Non-Newtonian Viscosity of Solutions of Ellipsoidal Particles

Abstract

The specific viscosity, and its dependence on velocity gradient, plays an important role in studies of the structure of macromolecules in dilute solution. A satisfactory theoretical interpretation of the non‐Newtonian viscosity of solutions of ellipsoidal particles has been given by Kuhn and Kuhn, and also by Saito, who made use of Peterlin's distribution function for the orientation of particle axes in the streaming liquid and calculated the energy dissipation due to both the hydrodynamic orientation and the Brownian motion. Also, a theory for the non‐Newtonian viscosity of solutions of rod‐like particles has been developed by Kirkwood. These theories involve extensive computations which have been carried out here with the aid of a computing machine by expressing Saito's results in terms of Legendre coefficients previously evaluated in the related problem of double refraction of flow. As a result, data are available for the dependence of the viscosity factor v on axial ratio and on the parameter α, where α = G/Θ, G being the velocity gradient in sec—1 and Θ being the rotary diffusion constant in sec—1. With these data it will be possible to determine the rotary diffusion constants of ellipsoidal particles from the non‐Newtonian viscosity of their solutions, and also to correct viscosity measurements to zero velocity gradient in order to obtain the intrinsic viscosity. Data are also included for the evaluation of Θ from the dependence of v at α = 0 on the frequency of periodic shear waves.