Static and Dynamic Light Scattering of a Nematic Side-Group Polysiloxane

Abstract

Static and dynamic light-scattering experiments on a nematic side-group polymer are described. Using two different scattering geometries, the depolarized scattering due to thermally excited fluctuations of the nematic director was analyzed. The relaxation rates and strengths show the q dependence known from low molar mass nematics. Values for the bend and splay elastic constants and the associated effective viscosities have been obtained for a wide temperature range. The elastic constants are of the same order of magnitude as those of low molar mass nematics, whereas the presence of the polymer backbone results in drastically increased effective viscosities. In the isotropic phase near-critical order parameter fluctuations are observed; scattering intensities and relaxation rates are found to be in accordance with the Landau−de Gennes description.