Theory of molecular reorientation rates, flow birefringence, and depolarized light scattering

Abstract

Flow-induced molecular orientation, the magnitude of which determines the importance of the flow-birefringence effect, is calculated using extended hydrodynamic equations. A similar procedure leads to the orientational fluctuations which give rise to depolarized light scattering. By combining HH depolarized light-scattering data, both integrated intensity and spectral linewidths, with the flow-birefringence data, one can determine a parameter R which measures the coupling of molecular orientation to collective shear modes and is of importance in studies of anisotropic intermolecular interactions. The same parameter can be evaluated from an analysis of the VH depolarized light-scattering spectrum. Experimental data confirm the theory.