Frictional properties of dilute polymer solutions. I. Rotational friction coefficient

The theory of Debye and Bueche for the frictional properties of dilute polymer solutions is placed on a microscopic basis. It is shown that the microscopic foundations for the theories of Debye−Bueche and Kirkwood−Riseman are identical, but that the theories differ in their statistical analysis. The Debye−Bueche equations are applied to the rotational friction coefficient of a spherically symmetric polymer with arbitrary radial density distribution. An exact result is derived for a Gaussian distribution of low density. A variational principle of minimum energy dissipation is formulated which is suitable for numerical work.