed in terms of the Landau-de Gennes model. The phenomenological constants (a, T//c and T) of the theory have been determined.