Physical properties of rod-shaped molecules in solution

Several theories describing the physical properties of solutions containing rod-shaped molecules are reviewed. The results of the various theories are presented in a convenient form for implementation on a calculator or microcomputer. Expressions are derived for light scattering from thin rods using rational approximations for the sine and cosine integrals. These expressions apply to turbidity, Rayleigh, and dynamic light-scattering measurements. Accurate approximating equations are given for the various diffusional motions involved in dynamic light scattering. For shear-dependent viscosity and flow birefringence, empirically derived interpolation formulas are given. These provide values of the Simha factor, extinction angle and orientation function for a wide range of axial ratios and velocity gradients with relative errors less than 1%. We demonstrate how these equations can be applied to predict or model the properties of a solution containing thin rods of various lengths.